1989 460 EFI E350/motorhome passenger side exhaust manifold has the two rear bolts broken. I know this is a common problem. I want to try and fix it with out removing the exhaust manifold. Motor only has 45k on it and runs like a champ, compression test was perfect on all cylinders. I don't want to take a chance of breaking any more bolts and having to pull the head. Besides working on the E350 chassis sucks.
I want to drill them out and possible helicoil them if the treads are shot. Question I have is how deep do the threads go in the head? The bolts are broke flush with the head, I don't want to drill too deep.
Anyone ever try this with the exhausrt manifold still in place?
Thanbks JKaz

 

You are venturing on a project that I wouldn’t want to do. It is a major bitch to drill them out even with the head off. I drilled two out and made a mess of the threads. I took the heads to a machine shop and they took a cutting torch to them. They heated each one up to cherry red and hit the oxygen and it blew the darn things out. Then they ran a tap in to clean any of the slag out of the threads. I asked if it damaged the heads and they said no because they were dissimilar metals. You might go to a shop and ask for advice.

My heads are off right now so I measured the thread hole depth and it measured one inch on all of them. I hope this helps.

 

Gary thanks for the reply. Might have to try the torch trick. Might be
easier then trying to drill blind and upside down. Would have to remove carpet and such so it doesn't catch fire.
Thanks JKaz

 

Kaz,

Have you done it yet ? Just wondering how it went. When my 87 did the same thing, I was lucky enough to have some of the studs exposed, so the shop was able to heat them up and back them out. Still was a HUGE mess. I ended up putting a set of Hedman Headers on, and LOVE them !!

 

Not yet, Just got the rig down to my buddys shop on friday. He has an old polish mechanic that can fix anything, we will work on it this week. I thought about headers but don't want to risk breaking anymore bolts and have to pull the heads. The two that are broke are the back two on the pass side so they are somewhat easy to get to. Some of the others I can't even see. I'll keep you posted.
JKaz

 

Good luck removing them with the manifold in place.

 

I was told the reason the bolts broke were because the manifold got hot enough to warp and twisted/ snapped the bolts. Which meant the manifold was trashed because it would never seal right now that it was warped. The price of the headers were cheaper than replacing the manifolds, and when all was said and done, it was only about $225 more including the new dual exhaust. Plus it sounds sooooooo awesome, lol.

Besides, how do you plan to replace the gasket if you don't pull the manifold ? Or are you just going to bolt it back down and hope it seals ?

 

Just going to bolt it down and hope it seals, factory didn't use a gasket. Already running wire insulation on #4 plug wire. This thing sees maybe 2500 miles a year. I take it on one or two camping trips and a few races. Not gonna try the torch idea, don't think the head gasket would appreiciate all that heat. I keep ya posted.
JKaz

 

Just to get back to you guys. Drilled and tapped the two holes. Used studs instead of bolts. Still has a exhaust slight leak, not bad after it warms up. Only cost me a half dozen cigars. lol
JKaz

 

Glad to hear that you got it going. The studs are a good idea. If the nuts freeze you can just crack them to get them off. They should never seize if you used brass nuts. I am not sure if the studs would work on the drivers side due to the steering column. There might not be enough clearance to slide them off of the studs on some vehicles.

It is my own personal opinion that the hot air shroud on the right side manifold is what gets that manifold so hot and makes it warp and crack. The shroud traps the heat on the manifold and won’t let the heat escape thus causing the manifold the inability to cool properly. There is never a problem with the left side manifold and that shroud is the only differential between the two manifolds. That hot air intake is only needed if you live in a very cold winter state or your states smog requires it. I took mine off after having to replace the old manifold and the new manifold stays at the same temperature as the left side after the shrouds removal.