Quote:
Originally Posted by LM93
If the pistons were a unique design, could pistons from a different engine with the same dimensions be made to work? Those Jeep I6 ones have close numbers and are forged.
Forged rods for the Chevy 250 are available in 5.700" and 6.000." I'm sure I saw on SpeedTalk.com a comparison of the Pontiac and Chevy rods. They were the same length but the Pontiac's were much beefier. Can't find it right now. Are the crank journals for the rods the same for the Chevy and Pontiac?
A new cam would be cut from a blank, right? Would the new cam be too hard a metal for the original followers? I wonder if roller followers could adapted or specially made. Would probably need to order more than just one set if so.
https://www.ebay.com/itm/142992244403
I messaged the seller of these to see what info I could get about them. I'll follow up if I get a response.
The short stroke like you say is good for turbocharging. Shorter stroke=higher redline. More rpms=more boost. The valvetrain has to live at that speed, though.
About compression, rule of thumb for V8s is 9.5:1 for N/A, 8.0:1 for boost on pump gas. But it's cylinder pressure under load that really determines preignition threshold. Are the combustion chambers on the I6 similar to the V8s? If they are, wouldn't they have the same cranking pressure tolerance? I've read that 160psi is the limit for iron heads. Wouldn't you need a considerable piston dish to run 25lbs of boost and not blow your engine?
https://forums.maxperformanceinc.com...d.php?t=852412. Asked about block strength in the boost section. Mr. Jack Gifford said he was told by Mickey Thompson's crew chief that the OHC heads would crack between the valves when they tried to run them. Races push their engines to the absolute limit, so I wonder how hard their engines went before failure.
So many unknowns, so many new things to learn! |
Being you do have a lot of unknowns regarding this engine being boosted which is leaving you with a lot of questions that you're asking, you're going to get a lot of opinions from most that never did it and are just speculating . With that said its not going to be first hand information from someone who has done it before. So all you can do is make a list of what you're going to need and see how much of it is available . From there you will decide if you want to take the chance.
I've been there before. I wouldn't worry about the head cracking . To me that was back in the 60's when things were different . Technology has come along way since then . Im not saying that it still wouldn't happen. Just that you have a good chance that it wont. I was told that if i put 15 psi to my 4cyl it would explode . Well ive been as high as 44psi now and i'm still going for more . That's all i heard when i was building that engine and i,m glad i didn't listen because i run 22 psi on a daily bases and when i race with the faster guys its set higher like 35 to 40 psi.. No matter what engine you build it can come apart.
So the way i see it, you can call and have parts made and spend a lot of money or just get a motor re-gap the rings and put it in the car with a turbo and tune it to see how it holds up . That would be what i would do.. Because now you have real world information that tells you if its worth spending money on good parts.