The Stovebolt Site Forums The Shop Area Engine Shop Chevy 235 exhaust manifold dowel pin question

Hello,
So just wondering since I've seen pics of 235's with the exhaust end dowel pins removed and bolts in place, I assume the dowel pins aren't threaded in there are they? Also how did you gents get them out? Just with a pair of vice grips or do they have to be drilled?

Thanks for any help!
Have a set of Williams headers and a Clifford 4 barrel intake I'm installing and want to be able to bolt down the ends of the manifolds.

The dowels are threaded same as the other manifold bolts but shorter. I used vice grips to turn mine out.

Threaded yes. ViceGrip's..... They should turn out since they
are not torqued down like a bolt would be.

dg

If you take your intake and exhaust (torqued properly together with the gasket) to your machine shop, they will mill the surfaces to perfectly straight. Then you don't need to add more bolts. I paid $46 for that here in Kansas. I wouldn't change the configuration. Chevy didn't feel the need.

I am willing to bet that Chevy felt a definite need to use dowels instead of bolts. With such a long cast iron manifold, there is a lot of heating and shrinking going on, and the dowels may be there to allow for movement without cracking.
Carl

I won't buy that one Carl. To many other bolts restricting the movement.
My guess is that it was an aid in the assembly. The line
worker used the pins as a guide when installing the manifolds.
I've really never seen much of a problem with not having the
ends bolted down. Now blowing out the gasket at the bottom
flange where the cobs come out....that's another story. I'm
replacing the exhaust pipe flange gasket about every few months.
Oh yeah, our new guy isn't using the stock manifolds, remember?
He's installing Williams headers and a Clifford 4 barrel
intake, taint connected together.
dg

Good speculation about why there are exhaust manifold studs at the end of Chevrolet Stovebolt engines' heads.

How do these theories explain why the same vintage/era GMC engines (228/248/270 and probably 302) had bolts or threaded-studs/nuts instead of studs?

"Threaded-studs/nuts instead of studs" makes no sense.

There are bolts they are threaded and head tightens bolt.

There are studs they have no head and need nut to tighten.

Explanation:
1. Weren't as many GMC's made as Chevy's so they had more leisure time on that production line.
2. GMC's were made heavier, stronger more durable than the Chevy
so more effort went in to making it that way.
3. GMC's cost more that a Chevy so they didn't have to skimp
on the cost of a bolt head. It's been the subject of discussion
many times of how Chevrolet Motor Division was full of penny pinchers.

dg

"threaded-studs/nuts instead of studs"

Oops, I meant "had bolts or threaded studs/nuts instead of dowels".

Thanks for the correction.

I was not trying to correct just thought I was missing something. Jeffrey

Jeffrey,

Corrections and questions are good things. No sense scratching our heads now (or, in the the future, when a new reader/member wonders about the contents of a post).