Hope someone can help me out here, I dont know much about distributors or HEIs. I have a couple issues

I have an HEI (orig GM) in my 72 SBO. There is a lot of play at the bottom (see arrow in pic). Can / should this be shimmed out ? I have seen dist shim kits for sale (mr gasket I think) where do the shims go, in that gap, or at the top ? how much play should there be? there is about 3/32 or 2-3mm there now! Has it worn a groove where the second arrow points to?



second issue the Vac advance was to much (30° I think based on the 30 on the VA bracket) and I would get some detonation at part throttle particularly up hills, so i havent been using any VA at all. I limited the travel of the VA to about half (see pic) is that OK will it create any other issues ?



I know I can get an adjustable VA, but none are speced ie how much VA and at what vacuum level plus they cost almost as much as a new "ebay HEI" w adj advance . well just get that then kid, I dont want to support china and I already have a functioning unit Im just trying to improve on what I have!!!

any helpful tips or pointers to sites w info appreciated thanks

 

I've all ways read that is the side to side movement you don't want. The up and down travel might be too much but I don't know. I've never shimmed an Hei. Don't know why you would, but you did take a good picture, and sure looks like some wear. 3/32'' or 2-3mm sounds about right to me.

I see nothing wrong with your limiting the VA. I've done something like that before. I can't believe a crane adjustable VA would cost you that much. I have one, didn't take more than one afternoon to dial in. It comes with instructions. Remember, every combination is gonna be a little bit different considering temp, altitude and carb settings when adjusting your VA just right.

Have you experimented with full manifold vacuum and ported vacuum to compare?

 

Looks like one of the springs on top
has been replaced with one
that may or may not match.
Could have something to with
the pinging?

 

thanks for the replies.

I dont really know much about dists but the up down play seemed like a lot and I know they sell shim kits so thats why I asked, the side to side play is very small and not measureable w any tools i have.

the crane kit is ~$38 at summit click for link to all VAs at summit there are other cheaper ones like the moroso one for ~22, but if the rest of the dist is worn I could get a new one on ebay for 50 w adj advance but chinese. moneys tight so I only spend what i need to, I think I can get what I want with what I have just need some experience to help me get there

I initially had the VA connected to ported vac but from my bench testing it comes on at ~5 in HG and is all in (30°) at ~13in HG, so I would guess that at all but just about WOT its giving me some advance. I intend to run the VA on full manifold vacuum once its limited to ~13° or so.

The springs are 1 mid 1 light from the moroso (made in CT USA BTW) advance kit. Initially when I bought the car there where some thin stamped weights and heavy springs (and just about no mech advance as a result) so i started there w the moroso kit (nice weights like GMs and 6 spring choices) 2 light springs showed me advanceing at idle 2 mid springs showed me no advance till ~2k rpms, 1 mid 1 lite springs shows mech advance starts at ~1400 rpms and is nearly done (~16°) by 3500rpms.

The amount of mech advance in the HEI led me to bump my intial to ~18° so intial plus mech = ~34° add 30° of VA you got some problems so thats why Im here now.

Im thinking VA limited to ~13° will put me right where I want to be around 46-48° total.

 

You probably don't need to worry about the shim as the Olds distributor turns CCW and pulls down.

To properly figure the correct vacuum canister, we need to know what your total mechanical timing is set to. Normally your total mechanical is around 36 degs all in @2800-3000 rpm. Your optimal timing idealistically would be for your total timing, initial+mechanical+vacuum= around 50 deg btdc. Most people are using a Crane adjustable vacuum canister, which makes changing the settings pretty easy.

Or you can use one of these and just limit it.

http://www.summitracing.com/parts/CRN-99619-1/

 

yea, I didn't catch that. It looks like someone has been in there before trying to taylor the mechanical advance. Looks like a medium and a light spring. Thats part of tuning these. You gotta try different spring combos. So with that said, changing one or both springs might do something for you. It could make it worse, but that's the joy of hotrodding.

Edit...I was incorrect earlier, I'm using a moroso adjustable VA-works the same.

 

Ditto that its got a curve kit on that distributer.

 

Olds distributors do NOT need to be shimmed for axial play - that's a "C-word" thing.

Radial play is another thing, though - there really shouldn't be any.

It sounds like your bushings are worn out. They make bushing kits for these, but honestly, since the distributor is not unique or original, and is not really dialed in, you might as well just pick up another one at a junkyard for five or ten bucks.

It's fine to put a stop on your advance like that, but I would recommend monitoring your operating vacuum levels and checking your advance's curve, and using that information to try to tune it that way.
I'm surprised that the Crane kit costs that much. Have you checked Amazon and eBay?
I got mine for $10 at a flea market.

- Eric

 

i have NOS olds distributor housings and shafts. transfer your guts and you have basically a new distributor. .. .pm if interested.


bill

 

Thanks for the replies and ideas...here is what i ended up with.

stock original 72 350 engine w RPM intake and ebrock 1405 carb;

GM HEI probably from a mid 70s car.

~17° initial
~16° mechanical all in by ~3500 rpms
~8° vacuum advance to manifold vacuum starts at ~5" all in by ~13"

Car starts easy hot or cold and runs good, transitions from closed to WOT smoothly at all rpms, cruises at speed very well too.

The settings are little conservative but the car is running very good now so i think i will stay w what I have, I plan to replace the 350 this winter. I think the adj vac advance would be the next step if I were to keep this set-up as i could use a little more vac advance but the permanant stop method is too much of a PITA to change, it did allow me to run some VA for now tho. Before w no stop on the VA it was like 30° of advance and was just to much so it has been disconnected.

 

Cool. Sounds like you got
it for now. Drive and enjoy.

 

Conservative is not bad if your just cruising around town.

 

Yea I'd enjoy that too.

Nothing wrong with trying a little more initial timing when things cool down this fall. Try to keep track of your mileage, you might be able to improve on it too with some VA. Have fun.