Eliminating Hot Spot?

Posted by Mike On 2011/5/25 15:04:12

Hi...i'm taking the 2 bbl manifold and carb off my 327 and am getting ready to prep the 327 4 bbl manifold. I'm going to take it apart, have it blasted, new hot spot gasket, painted or powder coated, and then reassembled and have the faces milled flat.

I did the same to my 2 bbl manifold (save the milling) and noticed lately that once the car is good and hot (not a 15 minute drive, like a 40 minute one) it rolls over fine but won't fire. I have 3-4 psi fuel pressure at the carb when this happens, and have the insulating spacer and new gaskets, etc installed and have the little exhaust flapper valve connected with a spring to always keep the exhaust routing directly out without hitting the manifold.

The thing is, i noticed that even in that position a fair amount of exhaust works on the hot spot, and i'm wondering if the fuel just isn't vaporizing as soon as it hits that when being squirted in with the jets when trying to start it. If there's a chance to work with the hot spot, its now before i have machine work done.

I was thinking of making a plate that pretty much matches the hot spot gasket, solid about 1/16 in thick, and putting a gasket on each side of it sandwiching it between the manifolds to block off the hot spot more solidly. I figure i'll have to have the thickness of the plate and extra gasket milled off one of the hot spot surfaces so that the intake and exhaust ports on the face aren't on a different horizontal plane after adding something so thick in.


Does anyone have any experience with this or other similar ideas? Do you think it would make any difference or do you think the intake side of the hot spot is just going to hit that temperature no matter what and it won't matter? Or maybe the 4bbl isn't as prone to this issue for some reason or i should look at mixing diesel in as some have done?


I don't believe i have a pump/line/tank issue, with good pressure at the carb and a full bowl of gas with 3-4psi behind it, vapor lock in the line can't be a culprit in my mind.

Of course, it could be ignition i guess which i'm working on, but then i don't think it'd be as easy to start cold as it is (it fires RIGHT up.)