building a cheap short stroke motor
05-04-2012, 03:03 PM
#21
They will not have correct journal or pin size, or length.
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05-04-2012, 03:10 PM
#23
Ive often thought about a motor ive wanted to put together
LQ block 6.0 +.060
LR4 crank/rods (4.8)
+.060 over replacement speed pro lq4 pistons
Clevite bearings
precision machining/balancing/assembly/clearances.
This makes 338ci. I believe it will handle 8000rpm shifts.
I would use 243 heads and ls6 intake.
Of course Jesel rockers. LPE GT11 cam. 10:1 scr
I think this motor would do well in a road race/circuit/autox car.
I would use it in 3rd gen camaro with a t56.
I think it would be very responsive, wind up quick and recover fast out of corners
LQ block 6.0 +.060
LR4 crank/rods (4.8)
+.060 over replacement speed pro lq4 pistons
Clevite bearings
precision machining/balancing/assembly/clearances.
This makes 338ci. I believe it will handle 8000rpm shifts.
I would use 243 heads and ls6 intake.
Of course Jesel rockers. LPE GT11 cam. 10:1 scr
I think this motor would do well in a road race/circuit/autox car.
I would use it in 3rd gen camaro with a t56.
I think it would be very responsive, wind up quick and recover fast out of corners
05-04-2012, 04:07 PM
#24
Yes and no...shelf stock won't work....BBC comes closest with the 6.535" length, but has the wrong sizing on both ends.
Likely going to be a custom rod (there goes the budget aspect of this build). Might be less expensive and faster build time to get a shelf stock rod and custom piston!
Likely going to be a custom rod (there goes the budget aspect of this build). Might be less expensive and faster build time to get a shelf stock rod and custom piston!
05-04-2012, 04:51 PM
#25
Was the the 1st crank of the 2nd one he was selling? I thought about getting one and building a motor for MNCA mean street, 331 cube screamer. go small journal, cam, heads were gona rock, didnt like the TB, intake I could run. And would be able to get alot of street miles lol.
Are you doing this for a class?
Are you doing this for a class?
05-04-2012, 06:24 PM
#26
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Interesting concept but..... Pulling off 8000+ rpm is going to take very high quality and light weight valve train components to have any reliability. Likely want to consider solid roller and this requires adjustable rockers etc. Nothing here remotely close to stock in costs. Your 330 could end up an expensive build.
Look for a very light weight car for this kind of engine.
Look for a very light weight car for this kind of engine.
05-04-2012, 09:01 PM
#27
Was the the 1st crank of the 2nd one he was selling? I thought about getting one and building a motor for MNCA mean street, 331 cube screamer. go small journal, cam, heads were gona rock, didnt like the TB, intake I could run. And would be able to get alot of street miles lol.
Are you doing this for a class?
Are you doing this for a class?
No class, no one could ever say I had any class
05-04-2012, 09:02 PM
#28
Interesting concept but..... Pulling off 8000+ rpm is going to take very high quality and light weight valve train components to have any reliability. Likely want to consider solid roller and this requires adjustable rockers etc. Nothing here remotely close to stock in costs. Your 330 could end up an expensive build.
Look for a very light weight car for this kind of engine.
Look for a very light weight car for this kind of engine.
05-09-2012, 08:37 AM
#31
I have to go custom. Having a set made for 754.00 and change. They will also balance the rotating assembly and install a reluctor wheel for the same fundage. Sent the crank and pistons out Monday. 6 weeks, I should have it all back.
This project is still uber cheap. Grabbing a 6.0L block from Summit for 800.00 shipped. LS3/L92 heads, the SLP roller rockers I already own, "hot cam" and call this project acquired. Junk 5.3L (200.00) for all the covers and stuff.
GMPP or Edelbrock carb intake with MSD for spark. Should rev well and I found a 72 Camaro that this will go in with the 6 speed manual I have.
