Auto Racing: timing, mallory distributor, stock dirt

Question
QUESTION: I run a factory stock dirt oval track car with a 355 chevy engine. 460 lift cm with a 2 barrel carb., everything else is stock. The distributor has no vacuum advance and I have a lock plate on it. When I try to time the engine the timing marks will jump between a 20 degree area on the balancer. I will get 3 readings, one about 10 degrees before one at zero and one about 10 after. not necessarily in that order. The engine has a cam button in it also.It runs good, doesn't overheat, and I'm in the top 5. Can you help? Thank you. George.

ANSWER: Hi George !

Somewhere there is something WAY too loose.  My first suspicion would be in the distributor drive, then the timing chain.

You can sometimes shim the distributor gear to take up some slack. Leave enough gear lash though, about .005"to .008" is good. Check the distributor gear for wear !  It's easy enough to replace it and they're cheap.

The other common problem is the timing chain.  If there is excess slack in the chain, change the whole timing set, both sprockets, and chain come together. Get racing stuff from Summit Racing (www.summitracing.com)

You can also install a cam button because excess end play in the cam can create problems with ignition timing.  The motor will run better too because your cam timing will be more accurate which makes  a big difference.  You may be able to get a replacement timing cover with a cam button already installed. Clearance between the button the the front of the cam should be about .010" or a hair less.

Anything you can do to get beyond the stock HEI stuff will be a help.  If you can run a Mallory distributor it's better- - -ANYthing is better than the stock GM stuff.

Here's a suggestion for you. Do one thing at a time so you'll have a better feel in the future for what to look for. Take notes, and pictures of what you find, and keep accurate records.

That should do it.  If you need other advice feel free to write again, and thanks for a challenging question!

Sincerely,

Dan Liddy
Sarasota, Florida    



---------- FOLLOW-UP ----------

QUESTION: Is it possible that hooking the power wire to the on switch would make a difference? I was told once to disconnect the distributor. That didn't change anything. Once I hooked to the solenoid and it was completely off. I'm going to try and extend my wires to reach the battery and see what happens. Again thank you for the info.

Answer
Hi George:

If by the power wire, you mean the wire to the distributor, then no, you're wasting your time. So long as your ignition switch is a quality switch and in good condition there should be no difference. I hope you're not using the junk that came on the car though, they really aren't much, and are made in Borneo or some other third world place. Plus you should NOT have the steering column lock on a race car.

You can find out by using your volt/ohm meter set on ohms and reading across the switch, one meter wire to each side of the switch while it's in the 'on' position. There should be no reading at all or no more than a small decimal .1  or .2 ohms.

Your ignition wire should run from the emergency battery cut-off switch, to the ignition switch, and then to the distributor.  I use 14 guage for this just to make sure there's no voltage drop, but it would be minimal in any case.

That's all I know about that

Dan