zakbradshaw

I had a shop set the timing on my distributor after an intake swap. The new hold down came loose and the distributor went out of timing. I converted to an HEI distributor and the shop said they marked it in case it ever needed to be reset. I got a different clamp, but how do I reset the timing?

Thank you!

MelWff

Do you own a timing light or can borrow one?
Not too clear on which clamp they marked and can you see the mark they are referring to?

zakbradshaw

I do have a timing light but have not used it really other than just messing around with it. I am pretty good with mechanical stuff, but lost when it comes to distributors. I don't know where/what he marked. He just said he marked the distributor in case I ever needed to reset the timing. What do I need to look for? How difficult should it be for me to reset timing?

Thank you!

SH-60B

Hook up your timing light, rotate the crank so #1 is before TDC by 8* as read on the balancer (or whatever you use for initial timing), with key on rotate the dizzy til the light flashes, lock down dizzy.

toobroketoretire

The shop most likely put a reference mark on the inner fender where the HEI cap was pointing. Ask the shop what they did to "mark it" so it can be put back in the same every time it gets removed. I have a thin white line painted on the top of my cap and that line points at a black line I put on the inner edge of my right fender. So any time I take my HEI out I can put it back in and rotate it until the white line points at the black line and be within 1 degree plus or minus.

CanadaGrant

There are a number of good videos that will show you how to do it rather than a written explanation here. Google "set initial timing chevy v8 youtube". If you have a light it's an easy job once you can actually see how it's done.

zakbradshaw

What degree of timing should I set it at with my timing light?

MelWff

Your profile states you have a 1981 Corvette. So how did you "convert to HEI" since it already came with one from the factory? Can you please provide complete information so that others can help you?

zakbradshaw

The 81 has the computer controlled carb and distributor, not HEI. I replaced intake/carb/distributor/etc to convert it to a traditional non-computer controlled setup.

Peterbuilt

These articles might help you understand a little more about timing.

http://www.lbfun.com/warehouse/tech_...%20ADVANCE.pdf

https://www.corvetteforum.com/forums...long-post.html


Once you learn how to do it you won't have to pay a shop anymore.

MelWff

Do you know exactly which distributor was used and whether the advance curve was modified? The stock timing on an 81 with computer control was 6 degrees BTDC which is very tame.
Is your timing light a dial back model?
Is there a reason why you are not asking the shop exactly how they marked the position of the distributor?

zakbradshaw

This is the distributor I used... http://www.summitracing.com/parts/su...make/chevrolet

The distributor was not modified. My timing light is one of the digital ones where you can set the desired timing. I have not contacted the shop because it was a few months ago and don't remember which of their employees worked on it.

MelWff

If the instructions are accurate, step 10, you have 20 to 22 degrees of crankshaft mechanical advance at 3,000 RPM, I assume the instruction numbers are distributor degrees which are 1/2 crankshaft. So with the vacuum advance disconnected set the initial timing to 16 to 14 BTDC. Then reconnect the vacuum advance.
http://static.summitracing.com/globa...i%206-2-08.pdf

zakbradshaw

16-14 initial BTDC, okay when I get a chance I will try to get this set. And that's at idle with the vac hose disconnected and plugged correct? How much total timing will that make?

MelWff

Yes disconnected and plugged. We are aiming for a total of 36 degrees mechanical so the 20 to 22 plus the 16 to 14 initial will give the desired 36. This is assuming you are running premium gasoline, 93 octane.

zakbradshaw

Yes, I only ever run 93 in my vehicles. Thank you for your help. I will repost on this thread when I get a chance to set the timing.

toobroketoretire

Thank you for pointing that out. The 36 degrees is the desired amount of timing IF a high octane fuel is used which means its too much for 87 octane use. And the 36 degrees was the desired amount back in the days when 100+ octane was readily available. With today's 91 to 93 octane I feel 36 degrees is pushing it and 33 to 34 would be a much better choice to avoid pinging under a heavy load.

I'm running 91 octane in my 10 to 1 compression ratio 454" and I found the most advance I can run under a heavy load is 31-32 degrees and even then I get a tiny bit of pinging in 100 degree weather.