Air Head - Not Sure How to Title This One

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plmbcrzy
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Air Head - Not Sure How to Title This One

Post by plmbcrzy »

Was determining pushrod length today and when I pressurized the cylinder with air to hold the valves open while I installed the check Springs I think they're called I noticed leakage out the exhaust tube called my machine assist he said bring them back and he went through and resurface the seats and lapped them all did a fine job both heads 140 if that makes any difference I came home put everything all back together got my pushrod length and said let me check again and I had the same problem so I put the head on that I hadn't used so far and had the same results as far as leakage I believe my Machinist to be highly qualified and his abilities therefore I'm wondering is there something I'm not thinking about causing this problem I'm using approximately a hundred hundred twenty pounds of air I bought the valves with the mallet the soft kind so I didn't do any damage and it didn't seem to make any difference I held my hand over the intake just for s**** and giggles and it was leaking there as well both heads same thing leads me to believe that it's not the machine work what could be causing this before I call him and say what the hell is going on
Thanks again
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plmbcrzy
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Re: Air Head - Not Sure How to Title This One

Post by plmbcrzy »

Sorry about the typos and lack of punctuation

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Jerry Whitt
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Re: Air Head - Not Sure How to Title This One

Post by Jerry Whitt »

Your terminology is fouled up. Air pressure is put into a spark plug hole to hold the valves closed, not hold them open.

If you are using mostly stock heads and rocker arms, with hydraulic lifters, the standard length push rods will work fine.

If you are using some exotic heads and valves, tell us what you have.
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plmbcrzy
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Re: Air Head - Not Sure How to Title This One

Post by plmbcrzy »

OT-10 cam
Roller rockers
Hydraulic lifters
.052 head gaskets
.015 base gaskets
Stock 140hp heads

Yes hold closed, ty for the correction

All that is irrelevant, the question is how can they be leaking air both intake and exhaust on all cylinders of both heads. I could see it if I had done a half ass valve job myself, but I had them done by a reputable Machinist with decades experience and familiar with Corvair heads, or if the problem wasn't consistent across all cylinders both intake and exhaust.

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plmbcrzy
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Re: Air Head - Not Sure How to Title This One

Post by plmbcrzy »

Something odd is going on. I can't believe every valve and seat in both heads has an issue.

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Re: Air Head - Not Sure How to Title This One

Post by bbodie52 »

Is it possible in your new setup that somehow every valve adjustment is too tight — causing all valves to remain open slightly even at the bottom of the cam lobe? Not necessarily a leaky valve and seat but a valve that is not closing completely. :dontknow:
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plmbcrzy
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Re: Air Head - Not Sure How to Title This One

Post by plmbcrzy »

bbodie52 wrote:Is it possible in your new setup that somehow every valve adjustment is too tight — causing all valves to remain open slightly even at the bottom of the cam lobe? Not necessarily a leaky valve and seat but a valve that is not closing completely. :dontknow:
I have no push rods installed yet I guess I could have been a bit clearer on that

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plmbcrzy
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Re: Air Head - Not Sure How to Title This One

Post by plmbcrzy »

Now Jerry's reply makes sense to me

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plmbcrzy
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Re: Air Head - Not Sure How to Title This One

Post by plmbcrzy »

In my defense and not to be a Richard Cranium I did say all all I did was install "weak" springs, don't have pushrods yet

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Jerry Whitt
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Re: Air Head - Not Sure How to Title This One

Post by Jerry Whitt »

Why not put the proper springs to start with? With proper springs installed, the valves will be firmly on their seats. Spring pressures, not compressed should be in the 80 pound range. Compressed springs should be in the 175 pound range.

