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Rough idle with popping sound?
Posted by: Winsamfarm ()
Date: January 14, 2023 01:28PM

On the subject of uneven idling. I have a 66 Monza Convertible with the 140 hp.
When idling, my left bank runs unevenly as can be evidenced by the 'popping sound through the exhaust. When I put the vacuum meter on, the poppet ball pops up and down whereas on the right side it is smooth in the center of the gauge.
I bought the car a year ago from Beverly Hills Car Club and it appears to be a new rebuild of the engine. Is it possibly a mal adjusted tappet causing the unsteady left bank.
The car is now in New Zealand.



Edited 1 time(s). Last edit at 01/14/2023 07:03PM by American Mel.

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Re: Engine Shakes and Sounds Terrible on my 1960 coupe
Posted by: American Mel ()
Date: January 14, 2023 04:23PM

Winsamfarm Wrote:
-------------------------------------------------------
> On the subject of uneven idling. I have a 66 Monza Convertible with the 140 hp.
> When idling, my left bank runs unevenly as can be evidenced by the 'popping sound through the exhaust. When I put the vacuum meter on, the poppet ball pops up and down whereas on the right side it is smooth in the center of the gauge.
> I bought the car a year ago from Beverly Hills Car Club and it appears to be a new rebuild of the engine. Is it possibly a mal adjusted tappet causing the unsteady left bank.
> The car is now in New Zealand.


Sounds like a "Lean Miss" to me.
That left side carb needs attention.
Could need a total carb rebuild, OR something as simple as the Ole Hand Over The Carb Mouth While Idling trick.
Can't really say form halfway around the world.

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WA. state, 1 mile south of the Canadian border, I am not at the end of the world, but you can see it from here.

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Re: Engine Shakes and Sounds Terrible on my 1960 coupe
Posted by: Winsamfarm ()
Date: January 14, 2023 05:47PM

It is the 140 engine with 4 carbs. I thought it might be the carb so bought a rebuilt one from Clark's. No difference.

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Re: Engine Shakes and Sounds Terrible on my 1960 coupe
Posted by: American Mel ()
Date: January 14, 2023 05:58PM

140, two carbs per side.
Which one did you replace?
.
In answer to your original question, yes, it is possible, but if adjusted correctly, it is unlikely that a lifter is your problem.
The Hydraulic Lifters are a Set and Forget item.
Unless one has a failure, they don't normally need readjusting.
.
Have you done a Compression test on the car?

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WA. state, 1 mile south of the Canadian border, I am not at the end of the world, but you can see it from here.

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Re: Engine Shakes and Sounds Terrible on my 1960 coupe
Posted by: Winsamfarm ()
Date: January 14, 2023 06:21PM

I replaced the primary carb on the left side, the side that is uneven.
No I haven't done a compression test. Certainly something I should do. I did check that all the distributor leads were correctly fitted.

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Re: Rough idle with popping sound?
Posted by: wittsend ()
Date: January 14, 2023 08:04PM

Perhaps a valve is hanging up in the guide, is burnt or the seat has come loose. The vacuum meter fluctuation (carburetor synchronization tool) is likely seeing pressure than vacuum intermittently.

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

***'61 Lakewood, a "Freebie" in hibernation for 27 years - In the process of applying CPR.***

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Re: Rough idle with popping sound?
Posted by: American Mel ()
Date: January 14, 2023 08:29PM

That was what I was thinking.
Why the compression question.
I didn't explain it, because I just didn't want to add a bunch of distracting thoughts into the process prematurely.

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WA. state, 1 mile south of the Canadian border, I am not at the end of the world, but you can see it from here.

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Re: Rough idle with popping sound?
Posted by: JimBrandberg ()
Date: January 15, 2023 06:04AM

It doesn't cost much to run through the lifter adjustment just to be sure. You can burn a valve running it too tight. I usually adjust them not running one cylinder at a time unless I have some trouble that warrants going through them with the engine running.
I'm not a fan of doing half of them when #1 fires and the other half when #2 fires. I'm sure it's a valid process, it's just not for me.

Jim Brandberg
Isanti, MN
CorvairRepair.com



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Re: Rough idle with popping sound?
Posted by: wittsend ()
Date: January 15, 2023 10:05AM

I realize this would not be the case for the original posters (assembled) engine... .
However, when I assembled my engine I left the top cover off as long as I could and with a flash light visually confirmed that the lifter was off the cam ramp when I adjusted the lifters. Just another means of double checking. It also allowed me with an extended brush to re-coat the cam lobes with assembly lube after the cam rotates. As I have noted with many of Jim 's posts he too seems to take the "ounce of prevention is worth a pound of cure" approach. Better to be "safe than sorry."

If the original poster finds a loose rocker and is doing a cold, non-running adjustment, I, like so many others have, recommend the .001 feeler gauge adjustment method. It takes a lot of the vagary out of knowing when the lash is at (well, very near) zero.

