Big Dave

Did the valves that weren't visibily bent hold any compression? I'm assuming that air will leak past a bent valve before liquid will. Then again, I'm personally in completely uncharted territory here.

T_MaX

Dave A. is right, if you really want to check each valve yourself, you can poor water or oil down the ports, wait a few minutes and check for wetness in the combustion chamber.

Pre-cleaning the combustion chambers would be a good idea.

You would have had to do a leakdown test to get a true idea of what vales were bent. A compression test only shows the obvious.

DR

Dave,
>Cam removal Special Tool 9226, on loan from Dave Roberts

Heh, watch those greasy fingerprints, those tools are made of unoptanium :-)

You know I 'm kidding, Oh, don't forget about the "template" we discussed before you return them.

Big Dave

They will be spotless upon their return. I'm getting good at this cleaning stuff, but everything I own smells like a cross between mineral spirits, oil, and Gunk.

I will be making a detailed diagram of the tool and its dimensions so I can make a copy of it out of suitable materials. Does anyone know the thread pitch for spark plugs? Just curious.

DR

>They will be spotless upon their return.

Not necessary, as I said it was a joke, plus they certainly weren't spotless when you got them.

> I'm getting good at this cleaning stuff, but everything I own smells like a cross between mineral >spirits, oil, and Gunk.

Don't forget your gloves or your hands will look like mine!

>I will be making a detailed diagram of the tool and its dimensions so I can make a copy of it out of >suitable materials.

As I said on the phone it is great idea.

>Does anyone know the thread pitch for spark plugs? Just curious.

I should know that off the top of my head, let me finish my 2nd cup of coffee and I will get back to you.

Tom. M

Nope...absolutely zero....shoulda seen the look on Thurstons face...we did a compression check starting at the driverside...working forward...over to passenger side...all fine...until number 4....

Thurston gets this puzzled look on his face and says..try it again....at that point I knew I had to take the head off..but in hindsight....2 valves out of 32..not bad....

When the head came off I couldn't physically tell which valves were bent..intake or exhaust... I did notice some impressions on the piston and some broken up carbon but not obvious bendage. A little water down the ports..and sure enough..droplets formed on the underside of the two intake valves. I have one of the valves here on my desk at work for a reminder...can't even really see the bend until you roll it in your hand.

When I replaced the valves, the seats and pretty much everything else was fine so I just lapped the valve with some lapping compound right in the head...used a piece of tubing slipped over the end of the valve and the other end in a drill....looked for even burnishing on the seat and valve..and was good to go...

later,
Tom

John Veninger

Can I buy one when you start making the copies?

docmirror

Dave, you're probably going to hear two trains of thought on reusing your old cam followers. Generally, once a follower is out the bore it was in, it's replaced. That's not always true, but the followers take a certain 'set' to the bore and the cam lobe. Once moved to another bore, the 'set' is no longer valid. Some people have been known to reface the lifter/follower, and reuse it in any bore. This has perils as well, bucause the face of the lifter/follower may not be perfectly flat, it may be slightly concave. Also, I would assume you are not going to regrind your cams, so the finish you have on them now is the finish you are stuck with when reassembled.

What should have happened, is to keep track of the bore locations of the lifter/followers and return them to the original bore with a bit of lifter lube for startup. At this point, it's a crap shoot, and like I said, you'll hear several different arguments both way. Some will say it's alright to reuse them in any lifter bore. I would disagree, but that just one man's opinion. Spalling a cam can start to get expensive, and although it can be serviced in the car, it's still better to redo it right with all new lifters/followers. Talk to a cam shop about having your's reground. They can look at what you have, and determine if they will take a grind, or require Nitriding, or other surface conditioning.

Each valve train is different, it may be that the 928 engine is forgiving of lifter location, and tends to not spall the cam, or, it may be the opposite, that the engine is notorious for cam spalling in even the best of circumstance. A lot depends on the amount of lube received, and also on the heat of the cam area, valve spring pressure, cam material, lifter material, radial motion of the lifter in operation, bore fit, lifter rocking, and operating RPM. It's complex, with no clear defined yes or no answer. The cost to replace them is probably high, but the cost of damaging the cam is even higher.

Sorry it's not an easy answer. If you know for certain which lifter came out of which bore, keep them in order, and reuse the ones you are sure of in the same bore. Or, you can roll the dice, and just put them back in where-ever and hope for the best.

Big Dave

Put it this way, I'm using a different set of heads. I did not keep track of where the tappets came out of relative to my old head.

This the first time I've heard that they are "mated" to the bores them came out of, although I admit I've never paid attention to the issue before. Perhaps Mr. Roberts or Wally can chime in on this?

Big Dave

I hadn't thought about it, but I suppose that's a possibility. Let me look into it.

Big Dave

For whatever it's worth, 928 International has used lifters for sale on their website, which leads me to believe that they in fact CAN be re-used in heads different from where they were originally used.

Chris

Dave, good progress.

I kept tally of where my cam followers/tappets/lifters (whatever you want to call them) came from but some of mine were v easily depressed withy finger pressure. Others were rock hard, no matter how hard I tried to prime them the ones that were easily depressed would not change.

Think I had about 6 like that, I got an assortment of used from one of the vendors and went through and found some good ones. Put them in and ran fine, will it be OK in 100K miles ?? Dunno will let you know.

In an ideal world be great to replace with new ones, specially of they were inexpensive, they are not so IMO just re-use in your new heads.

Chris

Bill Ball

My 24 valve CBX motorcycle engine valve train sorted nicely into 2 egg cartons. Three egg cartons would have done it in this case.

Rich9928p

If you have more than 100,000 miles on the engine it is always a good idea to replace the cam chains and tensioners. Certainly a while you're in there issue.

docmirror

Dave, they aren't "mated" in the sense that the lifters are bored to the hole, or machined to the lobe. They most definantly are 'set' once installed and run. Ring and pinion gears are a mated assembly. Lifters are designed to spin in the bore when running, and when moved from one bore to another they may not spin, and develop a gouge or rut that the lobe runs in. This is destructive.

Here's what I've done in the past. Used lifter reconditioning: Use a piece of flat glass, tape a very fine 1800/2000 grit piece of wet/dry sandpaper, and tape over the glass. Use Kerosene or diesel fuel as a lube fluid. Turn the lifter on it's face, and press on the very center of the inside of the lifter to gently work it in circles on the paper. Rotate the lifter from time to time, and work until the face of the lifter is nicely polished. I've seen people use a drill and valve suction cup to do this, but keep it moving in a circle on the paper.

It can take a long time if the lifter face is very concave. If you polish through a shiny face, into a dull metal underneath, the lifter will need to be professionally redone, with a heat treating. The lifter face is very hard, so plan on spending some time at this. Or, as mentioned before you can just clean and reassemble and hope for the best.