Downey/Mark Header on a 1981 2f (1 Viewer)

[martymart]

I had a Downey/Mark A. Header on my F engine and it mated fine. I am swapping in a 1981 2F engine. As I was bolting up the header to the 2F, the bottom of the manifold does not mate to the block because the manifold sits on top of the header where the 2 bottom studs are. It appears that I need to shave quite a

bit off the manifold to cleaner the header. Before I do that and potentially make a fatal mistake, I would like to confirm that cutting off some of the bottom lobes on the manifold is the correct action. I am using the 1981 2F manifold.

 

[martymart]

I had a Downey/Mark A. Header on my F engine and it mated fine. I am swapping in a 1981 2F engine. As I was bolting up the header to the 2F, the bottom of the manifold does not mate to the block because the manifold sits on top of the header where the 2 bottom studs are. It appears that I need to shave quite a View attachment 3671433bit off the manifold to cleaner the header. Before I do that and potentially make a fatal mistake, I would like to confirm that cutting off some of the bottom lobes on the manifold is the correct action. I am using the 1981 2F manifold.

 

[martymart]

View attachment 3671434

 

[charliemeyer007]

I made my own brass stepped washer instead of using 1/2 washers to compensate for the different thickness in the manifolds. I posted pic's before. I think mine is a man-a-fre.

 

[Toyoland66]

I would trace the overlap on the header flange and clearance the header with a grinder before modifying the intake.

 

[martymart]

I made my own brass stepped washer instead of using 1/2 washers to compensate for the different thickness in the manifolds. I posted pic's before. I think mine is a man-a-fre.

Thanks, that’s what I did with the F. In this situation, it’s not the thickness but the manifold sits on top of the header flange. As a result, the manifold cannot press against the block without cutting the manifold or header flange.

 

[martymart]

I would trace the overlap on the header flange and clearance the header with a grinder before modifying the intake.

Thanks for the advice. It makes better sense to me to grind the header over the manifold.

 

[Green Bean]

Just my 2 cents: I believe that the header flange material is stainless and is a harder metal to grind/shave. On the other hand, the manifold is aluminum and is softer and therefore easier material to work with?

 

[60 40]

Grind the header then the stepped washers or half washers will have equal bearing on it and the intake manifold. The header is an aftermarket product it should be modified rather than the stock components when possible.

Edit:

That being said when I fit my Downey header that I used on my '69 F to my "new" '83 2F and used the '69 intake it had enough clearance that I did grind the intake flange slightly but was still able to get a full 1/2 washer of purchase on it.

 

[65swb45]

Martin, that was one of the issues with the Downey header when I took over production.

I have a very specific memory that by the last batch of headers that were done under my supervision, I had the bottom of the flange made lower so that the flange could be cut instead of grinding the intake while keeping the flange stable. The batch of flanges that I sent to the new guys when I stopped making them had that change incorporated.

I am NOT implying that cutting the header flange will make it unstable. I just chose not to find out, knowing how prone headers in general were to leaking.

 

[martymart]

Thanks all

 

[brian]

Just my 2 cents: I believe that the header flange material is stainless and is a harder metal to grind/shave. On the other hand, the manifold is aluminum and is softer and therefore easier material to work with?

nah its carbon steel

 

[martymart]

Grinded the header flange just enough to fit the manifold flush with the block. Again thanks.

 

[gonzopancho]

The batch of flanges that I sent to the new guys when I stopped making them had that change incorporated.

We still have them, too. (the new one is stainless.)

 

[Fe3]

We still have them, too. (the new one is stainless.)

Let's make it easier for future searchers:

TriMeki 2F/F Stainless Steel Header & Exhaust System - https://forum.ih8mud.com/threads/trimeki-2f-1f-stainless-steel-header-exhaust-system.1337067/