964 head/valve job with 993 RS'ish valves

[konrad911]

Hi all, I'll start that I'm based in middle of nowhere in Poland (Europe) and doing most of the stuff by myself with my cars/engines.

The thing is although I do have a small lathe and a mill in my garage, I won't replace the valve guides or valve seat rings on my own as I lack the necessary tools and buying them for a single job, maybe two would not make a financial sense to me.

I went to a local machine shop and asked for the works I'm planning, and they said no.
I went to a well known machine shop in the capital of Poland, asked few questions, and they... got confused.

Tried to search the forum and found just bits of information I need for the work on my heads.

The story is as this, I have early 964 engine and the valve guides were worn out.
At the machine shop it appeared that also valves and seats are already out of specs, so I need to replace.

The 964 and 993 OEM valves got ridiculously expensive (almost $300 for single valve).

Fortunately just across the border there is a German company called Schrick. I used their camshafts in previous build that did not need the head job. It appeared they have 993 valves close to the 993/964 RS specs (52mm intake and 42mm exhaust with 8mm stem like in 993). Valves are like $60 each.

So I got two valves for the first head work, guides from 993 and went to the well known machine shop. The 964 valve seats are to small, so I ordered the 993 RS seats.

Intake Seat: OD 53.50mm / ID 47.15mm
Exhaust Seat: OD 47.75. / ID 37.82mm

(measurements might not be super accurate).

The well known machine shop told me that I need OEM seats, as they will not use anything else unless I won't need a guarantee for the works, that's why I got the 993 RS OEM ones.

Q1: Do you know by any chance the tolerances for the head to machine the place for the seats? I found in the internet the tolerances for stock 964 ones, but these are obviously less in diameter.

Q2: The Intake seat is ground by factory with 2 angles (45 deg and maybe 75?)
The exhaust seat is ground by factory with only 45 angle (EDIT: 2 angles as well)
According to the 964/993 manuals these should be ground to 3 angles (30deg/45deg/75deg). (EDIT: Which means the top part only needs to be machined at 30 deg to create a seat of width 1.5mm +/- 0.1mm that would seal the valve).

What worries me is the well known machine shop told me they will not grind the seats after install, maybe barely touch them - this seems to be in contradiction to the Porsche Manual.

They they told me also the valve seat hight (46.0 +/- 0.3mm) might be hard to achieve...

I'm worried. Not sure if they are capable of the job.

Obviously I will need to enlarge also the ports around the seats after installing the seats from 993RS in 964 heads, right? Any guidance here how to not make things worse?

Many thanks for any comments.

[konrad911]

So I paid a visit to the machine shop today with the valve seat rings and supporting printouts from the Porsche Manual. Slowly I explained what to do and how and to heat the heads to 200 deg Celsius as in manual. There is a big chance that I will only need to replace the intake valve seats, which will lower the cost in parts and labor.

While there I weighted the Schrick valves and compared with stock 964 ones.

The difference is -4grams for the intake and -14grams for exhaust compared to stock.
This is nice, especially intake is 3mm bigger in diameter.

I will be left on my own though with porting the intake port around the throat just below the new bigger intake seat - can someone please chime in and guide me how not to do it all wrong please?

[winders]

Well, first I would send my heads to someone that does not need hand holding to do the work. That shop would also know how to do the porting…

Here in the USA that shop would be Xtreme.

[stownsen914]

Agreed that you want to make sure the shop doing this work is familiar with Porsche 911 heads. It will potentially save you a lot of grief down the road. Understood that your options in Poland might be more limited, but in case you need recommendations I'm sure one of our European forum members can chime in.

[konrad911]

I wish I was based in the US :-)
Well I see it in two ways. Financially - either way is getting damn expensive. My local currency ex rate to USD/EUR/GBP sucks. Then add duties and taxes and shipment and it’s over twice the US price at least - been there, done that.
I have two hands that are not afraid of work. Some tools, some knowledge and some experience.
I haven’t ported the 911 head yet, therefore before I touch it, I want to ask. So I asked :-)
I’m sure companies like Xtreme or other well known vendors were also at this point some time ago.
I don’t want to build a competition head, but as I’m already there, why not do something good to those heads.
Appreciate your guidance.

[Neil Harvey]

Nothing you have been told makes any sense. My advice is to find another shop that does this type of work. It does not have to be a "Porsche" shop either. Any good automotive machinist knows what has to be done. Then it come4s down to specifications that can be found. Hopefully, you will find a place that can give suggestions of what can be reused and why. Eg., if the valve stems are undersize, the guide can be pin fitted to allow for the difference. We run a lot tighter than what the factory calls out. Material, oil all have changed since the spec's were written.

