Am I ok on 91 pump gas?
10-25-2021, 03:40 PM
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Am I ok on 91 pump gas? I have a 2007 GMC Sierra that came with the LH6. A 5.3 Gen IV with DOD. It has 220,000 miles on it. The lifters had been making noise for a while and I was waiting for the eventual demise of said lifter. Well, suddenly had multiple misfires and no compression in Cylinder 1. All the rockers seem to be moving as expected.... but regardless. It is getting a new engine, I had been planning on it anyways. I don't want DOD, so a stock long block is out of the question. This truck is a daily driver, plus the vehicle I use to tow my travel trailer/dirtbikes etc. So my plan is to go to a 6.0 with a stage 2 truck cam and raise the compression a bit. I have done tons of research combined with building a few smaller, completely stock engines in the past, and a bunch of dirtbike engines. And youtube/forums, I hope I can handle it. I just need someone to look over my engine math as I am about to start buying parts.
*Cam: SUM-8707r1 226/238@50, 113 lobe sep, adv 3, .600/.600/ IVC 43 ABDC.
You can see the specs according to summit for the ly6 block here. https://help.summitracing.com/app/an...6-engine-specs
But with the compression height of the piston, along with the connecting rod length, stroke, and deck hight this should give me a deck clearance of 0.00099 in the hole.
9.240 - ((3.622/2)+6.098+1.330) = -0.0009999999999
This combination would give me a static compression of 10.14 And a quench of .040
According to this calculator at gofastmath (https://www.gofastmath.com/Compressi...tio-Calculator) all this combined with the intake valve closing at 43 ABDC that gives me a dynamic compression ratio of 8.48:1
From my research, a dynamic of 8.5:1 is the farthest you want to push it on 91 octane at the pump even with aluminum heads, but the actual numbers on the internet are fuzzy. I was hoping someone with more experience on here could chime in with how close they may have been without having to pull too much timing out of the tune.
Thank you in advance and any advice on how to get more torque is welcome. I am ready to shoot that 4l60 right out the bottom of the truck.
- Block, I am looking at a ly6 6.0 block off of ebay with a standard 4" bore with the DOD towers already closed.
- I am planning on having my own crank polished since the 6.0 and 5.3 share the same crank and 58x reluctor wheel.
- I plan on having my stock rods rebushed. (Full floating Gen IV)
*Cam: SUM-8707r1 226/238@50, 113 lobe sep, adv 3, .600/.600/ IVC 43 ABDC.
- Using my stock 799/243 heads having them milled 10 thousandths to give a 63cc combustion chamber. and install Pac KS13 springs with a max lift of .625 https://www.lsxceleration.com/pac-ks...ners-7-degree/
- Pistons with a 10cc dish a 1.330 compression height https://www.summitracing.com/parts/d...make/chevrolet
- a .040 with a 4.100 bore cometic head gasket
You can see the specs according to summit for the ly6 block here. https://help.summitracing.com/app/an...6-engine-specs
But with the compression height of the piston, along with the connecting rod length, stroke, and deck hight this should give me a deck clearance of 0.00099 in the hole.
9.240 - ((3.622/2)+6.098+1.330) = -0.0009999999999
This combination would give me a static compression of 10.14 And a quench of .040
- Cylinder Bore (inches): 4
- Stroke (inches): 3.622
- Cylinder Head Chamber Volume (CC's): 62.8
- Piston Dish/Dome (CC's): (enter negative # for dome) 10
- Head Gasket Thickness (inches): (.038 is a typical value) 0.04
- Head Gasket Bore (inches): 4.1
- Deck Clearance (inches): (.020 is a typical value) .0009
- Optional for Dynamic CR
- Connecting Rod Length (inches): 6.098
- IVC @ .050": 43
According to this calculator at gofastmath (https://www.gofastmath.com/Compressi...tio-Calculator) all this combined with the intake valve closing at 43 ABDC that gives me a dynamic compression ratio of 8.48:1
From my research, a dynamic of 8.5:1 is the farthest you want to push it on 91 octane at the pump even with aluminum heads, but the actual numbers on the internet are fuzzy. I was hoping someone with more experience on here could chime in with how close they may have been without having to pull too much timing out of the tune.
Thank you in advance and any advice on how to get more torque is welcome. I am ready to shoot that 4l60 right out the bottom of the truck.
