Brazing an exhaust port on an iron head

Posted By: domingo

Brazing an exhaust port on an iron head - 08/19/11 05:09 PM

I know that its always said that you can braze intake ports to fix cracks, pinholes, etc because of the lower temps found in the intake port....

...but when you are taking about exhaust ports you CANT braze them due to the increased temperatures found there which would soften the bronze and it would do little to prevent cracks or pin holes from seeping water.

Now....

What if you had an exhaust port that had been opened up a tad bit too much and you would want to fill it up some by brazing and then reworking it. This is at the very end of the port opening where the gasket sits. Seems somebody port matched and went a bit overboard and enlarged the port opening a bit too much.

This port doesnt have cracks or pin holes, I just want to fill it up some at the very end of it and port match it again.

Will bronze hold up or will it melt????

Any other ideas?

Thanks!

Domingo

Posted By: S/ST 3040

Re: Brazing an exhaust port on an iron head - 08/19/11 05:17 PM

Brazing is a very common practice for repairing exhaust ports.

Posted By: domingo

Re: Brazing an exhaust port on an iron head - 08/19/11 05:27 PM

Quote:

Brazing is a very common practice for repairing exhaust ports.

really?? I always thought it was OK on the intakes but a real NO NO on the exhausts!!!!

Is there a possibility that a bronze filling actually MELT off on an exhaust port?

Posted By: DJVCuda

Re: Brazing an exhaust port on an iron head - 08/19/11 05:28 PM

I've seen exhaust manifolds that were brazed to fix a broken ear, or crack last years and years...

Posted By: domingo

Re: Brazing an exhaust port on an iron head - 08/19/11 06:16 PM

Well, exhaust manifolds are farther away from the heat....and an ear is not in direct contact with the heat.

I am concerned about how will a bronze filling behave INSIDE the exh port walls!

Once again, it wont be sealing any cracks or pinholes or trying to prevent water from seeping. The exhaust port is just fine, and it passed the water pressure test just fine. I just want to fill it some to rework it.

Posted By: Hemi Allstate

Re: Brazing an exhaust port on an iron head - 08/19/11 06:34 PM

I have seen exhaust ports brazed and filled on the bottom when raising them for SS etc.
The intake side could be epoxied, but exhaust is brazed.

Posted By: MR_P_BODY

Re: Brazing an exhaust port on an iron head - 08/19/11 07:54 PM

If your really worried about brasing it, weld it
with high content nickle rod

Posted By: dogdays

Re: Brazing an exhaust port on an iron head - 08/19/11 08:46 PM

The wall of the exhaust port has water on the other side so it probably is cooler than the exhaust header.
R.
You could drill a hole in an exhaust header or manifold and insert a brazing rod with a square tip. Run the engine up some hills and then take out the rod and see how it looks. This actually sounds like a fun experiment.

Posted By: domingo

Re: Brazing an exhaust port on an iron head - 08/19/11 09:17 PM

Quote:

I have seen exhaust ports brazed and filled on the bottom when raising them for SS etc.
The intake side could be epoxied, but exhaust is brazed.

Thats exactly whay I am looking to do....kinda what SS racers do. I know they raise the exh ports on the heads and make em smaller....I wonder if they do that by brazing the exh ports. If that is the case, I know I will be 100% safe.

It'd be great if Jeff (modern cyl head) could chime in....I know he does heads for the SS guys.

Posted By: POS Dakota

Re: Brazing an exhaust port on an iron head - 08/19/11 09:40 PM

I cant see the port reaching any critical melt temperature given the fact that the head is constantly being cooled by water. It might cool slower than aluminum, but I cant see the head itself reaching any temperature where the repair would melt.

If an exhaust manifold that is not cooled holds, the head will hold fine is my thought on it.

No????

Posted By: dannysbee

Re: Brazing an exhaust port on an iron head - 08/19/11 10:06 PM

The melting point of brass is 1700 degrees, aluminum is 1200 degrees.

Posted By: Hemi Allstate

Re: Brazing an exhaust port on an iron head - 08/20/11 03:45 PM

Quote:

Quote:

I have seen exhaust ports brazed and filled on the bottom when raising them for SS etc.
The intake side could be epoxied, but exhaust is brazed.

Thats exactly whay I am looking to do....kinda what SS racers do. I know they raise the exh ports on the heads and make em smaller....I wonder if they do that by brazing the exh ports. If that is the case, I know I will be 100% safe.

It'd be great if Jeff (modern cyl head) could chime in....I know he does heads for the SS guys.

How's this look? It may be some of Jeff's work!

Attached picture 6786903-Copyofportbrazing.jpg

Posted By: domingo

Re: Brazing an exhaust port on an iron head - 08/20/11 04:11 PM

Thats all I needed to see!!! Thanks! I will go ahead and fix my heads that way....thanks!!!!

Posted By: torkrules

Re: Brazing an exhaust port on an iron head - 08/21/11 01:25 PM

Quote:

If your really worried about brasing it, weld it
with high content nickle rod

+1 on that. I had a pin hole in an iron head. we heated it with a torch and zapped it with a high nickle rod. I think the heads are still around to this day.

Posted By: 70Cuda383

Re: Brazing an exhaust port on an iron head - 08/21/11 03:45 PM

I don't know a lot about brazing yet, but I've watched my dad do it a few times, oxy/acetylene hot blue flame to heat the metal to cherry red and touching the rod to it to melt the brass into it...that's GOTTA be hotter than any exhaust is going to get.

unless you run stupid lean!

but, if you're really worried, maybe look for someone who can weld cast aluminum up with steel rod.

Posted By: justinp61

Re: Brazing an exhaust port on an iron head - 08/21/11 04:09 PM

Quote:

but, if you're really worried, maybe look for someone who can weld cast aluminum up with steel rod.

I'd pay to see that trick

Posted By: MR_P_BODY

Re: Brazing an exhaust port on an iron head - 08/21/11 04:17 PM

Quote:

Quote:

but, if you're really worried, maybe look for someone who can weld cast aluminum up with steel rod.

I'd pay to see that trick

LOL.... same here

Posted By: Mike Swann

Re: Brazing an exhaust port on an iron head - 08/21/11 04:30 PM

Back in the 70's, I was given a 70 Pinto with a 1.6 crossflow head that was wounded. After taking it apart, it had a burnt ex valve and cracked seat. After consulting with the wise shop owner that I worked for, I gound out the crack, we heated the head in the oven to 400F then brazed/filled the crack. Then, I had a seat put in it and ported the crap out of it. That motor got me though college and saw 7500rpm daily.

Posted By: HEMIFRED

Re: Brazing an exhaust port on an iron head - 08/21/11 04:52 PM

Quote:

Thats all I needed to see!!! Thanks! I will go ahead and fix my heads that way....thanks!!!!

you had better know how much pre heating and cool down time it needs. all I have seen done used a furnace to braze