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140 Jetting?
Posted by: F4UCorsair45 ()
Date: March 30, 2021 10:02AM

I have a question for other Corvair owners out there. I have a 1965 140 with a four speed. It was down in Los Angeles til about 4 years ago and then was brought up here and never worked on. I bought it and started to restore it about a year back.

I've noticed that it struggles to start without pumping the throttle (more than you should in a carburated car). I don't know if it is a quirk of the Corvair to need that much pumping on startup or something but i was thinking it has jetting that is too small for my elevation and setup. I have headers from Clarks on it which opens it up a lot more, It also has individual air cleaners instead of the center mount. it is still running the stock 140 cam. My thought is that now its more unrestricted (especially the exhaust) and because of that it needs bigger jets to run at full efficiency.

The exhaust is unfinished so take that with a grain of salt. The car still needs work but it does take a lot to start especially in temperatures under about 50. I imagine it is still jetted for sea level and not 5000 feet like my place here in Utah.

I am young and still learning, most of my experience with carburated vehicles has been with motorcycles which from my understanding are a lot more temperamental with jetting than cars so i could just be overthinking this. but my question to you all is what would you do in this situation. should I get larger jets to compensate for the free flowing exhaust and intake. or is there something else that is causing this. another thought is that it could be a vacuum leak. I know my secondarys leak most of the time I've tried to fix it with springs on my secondary throttles, and adjusting the butterfly which drastically helped but there is still a chance.

All help is appreciated, Im just a dumb 16 year old so thank you all for your kind advise.

McLayne B,
Genola Utah 84655
1965 Corvair 140, 4 speed, 3.27 final drive with posi.
High school project car/daily driver

All tips and help are greatly appreciated

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Re: 140 Jetting?
Posted by: Spectre ()
Date: March 30, 2021 10:24AM

Is it hard to start at that temperature every time or just when it sits a couple of days? Today's fuels seem to evaporate from the carb bowls faster and after a day or two, it takes a bit for the bowls to refill when cranking. I ditched the stock pump and went electric. I turn the key on, listen for the pump to get quiet, then crank it.

David Clamp


1965 Corsa convertible - 140 4spd/3.55/AM-FM

2013 Mustang GT convertible - 5.0, 6spd auto, Procharger i-1

2003 Miata SE - 6spd manual (wife's toy)

"Victory is mine!" - SG

Norman, OK

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Re: 140 Jetting?
Posted by: MattNall ()
Date: March 30, 2021 10:25AM

Accelerator pumps and fully closed chokes?? If this is after setting for a week...it's today's gasolines... they evap quicker

MODERATOR
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Re: 140 Jetting?
Posted by: RexJohnson ()
Date: March 30, 2021 10:27AM

By taking the car to 5,000 feet elevation from sea level you made the mixture richer. Less oxygen at 5,000 feet. What are your chocks doing? If they are not closing all of the way then it might take alot of pumping of the throttle. Are the accelerator pumps working? That is a common problem with the Corvair carbs so that could be why you have to pump the pedal more than normal especially if the chocks aren't closing all the way. You don't need the accelerator pumps if the chocks work properly but if the chocks don't work you need good accelerator pumps.

RJ tools
Salem,Oregon

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Re: 140 Jetting?
Posted by: gbullman ()
Date: March 30, 2021 12:01PM

Yeah, before diving into changing jets verify your chokes are working properly. That means that the bimetallic coils are still moving pushing the rods up when cold and opening when the engine gets warm.

I'm coming off 2 older cars that started with less pumps than my Corvair so would agree they like a few more squirts than others I've owned. When cold (sitting a day or more) and temps around 50 or below I have to pump twice, it fires but doesn't start, pump 2 more time, runs for a few seconds then pump a couple more times where it runs long enough I can goose the pedal a little bit and keep it running, usually about 10 seconds of that and it idles


Gary
1966 Corsa Convertible
Northern New Jersey


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Re: 140 Jetting?
Posted by: F4UCorsair45 ()
Date: March 30, 2021 12:03PM

It usually is after it sits for a few days. I don't start it every day. I have an electric pump and it does tend to start better after it has pumped for a minute. I still worry that it is too lean though because even after startup it tends to want to die and you have to keep pumping the throttle to keep it running. after holding it for about a 30 seconds to a minute you can take your foot off and it runs albeit choppy. its just the cold starting and idling that are harsh. It may be my chokes not sealing/adjusted right. one of my secondary accelerator pumps was a bit malformed when i put it in a few months ago but that wouldn't effect startup because those carbs aren't engaged yet?

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Re: 140 Jetting?
Posted by: RobertC ()
Date: March 30, 2021 12:10PM

Well, a lot of things to check:

Primaries: what are the chokes set at - cold before you start the engine. The setting is in the 65 shop manual - approx 1/8" between blade of choke lever and side of carb.

What linkage do you have? Early 65 ("big" arm with a long slot?) or late 65 / 66? Instructions for setting up the early 65 will be in the 65 shop manual. Instructions for the late 65 / 66 is in the 66 shop manual supplement.

