I have a 67 Firebird 400 that has had a pretty much complete engine rebuild. Bored, new pistons, push rods, cam. Edelbrock intake manifold with a Cliff Ruggles rebuilt quadrajet. Runs great for about 5 minutes until it gets really heated up and then wants to bog down on the top end and is difficult to restart after being shut down. It seems the carb is getting awfully hot. I've been told that using a 3/8-1/2" wood spacer to get the carb off the manifold will cure my problems. Any other suggestions?
Sounds like more of a choke issue if it runs well after start up, then runs poorly after warm. Does it run poorly at idle or at speed. Have you made sure your idle mixture is correct? What kind of fuel pump are you using? It could also be timing related, running to far advanced. There are a lot of other things to look at that can cause the problems you're having.
Using a wood/phenolic resin spacer helps, but I think you would be throwing money to the wind. Sounds like you have a problem that can be solved without spending money first.
Mechanical fuel pump and we are going to address the possible timing issue today. I have to pedal it for a minute or so when cold starting but once warmed up the idle seems to be OK.
