Using bolts instead of studs on the exhaust manifold?
08-12-2005, 05:25 PM
#1
Rennlist Member
Thread Starter
Using bolts instead of studs on the exhaust manifold?
I'm thinking of having the studs removed from the head and using bolts instead to facilitate future maintenance. Who has done this and what grade of steel is required?
Thanks,
Thanks,
08-12-2005, 05:40 PM
#3
Drifting
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I use bolts on the two outside holes and on the fourth hole back. The reason for the fourth hole was that a PO had stripped the threads. The threads were gone and I didn't want to use a helicoil somewhere that has that much heat. I was able to re-thread it for a standard size bolt close to the same size. I used a grade 8 bolt just because of the heat.
08-12-2005, 05:58 PM
#7
Nordschleife Master
The advantage of the studs is that they use all of the threads in the head. Being soft aluminum you want all the holding strength available. Getting the bolt just right to be at the last thread is a challenge. They may not all be tapped the same, either.
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08-12-2005, 06:07 PM
#8
Race Director
Originally Posted by GlenL
The advantage of the studs is that they use all of the threads in the head. Being soft aluminum you want all the holding strength available. Getting the bolt just right to be at the last thread is a challenge. They may not all be tapped the same, either.
With bolts the steel threads will be turning in nice soft aluminum. Go just a little too far and the head won't have any threads.
With studs you don't have to screw them into the head as tightly as you do bolts. When you torque the nut on the stud, you are turning steel on steel and drawing the theads tight in the head w/o turing the stud and risking stripping the threads in the head.
Make sense?
I'd much rather torque a nut onto a stud threaded into aluminum that to torque a steel bolt threaded into aluminum.
08-12-2005, 06:07 PM
#9
Drifting
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I made sure to use bolts that had close to the same thread length as the studs did, spaced out with one washer so I had some extra room to tighten.
Another advantage to studs in alum. is becasue frequent removal of the studs/bolts wears on the alum. threads causing it to strip easier. But it doesn't matter much on our cars since you have to remove some of the studs anyway to get the header out easily. That and what Geo said is why I left studs on the remaining holes. I can get the headers out by removing just the three bolts I put in and leaving all the rest of the studs in place.
Another advantage to studs in alum. is becasue frequent removal of the studs/bolts wears on the alum. threads causing it to strip easier. But it doesn't matter much on our cars since you have to remove some of the studs anyway to get the header out easily. That and what Geo said is why I left studs on the remaining holes. I can get the headers out by removing just the three bolts I put in and leaving all the rest of the studs in place.