Secondary butterflies should be closed until activated by linkage. The secondaries have a stronger accelerator pump return spring to accomplish this. You should not need extra springs.

The lever on the throttle shaft can come loose over time. Need to check that they are tight on the shaft.

If the car sits for a few weeks, the current gas can evaporate out for the carbs and you have to fill them back up.

Jets: you can try 51(primary / 50 secondary (stock) or even 52/51. Since Steve Goodman lives in Denver, he should have a much better idea of the correct jets than I do.

But, the jets do not have anything to do with your starting problem.

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Re: 140 Jetting?
Posted by: F4UCorsair45 ()
Date: March 30, 2021 12:10PM

for me it is like waiting for the pump to get fuel into the floatbowls. then pumping about 10 times. It pops and bucks like it wants to start. then another few pumps and it runs really choppy. then i have to keep pumping to keep it somewhat idling. after it starts running on all cylinders then i can run about an 1/8 throttle (around 1100 rpms) give or take a few i dont have a tach hooked up so thats just from my butt dyno. after about a minute of doing that it finally idles.

How do you set the chokes correctly

McLayne B,
Genola Utah 84655
1965 Corvair 140, 4 speed, 3.27 final drive with posi.
High school project car/daily driver

All tips and help are greatly appreciated

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Re: 140 Jetting?
Posted by: F4UCorsair45 ()
Date: March 30, 2021 12:14PM

my linkage was a 65 but i bought the roger parent linkage for the 65s that has the bearings and bushings instead of the slots and stuff that the original ones did. this linkage is set to his specification.

McLayne B,
Genola Utah 84655
1965 Corvair 140, 4 speed, 3.27 final drive with posi.
High school project car/daily driver

All tips and help are greatly appreciated

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Re: 140 Jetting?
Posted by: Spectre ()
Date: March 30, 2021 12:17PM

Main jets should not impact starting ability. Double check that the chokes are set correctly. Letting the bowls fill first is a good idea since the engine won't run without fuel.

David Clamp


1965 Corsa convertible - 140 4spd/3.55/AM-FM

2013 Mustang GT convertible - 5.0, 6spd auto, Procharger i-1

2003 Miata SE - 6spd manual (wife's toy)

"Victory is mine!" - SG

Norman, OK

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Re: 140 Jetting?
Posted by: joelsplace ()
Date: March 30, 2021 12:36PM

McLayne,
It sounds like your chokes aren't working at all. The correct way to set them is to use the procedure in the shop manual or even better use Bob's book. A quick and dirty way to get them closer is to pull the air cleaners off with a cold engine and open the throttle about half way and then let off. That will allow the chokes to close as much as they want to. Look to see if they are fully closed. If they aren't adjust the threaded rods that come out of the heads and attach to the chokes until they are just closed. That should improve things a lot until you have time to go through the whole procedure.

Joel
Northlake, TX
5 Ultravans, 116 Corvairs and counting...

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Re: 140 Jetting?
Posted by: 66vairman ()
Date: March 30, 2021 05:16PM

The stock jets should be fine at 5,000 ft. The problem may be worn out carburetor accelerator cups. Even with the chokes inactivated if you "pump the pedal enough" on a cold engine it will usually start.

I have an electric fuel pump. After the car sits a few days you can hear fuel filling the bowls - NORMAL now. No lead gasoline meant changing the refining process to increase octane. It makes gasoline more volatile (evaporates fast).

After sitting a few days, I'd turn on the key to run the fuel pump a few seconds, pump the accelerator a couple times to get the carburetor accelerator pumps to prime the carburetors and the engine started immediately.

Then after a few years it took MORE pumping of the accelerator pedal, then even that did not work (even with the chokes closed). I found the accelerator pumps had quit!!

I rebuilt the carburetors with the new Viton accelerator pump cups and once again it started right up after sitting a few days with only a couple pumps of the accelerator pedal. Clark's doesn't have the Viton cups yet. I got them from Jeff at Calif. Corvair. If needed you can replace the accelerator pump assembly with the Viton cup if needed.

BTW -- Once the engine is warmed up it should start up by depressing the pedal while the starter is engaged without pumping the pedal during warm weather.

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Re: 140 Jetting?
Posted by: F4UCorsair45 ()
Date: March 30, 2021 07:04PM

i believe it was the chokes being not adjusted correctly. I came home and adjusted them to the 1/8th inch like you all said. I also ran the pump for a second and it started just fine. Ill keep up with this but I think we got the problem fixed. thank you all.

McLayne B,
Genola Utah 84655
1965 Corvair 140, 4 speed, 3.27 final drive with posi.
High school project car/daily driver

All tips and help are greatly appreciated

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Re: 140 Jetting?
Posted by: Alberto ()
Date: March 31, 2021 09:51AM

I had the same problems starting my 140 cold after it had been sitting for a week or 2.

I put new chokes on both sides and then put a flow-thru electric fuel pump with a push button switch (must continue to press to keep 'on'). I run the electric pump about 10~15 seconds before trying to start.

Doing these 2 things (and retarding the timing to 15 BTC) has cured the problem.

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