Bubba's chevy conversion dist.
 

I have a Bubba's chevy dist for my 51.I had vac advance added to the dist.What should the static advance be? I believe that the vac adv. must be from the manifold not the carb port as with the loadamatic,right?Phil

Re: Bubba's chevy conversion dist.
 

Did you ask this question when you bought the distributor from Bubba? Seems like he should be the one to answer the question.

Re: Bubba's chevy conversion dist.
 

The vac comes from ithe intake, not the carb. Disconnect the vac and plug it. Bring the rpm up to 2000 RPM set timing to 20 degs. re connect the vac read timing, should be 26-28. Let engine idle, remove vac plug it, read advance should be 2-4. Add vac should be 10-12. Now drive the car,it should start easy and idle nice and give great mileage. You can adjust the vac and turn the dist to make minor adjustments. If dist has more than 20 degs mach send it back to bubba.

Re: Bubba's chevy conversion dist.
 

Our latest conversions are shipped with 16 degrees (engine) of mechanical advance ( may be adjusted up or down with allen screw). The vacuum cans as supplied usually are 10-12 degrees of additional advance with full manifold vacuum applied and may also have the rate adjusted as to when that may happen.
Assuming the engine timing is set on the mark at 2-4 degrees btdc ( idle with no vacuum on vac advance) The engine when reved up ( 2500) would add another 16 degrees at 2500 rpm. This is with no vacuum.
Now lets add the vac unit to the deal with manifold vacuum applied. The engine would start with the 2-4 intial set on the pointer and when the engine starts the vac will add the 10-12 degrees giving the engine approx 16 degrees . (at idle) Now lets rev up the engine , when the engine is reved up the vacuum will drop and the mechanical advance witll increase . ( you wont have max vacuum with 2500 rpm or engine load).
This will allow the vac and mechanical advance to over lap each other to maintain a constant 16 degrees all the time the engine is running.
Both can be tuned to make this overlap perfect. Richard in Fla has mastered this adjustment with many trial and error drive sessions etc....

Clear as mud right ??? :>)

Re: Bubba's chevy conversion dist.
 

Jim, this setup would give 30-32 degs in cruise, alittle much, don't ya think?

Re: Bubba's chevy conversion dist.
 

The numbers i used were just for explanation , the vac cans vary from 6 to 10 degrees typically and must be adjusted ( we use the adjustable accel units) .

We now use Richards adjustable set up on the cam and adjust all to 16 degrees engine .

Hopefully everyone understands the vac must be adjusted.....

Yep 30-32 degrees at cruise would be a bunch for the flathead.... good catch...

Re: Bubba's chevy conversion dist.
 

Thanks ,will install it tom.Dumb ? how do you adj. vac adv. ?Phil

Re: Bubba's chevy conversion dist.
 

You should have received a small allen wrench with your distributor. If you insert the long end down inside the vacuum canister's snout (where the vacuum hose goes) it'll engage the adjusting mechanism.

To adjust the vacuum advance without a distributor machine and a vacuum pump/gauge you will need a timing light and a degree strip on your crank pulley.

Once the engine is warmed up, remove the two little springs you'll find under the rotor. This will allow your mechanical advance to go to maximum and stay there. This makes your job easier.

Now start the engine and let it run at idle.

With the vacuum hose disconnected from the canister, make a note of the advance setting. I'll use 20 degrees BTDC. (It could be anything)

Now connect the vacuum hose and read the advance again. The idea is to adjust the canister so it adds 8 degrees of advance (that's the number we like).

If the advance reading is higher than 28 degrees (20+8) remove the hose, insert the allen wrench, and turn it counterclockwise a couple of turns. Now check the combine advance again to see where you are.

If the advance reading is lower than 28 degrees (20+8) turn the allen wrench clockwise a couple of turns and check again.

Once you arrive at the amount of vacuum advance you're after, remove the hose again.

Since your distributor is already at full mechanical advance, this is a good time to also set the maximum mechanical advance your engine will see. Loosen the holddown and rotate the distributor body until you see 20 degrees on the degree strip. Then lock it back down.

