advice - how far do I take this?

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advice - how far do I take this?

Unread post by Going4joe » Wed Mar 08, 2017 3:15 pm

Hi all,

I posted here months ago about my 65 Monza 110 hp. Bought car for $500. It had a loud knock (cylinder #5) in the engine when I got it. I had a machinist/mechanic who is excellent at his craft, rebuild the motor. He found that one of the bearings spun and the Piston arm was damaged. New piston arm, new rings, replaced everything except the pistons, which seemed to be in excellent shape. New lifters. Machined the crankshaft as well as there was slight damage to it from the thrown bearing. Heads redone. New seals of course throughout. Got it all back together, fired it up. Knock still there - cylinder #5. After weeks of trying to figure this out, we took engine out and took it apart again and determined the crank was machined incorrectly. We sent it back to that machinist and he admitted he made a mistake. Crank redone again and sent back. Engine went back together. (rebuilt the two carbs as well). FIred car up. Knock still there, but it sounded different, like it was in the valve area. But it was still in cylinder #5. Car was running really rough despite the knock. I mean rough, like way worse than after we rebuilt the motor the first time. Car sat for a month while I pondered what to do. I finally took it to someone else. This guy told me the distributor was the cause of the rough running of the motor. He pulled that out, it came out in pieces!! Got a rebuilt one and installed it today. Car running rough still. This new mechanic put a vacuum guage on motor. He said the vacuum is all over the place. He thinks both carbs are shot - like they cant be rebuilt. The throttle bodies are just shot. He also thinks the noise from the motor is the camshaft hitting a lifter. I have done nothing with the cam - my first mechanic told me the cam was fine. WHO DO I BELIEVE HERE? I have over $4000 into this car motor and Im going nowhere - literally. Im sure some of you can relate to this tale of whoa... But this car needs a new interior, paint, chrome etc - I havent even touched that fun stuff yet!! Any thoughts?

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Re: advice - how far do I take this?

Unread post by County98 » Thu Mar 09, 2017 5:15 am

I don't know man. Crappy deal. Hope you get it worked out though.

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Re: advice - how far do I take this?

Unread post by Jerry Whitt » Thu Mar 09, 2017 10:55 am

You are experiencing a common issue. Lack of knowledge of older cars by the selected workers.


1. Go to your local junior college and sign up for an engine building class. The Corvair is pretty basic, and once knowledge is gained, you will feel good about doing your own work, and then be aware that some "experts" are not what they claim. The learning process is actually fun and you will meet some good people in class that will become friends for years.

2. Join a local Corvair group. Get to know the local Corvair people. Chances are excellent they will guide you to solutions to the problems you encounter
because they have already had similar issues. These folks will also become friends for years.
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Re: advice - how far do I take this?

Unread post by gnrand » Sun Mar 12, 2017 7:05 pm

Man I really feel for you. I wonder if the cam was reinstalled correctly after the block was separated. Also when the engine was disassembled, did you replace the lifters or use the old ones. If the old lifters were used, they should be installed on the same camshaft lob it was running on.
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Re: advice - how far do I take this?

Unread post by Scott Howey » Sun Mar 12, 2017 10:44 pm

Is the lifter stuck or collapsed cyl 5?

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Re: advice - how far do I take this?

Unread post by Going4joe » Sun Mar 19, 2017 3:37 pm

Thank you for your responses. I believe cam was installed correctly but this new mechanic who jumped in recently and said distributor was bad - now thinks cam is bad and yes I do have brand new lifters in there on a used cam. I found out this is a no - no. New lifters should be put in w a new cam. Apparently this could be causing the noiseImage

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Re: advice - how far do I take this?

Unread post by Going4joe » Sun Mar 19, 2017 3:39 pm

Scott - lifter is not stuck or collapsed in cyl 5. It's new. They are all new

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Re: advice - how far do I take this?

Unread post by notched » Sun Mar 19, 2017 3:56 pm

Did it spin the rod bearing again AFTER the initial rebuild? If so was it every determined what caused the rod bearing to spin in the first place? What were the clearances set to on the rods and mains during the rebuild? So of the Corvair blocks had machining issues in the grooves under the mains which could affect oiling to the rods. It pretty easy to see as sometimes the grooves are not lined up between the case halves or the grooves are not deep or wide enough.
Also as an FYI you must hook your vacuum gauge up to the vacuum crossover and not directly to the ports on the carburetors to get an accurate reading. Hooking to the carburetor ports will cause the gauge to bounce all over even on a perfectly running engine.
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Re: advice - how far do I take this?