There are many critical areas to be aware of. Some are never considered.

In your case, head work all starts with cleaning and crack checking. The Exhaust port requires some attention. Often more common than not, the insert is broken with chucks missing. It becomes a decision to continue with what you have, repair them or find replacement.

Then the guide is the first part to change. The seat insert and its housing bore all get machined concentric to the new guide. Replacing the guides will always give a slight change on concentricity to the seat. The seat insert bore is machined after the guide is fitted, to the size of the valve head plus any added for the top angle. Just make sure the interference is the right amount or you will be in serious trouble.

Then the seat angles are cut to what ever you want. 30/45/60 is common for street engines but you may consider difference angles all based upon the back angle of the valves. Exhaust seats often gain some flow by having a radius on the bottom. Flow testing shows what works best.

The 964 has a spec of how much the valve sticks out on the spring side. This is to ensure the rocker geometry is correct.

As for seat insert material, some have better transfer heat rates than others. For steel valves, you do not have to be too careful, but a good aluminum nickel bronze insert will work the best. These are available but you may need to do some machine work to make them fit. Remove the seats first, measure then bore and add the interference you need.

Need further assistance and advice, PM me. I'm happy to help.

Good luck.

nh

[mikedsilva]

Originally Posted by Neil Harvey

In your case, head work all starts with cleaning and crack checking. The Exhaust port requires some attention. Often more common than not, the insert is broken with chucks missing. It becomes a decision to continue with what you have, repair them or find replacement.

Hi Neil, if the ceramics in the exhaust are cracked and missing (common), can this be repaired? How? I was always told you have to replace the entire head... I ask, as I have a set of heads here; 3 with decent exh ports and 3 with terrible ports... would be good to be able to have them repaired.

[konrad911]

Many thanks Neil for the input.

Obviously they are doing a lot of regular water cooled daily cars, trucks and so on… for over 30 years.

Aircooled 911 is still rather exotic in Poland and the oldtimers/youngtimers market is in it’s beginning.

Therefore there is a very limited access here to workshops with serious experience.

I could send my heads to a German vendor obviously, but then again: #1 price #2 myself I’d learn nothing, and I want to learn and get experienced If this requires trashing one 964 head, I’m sure I’ll find one to practice on.

I’ll leave the machining - guides, valve seats, to the machine shop, as they are doing a LOT of that for STOCK cars.

I’m left with a bit of magic - porting the head to a bit more performance due to bigger valves and seats.

That’s where I hope to get a bit of enlightenment form the forum gurus

[safe]

You don't need a Porsche expert machine shop, only someone who are interested in the work. Preferably a performance shop that's not swamped by work on commercial engines (those will always push your work to the list).

[Neil Harvey]

Originally Posted by mikedsilva

Hi Neil, if the ceramics in the exhaust are cracked and missing (common), can this be repaired? How? I was always told you have to replace the entire head... I ask, as I have a set of heads here; 3 with decent exh ports and 3 with terrible ports... would be good to be able to have them repaired.

Mike,

We do have a special way to repair the ports. Its time consuming as it has to be applied in layers, then go through hours of curing/heating. The cost always is about the amount of damage. However, the cost is not based on the time. The majority of the time is ambient curing and over time. The labor is the initial cleaning, removal of any carbon, then applying each "coat" of the material.

[konrad911]

Ladies and Gentlemen so I got my head from the machine shop with guides removed and new valve seat rings fitted - now I'm on my own. They flow benched the stock head before doing any works and will do same after I give them back the head when I finish porting it on my own.

I took some photos from different angles for ease of discussion.

Obviously changing the valve from 49 to 52mm and replacing the valve seat with 993RS one introduced a step in the port, just below the seat.



So obviously I need to enlarge the port to the diameter of the ID of the seat - any suggestions how make it most effective - going straight down as factory did with milling tool I expect will not to be the best option?




The area around the valve guide needs some tuning, and while on the "attack" side [top of the valve guide hole in the photo] my idea is to create kind go knife edge that gradually widens into water drop shape, not sure what shape should have the back side of that area [area closer to the exit of the port - below valve guide hole in the photo].



As I mentioned I don't want to make it worse than it is, that's the biggest success criteria :-)

There are "stitches" and porosity that I want to smoothen with sanding tools and sanding paper.




