SBE LS3 two thoughts
10-04-2021, 09:53 PM
#21
TECH Enthusiast
Well, I really like the car and like what you are doing with it. Let me change my "slap it together" combo some. Given the use and the parameters. I'd slap a Fast intake on it for sure, and put an LLSR in it. To stay hyd for this, I think, is a waste. The maintenance on a LLSR really is not bad at all. Even easier on valvetrain, to a certain degree. You can meet your dirveability and rpm requirements way easier w/ less trade-offs. Give it some thought.
10-04-2021, 10:24 PM
#22
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Schmedium LLSR "something like" ~233*/241* 114*+2* .650"/.630" Mid-Length Runner Fast (for hood clearance).
500+ @ wheels pretty easy ~ 7000 carry 7400+, still drive very nice.
Just my .02
500+ @ wheels pretty easy ~ 7000 carry 7400+, still drive very nice.
Just my .02
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DualQuadDave (10-05-2021)
10-04-2021, 10:53 PM
#23
Thanks guys yeah it is a cool car for sure, and I miss having it on the road. That's part of the struggle - now that you know the application some different ideas start to pop up that might suit the car better. I'm trying not to go past 6-8* overlap as from past experience that is a good amount without getting too wild.
I have a wild ls7 in progress that life has not afforded me the time or energy to finish yet, so I'm looking just to get it back on the road with something easy that is still fun. The ls7 will be the big solid roller engine with ~33* overlap and turn 8k rpm. All the parts I've mentioned except the long block and the cam are owned and going on the car, including the Johnson lifters if I choose to use them. I just need a healthy engine to drop in.
Hood clearance is a big challenge. The ls7 I'll use a Holley low pro sniper and still probably will need to get creative to make it fit near the TB. Fast 102 takes cutting the stock hood webbing out and bashing the firewall to fit. The rod mod ls3 is free-95 and fits without issue.
I do like the idea of a mild solid roller with shimmed valve lash instead of adjusters, but it is more parts to buy that I don't own. Trying not to overspend. The crate motor + cam only is a stretch right now, but the cylinder head mods are essentially free.
One thing I've confused myself on while reading today is how much PTV clearance there is on the exhaust side? Everyone focuses on cutting pockets for the intake valve, but I think the exhaust will still get tight if I clip the heads way down. I don't have a fly cutter for the exhaust side so that would probably be a non-starter. If I take .060-.070" off the heads and run a .040 gasket is the exhaust valve too close?
As we joke about rain in Seattle, and driving on slicks in CA, there is a big lightning storm on top of my head right now haha. Check out Maxxis tires though - the RC1 is the super miata race spec tire and it is amazing on the street. Quiet and smooth without the aggressive tread blocks of a normal DOT-R.
I have a wild ls7 in progress that life has not afforded me the time or energy to finish yet, so I'm looking just to get it back on the road with something easy that is still fun. The ls7 will be the big solid roller engine with ~33* overlap and turn 8k rpm. All the parts I've mentioned except the long block and the cam are owned and going on the car, including the Johnson lifters if I choose to use them. I just need a healthy engine to drop in.
Hood clearance is a big challenge. The ls7 I'll use a Holley low pro sniper and still probably will need to get creative to make it fit near the TB. Fast 102 takes cutting the stock hood webbing out and bashing the firewall to fit. The rod mod ls3 is free-95 and fits without issue.
I do like the idea of a mild solid roller with shimmed valve lash instead of adjusters, but it is more parts to buy that I don't own. Trying not to overspend. The crate motor + cam only is a stretch right now, but the cylinder head mods are essentially free.
One thing I've confused myself on while reading today is how much PTV clearance there is on the exhaust side? Everyone focuses on cutting pockets for the intake valve, but I think the exhaust will still get tight if I clip the heads way down. I don't have a fly cutter for the exhaust side so that would probably be a non-starter. If I take .060-.070" off the heads and run a .040 gasket is the exhaust valve too close?
As we joke about rain in Seattle, and driving on slicks in CA, there is a big lightning storm on top of my head right now haha. Check out Maxxis tires though - the RC1 is the super miata race spec tire and it is amazing on the street. Quiet and smooth without the aggressive tread blocks of a normal DOT-R.
