Reproduction Parts for 1916-1964 Chevrolet Passenger Cars & 1918-1987 Chevrolet & GMC Trucks


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Me again with the 38 Master Sedan. I finally got the 38 started after a year or so passing and she ran better than ever until gas started leaking out of the Rochester. I decided to replace the Rochester with a Carter W1 which seems straight forward enough but no so. The vacuum line didnt fit so I modified the Rochester fitting to connect the vacuum line. I also removed the cable clamp from the Rochester to connect my throttle and choke cables. All seemed well, starting was a bit of a challenge but she finally started but running poorly. The vacuum fitting has a small orifice in the fitting which seemed to work well on the Rochester, but maybe not on the Carter
-The W1 is from a 42 Chevy, but i hoped it would not make that much of a difference.
-Any suggestions on how I can smoothen my idle because it is running pretty rough, especially compared to when the Rochester was on there.
Thanks for the help
Michael
PS. So close but it seems like small things keep popping up. I attached some pics

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Last edited by solafide; 10/04/22 07:58 AM.
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Hi Michael,

It is going to take some organized troubleshooting to resolve this.

Is the problem only at idle?

One quick test is to disconnect the vacuum line to the distributor and just plug that hole. That should not make a difference because there should not be a vacuum signal at that port when the engine is at idle.

One other “Gene” trick is to swap the #3 and #4 spark plug wires. That should make the engine fire back through the carb idle passages. Those passages are very small and tend to easily plug.

Another trick is to rev the engine with your hand over the intake. Wear a glove or wrap a rag around your hand. As you rev the engine close off the intake. The should pull gasoline through the main passages and main jet to clear out any dirt.

I just went through a similar scenario with a W1 on a ‘49 3100. Just go to my profile and check my posts.


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Thank you for th advice, I know little about carbs and less about Carters. The gent who rebuilt the carb is going to give me a call and coach me through troubleshooting too

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I am watching this post with interest as I am also planning on changing back to a Carter W-1 from the Rochester on my 37 Chevy Master Sedan. I believe the Carter I have is from a 1937 based on the 838526 tag attached. VCCA member Dean Echols is currently rebuilding my crusty Carter as we speak. May I ask who rebuilt yours? I was hopeful that switching from Rochester to Carter carburetor might have been just a matter of bolting it on but that doesn't appear to be the case.

Terry
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Does your W1 have split choke plates? 1937 was the only year for the split choke plates.


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Hate to partially disagree with Rusty, all Carter W-1 up to and including '37 have split choke plates. '32-'36 have straight throttle arms. 1937 starts the dogleg throttle arms. '37 & '38 have the 90 deg. horizontal part with a hole in it for the throttle cable (retained by cable clamp) to fit through.


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1937 and proier have split choke plate - 1938 and up is one piece,

Last edited by Chev Nut; 10/04/22 10:33 PM.

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I didn't think I had a picture down the throat and the carbs is being rebuilt but looks like I do.
In my mind's eye, I had thought there were two pieces with a spring in between but hadn't thought any more about it at the time.

Good to know when looking at carbs as they sort of all look alike.

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I believe my W1 is from a 42 Chevy, I didnt think it would make a difference but maybe i'm wrong. I bought mine from a gent on ebay who is out of Northern Ca. The Rochester actually worked well until gas started leaking our of the throttle side

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Thanks for the clarification. I mis-interpreted what I read on Carbking’s website.


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Will the engine run ABOVE idle?

The W-1 has a very small connector passage in the idle circuit. Virtually all W-1's that have been sitting idle for years will require removing the passage access plug, and removing the clog in the cross passage. The passage can be tested while the carburetor is apart to determine if this step is necessary.

Also, removal of the idle jet REQUIRES either a new jet, or the end of the jet that seals in a tapered passage to be expanded.

Either of the above will cause a very poor to no idle.

Hopefully, the gentleman who rebuilt your carb was aware of these possible issues.

As far as the interchange, other than the throttle arm connection, the '42 carb will work fine on the '37.

Jon.


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Thank you, that’s a comfort, just bought a W-1 bracket. The W-1 is on a 38.

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Ok, my newly rebuilt W-1 arrived without the fitting for the vacuum line. I could not attach the vacuum line so i robbed the fitting from the Rochester, ground it down, threaded it and installed on Carter. The Rochester vacuum fitting has a very small orifice leading me to wonder if it is correct for the Carter as i have no sample. I cannot find a fitting to mate the vacuum line and W-1 carb.
-Would someone please show me the correct connection from the distributor to the W-1?
-Can someone provide me a source for the proper fittings for the vacuum line and Carter?
Thank you as always

PS. Last image is a Carter with a fitting installed, but looks too large for mine, my vacuum fitting is 5/16"

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Last edited by solafide; 10/08/22 02:39 PM.
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My W-1 on my "40 has that same restricted fitting. Not sure but I think the restriction is to keep the distributor vacuum advance from increasing and decreasing too rapidly as the vacuum increases and decreases. If your ground down fitting works I wouldn't worry about it unless it looks boogered up.


