Turbocharging bored out engines. Problem?

[PanzerAce]

I seem to recall a couple of posts claiming that L engines that have been bored out don't take to boost well. Anyone know where I could read up on why this is true, or if it even is? (My search foo sucks, aparently)

[Clifton]

How much boost? 10 psi or 30 psi. Big difference. I know 1 fast Z sonic tests his to bore the max. He could answer, oh wait he's banned. maybe some one else has FIRST HAND experience boring to the limit with turbo and high boost?

[JSM]

Maybe w/Flat top pistons, but dished why would there be a problem? As long as the boring isn't took extensive to weeken the cylinder walls.

[PanzerAce]

How much boost? 10 psi or 30 psi. Big difference. I know 1 fast Z sonic tests his to bore the max. He could answer, oh wait he's banned. maybe some one else has FIRST HAND experience boring to the limit with turbo and high boost?

 

I will be/am running 91 octane, and it's my DD, so I think I won't be running any funny jungle juice to push the psi WAY up there, at MOST I'll be doing methanol/water injection.

 

Wait, why is he banned?

 

Maybe w/Flat top pistons, but dished why would there be a problem? As long as the boring isn't took extensive to weeken the cylinder walls.

 

Beyond the CR, is there a reason for dished over flat? The issue is I've seen some people saying that basically any boring of the cylinder beyond a simple re-machining of the surface will be to much to handle boost.

[sticky280zx]

its better to have dished pistons with the same cr than flat because of the burn surface.....quenched surface is better than flat....iirc

[1 fast z]

Yes I was on a 7 Week "vacation", but we wont be talking about that here.

 

 

 

Yes I sonic test all of my L series blocks. First of all which block are you using. If you are using a F54 block, then dont bore, as they are way thinner than a N42 block.

 

I offset bore my blocks as well, for the increased bore size. I gain about .040" of clyinder wall thickness by compensating for the core shift. F54's are a non siameesed block, and between cylinders 2-3 4-5 5-6 are not tied toghether, and therefore a much weaker block, and the clylinder wall thickness is not as thick either as the N42.

[PanzerAce]

guess I'll have to go wipe the grime off the side of the engine then, since all I can see on the block number is a 4, which doesn't help.

 

So basically, if it is an F54 block, then swapping my E88 for a P90 and turbo would be a bad idea, period, but if it is a N42, it is ok to do?

[1 fast z]

An N42 block is much stronger, and a 75-76 block is a high nickel content. You can almost hear the difference by tapping each block with a ball pein hammer.

 

ALL of my big bore builds use N42 blocks. I guess before I ever sonic tested L6 blocks, I thought like everyone else, and thought the F54 was the "siameesed block".

[PanzerAce]

Cool, thanks for the info. Time to clean up the engine bay and get my google-fu up to speed to check engine serial number vs. production time. (in this case, nickel is good, right?)

[col]

1 fast z , What was the max size you bored to by offseting the bores?

And did the offset have any effect on the engine, I suppose the gudgin pin has plenty of sideways movement, but still if pushed 20''' to one side it might push a bit sideways on the piston.

Thanks Col

[1 fast z]

Have you ever looked at alot of V8 engines, as far as wrist pin to connecting rod location goes? ALOT of them are not centered. Think about the forces involved, no .020" is not going to effect any pre-mature piston, rod, bearing or ring wear. My dad has been building monstor motors with this thinking for over 40 years, and my grandfather longer than that (I come from line of engine builders ).

 

 

I run 89mm bores, I can go larger, but you dont want any thinner than .090" cylinder bores in a NA motor, and can be up to .070" in SMALL spots, as the cores are not smooth on the inside anymore, after all, people do have not run antifreeze for how ever many years. On a boosted engine, I try to keep cylinder wall thickness at .125" and down to .110" in small spots.