Thread: Cam installation gone bad....

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Help, I'm frustrated.

Running a '72 350 SBC with Edelbrock RPM Performer Heads and Intake. Holly 670 Avenger carb.

I had issues with cam lobe wear and lifter wear. I purchased a new cam and lifters (Lunati 00013). This is the cam that was removed.

Everything is installed and timing is set at 8 BTDC. Engine starts very hard, almost like its running on a couple cylinders. Once started it will run at higher RPM with good response. It will not idle below 1000 RPM. It takes constant pumping of the accelerator to keep it running.

I have verified no flooding issues on both carb bowls.
I have replaced all plugs.
I have checked compression on all cylinders with all plugs removed and I am getting 225 - 235 psi.
Verified spark on all cylinders.
I only have 1 vacuum line and it is installed.
All wires are installed correctly as they were never removed from the distributor cap or the wire guides.


Remember, The car ran before the new cam installation.

I'm open to any suggestions. Also, wondering if the cam could be one tooth off on the timing chain and if the engine would still run with these symptoms?

Thanks in advance.

By the way, I also set the valve backlash to .028 (intake) and .030 (exhaust) per the mfg. specs. I also reset them after break-in.

Sounds like maybe the idle cicuits in the carb are clogged, or maybe just one side. I had the same problem a few weeks ago after I did a head swap on my car. Ran fine before the swap, but ran like crap the first time I fired it after I did the work. was very hard to start and wouldn't run below 1000 rpm. I guess moving the carb around disturbed the stuff that had built up inside over time. I pulled the top off the carb and it was full of sediment. Cleaned it out and it runs perfect.

Did you check for a vacuum leak????

I will tear into the carb today to clean it up. I will also check vacuum, but I should add that the motor takes an unusual amount of throttle to start it and keep it running. I have to floor it to get it to start. If I adjust the idle screw in nearly completely, it will idle around 2000 RPM when warmed up. As soon as it the Rs drop below this, instant stall.

Thanks for both of your help. I'll let you know what I find this morning.

Did the car run ok before the cam was pulled? You mention you had issues with cam lobe and lifter wear, how bad was that wear? I know you say it "ran" before putting in this one, but did it run well? If it ran ok before you did this work I can't see the carb getting plugged up unless you had it torn down for a very long time.

I'm thinking either you have a major vacuum leak or you didn't get the timing chain on right. Also, this will be a dumb question, but it sounds like you have a solid cam...........are the lifters also solid for sure? Reason I ask is years ago I put in a Duntov 30-30 solid lifter cam and they screwed up and gave me hydraulic lifters. Ran like you are describing.

Don

x3 on the vac leak... Mine behaved the same after blowing out a vac cap with a backfire before I had the time set right... Didn't figure it out till I pulled the carb and found the missing cap

I had a similar problem with a 283 i built for a restoration, the culprit...intake leak. Check your intake gaskets.

Thanks for all the help. After looking at the carb, I decided to check out the timing chain installation. Timing marks were off. Re-timed the sprockets correctly, reasembled and she never ran better.

Thanks again!

Glad you got it fixed.....

Originally Posted by DennyW

((I have checked compression on all cylinders with all plugs removed and I am getting 225 - 235 psi.))

That was the key factor (give away), in the timing gears being off...

Thanks for adding that Denny, I didn't put it together.