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DualQuadDave (10-05-2021)
10-05-2021, 12:36 AM
#24
One guy come to mind on a Stock engine and PTV Clearances:
Suicidal Racing.
Suicidal Racing.
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DualQuadDave (10-05-2021)
10-05-2021, 04:54 AM
#25
Where’s Darth? He always has solid input.
10-05-2021, 07:00 AM
#26
Thanks guys yeah it is a cool car for sure, and I miss having it on the road. That's part of the struggle - now that you know the application some different ideas start to pop up that might suit the car better. I'm trying not to go past 6-8* overlap as from past experience that is a good amount without getting too wild.
I have a wild ls7 in progress that life has not afforded me the time or energy to finish yet, so I'm looking just to get it back on the road with something easy that is still fun. The ls7 will be the big solid roller engine with ~33* overlap and turn 8k rpm. All the parts I've mentioned except the long block and the cam are owned and going on the car, including the Johnson lifters if I choose to use them. I just need a healthy engine to drop in.
Hood clearance is a big challenge. The ls7 I'll use a Holley low pro sniper and still probably will need to get creative to make it fit near the TB. Fast 102 takes cutting the stock hood webbing out and bashing the firewall to fit. The rod mod ls3 is free-95 and fits without issue.
I do like the idea of a mild solid roller with shimmed valve lash instead of adjusters, but it is more parts to buy that I don't own. Trying not to overspend. The crate motor + cam only is a stretch right now, but the cylinder head mods are essentially free.
One thing I've confused myself on while reading today is how much PTV clearance there is on the exhaust side? Everyone focuses on cutting pockets for the intake valve, but I think the exhaust will still get tight if I clip the heads way down. I don't have a fly cutter for the exhaust side so that would probably be a non-starter. If I take .060-.070" off the heads and run a .040 gasket is the exhaust valve too close?
As we joke about rain in Seattle, and driving on slicks in CA, there is a big lightning storm on top of my head right now haha. Check out Maxxis tires though - the RC1 is the super miata race spec tire and it is amazing on the street. Quiet and smooth without the aggressive tread blocks of a normal DOT-R.
I have a wild ls7 in progress that life has not afforded me the time or energy to finish yet, so I'm looking just to get it back on the road with something easy that is still fun. The ls7 will be the big solid roller engine with ~33* overlap and turn 8k rpm. All the parts I've mentioned except the long block and the cam are owned and going on the car, including the Johnson lifters if I choose to use them. I just need a healthy engine to drop in.
Hood clearance is a big challenge. The ls7 I'll use a Holley low pro sniper and still probably will need to get creative to make it fit near the TB. Fast 102 takes cutting the stock hood webbing out and bashing the firewall to fit. The rod mod ls3 is free-95 and fits without issue.
I do like the idea of a mild solid roller with shimmed valve lash instead of adjusters, but it is more parts to buy that I don't own. Trying not to overspend. The crate motor + cam only is a stretch right now, but the cylinder head mods are essentially free.
One thing I've confused myself on while reading today is how much PTV clearance there is on the exhaust side? Everyone focuses on cutting pockets for the intake valve, but I think the exhaust will still get tight if I clip the heads way down. I don't have a fly cutter for the exhaust side so that would probably be a non-starter. If I take .060-.070" off the heads and run a .040 gasket is the exhaust valve too close?
As we joke about rain in Seattle, and driving on slicks in CA, there is a big lightning storm on top of my head right now haha. Check out Maxxis tires though - the RC1 is the super miata race spec tire and it is amazing on the street. Quiet and smooth without the aggressive tread blocks of a normal DOT-R.
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Corona (10-06-2021)
10-05-2021, 07:26 AM
#27
10 Second Club
I have achieved 460+ rwhp with stock intake and cam in 2 different LS3s both motors squared up nicely with torque as well. Going in a light RX7 I would throw a good set of valve springs on it and enjoy it forever. You should be able to make 420ish with your exhaust limitations pretty easy. 90mm tb is plenty too. I have not found a significant gain switching to a 102.
Last edited by lazerlemonta; 10-06-2021 at 07:48 AM.
10-07-2021, 01:40 PM
#28
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One thing I've confused myself on while reading today is how much PTV clearance there is on the exhaust side? Everyone focuses on cutting pockets for the intake valve, but I think the exhaust will still get tight if I clip the heads way down. I don't have a fly cutter for the exhaust side so that would probably be a non-starter. If I take .060-.070" off the heads and run a .040 gasket is the exhaust valve too close?
