atb

Prematex gasket remover. Spray on, let soak, wipe off.

RyanPerrella

I'm in the valley, the engine is in a garage in Reseda

Thanks for all the suggestions, still havent gotten out to get some of those discs, although i do have some of that gasket remover stuff i may try that later. I think i just want to wash off this shortblock, its so filthy, every time i touch the stupid thing my hands come back black.

dr bob

Start off with spray engine cleaner, then soap and water in the pressure washer for the outside. If the stuff comes off on your hands, it will come off with detergent and the pressure washer. Messy but effective.

Koenig928

I used a bunch of those tiny Dremel tool wheels that look like 3M pads, about 1" dia., are sold in a 2 pack at Lowes. I cleaned out 2 different stores, twice. They work great on the valves and heads, but I wouldn't use them on the pistons.

I had severe carbon deposits on my valves, measured 2mm thick on several spots. What a nightmare that was to get rid of...

'Normal' carbon deposits are not too difficult. I even polished mine on a bench grinder afterwards and then re-seated each valve with grinding paste. Worked like a charm.

RyanPerrella

Bill, when you took your heads off and removed valves, i assume you didnt have the seats or valves recut, you just used lapping compound on them? I guess once you do that you can see if the valves need to be recut, and if the wear pattern from the lapping paste isnt even then you get them cut right?

Koenig928

Nope, only ended up using lapping compound. And yes, it will be obvious if they do not lap evenly. Unless they are bent or happened to bite on something getting injested, I don't think you'll need to recut them.

I was thinking the same thing before myself, but finally figured out I don't need to. There's a metal ring pressed into the head for the seat. And the valves are kinda interesting, the top half of the shaft is magnetic, and the rest is not (including the flared bottom).

I searched long and hard to find those specific "Neway" valve cutters that the WSM's say to use - they're a few hundred bucks for a set.

RyanPerrella

as for lapping its as simple as placing the valve in puting some paste in between the valve and the seat and using a lapping tool and twisting the valve in there back and forth right. that motion along wiht the compound will show if the valves will seat correctly, if they do then just remove the paste and reinstall correct?

Mind you these heads came from an engine that had a frayed TB and of the 32 valves, i have 2 intake valves that i know are bent, i will try some of my replacement vales to replace those, but there dosent appear to be any other damaged valves. I assume hat if i lap all of them if they all show a good contact patch that i can assume all the rest are straight as well.


thanks for the fast reply

ZEUS+

If you can, use prussian blue after lapping. It will show seat contact on valve. Should be in the center of valve face.

dr bob

It also shows the width of the seating area, somewhat critical at least in a performance engine.

Remember to number the valves so they go back in the same holes that are lapped to.

If the guides are worn, lapping won't work well. The valve needs to be held concentric with the seat for accurate seat prep and sealing. Worn guides won't do that for you, and you risk dishing the seat slightly.

Keep the lapping compound off the stems and out of the guides.

Wash the head thoroughly before assembling it again.

aguk928

Now this is a contention.

Some Porsche racing guys I have spoken to here in the UK that do 924 944 and 928 engines say that never lap but re cut as lapping will not give the correct 3 angle seating that valves need in these engines for best performance, having said that I lapped mine about 10k miles ago and compression and leak down are still A1.

Yes if you lap you need to wash everything 100% as otherwise the brass guides will suffer badly how do I know don't ask!

2V4V

Lapping v. 3-angle/5-angle is a matter of expediency and/or budget constraints.

A properly done 3 or 5 angle job will outflow a single angle (hand or drill lapped) seat. The angles on the seat and valve lip help generate 'tumble' and keep the air moving over the edge of the valve. Fluid dynamics stuff.

A properly done hand lap will save you the week (or month) you have to wait for your Porsche familiar machinist to get to recutting all those angles. It will also save you the $$$ you would have had to spend there.

If you do it right, and all goes well, the hand lap can be quite functional. Never as optimal as high-quality machine work, but hey, you do whatcha gotta.

Greg

RyanPerrella

I went ahead and lapped one intake valve, and i must say i am impressed with what it left me with, a nice concentric seat and valve. I am going to completely clean these heads and finish disasembly on the 2nd head before really get into the lapping process, but it works pretty fast I must say.

As for the actual sealing, the sealing surface is only one of the 3 correct, the middle cut, the widest one is the actual sealing surface right? above and below it are the 2nd and 3rd cuts of a 3 angle cut which are there primarely for airflow reasons, not for sealing. Am i right on this valve theory? If so then my seating surface is great on the one valve ive done so far. JUST 31 MORE TO GO!

John Veninger

Make sure you checked the valve guides.

RyanPerrella

I am checking the valve guides for play, I install a valve and hitw he top of the stem going into the guide i can check play, i guess it shouldnt move more then 1-2mm considering it will be allot less with normal valve guide lift as its extended about 3x farther then it would be when its actuated by the cam.

What about the valve face, is what i have correct in that the one main ring shows up as described earlier.

I should take some pics, i will do that ones everything is properly cleaned up.

Thanks again guys

RyanPerrella

valve guide wear is measured at 10mm lift and shouldnt be out more then 0.8mm