LS2 bottom end for boost?
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LS2 bottom end for boost?
Hey everyone, I dont post here much but I recently bought an LS2 that im going to throw some boost at and use in a swap. Im looking for recommendations and input on the parts i was planning to use, and where better to ask then a corvette forum?
First of all, the goal is to get it setup for a reliable 10+ psi while remaining streetable. Boost will be provided by a Procharger D1 headunit. Heads are stock 243 with new springs. RPMs are planned to be kept within 6-6500 for drag racing, but i really dont see that being much over 6k.
Parts List
Crank - Stock crank
Rods - Eagle CRS6125O3D H-beam 4340 rods with 8740 rodbolds (390$)
Pistons - Diamond 11517 (This is a 4.030 bore piston, how do people feel about that on an LS2 aluminum block?) (653$)
Rings - Not sure what to go with here? (maybe the JE piston rings?)
Bearings - Clevite H series throughout
Main bolts - Either reuse stock or buy some arp?
Those pistons would have me at around a 9.77:1 compression ratio with the ls9 head gaskets. Is that way to high, or manageable for street use?
Any advice would be greatly appreciated guys.
First of all, the goal is to get it setup for a reliable 10+ psi while remaining streetable. Boost will be provided by a Procharger D1 headunit. Heads are stock 243 with new springs. RPMs are planned to be kept within 6-6500 for drag racing, but i really dont see that being much over 6k.
Parts List
Crank - Stock crank
Rods - Eagle CRS6125O3D H-beam 4340 rods with 8740 rodbolds (390$)
Pistons - Diamond 11517 (This is a 4.030 bore piston, how do people feel about that on an LS2 aluminum block?) (653$)
Rings - Not sure what to go with here? (maybe the JE piston rings?)
Bearings - Clevite H series throughout
Main bolts - Either reuse stock or buy some arp?
Those pistons would have me at around a 9.77:1 compression ratio with the ls9 head gaskets. Is that way to high, or manageable for street use?
Any advice would be greatly appreciated guys.
Le Mans Master
Joined: Dec 2005
Posts: 6,999
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From: Southeast TX
Your parts list looks fine. Use whatever ring set the piston mfg recommends for your intended use. I'd use ARP head and main studs. Unless you're going way over 10psi, keep the compression ratio in the 10.5 to 11 range. You'll like it a whole lot more on the street. Pass a few fuel stops too. There's a bunch of stock short block LS2 &3's living well on boost in excess of what you're planning. Have a pro spec you a good cam.
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Thanks for the input guys. I guess the plan for boost would be between 10-15psi, im not sure the D1 will make much more than that.
Any suggestions on pistons? I cant seem to find jack that has any kind of a dish, 2618, and smaller than 4.030 but bigger than 4.000, for a stock crank, seems to be a lot available for a 4 inch stroke?
Edit: The Wiseco K444x05 seem like they could work? Stock stroke/rod length, 4.005 bore with an 11cc dish would make for a 10:1 compression ratio using LS9 gaskets and a -0.010 deck height (Is that fairly standard for the ls2?). Depending if i have to have the heads/deck milled at all, that would give me a bit of room to bump the compression up a bit.
Edit2: Wiseco K0045X05 also? A bit smaller dish, and use a bigger wrist pin?
Note: I live on the west coast of canada, our gas isnt nearly as good as that in the states. Even out '94' octane is probably comparable to US 89 or so.
Any suggestions on pistons? I cant seem to find jack that has any kind of a dish, 2618, and smaller than 4.030 but bigger than 4.000, for a stock crank, seems to be a lot available for a 4 inch stroke?
Edit: The Wiseco K444x05 seem like they could work? Stock stroke/rod length, 4.005 bore with an 11cc dish would make for a 10:1 compression ratio using LS9 gaskets and a -0.010 deck height (Is that fairly standard for the ls2?). Depending if i have to have the heads/deck milled at all, that would give me a bit of room to bump the compression up a bit.
Edit2: Wiseco K0045X05 also? A bit smaller dish, and use a bigger wrist pin?
Note: I live on the west coast of canada, our gas isnt nearly as good as that in the states. Even out '94' octane is probably comparable to US 89 or so.
Last edited by BigBadWhitey; Jun 18, 2013 at 05:32 PM.
Le Mans Master
Joined: Dec 2005
Posts: 6,999
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From: Southeast TX
Talk to your machine shop about the pistons. You really can't order them now. They will more than likely not want to get the pistons ordered until they see what it takes to clean up your cylinder bores. Like jon6 mentioned, less material removed is better.
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Ok so i did some measuring on my block to see what the bores were at.
I measured them in 2 directions (12-6 and 3-9 if you were facing the front of the block) and nearly every cylinder seemed to measure 3.999 or 3.998 in each direction. I was using a dial bore gauge and a micrometer, and the blocks temperature measured 69*F.
Does that seem strange? Im assuming it came in under 4 inches due to calibration in the tools used, or has anyone else experienced that? I guess my main concern was that one was more out of round than the others, but they all had a fairly tight spread.