Now when you reconnect the vacuum canister you should see 28 degrees +/-.

Now put the springs back in and go for a ride.

The vacuum advance will come into effect ONLY when the manifold vacuum is high as at idle or easy steady cruise. The instant you hit the throttle for some power the vacuum drops out.

Hope this helps.

Re: Bubba's chevy conversion dist.
 

Thanks Richard and Ron.....................

Re: Bubba's chevy conversion dist.
 

Thanks got the allen wrench,thought it was for the points.Phil

Re: Bubba's chevy conversion dist.
 

Where do I get a degree strip? Phil

Re: Bubba's chevy conversion dist.
 

richard makes them:)

Re: Bubba's chevy conversion dist.
 

If you get a digital timing light, you don't need a degree strip.

Re: Bubba's chevy conversion dist.
 

Is your engine otherwise stock?

If you can determine the diameter of your crank pulley, I'll e-mail you a PDF you can print out at 100% and it'll give you a pretty darn accurate degree strip. It's what I use; created it with my computer.

It looks like this.

Re: Bubba's chevy conversion dist.
 

Richard,Great idea,I will PM the dim.

Re: Bubba's chevy conversion dist.
 

Still in thy stone age,but have a battery opperated timing light.

Re: Bubba's chevy conversion dist.
 

Now that we have that cleared up, we can take advantage of the vacuum advance, by leaning the main jets. A lean mixture requires a longer advance. When you get into the throttle the PV will richen the mixture, the timing will fall back and you'll have all the power you need, Richard uses an AF meter that shows fuel ratios of 15.5 to 16:1 in cruise and the mileage of 20Plus in a hat 276/ L-100 cam is no fluk , I waz there and drove it. 4.11 gears and a T-5 makes it come off the line with no trouble at all.
I was impressed. Tuning can be fun.

Re: Bubba's chevy conversion dist.
 

Great knowledge sharing here, guys, thanks to all the contributors.

Mart.

Re: Bubba's chevy conversion dist.
 

many distributor wizards on here

Re: Bubba's chevy conversion dist.
 

The 11A is next!!!

Re: Bubba's chevy conversion dist.
 

The 11A could very well be the best distributor ever made (right up there with the chevy v8).
I thought i had covered every aspect of the 11A unit but got one in from a customer this morning that someone had bent the springs ( why i dont know) and the cam would stick mid range most of the time .
Would start good and then start bad was causing quite a problem.

Maybe we should write another thread on the very mis-understood vacuum brake on these and the helmets etc ??

What ya think...??????????

Re: Bubba's chevy conversion dist.
 

Yes, please.

Z

Re: Bubba's chevy conversion dist.
 

Richard. Maybe you could post the degree strip.

Re: Bubba's chevy conversion dist.
 

Sounds like a good idea but I suspect that with all the differences in the way printers and systems reproduce, the strip may not print out to exact scale.

Re: Bubba's chevy conversion dist.
 

I thought of that, so the scale pdf includes a reference line of specific length. You print once, measure that line, then adjust your printer accordingly until it's on the money.

Re: Bubba's chevy conversion dist.
 

Crank pulleys come in different diameters and the diameter is critical to making the strip accurate.

I don't mind filling requests. Otherwise, the files would get lost in the shuffle.

Re: Bubba's chevy conversion dist.
 

Unfortunately most don't have the knowledge or ability to adjust their printers.
Perhaps a better way would to be provided with dia. of pulley then give measurement for 10 deg. increments.
For example 6'' dia. pulley = .523" per 10 deg.
So rather than printing it can be layed out.

Just a thought

Re: Bubba's chevy conversion dist.
 

A 1/2" wide strip of paper can be wrapped around the pulley so that it overlaps and cut across the overlap. This will give an accurate circumference, fold it exactly in half for 180*, fold the end in to the crease for 90* and again for 45*. Next fold is 22.5* and if you have folded and creased carefully it will be at least good enough to work out the diameter for Richard's strip. ..B.

Re: Bubba's chevy conversion dist.
 

