Carb return spring - early style

[wayne1230cars]

I rebuilt my 36 hp engine this past winter. While the motor was out, I had the engine tin powdercoated and detailed the engine. The old carb return spring for my 28 PCI was not looking so great, so I decided to order a new one. When, I got the motor back in I noticed that the accelerator cable(new) was sticking and often would not return to the idle position. I adjusted and lubricated but the problem persisted. Finally, I removed the new spring and compared it to the old(which fortunately I had kept.) They measured identical but the tension strength of the old spring was susbstantially stronger than the new one. Cleaned the old one up and reinstalled. Problem solved. Moral of the story - don't throw the old part away until you are sure the new one is going to work.

[KTPhil]

[my59]

Oh so true!
FYI the bolt holding the accel. cable barrel nut tight originally was a set screw. I found mine stuck in the engine tin where someone dropped it decades ago.
_________________
my59: Well son, my grandfather died before I got to drive it, so does that answer your question?
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[wayne1230cars]

Good point. I went through my container of assorted VW parts and found the original set screw barrel. Installed it and adjusted the cable so there is the correct clearance on the carb when the accelerator pedal is pushed to the floor( a frequent occurence on a 36 hp).

[glutamodo]

Me too, I'm still using an old set screw type on my 62 - although I did change the throttle arm out for one that was not nearly as ovalled-out in wear where it sits after this photo was taken:

[HRVW]

Decades ago would use a 90 degree metal corner brace...drill a 8mm stud size hole in one end and a 1/8 drill size hole in the other end.

Installed the larger hole part under the carb stud with it's holding nut. Connected a spring to the small hole and to the carb throttle arm. Never had any problems with the idle not returning. Did this on customers early 36hp and the early 40hp cars.

[wayne1230cars]

When did they change from set screw to bolt?

[glutamodo]

that one, I don't know offhand. The newest illustration in the various Bentely manuals shows a 30PICT2 and it has the slotted style. So that would be 1968-69 they were still using it.

[HRVW]

What had/has happened with the early carbs is people over tightening the nuts on the stud and as a result stripping the threads in the carb base thus the bolt repair. Tis a shame but that is what happened...saw many over the yrs.

Steve

[glutamodo]

I thought by set screw, he meant the style of barrel clamp, not the rear stud changed to a bolt on the carb.

[wayne1230cars]

I did mean the style of barrel clamp. The other explanation is interesting. My 28 PCI carb has had an insert installed on the front stud. So, very likely a victim of overtightening as suggested above.

[glutamodo]

Overtightening is one reason, for sure, but I think sometimes it's simply metal fatigue. My 28PICT in that photo above, they just plain wore out - and they were fine when I was given that carb 20 years ago. But both of the bottom studs eventually pulled out on that - and I don't overtighten. One of the screws that holds the top on also pulled the threads not too long ago.
-Andy

[HRVW]

Do have a few barrell screws left over from my parts house days. Ordered some and they came w/o the tiny bolt (useless to say the least) Do have some bolts so nothing completly lost if anyone is interested in one.

[glutamodo]

I was just leafing through the old Car of the Century book and found that it says the bolt style barrel clamp came around when the throttle return spring change happened in mid 1966. BUT, then why do the factory books still show it the old style with the later 30PICT-2 carb?

[herbie1200]

The spring can be horizontal (old style) or vertical (new style).

The two configurations are not mixable, because old style works well only with:

- "no wheel" accelerator pedal assembly
- solid type cable
- "no spring" carburetor

The 1st solution, the old with horizontal spring on cable, has an advantage: throttle bushing is not intersted by the retaining force to return to idle, so throttle bushing are not stressed.

The 2nd solution, cable free and spring vertical on carburetor, suffers for a rapid erasure of throttle axle bushing.

[jzjames]

[herbie1200]

[jzjames]

That makes sense! And Ive never heard that reasoning before.

[glutamodo]

And then there's the final few 34PICT series carbs that had a radial return spring in that worked along with the throttle arm spring... I don't know why they made that change, and if it made any difference in wear.

[herbie1200]