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Mon Jul 28, 2025 5:35 pm

Challenge: despite test fitting all the tins prior to final assembly, I now discover that its impossible to install my cast dual carb intake manifolds because the opening for the intakes in the tins is too small.

I "massaged" the metal until the tins will accept the manifolds.

Now, the round spark plug openings are more egg-shaped, and it is impossible to put a spark plug socket on the plugs as the now-deformed bottoms of those openings now block access at the right angle to get it on the plugs.

I'm sure I'm not the only one who has encountered this!

Solutions? cut off the bottoms of the spark plug holes? Makes me wonder if it matters since the pub wire boots don't seal to those holes even without modification

Below is a pic of the modded tin. I have circled the areas that interfere. Open to suggestions.

Mon Jul 28, 2025 5:55 pm

Depends on the manifolds, but I usually end up removing about 1/4" off the manifolds on the inside face. Looking at the ports in your heads, you can probably remove 3/8" from the manifolds.

A little more tweaking, slitting, and bending on the tin will get you the rest of the clearance you need. The plug holes can usually stay complete.

Brian

Mon Jul 28, 2025 10:53 pm

I have the same problem and I end up just trimming them with a pair of snips.

Tue Jul 29, 2025 2:39 am

I use a piece of aluminum rod and a hammer to "massage" the tin until the manifolds fit. I use a scrap head when clearancing the tins and then test fit on the engine.

Tue Jul 29, 2025 10:54 am

Here is a pair of aapiston idf offset manifolds i ground the insides to clear the tin. They just drop on now, no need to beat on the cylinder tin. Probably took off a 1/4"