I'm having a bit of trouble getting my idle right. I installed a Crane Cam (210/216 dur, 0.440/0.454 lift) in my 350 about a month ago and I am having a hard time getting a decent idle. The engine even bogs down to about 500 RPM during a WOT shift from first to second. I was thinking about the slack in the timing chain being on the wrong side. It's a new chain, but I was thinking that if the slack was on the right side (looking at the gears) that it would cause a slight shift in the cams alignment with the crankshaft. The crankshaft would turn a bit before the slack would take up and the cam started turning. Am I digging too deep here or what?

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1984 Z/28
GoodWrench 350, Edlebrock Performer intake, MSD 6AL Super HEI kit, Crane CompuCam 2040, Edelbrock headers, Catco cat, Flowmaster aftercat, K&N, Custom 700R4, B&M Megashifter, Eibach springs, KYB GR-2 struts/shocks, Jegster adj LCA's, Lakewood adj panhard bar, BFG Comp T/A's, 160* stat, AutoMeter Pro-Comp COOLANT GUAGE.

 

I'm assuming your engine is carbed??? TC slack with a brand new chain should not be an issue unless you paid <$20 for the set... Sounds like you have a low vacuum/carb signal/carb adjustment problem to work out...

IF you are EFI, you may need a new PROM, FP adjustment, initial timing adjsutment or a combo of all of the above.

 

Its the LG4 Qjet with AH rods and M hanger. One other thing I was pondering was to cam degreeing or not. I have read that degreeing the cam get the most potential from the cam, but I have also read that if you have to degree it, you probably don't have the right one. Since I talked directly with Crane to choose the right cam, I just installed it straight up. I just put the rods in yesterday. It seemed to help a bit. I'm still not sure about the computer either.

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1984 Z/28
GoodWrench 350, Edlebrock Performer intake, MSD 6AL Super HEI kit, Crane CompuCam 2040, Edelbrock headers, Catco cat, Flowmaster aftercat, K&N, Custom 700R4, B&M Megashifter, Eibach springs, KYB GR-2 struts/shocks, Jegster adj LCA's, Lakewood adj panhard bar, BFG Comp T/A's, 160* stat, AutoMeter Pro-Comp COOLANT GUAGE.

 

Z/28,

There is always a little slack in the chain. As soon as you install a new set and run it in for a few hundred miles, the chain will stretch and wear to the point where there is just enough room for oil clearaince without overtension. The little bit of slack will always be taken up by crank rotation as soon as the engine is running, and can account for maybe a fraction of a degree in cam timing.

If your cam was installed without benefit of a degree wheel, it is possible that the cam was ground off lobe center, the cam sprocket dowel was drilled incorrectly in either the cam or cam sprocket (or both) or the crank key was broached in the wrong position. A little tolerance is allowed in the manufacture of these components, and if all the tolerances are off a bit in the same direction, your cam timing could be off by a few degrees.

It is also very common for aftermarket camshafts to be ground with a few degrees advance. Therefore, chances are that if it is off at all, it is still slightly advanced beyond factory cam timing specs. This maight not be optimal for your engine, but should be close. The easy way to check is with a degree wheel and dial indicator on the rocker end of the push rod. If the timing is within the acceptable range, you can rest assured that the cam is not the problem. At least you'll know wheter you'll have to remove the timing set to retime the cam.

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Later,
Vader
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"No matter how hard you try you can't stop us now"
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