05-09-2012, 09:45 AM
#32
Just make sure the big and small ends are both the right size. It's easy to find close to the length you need, but going to be VERY difficult to find anything in regular production with the right journal and pin size too!
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05-09-2012, 12:49 PM
#34
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It appears that the original intent was to build a "cheap" short stroke motor. The rods appear to be either a major expense or a weak link to an otherwise stout rotating assembly. Not to rain on your parade but wouldn't it make more sense to find a 4.8. Bore it to an LS1 bore that provides you the least expensive LS1/LS6 forged piston (Usually performance forging are hard to find for standard bores). The LS1/LS6 pistons are the proper compression height for a stock 4.8 crank and rods (3.268 stroke/6.275 rod length). Finishing the assembly with ARP rod bolts, ARP studs in the mains and heads would give you a proven tough combination.
This combination or the one NemeSS suggests is going to allow you extra money to build a valve train that can handle the rpm your going to throw at it. Think titanium. Think very expensive.
This combination or the one NemeSS suggests is going to allow you extra money to build a valve train that can handle the rpm your going to throw at it. Think titanium. Think very expensive.
05-09-2012, 03:23 PM
#35
It appears that the original intent was to build a "cheap" short stroke motor. The rods appear to be either a major expense or a weak link to an otherwise stout rotating assembly. Not to rain on your parade but wouldn't it make more sense to find a 4.8. Bore it to an LS1 bore that provides you the least expensive LS1/LS6 forged piston (Usually performance forging are hard to find for standard bores). The LS1/LS6 pistons are the proper compression height for a stock 4.8 crank and rods (3.268 stroke/6.275 rod length). Finishing the assembly with ARP rod bolts, ARP studs in the mains and heads would give you a proven tough combination.
This combination or the one NemeSS suggests is going to allow you extra money to build a valve train that can handle the rpm your going to throw at it.
This combination or the one NemeSS suggests is going to allow you extra money to build a valve train that can handle the rpm your going to throw at it.
.....
Last edited by Grendel; 05-26-2013 at 11:07 AM.
05-09-2012, 05:58 PM
#36
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I guess "cheap" is relative. Obviously, my interpretation of cheap is different than yours in this application. You're going to have a tidy sum tied up in this motor but if your pocket allows it, who am I to tell you different.
That being said, here is my experience. You can actually go too long on your rod to stroke ratio to where there is diminishing returns and you've got a sluggish motor on the low end. My problem with doing years of research on long rod motors is off the shelf cams are not going to work for you. There are engine dynamics involved such as increased dwell time at TDC that call for an unusual cam grind and unusual header design. Don't take my word for it. Call the tech support for a few popular cam companies. Tell them what you are proposing and ask what cam grind they suggest. I bet you'll get as many different suggestions and theories.
Here is my suggestion. Sell the pistons you have. They are for a stroker application where the compression height is actually working against you. Then purchase a stock LS2/6.0 forging with a more reasonable compression height (I believe it's 1.341). Now you can purchase off the shelf Eagle H-beams with a 6.300 length (part number CRS6300B3D) for a shade over $500. The final desired piston deck height can be easily found by milling. Check my math but I believe you'll be there with a more reasonable rod to stroke ratio.
That being said, here is my experience. You can actually go too long on your rod to stroke ratio to where there is diminishing returns and you've got a sluggish motor on the low end. My problem with doing years of research on long rod motors is off the shelf cams are not going to work for you. There are engine dynamics involved such as increased dwell time at TDC that call for an unusual cam grind and unusual header design. Don't take my word for it. Call the tech support for a few popular cam companies. Tell them what you are proposing and ask what cam grind they suggest. I bet you'll get as many different suggestions and theories.
Here is my suggestion. Sell the pistons you have. They are for a stroker application where the compression height is actually working against you. Then purchase a stock LS2/6.0 forging with a more reasonable compression height (I believe it's 1.341). Now you can purchase off the shelf Eagle H-beams with a 6.300 length (part number CRS6300B3D) for a shade over $500. The final desired piston deck height can be easily found by milling. Check my math but I believe you'll be there with a more reasonable rod to stroke ratio.
