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Trouble with Idle
Posted by: Nick_Soapdish ()
Date: September 10, 2018 08:00PM

Like the title says, I'm having trouble getting my (just rebuilt) engine to idle. It runs good with some throttle, but wants to stumble and die at lower RPMs. It'll stay running if you dial in a higher "idle," but it will still fall on its face once the Rs drop back down after a small rev.

I didn't find any vacuum leaks (doesn't mean there aren't any) and am using the same carbs that were on it when it ran (and idled) before. Timing is about 8 btdc and I've tried a few degrees in each direction with no major difference.

Any thoughts on this? Sound familiar to anyone? As always, thanks in advance for the insight.

Dylan
'62 95 Panel
Seattle, WA

Wagons and vans, just clap your hands.

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Re: Trouble with Idle
Posted by: TahoeRon ()
Date: September 10, 2018 08:12PM

Most likely the carbs are not adjusted correctly after reassembly. There is a specific sequence you should go through, and you should use a vacuum gauge or an air flow measuring device to get everything synced.

I was surprised how much smoother my engine idled after I got everything set up properly.
=====
Ron

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Re: Trouble with Idle
Posted by: MattNall ()
Date: September 10, 2018 08:59PM

Dylan, if yopu didn't messwith the carbs since you took them off the engine....

Valve adjustment!

Take a compression test to know





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Re: Trouble with Idle
Posted by: BobV66Vair ()
Date: September 11, 2018 09:52AM

Unisync the carbs, adjust mixing screws. Just sitting can change the carbs setup. New engine is drawing different vacuum than the old one. Maybe valve adjustment but that seems more like a problem that would have more symptoms. experts will tell us both. I found a good starting and idle with good power at 14 degrees BTDC. Make sure dwell is good too.

Bob Vinnacombe
Sandy, Oregon
1965 Corsa 140 stock
1966 Monza Soon to be race car
1968 Monza Parts for now

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Re: Trouble with Idle
Posted by: TerribleTed ()
Date: September 11, 2018 08:40PM

I bet on some valves adjusted a bit tight.

---------------------------------------------------------------------------------------------------------

Avid Corvair hobbiest since 1984.
I have personally performed ground up restoration on over 20 Corvairs.
I currently work full time at restoring and repairing Corvairs.
Located in the Atlanta Georgia area.
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Re: Trouble with Idle
Posted by: Nick_Soapdish ()
Date: September 12, 2018 07:24PM

MattNall Wrote:
-------------------------------------------------------
> Valve adjustment!
>
> Take a compression test to know

TerribleTed Wrote:
-------------------------------------------------------
> I bet on some valves adjusted a bit tight.


This is what I was leaning toward too. Never thought I would hope for low compression numbers. But:

#1 - 150
#2 - 145
#3 - 145
#4 - 135
#5 - 150
#6 - 158

So...crap. Back to carbs, I guess.

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Re: Trouble with Idle
Posted by: Lane66m ()
Date: September 12, 2018 07:54PM

Your left side compression is 145, 135, 158. Sounds like something not right there, why the high number or why the low number. The 135 seems low.

Just curious.

Al Lane
Ellabell GA

1966 Monza Coupe, 110 hp, 4 Spd
1968 Camaro SS Coupe 350 CI 295+ HP PG
1964 Greenbrier Deluxe, 6 dr, 80 hp car engine, PG
2015 Chevrolet Malibu 2LT
2018 Chevrolet Silverado LTZ Z71 Centennial Edition
1947 Farmall A tractor 15 hp


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Re: Trouble with Idle
Posted by: TerribleTed ()
Date: September 13, 2018 08:26AM

Some valves could still be a little tight. I would do a running adjustment to see if the situation changes. Compression test at starting rpms and actual compression engine running may vary. If a valve is on the verge of holding open during compression test it may indeed hold open a bit when running which will cause roughness and stalling.

---------------------------------------------------------------------------------------------------------

Avid Corvair hobbiest since 1984.
I have personally performed ground up restoration on over 20 Corvairs.
I currently work full time at restoring and repairing Corvairs.
Located in the Atlanta Georgia area.
[www.facebook.com]

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