Valve gap grows on my 74f rebuild (1 Viewer)

[rsbcruiser]

I think so.......

Ya, their toast. thinking my head mechanic had health issues, missed something basic. Now the only real desicion is do I man up and yard the whole mill out of there or wimp half way into it only to decide hellwithit, out she comes? latter philosophy has got me this far just fine thank you. Maybe slip some stainless steel valves by the Missus, you know, for my troubles.

 

[rsbcruiser]

Looking for answers

Bad leak down test, magic expanding valve gaps, why oh why? Checked the valve train. The pushrods look fine. The rocker asembly, very nice, no slop. Could it be these, nope see no problems here. Nice toasty patina on a couple valves, 1/4" carbon buildup after 3000 miles. No sirree no problems here.

 

[rsbcruiser]

Wait a second, think I found it

You are looking down into the exhaust port of # 1 hole. Might we be on to something ? Off to the rebuilder. Looks like the Ol wolf called it. I'd guess It was the valve guides, what say IDave?

 

[grant5127]

#1 had your best numbers... post up a pic of the piston tops and cyl. walls.......

 

[rsbcruiser]

#1 had your best numbers... post up a pic of the piston tops and cyl. walls.......

Funny thing is, # had the big scratch (fingernail catcher before hand honing).

 

[rsbcruiser]

Grenading valve guide carnage

Here is a good shot of cylinder 5. Looks like the guides did a little damage on their way out. Heard from the head rebuilder today. Guides were toast. Most had been knurled. I think my old mechanic did this one. Rebuilt heads arrive day after tommorrow. Was thinking I'd slap them on and call it good. Now I'm thinking I'm tearing in there and honing and reringing. Now I have to track down a set of rings and another gasket set.

 

[rsbcruiser]

Intake valve stems

This picture shows # 1 and # 2 intake valve stems. looks like # 2 let go. # 1 looks healthy.

 

[grant5127]

That thing needs to be bored....actually, being the block is cracked I would get shed of the whole mess......

 

[IDave]

Could you just hone it and see what you have in the way of lips and gouges?

 

[rsbcruiser]

Could you just hone it and see what you have in the way of lips and gouges?

That is the decision I finally reached last night. I now plan on tearing the bottom end down, honing all cylinders again. New rings, again. Grant, I know that this whole thing is a catastrophy of epic proportions but...... The stitching thing, a definite no big deal, bye bye crack $80 down. Feel confident it will work. Plenty of hole left, plan on one day going back and doing a proper rebuild on the bottom end. Heads, well forget about that, tomorrow has me wrapping mits around ported, rebuilt, again, all new guides, stainless ex valves, Downey valve springs, new rocker assembly, new lifters being lifted by Downey cam, new bearings in bottom end. So Grant I could find another block and lose some or all of my investment or stick to it. It's a damned if I do damned if I don't thing. Not afraid (not looking forward to it) to post that well, looks like ol grant was right post. So how bout a wish me luck. I have also noticed that yanking the ol anchor is getting easier. I do (though I don't hear numbers (as in $)) appreciate your input, thank you.

 

[IDave]

Well, no offense to anyone's good intentions and overwhelming kindness, but in my small experience, 2 replacement engines were a lot more time, work, disappointment and cost than rebuilding the original, in my case. That's what I'm doing now, and I wish I'd done it that way to begin with. Maybe a chevy small block would have been better yet, but that's not what I wanted.

When you hone the cylinders, mic them as well (rings don't seat well in oval cylinders, guess how I know), and look at the cam lobes for wear. You may wish you had if you don't do it now.

 

[Pin_Head]

I'm a little skeptical that worn valve guides would explain the valve clearance keep shrinking. It would make it vary each time you test it, but it wouldn't keep expanding or shrinking like if the lifters were wearing or the valve seats wearing into the head.

If I had known that you were going to tear down the engine, I would have recommended just getting a new block, although I think that the stitching will work out.

 

[rsbcruiser]

Well, no offense to anyone's good intentions and overwhelming kindness, but in my small experience, 2 replacement engines were a lot more time, work, disappointment and cost than rebuilding the original, in my case. That's what I'm doing now, and I wish I'd done it that way to begin with. Maybe a chevy small block would have been better yet, but that's not what I wanted.

When you hone the cylinders, mic them as well (rings don't seat well in oval cylinders, guess how I know), and look at the cam lobes for wear. You may wish you had if you don't do it now.

Totally in agreement with you IDave. The bottom end was on the rebuilders desk, he passed. I took the block home, miked the piss out of it, cyl. walls were .0005" at the worst from Toy out of tolerance spec with no more than .0002" out of round. All crank surfaces a-ok so I honed cyls. and rebuilt, all new bearings (no regrind), new valve train except cam gears (.005" lash) and pushrods. Now Idave i am second thinking it, opportunity has popped up so that I can rebuild bottom end right. So..........what do you think IDave, fellow shade tree wrench? Tearing in there to have a look this weekend. Let you know whats happening. Oh and small block SHmall slock, Me thinkin the new Toy straight 6 diesels the way to go. New diesel tech kicks butt at the pump.

