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I need some GM guru's to help me figure this out. I've been trying to build a budget minded LS1 Iron block.
I've got an 03 5.3l block that I sent to the machine shop to be bored over to LS1 spec.
I already have the LS1 pistons from a corvette with new rings. Problem is the machine shop over-bored my block to 3.905"....not 3.898"...
Now I'm sitting here with pistons I can't use...
I've got Gen IV rods purchased threw this site and now i'm looking for 3.905" pistons that match with the 6.098" length.
I'm unsure of the Pin Diameter on the Gen 4 rods. I know there free floating, but are they still .945" or the smaller .927"??
anybody have a link to a set of pistons that match for under $600?
Personally, I think that your best option for this particular set of circumstances is to get a set of JE forged pistons in 3.905" x 1.175" compression height (~$750), and some 6.25" forged eagle I-beams (~$250). Both of these are available through summit racing for about $1100+s/h. This gives you a higher rod ratio than most other combinations, which is really nice. And you end up with forged rods and pistons, versus stock rods and forged pistons.
I know you already have the genIV rods, but I am having an equally difficult time tracking down some forged slugs for the 3.905" bore and stock 6.098" rods. So my choice would be to go forged rods and pistons, and raise the rod ratio in the process. Really can't beat the price of those eagle I-beams. They may be Chinese steel, but at least it's forged and shot-peened Chinese steel. They've got to be better than oem powdered metal rods.
PS. I know you said ~$600, man, and I'm not trying to spend your money for you... But I couldn't find you an option for the price you listed. Sorry.
It sounds to me like this is your machine shop's problem, not yours. If they oversized your block for the pistons you intended to use, they need to fix the problem. Get on that ***! They should at the very least be able to get you a new set of pistons at their cost.
David, can't really go that route as I've already committed to the rods and there in route.
KCS, Those pistons might be the ticket. I don't see a listed PIN diameter on there website. If they are in fact .927" like the gen 4 rods. I'm in business. To be honest until I measure the rods or someone on here can confirm the pin diameter. I would make the purchase. But for the price. I'm just waiting on confirmation.
The machine shop I'm working with are crooks. But in my area, there all I got. two old dudes working out the shop behind there house.
Old dude#1: Well, you could bore it out to 4." and sleeve it to the right thickness.
Me: The LM7 won't go past 3.910" without hitting water...
Old dude#2: You could run a larger piston in that cylinder only..
Me: ...internally balanced engine....no I won't...
Old dude#1: Well,..I could probably use it on a build later on if your looking' to get rid of it...
Me: I'd sell it to you if I have another block to build off of..but I don't.
no i doubt it was sonic checked and even if he had the ability to do it. I wouldn't trust there findings.
SO, whats the harm in running pistons made for the 6.125 or 6.100" length rod on a 6.098"?
Are the pistons pin locations so different that they would promote Valve to piston issues?
First off, like I said earlier, stock pistons and rods use a .944" pin. THEY ARE NOT .927", that is aftermarket size.
Second, a piston pin bore will be about .945" so it has clearance with a .944" pin. The rods could be .945" as well in the Gen IV floating pin rods or .943" bore for the Gen III press fit rods.
Lastly, the JE piston PN I posted is for stock rods with the .944" pin. On JE's website, it has a note at the top that a K code comes with .944" pins and that PN has a K code. Keep in mind that they do not come with rings, those are extra. Don't assume the stock rings you have will work either. 3.898" bore rings will have a greater gap in a 3.905" bore by about .021".
Using a piston designed for a longer rod would make it too short for the stock rod. It would be down in the cylinder too far to make any compression.
To give you an example:
Zero deck on a 9.240" block would be a 3.62" stroke, 6.098" rod, and a 1.332" piston height. Bam, dead even with the block surface.
Same everything, except now you use a 1.305" piston, made for a 3.62" crank/6.125" rod combo, and you are .027" below deck. And that's too much to be ok with.
A 1.115" stroker piston would be a terrible .217" below the surface of the block.
First off, like I said earlier, stock pistons and rods use a .944" pin. THEY ARE NOT .927", that is aftermarket size.
Second, a piston pin bore will be about .945" so it has clearance with a .944" pin. The rods could be .945" as well in the Gen IV floating pin rods or .943" bore for the Gen III press fit rods.
Lastly, the JE piston PN I posted is for stock rods with the .944" pin. On JE's website, it has a note at the top that a K code comes with .944" pins and that PN has a K code. Keep in mind that they do not come with rings, those are extra. Don't assume the stock rings you have will work either. 3.898" bore rings will have a greater gap in a 3.905" bore by about .021".
Thanks for clearing that up. So Gen IV floating pin rods (Which is what the guy I bought them from calls them. they look to have bushings in them.) are .945"
I didn't mean to come off as putting words in your mouth. Just trying to measure twice cut once on this. I don't have them in yet, so I can measure.
Thanks for clearing that up. So Gen IV floating pin rods (Which is what the guy I bought them from calls them. they look to have bushings in them.) are .945"
I didn't mean to come off as putting words in your mouth. Just trying to measure twice cut once on this. I don't have them in yet, so I can measure.
No problem, just wanted to clear up some misinformation before moving on.
Yes, those bushed rods should be bigger than .943" in order to have clearance with the .943" pin. In the sets I've measured, they're usually only about .0005" bigger, which is tight for a performance engine IMO. I like to just bump them through the rod hone for about .001" clearance. The LS7 rods are the exception; they use a .925" pin but that's a whole different animal.
The machine shop I'm working with are crooks. But in my area, there all I got. two old dudes working out the shop behind there house.
Old dude#1: Well, you could bore it out to 4." and sleeve it to the right thickness.
Me: The LM7 won't go past 3.910" without hitting water...
Old dude#2: You could run a larger piston in that cylinder only..
Me: ...internally balanced engine....no I won't...
Old dude#1: Well,..I could probably use it on a build later on if your looking' to get rid of it...
Me: I'd sell it to you if I have another block to build off of..but I don't.
Your avatar says "Central Texas", there are plenty of shops out that way. I drove my junk 5 hrs from SETX to TSP on the north edge of Georgetown. You've gotta be closer than that...
I honesty didn't know TSP was in Georgetown. But I did email them before hand and asked if they would bore my block for me. They told me they only work on blocks if they're building a short block or long block for the customer. Not just a bore and hone job. I get that, got to make money somehow.
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