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Shiloh101
Reviewed in the United States on April 12, 2023
I needed to reduce the amount of vacuum advance I was getting at idle from 18 degrees to something between 10 and 12. There are four different "tabs" on the unit each one corresponding to a different amount of travel reduction of the vacuum advance arm. This got me down to 12 degrees using the C tab. Fit perfectly and easy to install plus it doesn't mess with your base timing at all so no need to reset anything after you install it. It states on the packaging that this is for the MSD distributors but I used it on a standard GM HEI distributor with no issues.
tyler duran
Reviewed in the United States on March 9, 2020
So this product does what it states. I installed it on a conversion hei distributor on a 302 sbf. Like other reviewers I found the timing limitation estimates in the instructions a bit exaggerated. The D notch at the absolute minimum still allows 11 degrees of advance on my setup. Additionally I had to zip off the A notch with a grinder for it to fit.If you’ve done your research their are essentially two products on the market that limits vac advance on hei style dizzy’s. This one limits the advance on the top of the vac arm stroke.The competitors design does the same on the other end, I’m referring to that little toothed wheel that is held down by one screw. This one limits the vac advance by forcing the vac arm forward. This means the vac arm will run out of travel because it had a head start to begin with. You have to essentially cancel out this head start by retarding the base timing.Both products accomplish the same thing they just do it differently. The toothed wheel will definitely require you to re-set base timing, this hooked wheel could potentially be installed without needing to re-set base timing. Though you’re likely to be adjusting the the centrifugal advance too while you’re doing this, so re-setting base timing is likely inevitable.I’ve read that it’s better to use the hooked wheel to limit the vac advance because it removes timing from the upper portion of the stroke. This in theory keeps the vac can operating in its most sensitive to adjustment range. I’ve found that to be completely incorrect. The toothed wheel in my experience keeps the vac can in the sweet spot for adjusting the tension on the vac diaphragm.If this review was confusing, I recommend passing on taking on this project. If you get too far off on re-curving a distributor you’ll hurt the motor quickly.
Carl R Dunn
Reviewed in the United States on November 26, 2019
Delivery arrived on-time, easy & quick installation
KpierceND
Reviewed in the United States on October 26, 2019
giving 5 stars Based soley on the fact that it does limit the travel of the vacuum arm, that being said the directions and a-d limit guesses is exactly that, a guess. A-d vacuum limit is more of a guide than anything and will likely be different on most cars/ vehicles etc...if youre looking to achieve 10-12 degrees vacuum limit like i was i set mine on d aka the least amount that called for 5-8 degrees on the directions, so as someone else stated i think they are a little higher than expected and i dont think itll limit much less than 10 degrees honestly...
jay
Reviewed in the United States on November 18, 2017
Don't think the degree marks are accurate as to what is stated. I think its a little higher. It allows it to move pretty far before hitting this stop no matter which position you use its pretty far.
Emmitt
Reviewed in the United States on August 30, 2016
Works great with my HEI distributor, (which is not MSD, so I would believe it would work with all HEI distributors). It was easy to install, only about 20 minutes, and brought my vacuum advance down from 24* to 14*. It has 4 different settings to allow you to customize exactly how much advance you get. And with this style stop plate, you don't need to retime the engine every time you change it.
DeMaris Soto
Reviewed in the United States on May 5, 2016
U must use this with your vacuum advance or you will have too much timing in your hot rod
Paul
Reviewed in the United States on February 16, 2014
I needed a way to limit the pull of my vacuum advance on my stock HEI distributor, and this worked perfectly! Stock HEIs come with about 20 degrees of vacuum advance, but that's too much for a high-compression engine running a carburetor in a classic car. These high-compression musclecar engines like 10 degrees of vacuum, else they will ping under load, even with 93 octane.I tried the Crane unit (a competitor), and while it worked as advertised, it didn't work correctly for my application. The Crane design pushes against the vacuum linkage which preloads the spring in vacuum canister, and this made the vacuum canister react poorly under acceleration. The MSD unit works differently, it prevents the vacuum advance from pulling past 10 degrees with no preload, so the vacuum canister operates much smoother.Plus, with the Crane unit, the design pushes the starting point of the vacuum advance 10 degrees forward, and this changed my initial timing. I had to rotate my distributor past it's normal range of motion which bumped against my manifold. The result was that I couldn't set initial timing low enough. I had to pull the distributor, rotate to the next gear tooth, etc.. It was a multi-hour job, and when it made the vacuum can operate choppy, I was stuck reverting to stock. The MSD unit doesn't require any of these hassles, it just drops in and works.Total install took about 15 minutes. You remove the cap from your distributor, remove the rotor (2 screws), remove the vacuum advance retaining screw (the one at the end of the armature, use the screw to lock-down the MSD unit, re-assemble, and it's done. Very easy install. I used 10 degrees, but you can choose one of four settings, from 10-20 degrees.I highly recommend this unit. It's cheap and works perfectly.
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