Onto the test results. When we tested on a stock LS3, the valve drop on that head was .128" on the 2.165" intake valve. Our SUM-8710R1 Stage 3 LS3 cam had .081"/.103" PTV clearance. The stage 4 LS3 cam SUM-8711R1 had .076"/.096". For fun we tested the standard stage 4 SUM-8709R1. It had .061"/.092". That’s pretty much right at the limit we would normally recommend for PTV clearance. We recommend a minimum of .060"/.090" for PTV clearance.
We'll throw our hat in the ring for a suggested route to go with this combo. A corner-carving-minded LS3 swapped FD RX-7 sounds like a lot of fun!
We'd go with something more like option 2. For the cam, we'd go with our stage 3 extra clearance "rectangle port" SUM-8710R1. Specs on it are .625"/.605", 230/242, 113+3 with 10* of overlap. Don't let the 10* of overlap scare you. For idle quality and driveability, we focus more on the intake valve opening point than overlap. With a 5* IVO it won't be a bear to tune or live with. With our stable lobes and the 45* IVC, it will carry out well past 7,000 paired with some .660" lift TFS-2500286P dual springs.
As far as the heads we'd recommend milling them .020". At .020" off with the 8710R1, you shouldn't have to worry about any flycutting. Although, for best engine building practices we always recommend checking PTV before final assembly. Also, on the topic of head milling. We typically find about .030" milled is the limit before you have to start massaging on the intake to get it aligned.
We think with cutting .020" off the heads and swapping in our 8710R1 this combo would be an absolute joy!
10-07-2021, 02:05 PM
#29
I second (or third) raising compression, makes the car better all around!
I agree the carb intakes love to rev and throttle response is great, but a 5-7lb weight difference between intakes isn't going to make a meaningful difference. My car is in the 2400lb range with a carb intake and 4 barrel throttle body which is less than 1% of its weight.
If the OP really wants it to pull higher in the rev range, I wonder if an MSD intake or even a short runner "carburetor" intake with a throttle body injector setup would be the ticket. I won't do that on my Miata, because it wouldn't fit under the stock hood. and I don't want the extra weight of the metal intake on the nose of my sports car ... but maybe the FD has more clearance. The FD is light enough that it really could trade some midrange torque for an extended rev range and more power up top. I might do that in the Miata if a higher revving intake setup would clear my hood.
10-07-2021, 07:11 PM
#30
I'd love to run a victor jr or super vic but the air cleaner would be half way up my windshield. It just isn't practical. Believe me I've daydreamed endless intake combinations for this car and then go pop the hood and the wind just falls out of my sails lol. I will be trying one of the sheet metal tunnel ram intakes soon and I think it will be a good match with a very flat torque curve that hangs on as long as I want to rev it. Performance wise the low profile sheet metal intakes seem to match approximately to a victor jr. Can't quite get to the realm of a hi-ram or super vic or CID - but for the packaging it isn't bad.
Thank you so much! Your stage 3 does seem like a good fit. The experiment I think I'd be interested in trying for my rx7 is to move the IVC and EVO point to something more in line with your stage 4 cams, but drop the overlap to the ~6-8* range. I think top end power would stay very similar, should extend the RPM range, and I would not miss any midrange losses in such a light car with 3.90 gears and 25" tall tires. Something like IVC 50, EVO 65, IVO 4, EVC 3. Definitely an oddball for a SBE ls3 that is typically in a much larger car with longer gearing. This is also why I was considering bumping the compression as much as possible to help recover some cylinder pressure for low rpm and part throttle.
It seems like from your valve drop numbers I would not be able to cut 60-70 off the heads and have any chance of the exhaust valve fitting. I don't want to buy an exhaust cutter, and you're right that intake fitment can get tricky. Cutting 20 and doing a shelf stage 3 is appealing.
What is your recommendation @Summitracing for street friendly 4.065 x 4.00" pistons and rings that would not require any machining to the ls3 block? I suspect my callies crank and rods are healthy that I can salvage from my 402 and I'd be a lot happier building out a 415. My 402 before I killed it pulled to 7400 and ran like hell in that car.
