engine "surge" vacuum advance issue?

[Stegs]

I had a very helpful guy tell me that I might have a vac leak from my vac advance when I was talking about engine surge.

The car @50 mph kinda revs up and down, I thought it was the converter in the trans locking/unlocking, but then he suggested I take off the tube that comes from the distributer to the carb. He said plug the hole on the carb and report back

Well that's easy enough to do, but if I remove the tube, and plug the hole where it goes into the carb, can I drive the car without worry of any damage?


Im assuming I have a vac leak, which is what he is implying, but if I remove that tube, will the timing advance enough to where the car will be able to run safely without damage?

can I drive it down the road to see if it fixed the problem?

If it does fix the problem, do I just get a new rubber tube?

I just don't want to do any harm to the motor is all

[don duick]

go to the "performance corner" section, page 3, go down 20 topics you will find the same subject.

[Ghoste]

You won't harm it, a lot of people run without it anyway.  On a street car you should have a vacuum advance but it's purpose is to bring the engine to a more fuel efficient point when you are in a steady cruise.

[Cooter]

Some big cams require more initial advance, without recurring your dist. Though, this can cause what n you describe. Won't hurt anything without it.

[Stegs]

found it...exactly what I have....

I will remove that tube tonight, but what should I use to plug the hole in the carb? just a piece of tape? or doesn't it matter as long as its covered?

now if this fixes the problem....does that mean I have a vac leak? do I just get a new tube? or do I just run the car without it?

or is this the start or tracking down a bigger problem/issue?

[cudaken]

You can buy Vacuum Caps that will seal the carb, or just leave the line on the carb and stick a tight fitting screw or nail in it.

Cuda Ken

[don duick]

disconnect and reconnect tube to vac advance with engine running you will hear the difference. Listen for suction from the tube or put your finger over it, should be strong if not it is connected to wrong port on carb.

[Stegs]

disconnect and reconnect tube to vac advance with engine running you will hear the difference. Listen for suction from the tube or put your finger over it, should be strong if not it is connected to wrong port on carb.

ok guys, I took the line off, couldn't feel a strong suction when I took it off, when I gave the car a little gas then I could feel it

I removed the tube completely, covered it up where it went into the carb and it made no difference. I put my thumb over it where it goes into the carb, car made no noise differences at all....

im thinking now its more of a timing issue? or the carb is in need of rebuilding....

[firefighter3931]

I'm not clear on exactly what you did ? 

Was the vacuum blocked off and did you take it out for a drive....or did you just check to see if the vacuum ports were producing a signal ? 

One port on the carb will be full time (manifold) vacuum and the other will be timed (ported) vacuum. The vacuum advance is supposed to be connected to ported vacuum if it is being used.

You need to block it off and take the car out for a drive. It might need some timing adjustments and carb adjustments to dial in for best performance. It all starts with the distributor first...then carburator/fuel delivery. 

How much spark lead do you have at idle ? What is the total timing ? What RPM does it stop advancing at ?



Ron

[Stegs]

what I did was took the little rubber tube off the distributor to the carb.

I plugged the hole where it goes into the carb.

took it for a drive and had no difference

Ive determined that my timing is off or the carb has a vac leak somewhere, or its gummed up from sitting for about 20+ years


I adjusted the mixture screws, I went out about 3/4 turn each one and it seemed to help a little, but not enough where I feel comfortable driving longer distances

I may need to get the carb rebuilt or get a new one....but its going to my friends engine shop, he is going to check/adjust the timing if needed and go thru the carb and make sure its doing what it should. He will look it over and let me know what the deal is.....