05-09-2012, 08:07 PM
#39
I guess "cheap" is relative. Obviously, my interpretation of cheap is different than yours in this application. You're going to have a tidy sum tied up in this motor but if your pocket allows it, who am I to tell you different.
That being said, here is my experience. You can actually go too long on your rod to stroke ratio to where there is diminishing returns and you've got a sluggish motor on the low end. My problem with doing years of research on long rod motors is off the shelf cams are not going to work for you. There are engine dynamics involved such as increased dwell time at TDC that call for an unusual cam grind and unusual header design. Don't take my word for it. Call the tech support for a few popular cam companies. Tell them what you are proposing and ask what cam grind they suggest. I bet you'll get as many different suggestions and theories.
Here is my suggestion. Sell the pistons you have. They are for a stroker application where the compression height is actually working against you. Then purchase a stock LS2/6.0 forging with a more reasonable compression height (I believe it's 1.341). Now you can purchase off the shelf Eagle H-beams with a 6.300 length (part number CRS6300B3D) for a shade over $500. The final desired piston deck height can be easily found by milling. Check my math but I believe you'll be there with a more reasonable rod to stroke ratio.
That being said, here is my experience. You can actually go too long on your rod to stroke ratio to where there is diminishing returns and you've got a sluggish motor on the low end. My problem with doing years of research on long rod motors is off the shelf cams are not going to work for you. There are engine dynamics involved such as increased dwell time at TDC that call for an unusual cam grind and unusual header design. Don't take my word for it. Call the tech support for a few popular cam companies. Tell them what you are proposing and ask what cam grind they suggest. I bet you'll get as many different suggestions and theories.
Here is my suggestion. Sell the pistons you have. They are for a stroker application where the compression height is actually working against you. Then purchase a stock LS2/6.0 forging with a more reasonable compression height (I believe it's 1.341). Now you can purchase off the shelf Eagle H-beams with a 6.300 length (part number CRS6300B3D) for a shade over $500. The final desired piston deck height can be easily found by milling. Check my math but I believe you'll be there with a more reasonable rod to stroke ratio.
Thanks. 3K is expensive for a fully forged shortish stroke motor?
I will probably save the pistons I have and grab something different, as you suggest. Except that I already own the crank, too. Short 3.185 stroke.
Last edited by Grendel; 05-09-2012 at 09:16 PM.
05-10-2012, 02:39 PM
#40
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Yup....I figured in your crank. Math goes something like this. 3.185 divided by two=1.5925 plus piston compression height (1.341)= 2.9335". Deck height on an LS motor is 9.240". 9.240" - 2.9335" give you a required rod length of 6.3065". Eagle rods I mentioned are 6.30". Should put you right where you need to be.
3K is pretty good for a forged short block. You still need a good set of heads with at least lightweight LS6 valves or better, lighter titanium valves to spin to 10K. Titanium retainers are going to be mandatory along with some premium valve springs. Custom cam for long rod to stroke ratio might be in order and an oil pan that can control that kind of rotating assembly rpm with a high quality oil pump. I'm not familiar with Summit's machined blocks but blue print machining including torque plate honing, squaring, decking will be necessary if you want this thing to live awhile. Studing the mains and probably the heads would be smart.
3K is pretty good for a forged short block. You still need a good set of heads with at least lightweight LS6 valves or better, lighter titanium valves to spin to 10K. Titanium retainers are going to be mandatory along with some premium valve springs. Custom cam for long rod to stroke ratio might be in order and an oil pan that can control that kind of rotating assembly rpm with a high quality oil pump. I'm not familiar with Summit's machined blocks but blue print machining including torque plate honing, squaring, decking will be necessary if you want this thing to live awhile. Studing the mains and probably the heads would be smart.