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I agree.
It was originally dome to correct a minor surging problem in 1939 and 1940.


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solafide

You have not told us if the poor running is only at idle.

Did you run the engine with the vacuum line disconnected & the port in the carburetor plugged?


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I will let you know as soon as I can, have a small coolant leak from the temp probe housing. I have to drain some coolant before adding some Teflon tape to fitting. I just received my correct choke/throttle bracket too. It’s the little things that are tripping me up but failure is not an option

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Ok, started her and ran her til warmed up, idling terribly with or without vacuum line connected and I did plug carb as suggested. I installed new fuel filter too. She runs worse when she is warmed up and I have to have the choke engaged or she will die

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Then you either have a massive vavuum leak or not enough gas in the bowl or something is plugged up.


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Should I try the swapping plug wires 3 & 4 and or Devine engine and covering intake? I messaged seller for suggestions too.

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Alright, 2 things here...

First,
The vacuum line fitting you used from the Rochester...
You ground it down to fit ?? (appears that way in the picture)
That WILL NOT WORK, and if this is what you have done, YOU NOW HAVE A VACUUM LEAK at that point.
Find the right fitting for the job and hope you haven't ruined the threads in the carburetor.

Second,
Does turning the idle screw in and out make little or no difference in the way the engine idles?
If so, Jon has given you the answer above.
You will need to find someone who can remove the plugs from the idle passage(s) and clean the passages, and especially the economizer jet, properly.
Nothing else will work.

Last edited by Stovblt; 10/15/22 11:38 AM.

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I ground and tapped the thread. Where can I find the correct fitting, I tried Autozone, Napa, oreilly, ace, Home Depot and Lowe’s. What is the idle screw? The screw with the spring does nothing, i thought it was the fuel/air mixture screw. I am waiting for the seller to call, I sent him a copy of the carbking post asking if this might be the case.

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If the idle mixture screw does nothing the idle circuit is probably plugged up.


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I should have been more clear.
Sorry about that.
When I said idle screw, I was referring to the "idle mixture" screw.

Most old carburetor cores will still have the vacuum fitting in them. (the ones I have do)
Possibly you could contact one of the members nearer to you than I who rebuild Carter carburetors and ask if they will sell you one?

Otherwise, it's been a while since I had mine off, but isn't this the fitting you are looking for:

https://www.amazon.com/Generic-Brass-Compression-Connector-Fitting/dp/B00CHHYRT4/ref=sr_1_10?crid=1TAPDINKG4YE&keywords=brass%2Bfitting%2B1%2F8%2Bpipe%2Bcompression&qid=1665875594&sprefix=brass%2Bfitting%2B1%2F8%2Bpipe%2Bcompression%2Caps%2C117&sr=8-10&th=1

If at a hardware store, ask for a brass "1/8" male national pipe thread" to "1/8 OD tube" compression fitting.

Last edited by Stovblt; 10/15/22 07:20 PM.

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I keep waiting for a key answer

Does the engine run smoothly at speeds higher than idle?


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No

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Coming from Carter's own service information,
and confirmed by my own experience...

On Carter W1's, the idle circuit continues to be the primary source of fuel well beyond "idle speed".
Especially under "no load" conditions.
So... with a plugged idle circuit the engine will run rough well up in revs.
Even on the road under load, the idle circuit doesn't completely drop out until somewhere above 15-20 mph.

As per Jon's post above, delving deeper into the idle passages fixed MY problem.


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I have to correct my earlier “no” with a yes. I just spent some time reading how the Idle or Low Speed Circuit operates and that does seem to be the exact range I am having trouble with. This page is very informative giving me a better understanding of what I am looking at and what it is suppose to do. https://www.carburetor-blog.com/knowledge-base/w-1-low-speed/
Everyone’s comments are starting to make sense now.
-now that it is confirmed that the Idle/Low speed circuit is the issue.
-what do I try first
Thank you

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THIS IS WHAT i WOULD TRY FIRST.

A cheap, easy, and fast way to blow out the low speed jet and passages.

Remover air cleaner. Place #3 spark plug wire on # 4 spark plug and #4 wire on #3.

Start engine and tromp down gas pedal rapidly several times. The engine will back fire through the carburetor and blow out the dirt of the low speed jet and idle system.

If this does not work there is probably an assembly fault in the carburetor.


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Gene gives excellent advice above.

If that doesn't fix the problem, try removing the idle mixture screw and direct a very high pressure blast of air into the hole the screw came out of.