Are your summit branded pistons a good choice? What is your targeted deck height? A lot of aftermarket pistons I've seen drop the pistons .005-.010 in the hole. I'd hope to see .005-.010 out of the hole or I'd be hard pressed not to deck the block to set the quench.
We love the Mahle powerpak pistons but they're backordered for ages. The powerpak pistons did require decking the block to get the pistons out of the hole. I suppose I could custom order a cometic gasket, but last I checked they're also very backordered - maybe that has improved.
We wanted to jump in and add some helpful info from a test we did. We've taken a stock LS3 and swapped in both of our extra clearance "rectangle port cams". Folks focus on the intake so much because of that big ol' 2.165" valve. With the smaller 1.590" exhaust valve you're effectively further away from the piston. That's why you don't hear the exhaust side discussed as much. This doesn't mean it couldn't become an issue, it's just not as common as the intake side that you hear about more.
*snip*
We think with cutting .020" off the heads and swapping in our 8710R1 this combo would be an absolute joy!
*snip*
We think with cutting .020" off the heads and swapping in our 8710R1 this combo would be an absolute joy!
Thank you so much! Your stage 3 does seem like a good fit. The experiment I think I'd be interested in trying for my rx7 is to move the IVC and EVO point to something more in line with your stage 4 cams, but drop the overlap to the ~6-8* range. I think top end power would stay very similar, should extend the RPM range, and I would not miss any midrange losses in such a light car with 3.90 gears and 25" tall tires. Something like IVC 50, EVO 65, IVO 4, EVC 3. Definitely an oddball for a SBE ls3 that is typically in a much larger car with longer gearing. This is also why I was considering bumping the compression as much as possible to help recover some cylinder pressure for low rpm and part throttle.
It seems like from your valve drop numbers I would not be able to cut 60-70 off the heads and have any chance of the exhaust valve fitting. I don't want to buy an exhaust cutter, and you're right that intake fitment can get tricky. Cutting 20 and doing a shelf stage 3 is appealing.
What is your recommendation @Summitracing for street friendly 4.065 x 4.00" pistons and rings that would not require any machining to the ls3 block? I suspect my callies crank and rods are healthy that I can salvage from my 402 and I'd be a lot happier building out a 415. My 402 before I killed it pulled to 7400 and ran like hell in that car.
Are your summit branded pistons a good choice? What is your targeted deck height? A lot of aftermarket pistons I've seen drop the pistons .005-.010 in the hole. I'd hope to see .005-.010 out of the hole or I'd be hard pressed not to deck the block to set the quench.
We love the Mahle powerpak pistons but they're backordered for ages. The powerpak pistons did require decking the block to get the pistons out of the hole. I suppose I could custom order a cometic gasket, but last I checked they're also very backordered - maybe that has improved.
Last edited by spanks13; 10-07-2021 at 07:17 PM.
10-08-2021, 01:21 PM
#31
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@spanks13,
We figured it would be best just to grab your post and provide answers in blue.
Thank you so much! Your stage 3 does seem like a good fit. The experiment I think I'd be interested in trying for my rx7 is to move the IVC and EVO point to something more in line with your stage 4 cams, but drop the overlap to the ~6-8* range. I think top end power would stay very similar, should extend the RPM range, and I would not miss any midrange losses in such a light car with 3.90 gears and 25" tall tires. Something like IVC 50, EVO 65, IVO 4, EVC 3. Definitely an oddball for a SBE ls3 that is typically in a much larger car with longer gearing. This is also why I was considering bumping the compression as much as possible to help recover some cylinder pressure for low rpm and part throttle.
No problem. We do really like the stage 3 for what you're looking to do here. We understand wanting to try something a little different. Your idea and valve events aren't as far out there as you might think. It's completely understandable wanting to shift the powerband up in a light car so at the tap of the throttle we're not scorching the tires off. At the same time let's boost compression to help with power across the range and throttle response.
We did some digging for shelf cams that fit the bill for what you're hunting for. Take a look at this Cam Motion CXM-03-01-0049. Specs on it are .621"/.604", 232/248, 116+5 with 8* of overlap. They designed it for a "Centrifugal" setup but the valve events @.50" are super close to what you're shooting for.
We calculated these out on the cam timing calculator located on our site.
