67 big block exhaust manifold french locks

[Dave K.]

Judging guide states french locks and spacers on cylinders 1,7,2,8 with applied sequence bolt, fresh lock, washer, manifold. Does this mean that cylinders 3, 4, 5, 6 did not have a french lock and no spacer; just the bolt and then manifold?? I want to make sure i'm following this correctly. Also was a single tab on each end the french lock bent over the bolt?

[Russ S.]

Re: 67 big block exhaust manifold french locks

Dave, That is correct. No washers on the other bolts.

[Donald A.]

Re: 67 big block exhaust manifold french locks

And just FYI, as I went through this a while back when my car was judged, the exhaust washers/spacers are an unusual size and the Paragon repros are not exactly correct. The NOS spacers are 0.127" thick with OD of 0.683" and are unplated and not stainless steel. Eight needed and difficult to find. Richard Fortier has them last I checked, and there is also an eBay seller who has them, search eBay for NOS exhaust manifold spaces.

[R N.]

Re: 67 big block exhaust manifold french locks

And just FYI, as I went through this a while back when my car was judged, the exhaust washers/spacers are an unusual size and the Paragon repros are not exactly correct. The NOS spacers are 0.127" thick with OD of 0.683" and are unplated and not stainless steel. Eight needed and difficult to find. Richard Fortier has them last I checked, and there is also an eBay seller who has them, search eBay for NOS exhaust manifold spaces.

Good information Don. Thanks for the additional specs.

[Joe L.]

Re: 67 big block exhaust manifold french locks

Judging guide states french locks and spacers on cylinders 1,7,2,8 with applied sequence bolt, fresh lock, washer, manifold. Does this mean that cylinders 3, 4, 5, 6 did not have a french lock and no spacer; just the bolt and then manifold?? I want to make sure i'm following this correctly. Also was a single tab on each end the french lock bent over the bolt?

Dave------


Actually, I believe that at some point in the 1967 model year, if not from the outset of the year, the french locks were replaced by special flanged head locking bolts. GM #3909821 which are still available from GM (although not with original headmarkings).

[Dave K.]

Re: 67 big block exhaust manifold french locks

Thx guys.....much appreciated

[Dave K.]

Re: 67 big block exhaust manifold french locks

oops! One last question. I see it does not call for an exhaust manifold gasket? Is it still best to put one on and if so how big of a hit in points will i see??

[Joe L.]

Re: 67 big block exhaust manifold french locks

oops! One last question. I see it does not call for an exhaust manifold gasket? Is it still best to put one on and if so how big of a hit in points will i see??

Dave------


Not necessary unless manifolds are warped which is usually not a problem with big block manifolds. Check the manifolds with a precision straight edge. If they are warped, your best bet is to have a machine shop surface them.

By the way, for aluminum head big blocks I do like to use gaskets but not the ones you're thinking of. I like the multi layer steel (MLS) gaskets used on late model GM 8.1 L big blocks.