Recently had to do some distibuter work. I didn't have timing light, so I took car down to a buddy of mine's station to time it. I had marked the location of the dist. before I took it out. When he timed the car to specs. didn't want to run right. The dist was about 1-3/4 of an inch away from the mark that I made. I put it back to the original mark and it does run better now. So do you go by the specs or not I guess is the Question. Car is a 79 L82 4SPD. Thanks

 

As long as the rotor points at the #1 plug wire when the #1 cylinder is at TDC on compression stroke,
and as long as the distributor body is clocked in such a way to give you enough room to move for
timing adjustments and advance can clearance, you are good to go.

 

if you go by the specs you will leave some performance on the table.
I'm assuming your '79 L82 has the same factory timing specs as my '78 L82. That called for it to be set with an initial timing setting of 12º. Most HEI distributors only had 18º or 20º mechanical advance built in and without modifying the unit or changing the advance stop pin bushing it's all you are going to get.
The mechanical advance plus the 120 initial timing setting will give you 30º-32º total timing (with the vac adv can disconnected and the hose plugged). This is pretty low and you can easily get a "feel of the pants" difference by increasing the timing to 36º total timing.
Also, the mechanical advance from the factory doesn't come all in until pretty high up the rpm range so you would be better off going to your local auto parts store and getting an HEI distributor recurve kit. This will include a few sets of springs and usually a few replacement advance pin stop bushings.
If you swap out the existing stop pin bushing for one with a smaller diameter you can get a few more degrees of mechanical advance. Than swap out the stock springs for the ones in the kit, you may need to experiment and play around to find the proper combination of springs to use but your goal would be to get the total timing to come all in by somewhere between 2800-3000rpm.

BTW, most local mechanics you find don't understand older cars, carbs, and distributors like the HEI. If they can't plug their diagnosis machine up to the car they are lost and confused. I'd strongly recommend going to Sears, picking up a nice dial-back timing light at only approx $49.99-$69.99 so you can set the timing yourself. Trust me when I tell you that once you learn how to do it the CORRECT way yourself you can EASILY set your timing up better than probably any local mechanic around you, and it won't cost you $200-$300 you would have to pay that mechanic to do it for you.
While at Sears, spend another $19.99 - $29.00 and get a decent vacuum gauge so you can also set the optimum idle fuel mixture.

If you need help using the timing light and/or vacuum gauge many of us on here can help explain how to use it and what to do to set your timing up

 

back when I was starting out hod rodding,, my dad who was a mechanic taught me to use a vacuum gauge to set the timing and air fuel mixtures. He would fiddle around with the timing and air fuel mixtures until we got the highest vacuum at idle. He never used a timing light. It sure seemed to work for us and my "hot rod" small block's as he called them.
With the newer carbs that don't have air/fuel adjustment except for idle, I don't see it wouldn't work the same. I haven't had to do this on my own L48 yet as it's running fine. He told me once that timing lights work fine (factory specs) when everythings new,, but as parts wear, things change.

 

Ok, I'll be the first to ask. Exactly what is the correct way to use the dial back timing lite?

Thanks.

 

very easy.......
let's say you want to set initial timing to 12º. Set the dial on the timing light to 12º and point the light at the balancer. You will see the timing marks show up and simply turn the distributor until the timing mark on the balancer is aligned with the "0" mark on the index plate just above it.

Say you want to set the timing at 36º total timing rather than set initial timing. Set the dial on the timing light to 36º, rev the motor up until the timing mark on the balancer stops moving so you know the advance is all in, than again just rotate the distributor until the timing marks is aligned to the "0" mark on the index plate.

You can also see where your current timing settings are easily wut ha dial back light. Lets say you want to check initial timing, just point the light at the balancer and turn the dial on the light until the marks on the balancer align with the '0"mark on the index plate than read where the dial is on the light and that tells you what your timing setting is. do the same with the motor rev's up to where the mark stops moving, turn the dial on the light until it's aligned with the index plate again and read the dial on the light to see where your total timing is.

it's MUCH easier and faster than using a regular non-dialback light where you first need to mark all the degrees on the balancer than read them while using the light

 

Great explaination! Thank you very much.

Dave

 

Thanks for all the input. I didn't mention that it was a new dist. that I put in. The Vacum Advance was wore out on the old one, so for $100 bucks I didn't think I could go wrong with this rebuilt one.