10-25-2021, 04:01 PM
#2
I think that cam is a little too big for a truck, not to mention, no mention of a stall or gears AND you tow with it. You should easily be able to run 10.14:1 on 91 octane. Its just a factor of how much timing it'll accept. More compression requires less timing. Do you have a TARGET amount of advance you want to run? And if you do, why? It'll probably make more power with 10.14:1 with 22-24 degrees of timing vs running 9:1 with 28-29 degrees of timing. If you already have the pistons, just run it and adjust the timing accordingly. i still wouldnt use that big of a cam in a full size truck unless you are running about a 3800 stall.....which i would not tow with.
And On the 4l60, that transmission would easily hold that small amount of power with a few light upgrades. i did a moderate build for a buddy of mine with 470rwhp in a gto and its been going for 3-4 years now. well I built him a turbo kit for the car now so it's probably making a decent amount more......If you don't know a good builder, just put a 4l80 in it
And On the 4l60, that transmission would easily hold that small amount of power with a few light upgrades. i did a moderate build for a buddy of mine with 470rwhp in a gto and its been going for 3-4 years now. well I built him a turbo kit for the car now so it's probably making a decent amount more......If you don't know a good builder, just put a 4l80 in it
10-25-2021, 04:21 PM
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It was a stage 2 "Truck Cam" It says a 2500 stall is "a plus", but not required. Is it the lobe separation? I plan on installing a slightly higher stall eventually... when the 4l60 with 220,000 miles on it grenades itself. I considered a 4l80, but finding info on bolting my transfer case to it was a little muddy. I found a few places that claim their $2k 4l60e can handle 600+ Hp. And have a good warranty to back it up. So I was planning on going that route. As far as timing. I didn't have a specific goal, I just didn't want to have major preignition issues. The 10.14 static isn't what I was worried about, it was the 8.45 dynamic with that cam. I don't mind a lope, I don't mind needing a slightly higher stall as long as it is streetable until I get one. I do mind having to find race gas everytime I fill up because it won't run without it.
10-25-2021, 04:54 PM
#4
It was a stage 2 "Truck Cam" It says a 2500 stall is "a plus", but not required. Is it the lobe separation? I plan on installing a slightly higher stall eventually... when the 4l60 with 220,000 miles on it grenades itself. I considered a 4l80, but finding info on bolting my transfer case to it was a little muddy. I found a few places that claim their $2k 4l60e can handle 600+ Hp. And have a good warranty to back it up. So I was planning on going that route. As far as timing. I didn't have a specific goal, I just didn't want to have major preignition issues. The 10.14 static isn't what I was worried about, it was the 8.45 dynamic with that cam. I don't mind a lope, I don't mind needing a slightly higher stall as long as it is streetable until I get one. I do mind having to find race gas everytime I fill up because it won't run without it.
like, wut????
I think you are way over/under thinking this. That compression will be fine, you may have to take a couple degrees out of it. As far as it not running without race gas…I’m not sure why you would think that.
that duration is more than I’d want in a heavy truck, especially with no stall or gears. This combo sounds like a train wreck.
The following 2 users liked this post by Kfxguy:
68Formula (10-25-2021), 99 Black Bird T/A (11-02-2021)
10-25-2021, 07:06 PM
#5
The 8707R1 that you referenced is not a "truck stage 2 cam." That's meant for a lighter vehicle. Their Stage 2 Truck Cam is the 8720R1, would be a much better choice and still work with that setup on 91 (with proper tuning).
Make sure to run a larger cooler with that trans, especially if planning on towing.
Make sure to run a larger cooler with that trans, especially if planning on towing.
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G Atsma (10-26-2021)
10-26-2021, 01:05 AM
#6
Jeremy, I think you are worried about the wrong thing. This sounds like a prime candidate for a quick engine swap or rebuilding the engine you have, and investing the money you would have spent on some sort of forced induction if you want to go faster.
You claim you have zero compression in hole #1, is it really zero zero or just low? Because if it's actually zero it's either the head or head gasket, and if it is the head gasket tear it down quick as it make leak water into your bore and rust instantly. If it does have the head issue, you will pay $$$ to fix the head before you can use them again, can't just slap them on your new block.
Your 5.3 crank and rods are probably fine, it's a later engine with the improved rods, BUT whether put them in a new block or not, you will need new pistons and therefore need to have it balanced, which will set you back $250. You also need to have said pistons in hand when this takes place.
When you try to play games with internet parts-matching you will often have a much harder and more expensive time than you think. That ebay block may be junk. You can also bore the 5.3 block over about .060 with plenty of material leftover, giving you more cubic inches. A competent machine shop will make sure your block is straight, decked, and has new cam bearings. All of that work, including the balance of the rotating assembly, will probably run $900-1000, but it will be right, not a questionable ebay block that may be warped.
As for CAM, I would recommend CALLING someone, like Comp, Crane, or another reputable manufacturer. Seriously this is the best option, because they have their combined experience.
