MSD Ignition 84281 HEI Vacuum Advance Stop Plate
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As a result, this product does exactly what it claims to do. I put it on a 302 sbf with a conversion hei distributor. The timing limitation estimates in the instructions, like those of other reviewers, seemed a little exaggerated to me. On my setup, the D notch allows for 11 degrees of advance at the very least. In order for it to fit, I had to use a grinder to remove the A notch. If you do your research, you'll find that there are essentially two products on the market that limit vac advance on hei style dizzy's. This one stops you from going too far forward at the top of your vac arm stroke. br>br>On the other end, the competitors' design does the same thing; I'm referring to the small toothed wheel that is held in place by a single screw. This one restricts vac advancement by forcing the vac arm forward, which means the vac arm will run out of travel due to its early start. By delaying the base timing, you can effectively cancel out the head start. br>br>Both products achieve the same result; however, they do so in different ways. You will undoubtedly have to re-tooth the toothed wheel. If the base timing is set correctly, this hooked wheel could be installed without the need to re-calibrate the engine. Establish a baseline for timing. While you're doing this, you'll probably be adjusting the centrifugal advance as well, so re-check everything. It's almost certain that you'll have to set a base timing. br>br>I've read that using the hooked wheel to limit the vac advance is preferable because it takes the timing out of the upper half of the stroke. In theory, this keeps the vacuum cleaner's adjustment range as narrow as possible. In my experience, the toothed wheel keeps the vac can in the sweet spot for adjusting the tension on the vac diaphragm, which is completely incorrect. br>br>If this review was perplexing, I would advise against taking on this project; if you stray too far from the original, it will be difficult to re-create. When you curve a distributor, you quickly damage the motor.
Giving 5 stars solely for the fact that it restricts the vacuum arm's travel; however, the directions and a- The term "d limit guesses" refers to just that: a guess. The vacuum limit is more of a guide than anything else, and it will most likely vary depending on the car/vehicle/etc. If you want to get a 10-percentage point raise, 12 degree vacuum limit, as I was, so I set mine to d, which was the least amount that required 5-minutes. According to the directions, it's 8 degrees, so, as someone else stated, I believe they're a little higher than expected, and I honestly don't think it'll go below 10 degrees.
This worked perfectly for me when I needed to limit the pull of my vacuum advance on my stock HEI distributor. The vacuum advance on stock HEIs is about 20 degrees, which is excessive for a high-end device. In a classic car, a high-compression engine with a carburetor is used. These high-quality products are Even with 93 octane, compression musclecar engines require 10 degrees of vacuum to operate properly. br>br>I tried a competitor's Crane unit, and while it worked as advertised, it wasn't the right fit for my application. The vacuum linkage, which preloads the spring in the vacuum canister, is pushed against by the Crane design, causing the vacuum canister to react poorly under acceleration. The MSD unit is different in that it prevents the vacuum advance from pulling past 10 degrees without a preload, resulting in a much smoother vacuum canister operation. br>br>In addition, the Crane unit's design shifts the vacuum advance's starting point 10 degrees forward, which threw off my initial timing. My distributor had to be rotated beyond its normal range of motion, and it collided with my manifold as a result. As a result, I was unable to set an appropriate initial timing. I had to remove the distributor, rotate the gear tooth to the next, and so on. It had been a multi-faceted project. I was stuck reverting to stock when the vacuum became choppy after an hour of work. The MSD unit, on the other hand, does not necessitate any of these complications; it simply plugs in and starts working. br>br>It took about 15 minutes to complete the installation. Remove the cap from your distributor, the rotor (2 screws), the vacuum advance retaining screw (the one at the end of the armature, use the screw to lock-in the vacuum advance), and the vacuum advance retaining screw (the one at the end of the armature, use the screw to lock-in the vacuum advance), and the vacuum advance retaining screw (the one at the end of the turn off the MSD unit, and then turn it back on again. It's just a matter of putting it all together. It's very simple to set up. I went with 10 degrees, but you can go with any of the four options available, ranging from 10-100 degrees. The temperature is 20 degrees. br>br>This unit comes highly recommended. It's inexpensive and effective.
It's great with my HEI distributor (which isn't MSD, but I'm sure it'd work with any HEI distributor). It took about 20 minutes to install and reduced my vacuum advance from 24 degrees to 14 degrees. It comes with four different settings that allow you to tailor the amount of advance you receive. You won't have to retime the engine every time you change this type of stop plate.
I don't believe the degree marks correspond to the information given. It's a tad higher, in my opinion. It allows it to travel quite a distance before coming to a halt, regardless of which position you use.
The package was delivered on time. easy and time installation time is short.
Otherwise, you'll have too much timing in your hot rod if you don't use it with your vacuum advance.
It does what it says on the tin and does not require engine retuning.
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