I already posted this in the Performance forum, but I'm putting it here too.

Here's the basics: 1969 Chevelle..350/300hp...everything stock except for HEI distributor. Here's the problem: Driving along the highway this morning...about 10 miles...got off the ramp and car was running real rough, would hardly idle. Got it home checked timing first to see if distributor maybe moved..nope. started checking carb and was only getting a reading of about 4-6 on vacuum gauge. I had another carb I was going to put on anyway, so I swapped them out. Now it has a Holley 650 DP. Started up alright, was getting about 18-22 on the vacuum gauge. After it warmed up...same thing as before...hardly idles...vacuum reading down to about 4-6. HELP ME...what could have possibly happened??

Sounds like a vacuum leak to me, try squirting WD-40 around intake and bottom of carb when it's doing this, and see if you cant find the leak.

Rocky Hill

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A Man And His Chevelle!
It's A Beautiful Thing.

MACC Member #220
TC Member #1530

My66SS (http://www.geocities.com/rocks66ss)

I would check the vacuum leak first too...

If that ain't it: I had similar issues when my fuel pump went for a crap (stock mechanical type). Check your fuel pressure. My symptoms were rough/poor acceleration....good luck.

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Ron Cook TC Gold #1276 ___ ACES #5136
1969 300 Deluxe HTSS396 (http://www.chevelles.com/showroom/bow_tied4.jpg) The L35-325HP 396cid (http://www.chevelles.com/showroom/bow_tied3.jpg) 69 Memory Lane (http://www.chevelles.com/showroom/bow_tied.jpg) 1971 Malibu 2DR HT (http://www.chevelles.com/showroom/bow_tied_71Malibu.jpg)
CanAm Chevelle Club (http://www.canamchevelles.com)

Has it been hot there? Sounds like a possible vapor lock.

Thanks for the replies. It seems to be running alright now. I did put some fresh gas in...maybe I had some bad gas. It has been very hot here so maybe it could have been vapor lock. I'm not really sure what it was but I hope it doesn't happen again!!

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1969 Chevelle Concours..350/300HP///4-door..yes...4-DOOR, but it thinks it's a 2-door!!

http://www.chevelles.com/showroom/May27_31convert.jpg

I CAN'T BELIEVE IT !!! It happened again. It has been running fine for a few days now...then all of a sudden, last night, it started to run lousy again..barely idleing. I decide to forget about screwing around with the carb any more and went out and bought a remanufactured Q-jet to replace it. I just installed it and it started up fine...went to high idle...nice and smooth...reading about 15 on the vacuum gauge...then once it warmed up the vacuum gauge went to about 2-3 and it died. Why am I loosng vacuum when it warms up? And to make things worse I have to take the carb back anyway...the piston for the fuel pump keeps getting stuck down. I don't know what to do next!!

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1969 Chevelle Concours..350/300HP///4-door..yes...4-DOOR, but it thinks it's a 2-door!!

http://www.chevelles.com/showroom/CONCOURS2.jpg