This, topped with a reproduction Trailblazer SS intake will make 375hp just fine on 91 octane gas. If you want to go faster, add forced induction.
You can do what you want, you don't know me, but this option uses 90% what you already have, and won't generate a junk engine to store. Don't fear the machine shop, especially if you need to do something right the first time.
This will not be cheap, no matter what you get, not will it be easy, and you don't run a stock cam you will need a custom tune. If you want cheap and reliable, get a Craigslist or Facebook Marketplace engine, hear it run, check it's oil filter for shavings, and if it's good then swap it. Tearing down and building up new will always cost more.
You claim you have zero compression in hole #1, is it really zero zero or just low? Because if it's actually zero it's either the head or head gasket, and if it is the head gasket tear it down quick as it make leak water into your bore and rust instantly. If it does have the head issue, you will pay $$$ to fix the head before you can use them again, can't just slap them on your new block.
Your 5.3 crank and rods are probably fine, it's a later engine with the improved rods, BUT whether put them in a new block or not, you will need new pistons and therefore need to have it balanced, which will set you back $250. You also need to have said pistons in hand when this takes place.
When you try to play games with internet parts-matching you will often have a much harder and more expensive time than you think. That ebay block may be junk. You can also bore the 5.3 block over about .060 with plenty of material leftover, giving you more cubic inches. A competent machine shop will make sure your block is straight, decked, and has new cam bearings. All of that work, including the balance of the rotating assembly, will probably run $900-1000, but it will be right, not a questionable ebay block that may be warped.
As for CAM, I would recommend CALLING someone, like Comp, Crane, or another reputable manufacturer. Seriously this is the best option, because they have their combined experience.
This, topped with a reproduction Trailblazer SS intake will make 375hp just fine on 91 octane gas. If you want to go faster, add forced induction.
You can do what you want, you don't know me, but this option uses 90% what you already have, and won't generate a junk engine to store. Don't fear the machine shop, especially if you need to do something right the first time.
This will not be cheap, no matter what you get, not will it be easy, and you don't run a stock cam you will need a custom tune. If you want cheap and reliable, get a Craigslist or Facebook Marketplace engine, hear it run, check it's oil filter for shavings, and if it's good then swap it. Tearing down and building up new will always cost more.
10-26-2021, 08:18 AM
#7
Jeremy, I think you are worried about the wrong thing. This sounds like a prime candidate for a quick engine swap or rebuilding the engine you have, and investing the money you would have spent on some sort of forced induction if you want to go faster.
You claim you have zero compression in hole #1, is it really zero zero or just low? Because if it's actually zero it's either the head or head gasket, and if it is the head gasket tear it down quick as it make leak water into your bore and rust instantly. If it does have the head issue, you will pay $$$ to fix the head before you can use them again, can't just slap them on your new block.
Your 5.3 crank and rods are probably fine, it's a later engine with the improved rods, BUT whether put them in a new block or not, you will need new pistons and therefore need to have it balanced, which will set you back $250. You also need to have said pistons in hand when this takes place.
When you try to play games with internet parts-matching you will often have a much harder and more expensive time than you think. That ebay block may be junk. You can also bore the 5.3 block over about .060 with plenty of material leftover, giving you more cubic inches. A competent machine shop will make sure your block is straight, decked, and has new cam bearings. All of that work, including the balance of the rotating assembly, will probably run $900-1000, but it will be right, not a questionable ebay block that may be warped.
As for CAM, I would recommend CALLING someone, like Comp, Crane, or another reputable manufacturer. Seriously this is the best option, because they have their combined experience. if he calls three different cam companies, he will get three different suggestions. No one can ever agree on the same thing when it comes to cam choice. My advice is run something around 216-218 degrees on the intake and 224-228 on the exhaust with about a 114-115 lobe seperation. I'd still advise running a small convertor like a trailblazer convertor.
This, topped with a reproduction Trailblazer SS intake will make 375hp just fine on 91 octane gas. If you want to go faster, add forced induction.
You can do what you want, you don't know me, but this option uses 90% what you already have, and won't generate a junk engine to store. Don't fear the machine shop, especially if you need to do something right the first time.
This will not be cheap, no matter what you get, not will it be easy, and you don't run a stock cam you will need a custom tune. If you want cheap and reliable, get a Craigslist or Facebook Marketplace engine, hear it run, check it's oil filter for shavings, and if it's good then swap it. Tearing down and building up new will always cost more.
You claim you have zero compression in hole #1, is it really zero zero or just low? Because if it's actually zero it's either the head or head gasket, and if it is the head gasket tear it down quick as it make leak water into your bore and rust instantly. If it does have the head issue, you will pay $$$ to fix the head before you can use them again, can't just slap them on your new block.
