Intake Manifold / head mismatch - Pontiac GTO Forum
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post #1 of 11 (permalink) Old 09-02-2017, 05:23 PM Thread Starter
 
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Intake Manifold / head mismatch

After reading what happened to Dan's Restore and his engine, I have discovered that I have a similar issue with mine. Apparently I have a 1973 intake on 1971 heads. I have read about using block off plates, or I could find the correct intake (which I believe is 481733). I came across this online. Could this work for me?
https://www.summitracing.com/parts/m...w/make/pontiac
Looks like it will allow some flow to work the choke, but blocks the top.

Thanks for your help
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post #2 of 11 (permalink) Old 09-02-2017, 09:48 PM
 
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You shood be able to get away using the '72 & later style intake gasket.

When it's the other way around, for example installing a '65-71 intake on 7K3's or 6X heads with active heat crossover, it's a matter of making a stainless steel shim that is slightly T shaped to block the recess at the top of the passenger side head's center heat crossover.
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post #3 of 11 (permalink) Old 09-02-2017, 10:53 PM Thread Starter
 
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Thanks for the reply. I have used the 72 style gaskets and am not having any performance issues, but there is definitly a mismatch between the intake and head. It is discoloring the paint on the manifold. I have attached a picture.
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post #4 of 11 (permalink) Old 09-03-2017, 08:14 AM Thread Starter
 
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Sorry, upon further investigation, I think I had it reversed, I have 1973 Heads and a 1971 intake. I will need to use the shims that you suggest.

Thanks
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post #5 of 11 (permalink) Old 09-03-2017, 07:01 PM
 
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Garage
The discoloration can be normal. This has been discussed before and it is hard to avoid the problem as the high temps of the exhaust gasses going through the heat crossover get hot. You might want to search the Forum to see what other members have used to deal with this problem.

I may be wrong, but I thought that some heads had that "pocket" you show in your photo and no exhaust gases pass through - it is actually hollow and sealed off from the exhaust crossover. Do you feel/smell the exhaust gases coming out?

You can make a "block-off plate" as PH noted, but these often will rot through at some point because they need to be thin. PH has covered this before in another post and I believe he recommended making one out of thin stainless steel.
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post #6 of 11 (permalink) Old 09-03-2017, 08:53 PM Thread Starter
 
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Thanks for the response. No there is not a leak there, as it is an empty pocket as you stated. Just has discolored the paint in that area. I will search for some additional information and most likely will end up touching it up from time to time
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post #7 of 11 (permalink) Old 09-04-2017, 11:25 PM
 
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"...I will search for some additional information..."


Pontiac Cylinder Head Modification - Hot Rod Network

The best iron intake for the late heads is the '72 model. It's a one year only intake. I'm sure PH can tell you more about 'em than I can. I noticed he recently bought one, real cheap, on another forum.

I've seen quite a few of these for sale on the PY site--some cheap, some not so cheap. At the time of this posting, there is one for sale for $100 + shipping. It's in Alabama.

http://forums.maxperformanceinc.com/...pontiac+intake

Sometimes a used Edelbrock Performer is cheaper. They'll work on early or late heads. Some say the iron intakes are better. Some say the Performer is OK for mild performance 400 & smaller engines.

Don't know if this one is good or junk. But the guy has a 100% positive feedback rating, for whatever that's worth. Lots of alum intakes have stripped out bolt holes. If you have any long time Pontiac guys in your area, you may be able to find a good one and save shipping charges.

http://www.ebay.com/itm/Edelbrock-Pe...dZnGTh&vxp=mtr

Last edited by bigD; 09-04-2017 at 11:42 PM.
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post #8 of 11 (permalink) Old 09-04-2017, 11:47 PM
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The discoloration at the crossover is normal, I shot my intake with high temp silver then high temp Pontiac metallic blue.
This basically gives you the factory look after the discoloration takes place.
Here is a pic of my '67 manifold showing the beginning of the discoloration.
I also drilled and tapped then plugged the crossover below the carb; this allows the divorced choke to work properly while keeping the heat from the carb base.
I also drilled and tapped the water jacket section so I could run with idiot light and gauge.
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post #9 of 11 (permalink) Old 09-05-2017, 08:31 AM Thread Starter
 
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Thank you all for the information. looks like I have several options
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post #10 of 11 (permalink) Old 09-12-2017, 12:50 AM
 
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Running a '65-71 intake on '72 & later heads with a functioning heat crossover w/o the passenger side '72+ intake gasket burning out is a relatively easy fix. I've referred to this fix several times, it flat out works. the stainless steel shim blockoff piece can be made in 15 minutes. Stumbled onto this solution many years ago dealing with a local who desired running his '65 GTO's tripower set-up on an .030 400 with 6X-4 heads. Just running the '72 intake gasket, it burned out right below the "dead spot" of the heat crossover, thus the need to block off to the bottom of the divider under the "dead spot" on the later style head. Since that first installation, have used the same stainless steel shim trick on over a half dozen other Pontiacs. No need for expensive intake swaps or just blowing off being able to run a '65 or '66 tripower intake on an engine built with '72 & later heads.

Making the stainless blockoff shim. First one needs a thin piece of stainless steel, not thin steel, or aluminum. The stainless steel needs to be thin, thin like the stainless shim gasket piece used on '67 Q-jet intakes. Years ago, I eventually struggled coming up with a readily avail piece of scrap thin stainless steel. Over the last two decades, many vehicles use a thin stainless steel piece that inserts between the brake pad & the brake caliper pucks. My sons 4Runner is one of many vehicles tht uses this piece of stainless, behind each brake pad. Its a piece of stainless steel that gets chunked everyday in shops across the country when a new pair of brake pads & stainless shim pieces are installed.

With a castoff piece of stainless shim from a brake pad replacement, along with a Dremel tool with 1" diam cutoff wheel, it is a simple matter of laying out the pattern & carefully cutting out the following shape.

Visualize the needed block off shim as the top of a capitalized T logo similar to what used on a University of Tennessee logo.

https://flagspot.net/images/u/us_tnvols2.gif

The top of this T is 4 5/8" wide.
The outside edges drop down 1 1/2"
Then on each outside edge, one kicks inwards 3/8".
Next, one goes straight up 1/2".
Next, one will have have to cut across (parallel to the top edge) 3 7/8" to connect the bottom plane.

Once the stainless shim is cut out, it is inserted on the passenger side. Between the heat crossover area on a '72 & later Pontiac cylinder head & the to be lined up '72 & later style intake gasket. The two 3/8" wide "legs" need to be carefully slid down abutting the top edges of the two center intake bolts. If one one likes, one can get creative with the Dremel tool & cup the shape of the two 3/8" wide legs so the legs are located to a small degree by the two center intake bolts.
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