Will be installing a new intake on the car. Cast aluminum with a 4bbl carb. Street car meant for fun. Never driven in the cold. Should I block off the exhaust crossover? How do you block it off?
For a street car that will get driven on cool or cold mornings I recommend you leave them open.
The car will "warm up" and drive normally much faster than if they are closed off especially with an electric choke.
With the passage closed off the electric choke may open fully before the intake is fully warm and it will run a little "boggy" for a bit.
With a manual choke it is not a big deal just wait longer before opening it all the way.
Less pronounced on an aluminum intake - more pronounced on the factory cast part.
I also use the valley pan on street driven cars for the opposite reason. Helps keep the manifold cooler once everything is up to operating temperature. Less vapor locks and better performance.
If you need to close them just cut 2 squares out of a beer can and cover the holes on each side - glue them in place with gasket cement. They go against the head and everything else goes on top of them.
Not a big deal either way - just seems to be more well mannered with them open on a street driven car. (in my humble opinion)
You may have read my post on the subject where I needed to block off the cross over passages on my cast iron manifold, because my Holley carb was percolating fuel when hot causing poor performance. If you are still using an Autolite 4300, that carb was designed to run with the crossovers. I also added a 1" thick fiber spacer to keep the carb cooler. This has proven to be best for my car. I have had no cool start issues in that regard.
I do tend to ere on the 'overkill' side of things, so there are other alternative that will work....... but for how long? I certainly would not use a beer can, the heat would blow through the aluminum in a heartbeat. Use .020" steel, the thickness of the paper valley pan gasket and cut it and the gasket, to fit slightly larger than the opening, glue it in place with sealant so it stays in place during assembly. Buying gaskets with the plate inserted would be an easier approach, I just didn't have them. As for the manifold, I used a Dremel with a 1/8th" flat bottom burr and CAREFULLY cut a step .080" deep and about the same per side wider, then cut 1/16th" SS plates to fit. Use a sharp center punch to "stitch" ( several indents close to the edge of the plate) the plate in place. I used some exhaust repair paste to seal them off. Told you I tend to ere on the overkill side!! Anyway, my engine suffered other issues and when it was stripped after the passages block-off plates had been in service for about 2000 miles, there was no sign of leakage or burning. I also still use the carb base gasket with the steel insert that would be used with the Autolite 4300.
I forgot to emphasize that I did this on an original cast iron manifold, an aluminum might need a different approach. I guess gasket with inserts built in would be best for this.
These are old school beer cans with the pull tabs. We only have aluminum now. I'm not planning on using, just pretty funny he brought up the old steel ones and I quite a number of them in my basement from an old collection.
We're way of "topic" but this is fun!! I grew up in England where beer was beer and served at room temperature, well, actually cellar temp of about 45 deg. and from "the wood" (barrels). No cans that I remember, just glass bottles. I do seem to remember some cans in the early 60's as we had several USAF bases nearby and the "Yanks" had them at a party at my brother's house.
