Is a Mirror image -55cc piston practical?

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Feb 1, 2004 | 01:25 PM

99.9percenter

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From: Washington

Is a Mirror image -55cc piston practical?

It would be a JE,for a High boost LT1. Or is a swirl quench better?

Feb 1, 2004 | 10:02 PM

J 98ta

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From: mpls, mn

Quote:

Originally Posted by streetbad

It would be a JE,for a High boost LT1. Or is a swirl quench better?

-55cc ? Sounds like a real low compression ratio to me... What are the heads you are using ?

'J

Feb 2, 2004 | 12:15 PM

Eric Fischer

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From: NJ

Quote:

Originally Posted by streetbad

It would be a JE,for a High boost LT1. Or is a swirl quench better?

-55cc is huge, about the size of the combustion chamber. In any case, if you have custom pistons made, then they can make the dish as big as you want (within reason, probably the max would be about -20cc).

Feb 2, 2004 | 12:35 PM

10secondZ

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From: Lake mary, (Orlando) FL

OMG! with a stock size chamber that would be 7.1:1 compression...and anything bigger than stock would of course be more even less compression on an LT1....for compression that low you would need in excess of 30psi to take full advantage of that...I would use a -20cc max quench and get 9.0:1 wich would still be good for roughly 25psi or more and wouldnt be such a dog in low boost rpm ranges....but to answer your original question..use a max quench design for sure if you are dropping a dish that low.

Carter

Feb 2, 2004 | 03:05 PM

Nick Agostino

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From: ONTARIO/CANADA

Some times when the effective dome volume needs to be that low (-55cc) depending on the bore size and chamber shape the compression height is cut down a bit to minimize the amount of relief cut into the piston. If you have lots of compression height it shouldn't be a problem to get a set made( not knowing your combo ?). You may be able to help your situation by looking at gasket thickness and head cc before you finalize the piston design, your engine builder should be able to help with these things.

Feb 8, 2004 | 10:57 AM

99.9percenter

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From: Washington

Swirl Quench Or Mirror Image?

Quote:

Originally Posted by Nick Agostino

Combo Is LT1. Compression Height Is Very Negotiable as I Have not ordered Crank or Rods yet. It is VERY encouraging to think that -55cc pistons are doable as I have not seen or heared of this before. Would a Swirl Quench design be more effective than a mirror image? Or should I just order the Mirror Image? My Valves(stock size) have been unshrouded would this make a difference in how I order the Mirror image pistons?

Feb 8, 2004 | 07:08 PM

Nick Agostino

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From: ONTARIO/CANADA

Quote:

Originally Posted by streetbad

I appologise if I was a bit misleading but with a 4.030" bore I don't think -55cc dish is practicle. We have used as large as -35cc on a few lt1's and that was pushing it but worked fine. If you were to work the chambers of the heads to a reasonable size (AFR's can be cnc'd to 76cc from a stock 58cc) play with the head gasket thickness ( I am assuming you are using copper and o-rings with 30lbs of boost?) then effectively you have achived -55 but with a 30-35cc dish; this is what I meant.

I have funny feeling you are trying to buld a mid to large inch LT1 with alot of boost. If you are looking to use 7.0 comp. you prob. don't that big of an engine and the effective - volume will not be as low to give these compression numbers.

I really think you need to look at the complete engine/power adder package and go from there.

Hope this clears thingsup for you a bit