312 Y block distributor points question

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Mar 18, 2015 | 11:24 AM

#16

ALBUQ F-1

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From: NM

Quote:

Originally Posted by 38 coupe

Do not hook the vacuum advance to manifold vacuum. Hook it to the ported vacuum on the carburetor. The only distributors I am aware of designed to get straight manifold vacuum are the 32-48 flathead distributors with a vacuum brake.

Quote:

Originally Posted by hiball3985

Agreed, never use manifold vacuum, use ported from the carb.

Here is a very good description of which to use:
Timing Mech vs Vac advance Good Read - El Camino Central Forum : Chevrolet El Camino Forums

Mar 18, 2015 | 04:36 PM

#17

hiball3985

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From: tujunga, calif

Quote:

Originally Posted by ALBUQ F-1

Here is a very good description of which to use:
Timing Mech vs Vac advance Good Read - El Camino Central Forum : Chevrolet El Camino Forums

I read that article last year and in theory it sounded good and made sense. I ran my 292 using the manifold vacuum for about two months but my seat of the pants dyno didn't show any improvements that I could notice. Temps at idle remained the same, mpgs didn't change and I noticed no improvement in performance.

Mar 18, 2015 | 05:31 PM

#18

ALBUQ F-1

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From: NM

Quote:

Originally Posted by hiball3985

Which distributor were you using? If it was a L-o-M it would run really poorly, I'd guess. Regardless, the vacuum can on your distributor has to be designed for specific advance at specific vacuum. I'm using an Accel adjustable vacuum can, limiting it to 8 deg of vac advance. I'm going to try going to 10 deg, at my altitude you can get away with a couple degrees more. The biggest impacts will be at cruise, better mpg, but if your carb is running fat, you might not notice.

Mar 18, 2015 | 06:11 PM

#19

hiball3985

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From: tujunga, calif

Quote:

Originally Posted by ALBUQ F-1

I'm using a 1962 centrifugal advance type because it only has 24 degrees advance.
10 initial + 24 centrifugal = 34 total, I don't like to push it beyond that with Calif crap fuel.
I have an adjustable vacuum canister set at 10 degrees. I'm using a 390 cfm Holley 4V jetted fairly lean..

Mar 18, 2015 | 06:37 PM

#20

ALBUQ F-1

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From: NM

I don't know how much advance Y-blocks need, that's quite a bit more than flatheads like. I'm running 3 + 18, all in by 2,000 RPM (engine). What kind of mileage are you getting? I'd love to have a 57 Ranchero!

Mar 18, 2015 | 06:53 PM

#21

hiball3985

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From: tujunga, calif

Quote:

Originally Posted by ALBUQ F-1

First I'd like to say, using the manifold vacuum method my be different for different people, just to many variables, weights, gear ratios, engine condition etc etc etc.. People say Y blocks can take 36-38 degrees but I just don't push it that high..

The 57 has a 292 with G heads, Isky E4 cam ( very mild ) 390 Holley, everything else is stock. I have 3.70 rear gears and a T85 Overdrive. The longest trips have been to visit the grand kids, 280 miles round trip. Two times using manifold and two times using ported and each time I got 18 MPG.. I try to keep it at 65-70 mph but sometimes push it faster to keep from getting run over by the idiots..