punkisntdead

I put a Holley 670 Street Avenger on a pontiac 350 and its got a consistant pop back through the carb. its supposed to be preset out of the box,what could be causing this? the timing is set also.

Monza355

iTrader: (3)

Is this a brand new carb? Look at the power valve, they can cause trouble but you would think a new carb would be ok. Also check for dirt in the system. What is the timing set at?

Bill

punkisntdead

the carb is new. the fuel system is also new. timing is set at 12 degees before.

CTSV05

You are not clear on when the "pop" occurs.

Is it at initial throttle tip-in?

During a steady cruise state?

This will determine the condition theren the fix.

EPP

iTrader: (22)

Did you install the carb on a quadrajet intake manifold without using the plate, which seals around the back two barrels? You may have a vacuum leak. Bob

punkisntdead

well we found what was causing the popping...the roller rockers keep coming loose after we set them. Setting the valves should be a simple process I know. we made sure #1 piston was TDC on compression stroke then set the valves with half a turn (we've also tried a full turn) after the valve lash was right. we followed the firing order and turned the crank 90 degrees after we set each valve. still, after the car runs and warms up good, the nuts back off and the rockers start clicking. the studs and roller rockers are brand new? what's going on? sorry if i wasn't very clear about the carb earlier, it was popping while the car was idling. the carb is on an edelbrock performance pontiac intake. no plates underneath, just the gasket.

EPP

iTrader: (22)

It sounds like you need to use the poly lock nuts, which have a set screw in the middle of them.

The Edelbrock Performer intake is set up for the Quadrajet style (spread bore) of intake, meaning you need to use the plate under it. Bob

punkisntdead

I'll look into a plate to go under the carb...the rocker nuts do have a locking screw on top and we crank them down pretty tight...still no luck

I've rebuilt entire engines so I'm not completely ignorant on how to put stuff together. still, these things are kicking my ***.

Muffracing

Try different poly locks.