wierd 390 problem
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Senior User
Joined: Mar 2001
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wierd 390 problem
I have a 390 4bbl from a 66 thunderbird in my truck and it will not run w/ a carb spacer. If you bolt the carb directly to the maifold it idles smooth as silk and has good power and throttle responce. If I put on a 1" 4 hole factory Ford spacer it stumbles something fierce at all rpms and will not idle. There are no visible cracks or holes on the spacer and I went so far as to fill all the voids and indentions w/ JB Weld and then block sanded it flat so I have 4 perfect holes w/ no vac ports or indentions. I would really like to run this spacer for the added power and heat insulation but it will not work. Anyone have some insight as to what in the world is the problem.
Thanks
"Like a Rock"; on the sides of roads everywhere.
Thanks
"Like a Rock"; on the sides of roads everywhere.
Cargo Master
Joined: Jul 2000
Posts: 2,281
Likes: 18
From: Northern California
wierd 390 problem
You need to put a vac guage to it. If you don't have one, get one because it's a great tuning tool. The stock adapter has coolant lines running thru it and a vac line out the back, but if you've filled yours that shouldn't be the problem. I'd check for a steady vac at about 17~20 and play with the adjustment a bit, you might need a very small adjustment on the carb but I don't think that would be the problem. This really sounds like a vac leak.
I've seen some older spacers that had casting leaks and heard that DOVE actually coated some of their parts with epoxy to seal the castings. I've even seen this on older intakes, a quick coverage of clear paint might do the trick. You can also check for vac leaks with a can of carb cleaner sprayed at the base of the carb, it the idle changes, you've found your leak.
I've seen some older spacers that had casting leaks and heard that DOVE actually coated some of their parts with epoxy to seal the castings. I've even seen this on older intakes, a quick coverage of clear paint might do the trick. You can also check for vac leaks with a can of carb cleaner sprayed at the base of the carb, it the idle changes, you've found your leak.