IVO: 5*BTDC
IVC: 47* ABDC
EVO: 65* BBDC
EVC: 3* ATDC
If you wanted to hit those exact valve events you mentioned there's always the option of custom. We could work with you and Cam Motion, Comp, etc. on a custom cam. Although, we think that Cam Motion cam above gets you right where you want to be. Another option is an adjustable upper timing gear like our SUM-G6644-4X. We use captured-degree bushings that enable you to advance/retard the cam in two-degree increments.
It seems like from your valve drop numbers I would not be able to cut 60-70 off the heads and have any chance of the exhaust valve fitting. I don't want to buy an exhaust cutter, and you're right that intake fitment can get tricky. Cutting 20 and doing a shelf stage 3 is appealing. Yes, that's correct. That's why we recommended to just take .020" off. That will still be a nice compression bump.
What is your recommendation @Summitracing for street-friendly 4.065 x 4.00" pistons and rings that would not require any machining to the ls3 block? I suspect my Callies crank and rods are healthy that I can salvage from my 402 and I'd be a lot happier building out a 415. My 402 before I killed it pulled to 7400 and ran like hell in that car. Are your summit branded pistons a good choice? What is your targeted deck height? A lot of aftermarket pistons I've seen drop the pistons .005-.010 in the hole. I'd hope to see .005-.010 out of the hole or I'd be hard-pressed not to deck the block to set the quench.
Our Pro LS 2618 forged pistons are street-friendly. We designed them knowing folks may very well throw boost or nitrous at them. For your planned 4.065" bore 4.00" stroke we would take a look at the 6cc dished SUM-1109274065-6. That'sassuming your stroker assembly is using 6.125" rods with a .927" pin.All of our Pro LS pistons will be set at .005" in the hole. We do this because we know folks like to deck blocks and or mill heads. Using our compression calculator this would put you right around 11:1 with stock 70cc heads and .040" head gaskets. With the general rule of thumb of .006" milled equals 1cc from the chamber going .020" should get you to roughly 67cc on stock LS3 heads. That would get you to 11.3:1. Then 0 deck would get you just over 11.4:1. Pair these with our SUM-136SN9045065 file-fit rings and you'll be good to go.
Another option is Diamond Pistons has their 2cc LS3 flat top DPP-11544-R1-8. Those are at 0 deck. With .020" milled and .040" head gaskets that would get you just under 12:1. Those include file-fit rings.
We like the discussion you have going here. Let us know if we can be of any further assistance.
We figured it would be best just to grab your post and provide answers in blue.
Thank you so much! Your stage 3 does seem like a good fit. The experiment I think I'd be interested in trying for my rx7 is to move the IVC and EVO point to something more in line with your stage 4 cams, but drop the overlap to the ~6-8* range. I think top end power would stay very similar, should extend the RPM range, and I would not miss any midrange losses in such a light car with 3.90 gears and 25" tall tires. Something like IVC 50, EVO 65, IVO 4, EVC 3. Definitely an oddball for a SBE ls3 that is typically in a much larger car with longer gearing. This is also why I was considering bumping the compression as much as possible to help recover some cylinder pressure for low rpm and part throttle.
No problem. We do really like the stage 3 for what you're looking to do here. We understand wanting to try something a little different. Your idea and valve events aren't as far out there as you might think. It's completely understandable wanting to shift the powerband up in a light car so at the tap of the throttle we're not scorching the tires off. At the same time let's boost compression to help with power across the range and throttle response.
We did some digging for shelf cams that fit the bill for what you're hunting for. Take a look at this Cam Motion CXM-03-01-0049. Specs on it are .621"/.604", 232/248, 116+5 with 8* of overlap. They designed it for a "Centrifugal" setup but the valve events @.50" are super close to what you're shooting for.
We calculated these out on the cam timing calculator located on our site.
IVO: 5*BTDC
IVC: 47* ABDC
EVO: 65* BBDC
EVC: 3* ATDC
If you wanted to hit those exact valve events you mentioned there's always the option of custom. We could work with you and Cam Motion, Comp, etc. on a custom cam. Although, we think that Cam Motion cam above gets you right where you want to be. Another option is an adjustable upper timing gear like our SUM-G6644-4X. We use captured-degree bushings that enable you to advance/retard the cam in two-degree increments.
