Correct vacuum canister for engine using the LT-1

[Michael G.]

Good evening all,

Am looking to get the skinny as the title suggests which or what is the correct vacuum canister using a LT-1 cam with my 327. Thanks

[Duke W.]

Re: Correct vacuum canister for engine using the LT-1

8" B28. Be sure it's connected to a full time manifold vacuum source.

Duke

[Mike E.]

Re: Correct vacuum canister for engine using the LT-1

Good evening all,

Am looking to get the skinny as the title suggests which or what is the correct vacuum canister using a LT-1 cam with my 327. Thanks

Michael,
Good question, one I'm going to need the answer to myself. Duke always talks about the "Two Inch Rule". From what I understand is you measure the manifold vacuum at the recommend idle speed, then size the can to be 2" below that measurement.

See this thread:

https://www.forums.ncrs.org/showthread.php?97360-L-79-distributor-blueprint-overhaul&p=641926#post641926

If I'm wrong perhaps Duke will chime in.


Mike

[Michael G.]

Re: Correct vacuum canister for engine using the LT-1

8" B28. Be sure it's connected to a full time manifold vacuum source.

Duke

Duke,

Have a brand and model #? Possibly where I might buy one?

[Duke W.]

Re: Correct vacuum canister for engine using the LT-1

All currently available VACs are manufactured by Standard Motor Products, but are in available in a half a dozen "brands". They are all the same SMP part.

The B28 appears to be out of production, but there is still stock in some brands. There have been recent threads on the subject.

Duke

[Duke W.]

Re: Correct vacuum canister for engine using the LT-1

Michael,
Good question, one I'm going to need the answer to myself. Duke always talks about the "Two Inch Rule". From what I understand is you measure the manifold vacuum at the recommend idle speed, then size the can to be 2" below that measurement.

See this thread:

https://www.forums.ncrs.org/showthread.php?97360-L-79-distributor-blueprint-overhaul&p=641926#post641926

If I'm wrong perhaps Duke will chime in.


Mike

Basically correct on the Two-Inch Rule. The LT-1 cam generates about 12" idling in neutral at 900, so a 10" VAC meets the Two Inch Rule, but available VACs are 8" (B28), 12" (B26), and 15" B(22). All provide a maximum of 16 deg. crank advance.

Since a 10" is not available, the 8" is the best fit that meets the Two-Inch Rule.

One of the above VACs is the "best fit" for every OE engine with single point or TI ignition with full time vacuum advance or converted to full time from OE ported. It's just a matter of measuring idle vacuum (in Neutral for manuals and Drive for autos) and applying the Two-Inch Rule.

Since typical idle characteristics are known for most OE engine/transmission applications, I've listed starting recommendations in the past on the TDB, and you can also find them here:

http://www.stlouisncrs.org/news_files/DukeWilliamsEngineTuningPerformance&EconomySeminar.pdf

Duke