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Discussion Starter · #1 ·
Hello everyone. I recently purchased a 1967 GTO. The car originally had a 400ci with 335 hp “YS” code with an automatic transmission. However it now has a 455ci the engine based on the numbers next to the timing cover (starting with 22P) it was originally in a 1972 Pontiac. This 455ci has “YC” code on the front of it under the passanger side head and casting 485428 so I based on my research it’s the 250 hp model but was produced in August of 1971 per the top rear of the block.

There is an exhaust leak coming out of the front of both exhaust manifolds towards the front most portion of the engine. The drivers side leak is worse compared to the passanger side. At first I assumed this was due to bad gaskets or loose bolts upon closer inspection it appears that front bolts on the exhaust manifolds do not exist as they do not have a hole to put a bolt into on the head.

I think it is safe to assume that when they swapped the original 1967 400ci 335hp engine for this 1972 455ci engine they left the factory 1967 exhaust manifolds would this explain the difference in holes in the head vs exhaust manifold?

So now comes the real question what will I do to fix it. I thought about ordering the thick aluminum or copper exhaust gaskets and hoping even with the lack of front most bolts this would help prevent leaks due to thickness but that idea may be unrealistic. Another idea was trying to find exhaust manifolds or headers that are designed for the 1972 455ci but these will probably not have a design to fit in the 1967 gto engine compartment.

Does anyone have any suggestions? I am willing to spend some $ for headers if this will fix it or go on a search for 1972 455 exhaust manifolds to keep a stock look. Any help will be appreciated.
 

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You have a few options. You can try the copper gaskets and you may have luck so long as you don't have any cracks or warping to cause issue. You could have the 2 extra holes drilled and tapped and install the extra bolts. Or you can replace the cylinder heads. I don't know of any headers that will seal well with only 4 bolts. The most efficient option is drilling and tapping. Just be sure to not drill too deep or you may be moving on the the option of replacing the cylinder heads!
 

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You have a few options. You can try the copper gaskets and you may have luck so long as you don't have any cracks or warping to cause issue. You could have the 2 extra holes drilled and tapped and install the extra bolts. Or you can replace the cylinder heads. I don't know of any headers that will seal well with only 4 bolts. The most efficient option is drilling and tapping. Just be sure to not drill too deep or you may be moving on the the option of replacing the cylinder heads!
Seems you have 2 posts going?

Good exhaust gaskets are the fix for stock manifolds or cast RA manifolds.

For headers:

This is an aftermarket fix IF the heads do not have the extra casting metal where a bolt should have gone. Uses the bolt holes on the back of the heads to secure them. Basically an "L" bracket with a stud welded on.

If the port has the material where a bolt hole could have been drilled and tapped, then these will not work and you need to drill and tap a hole for the bolt.

The easiest route will be to purchase cast iron aftermarket Ram Air exhaust manifolds/gaskets as they are rigid enough that they do not need the additional bolt hole to hold them tight and will perform as well as headers.


Auto part Automotive exterior Bumper
 

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Discussion Starter · #5 ·
Thank you to everyone who replied. I did some more research and it is clear the engine is a 1972 455ci 250HP with head casting 7M5 but using the original 1967 400ci 335hp exhaust manifolds.

The heads do not have holes for the front most bolt or the rear most bolt so there are only a total of 4 bolts holding the exhaust manifold onto the heads. It looks like there may be material tap and make the additional holes but I only want to look into that if completely necessary.

so it looks like the first order of business is replacing the exhaust manifold gaskets and 4 bolts. I have a few questions now

1) I know the ports are “D” ports it looks like there are options for exhaust gaskets with separated center ports or one large center port without a piece of gasket separating the center ports. Which type is recommend?

2)for replacement exhaust manifold bolts from research it looks like they are 3/8-16 thread what length should the bolts be? Guessing if the thicker gaskets (rem flex or the copper ones) are used the bolts may need to be a bit longer than stock.

3) I thought about trying to use the copper sealant to try and seal the front port with the worst leak but I doubt it will stand up to the heat or be a quality lasting repair.

Again thank you for the responses they are greatly appreciated.
 

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Never had that great of luck with copper gaskets. Best thing about them is they don't blow out and the small leaks do not get worse. Sounds like the mating surfaces are warped and the copper gaskets really don't have much to offer in filling up any voids. Wouldn't take much to pull them away from the head and take a straight edge to both manifolds and head surfaces and see if you can see where the problem is. Figure that Pontiac did obtain a proper seal with leaving out bolts so you should again be able to achieve a quiet exhaust. A good machine shop can resurface the manifolds if necessary. If it is the heads, they can also be surfaced but only financially practical as an added step during an engine rebuild.

If I were to give it my best shot without doing it "properly", I'd use Remflex gaskets and hope for the best. We've used a bunch of those on header installations and they seal up very well and are resistant to blowout. Might or might not work, but if adding a gasket to take up gaps they would be my choice.
 

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Discussion Starter · #8 ·
Thank you again for all the great info everyone.

I checked and there is not any material on the heads for a hole to be drilled and tapped in either the front or back of either head. I will try to include a photo of the front drivers side where the leak is the worst. I am going to try the following

1) try to use the copper exhaust sealant to temporarily fix the leak. I would imagine this will fail quickly if it even works at all. I am only hesitant to remove the manifolds because I highly suspect one of the 4 bolts holding it on will break

2) remove exhaust manifolds, resurface manifolds replace gaskets with remflex or similar and replace all bolts (4 each side)

3) possibly get headers and attempt to secure using the head “L” brackets that Pontiac Jim suggested.
134234
 

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KevGTO67,

Now that you have the car, find yourself the correct '67 YS engine for your car, and do it right.

They are out there to be found.

Object of the hobby in my view is to restore our car's to original, or as close as you can to get it there.

