Engine stand exhaust mounting question

[corvette8n]

Ok what size are the 4 outer exhaust holes supposed to be I'm trying to mount a '40 flathead to an engine stand and have the exhaust bracket. I looked through my coffee can of bolts but not finding anything that fits. Holes are scaly and rusty, can I retap them if so what size and pitch? Thanks

[Ken/Alabama]

7/16 coarse thread. That applies to the front two only. Rest are 3/8

[flathead4rd]

Don't use a tap on them. Use a thread chaser.

[Ford Freak]

Originally Posted by flathead4rd

don't use a tap on them. Use a thread chaser.

x 2 !!!

[corvette8n]

Thanks Ken, I just ordered one of the Sears thread restorer kits.

[cas3]

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a regular tap is just fine on those exhaust bolts for me, they are not special thread like the head bolts. bottoming tap is best, or grind the end off an old one if you a few.

[Phil Gillespie]

Originally Posted by cas3

a regular tap is just fine on those exhaust bolts for me, they are not special thread like the head bolts. bottoming tap is best, or grind the end off an old one if you a few.

Agreed, not a special thread. I also have bottom taps for the job.
Always wondered why the 7/16 for the front 2 and 3/8 for the rest?


Phil NZ

[V8COOPMAN]

One still needs to be careful when running any thread-restoring tool ALL THE WAY down to the bottom of those holes. It's very easy to poke into a water jacket when cleaning-out those holes. DD

[Ken/Alabama]

Originally Posted by Phil Gillespie

Agreed, not a special thread. I also have bottom taps for the job.
Always wondered why the 7/16 for the front 2 and 3/8 for the rest?


Phil NZ

My thoughts on that are the fact that the early ,32-36 , exhaust manifolds have the exit port at the front of the manifolds and those front holes had studs in them that were long enough to also accommodate the exhaust pipe flange. I think that's the reason for the larger 7/16 holes.

[Phil Gillespie]

Originally Posted by Ken/Alabama

My thoughts on that are the fact that the early ,32-36 , exhaust manifolds have the exit port at the front of the manifolds and those front holes had studs in them that were long enough to also accommodate the exhaust pipe flange. I think that's the reason for the larger 7/16 holes.

Yes Ken that makes very logical sense for sure.
Phil NZ