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slantzilla
PostPosted: Wed Jan 05, 2022 9:25 pm 
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With a 3.500" bore, flat top pistons -.010" down, a gasket compressed .039" and a 56 cc chamber what would I be at for CR?

Thanks! :mrgreen:

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emsvitil
PostPosted: Wed Jan 05, 2022 11:42 pm 
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http://www.wallaceracing.com/cr_test2.php

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Killer6
PostPosted: Thu Jan 06, 2022 12:27 am 
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slantzilla wrote:
With a 3.500" bore, flat top pistons -.010" down, a gasket compressed .039" and a 56 cc chamber what would I be at for CR?

Thanks! :mrgreen:

Actual stroke please....
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Rick Covalt
PostPosted: Thu Jan 06, 2022 3:08 am 
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If I looked at it right, and using a 3.66" big bore gasket, it came out to 11.1 CR. Please double check my numbers! :D

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hyper_pak
PostPosted: Thu Jan 06, 2022 6:51 am 
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Dart270
PostPosted: Thu Jan 06, 2022 7:24 am 
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I get 11.2:1 with that gasket thickness and assuming stock 4.125" stroke.

Lou

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slantzilla
PostPosted: Thu Jan 06, 2022 12:31 pm 
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Thanks everyone! Yes, stock stroke.

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Killer6
PostPosted: Thu Jan 06, 2022 3:59 pm 
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I get 11.2:1 w/a 3.55" gasket bore.
Edited; fat fingered gasket thickness.


Last edited by Killer6 on Fri Jan 07, 2022 8:25 am, edited 1 time in total.

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Killer6
PostPosted: Thu Jan 06, 2022 4:23 pm 
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hyper_pak wrote:
One Million To One!

:shock: I need You to manage a Roth IRA for Me, if Ya ain't busy, lol!
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Doctor Dodge
PostPosted: Thu Jan 06, 2022 7:19 pm 
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I also came up with 11.2 to 1 CR
Get a big cam with the intake valve closing around 75* ABDC and you get 8.17 effective compression.
DD
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GregCon
PostPosted: Thu Jan 06, 2022 7:32 pm 
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It won't make a huge difference, but you really need the compressed volume of the gasket. Most of the better gaskets have that printed on the packaging.
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Dart270
PostPosted: Fri Jan 07, 2022 5:17 am 
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I always measure my compressed thickness with head torqued on motor with feeler gauges. Felpro is 0.034, ACL is 0.046, Permaseal is 0.047. These are all pretty close to +/-0.001" measurement error and I have seen variations of +/-0.002".

Lou

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Greg Ondayko
PostPosted: Fri Jan 07, 2022 7:00 am 
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GregCon wrote:
It won't make a huge difference, but you really need the compressed volume of the gasket. Most of the better gaskets have that printed on the packaging.



I doubt many if any of the gasket suppliers for the Slant 6 engine (except for maybe the MLS Group buy) have the compressed thickness advertised...
Greg

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Killer6
PostPosted: Fri Jan 07, 2022 9:00 am 
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Dart270 wrote:
I always measure my compressed thickness with head torqued on motor with feeler gauges. Felpro is 0.034, ACL is 0.046, Permaseal is 0.047. These are all pretty close to +/-0.001" measurement error and I have seen variations of +/-0.002".

Lou


If You're actually cc'ing everything, that's the best way to get as close to perfect as possible. Using dimensional calc. methods, the uninstalled-previously compressed dim. offsets to some extent the volume unaccounted for in the upper piston to bore gap above the ring.
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kesteb
PostPosted: Fri Jan 07, 2022 2:44 pm 
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Interesting video from the "Riding with Alex Taylor" youtube channel that raising the compression may not be a all that desirable. As it limits the "tuning window". Especially if using power enhancers.

https://www.youtube.com/watch?v=jGHxF_5xvJE

But then they are playing in a difference league then we are.
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