Valve Guide Replacement

[Targa Me]

On the difficulty scale of 1 to 10, 10 being the most difficult; how hard is it to replace worn valve guides on a 3.2?
I understand if some one has little or no experience, a tune-up can be quite challenging. Although I am not an expert, I have successfully performed major tune-ups, brakes, wheel bearing, automatic transmission rebuild (non P-car), water pump, timing chain...etc. I have never attempted a valve guide replacement on a 3.2 P-car.
Can this be done with the engine in the car?

let me know your thoughts.
Thank in advance.

[village idiot]

Valve guide replacement is something your average home mechanic will not be able to perform. You will have to remove the engine and disassemble the top end in order to have access to the guides.

I am at the same point as you. My car smoke quite a bit and though it runs great, the smoke is annoying and embarassing.

I bought a complete set of used heads from another member here and sent them to Henry @ Supertec to be rebuilt. I just have to work up the guts to drop the engine and actually perform the necessary work to replace them.

[cgarr]

Engine out to remove the heads. If you have never done it, it would be about a 10, remove old guides not that hard, thread the top, install bolt, drill for relief, drive out with air hammer, check bore, cut new guides OD for proper fit, install with air hammer to proper depth, ream to 9mm, hone, cut seats 3 angle, lap valves to check fit, pressure test. Repeat 11 more times......

[Zeke]

I think guides only is doable for the home mechanic with considerable skills and equipment. but that's only part of the story. Then the seats have to be cut and the valves dressed. A rebuilder will bead blast the heads and check for cracks. They will also be able to tell if any seats need to be replaced. Same with studs.

I think for all that you get for a grand is a good investment in that they are including the stems in the cost. New valves may run higher for the valves themselves, but the fitting is part of the base price.

[Wil Ferch]

Ream...hone is only one of many critical steps ( along with making sure they don't fall out !)....remember too that the valve guide ID is tapered slightly too, to match the tapered profile of the valve stems. Plus you have choice in valve guide material. Silicon bronze(?) from US sources is currently preferred over factory????....any extra comments here???

[Rodsrsr]

If the guides are worn (which they probably are on a 3.2) you will need to remove the engine and dismantle the top end as already stated. DO NOT just send the heads anywhere, be sure to send them to a machinist who is familiar with the Porsche air cooled engine. You may also discover other problems as well. This is a very complicated and time consuming job and there are many areas where you can go sideways if your not familiar with these motors. I just did this very job on mine along with new cams (20/21 ) and discovered many other problems such as several bad valves, stretched timing chains, worn ramps, ect... you get the idea. I was fortunate to have help from Steve @ Dejung Motorsports who put it all back together for me. Nothing like a fresh 3.2! but to answer your question on a scale of 1-10 definitely a 10.

[LakeCleElum]

Sounds like you are a smart guy and have some experience. I say: Drop the engine youself, pull the heads and send them out. Depending on mileage, it's a good time to replace rings, seals, chains, ramps, etc.

[Grady Clay]

Reconditioning the cylinder heads is the single most important operation affecting performance. Done correctly, the heads will perform properly for a very long time.
If done haphazardly, they don’t work well and will have issues relatively soon.
This is not ‘back-yard’ stuff.



There are three critical issues:

The new valve guide must have the proper press-fit into the head. This means the new guide must be straight, properly finished and undamaged (no nicks, dents, etc.) The bore in the head must be properly finished and straight. The combination of guide and head must have the proper interference fit. Too tight and you break the head. Too loose and there is poor heat transfer to keep the valve cool and the guide can come loose. Of course the guide must be the proper material.

The bore of the guide must have the proper clearance for the valve stem. The bore must be straight and smooth. This is not possible with a drill or reamer. Only honing can get the bore straight. You must be able to measure the bore at individual spots, not just a ‘shaft clearance’.

Finally, the valve and seat must be properly cut, ground and lapped together. A ‘3-angle’ (or more) cut is necessary. The seat must be close or at the perimeter of the valve. The seat must not be low in the valve seat. Everything must be symmetrical.


The heads should be media cleaned. Of course the head cannot be cracked or damaged. The valves must be in excellent condition or new. The springs need to be measured and inspected. The spring ‘installed height’ needs to be set. The proper valve stem seals need to be installed. The sparkplug threads need to be inspected and repaired as necessary.

