Hesitation after burnout.

[Blind Squirrel]

Spark Plug Heat Range Explained

Also, and I could be wrong. But studying the picture you provided. It appears you're pulling vacuum for your distributor from the wrong place. I can't seem to blowup the photo on my junk laptop here.

 

[Hansen]

Spark Plug Heat Range Explained

Also, and I could be wrong. But studying the picture you provided. It appears your pulling vacuum for your distributor from the wrong place. I can't seem to blowup the photo on my junk laptop here.

I need to check my plugs for hot or cold type..

drawing vaccum from the metering block to the distributor, not the throttle body.

 

[Demonracer]

If you are pulling vacuum from the metering plate, that is ported vacuum. From the throttle plate is direct vacuum, I always ran mine with direct vacuum. Also, if you have timing problems, check the power valve it may be blown.

 

[Blind Squirrel]

drawing vaccum from the metering block to the distributor, not the throttle body.

Yup, that would be the incorrect place. Pulled vacuum for your brake booster and vacuum advance come off carbs base in most cases.

I have seen brake booster pull straight from manifold. Why, I have no idea. But I have seen it.

 

[Demonracer]

Brake booster require direct manifold vacuum to operate properly. Anything other than that can disastrous, LOL.

 

[Hansen]

Yup, that would be the incorrect place. Pulled vacuum for your brake booster and vacuum advance come off carbs base in most cases.

I have seen brake booster pull straight from manifold. Why, I have no idea. But I have seen it.

Could this damage anything if not switched to manifold? Looked it up and it seems like i can't have manifold advance if i have a vaccum that's not stable due to bigger cam.

 

[Demonracer]

No damage to speak of, but I always put a "one way" vacuum valve in the vacuum line.

 

[Hansen]

Brake booster require direct manifold vacuum to operate properly. Anything other than that can disastrous, LOL.

I will try to switch distributor to see if there's any difference.

 

[Demonracer]

Check your direct vacuum port with a vacuum gauge at idle & at operating RPM to see what you end up with.

 

[Hansen]

Solved! The distributor was rusted up on the weights inside. Cleaned and greased it a little and now its gone. And the 670 works fine

 

[Nat]

Update: fixed the distributor to 34 degrees but still had hesitation. pulled the 670 vaccum secondaries holley, and put a 600 double pumper. works very good again.

But now; what is wrong with the 670? any way to test these?

put a lighter spring in the vacuumsecondaries , i had that problem with my 340 and 670 played with timming and vacuum secondaries , worked well afyter that