Crack in exhaust manifold

[Gary #41345]

My drivers side exhaust manifold had cracked sometime before I purchased the car and was repaired but apparently has cracked again in the same location. Should I just buy new exhaust manifold/s or get this repaired again and what would the results of a crack in a exhaust manifold have on the operating condition of the car? Also frozen heat risers can someone explain what this condition would do to the operating system of the car?

Thank you

[Peter K.]

What year?? *NM*

[Terry F.]

Re: Crack in exhaust manifold

Heat riser is that heat sensitive valve on the right side exhaust manifold. It is suposed to open as the engine warms up. If it is frozen open, your engine might warm up more slowly in cold weather and have symptoms of a cold engine for a while. If frozen closed and the valve will cause back pressure and the engine won't run properly and it will potentionally damage the engine. It is suposed to provide back pressure to cause hot exhaust gasses to be directed up through the base of the intake manifold and out the other side. An old engine will commonly have this path fairly crusted up or blocked off. So, in that situation it is worse and you will get even more back pressure. It is simply a bad thing when it is not funtioning properly.

If your exhaust manifold has good meat left in it, you can fix it. Sort of depends on who repaired it last time and how bad the crack is and where the crack is. If the crack re-formed you have to figure out if it was because of a poor repair, etc. If the crack is easy to get to, I would bolt the manifold onto the head and nickle weld the crack while attached to the flange....or weld it and resurface the flange of the manifold. There is a process call cast blasting that is very strong and looks just like cast iron but that might not work because of the location and need to bolt it to a flat surface. You just need to make sure the manifold does not have to flex when it get bolted back on the surface of the head. I like nickle rod when repairing cast iron. The nickle likes to bite into the surface of the cast iron. I have taken things apart that were nickle welded/brazed. Very tough repair. Drill a hole at the end of the crack to relieve the stress of the crack. V it out a bit and fill it back in neatly. If it is in a thin spot or the cast iron has been heated too many times from normal use or from previous repair work or worn away from rust.....you are wasting your time trying to fix it. If you are into hunting things down like I am....I would just hunt down a nice used manifold. I would not bolt anything back onto that head flange untill I prove it is nice and straight though. Hope that helps you out a bit. Take care, Terry

[Gary #41345]

Re: Crack in exhaust manifold

1966 Peter

[Jim T.]

Re: Crack in exhaust manifold

If a heat riser valve functioned as designed forever it would be helpful in cold engine operations especially in the colder regions. Later model Corvettes have a vacuum operated system that open and closes the heat riser valve. Lots of posts in the achives about this valve. One costly benefit of a heat riser valve is the early deterioration of the passenger side muffler. This one reason is why some Corvette owners will block/wire the heat riser in the open position, replace it with a spacer (fuel injected Corvettes came with this spacer in place of the heat riser valve), or remove the butterfly from the shaft and simulate the operation of the heat riser valve. For my driving I can live with just wiring the valve open and next time I remove the carb I am going to close off the passage way in the intake manifold on my 68 because it is an open chamber under the carb base. It does not take very long to get past cold engine performance in my area.

[Joe L.]

Re: Crack in exhaust manifold

Peter----

I wouldn't mess around with trying to have a cast iron manifold welded unless there's no way to get a replacement. For any 1966 Corvette, you can obtain a replacement manifold. Not from GM, though. However, these things are available in reproduction or good used.

[Mark #28455]

Google "Muggy Weld" *NM*