hi all

there have been numerous posts recently about people not being able to get the timing and mechanical curve settings they have desired from their distributor. In one thread in particular we went thru 1 1/2 pages before discovering that the "short" 16º mechanical advance the poster was having an issue with wasn't really an issue after all but rather the actual correct factory specs on his particular model distributor.

In most cases for our street driven cars a timing set-up of at or close to 36º total timing with a 24º mechanical advance is going to give us good performance. This set-up will also allow initial timing to fall at 12º. These settings are before reconnecting the vacuum advance cannister.

This is not the way a lot of the distributors came set up from the factory and many had much shorter mechanical advance curves set-up, some as short as only 14º. If you leave the factory mechanical advance set the way it is and try to set timing by setting 36º total than your initial timing will typically be too high. If you try to set timing by seting for 12º initial than your total timing would be too low.
The mechanical advance can be adjusted by the use of different pinstop bushings inside the distributor. I bushing with a smaller outside diameter will increase your mechanical advance and a bushing with a thicker outside diameter will decrease your mechanical advance. In come cases you may even have to try running with no bushing at all to achieve the desired mechanical advance you are looking for.

If you are trying to set up your distributor and running into an issue of your mechanical advance being to short or limited, you may wish to first check the specs on your particular factory distributor and than see what you need to do to adjust from there.

I've just posted up on my website tech page a new tech paper that gives the factory timing curve specs on the various distributors between 1963-1973 if you need to research this data.

http://69.253.166.197/page1/page65/page65.html
the file is called: Distributor Curve Specs.pdf

**NOTE & Disclaimer: Before a lot of people start complaining about my desired timing specs listed above of 36º total with a 24º mechanical advance allowing for an initial timing of 12º I'll state right now that this is not for every single engine out there. If you have a heavily modified motor your desired timing specs my be different. This timing set-up is good for a stock or close to stock motor set-up. Even than in many cases it's only a starting point you may have to fine-tune. Some motors can let you go up to 38º total before detonation and others may only allow you 34º or so before you run into detonation issues. Some may find that if your initial timing is slightly higher or lower (therefore the mechanical advance needs to be adjusted accordingly) you get better performance, etc.
As always you need to find the set-up that works for YOUR car but again this is usually at least a good starting point to work from.
**The point is it's nice to have the specs on your distributor to start with.

If this info is handy for you, please enjoy it and make use of it. If it's not important for you than feel free to ignore it and don't complain about it.
Thanks!

 

I'll have to really look this over when I have time. Thanks for posting the info.

Gotta like the disclaimer you put in. That should save pages of discussion.

 

Holy smokes Barry, you have a lot of great links on your page!

 

Many of the older points style distributors will have too much centrifugal available in them. These distributors will need to have centrifugal advance pulled out of them. No biggie but in some cases you may need to braze the autocam slot a bit.

Some of the later HEIs will have not enough centrifugal advance. You need to add some centrifugal into them. I have recurved several of the points style distributors and 1 HEI. The HEI needed slightly different style kit to get the right amount of advance. Pertronics makes a very nice HEI kit that worked well for me. I had trouble with the aftermaket electronics they supplied so I kept the GM coil/module but the curve kit was very nice. Just swap the autocam and weights and presto you have 21 degrees centrifugal. These weights look to be better than most of the other kits I have seen. probably not advisable to reuse the GM weights with this kit if you want the right amount of centrifugal advance.

For what it's worth.

-Mark.

 

that was the idea........... otherwise I KNEW I'd have countless posts telling me that the listed timing set-up didn't work for THEM, etc, etc, etc and that just distracts from the point of the thread and the info

 

Boofers, thanks. make use of any of the info posted on my website. It's there so everyone can benefit from it.

Stingr69, that's true. On many distributors the cam slot has been elongated either from usage or from being deliberatley modified to increase the advance. sometimes a larger bushing will correct this and other times it needs to be welded or brazed to reduce it. My '65 had to be welded shorter as it was giving me 32º advance because of a previous ownner who opened it it up too far - Bubba is everywhere at times.
Usually, if the advance is too short a smaller bushing or removing the bushing altogether is enough to increase the advance enough to where you need it.
As for weights, it's my understanding so far that most weights found in the recurve kits are completely wrong - the amount of the weight and the geometry of the weights is incorrect. It's usually best to retain the original factory weights and if needed just change out bushings and springs to adjust the curve.

 

I would agree to a point. The older style points distributors need to keep the factory weights and play with the slot/bushing setup to get where you want to be. Use the factory weights here for sure.

The later HEI centrifugal advance mechanisim is different. The autocam plate is easily removable on these distributors. The remove and replace kit that I bought was very good. It used a new autocam, new weight pin bushings and new black oxide coated weights. The weights glide on nylon buttons so they do not wear quickly. No real guess work here just dissasemble and reasemble to get the 21 degrees which is about right. No slot to braze or file fit on these. Pay attention to the correct rotation direction when reasembling it but that is about all you have to worry about. No wear issues that I have seen yet. MUCH easier than doing a recurve on a points style centrifugal advance mechanisim. Select the springs so they start at 1200 RPM and finish by 3000 RPM and start testing.

There are some junky curve kits out there but this one I used on my HEI is not bad at all in my opinion. Your results may vary.

-Mark.

 

Mark

you may be correct, honestly I wouldn't know on the HEI's too much. I'd done some work on my '65 point's distributor but on the HEI in my '78 I've never fooled with it at all other than taking it out while doing my motor clean-up and reintalling it. Was never inside it though - no reason as the car has less than 10,000 miles and it works perfect.

 

What I did with the aftermarket recurve kit I bought was I took a grinder to the 'autocam' to allow the weights to move further out, allowing a greater mechanical advance.

Obviously you do not want to modify your stock autocam. Also, it can be dangerous if you are not careful as you could end up getting engine pinging if you advance too much.

 

BarryK,
I have a 74 and checked the dist no last nite: 1112150 (L-82), which of course is just off of the "Distributor Curve Specs.pdf" list. Any ideas if/where the same info exists for the 74? Hard to extraplate as values listed are all over the place!
thanks

 

S489, sorry, I don't have the info on the 2150 distributor.

The specs I have are from a couple of pages from a reference book that another forum member scanned and sent to me. I just put them into an excel spread sheet and put them up on my website.
There are books out that should give references to most if not all of the the different distributors that were out so you may have to find one of those books.

sorry!

 

the 1111250 dist specs are
500 rpm 0-2deg advance
1000 rpm 10.5-12.5
2200rpm 13-15
note these are dist rpm and advance specs which are doubled for engine readings

Barry i do have the delco remy 1.2 srvice manual so if you wish me to scan some pages i can. PM mail me with a e-mail address and the dist # range you want since i have 25 or so pages of specs with 65 or so dist #s per page

henry @ oles carb

 

thanks guys!!!