Thanks f-bird that's the best explanation yet! This should be a sticky, the msd part number is 8463 I can't post a link to summit because I'm posting from my phone. The vacuum can from bolt holes to rod is shorter than most I've seen, I emailed summit , they said they didn't have an adjustable vacuum can that fit? They may not know that they do. The combo is a 454 BBC, ls6 short block, 254/263@50 duration 620/629 lift, 3500 convertor, 3.73 gears , 325/50 bfg radials, 10.5 to 1 compression.

 

OK I am as we speak right in the middle of setting my mechanical advance limit. I agree with you Fbird my setup likes allot of initial so I must limit my mech. I have a off shore HEI that is most likely the same as thousands out there, not sure how it compares to the OP's but it may help others too with the same. I am shooting for 34 total on my vortec head 383 with 221 duration @ 50. I would like 20 or 22 initial/base so if I can add say 12-14 with the mech then lets try that. This HEI will not accept a bushing kit so I am using a small machine screw/nut through the rotor plate, the head of the screw will butt against the advance plate stopping its movement. This HEI had over 20 deg mech to start with. I would like to see if I can ball park this stopper with the dist. out of the engine by using a degree method. I have installed a pointer on the rotor plate and measured the movement of the pointer from no mech to its limit. The diameter of the dist body is 132mm, the travel of the pointer is 17mm, If say 6 deg on the pointer makes 12 at the crank right? or is it the other way around? how close am I? I would like to use some math to see if I have the right deg movement...anybody?

 

Well I am answering my own question C/D= 3.14 were C is circumference and D is diameter so 132 X 3.14 = 414.5 divided by 360 = 1.15 mm per deg approx so I get 19.55 deg movement is that 9.8 crank Deg? looking for some confirmation. Am I on the right track here or will this little exercise shoot itself in the foot somehow?

 

I should note that I respect the initial OP's question on vacuum advance and although my post does not address this directly yet, this may be useful if he is setting up the mech limit first off to get to what Fbird is making posts on, I will try and keep it relevant and add some vacuum adjustment details as we go along if need be

 

Ya the distributor runs at half crankshaft speed.

OK I have tweaked the stopper to get about 21mm movement that should equate to approx 12 deg at the crank thanks to mechanical. I will post when I get it in and set the light on it. Thanks

 

Ended up with 17 deg added by mech on the running engine with the 21mm advance travel. In this case I will set my base at 17 as well to get my 34 total without vac advance. My cam is not that big so this is OK for now but I may want to get my base up further sometime, that means getting back in there and changing the stop point...again. SO 21mm/17deg = .81 wonder if we can use this ratio? would setting the mech movement limit to 15mm travel have given the 12.15 deg I was looking for? (15 x .81 = 12.15) just a ballpark procedure maybe

One thing I found was that my adjustable vac can had a slow leak, it would bleed down really slow, the leak was were the sleeve for the hose meets the vac can, the OEM one I replaced it with is one molded piece or at least braised at this connection and tested good, by the way it adds another 22 without a limiter so back in I go once I get a new adjustable can.

 

Hmmm, still looking for an adjustable can for 836
1 msd dist. as stated in the thread title.

 

Yeah got ya, did not mean to fill your thread with my own ramblings should have started new one on this, was relavent to a point but not helping you much...my bad.

 

The vacuum can needs 15 inches to pull timing advance my BBC only makes 7 to 10 inches. Has anyone found an adjustable vacuum can that fits this dist. I chatted with sales at summit racing they had no luck finding anything that fit. ain:

Can you show a photo of it w/a ruler in the shot- there may be a GM (or other) can that'll fit it.

Summit sells a can- http://www.summitracing.com/search/...rch/Brand/MSD-Ignition/Product-Line/MSD-Vacuum-Advance-Mechanisms/?autoview=SKU

But doens't say it is adjustable, and I take it you've checked yours for an adjustment?

EDIT- Does it look like a GM points unit?

 

Can you show a photo of it w/a ruler in the shot- there may be a GM (or other) can that'll fit it.

Summit sells a can- http://www.summitracing.com/search/...rch/Brand/MSD-Ignition/Product-Line/MSD-Vacuum-Advance-Mechanisms/?autoview=SKU

But doens't say it is adjustable, and I take it you've checked yours for an adjustment?

EDIT- Does it look like a GM points unit?

Just fyi if you are referring to Idle vacuum 7-10" with that much cam is normal and does not affect the vacuum advance... driving at cruise speed say 40 mph with a vacuum guage to ported vacuum (light throttle) you'll see 15-18 inches (above 2500 rpm) you will then be above cam overlap issues the allen wrench you got in the box will adjust the advance stop built into that distributor Good fuel and conservative timing will keep you're motor intact ...TT

 

A little hard to tell from these images. The HEI can has a longer bracket than either of these- and the two are not interchangeable. I bet the points-type GM can will fit the MSD distributor, though.

ACCEL ADJUSTABLE GM POINTS-TYPE

MSD REPLACEMENT

 

The 8361 uses a GM point style vac can. So a Crane 99601-1 will do the trick



*

 

Tanks cobalt, those are good pic's, just need someone who has one running with a different can that's adjustable.

 

perfect, thanks greg t and fbird, ordering this week.

 

perfect, thanks greg t and fbird, ordering this week.

The 99601-1 is out of stock at Summit. Should ship by about the 10th. I'm waiting for one.

 

Update, ok f- bird I have 26* initial with 10* mechanical advance now. I have a vacuum guage plumbed into the car to map varying rpm, I have the crane adjustable vacuum advance can and limiter plate. Here's where I'm stuck, how does the plate fit under the inner screw by the rod? I cant seem to find an orientation that has enough room, looks like the can fits perfect but the limiter plate is too large for msd pro billet 8361 dist. Anybody get this plate to work? Cheers Tim.

 

Don't know why my post was quoted in that it has nada to do w/your response, but just FYI this thread is way old, I'm guessing the OP's issues have been resolved by now....:mwink: