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Re: Minimum/maximum quench [Re: Interceptor72] #2180927
10/23/16 05:38 PM
10/23/16 05:38 PM
Joined: Jun 2016
Posts: 76
Florida
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Interceptor72 Offline OP
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Interceptor72  Offline OP
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Florida
Well, I measured a third time and was very meticulous about WHERE I measured on the piston (as close to the center of the piston I could get) and getting EXACTLY on TDC (not just within 1degree or so) and everything I could think of and here are my final numbers:

#1= 0.011
#3= 0.012
#5= 0.013
#7= 0.015

#2= 0.012
#4= 0.011
#6= 0.010
#8= 0.008

I'm starting think this might be mostly the decks not being square, in combination with one slightly short and one slightly long rod.
If, for example, the rod in the 0.008 hole was just .001 longer than all the rest, then swapping it with the #7 hole would give me #s that look just like uneven decks.

I should have just instructed the machinist to zero deck it no matter what, so I guess that's my bad...

Re: Minimum/maximum quench [Re: Interceptor72] #2180983
10/23/16 08:00 PM
10/23/16 08:00 PM
Joined: Aug 2011
Posts: 2,842
Pattison Texas
CSK Offline
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Pattison Texas
as was said earlier you need to rock the piston to raise the quench area of piston & measure at the edge of piston to get the clearance # s
see my picture, mine is + 16.




Last edited by csk; 10/23/16 10:39 PM.

1968 Charger COLD A/C Hilborn EFI
512ci 9.7 compression, Stealth heads, 4.10 gear A518 ODtrans 4100lb,10.93 full street car trim
2020 T/A 392 Stock 11.79 @ 114.5

Re: Minimum/maximum quench [Re: Interceptor72] #2180995
10/23/16 08:21 PM
10/23/16 08:21 PM
Joined: Jan 2003
Posts: 30,945
Oregon
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AndyF Offline
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Oregon
The way to know for sure is to take one rod & piston assembly and put it in all four corners and use it to measure the deck height.

My guess is that your decks are sloped a little bit. Looks like one side slops up a little bit and the other slopes down. Or it could just be random error in rod length. Depending on the brand they'll vary that much.

Probably doesn't matter much for what you're doing. Put some 0.030 Cometic gaskets on there and get it running.

Re: Minimum/maximum quench [Re: AndyF] #2181102
10/23/16 10:42 PM
10/23/16 10:42 PM
Joined: Jan 2003
Posts: 1,020
Andrews,In. U.S.of A.
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67_Satellite Offline
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Andrews,In. U.S.of A.
In the 470 I am building, the pass side deck was even end to end and the driver side was out .020" front to rear. Machining at the factory in 1975 was lousy. Interceptor72 you have a p.m.

Re: Minimum/maximum quench [Re: Interceptor72] #2181109
10/23/16 10:53 PM
10/23/16 10:53 PM
Joined: Aug 2003
Posts: 43,007
Bend,OR USA
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Cab_Burge Offline
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Are you checking the deck heights in the center of the pistons or on the cam and outside block edges? Are you rocking the pistons in the bores and averaging the differences to get your readings?
Lots of variables in the ways to get those measurements work I use a thin bladed screwdriver to move the pistons in the bores, front to back and left to right and then average for the centers scope I used the highest readings on the piston tops to the head contact distances to set that clearance, better to be safe than sorry up

Last edited by Cab_Burge; 10/23/16 10:54 PM.

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Minimum/maximum quench [Re: Interceptor72] #2181113
10/23/16 10:57 PM
10/23/16 10:57 PM
Joined: Aug 2003
Posts: 1,573
K
KOS Offline
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Originally Posted By Interceptor72
Originally Posted By AndyF
Are you using aluminum heads? If so then you want the Cometic gaskets anyway.


Yes, aluminum heads.
To be honest, i've used steel shims with aluminum heads (even though they say not to) and never had a problem.
But steel shims are out of the question now anyway, since they will put me under .030. In the past I've always used them to get my compression up on stock blocks.
I have a pair of the MOPAR shim gaskets and they are actually 0.017...I wonder how much the copper spray adds to the thickness? wink


you can glue two of them together for a thickness of .034 i did it back in the day before cometics where avialable kept blowing felpros glued 2 steel shims together and never had a problem after and this was with 14.1compression

Re: Minimum/maximum quench [Re: Interceptor72] #2181344
10/24/16 12:34 PM
10/24/16 12:34 PM
Joined: Jan 2007
Posts: 8,027
Mt Morris Michigan
mopar dave Offline
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Posts: 8,027
Mt Morris Michigan
contact FBO/4secondsflat for your cometic gaskets, $165/pair.

Re: Minimum/maximum quench [Re: Interceptor72] #2181453
10/24/16 02:44 PM
10/24/16 02:44 PM
Joined: Jan 2003
Posts: 74,904
U.S.S.A.
JohnRR Offline
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Originally Posted By Interceptor72
Well, I measured a third time and was very meticulous about WHERE I measured on the piston (as close to the center of the piston I could get) and getting EXACTLY on TDC (not just within 1degree or so) and everything I could think of and here are my final numbers:

#1= 0.011
#3= 0.012
#5= 0.013
#7= 0.015

#2= 0.012
#4= 0.011
#6= 0.010
#8= 0.008

I'm starting think this might be mostly the decks not being square, in combination with one slightly short and one slightly long rod.
If, for example, the rod in the 0.008 hole was just .001 longer than all the rest, then swapping it with the #7 hole would give me #s that look just like uneven decks.

I should have just instructed the machinist to zero deck it no matter what, so I guess that's my bad...


The numbers indicate the decks are not square and one side is slightly higher than the other . go back and have it fixed . do it now while the engine is still a shortblock.


running up my post count some more .
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