Reproduction 1115355 vacuum adv.

[Larry M.]

I want to change the vacuum advance on my 66 327-300hp powerglide. I see LIC and Paragon sell a reproduction 1115355. Has anyone purchased this item and are there any problems with them? Thanks for any info. Larry....

[Duke W.]

Re: Reproduction 1115355 vacuum adv.

There have been a number of reports that "reproduction" VACs don't met the OE specs for the part number. I'm not sure about this repro of the 355, but you should ask the for the specs and get a guarantee that they are correct.

Approximately 0 @ 8", 16 deg. (crankshaft) at 12". (And these specs are well "tuned" to a 300HP/PG. For a 300 HP/manual trans I recommend the B22 which is 0 @ 8, 16 @ 15")

You can buy a B20/B26, which has these specs for about ten bucks. The VAC is worth three points - two for originality and one for condition. IMO a B20 or B26 VAC is a one point deduction.

So, is it worth the risk and cost for one point?

Duke

[Edward J.]

Re: Reproduction 1115355 vacuum adv.

Duke, talking about vacuum advance canisters, could you give me the spec. on my 63 327/340 corvette, I will be starting up the rebuilt engine this week, I did stay with the stock compression and camshaft profile.I believe that the vac. canister is the factory, and did at least test vacuum dia. for operation after I cleaned and lubed the bushings and tach drive gears.

Or should I consider a different vacuum canister for running ethonal gas?

[Dan H.]

Re: Reproduction 1115355 vacuum adv.

Be careful with the repro VAC's. I had a '236' one that didn't quite match the designed vacuum specs. After about 2K miles it ruptured the diaphram. Luckily I was home when it went out. Have a couple nice NOS ones now, never a problem anymore.
Dan

[Gene M.]

Re: Reproduction 1115355 vacuum adv.

[QUOTE=Duke Williams (22045);............. The VAC is worth three points - two for originality and one for condition. IMO a B20 or B26 VAC is a one point deduction.

So, is it worth the risk and cost for one point?

Duke[/QUOTE]

I think you will find that the number stampings are incorrect and no part number derivative as well as the front face stamping configuration is wrong. With that much wrong might as well find one of the old Crane adjustible vacuum canister and be able to dial it in.

[Ronald L.]

Re: Reproduction 1115355 vacuum adv.

I got one last summer, unless you have a microscope you can't tell the difference - and - it works just fine.

I would expect they are all coming from one place, LIC has them made if I remember correctly.

[William C.]

Re: Reproduction 1115355 vacuum adv.

I've had a number of the reproductions on my machine from various folks, and some are OK and some are WAY off. Particularly troublesome on the SHP engines that don't pull much vacuum at idle. Fixed a couple of engines that would not idle with a good vac. can.

[Duke W.]

Re: Reproduction 1115355 vacuum adv.

Duke, talking about vacuum advance canisters, could you give me the spec. on my 63 327/340 corvette, I will be starting up the rebuilt engine this week, I did stay with the stock compression and camshaft profile.I believe that the vac. canister is the factory, and did at least test vacuum dia. for operation after I cleaned and lubed the bushings and tach drive gears.

Or should I consider a different vacuum canister for running ethonal gas?

I've stated many, many times before that the OE '63 340 HP VAC is not properly matched to the engine's idle vacuum characteristics. The OE 201 15 is 0@8", 15 @15.5", but the Duntov cam only pulls 12" at idle so it doesn't meet the Two-Inch Rule. I figured this out and replaced my OE 201 15 with a 236 16 in 1965, which solved the chronic idle instability problems.

The modern OE replacment equivalent to the 236 16 is the B28, but I understand they are getting hard to find. Some who have purchased recently may be able to give you a source.

As long as you're rebuilding your 327/340 why not massage the heads and install a LT-1 cam. It idles the same at a Duntov cam, but you will have useable power to 7000+.

And don't forget to replace the weak OE rods with something better.

Do some archive searching for more info.

Duke

[Duke W.]

Re: Reproduction 1115355 vacuum adv.

Be careful with the repro VAC's. I had a '326' one that didn't quite match the designed vacuum specs. After about 2K miles it ruptured the diaphram. Luckily I was home when it went out. Have a couple nice NOS ones now, never a problem anymore.
Dan

I think you mean a "236".

Duke

[Duke W.]

Re: Reproduction 1115355 vacuum adv.

I think you will find that the number stampings are incorrect and no part number derivative as well as the front face stamping configuration is wrong. With that much wrong might as well find one of the old Crane adjustible vacuum canister and be able to dial it in.

The current "B-series" VACs that are made by SMP and sold by all the brands including Delco at least have the same dimensional geometry as the OE VACs even though some of the construction details may be different.

I don't think most of the aftermarket adjustable VACs even look remotely similar, so I would take a full deduction - two for originality, which means none for condition.

There's no reason not to install a B-series VAC. There is one of only a universe of THREE that is properly matched to any OE pre-emission engine, and those same three are applicable to any OE engine that is converted from ported to full time vacuum advance. I've posted the list, here, several times.

If one has an aftermarket cam in place of OE - just use the Two-Inch Rule.

Adjustable VACs are for people who don't understand the single simple fact required to select a proper VAC, and it's been discussed enough, here, that everyone should know how to do it or search for the answer.

Duke

[Duke W.]

Re: Reproduction 1115355 vacuum adv.

I got one last summer, unless you have a microscope you can't tell the difference - and - it works just fine.

I would expect they are all coming from one place, LIC has them made if I remember correctly.

Did you actually test it to determine if it meets the 355 spec?

If not, how do you know it works "fine".

Duke

[Dan H.]

Re: Reproduction 1115355 vacuum adv.

I think you mean a "236".

Duke

OOPS, that's the one Duke!

[Michael H.]

Re: Reproduction 1115355 vacuum adv.

As long as you're rebuilding your 327/340 why not massage the heads and install a LT-1 cam. It idles the same at a Duntov cam, but you will have useable power to 7000+.


Duke

Oh, here we go again.

[Jim T.]

Re: Reproduction 1115355 vacuum adv.

Duke I still have the original vacuum advance unit in my 68 327/350 L79. Removed the distributor to install new lubricant in the upper cavity of the distributor.
When the distributor was left laying on it's side oil drained from the vacuum cannister.
Have no idea of how the oil got there. Any ideas or knowledge of this occurance.

[Duke W.]

Re: Reproduction 1115355 vacuum adv.

The only thing I can figure is that some oil ingested from the PCV system found its way into the VAC, or it could be some of the heaviest components from fuel, which can look like oil.

I'm not sure how resistant the VAC diaphragm is to petroleum compounds. I know some rubber parts in brake vacuum boosters can fail due to oil contamination. In the mid seventies, GM added a small activated charcoal filter to most power brake supply hoses to absorb hydrocarbons. It's about the size of the small cannister filter (GF90 I think) that was used on '63 300/340/360 HP engines.

BTW, the OE 236 16 VAC on L-79s is more aggressive than necessary. I recommend replacement with the 12" B20 or B26. Since the L-79 typically pulls about 14" manifold vacuum at 750 RPM idle, a 12" VAC meets the Two-Inch Rule.

I recommend you check that OE VAC with a Mighty Vac to see if it holds vacuum

Duke