Unread post by 64powerglide » Sun Mar 19, 2017 4:06 pm

Tell the guys why you say the knocking is coming from #5. Did you pull the # 5 spark plug & start the engine & still hear knocking?? Did you back off both rockers on # 5 until the valves didn't move & still hear knocking with the plug out??? Just grabbing at straws!!!!!! :doh:
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Re: advice - how far do I take this?

Unread post by my65 » Sat Apr 01, 2017 11:16 am

Well, since you have looked at all the items inside the motor that could be the source of the knock and can not confirm anything, I am going to take a long shot like 64powerglide and look outside! If there was something in the bell housing on the right side the was being contacted by the flywheel, it could give you a knock that sounds like it is coming from #5?? If you pull the motor back out to inspect / repair, run it first WITHOUT any of the power train components on ( flywheel, clutch, transaxle, and transmission)
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Re: advice - how far do I take this?

Unread post by 1966-Corsa-GT-180 » Sat Apr 22, 2017 8:37 am

That has got to be a heart breaker, as well as a wallet buster!
The "piston arm" is called a "rod"
I'd be a little upset that the mechanic that was first working on the spun bearing did not catch the improper machine-shop work while assembling the engine. That crank throw would require new oversize rod bearing shells and would need to be checked for clearance during assembly, which would lead to the discovery of improper machinist work.
Would have saved an lot of grief. Probably should have bought a known good original crank and used a stock piston/rod assembly
Now, the noise is seemingly out toward the head. Could be rocker arm. Could be the top rod/wrist pin - this requires a heat process installation to get the pin installed thru the rod & piston correctly - easy to damage the piston when doing this unless the work is done absolutely correctly. Why I advise using a stock assembled rod/piston assembly.
Some have successfully installed new lifters on an old cam with proper break-in procedures and lube and lotsa luck. Can be a problem but the noise would be heard deeper inside the case, I'd think.
Engine running rough. The distributor came out in pieces?? It's one assembly, that had been working, right? Was the gear off the shaft? Describe this in more detail, please.
Could be as simple as misrouted wires. getting two wires on #1 & #3 crossed will definitely cause a rough running engine! I've done it!
Where are you located? There are still Corvair mechanics doing great work on these engines, without the issues.
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Re: advice - how far do I take this?

Unread post by cnicol » Sun Apr 23, 2017 6:15 am

Another possibility: did anyone working on the engine mention that a cylinder head stud unscrewed when they disassembled the engine? There are a couple of them that can be installed "too deep" resulting in contact with a nearby connecting rod bolt. You can imagine the "bang bang bang" noise. It's actually possible to inspect externally by laying a good straightedge across all of the upper cylinder head studs. Someone with an open engine can tell you which ones are the critical ones that are open to the crankcase on the inside or I can post a photo late today or tomorrow. (I'm hosting a club event today so I'm pretty tied up)
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Re: advice - how far do I take this?

Unread post by lostboy » Sun Apr 23, 2017 6:32 am

Scott Howey wrote:Is the lifter stuck or collapsed cyl 5?
That was my guess and I had responded to the prior thread about it.

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Re: advice - how far do I take this?

Unread post by terribleted » Sun Apr 23, 2017 11:00 am

This engine was/is heavily discussed in another thread. The issue turned out to be poor rebuild work. A standard piston was installed in a +20 cylinder in #5 was one issue. The rings actually departed their groove and were wadded up under the piston. See this post viewtopic.php?f=55&t=12871
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Re: advice - how far do I take this?

Unread post by Going4joe » Sun Apr 23, 2017 3:56 pm

Thank you all for your great responses. I did start a new thread as mentioned and think I may have resolved the problem where my machinist mechanic failed to do so - in fact it seems he cut some pretty important corners when he put this motor back together that caused months of wasted downtime and the need to open this motor up 3 more times before we figured this out - the standard piston was in an over-sized jug that caused the piston slap. I'm in the process of putting it all back together (again) this week. I will keep you posted as to how it goes Image

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