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 Post subject: Re: Head porting
PostPosted: Thu Feb 04, 2021 6:07 am 
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Supercharged

Joined: Wed Sep 17, 2008 6:48 pm
Posts: 3560
Location: Indianapolis
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Don, yes it is very important that the fire ring on the head gasket is fully supported. To do that and provide some relief around the valves, put a back cut in the combustion chamber wall at the height of the closed valve and extending up the combustion chamber wall .075 to .080 and you don’t need to make it deep. How high one can go depends upon how much the head has been shaved. If the head has not been cut you can go higher, just leave plenty of support for the fire ring. .030 thousands deep is enough to help low lift flow. Within reason, more can be better. Basically put a reverse taper on the combustion chamber wall where the wall is closest to the valve. As the valve opens the restriction from shrouding diminishes so generally, there is no need to relieve all the way to the fire ring land.

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 Post subject: Re: Head porting
PostPosted: Thu Feb 04, 2021 12:01 pm 
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Turbo EFI
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Joined: Wed Oct 12, 2005 9:00 pm
Posts: 2366
Location: kankakee IL
Car Model: 80 volare, 78 fury 2 dr, 85 D150
I have the old style fel pro that I have laid on the head as a template. Not the print o seal ones, I can't find specs on the old one, but I have fire ring bore specs on the printoseal style at more than 100-thou bigger than bore size. I have one of those coming to compare. I might be in trouble on this head if the printoseal is the same dia fire ring as the old style fel pro on 1 cylinder. I hadn't done much in the chambers yet, just touched a couple of them so far. I might have to call this head "practice" and start over with one of the others I have here. I didn't realize that the chamber size was already that close to the size of the fire ring. I have not yet but I definitely had planned to shave this head once I get my block together and see how deep in the hole my pistons will wind up. Looking at it the one cyl that I am worried about the relieving that I did does seem to taper so with a shave it might still be alright. Have to see.


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 Post subject: Re: Head porting
PostPosted: Thu Feb 04, 2021 3:25 pm 
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Supercharged

Joined: Wed Sep 17, 2008 6:48 pm
Posts: 3560
Location: Indianapolis
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If the newer Fel Pro head gasket does not have a larger fire ring diameter, there are slant six head gaskets that go much larger, I believe it is an Aussie head gasket,,, Lou or Dennis would know how to get them. I believe the compressed thickness is different, that will affect your compression ratio calculations, but a small price to pay to save a head that you have time in.

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 Post subject: Re: Head porting
PostPosted: Thu Feb 04, 2021 4:54 pm 
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Turbo EFI
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Joined: Wed Oct 12, 2005 9:00 pm
Posts: 2366
Location: kankakee IL
Car Model: 80 volare, 78 fury 2 dr, 85 D150
ok I found my dial caliper..... something I have only 1 of ///and use at home and at work....it slid under the seat in my truck.
. I'm curious what the fire ring diameter is on this old style Fel pro gasket, same PN as the Printoseal but suffix is SB instead of PT... I have a stack of these (7 or 8 ) NOS Fel Pro, silver backed style. and I do have 1 Mopar steel shim NOS slant head gasket..... I see old school Detroit, Mc Cord and ROL slant 6 head gaskets on Feebay, for "not bad" prices..... none of which I can find any tech info, like fire ring dia. or compressed thicknesses.....
my kid needs some other gaskets for his slant, he's not gonna go down to the head gasket/ but was cheaper for him to buy a complete set, than to piece together the few he actually needed..... so lets see what the new style Fel Pro looks like against this head once it gets here.....


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 Post subject: Re: Head porting
PostPosted: Fri Feb 05, 2021 5:25 am 
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Board Sponsor & Moderator
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Joined: Mon Oct 21, 2002 11:08 am
Posts: 15355
Location: Blacksburg, VA
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Felpro is quite close to 3.50". ACL gaskets around 3.55" but not sure if available. Best are Endurotec (aussie) that are 3.66" bore. Best for hi perf. Shipping not bad now. 0.046-0.048" compressed thickness.

Lou

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 Post subject: Re: Head porting
PostPosted: Fri Feb 05, 2021 10:00 am 
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Supercharged
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Joined: Sat Nov 27, 2004 8:03 pm
Posts: 7712
Location: IRWIN PA
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https://www.precisionintl.com/part/c/10 ... P210E.html


I usually buy 5 at a time to help on shipping.

Greg

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 Post subject: Re: Head porting
PostPosted: Fri Feb 05, 2021 3:53 pm 
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Turbo EFI
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Joined: Wed Oct 12, 2005 9:00 pm
Posts: 2366
Location: kankakee IL
Car Model: 80 volare, 78 fury 2 dr, 85 D150
Looks like the older fel pro is 3.540, I didn't think the chamber was bigger than the cyl bore but I have never bolted a head to a block and looked at it from beneath though I have heard it suggested in Doug's book relating to head to chamber alignment.
If that is right, then the gaskets have are slightly (0.020) larger than the printo seal version at least by printed specs. So that won't help.
I have exactly 1 NOS steel shim style head gasket here, I didn't measure that one.
Anyone have one of those head gaskets collecting dust that Greg highlighted that they'd spare?


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 Post subject: Re: Head porting
PostPosted: Fri Feb 05, 2021 4:57 pm 
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Turbo EFI
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Joined: Wed Oct 12, 2005 9:00 pm
Posts: 2366
Location: kankakee IL
Car Model: 80 volare, 78 fury 2 dr, 85 D150
Since it's gonna be so warm this weekend, (Hi tomorrow about 16*F, hi Sunday about 1/2 that and below 0 overnite) I think that I might spend it in the garage and pull the guts out of peanut head#2 and "practice" some more in case head #1 winds up as FUBAR. I've had wanting to do one up for the kid's truck anyways, with any luck I'll have one done for each at that point.


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