With the heads in your hand, now is the time to replace all the exhaust studs (and intake occasionally). Repairing broken exhaust studs is a pita in the car. It is easy at this stage.

If you intend to twin-plug your engine, now is the time.


All this takes the correct tools and very high skill and experience level.
There are quite a number of good vendors who can do this work.


Yes, you can ‘back yard’ this but you probably won’t be happy with the results.
There are some Pelicans who take exception to my concerns.
Let them argue their point.

Best,
Grady

[Targa Me]

Right now the car is not smoking but the valves are a little noisey on a good hot day. So I'm just trying to get my bearings straight as far as my plan of attack.
Thanks for the info Gentlemen.

[Rodsrsr]

It may only need a valve adjustment. If the car is not smoking and doesn't burn oli than the guides are probably still good. What made you decide to do a valve job in the first place? Low compression or bad leak down numbers?

[mkc1962]

As were on the topic....and I havent seen many recomendations on any other posts. Does anyone have recommended machine shops on the East coast? or for that matter anywhere else in the US. As in, expereinced in doing Porsche head work, and that folks here at pelican can vouch for the quality of the workmanship.

I know none of my local machine shops would have a clue.

And IF owner does all the dis and re-assembly what would be some ballpark worst case prices to have 6 heads done? Last set of small bleck chevy's I had done was about $500 for both.

Mines still running great and going about 1000 miles to the qt, so no where near any work that I can see, but just curious.

[Grady Clay]

I agree with Pelican Rodsrer, do some diagnosis first.

Have the valves been adjusted?
If so, have you tried ‘just tight’ on the 0.004” gauge?

What oil are you using?
How hot is the engine on a “good hot day”?

The catalytic converter will burn excess oil – to a point.
Does it smoke at all when started cold?
What is the oil consumption?
What do the sparkplugs look like?

I would do both a cranking compression test and a cylinder leak test.
This will give you a better idea of what is inside.
Please report back.

Best,
Grady

[Grady Clay]

Mike,

Yes, you can disassemble the heads first.
Keep all the pieces with their original location.
It is best to ship the heads assembled again.


You want the shop to assemble the heads.
This way the valve spring heights are set correctly and the valve stem seals are installed correctly.
Each valve is custom seated to one particular port.

Best,
Grady

[RSTarga]

Ask my local Porsche dealer who back in 1981 managed to crack 3 of my heads while pressing in new guides and then charged me for 3 new heads!
This is best left to experienced personnel.

[Drisump]

Originally Posted by RSTarga

Ask my local Porsche dealer who back in 1981 managed to crack 3 of my heads while pressing in new guides and then charged me for 3 new heads!
This is best left to experienced personnel.

Wow, I imagine there is much more to the story but.... a Porsche dealer eh? BTW, to Targa, I agree with Rodsrsr and Grady, why do you want to fix something that doesn't seem to be broke?

[mkc1962]

Grady,

actually I was referring to the part about removal and reinstall of overall heads, not so much disassembly of actual springs/valve and keepers.

any recommendations for some good porsche qualified machine shops?

[Targa Me]

Originally Posted by Grady Clay

I agree with Pelican Rodsrer, do some diagnosis first.

Have the valves been adjusted?
If so, have you tried ‘just tight’ on the 0.004” gauge?

What oil are you using?
How hot is the engine on a “good hot day”?

The catalytic converter will burn excess oil – to a point.
Does it smoke at all when started cold?
What is the oil consumption?
What do the sparkplugs look like?

I would do both a cranking compression test and a cylinder leak test.
This will give you a better idea of what is inside.
Please report back.

Best,
Grady

Valves are properly adjusted.
Oil is Castrol 20w-50
Engine temp on a really hot day will run 230 degrees approx.
Engine does not smoke at all when starting.
Oil consumption is about a qt every 1500 miles or so.
Plugs are white...i.e. on the lean side.
50k miles ago the compression was 171 / 170 across the board.

[Grady Clay]

I would say that you don’t have a problem.
Drive and enjoy.

This is still a good time for cranking compression and cylinder leak tests to establish a ‘baseline’.

Best,
Grady

[Targa Me]

Thank you for thoughts, Gentlemen.

[88911coupe]

Competition Engineering did mine last summer. Worked appeared flawless and has run perfectly since I put it all together. Well regarded shop.