Carb/Timing issue??

[RivalThreat]

So, I just bought my 72 351c 4v,with edelbrock 1406 600cfm carb not too long ago and have been trying to get it dialed in and im thinking I have some timing issues.

The distributor vacuum advance is ported through the carb but at idle if i remove the hose it bogs down like its going to die. From what i understand a ported advance vacuum to the carb should only be affected when RPM increases. is this correct?

If so, does this mean I have too much initial timing causing the advance to be used at idle? I did notice the carb idle screw is turned pretty far in as well pushing the throttle linkage a good amount. so im suspecting the carb may be tuned a bit screwy as well.

Any suggestions on what I should do or how to fix this?

Some things to add-

Starts right up every time, occasional trouble when hot and trying to start.

seems to run ok, doesnt lag too bad when accelerating but seems like it doesnt have as much power as it should.

Id appreciate any help I can get. Im fairly new to all this and trying to learn as I go.

Thanks!

 

[72HCODE]

Correct ported is zero at idle. It means the butterflies are open too far . Sometimes the secondaries need to be adjusted down.

Initial timing would not cause this, can cause other problems.

The mechanical advance works off Rpms. So if the idle is high it can kick off the mechanical especially if somebody installed a set of mr gasket light springs inside the distributor.

Vaccum advance again should be off at idle and have no effect.

Too much initial can reduce vacuum or cause ping/detonation during acceleration.

The idle air bleed screws could be out of adjustment ,too lean that can cause high idle.

First if you don't have a tach setup dwell/tach/voltage meter in the engine bay so you can see what Rpms you make at idle, install a vaccum gauge and see what the engine is making at idle.

It's possible somebody messed around with the carb and through all the setting off.

You should check initial timing as well. You want to set the idle barely running for initial timing check to make sure the mechanical advance is not kicking in, unplug the vacuum advance and cap the carb port for testing. Then test a reading with a timing light. Every motor is different and there are different opinion on initial timing depending on your cars cam. But if somebody advanced it over 20 that isn't good.

It's hard to diagnose over the internet so you want to take some initial readings and it would be a good idea to reset the carb if it is out of whack. Idle bleeds set to 1.5 turns, close the butterflies Down so the idle circuit is exposed but not the transition slots. Balance the primary and secondaries so they are open the same amount at idle.

Other problems could be a vaccum leak somewhere, ignition problems, plug gapping.

A lot of this will become trail and error because you don't know what the previous owner did to the car or if it ever ran correctly.

As for hot starts most cars have problems. Usually it's when the car is in between fully warmed up and cold. Or when a car sits for a half hour and you get some heat soak. This is not a modern car so some pedal fiddling is expected , just feather the throttle when starting and it should start up.

 

[RivalThreat]

Thanks alot! I really appreciate it. It gives me a place to start. As far as resetting the carb, is there a good source out there for the how to? Youtube? Just download the manual?

 

[c9zx]

Download the manual here. http://www.edelbrock.com/automotive/misc/tech-center/?query=1406&submit=search

Chuck