It seems like from your valve drop numbers I would not be able to cut 60-70 off the heads and have any chance of the exhaust valve fitting. I don't want to buy an exhaust cutter, and you're right that intake fitment can get tricky. Cutting 20 and doing a shelf stage 3 is appealing. Yes, that's correct. That's why we recommended to just take .020" off. That will still be a nice compression bump.
What is your recommendation @Summitracing for street-friendly 4.065 x 4.00" pistons and rings that would not require any machining to the ls3 block? I suspect my Callies crank and rods are healthy that I can salvage from my 402 and I'd be a lot happier building out a 415. My 402 before I killed it pulled to 7400 and ran like hell in that car. Are your summit branded pistons a good choice? What is your targeted deck height? A lot of aftermarket pistons I've seen drop the pistons .005-.010 in the hole. I'd hope to see .005-.010 out of the hole or I'd be hard-pressed not to deck the block to set the quench.
Our Pro LS 2618 forged pistons are street-friendly. We designed them knowing folks may very well throw boost or nitrous at them. For your planned 4.065" bore 4.00" stroke we would take a look at the 6cc dished SUM-1109274065-6. That'sassuming your stroker assembly is using 6.125" rods with a .927" pin.All of our Pro LS pistons will be set at .005" in the hole. We do this because we know folks like to deck blocks and or mill heads. Using our compression calculator this would put you right around 11:1 with stock 70cc heads and .040" head gaskets. With the general rule of thumb of .006" milled equals 1cc from the chamber going .020" should get you to roughly 67cc on stock LS3 heads. That would get you to 11.3:1. Then 0 deck would get you just over 11.4:1. Pair these with our SUM-136SN9045065 file-fit rings and you'll be good to go.
Another option is Diamond Pistons has their 2cc LS3 flat top DPP-11544-R1-8. Those are at 0 deck. With .020" milled and .040" head gaskets that would get you just under 12:1. Those include file-fit rings.
We like the discussion you have going here. Let us know if we can be of any further assistance.
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spanks13 (10-08-2021)
10-08-2021, 03:42 PM
#32
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Thinking of getting a long block crate engine from GM to get my rx7 back on the road.
2850 pounds, 6 speed, 3.90 gears, but a street car I drive semi-regularly. Used to have a 402 but I broke it, and I need a semi mild and reliable engine for it.
Engine will get rod mod Ls3 w/ 105mm tb, 1 7/8” long tubes, straight shot CAI, flex fuel capable, carbon RPS clutch -
1) Leave the heads on, ~227/238 on 113+2 cam something “stage 2” ish around 6* of overlap
2) Take the heads off and do a hand cleanup on the ports, cut the heads to ~12:1 compression, flycut the pistons, Johnson 2116 lifters, and run like a 233/246 115+2 cam - still shooting for ~6* overlap, but longer duration and later IVC to shoot for carrying power up to 7000+
I haven’t really seen any cams or putting the IVC at 48-50* for a SBE Ls3, but all the shelf cams are making compromises for PTV clearance. At 12:1 and cutting valve reliefs I think it would work?
Open to input on cams on either plan.
2850 pounds, 6 speed, 3.90 gears, but a street car I drive semi-regularly. Used to have a 402 but I broke it, and I need a semi mild and reliable engine for it.
Engine will get rod mod Ls3 w/ 105mm tb, 1 7/8” long tubes, straight shot CAI, flex fuel capable, carbon RPS clutch -
1) Leave the heads on, ~227/238 on 113+2 cam something “stage 2” ish around 6* of overlap
2) Take the heads off and do a hand cleanup on the ports, cut the heads to ~12:1 compression, flycut the pistons, Johnson 2116 lifters, and run like a 233/246 115+2 cam - still shooting for ~6* overlap, but longer duration and later IVC to shoot for carrying power up to 7000+
I haven’t really seen any cams or putting the IVC at 48-50* for a SBE Ls3, but all the shelf cams are making compromises for PTV clearance. At 12:1 and cutting valve reliefs I think it would work?
Open to input on cams on either plan.
