After about six months of searching I located and purchased an 89 Red with Black Allante in pretty good shape. There are cracks in the exhaust manifolds. I noticed these same cracks in several of the Allante's that I checked out in my search and yet I find nothing on any of the Allante Web Sites or forums about this problem. I found today that I can order a set of new manifolds for just under $1000 and that may be the fix. The car is worth it, I am just wondering how other's may have dealt with this?
Thats a new one on me. $1,000.00 seems a little high priced to me. Your source seems alful proud of there product(must be the General himself). You might try looking at some junkyards to see if you can find some that will fit off a wrecked Caddy with the same engine. Perhaps someone else will chime in with more knowledge than me, but I think that manifolds will interchange relatively easy.
This sub frame and basic engine were from an 87 to 92 Eldo or Seville. Called E body by wrecking yards. I would think these manifolds would be the same. My '88 manifold welds look like they are cracked but are in fact, not. The type of welder?used gives the appearance of cracks at the welds but is just overlap at the individual tubes. Try a wrecking yard first and report back. I would think for less than a $1000.00 you could have a certified welder repair both.
You may be right, they may not actually be cracks. Nearly every one that I looked at during my search appeared to have cracks and if that were the case I am sure there would be talk about that on the forums? I will investigate further and let you know what I find. Thanks,
I went back and re-examined the manifolds. They are cast units with no welds on them. The crack lines look like cracks? So I will blow a harmless smoke in the tailpipe and see where it comes out?
I got the right manifold off today and the crack in it is hardly visable but the left manifold is severly cracked. Unfortunately it is also very difficult to get off. I am still working on it. I also discovered that neither manifold has a gasket between it and the head? I can't find anything in the shop manual concerning gaskets but the local auto parts dealer listed one for it. So I will put the manifolds back on with gaskets. Also a few of the bolts were loose and exhaust was blowing by the manifold. I don't know if this is the result of somebodies poor work in the past or if it is original?
Yes, I have confirmed through a couple of service manuals that there are no gaskets, My question now is what will be the result if I add gaskets? Dick at Allante Source says that he too has seen many cracked manifolds. With only 18lbs of torque on the bolts, as soon as the manifold cracks, it is no longer square with the head and it leaks. Brazing or welding the manifold will only make any out of square worse requiring the surface to be machined. If they are prone to crack (for unknown reasons) what would prevent it from happening again? This is not a simple job and I don't want to do it again. Gaskets are looking good at this point unless there is a major reason not to use them.
I finally got the manifold off the right side of the engine. Here is a picture of the back side of the manifold, this crack nearly went all the way around.
