6 cyl Idle speed? - Chevy Nova Forum
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Old 11th-December-2009, 11:05 AM   #1
Rotorbolt

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6 cyl Idle speed?

I recently got my 194 6 cyl running. My shop manual says the idle sped is set at 500 rpm in drive. But what is the idle speed in park? Mine is running at least 1000-1200. Is this the normal range for a 6 cyl? That seems too high to me. If I adjust the speed down from this, then it idles rough in gear at around 300-400 rpm. Idles in gear fine at 500. I'd like to get the idle speed in park down to 800 rpms. This is my 1st 6cyl build and I'm not totally familiar with how they should run. I'm more used to V8s, so I'm learning here. I have the timming set a 4 degrees and idle set a 500 in drive like my manual specifies. The engine is stock internally. The only upgrades are the HEI and the dual holley 1bbl setup on it. It has a TH350 automatic. My guess is that I still have to mess with the fuel mixture screws on the carbs. The vaccum advance is working and the trans modualtor seems fine. Could the stall speed of the converter be too low since it was from a V8?
I'm thinking its the carburators. Too much carburation for an engine this size maybe?
I did, however, get to drive the car around the block a couple times last night. First time I drove it in over a year and half. I didn't get down on it, but it seemed to drive alright.
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Old 15th-December-2009, 11:51 AM   #2
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I doubt your problem is too much carb, but depending on what they came off of you may need to readjust or rejet them. Check the plugs and go from there. Also check for vacuum leaks around the carbs and intake as that could affect your idle speed. Also you need to make sure the carbs are adjusted the same. Since the car sat for so long, it might be a good idea to put fresh fuel in it. Bad fuel could make a huge difference in the way it runs. 4 degrees btdc with the advance plugged should be correct, but you can play with the timing a couple of degrees at a time to see if it makes a difference. Depending on the year, some 194s spec'd at 8 degrees.

A basically stock 194 should not idle as high as yours. Probably the 600-700 range would be appropriate. The converter may be part of the problem depending on what it came from; it likely will stall lower due to the lower torque of the 194.
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Old 15th-December-2009, 12:50 PM   #3
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I've messed with it some more as time permits. It is really hard to start when it is cold after it has set overnight. It gets fuel, but acts like it is flooded. Once I finnally get it started, it runs rough for a couple mins and then smoothes out. My theory is the gas thats in it is bad. I got in such an excited hurry, that I forgot how old the fuel that was in it was. It maybe had a couple gallons in the tank when I parked it to build the car. That was a little over a year and half ago. I later put a gallon of "fresher" fuel in it that was left in the lawn mower gas container maybe a couple months. That was more than likely a summer blend fuel as well. It ran better somewhat, but the fuel still stinks. I then had to adjust the valves again since one of them statred tickking. Also, I discovered that one of the carb's accelerator pumps isn't working efficently along with some wetness around some of the gaskets on the body. I'm also thinking the carbs are leaking down overnight. I'm going to have to get the numbers off the carbs and get some rebuild kits for them. If I find the kits, then i'll know what they originally were equiped on.
Once the engine warms up, it runs a lot better and starts up easy.

My plan ( budget wise ) is to rebuild the carbs, put some fresh winter blend fuel in it, and figure out a manual choke. I also need to get that "uni syn" carb syncronizing tool from Speedway so I can get the carbs flowing equally.

I'm very tempted right now to just bite the bullet and order a couple of new holley/webber progressive carbs with electric cokes, base adapters and linkage from Langdons Stovebolt and be done with this so I can drive it.

That or rebuild my current "auxillary" backup holley/webber 2bbl and change back over to my stock intake and figure out a throttle cable setup, if i can't get this setup to work like I want.

The transmission came out of a customer's 55 Chevy. He switched over to a 700R4 overdrive and I got the TH350 from him in a trade deal. It was behind a 350 V8 and I was told the converter had a higher stall to it ( unknown) due to the cam that was in the engine.

Last edited by Rotorbolt; 15th-December-2009 at 12:58 PM.
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Old 15th-December-2009, 01:07 PM   #4
tony
 
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Good advice from Bruce above......

On the converter: I have used a TCI Saturday Night Special in back of a mild 230 with a Holley 390 cfm with no issues whatsover....(this is a 16-1800 RPM stall SBC converter)

I would lean much more toward your carbs & their adjustments....

Also - Sometimes overlooked is the throttle linkage itself..... Is this adjusted so as that BOTH carb throttle shafts are completely down to the same idle postion ???
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Old 15th-December-2009, 04:02 PM   #5
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I have my idle speed set faster than normal, but that's due to the camshaft I put in it
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Old 18th-December-2009, 09:32 AM   #6
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I removed the two carbs yesterday to try and find all the numbers one them so I can get some rebuild kits. After I took them off, I noticed a good ammount of fuel puddling in the intake. Which means they were leaking down as I suspected.
I went to my local O'reiley's auto parts to try and find the kits. Looked through their books real quick with no immediate luck. There sure were a lot of part numbers just for Holleys. The store manager was kind enough to give me the carb parts book since they were updating their parts catalogs anyway. After much study and looking through it at home, I finally found out what kind of carbs I have.
What I have are old school Holley aftermarket replacement 1bbl carburators model# 1940 ( VERY small number on the carb! ). These were used to replace the factory carbs on various 6 cylinders. Everything from Ford, Chevy, Checker, AMC, Internatonal from 1962-1976.
My kits should be in today, as I had to order them. Hopefully, I'll get to rebuild them later and get this thing running right.
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Old 29th-December-2009, 03:38 PM   #7
Rotorbolt

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OK, I finally got both carbs rebuilt and reinstalled. I put some fresh gas in it and the engine fired right up and ran a whole lot better. I let it sit for a couple days and started it up with no problems.
I also took the time to engineer and fabricate a manual choke system that works correctly now for both carbs. I also had to make a new return spring bracket, tweek on the linkage and change the fuel lines.
Still need to adjust on the mixture screws and idle screws to tune it in some more. But other than that, it seems to work alright.
Thanks guys.

Last edited by Rotorbolt; 29th-December-2009 at 03:42 PM.
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