With proper springs installed, the leak down test should be less than 20 percent. If more than that, and there are whistles from any intake or exhaust valves, this indicates poor machine work. Should you have more than 20 percent and you here whistles from the oil filler, you then have a ring problem
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plmbcrzy
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Re: Air Head - Not Sure How to Title This One

Post by plmbcrzy »

From Clark's, used heads, everything is new, only have half the engine reassembled so far away, and only one pair of springs was removed. I'm using Otto performance springs. Not sure what a leak down test is. I put some air in to hold valves closed to do the spring change for the pushrod length calculation. I heard some leaking past the ring gap I assume. My hearing not bad but not great either so I put a hand on the exhaust tube and it built up pressure. If the gauge is right on the compressor I'm at 100psi. I'm then thinking how can this be when valve is closed? Call shop brought back he quick resurface seats and lapped in valves I watched looks great guy knows his stuff. Same issue. All 6 copper head gaskets squished now annealed 3 of them and put on other head same difference. I'm now thinking ok that's just how it is. It's just that it doesn't make sense to me that anything would be leaking with a heavier spring, a fresh valve job, and no pushrods or rocker arms in the way to be causing any problems. Thought then okay I'll put it up on the Forum and maybe somebody can explain to me what's going on. It's got to be something simple because it's beyond my comprehension.

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Re: Air Head - Not Sure How to Title This One

Post by Jerry Whitt »

A leak down test involves a gauge that most auto parts stores have. Some will loan it to you for free. (Auto Zone) Air pressure is attached to the gauge. Another hose is screwed into the spark plug hole. With the piston near top dead center on compression stroke, the hose going into the cylinder is now attached to the gauge. The gauge will not give a number reading. Less than 20 percent is considered acceptable. If the number is higher,
listen at the exhaust. A whistle indicates exhaust valve leak. Listen at the place where carburetors mount. A whistle here indicates an intake valve leaks. If the percentage is higher than the 20 percent and you hear a whistle at the oil filler, you have rings leaking.

One issue that bears mentioning. "New" parts are not always good. Used parts are not always good.
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66vairguy
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Re: Air Head - Not Sure How to Title This One

Post by 66vairguy »

I'm not sure what is meant by a "valve job. In the old days it was just lapping the valves and seats.

Anything short of new deep valve seats, new valves, and new guides is not acceptable on these old 140HP heads.

Worn valve guides will result in poor valve seating due to alignment problems.
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plmbcrzy
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Re: Air Head - Not Sure How to Title This One

Post by plmbcrzy »

66vairguy wrote:I'm not sure what is meant by a "valve job. In the old days it was just lapping the valves and seats.

Anything short of new deep valve seats, new valves, and new guides is not acceptable on these old 140HP heads.

Worn valve guides will result in poor valve seating due to alignment problems.
The old guides did have to be machined out then reamed to install the new ones. I wonder if the angle could have been off a hair. That would explain why it's occurring consistently and all Chambers intake and exhaust s*** I'm going to have to run that by the machine guy he's going to be pissed

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plmbcrzy
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Re: Air Head - Not Sure How to Title This One

Post by plmbcrzy »

plmbcrzy wrote:
66vairguy wrote:I'm not sure what is meant by a "valve job. In the old days it was just lapping the valves and seats.

Anything short of new deep valve seats, new valves, and new guides is not acceptable on these old 140HP heads.

Worn valve guides will result in poor valve seating due to alignment problems.
The old guides did have to be machined out then reamed to install the new ones. I wonder if the angle could have been off a hair. That would explain why it's occurring consistently and all Chambers intake and exhaust s*** I'm going to have to run that by the machine guy he's going to be pissed

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So I am correct in my belief that I should not be leaking any air out the intake or the exhaust if the valves seal properly to the seats ? because I am going to take these head back and tell them that he screwed up.

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rfw66
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Re: Air Head - Not Sure How to Title This One

Post by rfw66 »

A simple test for your valve seats, before you install them, is to lay them on your workbench combustion chamber up and fill the combustion chamber with water or alcohol, like you are measuring cc’s
Let them sit a few hours. If they don’t leak water or whatever you’ve used, the wont lead pressurized air! This will tell you to look at your head gaskets or your torque sequence. My 2 cense


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