1970 Vacuum Advance Control - Part # 1115357

[Clark E.]

In a previous thread I inquired about the correct vacuum rating stamping on the control bracket. The JM indicates "16" for the 350/300 engine and my original was stamped "20". Input from those responding was that both could be correct. I find now the original won't hold vacuum and will have to be replaced. I located an original control sealed in a red/white GM/Delco box marked with part # 1115357 and D1376 above it. Can the vacuum rating be determined from the D1376 without opening the box? Thanks...Clark

[Wayne M.]

Re: 1970 Vacuum Advance Control - Part # 1115357

Clark -- is the one you've located in a pull-string box ?

Here's the "357" I have; it also doesn't work (I can pull 20" Hg with a Mityvac, but it doesn't budge). It was on an early '66 BB distr. and confirmed correct # for that distr. by Delco Test Spec book. I have no catalog link to the Delco D1376 part #.

Don't know what the '70-72 TIM&JG states, but I have units with NO "MS" (on a 446_15); also no MS on a NOS 448_15 in a red/white/blue box D1378A; another NOS 164_20 with a bar (stamped) under just an "M" (not MS), in an orange/black/white box (someone wrote D1328 on it). Also have a 201_ 15 with a bar (stamped) above the MS. The latter is on a very original '68 L71 1111296.

So there's a lot of variety, probably based on when manufactured.

[Duke W.]

Re: 1970 Vacuum Advance Control - Part # 1115357

What do the CSM and AMA specs say are the vacuum advance specs for the base engine? The maximum advance is the two-digit number stamped on the bracket, so it should match these two sources. I would believe these two sources, especially if they agree before I would believe the JG.

If you don't want to pay a king's ransom, just buy a B22 - NAPA VC1802 or equivalent in another brand. They're all made by Standard Motor Products.

The VAC is worth a grand total of 3 points in Flight judging - 2 for originality, 1 for condition.

Duke

[Clark E.]

Re: 1970 Vacuum Advance Control - Part # 1115357

Thanks Wayne...We have exactly the same "MS" (on a 357_20). The unit appears to be in an original box. Are these units repairable?...Clark

[Wayne M.]

Re: 1970 Vacuum Advance Control - Part # 1115357

Thanks Wayne...We have exactly the same "MS" (on a 357_20). The unit appears to be in an original box. Are these units repairable?...Clark

Exactly what I forgot to ask (anyone in the know); what about soaking in a solvent ? Is the diaphragm and connecting internals all metal ?

[Duke W.]

Re: 1970 Vacuum Advance Control - Part # 1115357

I've never heard of anyone getting a seized VAC to work again, but that doesn't mean you can't. Pump it down, put it in a tank of mineral spirits, then pull off the pump down hose, which should allow the solvent to flood the interior.

The diaphragm is probably an elastomer, but it should be resistant to petroleum products.

A leaky VAC means the diaphragm is probably ruptured, but it could also be the crimp that secures the two pieces that make up the housing.

If someone has a seized VAC that they're willing to sacrifice to a destructive analysis, how about cutting it apart and taking photos of the interior, I've never done that, and don't have one I can sacrifice to science.

Duke