L88 Distributor Question

[Larry M.]

A comment on a recent thread prompts this question - What is the purpose of the vacuum-less advance unit on L88 distributors?

With no vacuum to it, it can't provide any timing advance, and therefore seems to be unnecessary.

Or does the unit contain some unknown-to-me mechanism that has a timing-altering function?

Thanks for indulging my curiosity.

Larry

[Timothy B.]

Re: L88 Distributor Question

My vote is that it's there to hold the points plate in a fixed position.

[Michael J.]

Re: L88 Distributor Question

I think it is also a part of Zora's edict that the L88 be made as driver unfriendly for normal driving as possible. He did not want people buying them as grocery haulers around town driving.

[Duke W.]

Re: L88 Distributor Question

Correct. Without a VAC or something equivalent, the breaker plate would be free to rotate.

The L-88 was never intended for road use. It was a pure racing engine meant to spend most of its life at WOT, so idle and part throttle fuel economy were not issues. Also, GM was concerned that with a vacuum advance, detonation could be an issue under some throttle/manifold vacuum conditions, so they took the expedient path of just cutting off the nipple to preclude anyone from connecting it.

The HEI on my Cosworth Vega did not have an OE vacuum advance (but it does now). To keep the stationary pole piece from rotating there was a plastic piece shaped like the VAC bracket. I always assumed it was already an existing part - maybe for marine applications, but apparently GM never made an equivalent piece for the single point and TI systems.

A lot of racers back in the day brazed the breaker plate to the dist. housing and didn't need a VAC to function as a breaker plate locating device.

Duke

[Larry M.]

Re: L88 Distributor Question

Thanks, all, for your replies.

Seems like it would have been less costly for GM to produce a small bracket or brace to hold the breaker plate stationary, rather than use a larger, modified vacuum advance.

Then again, the cost to develop and manufacture such a bracket for such a low production engine probably wasn't worth it.

Larry

[Wayne M.]

Re: L88 Distributor Question

Here's how they anchored the plate on the ball bearing distrib (w/3 screws). Part # 1111263.

[Ed H.]

Re: L88 Distributor Question

On the 1957 fuelies and the 2x4s there was no VAC advance, the springs and small MECH advance could be modified
to allow a faster advance. This was an old drag racing trick. I used it on my 57 and 60. Got you out of the hole quicker
along with Olds 4.88 rear gears. The 60 was a 10Sec, 130 MPH vette. Long live Lions Drag strip, Long Beach Ca.

[Mike Z.]

Re: L88 Distributor Question

GM from 63-into the 90's did not issue a V-8 distributor (line unit) that did not have a vacuum canister, albeit even if it did not function i.e., L-88 & ZL-1, equipped with the #373 vac canister. Only Over-the-Counter units i.e., #095 (no tach drive) & #263 (tach drive). which were intended for race applications were designed without a vac canister. To further enhance the race application; GM design these two units with a ball bearing at the top, but maintained a bushing at the lower position. Further, the coil P/U was mounted directly/securely to the housing-these units are rock solid to 8000rpm test limit of my Sun distributor machine.
It is my opinion; from working on these distributors for many years and thinking about this question: the canister on the L-88 & ZL-1 was designed into the picture to orientate the coil P/U to the cap position slot, which lead to positioning placement of the spark plug wires into the cap. On the #263/095 units, one could place the wires in any position as long as the firing order was maintained and then worry about timing. On the line, they did not have time to worry about wire position or timing position.

[Tom D.]

Re: L88 Distributor Question

https://www.forums.ncrs.org/showthread.php?120950-1-spark-plug-wire-placement-on-69-427-435&highlight=L88+distributor

This other discussion includes my photo of an L88 distributor.