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8.2 mexican block 338ci turbo piston ring land question

General engine tech -- Drag Racing to Circle Track

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fomocosteve
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8.2 mexican block 338ci turbo piston ring land question

Post by fomocosteve »

Hi, I have a question, I have a set of 30cc dish pistons I can make work in a combo im wanting to turbo, can anyone tell me what their thoughts are of a .165 top ring land in a turbo application with forged pistons. I can make it an e85 dedicated build if required to make it live.... 338 cubes, 750 hp @ 6800-7000 rpm...... 8:1 compression, carrillo 1.85 rods,..... Bryant 3.25 crank......
Will it live if the rings are gapped correctly... even on E85.... Thoughts Please.....
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Re: 8.2 mexican block 338ci turbo piston ring land question

Post by LSP »

fomocosteve wrote: Thu Feb 13, 2020 11:50 am Hi, I have a question, I have a set of 30cc dish pistons I can make work in a combo im wanting to turbo, can anyone tell me what their thoughts are of a .165 top ring land in a turbo application with forged pistons. I can make it an e85 dedicated build if required to make it live.... 338 cubes, 750 hp @ 6800-7000 rpm...... 8:1 compression, carrillo 1.85 rods,..... Bryant 3.25 crank......
Will it live if the rings are gapped correctly... even on E85.... Thoughts Please.....
Steve
Find out how much cross-section is between the valve pockets and the top ring groove, that is more important in your case.
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Re: 8.2 mexican block 338ci turbo piston ring land question

Post by BILL-C »

Looks like you have a 4.065 bore in that 338 cid 302 mexican block. The pistons are a concern, but i would be more worried about the block at the 750 hp level. You might be wasting a real nice crank and set of rods. Check how thin piston is between inside of top ring groove and intake valve pocket . Piston might possibly be thin between id of ring groove and edge of dish also. I would call whoever made pistons and ask their opinion. I personally would be a little worried.
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Re: 8.2 mexican block 338ci turbo piston ring land question

Post by KnightEngines »

That block will bust open like a rotted tomato.
Don't even think about it!

Get an SHP block, then worry about pistons.
fomocosteve
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Re: 8.2 mexican block 338ci turbo piston ring land question

Post by fomocosteve »

I just took a stab at the cubic inch, theyre actually 4.056, and i was going to half grout the block ??? Just checked it at 335.9 cubes, cant rough guess anything around here without being called on it lol...
Last edited by fomocosteve on Thu Feb 13, 2020 8:46 pm, edited 1 time in total.
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Re: 8.2 mexican block 338ci turbo piston ring land question

Post by KnightEngines »

Grout won't help, the torque of a turbo motor will tear the mains out.

You NEED an aftermarket block.
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Re: 8.2 mexican block 338ci turbo piston ring land question

Post by fomocosteve »

Ok, thanks Knight, im hearing ya, what if i used em in a 351w block i have laying around, would the ring land still be a problem?
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Re: 8.2 mexican block 338ci turbo piston ring land question

Post by KnightEngines »

351w block will take it.

Ring lands will live on e85 if the tune is good.
But you don't have much margin for error in the tune, if it pings it'll break the lands.
Probably best to get some boost specific pistons - spend more up front & it'll be cheaper in the long run.
fomocosteve
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Re: 8.2 mexican block 338ci turbo piston ring land question

Post by fomocosteve »

Okay, thanks, Just seeing if they were usable, i think ill move em on, I dont have a use for them, what would you recommend as a minimum ring land thickness for boost while im shopping for pistons?
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Re: 8.2 mexican block 338ci turbo piston ring land question

Post by Mark O'Neal »

I'd recommend a .250 minimum BUT...... If the tuneup is right, it doesn't matter how I make the pistons. If the tuneup is wrong, it doesn't matter how I make the pistons.
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Re: 8.2 mexican block 338ci turbo piston ring land question

Post by KnightEngines »

Another point - your crank won't go into a 351w block.
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Re: 8.2 mexican block 338ci turbo piston ring land question

Post by fomocosteve »

Yeah, id have to use other crank for use with the 3" main. Thanks guys
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