Tapping for ported vacuum on Stromberg 97's

Has anybody successfully added ported vacuum to a set of 97's. If so where exactly did you drill and tap and what vacuum did you actually record after adding the port. Did you get a proper vacuum signal.

I have a few sets of 97 bases that I could drill out and since it will take at least a few weeks for my distributor to be converted to full mechanical by Bubba after he gets it I was thinking of trying this on the spare bases that I own with a backup distributor.

I like the a adjustable vacuum advance over pure mechanical on some of my cars so that I can tweak things after modification plus I want to understand how to do it.

 

I've never done this...IMHO engines generally prefer manifold vac. Having a vac advance to supplement the mechanical is a very good thing for power in normal driving situations.
The Stromberg already has some holes ready to use or convert...look at the rear of the base. The little nubbins back there are plugs in the ports used at the factory to drill idle holes. Remove one and you are looking at ported vac, drilled in a bit above throttle plate. I think easiest way to use it would be to just drill it to fit a small tube, stopping the oversize drill before it goes all the way to create a step.
This would give ported vac just as supplied on many '70's applications.
If you are thinking about this as a control for original '49-53 distributor, though, you are barking up the wrong tree in the wrong forest.

 

Thanks Bruce figured you might drop in.

Its a 312 Y block motor, with a normal rotation vacuum advance. Its a cruiser so partial throttle position and idle are were am focusing most of my time in terms of tuning. I don;t even bother with my flatheads doing anything but full mechanical.

I guess I was wondering if I would get a true vacuum signal tapping the base like that. If it would be close enough to the ****erflies to give a true reading.


this would totally not work with a load-o-matic. (In case of search)

 

I think it would be about where the ported vac line went in on a typical Holley or such.
But...stock Y blocks up through 1956 (I think) had no centrifugal advance. Later ones did.
If this is an early Y block distributor...the vac can is the whole deal, and requires a venturi port linked to a ported vac port. If hooked up to ported only it might well function at half throttle and down but will for sure drop dead when pushed a bit. If this is an early distrib of that type, Holley Loadamatic, converting to a later one is a more productive hop-up than multiple carbs! Someone who knows will likely chime in with years of good distributor for the Y.

 

If that is the case a manufactured stock unit is only ~70$ locally for the later motor. I want to say that my motor is a 59 unit so it should have the centrifugally advance in it. I need to pull it apart tonight and take a look at it. I could not get it out without removing the intake due to firewall clearance issues.

I am fixing somebody else's stupidity on this one. Figures I would spend a bunch of cash to get a rust free shell and the motor and transmission which I saw as just extra are all mucked up.

If anybody knows of a stock centrifugal only unit that bolts in please speak up. Mallory makes a electronic one but not really happy with there stuff in the past.

 

Just grab the rotor and give it a twist in the direction of rotation...'59 would be centrifugal if stock, and rotor should twist circa 10 degrees or so and then snap back home. The dreaded Loadamatic was gone by then, but its shaft was entirely solid and rotor should noy mave beyonf the slop in the gears. If you can read the ID plate I think number would start with something like B7...any number higher than 6 in there should be centifugal!

 

Bruce did a bit of digging.

The 64 F100 292 cid Distributor fits the 312 Y Block and has provisions to run on manifold or ported vacuum.

I also fabbed up some tapped/stepped br*** tubing at the office to port my bases this evening.

 

OK! A real distributor and you are on your way. Check what you have, though...if post- 1956 it may well be about the same thing.

 

Bruce I owe you a beer, seriously when ever you get out to California a few bottles of home brew on me. Looks like its a 58+ with a standard vacuum advance.

Pulled the distributor got it un-gummed up, 10 degrees of counter clockwise, vacuum advance on the distributor even works. Both bolts the wrong size and loose holding it in place which is how it worked loose. Held vacuum for 2 minutes which is good enough for me to call the advance good.

Back in and indexed I think. Decided to wait on drilling out the 97 bases until I get the rebuild kits in tomorrow, if I could use manifold vacuum that would be so much easier but more then worth the effort to get it all hocked up right the first time.