How the "lip" should look like on the shorter wall and longer wall (the one that has valve guide in it)?






There is a "bump" on the almost 9 o'clock that I will flatten as well (blurred area / out of focus) in this photo.


Appreciate your help and guidance and hope this will be also useful to the rest of the community.

For reference, these are the early type 964 heads (MY90) without the sealing ring.

[winders]

There is a reason one should get a pro to do this work......

[917_Langheck]

Or grab the air hose, the dykem and die grinder and become a professional like so many before - you know, the pros dont automatically start out as pros and they dont always have a seasoned eye looking out for them; they just get stuck in and figure it out.

[konrad911]

I'm not afraid of the job, of the trial and error (even though I might need to sacrify a head). The pros = sending the heads to the US or Germany, which means skyrocketing the budget (anything I buy in the US ends to be twice the US price in the end for me - when I add all the customs, shipping and taxes like VAT, that don't exist in the US [23% on top of everything - parts+shipment+duties+services].

I could not find experienced machine shop here in Poland for such job. They do lots of Subarus and Mitsubishis, and Supras though (add more boost) And when you hear... "we give no guarantee on the job results" (porting), this really challenges me to do it on my own.

So when not giving it to the pros, but willing to do it on my own - what are the does and don'ts here?

As I said - not building a competition head, just while there I want to get things slightly better.

Thanks

[winders]

If you have no idea what you are doing, it's more likely you will make the heads worse than you will make them better.

[konrad911]

Originally Posted by winders

If you have no idea what you are doing, it's more likely you will make the heads worse than you will make them better.

I have some idea, I'm just asking for better ideas, more experienced ones.
If there is something wrong in my ideas already posted, please let me know - I'm happy to get more understanding on that subject.

[winders]

You're just guessing....and I would be too. I don't know of any sites with detailed information on porting 911 heads. Doing it well requires knowledge, experience, the right tools and may iterations. Most people that go through this process don't just give away their intellectual property. It cost them time and money to obtain.

Are you doing anything else to the engine that would suggest these valve sizes are the way to go? From what I do know, engine configuration and use case determines air flow needs which affects valve and porting choices. If you aren't increasing the air requirements of the engine with improved intake and exhaust systems, bigger valves and larger ports are going to hurt, not help, performance.

[safe]

Originally Posted by konrad911

I have some idea, I'm just asking for better ideas, more experienced ones.
If there is something wrong in my ideas already posted, please let me know - I'm happy to get more understanding on that subject.

I "ported" my 964 heads. I just removed imperfections, blended any steps towards the seat, some sharper ridges on the inner short side of the bend a little smoother. Narrowed the valve guide boss a little. Port blended the intake and exhaust to the manifolds.
It definitely didn't get any worse! As long as you don't alter the port dimensions, just smooths it out you can't go wrong.
After that you need a flow bench.

A company here in Sweden offed to do the above and claimed it made about 10 hp.
I decided to do it myself due to logistics and time.

[konrad911]

Thanks safe, these are my observations as well, but as I did not work on 964 head with a bigger valves, just wanted to ask before I touch it.

Winders - there will be few other things changed as well. Both on induction and exhaust. This is a street car, so I’m not targeting max HP at open throttle all the time, more a nice torque curve all around.

In terms of bigger valves will hurt the engine - well if the flow is better, I cannot see how this could hurt the engine performance.

I know for sure if the valve goes to deep into seat, this will restrict the flow rate, that’s why there is the +/-0.3mm tolerance on the height of the valve relative to the spring seat in the head.

Radius cut seats and back cut on the valve will help as well for a better flow.

But these are things I know, so I’m not asking. Same for the induction/exhaust… The intake port is obviously one of many parts that add up, one part I did not touch on my own yet, and I want to do it on my own as well. Easy as that :-)

As of protecting IP/research and so on - I completely understand that, and I’m not asking how to build a competition head right?

It’s just there might be things that are not well kept secrets that I’m not aware of and someone from the community can enlighten me and others.

If I was targeting racing or so, then most probably the billet head would be the choice, but also there will be a budget.

So safe’s comment is a good starting point.
What else?

Thank you

[917_Langheck]

It is not rocket science based on state secrets. Plenty of info out in the wild, even in the library, on how to do this, because it's been done since motors have been manufactured. You can even build your own flow bench to measure your work and ensure the heads are flowing within the same baseline of each other.

At a minimum blending and smoothing the transitions is what you'll want to do. It's your motor, so have fun.