Carb tuning and timing

JayBar · #1 (**permalink**) 08-02-2005, 05:53 PM

Well it all started when I pulled my distributer to prime the oil system, after installing an oil cooler. I lost the timing mark on the distributer. Cranking the engine the first time produced a few large back fires through the carb. I then retarded the spark and the car started. I played around with the timing and finaly got it (I thing) at 32 degrees of advance. Then the idle seemed to be higher than before so I turned it down a bit to 800-900rpm. At that speed it sounds great and shakes the car in the "badest way". Then I played with the 4 corner idle mixtures. BTW the carb is a HOlley HP 750. And I noticed a strange thing. No mater what I did to the mixture screws nothing happened to the idle speed. This was not the case when I first tuned the engine. I could stall the engine by not backing out the mixture screw fast enough. I also re-gaped the plugs at .50 they were .40.

Now when I drive along after the engine warmes up the car starts to pop out the exaust at a steady cruse. Not constant just now and then ,it is comming out of the right side only.

I am thinking several things. One I know the rotor and cap need replacing they are MDS. Then maybe the backfires through the carb blew out the power valves hence negating the function of the idle mixture screws (thought I don't know why). It there a way to check the power valves?

Engine 408, cam 336/348,112spacing,.575/.595. Edelbrock performer manifold.

Any suggustions?

blykins · #2 (**permalink**) 08-02-2005, 05:57 PM

The initial time is 32 degrees? That's extremely too high.....needs to be 12-16 degrees.

You need to make sure the distributor is installed correctly....and the timing is set correctly.

Pull the dizzy, pull the #1 spark plug, stick your finger in the hole and turn the engine over until it blows your finger out....

The timing pointer should be pointing at 0 on your balancer.

Put the dizzy back in....point the rotor at the #1 plug wire as you're installing it....

Make sure the firing order is correct...

13726548 for a 351W firing order....

blykins · #3 (**permalink**) 08-02-2005, 05:59 PM

OK...sorry....I see that you put 32 of advance in there...

What's the initial?

You should check that the distributor is installed correctly, with the correct firing order....

lovehamr · #4 (**permalink**) 08-02-2005, 07:51 PM

Jay, I'd bet that when the engine backfired through the carb it blew the power valve. This would explain the insensitivity to the idle mixture screws (extra fuel from the PV), the shaking idle (grossly rich mixture) and the exhaust popping (raw fuel lighting off). This problem is one of the reasons I switched to the Demon.
Steve