1967 440 hp motor if I put the exhaust block off intake pan will my engine bay, carb, intake be cooler will it effect performance thanks mark

So I assume you used Felpro # 1215 valley pan gasket?
It will make you carburetor cooler by not getting the hot exhaust gas up to it and then in turn less likely to vapor lock. The down side is your choke won't work properly in the winter months unless it's an electric carburetor mounted style.
Ron

Don't mean to high jack the OP's question here but....I was thinking of doing the same thing to my motor. Here's my question: Seeing valley pans are not made out of the thickest material, how long is it going to take before hot exhaust gases burns a hole thou its thin metal? Or won't that happen. Anyone ever had this happen to them? Thanks.

I just fill the ports with JB Weld, about a 1/2" thick "plug" and never had one burn thru.

Just mix up a batch of JB, pour it in one crossover port, put masking tape across the port and prop the intake so that the surface is flat on the table and let it set. Gravity will let the epoxy flow down too the tape and seal the port. Once that side is setup, do the other side. Done. On an LA I generally use one, two part kit of JB Weld per side.

marcjames --> I agree with RJS
BlueRacer69 --> the hot exhaust gases are not even close to being hot enough to burn through the valley pan "block off", thin metal.

My brother fills them with a zinc alloy and then cleans the port back up. On other heads, such as Oldsmobiles, that cross over opening is very large and worth the effort to fill it on a hot rod motor.

The head has to be pre-heated and the zinc has to be heated with a acetylene torch. The head usually gets warped from the heat and will need to be decked. No big deal if your rebuilding oem heads from scratch, but if you have good usable heads to begin with most don't want to do it this way.

Cut a piece of stainless same thickness of valley pan. Cut the hole larger to fit the new piece. Fill up the intake with tin foil leaving about an inch from the edge then fill with high temp (red) silicone is another way.

Wow.

I just use the valley pan without the crossover opening. Never had a problem.

At one time I'd fill the intake with duroglass and use the block off gasket. Overkill, gasket works fine.

do it the hard way.

Wow, a lot of work some people put into this. For my small block I used thin gauge sheet of hobby brass (nothing special) from Lowes. I cut it a little bigger than the opening in the gasket, stuck it on with RTV to keep it in place while I torqued down the intake and was done. Years later pulled off the intake, wiped off the little brass plates and they looked like the day I installed them. In fact I reused them when I put the motor back together.

Combustion does generate water. If your block offs are burning through, its probably more like they rusted through and got sooty looking once the hole was already there.

https://www.summitracing.com/search/part-type/wheels/department/wheels-tires/wheel-material/steel?N=4294920860%2B4294950865%2B4294920356%2B4294566455%2B4294920856&SortBy=Default&SortOrder=Ascending


Wow, it’s not rocket science. Just buy the valley pan with the block off.

No need to complicate the crap out of it.

I've never had the felpro valley pan burn through.

And you never will !!

Good info about the Felpro valley pan. That's what I wanted to know.