Hot Rods MSD distributor vacuum cans

Ever get tired of trying to tune your MSD distributor and use vacuum to increase the advance? I’m a believer in using vacuum advance on street driven hot rods. Yeah, I know it’s not strictly traditional, but it’s one area (like brakes) where I think cheating a bit is ok.
Long story short, MSD vacuum cans that come with the distributors I use are not adjustable and retro fitting another brand can be a bit of a hunt.
So what do you do when MSD says their cans give around 10* of advance at full suck and you’re getting closer to 20*?
Solution: take the damn distributor out, pull it apart, and modify the pull length. It’s a little nit picky, but well worth the time/effort.
Here’s my solution in pics to help fellow MSD suckers (pun intended).

1st up: make a little plug to weld in. Size is important (no matter what she said, haha), so always better to start with a little bigger.



Step 2: carefully weld it in.


Step 3: clean it up so it doesn’t interfere with the little bushing.



Note: I left one little corner non-welded so I could always go back and see how much I adjusted the pull length.



Final step: reassemble distributor and stab her back in.



I’m sure this isn’t a new solution, but if anyone else is dissatisfied with getting 18-20* advance out of a product advertised as 10* then I hope this method helps.

Cheers.

 

So you closed up the slot?

 

Made it shorter so that it limits the advance that the can will provide. It was either limit the travel in the slot or shorten the rod.

 

Nice work!
You have to wonder about aftermarket solutions that have fewer features than OE stuff.
I've got an MSD (?) pro comp on my junk. No vacuum can. I did a basic check of cap and rotor, but didn't dive in further. I should probably dig in and check what can be adapted and what curve I've got now.
This probably should get bumped over to the OT section, though.

 

My MSD fully open gives 17 degrees.I never did like the way it operated. With a bigger cam and low vacuum it would dither or pull timing sometimes at idle and sometimes not, so I just plug it off. I also use the black bushing, silver and blue springs which gives me 18 degrees for a total of 34 at 2600 rpm.

 

Ok, I read your post in reverse. Thought you wanted more timing.

 

I do the same on the HEI's only use alittle longer piece so it gets screwed down with the original mounting screw. I also slot the hole so I can adjust it a couple degrees either way incase 10* is not enough or to much.

 

Need to do something similar on the Duraspark distributor in the 351W. Weld up the advance slot, to limit mechanical. Will look at that when the engine comes out, for the newer replacement one.

 

This is good stuff. I did the same on the centrifugal in a stock GM HEI. And some outside mfrs. make MSD bushings to limit the centrifugal curve down to 10 degrees. Funny how MSD can't see the need for them.