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Discussion Starter · #1 ·
I am having difficulties with the velle!!! It is idling very rough when you give it gas it backfires out the exhaust. I have tried 2 different distribs, adusted float level checked and set tiing multiple times just can figure it out. It is a 70 chevelle, 327 with a performer intake and 750 vs holley. It currently has an hei. ANy ideas where to start? Also it occasionally pops out the carb. Ive checked the power valve, it is ok. Can any one give me an idea what to check next?????????????

also can you help me find my voltmeter, It seems to have walked out of the garage on its own. If you see a worn grey fluke meter walking sown the street, please send it home.. I miss it:confused:
 

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Could be a lot of things but I'd start by checking ignition wire routing. You said you've checked timing but you didn't say what it was (total and initial). Cam timing could also cause your symptoms (as would improperly adjusted valves). Other possibilities that come to mind are a bad valve, bent pushrod, or slipped timing chain. Were any changes made before the problem started?
 

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Discussion Starter · #6 ·
Intial timing is about 15* kind of hard to tell because of the rough idle. total is impossible to find due to the backfiring, its about 26* or so when the backfiring starts/about 2800rpm. no changes had been made prior to this. Ill change the plugs tomorrow see if it makes a difference. if not Ill check the valves see if one is stuck or a collapsed lifter or something else odd..

keep the ideas coming
 

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Like Jerry mentioned, a bent pushrod, did you get on it hard lately or rev it real high, roll the push rods on a piece of glass and see if there true.

Rob
 

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Discussion Starter · #8 ·
Like Jerry mentioned, a bent pushrod, did you get on it hard lately or rev it real high, roll the push rods on a piece of glass and see if there true.

Rob
havent really driven it in months, but my son was out "showing" it to his friends in the driveway the other day, There were several High rpm revs before I got out there to tell him to shut it down..
 

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I just went through this with my new 66 and its junkyard dog 350, Edelbrock performer and Edelbrock carb.

Although it only has two vacuum lines to begin with, I changed both, the dist line, and the trans modulator line. Put a new vac cap on the other tap on the carb, adjusted the carb, and its much better.

I think it has a cam that is maxing the valvesprings or just is too big for a stock old motor, as it still has a shakey 12 in of vacuum at idle.

But, after fixing the two wire twist wiring to the HEI. it seems much better.
 

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Check your rockers. I just bought a complete 454 that owner complained of backfiring after a quick high speed run. Dyno sheet showed 347 HP at the rear wheels. Offered a $1000 and asked to pull a valve cover. Rocker arm was lying in the head, had a broken locknut. And it was a four bolt to boot.
 

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Was the car doing this before you made the carb and distributor changes? If not, then I would go back and make sure the distributor is on top dead center and the plug wires are correct. Sounds like timing is incorrect.
 

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Also make sure your balancer is not damaged between the inner and outer sides. Can cause you to constantly time the engine wrong because the outer ring has seperated from the inside hub.
 

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Discussion Starter · #19 ·
Was the car doing this before you made the carb and distributor changes? If not, then I would go back and make sure the distributor is on top dead center and the plug wires are correct. Sounds like timing is incorrect.

the changes were made because of the problem, It had a gm point dist. It sound like the points were shot again, I had a new hei I had bought for the 454 thats going in this summer so I installed it. Ive checked the firing order multiple times but will again just to make sure I didn't screw it up. I think it something simple I'm just overlooking due to aggrevation..

thanks again
 

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I'm having the same problem with my 'velle. I fired up the 'velle maybe once in 3 or 4 months. Give it some revs and let it idle for 10 - 15 minutes. Last time, all of it suden it started idling very rough en backfires from the carb. I think that I have blown the intake gasket from the manifold. Maybe you have the same problem? (I didn't make any adjustments the last 3 years)
 
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