Valve lift after cylinder head rebuild

C

Carlos

Member
Hello people , I need some advice about the valve lift I found after the shimming.
According the manual, the valve lift should be 0.370 in ( 9.40 mm ).
I measured the valve lift and found an average of 0.428 in ( 10.89 mm ).
Is it too much ? Any possibility of the piston hitting the valves ?
I enclose a couple of photos to illustrate.
I will appreciate any comment.
 

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I assume the valve clearances are correctly set. If this camshaft was in this engine and running without the valves contacting the pistons before you dismantled the engine, then I see no reason why they should make contact now.

With the head in place and it all timed up correctly, with plasticine on the top of the piston you could turn the engine over and then measure the thickness of the plasticine to give you a running clearance, but that will mean taking the head off again to get the plasticine out.
 
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harveyp6 said:
I assume the valve clearances are correctly set. If this camshaft was in this engine and running without the valves contacting the pistons before you dismantled the engine, then I see no reason why they should make contact now.

With the head in place and it all timed up correctly, with plasticine on the top of the piston you could turn the engine over and then measure the thickness of the plasticine to give you a running clearance, but that will mean taking the head off again to get the plasticine out.
Click to expand...

Thanks Harvey. The camshaft is the same, the head was slightly machined.
The plasticine solution seems quite clever.
In case I take the head off again, do you think I can reuse the head gasket ? Is the all metal one.
 
harveyp6 said:
If this camshaft was in this engine and running without the valves contacting the pistons before you dismantled the engine, then I see no reason why they should make contact now.
Click to expand...
I believe Carlos has had new seats fitted, hence them sitting proud of the head surface.

The valves are most likely sitting 1.5mm down from the original point. I think that's ok, but certainly closer than before. It would be sensible to measure the height of the valves when closed relative to the face of the head. Then measure the clearance of the pistons when at top dead center.
 
sdibbers said:
I believe Carlos has had new seats fitted, hence them sitting proud of the head surface.

The valves are most likely sitting 1.5mm down from the original point. I think that's ok, but certainly closer than before. It would be sensible to measure the height of the valves when closed relative to the face of the head. Then measure the clearance of the pistons when at top dead center.
Click to expand...
Thanks Sdibbers, the seats are the originals, slightly machined. I changed the four exhaust valves and one inlet.

The question is if in any moment of the cycle, when the piston is in top dead center, the valve is fully open ( max lift ).
In that case for sure its going to hit the valve.
 
Carlos said:
Thanks Sdibbers, the seats are the originals, slightly machined. I changed the four exhaust valves and one inlet.

The question is if in any moment of the cycle, when the piston is in top dead center, the valve is fully open ( max lift ).
In that case for sure its going to hit the valve.
Click to expand...
The valves will be closed when the pistons are at TDC so I wouldn’t worry on that count.
 
I'd be very suspicious of a head with proud seats, that is not correct. But I can see in the photo that's not the situation.

BTW, both valves are open, albeit not much, at the end of the exhaust stroke, aka the other TDC.

Something is fishy somewhere. 1.5 mm is a huge discrepancy, given the direct action valve train either the measurement is incorrect or you've got a non-standard camshaft. Could you measure one cam lobe, base to peak and the width at right angles to that? We'd be able to figure out the rough lift of the camshaft with those numbers.

Yours
Vern
 
Carlos said:
Thanks Harvey. The camshaft is the same, the head was slightly machined.
The plasticine solution seems quite clever.
In case I take the head off again, do you think I can reuse the head gasket ? Is the all metal one.
Click to expand...
I use the old, pre crushed head gasket for the plasticine clearance check.
 
if the cam is the same, then you cant of done anything to increase valve lift over standard, so it should be ok now
 
Vern Klukas said:
Could you measure one cam lobe, base to peak and the width at right angles to that? We'd be able to figure out the rough lift of the camshaft with those numbers.
Click to expand...

Ok. Vern, I measured one cam lobe and I have:

Height: 1.253 in ( 31.83 mm )
Wide: 1.628 in ( 41.34 mm )
 
I think I see your problem. Measure valve from deck of head when closed, now measure from deck of head when open. Subtract closed distance from open and that will give you your valve lift. I bet it’s in spec then.
 
Carlos, those measurements suggest a lift of .375", which is right in the ballpark of correct. So I suspect something about how you are measuring the lift is giving you a false result.

Yours
Vern
 
sdibbers said:
I think I see your problem. Measure valve from deck of head when closed, now measure from deck of head when open. Subtract closed distance from open and that will give you your valve lift. I bet it’s in spec then.
Click to expand...

Ok !! Ok !! Thanks Sdibbers ! I think you've got it ! They call ¨valve lift ¨ the difference between the two distances. Thanks !!
I will do the measurement when I install the shims coming: Thanks !
 
Vern Klukas said:
Carlos, those measurements suggest a lift of .375", which is right in the ballpark of correct. So I suspect something about how you are measuring the lift is giving you a false result.

Yours
Vern
Click to expand...
Hi Vern, I made about 5 measurements and then an average calculation. Anyway I'm using the back of a digital caliper. I know is not the ideal tool but comes close. Anyway I think Sdibbers has got the answer. Thanks.
 
Carlos said:
Hi Vern, I made about 5 measurements and then an average calculation. Anyway I'm using the back of a digital caliper. I know is not the ideal tool but comes close. Anyway I think Sdibbers has got the answer. Thanks.
Click to expand...
Yep, I’m pretty sure you’re safe Carlos.
 
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