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Jan 20, 2001 | 11:22 PM

mudbug

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Joined: Jan 2001

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Distributor

Jan 26, 2001 | 06:36 PM

jspegg

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Posts: 70

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Distributor

I have a 73 f100 with a 390 I just replaced my vacum advance on the distributor because I had a hesitation when I would go to take off andways figured out it was the vacum advance it was ruptured. after I put the new one on my truck now will cut out real bad and backfire If I unhook the vacum advance it runs fine I have checked everything else out and cannot find the problem I think it maybe the distributor itself what do you think.also I have a bad king pin on my passanger side need to replace it I have never done this I just had them replaced about a year ago this time I am going to do it my self is there a good book to guide me through this and will they be pretty easy to get out considering they havent been in there that long.

Jan 26, 2001 | 10:37 PM

dave186

Senior User

Joined: Jan 2000

Posts: 238

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Distributor

First thing you need to do is get a light and check your timing with the vacuum line off and capped. Do you have the vacuum line hooked to a timed or full vacuum port on your carb? a timed port should have no vacuum to it at idle.

Dave
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Jan 26, 2001 | 11:11 PM

karljay

Cargo Master

Joined: Jul 2000

Posts: 2,281

Likes: 18

From: Northern California

Distributor

This is strange, use a vac gauge to see when you are getting vac from the carb. Then check timming without vac hose. The vac off the carb is supposed to be timmed, that is it only kicks in for a second when you hit the throttle. Also the stock vac adv is adjustable.
But this sounds like the vac is comming on at the wrong time, or the timming is not set properly. Also some distributers have vac adv and retard. Don't forget the engine needs to be fully warmed up before setting the timming, and check intake manifold vac at idle, it should be 17~20.

Jan 26, 2001 | 11:51 PM

jspegg

Junior User

Joined: Dec 2000

Posts: 70

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Distributor

we checked the timming we set it by the mark and also set it by vacum just incase the mark was off we even reved the engine up and while it was cutting out played with the timming to see if we could do it that way but still nothing the shaft has a little play very little but not enough to change anything it got me stummped I might try a new distributor but only as a last resort I havent seen any place to adjust the vacum advance so I guess I cant but it sure is advancing at the wrong time or to much advance

Jan 27, 2001 | 01:26 AM

MSTRAWN

Senior User

Joined: Aug 1999

Posts: 166

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Distributor

If you pulled the distributor when changing the vacuum advance, you may have missed the correct tooth engagement for the distributor gear when reinstalling. Check the position of the rotor in relation to the No. 1 wire in the distributor cap with the No. 1 piston at TDC.

1977 F-100
300 I-6 / C-4
Offy intake w/holley390
Hedman headers w/duals
MSD6
Whiter whites/Brighter brights

Jan 27, 2001 | 10:31 AM

jspegg

Junior User

Joined: Dec 2000

Posts: 70

Likes: 0

Distributor

I dont think that if I missed a tooth that would affect it as long as I still got it in time also I just put my dad's dwell meter on it and with the vacum hooked up the dwell moves alot when I gas it and even with the vacum off it still moves but not a lot

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Jan 27, 2001 | 12:43 PM

Post Fiend

Joined: Feb 2000

Posts: 5,130

Likes: 8

From: Brea CA

Distributor

It sounds like you are getting way too much vacuum advance or it's coming in too early. Sometimes these replacement vacuum units are not set up for the proper application too. First check your vacuum source with a gauge, there should be none at idle. The dwell should not change much with it disconnected, maybe 1 degree or so. With the vacuum hooked up, the dwell does change by 3 or 4 degrees. This is normal, the pivot point for the movable breaker plate is offset from the distributor shaft. This causes it to swing in an arc instead of rotating around the shaft, a cheesy design. If it changes any more than that or is erratic, the plate is worn out. Your vacuum unit may be adjustable, try inserting a hex key into the nipple port. If it is adjustable, turn it CCW a couple turns as this slows down the advance. Recheck engine operation and repeat if it needs more. If you come to the end (around 10 turns) don't force it any further or else you will weaken or rupture the diaphragm.

Barry