GM HEI centrifugal advance blocked ?? - Team Camaro Tech
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post #1 of 6 (permalink) Old Jul 16th, 09, 03:29 PM Thread Starter
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Chris
 
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GM HEI centrifugal advance blocked ??

I'm into changing the weights and springs in a GM HEI on my '69, due to finding I can only get roughly 5* centrifugal advance.
the initial is already locked full advance, (prior owner~thing), so my balancer-best * for cool idle and easy starting has been 17.6* before, more or less.. (fluctuates due to the cam). at 3000 rpm, my total is 22*. that reading is relatively steady, but the engine has always had a slight "miss", thru all RPMs, kinda like an overlap-fire, if that is a good description....
my question is:
after removing the weight plate (to replace it with the new one from the Moroso kit), I see what looks-like "slugs" or "plugs", welded into the slot where the centrifugal mechanism moves to allow centrifugal advance.
in other words, I understand by looking why I can't get but the few additional degrees centrifugal, but why, or what,, would be anyone's reasoning, for fixing the centrifugal to only have "x" given degrees of centrifugal ?
I have an engine builder coming-by to take a look, so I'll be gone from here for a while,, but I'd appreciate any feedback if any of you have seen or done this, or understand why ....

'69 SS X66 Camaro
454, TH400 & GearVendor, 12 bolt
'82 Corvette.
stock
'81 Camaro Pro Bracket car.
406, TH350, 10 bolt, NHRA #3148
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post #2 of 6 (permalink) Old Jul 16th, 09, 03:56 PM
DjD
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Re: GM HEI centrifugal advance blocked ??

If all you do is run the quarter mile in WOT passes it might be beneficial to lock out or restrict the mechanical timing. There are a lot of cars driven on the street with track only parts or mods for the cool factor. The previous owner or who ever set the dist up may have been getting advice from track rats. About 18 - 20 degs mechanical would probably cover most street applications.

...Dennis

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post #3 of 6 (permalink) Old Jul 16th, 09, 07:13 PM Thread Starter
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Chris
 
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Re: GM HEI centrifugal advance blocked ??

evidently, you're right-on Dennis..
my bud down the street had a take-out HEI, so we swapped internal shafts to-include the advance mechanism, and now, at 12* initial / 25* total @ 2500rpm (that was with the "chrome" springs out of the Moroso kit), it starts great, didn't overheat idling, and throttle response is better than it has ever been in over 4 yrs.
I don't have a camera here at home, but I'm gonna take this modified shaft to work with me tomorrow and post some pictures..
just goes to say that when a build is inherited, and problems arise,, don't leave any stone unturned..

'69 SS X66 Camaro
454, TH400 & GearVendor, 12 bolt
'82 Corvette.
stock
'81 Camaro Pro Bracket car.
406, TH350, 10 bolt, NHRA #3148
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post #4 of 6 (permalink) Old Jul 16th, 09, 11:04 PM
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Re: GM HEI centrifugal advance blocked ??

If you want to put more advance in a GM hei you have to remove .3 to 1 mm from the tail of the weight
Detailed several times in older posts

My Spelling is not incorrect...it is creative

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post #5 of 6 (permalink) Old Jul 17th, 09, 06:05 AM Thread Starter
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Chris
 
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Re: GM HEI centrifugal advance blocked ??

...excepting for if it's discovered that the centrifugal advance slots have been welded 3/4~way shut......then no amount of grinding will help anything. (unless I grind the slugs out and re-machine the slots where this butchering has cobbled them up and allow the centrifugal to function properly. I think I'll just stick it on the wall of my collection of "lessons~learned").





now I fully understand why I could never gain any-more than 5 degrees of advance, but I sure don't understand why someone would do this to a street-car engine..

'69 SS X66 Camaro
454, TH400 & GearVendor, 12 bolt
'82 Corvette.
stock
'81 Camaro Pro Bracket car.
406, TH350, 10 bolt, NHRA #3148
82Vettrin is offline  
post #6 of 6 (permalink) Old Jul 17th, 09, 09:48 PM
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Re: GM HEI centrifugal advance blocked ??

figure out how much initial and total advance your motor wants, and keep filing those holes out until you can set the initial where the motor likes it and have it advance to the total amount it wants.

you don't plan sincerity.
you have to make it up on the spot.

wanna hear about 20 years ago when i was too smart to know any better?
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