Your 5.3 crank and rods are probably fine, it's a later engine with the improved rods, BUT whether put them in a new block or not, you will need new pistons and therefore need to have it balanced, which will set you back $250. You also need to have said pistons in hand when this takes place.
When you try to play games with internet parts-matching you will often have a much harder and more expensive time than you think. That ebay block may be junk. You can also bore the 5.3 block over about .060 with plenty of material leftover, giving you more cubic inches. A competent machine shop will make sure your block is straight, decked, and has new cam bearings. All of that work, including the balance of the rotating assembly, will probably run $900-1000, but it will be right, not a questionable ebay block that may be warped.
As for CAM, I would recommend CALLING someone, like Comp, Crane, or another reputable manufacturer. Seriously this is the best option, because they have their combined experience. if he calls three different cam companies, he will get three different suggestions. No one can ever agree on the same thing when it comes to cam choice. My advice is run something around 216-218 degrees on the intake and 224-228 on the exhaust with about a 114-115 lobe seperation. I'd still advise running a small convertor like a trailblazer convertor.
This, topped with a reproduction Trailblazer SS intake will make 375hp just fine on 91 octane gas. If you want to go faster, add forced induction.
You can do what you want, you don't know me, but this option uses 90% what you already have, and won't generate a junk engine to store. Don't fear the machine shop, especially if you need to do something right the first time.
This will not be cheap, no matter what you get, not will it be easy, and you don't run a stock cam you will need a custom tune. If you want cheap and reliable, get a Craigslist or Facebook Marketplace engine, hear it run, check it's oil filter for shavings, and if it's good then swap it. Tearing down and building up new will always cost more.
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G Atsma (10-26-2021)
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10-26-2021, 11:51 AM
#8
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The only thing I'd like to add is this; with a bit more cam, it will lower the dynamic compression ratio, and the required octane. But you can't go too wild just to be able to crank up the timing. If it was my truck, I'd probably try to find a good Hi performance truck/engine builder, and get their input. I'll recommend an LS engine builder who is among the most knowledgeable LS guys in the world. Call and talk to Kurt Urban@SDPC (Scoggin Dickey). He has a built, full size truck. It was on the cover of a Will Handzel book about building an LS engine. Can't remember the name, and I have the book, but it's at another place. Talk to Kurt, a down to earth expert, who will steer you right. My .02.....
10-26-2021, 12:26 PM
#9
The only thing I'd like to add is this; with a bit more cam, it will lower the dynamic compression ratio, and the required octane. But you can't go too wild just to be able to crank up the timing. If it was my truck, I'd probably try to find a good Hi performance truck/engine builder, and get their input. I'll recommend an LS engine builder who is among the most knowledgeable LS guys in the world. Call and talk to Kurt Urban@SDPC (Scoggin Dickey). He has a built, full size truck. It was on the cover of a Will Handzel book about building an LS engine. Can't remember the name, and I have the book, but it's at another place. Talk to Kurt, a down to earth expert, who will steer you right. My .02.....
The following 5 users liked this post by Kfxguy:
68Formula (10-26-2021), 99 Black Bird T/A (11-02-2021), Che70velle (10-26-2021), grubinski (10-27-2021), RedXray (10-27-2021)
10-28-2021, 09:00 PM
#10
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10:1 is not high compression. I think he needs to worry with picking a more suitable cam and be realistic with how things work. If he goes with this vehicle, the cam he has picked with no stall, it’s going to be a dog. I had a 99 Silverado, stock 5.3 with a 212/218 cam, trailblazer converter, 4.10 gears. I pulled a 7200lb camper with that truck. It did it ok, but when I bought a 2017 Silverado with a 5.3, it pulled it far better with less power. I raced the two trucks, the older truck would get beat off the line, then pull hard past the 2017 and walk off and leave it, and I had a much smaller cam than he’s picking. Yet the 2017 pulled the same trailer like it was nothing. I think he’s putting together a mismatched combo. The cam is too big to tow with. And too big to not have a stall.
11-01-2021, 01:24 PM
#11
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OP,
We agree with 68Formula and kfxguy. It looks like you mixed up the cam info. The SUM-8707R1 you provided specs of is our stage 2 automotive "car" cam. That wouldn't be a good match for your combo and goals. It would be better suited for a 5.7 or 6.0 in something like a 4th gen F-body. The SUM-8720R1 is the stage 2 truck high-lift cam. Specs on it are .600/.600, 218/227, 112+2 with -1* of overlap. That is a good match for your 6.0 swap and goals.
