[RicksGTO]

I just pulled my original Ram Air manifolds from a '72 455HO and the passenger side has some small cracks that appear to be in the surface of the collector. I can't feel them on the inside of the collector so it doesn't appear they go very deep at all. Has anyone ever seen this in an older set and is there a problem with using them, or would there be some sort of low temp cast iron weld that would be needed. I am wanting to send them to be ceramic coated but don't want to waste the money on one that may crack further or eventually form a leak. Thanks for any help, Rick

[Jack Gifford]

I have no experience with the RA manifolds. If I were you, I'd try to learn the depth of those cracks with a small scribe or tiny wire. If the depth is some small fraction of the manifold thickness, I'd remove them by grinding.
Unfortunately, there's no such thing as "low heat welding"- whatever temperature cast iron melts at, that's it, no way around it. And welded exhaust manifolds seldom survive very long in use.

[Pontirag]

nickle welding but its overkill and probably may complicate the cracking delema further. in the early 70's chevy bigblock manifolds were doing that alot. eventually it will fail, I think its caused by running lean for long periods of time. polishing is an interesting idea it may prolong the life of that manifold but it will eventualy fail. Your new manifolds should have a thermally reflective coating on the inside of the runners. Perhaps port match them and cleane them up and extrude hone them first.

[RicksGTO]

thanks for the replies, I have had some heads nickle welded before once on an exhaust port but wasn't sure how thick the collectors are on these manifolds. I will try to carefully grind them and clean them up before deciding what to do. It's on the pass. side which is the easier one to change so I'm hoping it will clean up and not get any worse after thermal coating unless I find that it's deeper than it looks.

[Geoff]

Your manifolds may also need surfacing to true up the head mating surface. More $$$. The repro manifolds available now are claimed to be made from superior cast iron. Might be wiser to buy a pair of these.

[RicksGTO]

hey Geoff, I used the R.A.R.E. manifolds on my GTO when I changed the exhaust on that car and they are very high quality pieces. I believe they are made from the stronger ductile iron as you pointed out. I very lightly ground on the main crack last night for less than a minute and it ran on me so not much chance of savings this one now. These were also leaking at the head mating surface, so surfacing them would have not only cost more on these 35 year old manifolds, but put more stress on them. I will feel better having a set of the new ceramic coated manifolds on this car anyway. Thanks for the replies

[screamingchief]

My '72 455 H-O GTO had a cracked manifold on it when I got it,the crack ran right along the right angle "valley" in the casting on the engine compartment side,the crack was about 5-6 inches long and wide enough to make the car kinda sound like that plymouth fury in "Christine" when he first got the car and took it to that old coots garage.

You know,bbbrrraaappp bbbrrraaappp bbblllaaattt.

It was also running on 4 or 5 cylinders due to the unitized ignition neglect...

But for $500.00 it was a no-brianer.

The H-O mainfolds are known for cracking issues,mostly due to the use of just 3 bolts per side to mount them.

The other side was OK and had no cracks (drivers side) but that one later just found out it had been surfaced one too many times (I had them done at least once),and that let the manifold touch the block and this in turn casued some overheating issues that were hard to diagnose,replaced that manifold and the problem went away.

If it were me,I'd buy a set of the repos to use and save the originals for the sake of having them.

[RicksGTO]

I agree on the new ones, these are date coded to the car so I wanted to reuse them, but not at the point of having to put up with an exhaust leak or having it continue to crack. My neighbor at work is a good cast iron welder and swears he can braze the crack so I may see if he will take a shot at it but I still bet I'll end up getting a new set.

[Pontirag]

As you grind it it grows? Its not really worth saving. You could thermally stress relieve it. metallugical testing business's can put it in an oven and heat it up to its bright orange (TEMP?) and hold it for a while. Cryogenicly freezing it can take it down in temp. Then polish it, etch it, and do a dye penetrant inspection on it. Blah blah blah. Much money to tell you what you already know. Replace both of them with a new set properly prepared. Set the old ons aside for later on down the road if the technology changes or if you sell the car .

I cant recomend brazing. wrong co-efficient of expansion. plus its a one shot deal cause after tryin real hard to get brazing material down in that crack if it fails you cant weld over it and maybe not even be able to grind it out.

I would leave it alone for now. get the new ones and do a search on plasma spray welding.