331 Cadillac engine question

I know this is an old thread, but do you remember what you wound up setting the floats at? They look pretty low already in your picture above.

I've been having the same issue with my 331 and Rochester 4jet. I went to lower my floats but I thought they looked pretty low already so I wound up raising them. I was able to put smaller jets in it without it breaking up at speed but I'm still having the same issue with hard starting when the engine is up to temp, even in this cooler weather.

 

I'm willing to use and enjoy more my '51 Coupe which is fitted with a Rochester on the 331 and was planning to keep it as stock as possible (easily reversible mods preferred) as I need it as a reference to restore a '51 conv... I have eventually embarked in the following steps to fight vapor lock in preparation to the coming season:
- 12" push through fan on an thermostat off the left head outlet (on 180°f/off 165°f - first test with on 190°F/off 175°f appeared too high as the problem still occured), with on demand switch, at the right of the stock radiator support
- 1/2" carb phenolic insulator (hoping it won't mess the control rods operation)
- heat wrap protection of the incoming fuel pipes (stainless replacement of the stock one)
- heat wrap insulation of the headers (esp. left side)
- check if carb heating from header can be blocked

question: would it be recommended to make a thin phenolic insulator for the fuel pump itself (1mm or 2mm so as not to empede mechanical operation), as I suspect the heat of the block is mostly acting on the pump (vaporising fuel on the pumping stroke hence nothing to push afterward then carb starvation)?

 

An insulator on the fuel pump is probably overkill. You might want to consider Olsen gaskets makes intake gaskets that are made without heat riser holes, blocking off the hot exhaust ports to the carb. I put a set in my 331 and it worked better than an insulated carb spacer. It stopped burning the paint off of the intake manifold also.

 

I would check the floats themselves to see if they are water logged. I have had many that were full of gas and would not float.

 

Will do, but the engine runs great when cold...

 

Same here on my '49.
4 -Jet on a 53-54 manifold.
6 volt NAPA pump, steel Fram filter with a return line and a 1" spacer under the carb. Made a block-off plate on the oil-fill fixture where the fuel pump was.
No vapor lock for about 99% of hot restarts.