That 8720R1 would be a great fit here. It will be easy to get along with for daily driving duties. Then when you want to hook it up to a trailer you'll have some extra grunt to get up and moving. It will have an excellent mid-range and good top-end out to 6,500+ with .600" lift beehives. We have the Trickflow by PAC TFS-16918-16 beehives to pair with this cam. You can use a stock converter with the 8720R1. It's the largest truck cam we offer for use with a stock torque converter. A 2,500+ RPM stall converter would be a plus but not at all required.
Some upgraded pushrods will be needed. At .600" lift we typically see a 7.400" or 7.425" pushrod work. Things can vary so we always recommend measuring for pushrod length before purchasing pushrods. If you wanted to check for pushrod length and don't already have a pushrod length checker we offer the Trick Flow TFS-9501. When it comes time for purchasing pushrods we recommend a minimum of a 5/16" Chromoly pushrod with a .080" wall. You can typically find a set of 16 for around $100. From there you can get into thicker wall and or larger diameter pushrods.
We know our customers like combos. We put together different combos for our Pro LS cam lineup. For all available 8720R1 combos check here.
If you wanted something a little smaller and even easier to get along with we have the Truck stage 1 high-lift. That's part number SUM-8719R1 with specs of .550/.550, 209/217, 112+1 with -10* of overlap. It's on the small side of what we'd typically recommend for a 6.0. However, if you're budget-minded and tow often this might be one to look into. It moves the powerband down a bit with its 36* Intake valve closing vs. 39* of the 8720. This will help with off-idle torque but give up some power to the 8720 in the mid-range and top-end. At .550" lift, you can use our budget-friendly LS6-style springs. It's perfectly happy with a stock stall converter.
Regarding octane and compression. If someone is running 87 octane and towing, 10:1 is a pretty safe number. 10.5:1 on better gas is fairly safe. These are general numbers from what we've seen. Things can vary. A tuner can make up for lower compression with timing, but it’s not a good idea to constantly pull timing if static is too high.
This gives you some things to ponder and think about. We're here to help. Let us know if we can be of any further assistance!
We agree with 68Formula and kfxguy. It looks like you mixed up the cam info. The SUM-8707R1 you provided specs of is our stage 2 automotive "car" cam. That wouldn't be a good match for your combo and goals. It would be better suited for a 5.7 or 6.0 in something like a 4th gen F-body. The SUM-8720R1 is the stage 2 truck high-lift cam. Specs on it are .600/.600, 218/227, 112+2 with -1* of overlap. That is a good match for your 6.0 swap and goals.
That 8720R1 would be a great fit here. It will be easy to get along with for daily driving duties. Then when you want to hook it up to a trailer you'll have some extra grunt to get up and moving. It will have an excellent mid-range and good top-end out to 6,500+ with .600" lift beehives. We have the Trickflow by PAC TFS-16918-16 beehives to pair with this cam. You can use a stock converter with the 8720R1. It's the largest truck cam we offer for use with a stock torque converter. A 2,500+ RPM stall converter would be a plus but not at all required.
Some upgraded pushrods will be needed. At .600" lift we typically see a 7.400" or 7.425" pushrod work. Things can vary so we always recommend measuring for pushrod length before purchasing pushrods. If you wanted to check for pushrod length and don't already have a pushrod length checker we offer the Trick Flow TFS-9501. When it comes time for purchasing pushrods we recommend a minimum of a 5/16" Chromoly pushrod with a .080" wall. You can typically find a set of 16 for around $100. From there you can get into thicker wall and or larger diameter pushrods.
We know our customers like combos. We put together different combos for our Pro LS cam lineup. For all available 8720R1 combos check here.
If you wanted something a little smaller and even easier to get along with we have the Truck stage 1 high-lift. That's part number SUM-8719R1 with specs of .550/.550, 209/217, 112+1 with -10* of overlap. It's on the small side of what we'd typically recommend for a 6.0. However, if you're budget-minded and tow often this might be one to look into. It moves the powerband down a bit with its 36* Intake valve closing vs. 39* of the 8720. This will help with off-idle torque but give up some power to the 8720 in the mid-range and top-end. At .550" lift, you can use our budget-friendly LS6-style springs. It's perfectly happy with a stock stall converter.
Regarding octane and compression. If someone is running 87 octane and towing, 10:1 is a pretty safe number. 10.5:1 on better gas is fairly safe. These are general numbers from what we've seen. Things can vary. A tuner can make up for lower compression with timing, but it’s not a good idea to constantly pull timing if static is too high.
This gives you some things to ponder and think about. We're here to help. Let us know if we can be of any further assistance!
