Vacuum advance dist. for Model A

[mcgarrett]

Is anyone making or modifying a distributor for Model A engines that incorporate vacuum advance? I know about the Rex-a-co centrifugal advance unit, but it's not vacuum controlled. Has anyone ever modified a distributor like the Bosch 009 for example that would work well in the Model A engine? Would there be any benefit especially when running high compression heads?

[AL in NY]

I have read on here somewhere that a 70's (?) Honda distributor can be modified to fit the Model A.

[Kurt in NJ]

you have to be careful with 70s distributors, some have vacuum retard.
some Subaru ones also could be used, all will require modifications to the advance curve

[Gene F]

Isn't there a way to use a VW distributor from an old beetle?

[Bob C]

There is a thread on this site using a Honda distributor.
https://www.fordbarn.com/forum/showthread.php?t=244492

[AzBob]

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I run a modified Honda civic points distributor (Hitachi 1975) with mechanical and vacuum advance. It performs wonderfully. Set up 2 years ago and haven't touched it since. Bullet proof.

I made all the modifications myself and do not know of anyone who supplies them for a Model A. The Honda distributors of that era are becoming harder to find.

[Jim Brierley]

For a dist with vacuum advance you will need a carb wit a port for that, most vacuum dists don't use manifold vacuum. I doubt if there would be enough improvement to notice?

[AzBob]

Originally Posted by Jim Brierley

For a dist with vacuum advance you will need a carb wit a port for that, most vacuum dists don't use manifold vacuum. I doubt if there would be enough improvement to notice?

Jim, In my case, I am running a Weber 32/36 with the vacuum port. Hooked the vacuum line from the distributor to the vacuum port on the carb. Works great for cruising, improves mileage. When more throttle is needed, you get vacuum retard.

[ModelA29]

#3 cylinder on old VWs ran 3 degrees of retard. That cylinder was shrouded by the oil cooler and they retarded the spark to keep it a little cooler. The Porsche 356/912 distributors had evenly spaced distributor cams.
The air cooled VW used a clockwise rotation distributor and the Model A is CCW.

[Gene F]

Does the rotation direction matter?

[Dodge]

I'm using a Rover 4cyl. dist. with vacuum advance. You can get them with points or
electronic ignition. Easy conversion.
Carburetor is one of the new Stromberg 97's with a vacuum port.

[Gene F]

Originally Posted by Dodge

I'm using a Rover 4cyl. dist. with vacuum advance. You can get them with points or
electronic ignition. Easy conversion.
Carburetor is one of the new Stromberg 97's with a vacuum port.

Isn't that a downdraft, with 3 mounting holes to the manifold? Where did you get that?

[Dodge]

Summit Racing

[Phil Brown]

Originally Posted by Gene F

Does the rotation direction matter?

Yea, the advance is backwards. You can change the Bosch 009 ( A centrifugal advance only distributer) by revirsing the way the weights advance.
Also the 009 type does not retard the #3 firing, that only happens with the early factory used VW stuff.
The 009 and 050 Bosch can be made to work well but again there only centrifugal advance not what the OP is looking for

[Synchro909]

I've been running a modified Nissan distributor on my Burtz engine and love it. It was done by "Performance Ignition" in Nunawading, Melbourne. I have used them before and been impressed each time. A bonus for you guys is that the exchange rate works FOR you but unfortunately, AGAINST us.

[Hitman]

Originally Posted by ModelA29

#3 cylinder on old VWs ran 3 degrees of retard. That cylinder was shrouded by the oil cooler and they retarded the spark to keep it a little cooler. The Porsche 356/912 distributors had evenly spaced distributor cams.
The air cooled VW used a clockwise rotation distributor and the Model A is CCW.

This is not correct as you stated. VW did this only for a handful of years, and not for the reason you stated. It only occurred in the 69-72 VW’s that were 1600cc before they went to the doghouse cooler.

This didn’t happen with the 356/912 distributors. Those cars used different distributors. The distributor rotation has nothing to do with any of this.

[Hitman]

Originally Posted by Phil Brown

Yea, the advance is backwards. You can change the Bosch 009 ( A centrifugal advance only distributer) by revirsing the way the weights advance.
Also the 009 type does not retard the #3 firing, that only happens with the early factory used VW stuff.
The 009 and 050 Bosch can be made to work well but again there only centrifugal advance not what the OP is looking for

I wouldn’t bring the 009 into this discussion. It’s a centrifugal advance distributor but needs a carb that is properly matched. 009’s are very particular.

Most carburetors are designed for distributor advance, mechanical, centrifugal or manual. It’s best to match the distributor advance mechanism to the carb advance. Just because it fits doesn’t mean it’s appropriate.

[Bruce of MN]

Originally Posted by Hitman

Most carburetors are designed for distributor advance, mechanical, centrifugal or manual. It’s best to match the distributor advance mechanism to the carb advance. Just because it fits doesn’t mean it’s appropriate.

Pardon my ignorance, but what is carb advance?

