LT Texan

Same here!!! (Sans the broken cam belt and bent valves. Knocking on wood)

LT Texan

hard to do with the 928 set-up, hydraulic lifters, timing belt and all. Unless you're just going to push down a valve max lift height while at TDC.

mark kibort

thats another good point, and why that technique wont tell much. i bet most of the lifters on a newly disassembled engine are pumped up, but I dont really know. bottomline, if they are not, there is 1.4" or so that is not pushing down on the valve. thats why, just pressing the valve down in the head with the piston at TDC is the way. if you know the cam lift, you know how much the valves will be pushed down, worse case.

here is how you do it, (devek trick, thanks Marc! ) and this is what it looks like with clay before and after
the fix.

mk

RCinXS

Mark, Sorry for any confusion about referring to the previous PM to you, but that's why I said I would check at TDC only in Post #13.

Quote: "Mark, Going to clay the pistons as described in my previous PM to you. TDC only."

Don't even need a wrench to push the valves down. I'll do it with extremely light springs or no springs at all.

I have no intention of even having the cam towers in the same room as the engine when I clay it.


By the way, there is a way to pump up the cam followers before assembly and keep them hard. I do it all the time when I drain cam followers to flush them out. You'd be surprised what comes out of them.

Once I pump them up, I store them in some early 16V cam bushings. If you insert the cam followers upside down in the Cam bushings there's enough seal to stop the lifters from bleeding off for quite some time.

The hole is then against the bushing wall, not the oil groove. I use good old STP to lubricate the Cam bushing before inserting the cam followers for storage. Makes a great seal. I just checked a set that I did last December and they are still hard as a rock.

LT Texan

Mark,

You use play-doh, not clay?

Oh my.

123quattro

Last time I did it I used pink play doh.

RCinXS

Here's and Update on the US 4.7 Pistons and Euro S cams in my engine.

Regarding the DEPTH of the reliefs from the factory.

U.S. Valves At TDC:

Inakes bottoms out in the relief at 0.5610" valve depression.

Exhaust bottoms out in the relief at 0.5620" valve depression.

So as far as the Euro S cams go with 4.7 U.S. Pistons, Heads and valves, absolutely still a non interference engine.

By the way, The engine is unbelievably clean on the inside.
No scaling around the clyinders. (Pays to change it every 2 years.)
Cylinder bores are as near perfect as I have ever seen on a 27 year old engine.
The cleaner piston was just wiped off with a rag.

Will clay them up after lunch and see what the diameter clearence is with the U.S. valves. Should have the Euro heads back tomorrow.

mark kibort

I have kids, so playdoh is readily available

hey, it works doesnt it!

RCinXS

I used plumbers clay.

With the US valves:

Intake valve a bit more than 1mm diameter more than the valve at the deepest part of the relief.

Exhaust valve 1mm more in diameter, also at the deepest part of the relief.

1mm cushion from the factory, just like Mark Kibort said.

Guess it'll be dremel time.

But the great news is it'll still be a non interference engine.

mark kibort

RCinXS

OK. Another Update.

For kicks, I decided to see just how tight the Euro valves fit the reliefs.

Using a U.S. head, I inserted exhaust and intake valves and tested on one cylinder.

The clay revealed no contact with the reliefs but was way too difficult to measure the cushion.

After thinking about it for a while, I decided to use some palstic sticky film that I have, and built up 6 layers of it and cut it so that it would fit the wall of the reliefs.

The thought was to use it sort of like plasti guage.

The thickness of the built up layers at this point was .5mm or 0.0200" - 0.0210" if you'd prefer.

There was no contact with the film from the valves, so I made it 8 layers. That's about 0.0260" - 0.0266" or .66mm - .68mm.

There was slight contact towards the end points of the reliefs, but not at the deep part. Could be due to a variance of the pointed profile of the film or even a slight crease that may have occured as the film was curved.

When I told the machinist how much clearance there was, he told me that he thought 0.021" would be fine.

Any opinions on how much more clearance I need, if any?

RCinXS

Heads installed.

Everything turned out great.

Cams can be rotated 360 degrees at #1 TDC.

Guess she's still a non interference engine!

Sliding the engine back in on the 6-13-11.

Thanks to eveyone for all of your input!