Technical Vacuum or no Vacuum ?

I recall Bubba years back on the FordBarn saying something like 18*s BTDC ? For a FH V8. I don’t recall his view (if any) on vacuum advance for highway driving on a FH V8.
When I used to frequent the FB some were doing tests on various setups for performance vs mileage, but not sure the outcome.
Again, I’m just talking about Ford FH’s.

 

That brings back some memories Andy!

My Dad was a truck mechanic for a GMC dealership in Cleveland, Ohio from 59 to mid 80's (basically all the years I was a kid) The way GM did things back then, anything replace under warranty was throw away. I learned engine building on small blocks & big blocks that were slated for the dumpster, but ended up at home. I still have probably 10 or so 4 bolt main small blocks upstairs & several big blocks as well. Including a 366 that had 6 miles on it with a knock...Turned out it was a fuel pump pushrod, so basically I have a new long deck engine that is brand new! Of course back then, my idea was just using the tall-deck block for a big inch stroker, but nowadays you can buy a really big inch engine for less that what I could build one for, so it is just a boat anchor now!

God bless
Bill
https://www.jalopyjournal.com/forum...ar-transport-hauling-open-or-enclosed.614419/

 

Yeah, from an engineering standpoint any gasoline motor runs best, i.e. the most power & efficiency, with the ignition advance held to a point just short of engine knock at all times under all conditions. This is a really tall order on a street engine, which run varying speeds, loads, and RPM.

The problem they ran into early on, there was no way to achieve the correct ignition curve using mechanical weights and springs alone. OHV engines routinely run 50 to 55 degrees ignition advance on the highway. But that's why vacuum advance was invented. It doesn't "improve" fuel mileage, though efficiency takes a 15% or 20% hit on the highway without it. Modern engines have all this computer-controlled electronically with sensors and gee-gaws. Vacuum advance was an ingenious solution to this problem, and manifold vacuum is still used as a signal input.

Efficiency and/or power always declines anytime the ignition advance deviates from the optimum point. Federal emission regulations threw a wrench into the mix at the time they were enacted, and further confused a new generation.

 

I agree with most of your post, with the exception of the vacuum doesn’t improve fuel mileage! I truly believe it does! We may be just talking the cup half full or half empty. LOL!

But timing is very important, like mentioned, it need to be advanced as much as possible up to ….too much! You touched on the new computer controlled cars, that is one of the major reasons they usually get better fuel mileage and a lot of horsepower out of a small engine. Precise timing helps do this! Quick and Precise timing cannot be accomplished with weights and vacuum. But speed and engine load are still the two main inputs to the computer to determine timing. There are several other inputs that help determine optimum timing!

But with either old or new engines….timing is very important!






Bones

 

I have been Running a Dual Point Tack Drive ( needle Bearing ) GM for
about 45 Years & No Problem it comes with 12 degrees in the Dist.
and the rest of the Timing on the Damper,
And I never had a Problem with it.
I bough my Dist. in 68 & It was 185.Dollars,
I do not know if they Still make Them, but a lot of Vets Had them.

Just my 3.5 Cents

Live Learn & Die a Fool

 

Yes - trying to get you to understand the error of your ways!! lol

It's like saying properly inflated tires "improves" gas mileage. Well, not really - Under-inflated tires increases rolling resistance and robs power. It's less than what it should be. Retarded (or also as you note over advanced ignition timing robs power and efficiency.

 

Do the vacuum advance.... your motor will love you for it...

 

This is a late flathead V8. FoMoCo used a unique Vacuum only advance that was metered through a special "matched" carburetor. The distributor and carburetor were matched pairs. This advance system is unique to the late flathead, Y blocks to 1957 and small 6cylinders to the 1970s. It's called Loadomatic.
Do not confuse this system with a "standard" vacuum/mechanical advance. The vacuum was metered through Loadomatic compatible carburetors.

Again...If you use a stock vacuum advance only distributor aka..Loadomatic or LOM, you must use the matched LOM carburetor.

The stock LOM distributor....
Will work fine with the stock LOM carburetor
Might work OK with 2, LOM carburetors with custom work done to the LOM carburetors (split signal) and custom work done to the LOM distributor (tuning the vacuum only advance springs)...
Will not work the triple carburetors of any type
Will not work with an early Stromberg
Will not work with any non LOM carburetor 2bbl 4bbl no matter...it has to be LOM compatible to use the stock distributor.

Do not confuse all this debate about mechanical vs vacuum mechanical advance distributors. These guys are talking about later model engines and not "late" flatheads with the L-O-M system.
The reason late flatheads have aftermarket mechanical only advance units put on them is to get away from this LOM system. Why?, because without a LOM carburetor or 2 modified LOM carburetors the engine has no working advance with the stock distributor...

 

This is a good explanation of the Ford/ Mercury stock equipment and their proper use. I found that upon repairing/ replacing my Load a matic on my 8ba and rebuilding the correct 94 carb. , it performed very well and I was actually surprised how well.
To the use of the Bubba's unit, you should be able to just add the vacuum advance diaphragm to the dist you have and check the mech advance is limited to about 22-24 degrees total. The vacuum advance units for Delco distributors available now are adjustable; you can set how much you need.
JMHO.
EDIT: you may need to tap into manifold vacuum with the Delco dist. with vac.