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G Atsma (10-08-2021)
10-08-2021, 04:19 PM
#33
what would you call it then? I would think it’s a fairly serious cam. Not small at all. Being a LS3
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spanks13 (10-08-2021)
10-08-2021, 04:50 PM
#34
Haha! The car won't be mild that is definitely true. Driving a well setup LS FD is quite the experience. I guess semi mild I mean just the idle quality and driving around town. It could idle without crazy chop and would have just a little bit of lope if the overlap is kept to ~6-8 degrees that is stage 1 or 2 territory in internet speak. Texas Speed stage 2 is 12.5 degrees overlap for example.
10-08-2021, 05:21 PM
#35
@spanks13,
We figured it would be best just to grab your post and provide answers in blue.
Thank you so much! Your stage 3 does seem like a good fit. The experiment I think I'd be interested in trying for my rx7 is to move the IVC and EVO point to something more in line with your stage 4 cams, but drop the overlap to the ~6-8* range. I think top end power would stay very similar, should extend the RPM range, and I would not miss any midrange losses in such a light car with 3.90 gears and 25" tall tires. Something like IVC 50, EVO 65, IVO 4, EVC 3. Definitely an oddball for a SBE ls3 that is typically in a much larger car with longer gearing. This is also why I was considering bumping the compression as much as possible to help recover some cylinder pressure for low rpm and part throttle.
No problem. We do really like the stage 3 for what you're looking to do here. We understand wanting to try something a little different. Your idea and valve events aren't as far out there as you might think. It's completely understandable wanting to shift the powerband up in a light car so at the tap of the throttle we're not scorching the tires off. At the same time let's boost compression to help with power across the range and throttle response.
We did some digging for shelf cams that fit the bill for what you're hunting for. Take a look at this Cam Motion CXM-03-01-0049. Specs on it are .621"/.604", 232/248, 116+5 with 8* of overlap. They designed it for a "Centrifugal" setup but the valve events @.50" are super close to what you're shooting for.
*snip*
We like the discussion you have going here. Let us know if we can be of any further assistance.
We figured it would be best just to grab your post and provide answers in blue.
Thank you so much! Your stage 3 does seem like a good fit. The experiment I think I'd be interested in trying for my rx7 is to move the IVC and EVO point to something more in line with your stage 4 cams, but drop the overlap to the ~6-8* range. I think top end power would stay very similar, should extend the RPM range, and I would not miss any midrange losses in such a light car with 3.90 gears and 25" tall tires. Something like IVC 50, EVO 65, IVO 4, EVC 3. Definitely an oddball for a SBE ls3 that is typically in a much larger car with longer gearing. This is also why I was considering bumping the compression as much as possible to help recover some cylinder pressure for low rpm and part throttle.
No problem. We do really like the stage 3 for what you're looking to do here. We understand wanting to try something a little different. Your idea and valve events aren't as far out there as you might think. It's completely understandable wanting to shift the powerband up in a light car so at the tap of the throttle we're not scorching the tires off. At the same time let's boost compression to help with power across the range and throttle response.
We did some digging for shelf cams that fit the bill for what you're hunting for. Take a look at this Cam Motion CXM-03-01-0049. Specs on it are .621"/.604", 232/248, 116+5 with 8* of overlap. They designed it for a "Centrifugal" setup but the valve events @.50" are super close to what you're shooting for.
*snip*
We like the discussion you have going here. Let us know if we can be of any further assistance.
I've been through so many iterations with my car to try and get the powerband how I wanted it and my experience is that if you want it to rev, especially a 4" stroke motor, you need some cam duration. Balancing that with a stealthy streetable engine is kind of difficult you have to compromise somewhere. I'm willing to compromise midrange and overall power to keep the idle and low speed a bit stealthier, but I still want the top end revs. Definitely won't be the ideal NA cam for other vehicles.
End of the day, I think there are a lot of perks to a "blower cam" in the right NA application. The custom cam I ground way back in the day was a 226/242 on 117 and it actually ran great for what it was, I just could never extend power peak past 6200 rpm until I finally put a bigger cam in it. Covid boredom led me to put an old LS7S TSP cam in it I bought used for cheap at 242/250 on 114 and it drove like absolute crap, but it definitely gave it the powerband I wanted. It was honestly more power than the car needed with that cam without question it was 9 second power levels at that weight, but having an engine that rewards you for reving it matches the character of the car, and compliments the handling. I mean...the funny thing is the stock rotary only horsepower peaked at 6500. They weren't the 10,000 rpm engines everyone believes them to be from the factory so with the right LS build you're actually reving higher than a lot of the rotaries out there, plus you get the low end power and response of an NA engine.
