FYI - Carter 1BBL - SPRING Carburetor Step-Up Piston

[James_Douglas]

Hi guys,

 

Those of you who have followed my threads over the last few years will remember the issue of the step-up-piston hanging up.  No doubt do to slight corrosion in the housing by alcohol flashing off the bowl and getting sucked past the step up piston by engine vacuum.

 

I now check that piston every six months.  A stuck closed piston will cause a lean condition at freeway speeds and that is not a good thing.

 

A week ago I did my 6 month check and things looked good except that the piston had a scratch in it like some crap got sucked past it.  With all the filters on this car it is beyond me what it was.  So, I pilled out the piston and polished it. 

 

While I was at it, I got curious. A few months back when Radio Shack closed a bunch of stores around here, I picked up two of the big electronic small part cabinets that were in all the stores.  I then used them for things like nuts and bolts, electrical, small hardware and the like.  I also set one drawer to nothing but Carter 1BBL small parts.  I stripped 5 or 6 carbs I had and put all the parts in the drawer.

 

So, I was able to quickly pull out a bunch of pistons and springs.

 

What I noticed was that the springs looked different.

 

I then examined all the springs close.  Guess what?  Different.

 

All the springs had the exact same wire diameter. But, they had a number of different coils numbers.  I ended up testing 6 or 7 springs.

 

I took the spring that had the largest number of coils, like an extra 4 coils,  and put it in the car.

 

I have to say it makes a very big difference in mid-level to full throttle acceleration.

 

Of course that makes sense.  With the same vacuum level and a stiffer spring the piston will lift sooner and allow more fuel sooner.

 

This will also allow for a richer mixture at highway speeds.  This will provide some benefit in cooling, but of course will use more gas.

 

I know that in the past several people in the know have suggested that with the addition of alcohol in the fuel that the jets could use to be 5%-10% larger to compensate for the BTU loss.  A slightly stronger spring basically does the same thing.

 

I will run the car for a few weeks and "read" the spark plugs and see what they look like.  I can say that in around town traffic here in San Francisco, and on freeway on ramps, I definitely notice the difference.

 

Since I did not touch anything else, this is an area that people may want to look at to fine tune their cars.

 

James.

[Jeff Balazs]

James;

Interesting topic. I wonder if there really were different springs back in the day? Or if there is more info on this topic in some tech literature of the period? It seems like a difference that might be "stumbled" across.....but one that may not show up unless you were to have a large collection of parts to rummage through.

 

Jeff

[Don Coatney]

Where can these heavy springs be found? What carburetors were they used in?

[Dodgeb4ya]

I looked this up in the Carter master parts books...

For all lines 1942-53 Chrysler/DeSoto/Dodge/all dodge trucks to 4 ton and Plymouth cars I saw two different step up spring part numbers..

 

Carter #61-134 and #61-135.

 

Spring #61-135 was the most common one used and also a note that for one model of the 1942 DeSoto the # 61-134 was to be superseded the #61-135.

 

No technical info on the two springs was noted.

[James_Douglas]

I have the carter parts book as well.  There are a few springs part numbers that are different across the years and make/models.

 

The problem is that there is nothing in the book about the number of coils.  All the springs were the same dia in my parts bin.

 

So, unless someone can come up with a bunch of NOS carburetors and match those springs to the carter parts book we are all in the woods on this one.

 

I posted the info so people would be aware and can try some trial and error.

 

Of course since this piston is sucked closed by engine vacuum, the condition of the engine and the loading will make a difference.

 

In my 5000 pound suburban one spring may work great but in a coupe it may be too much.

 

I just wanted to let people know that there is a range of springs out there.  I am sure some rebuilding houses also supplied different springs to make their rebuilds "perform good" as a marketing ploy.  So, unless one has an NOS carb never taken apart...

 

Best, James

Edited February 22, 2016 by James_Douglas

[Dodgeb4ya]

I think a lot of carbs over the years have had mix and match done to them.

If it runs good enough.... be done with it.

[James_Douglas]

I think a lot of carbs over the years have had mix and match done to them.

If it runs good enough.... be done with it.

 

Some of us like to optimize :-)

[Jeff Balazs]

Some of us like to optimize :-)

That could be the difference between OK and better than OK. Sometimes it is just some small...almost no difference type item like this. And how would you know it even existed without a discussion like this? I am of the opinion that these older vehicles need to be optimized in order to begin to be operated safely in todays' traffic. I've read many times where someone takes one of these cars or trucks out on the road in less than good operating condition. Makes me cringe. You just can't count on the people you share the road with to cut you any slack.

 

Jeff

[Dodgeb4ya]

By runs good enough I mean no one would feel or see a problem.

I have a friend who spends way too much time trying to get his slant six engines to run absolutely perfect ...flawless never a miss at 3000 RPM ect.

He worries about these issues and makes him a nervous Nellie.   Stupid..

[Jeff Balazs]

By runs good enough I mean no one would feel or see a problem.

I have a friend who spends way too much time trying to get his slant six engines to run absolutely perfect ...flawless never a miss at 3000 RPM ect.

He worries about these issues and makes him a nervous Nellie.   Stupid..

I get what you are saying.......but don't you think that he probably just has that tendency as part of his natural makeup or personality?

I do know that when I first started driving my truck it had some hesitation during acceleration from a stop. When the engine was still relatively cold it actually stalled  a few times. Definitely a bad thing in the traffic here. It took me a while to find the solution.......and that was something very small and subtle....similar but not the same as the difference James describes here.

 

Jeff

 

Jeff

[James_Douglas]

I made a run today some 160 miles round trip with a lot of 60-70 MPH running.  On the hills at about 2/3rd throttle I think that spring made a difference.  I did not have to floor it as much on a trip I make often with the car.  Better roadability.

 

James.

[Dodgeb4ya]

I get what you are saying.......but don't you think that he probably just has that tendency as part of his natural makeup or personality?

I do know that when I first started driving my truck it had some hesitation during acceleration from a stop. When the engine was still relatively cold it actually stalled  a few times. Definitely a bad thing in the traffic here. It took me a while to find the solution.......and that was something very small and subtle....similar but not the same as the difference James describes here.

 

Jeff

 

Jeff

I've tried to break this friend of going crazy to trying make his old Valiants run perfect... that they were not. They used carter and holly carbs.. both had issues.

 He's really good at fixing cars. He just wastes so much mental energy on these things where as he should get over it and drive them as they all run well.

He's the way he is and that's OK. It's his way.

I drive all my cars and trucks doing the normal maintenance plus listening /feeling that they run well enough and thats it, and I've never had any serious trouble with any of them.

 keeping my fingers crossed Ha Ha 

[Niel Hoback]

Some people work crossword puzzles, some collect stamps, some work on cars. He won't go crazy working on his credit, but he's probably happier than if he did nothing.

[Dodgeb4ya]

It's good that people like James bring to light some of these possible parts issues causing drivability issues.

I tried to see if I had some new Carter springs to ID the differences but had no NOS Carter step up springs.

 

So what size/ length / # of coils spring belongs to what model of carb?

 

This could be hard to figure out with old used step up springs that are possibly stretched or compressed with use or mishandling over the years.

 

New springs usually are found loose in the Carter parts bins all mixed up and out of the OE wrappers!

Bob

 

 

 I remember now I still have some NOS Carter carb kit boxes to look through!

Edited February 24, 2016 by Dodgeb4ya