 

Why dont you just install the vacuum adapter for a Southwind heater between the carb base and the intake manifold and route the vacuum advance to that?

 

This will pull from both ports, so it should give a more even vacuum.

 

Those sit under the ****erfly as as such would give you intake vacuum not ported vacuum.

 

Not necessarily, If the vacuum port was off the body of the intake you would have intake vacuum, if the port was close to the ****erfly then you have the throttle vacuum which is what you get with the spacer.

 

If so that would solve a ton of problems. I could cast/machine a quick 1/4 inch spacer with the port already attached.

Though I do not think the vacuum signal will be exactly the same, easy enough to check with my gauge but I think you would have a bit of vacuum at idle.

 

Vac from below throttle plates will be manifold vacuum, vac from above plates will be ported. Ported vac is isolated from manifold vac until throttles open. Manifold vac is full time.
If manifold vac is needed a plate will do it, but there are very few manifolds that don't already have a plugged hole somewhere for manifold vac.

 

hard to find but Stromberg made bases with a tapped vacuum port.

 

But that's just a manifold vac source...doesn't the OP want ported?? That space is there on all or most, easy to drill and tap for use, but most manifolds have available ports anyhow.
That one, drilled blind and then opened into both sides of carb with very small drills might be an easy way to provide for a PCV installation.

 

Those are actually 1-1 bases for factory idle adjustment screws I believe. Very Rare.

 

Not the idle screw holes...the big hole in one, empty boss on the normal one

 

Yeah but on that casting the port would be below the ****erflies.

 

Yes...that would be manifold vac

 

No, this is ported vacuum. here is a better picture see the plug just above the tapped vacuum hole? it lines up above the throttle shaft / ****erfly on the inside. I can supply a picture of the inside if needed.

 

So...threaded hole does not go through, it intersects a drilling up to the cast boss that has a drill access plugged for a hole above plates...is that right? I did NOT notice the boss headed up when I first saw that!
Loadamatic required a more elaborate mod...it needed joint access to ported vac and to the venturi pressure drop as well. That version had special main body to suit I think.
Very rare, because Strombergs were selling mainly to rodders by the '50's and everyone had figured out that a different distributor was the first and best mod, and a necessary precursor to running lots of Strombergs.

 

So got everything put back together. Rebuild the carbs, set the idle to factory spec. Not a lick of vacuum at the port I drilled until the prms get above 2400 so I still have a m***ive stumble off idle. Once it gets over that though it runs very well. Vac gauge reads correct on the intake port so at least its not the gauge.

I have the usual high idle speed issue when running triples but chances are the carb return spring is not as strong as it should be or one of them is out of sync on the linkage. Using my hand to pull back the idle drops to ~650 or so which with the mild cam is about right.

Motor for the first time sounds decent.

 

Been following your thread, trips on a y block stumble, I am of the opinion that you need to richen the jets up numbers 97 usually have 45s so you need to go to 48s. The increase in carbs gives you an increase in air so the mixture must be richened to compensate for the in rush of air as the throttles are cracked. Another tip is to shorten the throw of the accelerator pump arm to give a larger shot of fuel when you hit the pedal.

 

I got a box of jets and at least 6 or so of them in that size. Will give it a go tonight.

I also noticed that I have everything on the winter accelerator pump settings and in the back of my musty mind I seem to remember that you need to have them set at summer to set the idle correctly.

 

Drilled out all three bases, then got a br*** Tee to get it all together finally got some vacuum singnal. Added a bit larger jet and no more hesitation. The thing just ROARS now.

Of course at some point during this I ended up killing the temp sensor so no driving it until I can figure that out. With the new radiator I am not sure how warm the this is actually getting.

 

If you can find a mid-30's Buick or Oldsmobile Stromberg carb, they also use an EE-1 base casting but have the vacuum porting already in them. The throttle shaft is different and would have to be changed out, but other than that, they are the same as the Ford casting. I used to have several of them in years past, but they're all gone now.