vacuum advance control

[Leon Fogleman]

I have a 1965, 327/300hp Corvette. The vacuum advance control is stamped
238 24. Paragon and LI Corvette list a 236 16 vacuum advance control for this model and engine. Are they the same and just different numbers? As always thanks for any help given
Leon Fogleman

[Joe L.]

Re: vacuum advance control

Leonard------

No, they're not the same. The "238" refers to GM #1116238. This was the original vacuum contol used for your application. It produces a maximum of 24 crankshaft degrees of advance at full plunger deflection and that's what the "24" refers to. This vacuum contol was dicontinued in March, 1966 and replaced by GM #1115357. Unfortunately, the GM #1115357 was discontinued several years ago and is no longer available, either.

The "236" refers to GM #1116236. This control produces a maximum of 16 crankshaft degrees of advance. It's not the correct unit for your application, though.

[Duke W.]

Re: vacuum advance control

The first three numbers are the last three digits of the GM long part number. The last two digits are the maximum crankshaft advance.

If you check your '65 Corvette Shop Manual supplement, or the AMA specs that are in your free "Corvette Restoration Package" from GM you should find that the maximum vacuum advance for the '65 300 HP engine is 24@13", so this sounds like the OE can, but I can't verify the part number. This is considerably different than earlier 300 HP engines, which were closer to 16@16" This spec is achieved by the NAPA/Echlin VC680.

The "236 16" can is for SHP/FI engines and and its maximum advance is 16@8", so Paragon and LI are WRONG! Perhaps you could contact them and see that they correct their application information.

Duke