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 Intake Gasket for this head/intake combo?
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cortcomp
Coyote

USA
5335 Posts

Posted - 13 Jul 2010 :  9:22:42 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
I just swapped my 670 heads for 6X-4 heads but am keeping my Performer RPM manifold. I use the felpro gaskets that let you block off or partially restrict the exhaust crossover (i usually block it off) but noticed that the exhaust crossover runs up closer to the top of the head and the intake isn't quite as high as the exhaust crossover port. The block off seems snug in there but i'm worried that with no metal pressing on it from the intake side, it will eventually blow through the gasket. Picture below. Suggestions or am i worrying too much?



Taman
Red Bird

USA
844 Posts

Posted - 13 Jul 2010 :  9:58:39 PM  Show Profile  Reply with Quote
My Flepro kit had a block off piece included in the kit. Standard Pontiac gasket.

Everything Under The Sun Is Intune
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Christ
Howling Wind

USA
1808 Posts

Posted - 13 Jul 2010 :  10:10:19 PM  Show Profile  Visit Christ's Homepage  Reply with Quote
quote:
Originally posted by Taman

My Flepro kit had a block off piece included in the kit. Standard Pontiac gasket.






Can you make the picture a little larger next time. Maybe it might fit on my 42 inch plasma next!
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cortcomp
Coyote

USA
5335 Posts

Posted - 14 Jul 2010 :  09:55:53 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
LOL Sorry! Took it with my phone too, didn't think it'd be that big! I don't know how to resize images for display using the forum code. i'll have to start resize before uploading, it's been fixed now.

The little line you see on the gasket is the block off piece's edge, it's the solid one. It's just that the seam of the block off piece meeting the gasket is actually slightly over the exhaust port on the head, meaning there should be exhaust pressure pushing on that seam at all times, right? Maybe it's off from having the heads milled, but the intake side was milled too and everything seemed to line up, bolt holes, ports, etc. It would just seem with enough time, the exhaust heat and pressure would cook the gasket and start making it flaky and then blow through.
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cortcomp
Coyote

USA
5335 Posts

Posted - 14 Jul 2010 :  10:22:22 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
For reference, here is the gasket i used:

http://www.summitracing.com/parts/FPP-1233/

I used the solid block off.
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Christ
Howling Wind

USA
1808 Posts

Posted - 14 Jul 2010 :  3:35:33 PM  Show Profile  Visit Christ's Homepage  Reply with Quote
http://www.highperformancepontiac.com/tech/hppp_0706_intake_manifold_replacement/photo_04.html


Here is the intake I use. The bosses for your cross over with the manifold you are using are to low and will eventually brun through!
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cortcomp
Coyote

USA
5335 Posts

Posted - 14 Jul 2010 :  4:11:17 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
If i'm not mistaken, isn't that a higher performance, higher RPM manifold? I want something for low end torque and to be "in it's powerband" at a lot lower rpm than most guys building a motor, so i was looking at a stock manifold or the performer rpm (which i have) because I've read the dual plane is going to work in the rpm range that i'm looking at. My other stock manifolds here also have the same height bosses, so it would seem they would line up the same way. (Didn't swap manifolds to check yet)

Even if i'm wrong, i do hate to swap manifolds, i find it hard to believe that you can't use an edelbrock manifold on later heads like the 6X-4 at all. Someone has to be out there doing it with a workable solution, whether this gasket, a different gasket, or some kind of modification.
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cortcomp
Coyote

USA
5335 Posts

Posted - 14 Jul 2010 :  8:31:13 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
To do some more checking, i drug out the following parts:

Stock 67 manifold
Stock 73 manifold
stock 77 manifold
Stock 6x-8 heads
stock 670 heads

The 670s are a non issue with any manifold because the exhaust crossover port doesn't go that high. The 6x-8 is exactly like my 6x-4s. Astonishingly, after setting it up and checking, all of the stock intakes leave the same area exposed. Attached is a pic of the 6x-8s. you can see the paint line and that some of the crossover hole is above the intake. The intakes and heads are all stock and not milled, etc like my 6X-4s.

I edited my pic to show my concern. The green line is about where the intake stops. The red outline is the block off insert piece. The blue line between them is the area i'm worried about. You can see that some pressure there on that seam and some heat i would think would lead to a blow through. I could cut the exhaust crossover off and use some plate any size i like to block it, but i have enough work to do now as it is. It looks like if you peeled the gasket back some after installation, exhaust would just blow right out.