The following 2 users liked this post by spanks13:
grubinski (10-08-2021), Summitracing (10-12-2021)
10-08-2021, 06:57 PM
#36
LS powered RX7 that’s something I need in my life. 🤔 going to keep my eyes peeled for one.
10-12-2021, 10:58 AM
#37
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spanks13,
We enjoy interacting with the community providing advice and recommendations. Sometimes we're learning just as much as we're teaching. The good-hearted banter between the community keeps things fun and entertaining!
Saving up and moving the build to a 415 stroker instead of a stock LS3 is understandable. It sounds like you already have a good crank and rods to get started so why not right? There's no replacement for displacement! Key up the boost comments
We like that you've been on the trial and error train trying to get the results you want. That's all part of the game. There's nothing wrong with building the combo out how you want it. It's your build and your goals. The community is here to provide advice and recommendations when you ask for them.
If you haven't already, get a build thread going for the new 415 venture for the RX7. We'll be sure to jump in on it and follow along
We enjoy interacting with the community providing advice and recommendations. Sometimes we're learning just as much as we're teaching. The good-hearted banter between the community keeps things fun and entertaining!
Saving up and moving the build to a 415 stroker instead of a stock LS3 is understandable. It sounds like you already have a good crank and rods to get started so why not right? There's no replacement for displacement! Key up the boost comments
We like that you've been on the trial and error train trying to get the results you want. That's all part of the game. There's nothing wrong with building the combo out how you want it. It's your build and your goals. The community is here to provide advice and recommendations when you ask for them.
If you haven't already, get a build thread going for the new 415 venture for the RX7. We'll be sure to jump in on it and follow along
10-13-2021, 08:09 AM
#38
Thinking of getting a long block crate engine from GM to get my rx7 back on the road.
2850 pounds, 6 speed, 3.90 gears, but a street car I drive semi-regularly. Used to have a 402 but I broke it, and I need a semi mild and reliable engine for it.
Engine will get rod mod Ls3 w/ 105mm tb, 1 7/8” long tubes, straight shot CAI, flex fuel capable, carbon RPS clutch -
1) Leave the heads on, ~227/238 on 113+2 cam something “stage 2” ish around 6* of overlap
2) Take the heads off and do a hand cleanup on the ports, cut the heads to ~12:1 compression, flycut the pistons, Johnson 2116 lifters, and run like a 233/246 115+2 cam - still shooting for ~6* overlap, but longer duration and later IVC to shoot for carrying power up to 7000+
I haven’t really seen any cams or putting the IVC at 48-50* for a SBE Ls3, but all the shelf cams are making compromises for PTV clearance. At 12:1 and cutting valve reliefs I think it would work?
Open to input on cams on either plan.
2850 pounds, 6 speed, 3.90 gears, but a street car I drive semi-regularly. Used to have a 402 but I broke it, and I need a semi mild and reliable engine for it.
Engine will get rod mod Ls3 w/ 105mm tb, 1 7/8” long tubes, straight shot CAI, flex fuel capable, carbon RPS clutch -
1) Leave the heads on, ~227/238 on 113+2 cam something “stage 2” ish around 6* of overlap
2) Take the heads off and do a hand cleanup on the ports, cut the heads to ~12:1 compression, flycut the pistons, Johnson 2116 lifters, and run like a 233/246 115+2 cam - still shooting for ~6* overlap, but longer duration and later IVC to shoot for carrying power up to 7000+
I haven’t really seen any cams or putting the IVC at 48-50* for a SBE Ls3, but all the shelf cams are making compromises for PTV clearance. At 12:1 and cutting valve reliefs I think it would work?
Open to input on cams on either plan.
😭
How did we get to a stroker from this
The following 2 users liked this post by Corona:
NAVYBLUE210 (10-13-2021), spanks13 (10-13-2021)
10-13-2021, 11:19 AM
#39
It is only $750 more for pistons and rings and balancing since I have a crank and rods the rest is just putting it together. I don't think I can get wooded up about a stock ls3 with just a cam in a car that I've always had a built motor.