70 LT-1 vacuum advance

[Mathew S.]

[Joe L.]

Re: 70 LT-1 vacuum advance

At the Texas regional I found out the vacuum advance is incorrect, and would like to get the right one. I don’t have my current judging manual handy, and the internet is suspect. I have one of the older green ones, and it called out a 201 16. Anyone able to shed some light on what is correct, and maybe the actual GM part number.

Mathew------

What is your distributor part number (from the metal ID band)? If it is 1111491 then the original vacuum control was GM #1116201, stamped 201-15

[James G.]

Re: 70 LT-1 vacuum advance

I don't know which can is in the car, however most of the time the original 201-15 will dither in and out because of the cam and lack of vacuum.
Many LT1's have the L76/L84 can which is all in well below 10", in turn making the engine idle much better.

[Duke W.]

Re: 70 LT-1 vacuum advance

'70 LT-1 OE vacuum advance is ported, so the Two-Inch Rule doesn't really apply. Better engine operation can be had by converting to full time vacuum advance but you need a Modern B28 VAC, which is equivalent to the OE 236 16 VACs used on the 327-365/375 HP engines. If the engine has TCS that will likely have to be disabled to achieve full time vacuum advance.

The VAC is only worth 3 points, 2 for originality and 1 for condition.

What is the ID number of the installed VAC and what was the deduction for the "incorrect" VAC?

BTW, the 201 15 was replaced in service parts in the late sixties even though it was used in production into the early seventies. Go figure!

So your only hope is to find a used, serviceable example that will likely be a tough find.

Duke