Back before todays crap fuels you wanted the fuel to vaporize so you didn't have raw fuel going into the cylinders, that caused cylinder washing that removed oil from the cylinder walls if I remember. Fuels were also blended with stuff to prevent boiling.
Todays engines with fuel injection and computer controlled don't require that type of fuel, it seams the crap now boils and vaporizes on a good warm day :-). Just my theory and I have nothing to back it up..

I was recently reading an automotive text book published in 1946. It states that a intake manifold "hot spot" is desired for fuel vaporization....is that no longer true?

 



"FREE SAMPLE"

The material I use for making the exhaust crossover block offs is 0.010” thick.  That’s exactly the same thickness as the restricted tin plates that come on the Best Gasket intake gaskets.  Blocking off the heat riser passage is customary on those engines where you are wanting to keep the paint from burning at the intake manifold crossover.  The block offs only affect cold weather startups/driving and once the engine is warmed up, there are no other adverse effects.

Lorena, Texas (South of Waco)

With the restricted truck style gaskets & a phenolic spacer it should be o.k.  As suggested, there may be something else going on there.  A possiblity is that the carb is leaking into the manifold after shutdown. I had that problem with a Holley 2300-2 Bbl. Ted put me on to checking the orfices behind the float bowl for being plugged up. They were. Carefully cleaned them (no reaming) & no problem since. Likely caused by old fuel & sitting for long periods.. And is your heat riser opening properly, if you have one?


Paul

Thanks Ted. About how thick are the plates you use?

Durham Missouri

I use a couple of solid tin plates on top of the intake gasket crossover port.  These I put a small 90° lip at their tops so they stay in place while laying the intake in place.  If using the Best Gasket intake gaskets, then I remove the existing ‘restricted’ tin plates that are on the gaskets and use my fully blocked ones.
 

Lorena, Texas (South of Waco)

I live in Northeast Missouri. Summers get pretty warm here also. I think the biggest problem is what Miker experienced also. I was hoping blocking off the crossover and a phenolic spacer would help to alleviate the problem. As far as fuel I only burn 91 octane non-ethanol.

Durham Missouri

I use the restricted gaskets here in Atlanta.  That's up to around 100 degrees in the summer, so for most people they should do the job.

Do you have a spacer?  If not, try a spacer.  Phenolic spacers are available as thin as 1/4".  Edelbrock make a gasket that is 3/8" thick.

Also make sure it is not some tuning or ignition issue.


Lawrenceville, GA

That's a pretty common problem in my experience. Both my cars do that parked with the hood down. Then I noticed at a show where the hood was open, it didn't happen. I haven't found a cure, I'm inclined to blame it on the ethanol and Reid (?) vapor pressure of modern fuel designed for use in fairly high pressure EFI systems. I know it wasn't a problem way back when. Vapor lock when driving seems more common too in our old cars.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

That might have more to do with that shit fuel you guys have.?  Sounds more like you need the heat if its not idling well until it heats up.
 What state are you in ?



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