You don't have to figure any dia's. that way.
Just measure the length of the circumference and divide by 360 to give the length for 1deg. or divide by 36 to give the length of 10 deg. etc.etc.

Re: Bubba's chevy conversion dist.
 

In actual fact, the number I need is indeed the circumference. I usually ask for the diameter because some guys know that number from their build days.

Re: Bubba's chevy conversion dist.
 

Anyone interested might want to check with Speedway Motors. They have "Timing Tapes", marked in degrees, for 6", 6-3/4", 7" and 8" diameter pulleys/balancers. They are marketed for Ch--y engines but will work nicely for any engine with the specified diameter pulleys or balancers. I modified the pulley on my 8ba to use one.

Re: Bubba's chevy conversion dist.
 

I agree with Jim the 11A is definately the best distributor available for the pre 49 engines. They get even better when converted to electronic. However I do thing the advance curve could be improved and that's one of my projects. It's quite simple:
Lighten the springs by grinding them down enough toge all the advance in by 2000.
and lengthen the advance slot to 28 degrees. Unfortunately thid depends on the vacuum brake doing it's job.
I discovered that my stock test engine has a broken area in the exhaust port under the front blind hole. Not sure how to fix this with the equipement I have and with out dissembling the engine. Today ewe installed the radiator and added water . After start up the drivers side exhaust looked like a fire hose.
This is very depressing and I will have to reevaluate my test schedule. Might have to go to the 280 now. I was hoping to have the truck running in a few weeks to work out all the bugs.

Re: Bubba's chevy conversion dist.
 

great info here.
thanks.
rich

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Ordered a timing light with advance from Amazon almost ready to go.Richard,Ron and Bubba,THANKS ,Phil

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Just finished installing the Bubbas conversion.Set the inital timing on the dot with vac adv. plugged.Reved the engine has about 16 deg mech.Connected the vac.at idle dot moved about 8-9 deg.The engine idles better and has better throttle response.MISSION ACOMPLISHED. THanks for all the help. Phil

Re: Bubba's chevy conversion dist.
 

With the vacuum disconnected and plugged again, try increasing the maximum mechanical to about 20. You'll get a little more oomph. And if your vacuum is adding 8 degrees, you're right in the ballpark.[/QUOTE]

Re: Bubba's chevy conversion dist.
 

Yes a new thread on adjusting the Vac brake and also fudging the max adv with the inital, which isn't that importanr. As long as it starts, who cares.

Re: Bubba's chevy conversion dist.
 

OK, I need some help here because the statement, "If you get a digital timing light, you don't need a degree strip.", completely befuddles me.

I looked at an Innova demo on U-Tube, but it did not help me understand. If you do not have a tape or marking on the crank pulley, does the light only flash when the advance matches whatever you set in? What am I missing here?:confused:

Re: Bubba's chevy conversion dist.
 

It sort'a befuddled me too untill I got one and learned how to use it.
It's too complicated for me to fully explain here. (get one and learn)
Anyway, all you need is the T.D.C./timing mark on the pulley.
For example, if you want to advance timing 6 deg., with light aimed at timing mark and pointer, punch in 6 deg. to advance , the mark on pulley will move 6 deg., rotate dist. to bring timing mark and pointer back into alignment and lockdown. It's now 6 deg. advanced. No degree strip needed.
(probably clear as mud) This is example of one like I have--also a link to demo
https://www.youtube.com/watch?v=ViDA9IrkTtI

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Thanks, 51. I guess I do not understand how the darn thing gets its inputs.

When you said that you do not need a degree strip to set the timing that intrigued me because of what I'm doing. I put the late timing gear cover on a 59A to adapt a Chevy distributor to it. I took an 8BA crank pulley and cut off the timing bell. I reversed it and welded it to a 59A crank pulley. I used the crank key way as the reference for where to locate the timing dimple. I doubt that I have it exact so it will be just a starting reference point for TDC. This is why I thought this digital timing light could help me nail down the timing.

Seems like the cheaper light with the round dial to set the desired advance is all we need for this job, but I kinda like the red ones with the protective covers. Are the ones like you pictured pretty sturdy?