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

***'61 Lakewood, a "Freebie" in hibernation for 27 years - In the process of applying CPR.***

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Re: Rough idle with popping sound?
Posted by: Frank DuVal ()
Date: January 15, 2023 07:01PM

Lean maybe? Then make sure the secondary carburetor on the left side is closing fully.winking smiley

Frank DuVal

Fredericksburg, VA

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Re: Rough idle with popping sound?
Posted by: TIBCO ()
Date: January 16, 2023 08:18AM

To add to what Frank just said, I would block off the secondary entirely until I was certain the primary carburetor is working fine. It only takes a thin piece of metal and a few minutes to do. Then you can concentrate all your attention on the primary carburetor.

Cliff Tibbitts
Nicholasville, KY
CORSA, CKCE, Derby City Corvairs
66 Monza, 140/4sp

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Re: Rough idle with popping sound?
Posted by: Winsamfarm ()
Date: January 19, 2023 11:56AM

Good morning all from mid summer New Zealand. I am slowly working my way into diagnosing this rough idle and think I may have found an issue. Bought a compression tester and I will get to use it once the car is back on the ground from the hoist. But in the meantime from a ladder on the back of a trailer pushed under the rear of the car, on removing the plug leads, number 4 the lead came out without the fitting and grommet. So odds on that there was very poor contact with the plug. Then on removing the plugs, on the right bank there were NGK Iridium BR7HIX installed. On the left bank there were NGK BP6HS installed. On reading the literature for both these plugs it appears they have different firing characteristics and the BP6HS has an extended probe. I have 3 NGK Iridium BR7HIX on their way to me now from a local retailer. Don't choke when you hear the prices. I got them for NZ$16.80 each on sale. Normally NZ$55 each.

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Re: Rough idle with popping sound?
Posted by: RobertC ()
Date: January 19, 2023 02:17PM

Unfortunately, neither BP6HS nor BR7HIX is listed for Corvair (Rockauto)

People here (not me) use NGK BR6HS (now NGK 3922)

Rockauto lists the Corvair iridium plug as NGK 3419

As near as I can tell; the BR7HIX is a colder plug than a BR6* plug. This may not work well with a Corvair engine - just my speculation.

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Re: Rough idle with popping sound?
Posted by: joelsplace ()
Date: January 20, 2023 12:12AM

If you aren't burning oil and your carburetors are dialed in you shouldn't have an issue with the 7 heat range.
The P in the part number means extended tip.
H is the length and B is the thread size. S is something silly like "Super". I think it just means a basic copper core plug.
R is resistor.

Joel
Northlake, TX
5 Ultravans, 141 Corvairs and counting...

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Re: Rough idle with popping sound?
Posted by: steve c goodman ()
Date: January 20, 2023 06:05AM

Winsamfarm did you block secondary carb by making gasket to be placed under the carb?

best wishes, Steve
Rear Engine Spec. Inc. Golden, Colo.

1962 spyder 3.0L turbo---1965 Crown V8
1967 monza 110/4---1968 monza 110/4
1971 amante gt 110/4
CORSA/RMC/PPCC/V8 Registry

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Re: Rough idle with popping sound?
Posted by: RobertC ()
Date: January 20, 2023 10:21AM

Before going to the trouble to make block off plates, first closely inspect that secondary.

Is the linkage "tight" / no play? Is the throttle plate completely closed?

May want to remove carb to check - use a flashlight in a dark room.

Very slim chance someone installed the throttle plate upside down. Plate is beveled and will not completely close, if so.

But, still, someone could have reinstalled the plate slightly off center and it will bind and not completely close, also.

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Re: Rough idle with popping sound?
Posted by: RobertC ()
Date: January 20, 2023 05:38PM

Another item to check is the balance tube.

It is connected to the base of each carb bank - usually a rubber hose.

"Back" of engine compartment - towards the front of the car.

I use a 3/8" compression union - might be hard (expensive) to find / get in New Zealand.

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Re: Rough idle with popping sound?
Posted by: Frank DuVal ()
Date: January 21, 2023 04:41PM

Tight fitting 3/8" rubber hose will work, just have to check now and then to make sure it still fits tight. Some 3/8" hose fits looser than others. Compression fitting is more install and forget, I have yet to bother with them.winking smiley

Frank DuVal

Fredericksburg, VA

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Re: Rough idle with popping sound?
Posted by: American Mel ()
Date: January 21, 2023 04:47PM

Simple hose clamps installed on your rubber hose will work also. winking smiley

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WA. state, 1 mile south of the Canadian border, I am not at the end of the world, but you can see it from here.

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Re: Rough idle with popping sound?
Posted by: RexJohnson ()
Date: January 21, 2023 05:29PM

Auto trans cooler hose seems to work good. I think that it is slightly smaller than the 3/8" fuel hose with a heavy wall thickness.

RJ tools
Salem,Oregon

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