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1970 GTX 440 Timing

Tony 70GTX

Tony 70GTX

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I just installed a Edelbrook 750 CFM. I feel I need to advance the timing to get more out of the carb. The secondary doesn’t kick in as soon as I would like. The Carter AVS had a better feel. I know how to advance the timing but wanted to ask the group has anyone experience this and if so how far did you advance the timing?
 
Last edited:
Why did you change the carb if the Carter felt better?

Was the timing right prior to this? Don't change it.

The secondaries are adjustable on the AVS, so adjust them first.

The carb was the only change, so just change that new carb not the other settings.
 
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Advancing timing in most situations is fine to get better idle quality and throttle response. The book numbers are garbage in most cases as they weren't optimized to performance, a crutch to meet emissions.

You have to be careful advancing idle timing as it moves you total timing number up the same amount, Stay away from pinging. It may require some distributor surgery to limit mechanical to obtain a good overall timing package

Timing won't likely change when the secondary door opens, that's a carb adjustment. Not sure but, IIRC, 750 Ede's had a bad rep for OOTB tune up/settings. Don't know if they fixed them.
 
What are your current timing settings?
 
Adjust the secondary spring. Loosen the lock screw and count the turns until the secondary blade opens, then back until it just closes. Now, many turns was that? If your engine isn't boging, the spring is a little too tight, back it off until you are happy with it. If it bogs, the spring needs to be tighter. This is how I always did it. My Dart back in the day had a factory setting of 1 3/4 turns, but it bogged, it liked 2 1,/2.
 
R413 said:
Why did you change the carb if the Carter felt better?

Was the timing right prior to this? Don't change it.

The secondaries are adjustable on the AVS, so adjust them first.

The carb was the only change, so just change that new carb not the other settings.
Click to expand...

R413 said:
Why did you change the carb if the Carter felt better?

Was the timing right prior to this? Don't change it.

The secondaries are adjustable on the AVS, so adjust them first.

The carb was the only change, so just change that new carb not the other settings.
Click to expand...
The Carter was rebuilt several times. It was time for it to be replaced.
 
Depending on what type of distributor you're using you can get an fbo limiter plate and have more initial without going over about 36° all-in. I use the 18° slot for mechanical and 18° inital.
 
turbine68rt said:
Depending on what type of distributor you're using you can get an fbo limiter plate and have more initial without going over about 36° all-in. I use the 18° slot for mechanical and 18° inital.
Click to expand...
It’s the stock distributor. The car is all original with the exception of the Edelbrock.
 
You should be able to use the plate in your distributor. There's several choices of slots to tailor it to what works best for you.
 
FBO Ignition is the limiter plate supplier.
 
Does the engine have a hotter cam? If so, 8-10* initial timing will be nowhere near enough.

img267.jpg
 
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