Your distributor rebuilder is in error with his use of the 163 VAC. The VAC you need is the Standard Motor Products VAC P/N VC 177 stamped B28. Do you know what ignition map your builder customized? The stock map for your engine w. 30-30 cam & advertised 11-1 compression is

Start @800 RPM
24* @2350 RPM

 

I'm starting to think so..... though he claims this is absolutely the correct can that he uses on all of the 30-30.

He reminded me that he sent a cert with the unit which I do recall seeing. I will look for it when I get home.

 

I found the report and it reads.

24 deg @ 2600

He only gives the totals

Well this looks right, I'm not sure why it would exceed 36?

Btw there is a brass bushing in slot location.

 

I have been following this thread. I have the same issue. Too much centrifugal advance.10 degrees more than I should.
I have the accel bronze bushing in it. I am thinking my slot needs work.

 

Donald, no offence is intended, but the vacuum advance has nothing to do with RPM. it only has to do with vacuum in the intake. cruising down the freeway at 3000/3500 just maintaining speed will give you full vacuum advance (the manifold will have high vacuum because of the light throttle to just mantain speed) Now at full throttle at say 5 grand there will be no (or almost no) manifold vacuum, thus NO vacuum advance. it is really a great system, the centrifigal is RPM related and the vacuum is load related, they both work independently of each other but when set up properly will give the right timing for every RPM/load condition.

the best posts (and the most right posts that go into great detail) were posted by 63 340HP, it would pay to reread them!!!

in the 60s advance kits were not even around, as mentioned in a post above we always brazed the advance slot and filed to get the initial/total spread. we shimmed the dist shaft to .010 (commonly they had over .120 of play) i have realized for a long time that this is stupid, the gears on the cam and dist. hold the dist. shaft in timing under load, but i still shim any distributers because that is what i have always done.

there is no absolutly correct timing on any engine as some people say. every engine is different. generally on small blocks like somewhere between 34/36 total is acceptable now days with modern heads. back in the old days with cast iron fuele heads and leaded gas the spark plug was shorter 3/8s, and the engine required more lead when. now days with the smaller longer reach plugs require much less lead...

 

I have been following this thread. I have the same issue. Too much centrifugal advance.10 degrees more than I should.
I have the accel bronze bushing in it. I am thinking my slot needs work.

Makes little sense to me why this is the case for us.
What's involved in getting this plate out?

 

24* of centrifugal advance at 2600 rpm is fine; with 12* initial, that'll provide 36* total timing.

 

yes, John I agree, sounds good on paper but it's not reacting that way.

I want to get the B28 can but 2 FLAPS can not locate it based on all of the P/N's floated about in this post. Anyone know how to reference or a particular Chain Store Name?

 

There a number of things that can get miss-applied when a Technician is running a Sun machine. The easiest mistake (due to inexperience or a lack of training) is the Technician failing to account for the distributor running off the camshaft at half the crankshaft speed (the old farts can laugh, but CRS hits the trainers sometimes too, and any fool can run a machine incorrectly if not trained properly).

This difference in speed is accounted for in the distributor setup by differentiating "distributor degrees" with "crankshaft degrees." In the above discussions we have all been referencing crankshaft degrees of advance timing.

When you are working over a distributor on a Sun machine (or working with a stone age angle-gage) the distributor set up is in "distributor degrees", exactly half of the crankshaft degrees. 12 distributor degrees of advance plate movement in the distributor equals 24 crankshaft degrees of advance on the engine balancer.

The problem may be the Technician set up your distributor with 24 degrees of advance, and you have 24 degrees of distributor advance (that equals 48 degrees of centrifugal advance at the crankshaft). It's a long-shot to make this mistake, but Columbus never sailed all the way to India and his voyage was also considered a success (stuff happens).

An exploded view of the distributor is very helpful to learn how to disassemble the distributor and inspect the advance plate. Maybe someone can post a link to a drawing (anyone?). The only trick to the assembly is to mark and note the orientation of the distributor drive gear to the shaft. The gear can be spun 180 degrees on the shaft, and it changes the gear tooth alignment by 1/2 a tooth (just enough to make it near impossible to properly rotate the distributor to get correct timing without hitting the manifold or coil bracket).

Good luck with the task at hand (there a a lot of sharp folks on this forum to help).

 

I would try a FLAPS that has access to the Standard Motor Products warehouse. As of last Feb 2010 there was one left at the Deauville (sp), Va. warehouse. The VC 177 from what I hear is discontinued and only remaining old stock is available.