Also talked with my machine shop, they said they were good going with up to 30 thousandths over as a last resort, and said i would be fine to buy an off the shelf piston (i guess based on my measurements anything from 4.005 to maybe 4.020 is going to be ok)
How firm does everyone believe in the 10:1 being a good compression ratio, and why so comfortable at this high of one? Every where I read on any other motor (ls1,lt1, ect) 9:1 and 9.5:1 seem to be the bounds people like. Is that old school logic, or is there something im missing as to why the ls2 is ok at a higher compression ratio.
I measured them in 2 directions (12-6 and 3-9 if you were facing the front of the block) and nearly every cylinder seemed to measure 3.999 or 3.998 in each direction. I was using a dial bore gauge and a micrometer, and the blocks temperature measured 69*F.
Does that seem strange? Im assuming it came in under 4 inches due to calibration in the tools used, or has anyone else experienced that? I guess my main concern was that one was more out of round than the others, but they all had a fairly tight spread.
Also talked with my machine shop, they said they were good going with up to 30 thousandths over as a last resort, and said i would be fine to buy an off the shelf piston (i guess based on my measurements anything from 4.005 to maybe 4.020 is going to be ok)
How firm does everyone believe in the 10:1 being a good compression ratio, and why so comfortable at this high of one? Every where I read on any other motor (ls1,lt1, ect) 9:1 and 9.5:1 seem to be the bounds people like. Is that old school logic, or is there something im missing as to why the ls2 is ok at a higher compression ratio.
Burning Brakes
Joined: Jan 2012
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From: Alameda Ca
I have a forged bottom end LS2, stock crank.
Untouched 243 heads
untouched LS2 intake
ECS baby cam (which is for sale right now)
Novi 2200SL (ECS setup)@14.9psi
My compression was at 10.1
My car made 745 to the wheel on 91 octane pumpgas (I live in California, best we get at the pump)
Untouched 243 heads
untouched LS2 intake
ECS baby cam (which is for sale right now)
Novi 2200SL (ECS setup)@14.9psi
My compression was at 10.1
My car made 745 to the wheel on 91 octane pumpgas (I live in California, best we get at the pump)
Le Mans Master
Joined: Dec 2007
Posts: 8,375
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From: Somewhere in the Mid 9's TX
Personally, with a built motor, I'd push it a little more. Maybe an F1a, or raise your compression to around 10.5:1. I don't see a sub 10:1 compression motor with the stock stroke being much fun on 10psi with a centri. Maybe a twin screw or TT car.
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I have a forged bottom end LS2, stock crank.
Untouched 243 heads
untouched LS2 intake
ECS baby cam (which is for sale right now)
Novi 2200SL (ECS setup)@14.9psi
My compression was at 10.1
My car made 745 to the wheel on 91 octane pumpgas (I live in California, best we get at the pump)
Untouched 243 heads
untouched LS2 intake
ECS baby cam (which is for sale right now)
Novi 2200SL (ECS setup)@14.9psi
My compression was at 10.1
My car made 745 to the wheel on 91 octane pumpgas (I live in California, best we get at the pump)
I found someone with some Callies H-beam rods i think im going to buy for a good deal, so that should be good as well.
Your 91 will be similar to the 94 we get here, if not better.
Ill be sticking with the D1 for a while, unless i can find a good deal on an F1 of sorts locally. Also tuning shops out here arent too abundant, im worried that 10-10.5:1 is going to set me up to high for detonation sake if i cant get a spot on tune, less room for error?
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I found a 4 inch crank locally, but i guess whoever installed the pin last didnt do a pretty job of it. How would anyone go about fixing this? Is there maybe a larger pin I can use, drill out the old and put in the new? Or is there a reasonable way of fixing this?
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That was the plan, but what do i do with the current pin?
Le Mans Master
Joined: Dec 2005
Posts: 6,999
Likes: 1,685
From: Southeast TX
[QUOTE=BigBadWhitey;1584318256
That was the plan, but what do i do with the current pin?[/QUOTE]
Not sure what you mean, but just ignore the slot that was cut in the previous pinning process. It won't affect doing it right this time.
That was the plan, but what do i do with the current pin?[/QUOTE]
Not sure what you mean, but just ignore the slot that was cut in the previous pinning process. It won't affect doing it right this time.
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So if the old pin is just yanked out, i wont have to have the hole filled or anything of the sorts? Thats my issue
A local machine shop could probably have it ground down to round, but i figure that will probably undersize the snout which wouldnt be good. Youd feel safe just removing the old one and having the slot remain empty as long as it was repinned?
A local machine shop could probably have it ground down to round, but i figure that will probably undersize the snout which wouldnt be good. Youd feel safe just removing the old one and having the slot remain empty as long as it was repinned?
Le Mans Master
Joined: Dec 2005
Posts: 6,999
Likes: 1,685
From: Southeast TX
So if the old pin is just yanked out, i wont have to have the hole filled or anything of the sorts? Thats my issue
A local machine shop could probably have it ground down to round, but i figure that will probably undersize the snout which wouldnt be good. Youd feel safe just removing the old one and having the slot remain empty as long as it was repinned?
A local machine shop could probably have it ground down to round, but i figure that will probably undersize the snout which wouldnt be good. Youd feel safe just removing the old one and having the slot remain empty as long as it was repinned?
Last edited by old motorhead; Jul 3, 2013 at 11:08 PM.