350 HEI Owners Only

[DJSH]

So, I had the dealer (yes the dealer of all people) take a look at my truck because I am short on time these days.....anyway, they said the carb needed to be replaced so I bought a new one and had them do that and new plugs. Long story short, I was talking to the mechanic as my truck idled and it would rev up and "rough" every so often. I asked why this would be happening and he said its a carb. Well, I don't buy it. Why would the engine rev up and down at idle and run rough while it is revving up? Everything is new on the conversion.

Thanks for any advice. I am thinking about switching out the HEI and disti for another to see if that is my problem.

Dave.

 

[Gumby]

I don't think it would be your HEI distributor unless your timing is fluctuating. Check the timing advance with a timing light. If it is relatively stable at idle and advances normally during acceleration, I doubt it is the distributor itself. A weak coil, bad cap, wires or plugs can cause the rough acceleration.
The hunting idle could be as simple as a vacuum leak. I hate it when mechanics tell people they need a new carb. Unless the body is cracked or the throttle plate bushings are worn, it seems like a way to get the customer to buy a big expensive part rather than fix whats wrong.

Did your new carb fix the problem?

 

[DJSH]

The new carb did not fix the problem, but did make a difference in more power throughout the powerband. "The hunting idle could be as simple as a vacuum leak." Remind me how to check for a vacuum leak on the 350? Also, I was thinking there was too much vacuum pulling on the disti and causing it to run rough, so I should be able to plug the vacuum adv. on disti and have it smooth out, right?
"A weak coil, bad cap, wires or plugs can cause the rough acceleration." I think a new cap and coil are next on my list. The plugs are brand new NGK. Wires less the 3000 miles. This has been happening virtually since new.

Thanks for all the help.

 

[warpdriv]

Correct me if I'm wrong, but are you running a "ported" vacumme source to your dist? You can't just run straight vacumme. Your carb should have 1 or 2 sources.

What carb are you running?

To check for vacumme leaks, pull and plug all of your vacumme sources.

Maybe it is a leak in your dist diaphram? Just an idea...

I'm running a Proflame HEI dist. I have been happy with it.

HTH,

 

[hammerhead]

What brand of carb?

Jeff is right - you must run "ported" vacuum to dist.

Set your timing with vacuum hose removed from dist and plugged.

Use a degreeable timing light to verify proper advance curve.