I'm beginning to think they were like this stock. (i know there was no seam stock and you can get solid gaskets that don't need the block off that cover the hole, but it would still seem that the only thing holding the exhaust back is the gasket and the pressure of the manifold below it, no steel pressing directly on the gasket at the top of the hole.)





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Mark S.
Cochise

USA
432 Posts

Posted - 15 Jul 2010 :  03:14:06 AM  Show Profile  Reply with Quote
Okay, what manifold is in the first picture? The Performer RPM does not have a plate to cover/blockoff a choke stove on it. There is no choke heat stove mount to attach the OEM coil-style or heat tube style choke assembly on the RPM. It's manual or electric choke on that intake.

I think that's a standard Performer intake, not an RPM.

The Performer RPM has the "small" crossover passages the will match up with the "small" crossover ports on the 6X series heads. You need to use the intake manifold gaskets for the head you are running, that is, use the Fel-Pro gaskets for the 6X heads.

From the Summit site: "Notes: EDL-2156 (Performer) When installed on 1972 and up cylinder heads, intake gasket FEL-MS90205 or MRG-5848 is required to seal exhaust crossover."

Unless you're going for all out power, don't worry about trying to block the port at the manifold.
It won't last very long and will still leave those two center cylinders connected.
The only way to really benefit & truly block the exhaust crossover is to fill it with molten aluminum, while the heads are off for a re-build, overhaul, etc.

Don't worry about that upper opening. It does not connect to the exhaust port and does not need to be covered.
It's there to provide an air-gap to reduce heat transfer from the crossover to the oil draining back from the heads to the block, supposedly...

PSP Member since 1996

Never enough cubes...

"The difference between genius and stupidity is that genius has its limits." - Albert Einstein

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cortcomp
Coyote

USA
5335 Posts

Posted - 15 Jul 2010 :  10:17:30 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
Thank you for the reply and info!

It may be a standard performer, i couldn't tell from any casting numbers but it looked taller than the standard performer, so i'm likely wrong about it being an RPM.

It makes sense now that i look at the pic and don't see exhaust soot in that hole. If there's no pressure there i don't see any issues with the gasket installed now, especially since the stock intake would leave the same area above the intake exposed (Unless there's a problem underneath where i'd have to change gaskets? This gasket lined up with the heads perfectly when apart).

When i had the 670 heads on i had this engine running at a cool 150 degrees, even idling all day long in hot traffic. It's a feature that seems hard to attain for some pontiac owners and introducing heat right where the intake charge is coming in might upset whatever seems to be keeping my motor nice and cool. It's not all out performance that i'm looking for, i just want to keep it cool and it seems like an exhaust crossover is working against that goal. I don't mind waiting a minute for the engine to warm up before running well if it means cooler running and longer life.

The Previous owner had hot start and overheating issues using the same intake, radiator, and heads i just ditched (the crossover was connected for him), so i've been eliminating small causes here and there as i put it back together and it seems to have worked. I just prefered to block it for that reason alone. If it blows through and actually starts running warm i'll likely modify one of my stock manifolds and remove the water crossover and heat crossiver and block with a plate like jim hand showed in the book.

As it sits now, if there's no pressure on that top hole and the bottom one has the intake squarely on it, i should be good to go, especially considering the performer lines up the same as the intake that came on those 6x heads no?
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Christ
Howling Wind

USA
1808 Posts

Posted - 15 Jul 2010 :  12:31:28 PM  Show Profile  Visit Christ's Homepage  Reply with Quote
I wasn't telling you to use the intake just showing you the height of the port that covers the heat cross over. You will get away with it for a while but it will eventually burn through!
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cortcomp
Coyote

USA
5335 Posts

Posted - 15 Jul 2010 :  2:20:21 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
But considering that the stock intake for those heads covers the same height, wouldn't they all burn through if that was the case? Mine isn't any lower than a stock manifold for those heads.