Why do you want a '72 250 HP 455 in the car anyway...?

Its supposed to be, as you already know a 335 HP block w/670 heads.

Search suggestion - You can do an All of Craigslist Search and something will turn up for you.

It's just going to take some digging to find on,e and someone on the forum here may have one to sell to you...?

I'm working w/guy now junking out trashed '67 for an AT to 4 speed conversion project.

Donor GTO has a WT engine (4 speed motor) that going to be available, but it is locked up - and it has 670 heads.

May be salvageable, and even pretty reasonable...?

The right motors are out there, and can be had. I may have a line on some others, but would need to check more.

I recommend spending a little time & effort & then some dough to make your 67 a real GTO again.

Just thought I'd share my thoughts.

Best regards,

Lfryklu
 

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KevGTO67,

Now that you have the car, find yourself the correct '67 YS engine for your car, and do it right.

They are out there to be found.

Object of the hobby in my view is to restore our car's to original, or as close as you can to get it there.

Why do you want a '72 250 HP 455 in the car anyway...?

Its supposed to be, as you already know a 335 HP block w/670 heads.

Search suggestion - You can do an All of Craigslist Search and something will turn up for you.

It's just going to take some digging to find on,e and someone on the forum here may have one to sell to you...?

I'm working w/guy now junking out trashed '67 for an AT to 4 speed conversion project.

Donor GTO has a WT engine (4 speed motor) that going to be available, but it is locked up - and it has 670 heads.

May be salvageable, and even pretty reasonable...?

The right motors are out there, and can be had. I may have a line on some others, but would need to check more.

I recommend spending a little time & effort & then some dough to make your 67 a real GTO again.

Just thought I'd share my thoughts.

Best regards,

Lfryklu

Why should the car be restored to its original condition? What good would it serve to locate a block code matching engine when the cast date codes and EUN will not match the build sheet? It does not have the original engine, period, so installing a "faked" engine is no better than a lie - which many try to pass off as original.

Trying to restore a car to its original configuration may be fine for those who can afford the absurd prices for NOS, original used, reproduction it may fit parts, and the labor rates associated with removal, rebuilding, installation, etc., if the owner can't swing the prices or does not do his/her own work?

What do you do when you buy an original engine that is frozen only to open it up and find that it has been used as a boat anchor for several years. Money thrown out the window and I don't know many who will guarantee your money back PLUS shipping. So working with an engine that is already in the car and runs is a far better risk than a cast iron boat anchor - yep, even I got that end of the stick and its money wasted.

The 455 has far more potential than the original 400 IF that is the eventual goal of the owner in assembling either a low RPM torque monster or high HP/TQ RPM engine. The owner may have his sights set on upgrading the engine with better aluminum heads and lowered compression to work with pump gas.

So it is your opinion, and your dollar, that supports your view of how the car should be brought back. Most here are not looking to do restoration, but rather, personalize their rides in a manner that suites them which may or may not lean towards original. I think for many of us, the object of the hobby revolves around budget and fun, not restoration, $value, and trophies. (y)
 

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There is an object to this hobby? I bought a restored 1962 IH Farmall.if that counts. I have used it on my fields since the day I bought it. Had a SS Chevelle, rebuilt the motor and trans. with go fast parts. Took in down to bare metal then on went base coat clear coat paint. I have a 1967 Cougar that will probably get the same treatment and then some. I am looking for a first Gen GTO or equivalent for a ProTouring type setup. I don't want a museum piece. I want to drive something fun. Enjoy it with my family
 

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Discussion Starter · #12 ·
Everyone thank you for all the replies. The 72’ 455ci 250hp engine is what is currently is in the car and was put in prior to my ownership. I don’t know what the reasoning behind that was was except I am guessing the original engine broke and a 455ci was readily available . My intentions of fixing the exhaust are only to drive and enjoy it as it is. It drives great but as is but the exhaust leak is annoying. I respect each persons intentions with their own car and to each his own. As for this car I would like to keep it as original / stock looking as possible but would entertain suspension / brake improvements all “bolt on” that could be changed back.

I would like to find an engine similar to the one that originally came in it 1967 code “YS” 335hp (with auto trans) According to the PHS the engine would be # “Y 55160” . If anyone knows of an engine for sale that would be similar to this I may be interested in purchasing it and store it until I have(hopefully) the money allocated to build it correctly.
 

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Its great that you want the high compression motor. I would suspect that you would need to make gear changes to get the most out of the 455. A friend had a 72 Grandprix with a 455. Great car, real tire burner but everything has to match to get the best out of it.
 

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Everyone thank you for all the replies. The 72’ 455ci 250hp engine is what is currently is in the car and was put in prior to my ownership. I don’t know what the reasoning behind that was was except I am guessing the original engine broke and a 455ci was readily available . My intentions of fixing the exhaust are only to drive and enjoy it as it is. It drives great but as is but the exhaust leak is annoying. I respect each persons intentions with their own car and to each his own. As for this car I would like to keep it as original / stock looking as possible but would entertain suspension / brake improvements all “bolt on” that could be changed back.

I would like to find an engine similar to the one that originally came in it 1967 code “YS” 335hp (with auto trans) According to the PHS the engine would be # “Y 55160” . If anyone knows of an engine for sale that would be similar to this I may be interested in purchasing it and store it until I have(hopefully) the money allocated to build it correctly.
Why not keep the 455 short block, and use the correct '67 heads, intake, carb, points distributor, exhaust manifolds, brackets, and air cleaner? If you don't mind high compression and using 95+ octane, it would be an easy build. If you wanted to use pump gas, then get the corresponding dished pistons to lower compression with the 067 heads. 98% of the people will never know the short block is a 455 and it is just as saleable, if not better, than a non-numbers matching '67 400CI.
 
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