[Will N]

I never understood the need for vacuum advance until I researched it yesterday after seeing this thread. I always figured an engine develops its highest vacuum when the throttle is closed or slightly opened, and wouldn't need advance under these conditions. But I read that when cruising at a steady speed and only a little load, the throttle is only partly opened, increasing vacuum, and also the fuel/air charge going into the cylinders is restricted by the throttle. This less dense charge of fuel/air takes more time to burn because, well, it's less dense. And because it takes longer to burn you need the spark to occur earlier. Fascinating.

[Phil Brown]

Originally Posted by Hitman

I wouldn’t bring the 009 into this discussion

I didn't, try rereading post #1

[Hitman]

Originally Posted by Bruce of MN

Pardon my ignorance, but what is carb advance?

Most modern carbs are designed for the distributor type they came with. For example, VW's run a variety of Solex carbs. The most popular Solex 34 PICT-3 is designed to run with the aluminum bodied Bosch vacuum advance distributors. When you put the mechanical advance Bosch 009 distributor on with that carb, they have a flat spot because the distributor ins't advancing like a vacuum distributor does. So it creates a flat spot until the distributor catches up to the carb. During VW's air-cooled era, they had at least three dozen different distributors they used in production.

Bosch 009's are good distributors, but are often times put on an engine as a bandaid to the real issue, often a poorly matched carb to a vacuum distributor. I have VW's and I don't run 009's, I use the pertronix distributors or early 010 or 019 distributors with mechanical advance.

[ModelA29]

Originally Posted by Hitman

This is not correct as you stated. VW did this only for a handful of years, and not for the reason you stated. It only occurred in the 69-72 VW’s that were 1600cc before they went to the doghouse cooler.

This didn’t happen with the 356/912 distributors. Those cars used different distributors. The distributor rotation has nothing to do with any of this.

ALL the early VW (1949 to 70 style cooling) and even the early mechanical only 009 (developed by Bosch for VW and installed as stock on some cars and stationary engines) had the retarded cam. After 1971 it wasn't needed. The trick mechanical (no retarded cam lobe) distributor has always been the hard to find Bosch Porsche 010. Yes distributor rotation of a VW/Porsche dizzy used on a VW or Porsche doesn't matter but it won't work right when you spin it backwards. Today you can buy a new ChiCom 009 on ebay for less than $30 cheap enough to play with.

https://www.vwnos.com/0-231-129-010?...caApahEALw_wcB

VW-resource.com wrote: A problem occurs in mismatching the 009 distributor with the doghouse-type oil coolers. Up to and including 1970, the oil cooler was internal to the fan shroud, and this meant that the #3 cylinder (left front) got warm air for it's cooling and therefore ran hotter than the others. So VW altered the timing on the #3 cylinder only -- the cam in the vacuum distributors has #3 cut 2-3 degrees later than the other three cylinders, to reduce the heat load on that cylinder a little. The early 009 distributors also had this feature.

But since 1971 the engines have a doghouse oil cooler that sticks out the front of the fan shroud. After passing through this oil cooler, the hot air is dumped overboard through some extra tinware. The fan itself is a little larger to supply this extra air. You should be able to see/feel this cooler sticking out the front of the fan shroud (front is front of car), slightly left of center. When you're under the car you should be able to see the rectangular air outlet in the tinware just above the bell housing. If the shroud is smooth/straight right across the front of the shroud, you have the earlier type of "in shroud" cooler.

So with the newer type oil cooler, the #3 cylinder now gets nice cool air for cooling, and the retard on #3 is not needed. The double vacuum distributors therefore have no retard on the #3 cylinder (double vacuum distributors were only used on '71 and later engines). VW dropped the retard on 009 distributors about 10 years ago too. So some 009 distributors have the retard, some don't. You need to make sure you have the right one. The only way to tell is to time the engine on #1 as it should be, then look at the timing for #3 (turn the engine 360 degrees). If the points open at the same time, okay; but if the points are opening later (the timing mark is now more about 4-5mm to the right), it's the wrong 009 distributor for a doghouse cooler engine.

[AzBob]

Retard no.3 cylinder for cooling? Perhaps air cooled VW engines behave differently than a Model A engine. When I retard my Model A engine, it runs hotter. What am I missing?

[nkaminar]

Arizona Bob. I think it is a matter of degree. Two or three degrees may make the engine run cooler, especially on a higher compression engine. That is one notch on the ignition lever on a Model A. The very slightly retarded ignition means that cylinder is not producing as much power and will run cooler by a few degrees. This is all guess work on my account. I am trying to put myself in the mind of the VW engineers.

[AzBob]

Originally Posted by nkaminar

Arizona Bob. I think it is a matter of degree. Two or three degrees may make the engine run cooler, especially on a higher compression engine. That is one notch on the ignition lever on a Model A. The very slightly retarded ignition means that cylinder is not producing as much power and will run cooler by a few degrees. This is all guess work on my account. I am trying to put myself in the mind of the VW engineers.

