……
Corvair DiagramCorvair Photo
Corvair Center
home forum corvairs calendar links Corvair Podcast
California Corvairs
Clarks Corvair
Clarks Corvair
“CORSA"



Chevy Corvair License Plate
Chevy Corvair Chrome Wheel
Corvair Center Forum :  Corvair Center Phorum - presented by CORSA The fastest message board... ever.
Corvair Center 
Pages: Previous12
Current Page: 2 of 2
Re: Rough idle with popping sound?
Posted by: Winsamfarm ()
Date: January 21, 2023 06:04PM

Hi Folks. I have found the source of my problem. Just got in from compression testing (not the easiest getting the fitting down there with all the carb linkages) and have zero compression on #2. Put compressed air into the cylinder and it came up through the carb throat, so one very stuck intake valve. Just hope the stem hasn't been bent from hitting the top of the piston. What clearance is there between the valve and piston at the top of the stroke.
I was able to do this while the car is up on the hoist waiting for new gearbox mounts and had a trailer pushed under with a ladder.
I also appreciate advice on here. Steve c Goodman made it easy for me to turn the engine over while standing over watching the gauge. Thank you for that. I wasn't looking forward to going back and forth and I work on my own.

Options: ReplyQuote
Re: Rough idle with popping sound?
Posted by: JimBrandberg ()
Date: January 22, 2023 07:03AM

It could be the #2 Intake adjustment is to tight. Maybe a bad valve seat. It could be a valve stuck in the guide but chances are slim.
First step is to remove the valve cover and investigate. With the distributor pointing at #2 and the harmonic balancer at TDC see the attitude of the valve compared to the exhaust, they should both be closed.
If closed see how many 1/4 turns you loosen to get to zero lash.
If you think the valve is stuck you can rap on the tip to see if it will spring closed.
Valve seat issues have several stages of severity.

Jim Brandberg
Isanti, MN
CorvairRepair.com



Options: ReplyQuote
Re: Rough idle with popping sound?
Posted by: RexJohnson ()
Date: January 22, 2023 10:10AM

Defiantly back off the intake valve a couple of turns and then put air in the cylinder again to see if things changed.

RJ tools
Salem,Oregon

Options: ReplyQuote
Re: Rough idle with popping sound?
Posted by: Winsamfarm ()
Date: January 22, 2023 09:31PM

Dropped the head out today and found the exhaust valve seat has dropped out. So off to the engine rebuilders to see if he can repair with parts available here in NZ. Interesting there is a couple of valve imprints in the top of the piston from both valves. The seat has whacked into the head gasket and damaged that.

Options: ReplyQuote
Re: Rough idle with popping sound?
Posted by: American Mel ()
Date: January 22, 2023 09:38PM

Try to find some "Deep Seats" for that.

-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
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.

Options: ReplyQuote
Re: Rough idle with popping sound?
Posted by: JimBrandberg ()
Date: January 23, 2023 04:48AM

Around here someone might try to find a different used head.
If the exhaust valve is the main culprit I wonder how or why you had pressure coming up through the intake as well.
I wonder why the intake valve was hitting the piston too. I suppose the possibilities are that it was sticking in the guide or that the intake seat had come out and rattled around a while before going back in.

Jim Brandberg
Isanti, MN
CorvairRepair.com



Options: ReplyQuote
Re: Rough idle with popping sound?
Posted by: Winsamfarm ()
Date: January 23, 2023 12:42PM

My guess would be as I was turning the engine to try to get a compression reading, it was when the intake valve was opening that I could hear and feel the air up the carb. At that stage the muffler was attached so I didn't hear it coming from the exhaust.

Options: ReplyQuote
Re: Rough idle with popping sound?
Posted by: jjohnsonjo ()
Date: January 23, 2023 01:39PM

There is a chance both seats came out and one went back in

J.O.

65 Corsa Turbo Vert
79 Honda XL 500S
69 Honda CL 160 D
2010 BMW F 650 GS
2003 Bounder 36D
2013 KIA Optima SX turbo-AKA ZIPPY (wife,s car)
69 Newport Holiday Sailboat
Baja 150 dune buggy cart
Coleman HS 500 UTV
2016 KIA Sorento SXL Turbo

Bethlehem,Pa


Options: ReplyQuote
Re: Rough idle with popping sound?
Posted by: RobertC ()
Date: January 29, 2023 12:08AM

My valve seat failures have been intakes.

Think ALL the valve seats need to be replaced in your head.

Or, source a rebuilt head here in the US. Or, two? As your other head is probably not in better shape.

How many miles have you put on the car? You have had it for a year?

Options: ReplyQuote
Re: Rough idle with popping sound?
Posted by: Winsamfarm ()
Date: January 29, 2023 12:17PM

I would be doing all the valves once I hear back from the rebuilder. I will be seeing him tomorrow. There is a set of rebuilt 140 heads on Ebay which I am watching and will have to make a decision once I know about this one.

I bought the car a year ago sight unseen because of 'those' travel restrictions. The engine has clearly been worked on, but to what extent I do not know. I am glad I received the suggestion on this forum of compression testing because that immediately identified the bad cylinder.

Other than starting every now and then to circulate the oil, I have not driven it except for around our lot. It has 91K miles on it.

It has previously been in a left front fender bender and the repair has been 'so so'. There is a small dent in the front chassis rail which the inspectors here picked up on. This has to be rectified before I can register it for the road. In the meantime I am sorting the few other items that I could see needed attending to, ironically not picked up by the inspectors. Like replacing the rear strut bushings that had been completely chewed out.

Options: ReplyQuote
Pages: Previous12
Current Page: 2 of 2


Sorry, only registered users may post in this forum.
This forum powered by Phorum.