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  #21  
Old 11-19-2014, 04:56 PM
lr172 lr172 is offline
 
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Location: Schaumburg, IL
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Quote:
Originally Posted by jayyau View Post
Hi Larry,

This Engine is 1960 Lycoming O-320 Engine, model B3B, the guy who overhauled it installed a new Cam but didn't replace the tappet/plunger, that's a terrible mistake.
That's a major league no no! Lifters can be replaced without cam replacement, but never the opposite. You should have mentioned that first. In a perfect world, the tappet wore into conformity with the cam. If you wore .100" off the cam lobe, you'll pay for that in performance through to TBO.

I understand the desire to avoid a tear down, however, I would not wallpaper over this by putting in longer pushrods just yet. If it were me, I would confirm how much lift you have left on each cam lobe. If an acceptable lift exists, then go ahead and consider the work around with pushrods.

I would find a stable way to put a dial indicator on each pushrod or plunger and rotate the crank through a full lobe rotation and measure the travel. Compare each intake to each other and each exhaust to each other. The intakes should all be the same as will the exhausts (I would assume different lifts for Intake and Exhaust, but don't know). I don't have spec's for the lift on these cams, but clearly 3 of your lobes are in pretty good shape so you should have a close reference value. Maybe one of the engines experts can give you the lift spec for your cam.

After that test, you'll know if you have wear on your cam. If you do, I would recommend replacing it with all new tappets this time.

EDIT: My recollection from past research is that when you put non-new, mismatched lifters they will not develop a rotation of lifter. This leads to long-term wearing of the lobe and lifter that never settles. A new lifter has a concave/convex (I forget which term is appropriate - It is a dish shape) surface that works with the slight angle cut of the lobe to initiate a rotation of the lifter. As the tappet wears into conformity with the lobe, this dish shape developes a mating that maintains rotation of the lifter. If the lifter does not rotate, excessive long-term wear is inevitable.

Larry

Last edited by lr172 : 11-19-2014 at 05:13 PM.
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  #22  
Old 11-19-2014, 08:58 PM
jayyau jayyau is offline
 
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Location: Irvine, CA
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Hi Larry,

"I would find a stable way to put a dial indicator on each pushrod or plunger and rotate the crank through a full lobe rotation and measure the travel."

Great advise, very scientific. I'll find a way to attach a dial indicator and measure the cam lobe travel. Thank you so much Larry.

Jay
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  #23  
Old 11-22-2014, 10:49 PM
jayyau jayyau is offline
 
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Dry Tappet clearance

Last edited by jayyau : 05-22-2016 at 12:11 AM.
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  #24  
Old 11-22-2014, 11:19 PM
lr172 lr172 is offline
 
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Originally Posted by jayyau View Post
I measured #4 cylinder cam lobe travel today, the exhaust cam traveled 0.359", the intake cam traveled 0.351", so they both are in the 0.350" region. I'll measure other cam lobe travel when checking their dry tappet clearance.

I replaced another push rod with 0.151" dry tappet clearance, the new clearance = 0.032". New rod is only 0.020" longer, but it cut the gap down to 0.032", with over all reduction -- 0.119". the ratio is near 1:6.

My theory is, the new rod needs to break-in with the rocker and plunger sockets, I'll re-check the dry tappet clearance again after running the Engine for 10 more hours.

I think measuring the cam lobe travel is the best way to determine the condition of the cam lobe and tappet without removing the Cylinders.
You have some type of measuring error. The ratio is NOT 6:1. I might buy 1.6:1. That is the ratio for a small block ford with stronger valve springs than a lycoming. I am still guessing between 1.4:1 and 1.5:1. Either way it's not even in the same neighborhood as 6:1. You need to get a handle on your approach for measuring the the lash.

While the lobe measurements are encouraging the only real comparison is against like lobes. We need to see all four to be sure. But, given the above, I think you are having an issue with measurement. Are you sure you got the springs in the plungers fully seated? It takes a good push while turning. If you rotated the engine, the valve spring pressure would do it and explain your theory of "breaking in."

Larry

Last edited by lr172 : 11-22-2014 at 11:22 PM.
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  #25  
Old 11-23-2014, 12:33 AM
jayyau jayyau is offline
 
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Dry Tappet clearence

Last edited by jayyau : 05-22-2016 at 12:11 AM.
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  #26  
Old 11-23-2014, 09:21 AM
deek deek is offline
 
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Sent you a PM Jay

dk
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  #27  
Old 11-23-2014, 03:37 PM
lr172 lr172 is offline
 
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If you got the tappet clearance right, you are good. I would still question the measurement of the pushrods themselves, but in the end all that matters is that the clearance is correct.

I would still confirm that you have a consistent lift across lobes to uncover the reason for the improper clearance before you started.

Good luck,

Larry
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  #28  
Old 11-23-2014, 06:50 PM
jayyau jayyau is offline
 
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Dry Tappet clearance

Last edited by jayyau : 05-22-2016 at 12:12 AM.
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  #29  
Old 12-06-2014, 05:28 PM
scarter770 scarter770 is offline
 
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Quote:
Originally Posted by lr172 View Post
I avoided all these problems. after moving parts all around, I had three pushrods that were too short to meet spec. For each one I determined how much longer I needed it to be, using a formula similar to the OP's. (found the factor on a post here). I sent the 3 pushrods to Manton pushrods (I don't have calipars or mic's that large). They measured my existing rods and added/deleted the dimension I provided for each and they shipped me 3 new custom pushrods. I paid $10.50 per pushrod and the quality far exceeds the Lycoming. Pushrods are quite a bit beefier, but the weight penalty is insignificant in my opinion. They cater to the racing business where everyone needs thick-wallled pushrods, so they don't carry the thin-wall material.

Larry
Manton and Smith Brothers are the premier pushrods builders in the country. I found Lycoming pushrod length random at best. I use Smith Brothers for all my requirements. Stock ratio is 1.28 to one.
Thanks
Steve
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  #30  
Old 12-07-2014, 12:10 PM
jayyau jayyau is offline
 
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Quote:
Originally Posted by scarter770 View Post
Manton and Smith Brothers are the premier pushrods builders in the country. I found Lycoming pushrod length random at best. I use Smith Brothers for all my requirements. Stock ratio is 1.28 to one.
Thanks
Steve
Hi Steve,

Which engine do you have?
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