L-82 Dist. Vac. Cans

**Duke W.** · May 17, 2005, 09:09 AM

Re: L-82 Dist. Vac. Cans

The first three digits are the last three digits of the GM long number, and the last two digits indicate the total advance in crankshaft degrees, so you have gone from 10 to 20, which is probably too much. I'm familiar with the "577 10" (1973577, D-1356, 0@4", 10@8") which was used in L-82s as I also use that number on my Cosworth Vega (which was not originally equipped with a vacuum can), but "626 10" doesn't ring a bell.

A proper initial timing can only be determined if the total centrifugal advance is known. What is it? It should be listed in the service manual and AMA specs along with the vacuum can specs. Keep in mind that your timing map is set up for emission control, so advance at idle and low revs is keep well below the ideal amount to create high EGT to keep the converter hot.

HEIs are easy to rebuild, similar to single point distributors - check shaft bushings, grease the upper bushing well, and install a new module and pickup coil, cap and rotor - about a hundred bucks in parts. Also replace the plastic bushings in the weight pivot bores - Borg Warner DG13 from Pep Boys

Duke

**John Liner** · May 17, 2005, 10:24 AM

Re: L-82 Dist. Vac. Cans

Thanks Duke, I was hopeing you would respond.
I thought the can on my Original dist. was the correct one but I can't be sure.
Maybe Joe will check it out for me. I have checked my books but can't find the vac can number for my original dist.
If it's not would you have a recomendation?
Thanks for the response.

**Duke W.** · May 17, 2005, 10:42 AM

Re: L-82 Dist. Vac. Cans

My '80 Corvette P & A catalog shows 1973626 for your engine, so the one installed is probably original and the 10 indicates it provides 10 degrees. The 1973577 used on '76 -'77 L82s is also ten degrees, and I gave the exact specs in my previous post.
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Do you have a service manual?

Do you have the AMA specs that are part of the free GM restoration package?

I can't offer much more without knowing the specs.

Duke

**Timothy B.** · May 17, 2005, 10:48 AM

Re: L-82 Dist. Vac. Cans

John,

My Chilton's manual lists distributor # 1103291 specs as centrifugal advance, 0 @ 1200 - 13 @ 1600 - 16 @ 2000, vacuum advance is 0 @ 4" - 10 @ 8", so the advance can may be correct. In the tune up section it shows inital timing as 12 BTC.

**John Liner** · May 17, 2005, 10:54 AM

Re: L-82 Dist. Vac. Cans

Duke, I do have the service Manual, not sure if I have the restoration package you refer to. Very much appreciate your input. Started on this last night and haven't really done my homework. I knew the engine wasn't running right with this dist. (sluggish) but it starts and drives ok. I will have more time to work out the kinks later this week. This engine was rebuilt about 3,000 miles ago with a little more cam and different pistons with a lot of head rework.
Would like to get it running at it's best.
I would like to follow up with you later for ideas on how to make the most of what I have. Thanks again!

**John Liner** · May 17, 2005, 11:08 AM

Re: L-82 Dist. Vac. Cans

Timothy/Duke,
I understand my vacume can is hooked to a thermo/ported valve which controls the vacume untill the engine warms up, right? So the vacume advance doesn't come in untill the engine warms up. If you add up the specs that Timothy posted wouldn't you have a total of 38 degrees timing? This being based on the engine being hot and the vacume ported valve opened up. 12 degrees inital,16 Centrifugal and 10 by vacume can? Is this correct? Is this too much. Just asking.
Appreciate all information or sugestions.

**Duke W.** · May 17, 2005, 11:11 AM

Re: L-82 Dist. Vac. Cans

The distriubtor centrifugal and vacuum advance specs are in the service manual. The initial timing should also be specified and it's also stated on the emission/tuneup decal in the engine compartments.

"A little more cam" was probably a mistake. Different pistons? What does that mean? What is the claimed compression ratio? The L-82 cam is already more than sufficient, and most aftermarket cams have more overlap, which will decrease low, end torque, which is ill advised.

Call GM Customer Service 800-222-1020 and ask for the '79 Corvette Restoration Package. They will want your VIN.

Duke

**Duke W.** · May 17, 2005, 11:21 AM

Re: L-82 Dist. Vac. Cans

The details of the timing controls are in your service manual, and it probably has TCS with low temperature blockout. I'm not intimately familiar with the specfic configuration. Read the manual and tell us the setup.

There are three different "total timing" specs - idle, cruise, and WOT.

WOT total timing is the sum of initial and full centrifugal, which would only be 28 according to the Chilton specs. Ideal is 38, but this is an emission controlled engine and the timing map was set up for emissions, not performance.
Vacuum advance is NOT included in the total WOT timing number because there is essentially no manifold vacuum at WOT - at least no where near what is required to start pulling the vacuum can plunger. Vacuum advance is included in the total cruise timing and total idle timing on pre-emission engines, but usually not on emission controlled engines.

What are the ignition map specs in the Chassis Service Manual?

Duke

**John L.** · May 17, 2005, 06:05 PM

Re: L-82 Dist. Vac. Cans

Will do Duke. Thanks for all the input. I'll follow up later after I do my homework.

**Joe L.** · May 17, 2005, 10:40 PM

Re: L-82 Dist. Vac. Cans

John-----

GM #1973626 is the correct vacuum control for your distributor. Also, you're in luck as it's still available from GM for about 20 bucks, list.

**John Liner** · May 18, 2005, 07:22 AM

Re: L-82 Dist. Vac. Cans

Thanks Joe. Thats what I wanted to hear. Appreciate your help.

**Duke W.** · May 18, 2005, 06:15 PM

Re: L-82 Dist. Vac. Cans

I'd still like to see the specs on this can from your CSM or AMA specs.

Duke

**Joe L.** · May 18, 2005, 08:02 PM

Re: L-82 Dist. Vac. Cans

Duke-----

The GM-published specs for the '626' vacuum control are as follows (in crank degrees):

0 degrees @ 4" of vacuum

10 degrees @ 8" vacuum

mechanical advance specs for the 1103291 distributor:

0 degrees @ 1200 rpm

13 degrees @ 1600 rpm

16 degrees @ 2000 rpm

initial timing for 1979 L-82 (both 4 speed and auto)

12 degrees BTDC

**John Liner** · May 19, 2005, 08:01 AM

Re: L-82 Dist. Vac. Cans

Thanks Joe.
Duke sorry for my delay, I have been on the road, and unable to find out what you ask. Guys, I realy do appreciate all your responses.
Thanks all for the responses.

L-82 Dist. Vac. Cans

L-82 Dist. Vac. Cans

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