 

[rsbcruiser]

Guides did it

I'm a little skeptical that worn valve guides would explain the valve clearance keep shrinking. It would make it vary each time you test it, but it wouldn't keep expanding or shrinking like if the lifters were wearing or the valve seats wearing into the head.

If I had known that you were going to tear down the engine, I would have recommended just getting a new block, although I think that the stitching will work out.

Guides are what faulted. Actually Pinhead, your skepticism is the result of confusion. The gap GREW over time. but like you said, they would surprise me alot of times. One or two would be too tight, no gap. Talk about your mechanical skills crisis, try seeing all that happen, even you, I bet would be reviewing your procedures, looking at your wrench like it done you wrong. That all settled out, they all showed increasing valve gap until settling down. Going in there this weekend, now second guessing, thinking maybe going all out, punch (0.040"), regrind, balance, do it right. PS, your gonna drool over the rebuilt heads, man o man. Sweet!

 

[IDave]

Totally in agreement with you IDave. The bottom end was on the rebuilders desk, he passed. I took the block home, miked the piss out of it, cyl. walls were .0005" at the worst from Toy out of tolerance spec with no more than .0002" out of round. All crank surfaces a-ok so I honed cyls. and rebuilt, all new bearings (no regrind), new valve train except cam gears (.005" lash) and pushrods. Now Idave i am second thinking it, opportunity has popped up so that I can rebuild bottom end right. So..........what do you think IDave, fellow shade tree wrench? Tearing in there to have a look this weekend. Let you know whats happening. Oh and small block SHmall slock, Me thinkin the new Toy straight 6 diesels the way to go. New diesel tech kicks butt at the pump.

If you can go diesel, do it! That's beyond me. I'm slapping together my rebored original.

Sounds like the bottom end is NOT your problem unless the damage from the grenaded guides was severe...(what do I know, tho?). What exactly happened with the valve guides, and why did they let go?

When you did the leakdown tests, you said it leaked from everywhere. What did you mean by that? Bubbling coolant? Noise from the carb? Noise from exhaust? Noise from crankcase/pcv?

 

[rsbcruiser]

I'm slapping together my rebored original.

Sounds like the bottom end is NOT your problem unless the damage from the grenaded guides was severe...(what do I know, tho?). What exactly happened with the valve guides, and why did they let go?

When you did the leakdown tests, you said it leaked from everywhere. What did you mean by that? Bubbling coolant? Noise from the carb? Noise from exhaust? Noise from crankcase/pcv?[/quote] IDave

Leakdown tests revealed that most of my intake valves were toast. Lots of noise from intake manifold. Most of the exhaust valves whistled pretty good too. When I listened through the oil fill it was a regular hurricane up in the heads. But, down below, all was fairly quite. pvc was quite. There was no evidence of a blown headgasket. Comparing the wet dry pressure tests to the damage on the cylinders revealed a rough correspondance. With a change on several cylinders (between wet and dry) of maybe (the numbers are posted in a thread above) 10psi it is possible I have some ring leakage. The scratches shown in the thread above look bad but only a couple hang a fingernail. What happened to the valve guides was they were knurled, the knurling was too tight. The knurled part of the guides fragmented, jamming between the guide and the valve stem. The jamming stopped the valve from competely closing, thus causing the valve gap increase. When the fragments finally freed, the pieces went down the intake, into the combustion chamber. Maybe the valve keepers were involved too. Not all that familiar with that assembly. Looking real serious at a total rebuild now.

 

[IDave]

So do you think that the head rebuilder knurled the inside of the guides himself, and picked too small of a diameter? Or did he buy aftermarket guides that were knurled too small? I would assume original guides for these engines weren't knurled, but only because it's a newish thing, right?

 

[rsbcruiser]

So do you think that the head rebuilder knurled the inside of the guides himself, and picked too small of a diameter? Or did he buy aftermarket guides that were knurled too small? I would assume original guides for these engines weren't knurled, but only because it's a newish thing, right?

IDave, Dick actually knurled the guides himself. I believe he resized them too tight. He also installed an incorrect (chevy) valve guide. So basically, he hosed the whole thing. The new rebuild has all new guides. It is also recieving solid stainless exhaust valves. I am tired of dealing with it, fineto! No more burnt valves. Oh, hey did you know the stock valve seats are like rock. Brian, down at Bearing Services said replacing the stock Toy seats with a stelite or some other fancy seat was an exercise in futilety. Apparently, you can't buy better valve seats than the stockers.

 

[IDave]

IDave, Dick actually knurled the guides himself. I believe he resized them too tight. He also installed an incorrect (chevy) valve guide. So basically, he hosed the whole thing. The new rebuild has all new guides. It is also recieving solid stainless exhaust valves. I am tired of dealing with it, fineto! No more burnt valves. Oh, hey did you know the stock valve seats are like rock. Brian, down at Bearing Services said replacing the stock Toy seats with a stelite or some other fancy seat was an exercise in futilety. Apparently, you can't buy better valve seats than the stockers.

That's cool. Don't blame you for going stainless!

 

[grant5127]

Knurling valve guides is a used car lot fix, a term known among them as "good e-nuff to get it off the lot" repair....IIRC you said the motor had 3 or 4K on it since the repair? if so thats about a normal length of time before you start noticing some issues.....