GM Fastburn Head to Header Port Issue

[kryptik]

Hello,

I have a zz383 engine with GMPP Fastburn heads; the exhaust ports on these are "d-port." I have headers (Dynatech 1-3/4") that work well as far as interfacing properly with the "D" shape (i.e. they do not hang down and block the top of the "D").

The problem I am having is that because these headers are completely oval, they hang DOWN too far from the flange surface. Long story short, when the headers are bolted and torqued, a roughly 1/8" portion of the header primary is under-hanging the flange and is completely open and exposed. I can't do anything with the gasket itself to seal it up, and I feel that this is far too large of a gap to not worry about; it will cause a major exhaust leak, will cripple any notion of using a wide-band in the future, and may even spit fire.

My only idea is to have a qualified welder lay down a bead inside each of the primary tubes to cover up this exposed area, and then to machine the surfaces flat once more. Any other ideas/input would be greatly appreciated. I am also on a very limited time schedule.

Thanks a lot for the help everyone, cheers!

[PARKERRS]

I know your exact problem. I have the fast burn 385 crate motor in my grey car. I went through 8 sets of headers test fitting when I built the car and had the same problem with all of them.

A flange for LT-1 chevrolet heads works perfect and so do the gaskets. I had a company called Stan's headers out of Washington build a set of their try-y headers using the LT-1 flanges and all is great.

You can contact Stan's and have a set built or you could purchse a set of LT-1 flanges to weld on your headers. Or the expensive route is to go and have a set custom built. Stan's was a good cross between custom built and off the shelf. 3/8 flanges, thick tubes and great workmanship. Stan used to be connected with the original Doug Thorley designs and manufacturing in the 60's.

[kryptik]

Sounds good I'll give Stan a call on Monday, thanks for the referral.

On a side note...how do those headers fit with angle plug heads and angled spark plugs (not sure if your heads are angled)?

[72elco]

I have this same set up. zz383 D port heads. I bought the ceramic coated headman headers "D port" for it and it works perfectly. they were pricey but may be cheaper than having something custom done for you.

[CarlC]

It's very common on standard flanges to slot the bolt holes in order to move the header up. The FB heads have a raised port which makes most traditional port location header flanges have gaps.

[PARKERRS]

Sounds good I'll give Stan a call on Monday, thanks for the referral.

On a side note...how do those headers fit with angle plug heads and angled spark plugs (not sure if your heads are angled)?

My heads are identical to yours. no fitment issues at all.

[Landon]

I noticed you have a tru trac rear end in your car. How do you like it? Does it act like a tru posi, are you able to burn out both tires at the same time?

Thanks,
Landon



Hello,

I have a zz383 engine with GMPP Fastburn heads; the exhaust ports on these are "d-port." I have headers (Dynatech 1-3/4") that work well as far as interfacing properly with the "D" shape (i.e. they do not hang down and block the top of the "D").

The problem I am having is that because these headers are completely oval, they hang DOWN too far from the flange surface. Long story short, when the headers are bolted and torqued, a roughly 1/8" portion of the header primary is under-hanging the flange and is completely open and exposed. I can't do anything with the gasket itself to seal it up, and I feel that this is far too large of a gap to not worry about; it will cause a major exhaust leak, will cripple any notion of using a wide-band in the future, and may even spit fire.

My only idea is to have a qualified welder lay down a bead inside each of the primary tubes to cover up this exposed area, and then to machine the surfaces flat once more. Any other ideas/input would be greatly appreciated. I am also on a very limited time schedule.

Thanks a lot for the help everyone, cheers!