If that doesn't work, you will need to find someone who can remove the slotted plug, idle jet, and the copper plugs in the ends of the drilled passages.
As Jon said, at the very least the plug at the end of the upper cross-passage will need to be removed.
The passage(s) and economizer orifice will need to be cleaned using the PROPER gauge sized extended reach drill bits.
It is VERY important to know the proper size to use for the economizer orifice in your specific carburetor model, and not ream it oversize.

I had to go all the way with my carburetor.
I soaked and flushed with every kind of solvent I could think of, and directed air in both directions through the system.
Liquid and air flowed through the system, but reassembly and re installation gave the same poor results.

Only a small amount of reddish stuff came out of mine when running the drill bits through, but the effect of cleaning was dramatic.

Good luck.

PS
The link you provided for the explanation of how the idle system works is excellent, and gives almost exactly the same explanation the Carter literature gives.

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Originally Posted by Stovblt
I should have been more clear.
Sorry about that.
When I said idle screw, I was referring to the "idle mixture" screw.

Most old carburetor cores will still have the vacuum fitting in them. (the ones I have do)
Possibly you could contact one of the members nearer to you than I who rebuild Carter carburetors and ask if they will sell you one?

Otherwise, it's been a while since I had mine off, but isn't this the fitting you are looking for:

https://www.amazon.com/Generic-Brass-Compression-Connector-Fitting/dp/B00CHHYRT4/ref=sr_1_10?crid=1TAPDINKG4YE&keywords=brass%2Bfitting%2B1%2F8%2Bpipe%2Bcompression&qid=1665875594&sprefix=brass%2Bfitting%2B1%2F8%2Bpipe%2Bcompression%2Caps%2C117&sr=8-10&th=1

If at a hardware store, ask for a brass "1/8" male national pipe thread" to "1/8 OD tube" compression fitting.
I ordered the fitting from Amazon, thanks for the reference. I will of course keep everyone posted

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I own a 1936 Chevy Master coup that I inherited from my pop's earlier this year after sitting for 3 years. I was able to to get it to run after freshening it up and it ran ok with some idle issues but the biggest problem was at high speed 45-50 the engine would die out. Long story short I had the W1 rebuilt by Rod's carb in Glendale AZ where I live and all my issues resolved. I agree with the guy's above that there is some thing clogged and it need's a rebuild.

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I’m going to try the swapping #3 & 4 spark plug wires to blow out system. The carb is newly rebuilt so I can only assume it ingested sediment from the tank

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Please read back through this thread as well as my post from about a month ago. I would not necessarily assume it is dirt from the tank. In our case we are getting small rust particles from the float bowl itself.

I would also be cautious that assuming that because the carb was just “rebuilt” that everything was clean. If I remember correctly this carburetor has never idled properly on your engine. As noted by others who posted to your thread if the rebuilder did not remove all of the threaded and pressed-in plugs the passages might not have been properly cleaned.

The idle passage is very prone to blockage because it is so long and small in diameter.

Hopefully the #3 & #4 swap will work.


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So I tried the 3&4 swap, seems to idle a bit better but much black smoke coming from exhaust

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I’m actually starting to wonder if my timing is off with all of the messing around with stuff I’ve done. What sow the screw with the spring suppose to do, it seems to do nothing audibly noticeable?

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If screwing the the idle mixture screw in and out doesn't seem to be making much difference...

Your idle circuit is still at least partially plugged.


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The screw absolutely nothing and now there is black smoke coming from the exhaust which started since trying the 3&4 swap and Erving engine. Once the wires are correct she is now backfiring occasionally.

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I suggest that you need to send the carb back to your rebuilder.


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Sounds like I might have to do that. I wonder if I can repair my Rochesters leak in the mean time

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It probably would be good to start from the beginning of a tune-up and that is a compression test. Fuel and electrical items will not compensate for mechanical issues . Once you verify compression is good then you can diagnose further.


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Thanks all for the advice, turned out to be a defective rebuild. She runs great now but..
-ready to go for a spin and the brake pedal went to the floor. I checked the master cylinder and it was empty. After filing and pumping a few times I have a full pedal. Should I be concerned?
- Took her for a spin and decided to get gas not knowing how much is in her. Have been putting gas in her two gallons at a time until today. I might have put 3 gallons and gas started pouring from around the tank somewhere. Is it normal for gas to put out if the tank is full?
Thanks as usual
Michael
38 Master Sport(sport maybe?)

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Unless there is an unusual feature on your tank any overflow from over-filling the tank should come out the filler pipe.


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There are 2 standard openings in those tanks, the filler neck which may be a 2 piece with a rubber hose joiner and where the guage sender fits into the tank. Either 1 is a possibility or there is a rust hole somewhere.
Tony


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But the seller told me the tank is new, like I believe that. The gauge never worked properly, stuck at half a tank too. A hole was cut in the trunk floor so something was done in the tank area. Another mystery to unravel. Keep you posted.

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The tank could be new but that does not mean that the fuel sender was sealed properly. Or that the filler pipe is connected properly.


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