65 Vacuum advance can?
Can someone please provide me with a good part number for the vacuum advance unit for 65 300 hp 327 automatic trans.
Thanks,
Bruce B
Thanks,
Bruce B
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Re: 65 Vacuum advance can?
From the 10/72 parts manual it's 1115357. Also the same in the 1985 manual. Vacuum cans are engine specific but not transmission specific. It's the same no mater what trans is on your 1965 327/300.
Tom -
Re: 65 Vacuum advance can?
For meeting the 2 inch rule Napa VC 1765. Fully deployed 11-12 inches HgComment
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Re: 65 Vacuum advance can?
Jim------
The GM #1116238 was discontinued in March, 1966 and replaced by the GM #1115357. Both have about the same specs. The 1115357 was used for many base engine applications. It's miserable unless one likes detonation.In Appreciation of John HinckleyComment
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Re: 65 Vacuum advance can?
Joe,
The new engine in my 65 is actually a 327, with 9.5:1 pistons and the 151 (327 350 HP cam) and stock small valve double hump heads.
Just a mild engine, and the car is driven a lot.
Would you please recommend a appropriate vacuum advance can?
Thanks,
Bruce BComment
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Re: 65 Vacuum advance can?
Bruce
Check your e-mailComment
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Re: 65 Vacuum advance can?
L-79 cam typical idle behavior with a manual transmission is 14-15" @ 750 IN NEUTRAL so the 12" B26 (NAPA VC-1765) passes the Two-Inch Rule.
HOWEVER, you say that you still have the OE Powerglide? If true then you need to measure idle vacuum idling in DRIVE. Please post that answer "vacuum @ idle speed" per the above example IN DRIVE. I've been looking for this information for a LOOOOOONG time and would appreciate your help.
Depending on results, you may need to install the more aggressive 8" B28 VAC.
Also, PLEASE POST the data stamped on the currently installed VAC mounting bracket.
DukeComment
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Re: 65 Vacuum advance can?
Duke,
The 65 currently has a modified GM Turbo 350 trans in it.
I will do the measurements as suggested and post the results.
Thanks,
Bruce B.Comment
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Re: 65 Vacuum advance can?
Duke
Per your request in post #8 ... here's data from my car.
Stock, rebuilt '66 300HP with stock, rebuilt p/glide, OEM distributor w/Lars rebuild & curve, Lars VAC installed, B26 can, NOS Holley 3367 set-up by Lars; 7500 MSL
13.5 to 14" Hg in neutral, 710 rpm. 12 to 12.5" Hg in drive. rpm drops to a stable 540. Runs great, no difficulties although 2" rule barely squeaks in.
JeffComment
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Re: 65 Vacuum advance can?
I was about to question that it only pulls 14" at 710 in neutral, assuming an OE equivalent 300 HP cam, but then I noticed your altitude. If you have any idle instability issues a 8" B28 should help and allow a slightly lower idle speed in Drive.
Thanks for posting the data, but your high altitude is a relatively rare case. Idle vacuum drops off with increasing altitude and you're really up there.
What I need is a for sure 300 HP cam engine and any torque converter transmission(with typical OE 1800-2000 stall speed) manifold vacuum idling in drive at about 450-500 at no more than about 1500 feet above MSL.
DukeComment
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Re: 65 Vacuum advance can?
Duke, this is what I've got on mine.
1966 327/300HP Power Glide
Air Temp 87 degrees, Barometric Pressure 29.92, Altitude 476 feet ASL,
VAC ADV B-26, Timed 10 degrees BTDC
In Neutral, 19.5 Hg, RPM 725
In Drive 17.5 Hg, RPM 525
I have tried to use a B-28 VAC on two occasions and it severely fouled the spark plugs both times. But, I'm no mechanic.
Hope this helps your quest.
Ken BryantComment
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Re: 65 Vacuum advance can?
If drive-ability is more desired over originality Id recommend installing an adjustable travel(not adjustable rate) vac can. This allows for "super tuning". Now you get to zero in all ignition timing events. Base timing. Base timing with specific vac timing applied. Then custom tune the mechanical advance. And of course your adjusting the A/F mix with each change. Give the engine as much advance as it will tolerate short of pre-ignition.
With today's fuel yesterdays timing specifications can be improved upon(same for carb specs). After you get this all dialed in according to your driving habit, fuel octane rating (non ethanol) and general elevation above sea level, the car will respond favorable with much better, smoother throttle response and no detonation.Comment
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Re: 65 Vacuum advance can?
Thanks for the detailed report.
I know that with a manual trans and no AC a base cam engine with a manual trans should idle in neutral at about 18-19" at 500. But with an automatic, idle vacuum must be checked in Drive, and at the same idle speed (500) manifold vacuum will be less due to the converter load.
So it looks like the 15" B22 is okay for both manuals and autos EXCEPT, maybe, C-60 and high altitude. In either case idle vacuum must be recorded with the compressor engaged and it will be lower for both manuals and autos because of the additional compressor load. Then apply the Two-Inch Rule and use the least aggressive of the available 8, 12, and 15" VACs that meets The Rule.
Maybe that's why GM chose to install a 12" VAC on '66-'67 300 HP engine because it was okay (Two-Inch Rule) for the worst case, which would be idling in Drive with an auto trans and the AC compressor engaged.
DukeComment
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Re: 65 Vacuum advance can?
The trouble with these so-called "adjustable" VACs is that they don't allow independent changes of both vacuum and advance. The adjustment changes both simultaneously in a fixed way and rarely ends up optimized for the engine configuration.
There are only three applicable VACs for all pre-emission and ported vacuum advance emission controlled engines and one of these ten-buck parts will be very close to optimum if the tuner understands and follows the Two-Inch-Rule.
Optimum spark advance maps for just about all OE engine/drivetrain combinations are well established guidelines for all are in my 2012 San Diego National Convention Tuning Seminar, which is an easy Web search.
DukeComment
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