I am rebuilding my engine a 2.0 from 76. I took the heads in to be reconditioned.
The machinist told me that the valve stems needed replacing, the valves needed regrinding and the seats machined. He said this would be no problem.

He know tells me that the new valve stems are not at the same angle as the originals and after machining the seats the valves sit too low in the valve seats. He says new valve seats are required
As you will understand I am not happy especially when he reassured me that he could do the job no problem.

Is this guy incompetent dick head or is this a common problem,?
Appreciate feed back before I go to the shop on Wednesday.

Well, the valve guides may have needed replacing, the stems, not too sure I would do that versus getting new valves.

If he ground the seats to low during the machine work, you may need a new set of seats now, and I bet that it depends upon the condition of the heads.

Rich

Go pick up your heads tomorrow morning. Please, before he ruins them.

His terminology for guides is stems. Read his post that way and it makes more sense.

If he put in new valve guides and reamed them out at the wrong angle, then tried to fix his error (he jigged it up wrong) by grinding the valve seats again, I would have to agree.....go get your heads.

Now you need new guides, again, and new seats.

It's not the end of the world and the heads are not ruined, you may just want to find a shop the knows how to deal with type4 heads.

Contact mittelmotor in Germany, they may be able to suggest a good machinist in Sweden, or look at the german look forum on,shoptalk forums and ask there...again to get a name of a shop that will treat you right.

Thanks for the input, I am at a real disadvantage as my knowledge of engines and rebuilding is very limited...in other words I dont know shit.
And Yes I mean guide not stems sorry for the mistake. I will take some photos and post them later in the week until then I will try to stay calm and hear what the guy has to say.

Thanks again

At this point, I'd question if you're getting the truth into what the machinist actually did to start this issue. . . but is sounds like when he replaced the guides, something went a little off replacing /pressing in new guides and the valve guide stem hole is no longer in the same 'plane' as it was before. . . meaning the valve is no longer parallel and perpendicular to the pre-existing valve seat. . . The machinists answer is to recut the old seat to accommodate the valves new orientation in the head. . .
Bad for a couple of reasons, the one you currently have with the valve now sitting too low in the head chamber, but more important, if the amount of variation necessitates re cutting the seats excessively, the face of the valve stem will no longer be in the designed location and will have a modified contact with the rocker arm. .
I suspect the machinists answer to replace the seats is what he needs to do to get you out of his shop, and it won't be until you put on the rocker assembles that you'll notice any other issues. .
Are all the valves having the same issue or is it just one or two. . ??

The first clue that the shop is not well versed with T4 heads was when they did not insist on replacing the valve seats as a standard service of the rebuild.

Get your heads and find someone who knows T4's

Ham Inc is one of the most knowledgeable people here on 914world. I don't believe he works on old heads anymore but he did the head work on my engine I would trust no other.

AFAIK He doesn't work with your head as you need it. Still, please do not let that shop do anything else. I would pay and leave as the price of driving later with a dependable car. Good luck!

Thanks for the kind words!
We do still work with used 2.0 914 heads, no bus heads. And they have to meet the criteria outlined in the article this link takes you to. Last year only 3 pairs did.
http://www.hamincgroup.com/blog/porsche/91...-service-policy

Our new 2.0 914 F.I. replacement heads are keeping the T4 work prominent in our shop, otherwise you'd hardly know we work with them anymore.

http://www.n56ml.com/corvair/valvejob.html
The problem of valveguide od to seat concentricity is the same for most manufacturers.
A detailed inspection will discover those errors,pita and costly.

Click to view attachment

So true,an overheated head will always be prone to dropping the seats.
I find it incredible anyone would consider flying an engine without new valves and seats.
Staking them is a good measure that if done correctly,is a margin of durability.

I appreciate the agreement, but have to point out that staking is not an accepted method of o.e. seat retention in T4 heads.

The #1 contributing factor to valve seats dropping out of these (and most aluminum heads) is tired valve springs. All other issues are contributory but secondary.

A vicious cycle that comes into play as the engine ages and gets fatigued, losing power over time. As a result it's revved higher between shifts to compensate. While this is going on the springs are fading and no longer able to control the valves, especially the heavier intakes. They literally pound the seats like a hammer, loosening them. This is why intake seats drop, but rarely exhaust seats.

Heat plays a role, but it's more an issue of the aluminum softening as it heats allowing deformation of the seat bore, than actual expansion of the bore.

Excessive valve lash magnifies the issue by adding to the pounding, this is why hydraulic engines suffered this problem in spades with these engines.

Yes,the relaxing of strength as a consequence of elevated temperature,both the spring and alloy head.

Click to view attachment
A RR Phantom III head.Staked.
Threaded valve seats is another of RR's innovations for reliability.
An expensive method of machining,but certain.
Not sure if any round engine makers made similar seats,anyone here with P+W experience?
http://www.sl113.org/forums/index.php?topic=8028.0
https://www.roushaviation.com/repairstation...nprocesses.aspx
Incredibly expensive process for approval.

Yep, as soon as he even considered keeping the stock seats, his credibility was compromised.

http://www.914world.com/bbs2/index.php?sho...4258&st=100



http://www.flycorvair.com/
Built as per these standards,a reasonably economical aircraft engine.
https://flywithspa.com/product-category/corvair/
There is a good crank here,not cheap,worth every penny.
Careful up there.

to offer a cost effective solution to this guy, can he post some pics to allow you to decide if you can help him, then have him ship you the heads?

That may be a great way to get him out of this situation without too much pain.

If I was the OP, I would pick up the heads, pay the guy, take it as lesson learned.

Then decide what the next step is based upon cost....it may be easier, faster and a better deal all around to buy a set of built up heads from Len/LN Engineering/Type 4 store....or wherever you can buy them now.

Not sure if that is practical, but it might be something to consider.


Rich

I think the cost of shipping to the states and returning the heads to Sweden, that might be fixed beyond repair, would be cost prohibitive. Easier, faster, less expensive to just buy a ready to go set. No telling what import duties might be given the tax structure in Sweden.

With all due respect to Len, there is a fairly large community of Type 4 builders in the EU, which can be tax free for him to work with.

It was an idea for him to post pics of the head, just to see if they can be fixed properly at this point.

Rich