Installed new Holley Carb

Cobra 29 · #1 (**permalink**) 10-25-2009, 05:10 PM

I finally replaced my 4777 DP with a new 82651 DP. Both are 650 CFMs but there seems to be a world of difference. The install was easy since both where 650 DPs. The initial settings from Holley seem good. I used a vaccum gauge to set the idle mixture.

I was planning to continue to run the 4777 and remove the choke tower but I think I made the better decision.

Any things to check besides gas leaks? I will pull the plugs later to check the main jetting / running mixture.

patrickt · #2 (**permalink**) 10-25-2009, 05:43 PM

Of course you should set your floats by removing the sight plugs. What will be interesting is seeing how many forum members do that with the engine running, how many do it with the engine off, and how many have had a fire under their hood.

Cobra 29 · #3 (**permalink**) 10-25-2009, 05:52 PM

Since I have an electric pump, I checked the level with the pump on and engine off. The level was immediately below the ports. Should the engin be running or is that only required if you have a mechanical pump?

patrickt · #4 (**permalink**) 10-25-2009, 05:55 PM

Having an electric pump is cheating.

Holley says to do it with the engine on and running, but most of us have seen an occasional fire, so a lot of us do it with the engine off so we spill as little gas on to the primaries as possible.

We'll probably get a couple of posts that say the only way to correctly do it is with the engine on and running, and wiggling on the mounts, and spilling gas on the primaries.

patrickt · #5 (**permalink**) 10-25-2009, 06:12 PM

Typical thread from the FE forum on "should I adjust my floats with the engine running or off?" http://www.network54.com/Forum/74182...+fuel+bowls%29

Gunner · #6 (**permalink**) 10-25-2009, 08:24 PM

I just replaced my 4160 (750 CFM) with a Barry Grant Speed Demon 750. Besides all the other advantages, it has glass float bowl sights, so I can set the float levels with the engine running and no splashing gas.

I took the jets down two steps but am not sure it was necessary. Had some detonation but discovered I had almost 25* of initial timing instead of 15* (don't ask). Backed it off to 15* initial and will see how it plays tomorrow. Much crisper throttle and none of the Holley's bogging.

*13* · #7 (**permalink**) 10-26-2009, 07:51 AM

Demon makes a nice carb. I set up & ran one a few years back on a BB Chev I had. It was a definite improvement over the edelbrock it replaced. The car was geared so tall that I ended up running a 600 Holley DP on the Motor. The smaller carb had much better low end response & since the engine(behind an automatic) never revved it didn't need the larger CFM. A 600ish CFM Demon would have been even better! But free is tough to argue...