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Re: vacuum advance on 110hp...best practice?
Posted by: red monza ()
Date: September 27, 2022 08:41AM

PequotMonza64 Wrote:
-------------------------------------------------------
> red monza Wrote:
> -------------------------------------------------------
> > I believe that tells me also its already using the engines vacuum regardless where its connected and that it is perfectly fine to advance the timing with vacuum...agreed?
If all instructions say disconnect and PLUG the hose going to the distributor to set the static timing...that tells me vacuum is active in that hose, otherwise it would not instruct one to do what I just stated. I also said check you own hose and see if it is producing vacuum at ignition setting rpm and raising the rpm. Very basic.
>
> Not necessarily. How much vacuum and how much is needed to actuate the vacuum advance?
>
> >Static timing in a Corvair can be 4 to 24 degrees.
>
> That may be your experience, but that's not what's published in what I've read. My 110 with PG is 12 degrees. Maybe I've missed something. I have it set at 10 because a Corvair bud suggested it would be better on our available fuel.

Thank you Frank.
>
> > Anyway, the only ones that count is the static at about 20 ...
>
> I'm sure you have much more experience tuning the engines, and I may need to be schooled, but that makes absolutely no sense to me.
>
> Maybe later on I'll understand why what works for you seems to be so far from the norm. Maybe you forgot to mention you are not using factory standard parts in the standard configuration. In the meantime, I'll just assume that I'm still in the dark

Adding 2 degrees to the recommended static timing is "far from the norm". Really? I had the timing set at 14 on my first 110/PG 66 Corvair with 44,000 actual miles and it ran great. Why anyone would retard the timing on a 110 and make it less efficient is beyond me...no premium gas in your area as the 110 engine calls for premium.

I assume you have checked all the internal parts on your distributor, the correct weights and how far they move when fully engaged, the cam number, the shaft for play, the springs for correct diameter of the wire and height and length of course, you know...the science of the distributor. I would have the timing on 20 regardless of the distributor number which is not the orig to the 140 engine. It is a 319, a 110 distributor. I did look up the stats on the springs used in the distributor and put in weaker springs as the 339 dist called for vs the 319 stock springs.You should come and ride in my 140/PG and see if you find any problem in my "far from the norm" engine. I am serious, would be glad to do that.

The end of this con for me. Good luck. Hope you have learned from this as I have.



Edited 1 time(s). Last edit at 09/27/2022 08:44AM by red monza.

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Re: vacuum advance on 110hp...best practice?
Posted by: cnicol ()
Date: September 27, 2022 08:49AM

Pequot wrote:
I'm not sure I understand how there can be two (or more) schools of thought on this subject. It certainly would be helpful if people would restrict this discussion to Corvair engines and also to respect that the Turbo is its own beast. I think the original poster was asking about a bread and butter 110 hp engine.

Craig replies: There are two schools of thought regarding use of ported & manifold vacuum advance at idle because 1)Knowledge was evolving (toward ported) and 2) Camshaft design was moving toward higher performance through higher overlap. Higher overlap results in lower and sometimes unstable idle vacuum.
Unstable/low idle vacuum, due to camshaft design, led engineers to use ported vacuum (i.e.no vacuum at idle) and to "bake" that advance into base timing setting. This decision had everything to do with performance and driveability and absolutely nothing to do with smog or emissions.


Craig N. Coeur d'Alene ID.
66 Black Monza 4dr, 4.2L V8 49k
61 Seamist Jade Rampside 140 PG
65 Canadian Monza 4dr 110/PG 40k
66 Sprint Corsa convt - First car! Re-purchased 43 years later
2+2 gnatsuM 5691

+17 Tons of parts

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Re: vacuum advance on 110hp...best practice?
Posted by: Frank DuVal ()
Date: September 27, 2022 09:19AM

Thank you Craig!

As I pointed out, Chevy used ported vacuum back in the 40s. No way was emissions on their mind as the reason for using ported vacuum back then.

Frank DuVal

Fredericksburg, VA

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Re: vacuum advance on 110hp...best practice?
Posted by: PequotMonza64 ()
Date: September 27, 2022 09:48AM

red monza Wrote:
-------------------------------------------------------

> The end of this con for me. Good luck. Hope you have learned from this as I have.

I'm learning every day here, and I've gotten an education from you. As I said, you have MUCH more experience with tuning these critters and the Turbo is a different beast from what I have (and mine is the only Corvair engine I have ever touched). The problem here may just be one of communication where your are talking over my head and some of it is just flashing by. Sometimes you need to slow down a bit and use smaller bites of information with some guys like me.

This conversation has been valuable to me, and I appreciate your contribution.

Glen in Ohio
1964 Monza Sedan Powerglide 110 hp
Low mileage survivor, stock as delivered
Records back to 1967 in Pequot Lakes, Minnesota
Original dealer Mike Turk's in East Liverpool, Ohio
Located in Cleveland, Ohio area


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