Vacuum advance or not ?

elwood

elwood

Well-known member
So I put a couple Stromburgs on one of my 8bA,s and there's no vacuum port on the carb bases to run to the distributor, so I was asking my old friend, whos been running flatheads since the 50s, what type distributor I needed to run, something I'm thinking, with a mechanical advance instead of a vacuum advance,
He told me he never runs the vacuum advances, he said that the weights in the stock distributor would act as a mechanical, he said he has a couple running now set up like that,
I think he told me he puts weaker springs in them,
Said he pulls the vacuum canister off and runs them.
So basically I'm looking for the best way to set up the distributors.
Iv got 4 running flatheads and they all seam to have different set-ups.
 
elwood said:
He told me he never runs the vacuum advances, he said that the weights in the stock distributor would act as a mechanical, he said he has a couple running now set up like that,
Click to expand...
That's a neat trick since there are no weights in the stock Loadamatic distributor.
 
Hey Elwood, your friend don't know what he's talking about. The stock 8BA dist doesn't have any mecanacal weights or spring, it only has the vaccum can. It's pretty hard to run an 8BA with Stromg carbs. You will be better off running the Chevy dist. Walt
 
thanks for the replies guys, yea your right, the stock 8ba diss, don't have weights, just the advance cam. guess I need to ask him what he's got going on.. I prouble misunderstood him.
Walt, iv gotten another block, and a speedway block water passage tester, but am busy in my shop with customers cars and haven't gotten back to my F1.
Hey, on the eab in my F1, I'm running 2 ford script 8ba carbs with one blocked off and the other vacuum port running the diss.
That ort to be good ?
Thanks again guys..
 
Hello Elwood,
The opinions expressed here are my own.......so !
In my experience the SBC dist is as good as it gets, for a Flathead....,
with the can. Here's why...The can pulls the advance plate ahead when engine vac
increases like when the motor is powering the car down the freeway and not 'working'
real hard. These extra degrees of advance add mpg's and a cooler running motor....
it's a fact. When you wish to blow the doors off some buddy up ahead on the freeway
and you floor it the vac drops and the plate retards to a manageable point so
detonation does not occur.
We've all seen Loadmaster distributors igniting happily running
Flatheads of all configurations but what's not seen is the loss of potential power,
tunability and mpg. All this at a reasonable price....6 or 12 volts and zero point
float to at least 5500 rpm.
I shall now step down from my orange crate.
Charlie ny
 
Charly has it right on the money. The reason is obvious, your engine needs one form of advanve to make power and one to give economy. Those running no vacuum advance have poor combudtion in cruise where you have a lean mixture and that needs more advance. Over the years this causes advanced ring ware with excess gas washing the cylinder walls. It also removes mor money from your pocket.
Tuning now has advanced to using some modern ways to inprove our old Flatheads, take advantage of an AF meter and experiment with timing. Not every engine is the same.
 
Charlie ny said:
Hello Elwood,
The opinions expressed here are my own.......so !
In my experience the SBC dist is as good as it gets, for a Flathead....,
with the can. Here's why...The can pulls the advance plate ahead when engine vac
increases like when the motor is powering the car down the freeway and not 'working'
real hard. These extra degrees of advance add mpg's and a cooler running motor....
it's a fact. When you wish to blow the doors off some buddy up ahead on the freeway
and you floor it the vac drops and the plate retards to a manageable point so
detonation does not occur.
We've all seen Loadmaster distributors igniting happily running
Flatheads of all configurations but what's not seen is the loss of potential power,
tunability and mpg. All this at a reasonable price....6 or 12 volts and zero point
float to at least 5500 rpm.
I shall now step down from my orange crate.
Charlie ny
Click to expand...


Yep !!
 
Ok, now what do us do that have the SBC distributor without the vacuum can? I run one on my 51 Merc that I received from Bubba and it was recommended to me not to have the vacuum advance, now it is suppossed to be better with one??
 
The final development of distributors before they were superseded by ECU controlled spark and fuel injection was just as has been suggested above, centrifugal advance coupled with vacuum advance for part load economy. There is really no discussion to be had. I would love to see how a Flathead would do with full engine management and standard heads, flow etc, just to see how much modern electronic control does for an otherwise stock motor.
 
alanwoodieman said:
Ok, now what do us do that have the SBC distributor without the vacuum can? I run one on my 51 Merc that I received from Bubba and it was recommended to me not to have the vacuum advance, now it is suppossed to be better with one??
Click to expand...

I guess i thought we had beat this horse to death but not really.....

Any gasoline engine can benifit from the use of both mechanical advance ( controlled by engine rpm) and vacuum advance ( controlled by engine load).
Especially a emission equipped engine, the mechanical advance overlaps and works in conjunction with the vacuum advance to provide a spec level of advance during all operating conditions.
For an example lets say the distributor has 15 degrees of mechanical at 2500 rpm and 15 degrees of vacuum advance at 18 inchs of vac. That could be a advance of 20 degrees (30 total with overlap) during all operation conditions. The engine wouldnt have 18 inches of vacuum at 2500 rpm hense the overlap etc...., ie rpm high vacuum is low and vac is high rpm is low....
Another problem is the use of a high lift large overlap cam shaft with multiple carbs making the vacuum very hard to tune.
All of our distributors can use the vacuum unit, it just needs to be added but most dont have the ole Ron and Richard patience to mess with the engine and tune it all in...
The vacuum unit is pretty hard to tune on thee engines and may even cause a clearance problem as well...
We ship approx 3-4 % of our units with the vacuum canister... 96 % dont have them and use a really good curve with just mechanical weights and springs....
 
ajmac said:
The final development of distributors before they were superseded by ECU controlled spark and fuel injection was just as has been suggested above, centrifugal advance coupled with vacuum advance for part load economy. There is really no discussion to be had. I would love to see how a Flathead would do with full engine management and standard heads, flow etc, just to see how much modern electronic control does for an otherwise stock motor.
Click to expand...


Interesting thought...
I happen to own Linder Fuel Injection and have trained quite a few techs in the later technology over the years etc.
One of the factual issues concerning gasoline engines and engine design is that a given engine takes xxx amounts of air fuel and develops xxxx amount of btu,s of energy etc.
A good example is the addition of fuel injection to a older engine ( lets use a boat engine for one example). The addition of fuel injection to a boat engine didnt add any fuel economy or additional hp at all.
It did change the driveability of the engine and allow us to pop a skier out of the water at a different engine rpm ( change in torque curve)..
 
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