1966 L36 Vacuum advance Mechanism

[Stuart F.]

Re: 1966 L36 Vacuum advance Mechanism

When I first saw the weights in your post (without enlargement), I thought they were some sort of bugs like dragon flies. I have never seen anything like them. Are they originally like that or did someone get carried away with a bench grinder?? (look for grind marks)

Stu Fox

[Ronald L.]

Re: 1966 L36 Vacuum advance Mechanism

Hi Stu, they were in the car as bought, been there a very long time, like over 35 years, and had a little oxidation to prove it if you look close.

About 15 - 20 years ago I went through a big move and a lot of my good stuff was given away so I no longer had any original springs or weights in the tool box to compare to.

Early in this thread and a prior, you note my concern that I was not getting full advance - and this seemed to be it.

Bu you know, in that tool box I do have an old aftermarket TI unit from my 70, or at least parts if it

[Joe L.]

Re: 1966 L36 Vacuum advance Mechanism

The weights in the photo aren't GM weights

John------


Surprisingly, these are GM weights of GM #1965843. They were not used for too many applications, but one of the applications for which they were used was 1966 L-36. 1968 L-88 was another.

[John H.]

Re: 1966 L36 Vacuum advance Mechanism

John------


Surprisingly, these are GM weights of GM #1965843. They were not used for too many applications, but one of the applications for which they were used was 1966 L-36. 1968 L-88 was another.

Joe -

Thanks - I learn something new every day, it seems; I've never seen a set of weights with "tails" like that in the 50+ years I've been fiddling with these cars, but I've never worked on or owned a '66 L-36 or '68 L-88 either.

[Duke W.]

Re: 1966 L36 Vacuum advance Mechanism

If you still have the OE weights, use them and install the lightest springs.

Disconnect/plug the VAC signal hose and tie up the centrifugal and set the initial at 8-10 degrees at the lowest revs possible.

Then untie the centrifugal an check the total centrifugal with the VAC disconnected and plugged. Rev it until the advance stops, which may be up to 5000. You should see 38-40.

Then drop idle revs to minimum to see where the centrifgual starts.
Test drive it. If it doesn't detonate, you're good to go.

Big blocks like about 40 degrees total WOT advance, and if it doesn't detonate...

Also, getting in the centrifugal in as soon as possible improves low end torque.

With a B20/26 VAC attached it should idle at 600 at about 14" with the OE cam and total idle timing should be at least 24-26.

DOCUMENT YOUR RESULTS!!!

Duke

[Joe L.]

Re: 1966 L36 Vacuum advance Mechanism

Joe -

Thanks - I learn something new every day, it seems; I've never seen a set of weights with "tails" like that in the 50+ years I've been fiddling with these cars, but I've never worked on or owned a '66 L-36 or '68 L-88 either.

John-----


I have seen used examples of these weights sell for BIG $$$$ on eBay. My recollection is that they were shown as applicable to 1970 LS-6 Chevelle which, of course, would always drive the price to the "stratosphere" for hardcore restorations (even though you could use the much more common weights and have the distributor curved to exact 1970 LS-6 specs). The problem is I don't show these weights as ever having ben used for 1970 LS-6. But, I suppose the guy that paid big money for them knows more about it than I.

While these weights were not real common, they were used enough that I would not think that used examples of them would be rare. They were used for both mundane as well as SHP applications.

[Ronald L.]

Re: 1966 L36 Vacuum advance Mechanism

Yikes, I did get any of the added posts (via the email notification) until Joe's latest.

Duke - the results I had with the ACCEL kit are above. Important point is I used the middle spring that had lots of advance at idle.

Next - on those weights. They go back in - what would we do without Joe's archive of original parts? I have to see the whole collection - really! Thank you so much.

The issue "I thought I had" is that I was not getting but 24 degrees mechanical with the old springs and weights.

So...Duke, with your latest script from the Doctor of timing, we will do Friday if the weather holds. I had 10, turned it back to 8 and was unsure of such a low idle speed, 600-650 so I will go back to where I was doing it as the Doctor prescribes above.

