650 DBL on a 318 help - Moparchat

Aspenj2002 · #1 07-21-2005, 10:48 AM

Here's a Q for you tuning wizards. Just took a well performing 750 vac off a very strong 318 of unknown history and put what appears to be a brand new 650 dbl pumper(Holley) and it runs poorly now. I know check the floats and make sure no vaccuum leaks and all that-but what I was hoping to find out was if anyone has a street 318 with a 650 dbl and if so what was the final jetting, shooter size, timing etc. Incidentally all of this is in a 74 Duster with auto,3.55 headers. I know someone here can direct me in the right direction. Thanks in advance. J.

dart joe · #2 07-21-2005, 02:11 PM

650 dp i think came with 66/76 jetting, PV up front, was the carb rebuilt, if not, i would throw a kit in it and clean it thoerally, there's a posability that it might be too much for a 318, maybe not, i would say if you had a 3000+ stall and 391 gears it will work better.

dart joe · #3 07-21-2005, 02:14 PM

They came with either 25 or 28 squirters F@R and 30cc pumps.

pishta · #4 07-21-2005, 04:37 PM

Move all the jets and 1 shooter from the 750 over to the 650 and see if it behaves any better. I would stick with the 750 vacuum. the vac secondaries let you run an apperantly larger carb than needed.

dwc43 · #5 07-22-2005, 02:54 AM

I agree with Pishta. The 650 is way too small and it will have much more power with the 750. It would perform even better with the stock carb which is an 800 cfm Thermoquad. We use the big block TQ carb on our 360 race cars which rates at 850 cfm.

rumblefish360 · #6 07-22-2005, 09:50 AM

I have found DP carbs a little bit of a pain in the rear on auto trans cars. Vacumm carbs work better
Why the move to a smaller carb?