Royce, ain't no how, ain't no way I would bolt those heads back on with less than .0018" guide clearance. I would prefer to see .0020" on the exhausts. Intake valves grow too!

This isn't Daytona and there isn't a million dollar prize for winning. Tight guides are all risk and no reward.

I would rather be down 3 horse power due to loose guides than be down 3 cylinders when the guides sieze up.

http://ford-y-block.com 

20 miles east of San Diego, 20 miles north of Mexico

No evidence of valve hitting piston when we pulled the head and no damaged push rods.. Ted I'll pass on your experience,, If I recall it was an intake lifter that broke

Further on lifter failures; the latest issue of YBM, issue #102, contains the Dyno test of the Church Bros Y-Blk racing engine. It too suffered a lifter failure & block damage. However, it was found that a cam timing error resulted in a valve hitting a piston, and the blow breaking a lifter. Could that have happened to the Christenson engine??

Paul

Royce.  Pass on to Jerry that I worked on an early model Austin Healy 4 cylinder early last week that had stuck the two center exhaust valves due to being too tight on valve stem clearance.

 

Here’s the full story.  I’m involved in this as I had originally recommended and milled the heads 0.055”.  This was just prior to the heads going to another shop for new valves, bronze guides, and a valve job.  Once that freshly machined head was reinstalled on the engine, the center exhaust valves banged the pistons after 25 minutes of running.  This engine was never under a load and simply started missing prior to it being shut off.  Not only did the valves whack the heads hard enough to bend, the pushrods also wadded up.

 

The customer then took the removed head back to the shop that did the guide installation and the valve job.  That shop said the problem was in the valve to piston clearance which they pointed the problem back to the head milling.  When the customer called me on this, I simply told him to bring the engine to me and I would go to the trouble of checking those clearances.  Upon doing the checks, I found that the valve to piston clearance was 0.155” on the intakes and over 0.200” on the exhausts; this was more than adequate.

 

Because I now had the cylinder head apart, I checked the stem to guide clearance on the valves that banged the pistons and found them on the tight side at 0.0011” and 0.0016”.   Although the hole size in the guides were the same, the two valves in question varied 0.0005” on the stem diameters.  And to compound the problem, the exhaust valves stem diameters were slightly larger than the intake valve stem diameters.  Final analysis is that both of the center exhaust valves share the same exhaust port so these two valves naturally get hotter than the valves on the end cylinders; subsequently they just ‘seized’ in the guides first due to inadequate clearance to compensate for expansion when hot.  In looking at the stems and the guides on the two that bent, there is no evidence of any galling.

Lorena, Texas (South of Waco)

John, the clearance on the guides varied from .001 to .0013. Jerry had them all redone to .0013.. The machinist was emphatic that none of the guides had stuck a valve.. The engine only made one short pull so it was never under a sustained load.

Royce, I would be curious to know what the actual guide clearance on Jerry's heads was. I have seen valves stick at .0016" on a 455 Olds jet boat.

Hopefully everythings works out better when its put back together.

http://ford-y-block.com 

20 miles east of San Diego, 20 miles north of Mexico

Agree that it is a fresh break, also a break as such would not have time to show wear, I think the head would have just dropped off into the pan.

On another note, I don't know if the cast lifters are anything like railroad rail material but I have had an instance where assembling machinery a piece of rail was dropped 6-8' and it broke in half. I have also heard in the old days they could scribe rail where they needed and break the rail there, I have not seen it done personally but beleive it since seing that rail break. Trains ride on that rail and it flexes seriously and takes all kinds of abuse but if scoured shatters like glass.

Could Jerrys lifter, or many lifter failures for that matter be caused by a scratch on the surface?

55 Vicky & customline

58 Rack Dump, 55 F350 yard truck, 57 F100

59 & 61 P 400's, 58 F100 custom cab, 69 F100, 79 F150, 82 F600 ramp truck, 90 mustang conv 7 up, 94 Mustang, Should I continue?

Hate to say it but I think your right. 

That break does look too clean.

No one to blame except me.  Hopefully my last mistake.

Thanks

Dale

That break looks like it might have occurred during the teardown as there’s very little evidence of wear at the break itself.  Not saying this is what happened, but a break like this can take place in pulling out the camshaft aggressively with the lifter not pushed up (or down depending upon your perspective) all the way into its hole.  A moderate hit from the side at the lifter foot will snap the lifter shank.

Lorena, Texas (South of Waco)

That is a picture.  Doubt if it is possible but sure hope worse damage didnt result.  Quite the first post!  Welcome!

Mike, located in the Siskiyou mountains, Southern, OR 292 powered 1946 Ford 1/2 ton, '62 Mercury Meteor, '55 Country Squire (parting out), '64 Falcon, '54 Ford 600 tractor.