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'72 Chevelle Fresh Restore Question


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gmbaal
New User

Jun 7, 2014, 4:23 AM

Post #1 of 7 (1034 views)
'72 Chevelle Fresh Restore Question Sign In

Hello,

So I've got a 72 Chevelle with a .307 that is still a pretty fresh restore and rebuild of engine. The engine has about 1200 miles on the rebuild. I had an issue pop up with her this weekend that has me a little puzzled.

I had just done my second 500 mile oil change after the engine rebuild and was taking her for a drive up the interstate. She had gotten down to 1/4th a tank of gas on the trip when the engine started idling up and down on me.

The problem is now most noticeable when you are accelerating, but the issue seems to be getting worse. At high fuel speeds or when you are heavy on the gas, things seem to smooth out.

Other factors, the last time she was timed was in the winter. I have recently changed Alternator, battery and batter cables. I was thinking bad gas, so I have put in some octane booster and some dry gas in her, but since the dry gas the problem seems to have worsened.

Any suggestions on what to check out would be awesome. I'm still learning how to troubleshoot these wonderful cars. I know my way around the engine and feel comfortable with most repairs already, but the troubleshooting is where I'm lacking.

Thanks,
Joe
https://plus.google.com/u/0/photos/+JosephCraig/albums/5843876305671379537


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Jun 7, 2014, 7:41 AM

Post #2 of 7 (1006 views)
Re: '72 Chevelle Fresh Restore Question Sign In

Have you checked for vacuum leaks? Choke all the way open when it is fully warmed up? If you look down into the carb while the engine is idling, do you see fuel dripping out of the booster? Checked for clogged air bleeds?





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gmbaal
New User

Jun 7, 2014, 8:38 AM

Post #3 of 7 (1000 views)
Re: '72 Chevelle Fresh Restore Question Sign In

I found a dirty air filter and dirty carb. I cleaned both of those and the problem is not as bad. She is back to idling in park and neutral, still idling slow and hesitation in the pedal. I drop her in gear and she will die on me if I don't flutter the gas.

I have felt around for vacuum leaks, and not found any as of yet. however I did spray a little carb cleaner on the vac lines and the engine idled up which makes me think there might be some vacuum issues.

Thanks,
Joe

(This post was edited by Hammer Time on Jun 7, 2014, 9:48 AM)


Discretesignals
Ultimate Carjunky / Moderator
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Jun 7, 2014, 8:59 AM

Post #4 of 7 (997 views)
Re: '72 Chevelle Fresh Restore Question Sign In

If you have any rotted vacuum hoses, you should go ahead and replace those. It is important that you repair all vacuum leaks because they will cause your carb to lose its vacuum signal at or near idle speeds causing the engine to run lean.

You could still have a carb problem. Did you take the carb apart to clean and overhaul it? There is also the concern of adjustments on the carb also.

Have you checked the operation of the vacuum advance on the distributor. The vacuum hose going to the vacuum advance servo on the distributor should have vacuum on it when you snap the throttle with the engine running.

You should also inspect the advance mechanism in the distributor to be sure the weights are free to move and that the plate rotates when you apply vacuum to the servo.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Jun 7, 2014, 9:15 AM)


gmbaal
New User

Jun 7, 2014, 9:44 AM

Post #5 of 7 (980 views)
Re: '72 Chevelle Fresh Restore Question Sign In

I just used carb cleaner and a toothbrush to clean it out. I didn't break the carb apart. Things have gotten better, now it just seems like it's idling slow.

I have adjusted the idling down over the past few months so this could have been going on for a little while and now it seems I may need to go the other way. I'll check out the vacuum lines as well.

Thanks for the help I'll keep things updated.
Joe

(This post was edited by Hammer Time on Jun 7, 2014, 9:49 AM)


Hammer Time
Ultimate Carjunky / Moderator
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Jun 7, 2014, 9:49 AM

Post #6 of 7 (977 views)
Re: '72 Chevelle Fresh Restore Question Sign In

OK, please take the link out of your signature. Once is enough.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Jun 7, 2014, 10:21 AM

Post #7 of 7 (974 views)
Re: '72 Chevelle Fresh Restore Question Sign In

The carb may need to come apart. There are tiny passages that have to been cleaned out, so a tooth brush won't cut it. Carbs are like musical instruments. If you have one part in a carb not working or adjusted correctly, the whole thing won't perform right.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.






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