69 Lemans header gaskets.
 

A friend of mine has a 69 Lemans with header gasket leaks. The heads are 47's I think he should put manifolds on it and loose the headers. What do you think?

Sure if he does not mind giving up 15 Hp and 3 mpg.

I guess he is not racing his 350 with #47 heads?

Headers are for race cars and racers don´t mind regulary changing leaking gaskets as they always have something to repair on their cars.

The power loss may be at 5000 rpm´s and i don´t think he will notice any power loss under normal driving conditions using stock manifolds.

Quick question re headers vs manifolds. If he removes the headers and installs let’s say RA manifolds, will the down pipes easily line up with the exhaust? That is, do headers typically have the same spacing, width where they meet the exhaust as down pipes?

I've done the headers to manifolds thing,...both of mine ended up being in that 19 to 20 inch center to center for the head pipes. As far as getting rid of the headers and go to exhaust manifolds on the 350,,,definitely.

Headers are probably leaking because the 47 heads don't have the bolt holes drilled and tapped on each end. Has 4 bolt holes instead of all 6

Singleton you are correct. I just want to fix it and be done with it. So does anybody have a pair they want to sell?

You can call or text me at 708-204-7341 Thanks John

The 47 castings indeed do not have the outer bolt holes to seal up the end exh ports as needed.

Don’t go looking at the Pontiac 350 in the the light as a Chevy 350 when it comes to its response to headers.

The Pontiac 350 has a lot more stroke !

Try your luck with Remflex gaskets, much easier than taking headers off.

Just in general and from what I have seen over the years in terms of failed header gaskets is this.

If your motor mounts are worn and allowing the motor to rock more then normal then the headers being bolted to the exh system are put into the position of trying to hold the motor in place.
This will sheer the gasket no matter what is made of and a leak will develop sooner or later.

If you have headers with a narrow welded sealing lip then all the movement gets concentrated there and then any movement not only burns them out, but that narrow sealing lip chews thru the gasket due to the concentrated loads there.

I have always used a good slathering of anti- seize on both sides of my header and collector gasket’s do they if need be can slide on each other without getting torn up.

We have had excellent results with the RemFlex header gaskets .... I would probably try a set of those first, before changing headers out.....

We are going to try the Remflex gaskets 1st.

I like the Remflex material, they will definitely help prevent
leaks. Just double check the fit and the cut of the gaskets. I don’t know about D ports, but the cuts for the two center bolt holes on the Remflex for round ports was off enough that the bolts wouldn’t nearly go in. Had to pull the gaskets out and trim them up, surprisingly more than a little.


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Without the end bolt holes anything you end up with could leak. Crazy that some heads don't have all the holes.

I've had the same headers and gaskets on my 440 for around 20 years. Back then I asked my machinist about copper gaskets and other fancy stuff. His opinion was that header leaks come from loose header bolts. I've been safety wiring my headers and its eliminated problems.

1969 was the year the factory began producing some exhaust manifolds without the end bolt holes. I guess they decided they could save money that way, usually that’s the reason.

In 1965 both the manifolds and heads had all 6 bolt holes but they assembled the manifolds to the heads using only 4 bolts, there are pictures of 1965 GTO engines built that way sitting and waiting at the factory.

Usually the big-valve performance heads would have all 6 bolt holes drilled and tapped (1969 #62 & #48) but the low performance small valve heads (#46 & #47) had all 6 bosses cast into the head but only 4 were drilled and tapped.

Even some of the round-port heads (1971 #197 & 1972 7F6 455 HO heads) had only 4 bolt holes drilled and tapped, if you want to run headers you have to drill and tap the end bolt holes. The exhaust manifolds used on these heads were held on by only 3 bolts if that doesn’t sound crazy, the way the manifolds were cast only allowed for one bolt for the center two exhaust ports.

In a nutshell the factory didn’t give a damn if headers would seal or not, the exhaust manifolds sealed up fine with 4 or even 3 bolts in some instances.

Well I put the remflex gaskets in with no more exhaust leaks. I told my friend do not bring that oil and coolant leaking pos back. LOL

If you got headers: Remflex, Remflex, Remflex.

My 1969 47s have bolt holes on the ends. Should I assume they were added?

What does that stamping say on the front of your heads? May have had some good work done to them.