Also try GM Parts Direct. GM P/N 88924985

 

I bought my b28 vac can from GM Performance parts about 8 months ago. Get the right part# from a forum member and it will show up there. I don't remember what # I used.


http://www.gmperformanceparts.com/

 

try here for a B28 vacuum cannister:

http://www.gmpartsdirect.com/
part# 88924985
price is $5.99

 

I special ordered DV1810 through Auto Zone using some cross reference numbers posted a while back. It's labeled as made by WELLS and has B28 on it.

 

The NAPA-Echlin number is VC1810, not VC177, and it was discontinued over a year ago.
If you cannot find one of these, then you have 2 choices:

1. Get a reproduction 236 can, such as this one (catalog #4756)
https://www.paragoncorvette.com/c-22...aspx?pagenum=4
Caution: I have had occasions where these lasted less than a few thousand miles before the diaphragm ruptured.

2. The better option, if your car is not concours stock, is to use this adjustable unit from Accel.
http://www.accel-ignition.com/Produc...xtSearch=31034
I currently have it installed on my distributor after pulling a ruptured 236 reproduction control.

According to the report from your distributor guy, it is set up correctly. Either you are reading it incorrectly, or he is lying to you. Are you SURE that you are not getting vacuum advance at idle? It sure sounds that way. Assuming you have (about) 12 initial, 17 vacuum, and zero centrifugal, then you will be seeing about 29 at idle.

When do your weights begin to deploy? Tie them so that they don't move and recheck, with your vacuum can disconnected and plugged. With 24 centrifugal and 12 initial, you will be in the "sweet spot" with 36 total.

Here is what you should be shooting for. This is a conservative distributor setup, but was the factory calibration:

 

[QUOTE=65tripleblack;1574899841]The NAPA-Echlin number is VC1810, not VC177, and it was discontinued over a year ago.


VC 177 is the Standard Motor Products P/N for the B28 VAC

 

Thanks I will order as indicated.

I'm sure no vac since it was disconnected and plugged. Also, it not working when connected now makes sense since it was the wrong can.

I guess there is a possibility that there is centrifugal at idle as I did not tie them, but I don't believe so since the timing behaved normal when I adjusted it throughout the timing tab and it seemed steady at all rpm, but you do have a Good point that I will look into.

Actually the distributor guy suggested that I raise the idle so that they do open, lower the initial timing,and in turn create more vacuum to pull the diaphragm. This sounded like a bubba balancing screwy act to me so I told him I don't think so.

Next I'm going to increase the valve lash from .023 to .026 cold to try an increase vacuum as suggested. Then I will replace with the b28 can and start again. Thanks for everyones help

 

It's also AC-Delco #D1312C (it comes in an AC-Delco box with both the GM and AC-Delco part numbers on it); I buy lots of them from GMPartsDirect.com.

 

Ok, I bought a dozen of the B28 cans...

Installed and I now have vacuum advance!

I adjusted the valves to .026 cold and I had in a quick check (need to get a vac. T) 9 in on gauge which was a good move.

I also installed a Mr. Gasket timing tape and still have about 42-44 deg total advance despite what the rebuilder guy said about 24 deg set up on the dist. (12 static)

It seems to run well at 12 deg now but I may try to set it at 36 and make the initial whatever I get . Will this affect the idle, cooling etc. even though the vacuum will advance it? OR should I adjust the slot on the advance plate?

 

Go for the slot. If you pull the static timing back to make up for the excess mechanical advance, you'll have a lazy idle, lazy engine down low.

 

In the short term run a better grade of fuel (for improved detonation resistance) and tune the initial timing for the best idle (so you can continue to enjoy driving the car).

Too much timing advance can promote detonation (pinging you can hear), and it can lead to overheating (high temp effects you can see under load), and it will cost you WOT power (bad, if you were in competition). Keep your foot out of the throttle and these issues are minimized as it will reduce the potential for engine damage until you find a good distributor tuner (and also reduce the fun factor).

Find someone in your area than can braze & restore/tune the length of the advance slot, or tackle it yourself. With the tools & knowledge you now have (timing tape, etc.) you can tune the distributor yourself (if you or a friend is handy with a torch and brazing rod with a few files and/or a Dremel tool, if you have patience). As 65tripleblack mentioned, you do not need a Sun machine or special tools to custom tune the distributor for your engine combination (just patience and a will to tinker until it's just right).