As Mark said, i don't believe it's an exhaust opening after all, so it shouldn't have any pressure or heat to burn through anything with.
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ledhed76
Cochise

USA
304 Posts

Posted - 15 Jul 2010 :  11:10:54 PM  Show Profile  Reply with Quote
the top hole isnt an exhaust opening at all....i just put a performer intake on my 6x-8 heads and was wondering the same thing....after doing some more research, the hole is just for weight reduction???....i poured water into the hole on another set of 6x-8 heads i had, and it held water...
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cortcomp
Coyote

USA
5335 Posts

Posted - 16 Jul 2010 :  09:41:32 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
Well glad that it won't seem to be an issue, wasn't really looking forward to doing more intake work now anyway :) Thanks everyone for the info and the help.
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beertracker
Cochise

350 Posts

Posted - 19 Oct 2012 :  1:38:28 PM  Show Profile  Reply with Quote
I know it's a old thread but it is very useful to me since I am tackling the same problem with a 6x-4 head & 1970 manifold combo. Cortcomp your photos helped a great deal in understanding. Thanks to all who contributed.
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cortcomp
Coyote

USA
5335 Posts

Posted - 19 Oct 2012 :  1:44:49 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
Glad they could help! I am running 6x-8s and a performer rpm manifold and those gaskets with the block off inserts with no issues, for about 2K miles right now. No leaks, no gasket burn through, etc.
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beertracker
Cochise

350 Posts

Posted - 19 Oct 2012 :  6:57:55 PM  Show Profile  Reply with Quote
A couple of questions. Some of my friends are telling me I don't need to use gasket sealer between the intake manifold and gasket. They say sealing the intake gasket to head is all that is needed. What do you guys think.

In my gasket set I found 4 little plastic rings or inserts. They are just the right size to fit inside the intake manifold gasket bolt holes. I assume these are guide inserts to keep the gasket from shifting around when the manifold is lowered in place? Just insert them in the gasket, lower the intake manifold and tighten down with the bolts leaving the inserts in place?

I too have a couple of 6x-8 heads that I am saving for a 455 build some day!

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cortcomp
Coyote

USA
5335 Posts

Posted - 19 Oct 2012 :  8:34:45 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
Don't use those plastic guides, they've screwed me more times than they've helped me, maybe i'm doing it wrong. I only use the lightest of coats of RTV over the seam where the gasket insert blocks the crossover, and more to hold it snug there for assembly (fits tight anyways, but belt and suspenders and all.

I don't use any other sealer or liquid. Being careful, it's very easy to set the intake on and make sure the gaskets are still lined up, especially on a pontiac where the valley pan lip holds them from slipping down too far.
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74_Formula
Buffalo

USA
92 Posts

Posted - 06 Feb 2013 :  2:29:39 PM  Show Profile  Reply with Quote
This thread just answered every question I had abt this issue. Just posted a intake gasket question yesterday! Shlda searched the threads first lol
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cortcomp
Coyote

USA
5335 Posts

Posted - 06 Feb 2013 :  4:16:14 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
I totally forgot we had this thread, and i started it! Glad it was useful :)
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74_Formula
Buffalo

USA
92 Posts

Posted - 06 Feb 2013 :  4:34:56 PM  Show Profile  Reply with Quote
Definitely useful. Eliminated all the worries I had about this exact issue.
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chris60s
Tribal Scout

USA
14 Posts

Posted - 30 Nov 2014 :  6:40:16 PM  Show Profile  Reply with Quote
I've got the same issue and thought this thread provided a solution until I looked at the crossover port on the intake manifold.... it's BIG, about the same as intake ports so exhaust will leak around the horizontal section that separates the lower section in the head (to exhaust) from the smaller upper section. If the exhaust port was completely covered by a closed gasket it might hold for a while, but I think it would eventually blow through. Below is a permanent solution.. filling the upper hole with furnace cement will give a solid gasket sealing surface - this would allow the crossover to be used if desired. Interesting about that upper hole it was done for oil cooling (according to this article):
http://www.hotrod.com/how-to/engine/hppp-1301-pontiac-cylinder-head-modification/
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cortcomp
Coyote

USA
5335 Posts

Posted - 30 Nov 2014 :  6:46:16 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
"2. Beginning in ?72, Pontiac added this hole above the exhaust crossover. Said to keep oil flowing under the valve cover isolated from exhaust heat, it?s completely separate from the crossover and does not connect to any other port or passage."

That port doesn't do anything at all, it's not where the "blow through" would be, it'd be if the gasket leaked between the two sections, which doesn't happen with the above gasket.
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