With the old weights - we will play with the springs and document results. That is the old way we know what is happening.

On the vac can, the L36 uses the 355 15 can and that new can pulls real good. If you look at my numbers above for vac - At 800rpm it was 15 and by 2000rpm it was essentially 20"Hg (we do have to go back to the 650RPM idle and verify vac I believe it was 12-13"Hg).

All the in & out of weights & springs - what grease for these - dieelectric OK?

[Wayne M.]

Re: 1966 L36 Vacuum advance Mechanism

....All the in & out of weights & springs - what grease for these - dieelectric OK?

Ron -- don't know about the weight plate contact (nylon or metal slide buttons ?) and pivot pins, but the grease in the tub is supposedly for distributor shafts, as well as starter uses. Ignore the tube, which is for the bump cam on points systems.

[Duke W.]

Re: 1966 L36 Vacuum advance Mechanism

Don't put grease on the autocam. Just spray/wipe down the parts with WD-40 so they don't rust.

Grease should only be used in the upper bushing grease well, tach drive cross gear, and a tiny amount on the point rubbing block. The grease Wayne photoed is good stuff for this application, but is no longer available. The alternative is a general purpose synthetic base NGLI #2.

Chances are your distributor upper grease well is dry. Most are because many of these distributors have never been disassembled for cleaning and overhaul.

Duke

[Ronald L.]

Re: 1966 L36 Vacuum advance Mechanism

Duke - chances are you are real right if you consider we were dealing with original components after 44 years here.

OK - round 3?

Note: from the above settings, ONLY changes are what I write below:

Original weights back in, gold (pic above) springs in, banded.
550rpm>14"Hg>9* at crank

Unbanded
450rpm>10"hg
@2000rpm 25*@CRANK
@3000RPM 25*@CRANK
To me, this was like where I was at the beginning of all this - not enough advance.

Put the silver springs in - middle pull force of the three in the set, banded.
450rpm
2* at crank
Adjusted distributor to 8-10* at crank
550rpm

Unbanded
@1000rpm 24*
@2000rpm 28*
@3000rpm 32 then 36*
@4000rpm 38*

It seemed that the advance was sticking, and a higher rev then down and back up again pulled the timing higher to 36*@3000 on subsequent revs.

That was enough,

vac can plugged in rpm to 900 - we went on the sub street.
Above 3000rpm it started pulling like never before through 4500. Seemed like a lot more power than before.

There isn't a highway that isn't torn up and full of rocks to get it out and see how it runs at highway speeds but around the sub at 0 - 50mph nice accel and with my little one saying squeak the tires papa, we made sure there weren't any nibs left

[Duke W.]

Re: 1966 L36 Vacuum advance Mechanism

It sounds like you are getting there. The centrifugal should have a total of about 30, but it's non-linear.

Try the weakest springs. If it doesn't detonate...

The quicker you can get the centrifugal in - without detonation - the stronger the low end torque.

Duke

[Clem Z.]

Re: 1966 L36 Vacuum advance Mechanism

you can speed up the mechanical advance by removing one spring and putting a "E" clip on that weight to hold it in place.

[Ronald L.]

Re: 1966 L36 Vacuum advance Mechanism

I'm going to try those soft springs tomorrow and if no rain, smoke-em'! I was a little surprised how it lit up today.

Is it possible it is a little sticky - what else could it be preventing advance? We can give it a blast of wd40 as well.

[Duke W.]

Re: 1966 L36 Vacuum advance Mechanism

Being as how your distributor has probably never been disassembled, overhauled, blueprinted, and lubricated in 45 years, maybe it's time.

The distributor is the most overlooked component on the engine. Most guys take them for granted and run them until they are junk.

Duke

[Ronald L.]

Re: 1966 L36 Vacuum advance Mechanism

Duke, I agree, exactly what I was thinking when I saw what appeared to be sticking today.

When the snow flies and I trash the edlbrock intake, nice way of saying the original intake goes back on that has been boxed for 34 years, this will get attention at that time.

We only have about 6 weeks left of good weather, so put the top down, turn up the heat and go for a drive! Never had an issue with being cold in a big block car