73 454 header pipes
Thread Starter
Racer
Joined: Jun 2011
Posts: 300
Likes: 3
From: kempton park Gauteng
73 454 header pipes
Hi GUYS ,
Back again and need some advice for replacing the headers on the big block.
Since i received the vette i have had problems with the exhaust headers blowing . I replaced the exhaust gaskets and all was fine for a short while and the gaskets blow out at the base in three of the ports on the right bank. Everytime its the same which makes me think its the headers heating and causing a bow which allows a gap for the exhaust to blow . ( not so ??? )
I have looked on the Summit site and there are so many types to choose from i need some recommendations , the exhaust is standard and the heads are cast (original motor ) Please let me have your advice and thoughts on the correct selection
Cheers and thanks guys:
John
Back again and need some advice for replacing the headers on the big block.
Since i received the vette i have had problems with the exhaust headers blowing . I replaced the exhaust gaskets and all was fine for a short while and the gaskets blow out at the base in three of the ports on the right bank. Everytime its the same which makes me think its the headers heating and causing a bow which allows a gap for the exhaust to blow . ( not so ??? )
I have looked on the Summit site and there are so many types to choose from i need some recommendations , the exhaust is standard and the heads are cast (original motor ) Please let me have your advice and thoughts on the correct selection
Cheers and thanks guys:
John
Pro
Joined: Feb 2012
Posts: 577
Likes: 6
I don't think you need new headers yet. Instead take the headers to a machine shop and have them grind all the tips of the primaries perfectly flat and square in relation to each other. The problem is that the tips are not perfectly flat and the gasket makes up that gap for a short period until the exhaust digs and burns it's way through. Once the tips are ground flat they'll seal and stay leak free for a very long time. Should be a lot cheaper than new headers too.
Race Director
Joined: May 2006
Posts: 18,709
Likes: 2,574
are you tightening the bolts in the sequence from the center 2 and then out to one side and then to the other side? Assuming it's not a metal gasket, have tried soaking the gasket in warm water for a few minutes before installing?
Thread Starter
Racer
Joined: Jun 2011
Posts: 300
Likes: 3
From: kempton park Gauteng
73 454 Headers
I don't think you need new headers yet. Instead take the headers to a machine shop and have them grind all the tips of the primaries perfectly flat and square in relation to each other. The problem is that the tips are not perfectly flat and the gasket makes up that gap for a short period until the exhaust digs and burns it's way through. Once the tips are ground flat they'll seal and stay leak free for a very long time. Should be a lot cheaper than new headers too.
Thanks for the help with my manifold problem.
When the car arrived in S.A the right bank was blowing badly and i ordered a set of the metal gaskets which have the coating on them, locally manufactured.The gaskets that were with the car were some type of paper type material .
I loosened the manifold from centre points outward , and refitted in the same fashion , and the blow seemed to have been cured , but this joy was short lived as a few weeks later the leak was back . Sure enough when i removed the gasket the lower sections were burnt through again , so i believe your diagnosis to be 100% correct .
For now i have removed both gaskets and fitted the headers face to face with the heads with a very high temperature compound , which is not a silicon and neither a gasket paste that hardens , but i think that the correct way to go will be to replace or have the headers faced off square again .At the moment all is quiet and sounds sweet.
Cheers for all the help and to all the other guys that chipped in to help me get past this problem.
John
Thread Starter
Racer
Joined: Jun 2011
Posts: 300
Likes: 3
From: kempton park Gauteng
Thanks for the pointers ,
The gaskets i put in were made in South Africa , and are a metal coated type which is supposed to be fitted dry , ie without any form of sealant put on them . I think the problem is as mentioned by Mark ( THANKS MARK) I think the face of the headers is not 100% square , but i have installed the headers face to face with the head surface with a special sealant available in South Africa that the racing guys tend to use for quickness and ease of replacement , but i doubt this will provide the permanent solution i am looking for , more of a stop gap until i can give up the car for someone to clean the faces or i fit new headers .
and thanks a stack ,John
Thread Starter
Racer
Joined: Jun 2011
Posts: 300
Likes: 3
From: kempton park Gauteng
454 Headers Problem
I must assume from your user profile that you also have a 454 any pics ??
Thanks for the help , I have replied to a couple of the other guys , so you will be able to pick up on what i have done so far and where too from now , your help and advise is greatly appreciated as is that of all, of the members on the forum, life would be extremely frustrating without the pointers that you guys provide .
Thanks
John
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Thread Starter
Racer
Joined: Jun 2011
Posts: 300
Likes: 3
From: kempton park Gauteng
73 454 big block manifolds
Good to hear from you again.
Sorry i maybe didn't explain the whole scenario correctly .
The engine and heads are all original , cast heads, the manifolds have at some time in the cars life been changed and are aftermarket headers and not the original cast iron manifolds that GM fitted .
It does appear as if once the engine is very warm the headers move away from the heads fractionally causing the manifold to blow and the gaskets to get burnt away at the bottom edge of the port face .
I have now taken out the gaskets completely and used a compound gasket material which seems to be holding well without leaks , however i do not think for one moment that it will prevent further leaks and feel my best option would be either to get some new ceramic headers , or remove the headers from the car and get the faces of the flange machined flat and re- torque the manifolds up correctly evenly across the face . It might be that someone previously tightened the manifolds without using the correct sequence and torque values and pulled the manifold out of square .
I would welcome your thoughts on the matter though .
John
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
My 69 BB has had headers on it since 1971- never had any problems with header gaskets. The only time I've replaced them was when the headers were replaced/upgraded or the heads came off.
Install, tighten the bolts, start the engine and get it good and hot, tighten the bolts, let it cool, tighten the bolts, run it again, tighten the bolts, cool, tighten the bolts- you get the idea. I do this for about 4 weeks- everytime without fail. After that, it's just check them once in a while. So far, I've never had to replace a gasket. And that's with aluminum heads and Hooker sidepipes.
Install, tighten the bolts, start the engine and get it good and hot, tighten the bolts, let it cool, tighten the bolts, run it again, tighten the bolts, cool, tighten the bolts- you get the idea. I do this for about 4 weeks- everytime without fail. After that, it's just check them once in a while. So far, I've never had to replace a gasket. And that's with aluminum heads and Hooker sidepipes.
