I have been reading old posts about cracked exhaust manifolds and upgrade headers-I welded what I could reach on mine and smeared never works band aid stuff on the back side-it's cracking in a new place now and evident I need to pull it apart. I am an experienced welder but I know eventually it will crack agian next to the repair-I am asking for advice-I dont want to do this more than once. has anyone tried re-enforcing the area prone to cracking,and if so does this simply move the problem ,creating a weak link elsewere? I'd like to get away with only having to buy new gaskets,but thinking I may be ahead by just ordering a better design and call it done.this is an'88 limited with 215000 miles-I am planning on keeping it at least one year,and perhaps more if it continues to be reliable. so-anyone had luck fixing the OEM? or advice on aftermarket choices? thanks,Steve
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manifold debate
- Thread starter xtp45lc
- Start date
8Mud
NAXJA Forum User
- Location
- Central Germany
My welds used to last a year and a half, maybe a little longer if I was lucky. They'd usually crack again right next to the weld.
I relax the welds with a torch after MIG now (faint red about 600 F) and let them cool slow. The usually last 3-5 years.
Next time I'm going to try a softer wire, something with a high nickel content and see how it lasts.
A friend said he brazed his cracks shut and it's been holding up well. The early Renix headers are an alloy, steel, copper and perhaps a bit of nickel. I've done enough welding to spot the signs and how the metal reacts to heat, softer welds may actually hold up better.
I also use a large thick piece of flat stock and clamps to keep the exhaust manifold straight while welding. I made the mistake of welding and then not having the bolt holes and pins line up, I had to stress it to install it.
I relax the welds with a torch after MIG now (faint red about 600 F) and let them cool slow. The usually last 3-5 years.
Next time I'm going to try a softer wire, something with a high nickel content and see how it lasts.
A friend said he brazed his cracks shut and it's been holding up well. The early Renix headers are an alloy, steel, copper and perhaps a bit of nickel. I've done enough welding to spot the signs and how the metal reacts to heat, softer welds may actually hold up better.
I also use a large thick piece of flat stock and clamps to keep the exhaust manifold straight while welding. I made the mistake of welding and then not having the bolt holes and pins line up, I had to stress it to install it.
beakie
NAXJA Forum User
- Location
- Ontario, Canada
another option is to add the flex pipe inline before the tranny mount. I put one on mine months ago after investing in a Banks header. The torque flex from the engine can't help an exhuast system that isn't designed to flex at all.
5-90
NAXJA Forum User
- Location
- Hammerspace
xtp45lc said:
While you've got the header off, may as well replace all of your engine mounts (two on the engine and one on the transmission.) If you've an engine mount going south on you, it can take out your header - there's no flex built into the system. If you just replace one or two mounts, the leftover old ones will help your new ones fail prematurely...
It seem a lot of "cracked header" complaint have involved failed/failing engine mounts - either directly or tangentially.
You can also expect some difficulty in finding a replacement header for a RENIX rig - I'm not sure where to get one. Since the RENIX has that damned EGR valve, you have to have provision for the lower end of the tube in the manifold.
5-90
NAXJA Forum User
- Location
- Hammerspace
falcon556 said:
Poly does transmit more vibration into the chassis - meaning more engine noise. However, they're a more rigid mounting and are somewhat less susceptible to breakdown as a result of exposure to petroleum - so it's a decent compromise. A more rigid mount is important in performance applications - the more the engine is allowed to twist in its mountings, the less power makes it to the rear wheels. Fix the engine in place, and you get more torque transmitted. Poly is a nice compromise between allowing for flexion in the engine mountings and having solid steel brackets (and therefore a fully rigid mounting.) Most people are just whimps, and don't want to feel their engine running - although I would usually prefer it, myself. I like to know that something is happening under the hood...
