3500 forged pistons options

[39bird230]

Hi,

After talking with my engine builder, it seem the 305 piston are gona have the wrong compression height compared to the stock pistons. Are they any other options?

I planned on putting a turbo this engine and it spend most of its time on the street and would like forged rods and pistons.

Would I be better off goin to a 3900 ?I would have to find cam spacer but I know others have used ls1 pistons and sbc rods and off set ground the crank to make it all work.

Thanks


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[koolcamaro]

Interesting, I didn't know there would be any v8 pistons out there that could replace ours. I thought WOT-tech sold some, but all I could find was Diamond piston options for the 3.4 and 3400. You could always go custom which requires you to mail in a piston, but it won't be cheap.

I saw a video where Mars ran 10's with a turbo 3900 in a third gen I believe. I wasn't able to find it again, but the video is somewhere on the youtube.

[Guest]

Custom is the only option for the LX9. They are probably not as expensive as you think, especially when you factor in custom machining to fit the conglomeration of parts that would yield less than desirable rod ratios and parts fitment in the end. Typically a custom piston is usually around $125 per hole, and they will fit exactly to your specs. Price out the machining required to fit an off the shelf piston to your engine and you will see that a custom piston will in many cases be cheaper.

As far as I'm concerned the only good option for even the LZx engines is custom piston as well. Too many compromises in using the LS1/6 pistons that require custom rods from what I've seen one other person do, along with needing to add proper valve reliefs in the pistons that no LS1/6 piston will have to match the valve arrangement of the LZx head.

That being said, how much boost do you plan to run? How are you REALLY going to drive it? You may find that a stock piston will do you very well. I ran upwards of 12 PSIG on my LX9, and eventually had a piston fail, but it seems to be from other factors, not a weak piston, like the fact that I had an ignition module fail in such a way that it caused the engine to stop VERY abruptly which I believe caused a piston to fracture added to that are the numerous times I would wring the engine out to 6500+ RPM with very little load due to lack of traction (I knew better, but did it anyway), which can cause undue stress on pistons and rods.

Looking at the LZ9, Mars has been running 15+ PSIG on his stock bottom end LZ9 abusing it at the race track with many 11 and 10 second passes, which come out to around 550 HP or so on those stock parts.

FWIW, I'm putting another LX9 together with oil squirters on all 6 pistons not just 5 and 6, and getting custom pistons for my LZ9 that will eventually go in the car when I pull the LX9 out to go into yet another project... Too many projects not enough space or time to get them all done.

[39bird230]

I'd like to race it to wheather it on the auto x or drag strip and I'd like to avoid what happened to you. I'm gona run low boost while i figure out how to tune efi. Then turn it slowly to 10 plus psi.

I also question the rod strength. I have found that do make 3.8 h beam rods that ate very close to the factory rods. Specs are 5.967 long with a 2.249 journal diameter and a 0.940 pin diameter. I think these could work since it seems Ill have to get a custom piston made anyhow.

I have seen what Mars has done and it is very impressive. His build helped inspire me to do a turbo v6 in an f body. I just want the extra reliability of forged parts.

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[Guest]

you state 3500 so I am assuming lx9 engine. There are others that have done forged pistons for a 3500 they might be able to give you the manufacturer and build number so the pistons could be reproduced.

if you insist on forged pistons, JE makes an off the shelf forged piston(part number 321238 ) that gives roughly a 10.8:1 compression ratio, has a 21cc dish and fits the stock rod. It fits the stock rod of the 3900 though so you would have to swap to the 3900.

if you did, you technically don't need to use the bearing spacers, you can run a stock cam, but you need to also run the factory timing chain cover if you did. if you need a set of cam spacers for a 3900 I can machine some up for you.

if you plan to only throw 10 psi at it, you probably don't need forged rods or pistons. thats just my opinion though. I am currently running a stock bottom end 3.5 lx9 on 10-12 psi now. I have a 3900 ready to go in if the lx9 pops.

[39bird230]

you state 3500 so I am assuming lx9 engine. There are others that have done forged pistons for a 3500 they might be able to give you the manufacturer and build number so the pistons could be reproduced.

if you insist on forged pistons, JE makes an off the shelf forged piston(part number 321238 ) that gives roughly a 10.8:1 compression ratio, has a 21cc dish and fits the stock rod. It fits the stock rod of the 3900 though so you would have to swap to the 3900.

if you did, you technically don't need to use the bearing spacers, you can run a stock cam, but you need to also run the factory timing chain cover if you did. if you need a set of cam spacers for a 3900 I can machine some up for you.

if you plan to only throw 10 psi at it, you probably don't need forged rods or pistons. thats just my opinion though. I am currently running a stock bottom end 3.5 lx9 on 10-12 psi now. I have a 3900 ready to go in if the lx9 pops.

It is an lx9 I believe out a 05 malibu. Do you use meth injection?

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[Guest]

I do not use meth and feel on an engine running such low boost numbers it is not necessary. If you do eventually turbo the engine and run 5-10 lbs or whatever around there, meth would be a waste of money for you.

I am running E85 because it is available in my area, although I have run 93 octane with it as well and it was fine.