Thanks nkaminar. Sounds plausible. This now makes sense to me considering the slightly retarded no. 3 cylinder will make a little less power and thus run cooler by a few degrees.

[Hitman]

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Originally Posted by ModelA29

ALL the early VW (1949 to 70 style cooling) and even the early mechanical only 009 (developed by Bosch for VW and installed as stock on some cars and stationary engines) had the retarded cam. After 1971 it wasn't needed. The trick mechanical (no retarded cam lobe) distributor has always been the hard to find Bosch Porsche 010. Yes distributor rotation of a VW/Porsche dizzy used on a VW or Porsche doesn't matter but it won't work right when you spin it backwards. Today you can buy a new ChiCom 009 on ebay for less than $30 cheap enough to play with.

That’s not correct. The Bosch 010 distributor was a VW bus distributor used only one year, and used in industrial applications for years after that. The Bosch 009 distributor was a two year VW bug distributor and used extensively in industrial engines later. The 009 never had the #3 cylinder retard. I don’t think the 009 distributor is good on T’s or A’s because they are centrifugal advance and don’t fully advance until 3000 rpm. Quality points and condensers are extremely hard to find these days.

VW’s ran hot on the #3 for reasons that had nothing to do with the oil cooler.

[nkaminar]

Modern cars, of course, have a computer and bunch of sensors to control ignition timing. The Model A in stock form relied on the operator to control the ignition timing. In my case this is just fine as I have gotten used to using the ignition lever over the last 60 years of driving Model A's.

[Bob C]

Originally Posted by Hitman

That’s not correct. The Bosch 010 distributor was a VW bus distributor used only one year, and used in industrial applications for years after that. The Bosch 009 distributor was a two year VW bug distributor and used extensively in industrial engines later. The 009 never had the #3 cylinder retard. I don’t think the 009 distributor is good on T’s or A’s because they are centrifugal advance and don’t fully advance until 3000 rpm. Quality points and condensers are extremely hard to find these days.

VW’s ran hot on the #3 for reasons that had nothing to do with the oil cooler.

And the reason was??

[Hitman]

Originally Posted by Bob C

And the reason was??

Briefly, the #3 cylinder on a VW is like the #4 cylinder on an A. It's out of the way and doesn't get as much cooling as the other cylinders do. The #3 in a VW is the forward most cylinder due to crank journal spacing, and it's out of the direct airflow from the cooling fan. The #4 receives air directly on that side. It runs hotter due to the lack of air flow, and even then only ran hotter when they went to a 1600 cc engine with a higher compression ratio.

Pre 1971 the oil cooler is in the cooling airflow path of both the #3 and 4 cylinders, but only #3 runs hotter.

Happy to discuss further offline since this is off topic.

[Tanglfoot]

Hello all, I am with Synchro 909. I have used Nissan Navara Distributors from around 1990 with good results. They are easy to adapt and parts still available here. Cheers Rosco

[Bruce of MN]

I see that Nissan is a light pickup. At https://www.rockauto.com/en/catalog/...stributor,7108

it shows Mitsubishi and Hitachi types, which one is preferable? (I see one is out of stock)

[AzBob]

Originally Posted by Bruce of MN

I see that Nissan is a light pickup. At https://www.rockauto.com/en/catalog/...stributor,7108

it shows Mitsubishi and Hitachi types, which one is preferable? (I see one is out of stock)

I don't see a vacuum control canister on any of those Nissan distributors.

If you want points ignition you are going to have to go earlier than 1980. Prices for the Honda Civic distributors used to be in the $25 to $100. range.

Perhaps Tanglfoot or Synchro 909 can post a picture of their setup.

[nkaminar]

Can you stick that vacuum actuator that Arizona Bob posted on the ignition advance lever?

[Fordestes]

Originally Posted by AL in NY

I have read on here somewhere that a 70's (?) Honda distributor can be modified to fit the Model A.

I built some using 1980 Honda 1.5 litre distributors , two I left the vac. advance on so the person can set it retarded in order to crank start , then the vac. pulls adv. to Idle setting, on one unit I blocked the vac. advance, set the total to 30 degrees. seems to do to job, the repair parts are easily bought from auto suppliers when service is needed . I like it just as good as an F.S.I ,which is a nice unit , which uses a Pertronix module . have had zero complaints .

[Fordestes]

Originally Posted by Gene F

Isn't there a way to use a VW distributor from an old beetle?

The V.W distributors work pretty good in a Model T , the rotation is clockwise and the A is counter clockwise,

[Dave in MN]

I have modified a couple Lucas 25D vacuum/mechanical advance distributors for use on high compression heads. I need three more for engine builds in the works. I get them on Amazon for about $80.00. The lower part of the distributor needs to be machined so it fits the Model A distributor hole.

I ran one on my round trip roadtrip which included touring Alaska last summer without issue. The entire trip was 11,500 miles.

When I modify the next three distributors, I will add some photos to my post.
Good Day!