PZB993

Does anyone have any real world experience with the 9m billet heads? I'm planning a top end rebuild and this sounds like a good option. I know it's a large chunk of money on top of the rebuild labor, but I figure there's some savings on all the head work. Just bolt up the new system (heads, valves, cams,).
Thanks

pp000830

What prompts you to do a top end rebuild?
Andy

IainM

I take it you’ve read the several threads on this forum?

95_993

To really go down the path of 9M heads, you need to think about the whole motor as a system and you will need to make changes to the fuel injection, mapping, cams, etc, etc.

Beautiful pieces of machine work, but the intended benefit comes from much greater volumetric efficiency due to increased flow from bigger valves, ports, etc. That can only be accomplished with additional increasing the ability to handle the greater volume in and out of fuel and air. Quite a few threads and I am sure Colin at 9M can walk you through things in far greater detail.

IF you're doing a top end and want a little more than just stock, having the heads machined for bigger valves while you're in there, add RS cams , new mapping, etc. You'll know better once you're in there looking at the valve seats, cams, etc. if there is putting on the cams, you're in for the cost of cams, grinding of rockers for parallelism anyway. If the valves are out of spec and the valve seats are shot, again you're looking at the cost of replacing those as well. All that said, IF you're going that far, upgrading to the RS components isn't that big of a bump.

This is why it's referred to as the " slippery slope".

PZB993

I know this isn't a scientific answer, but here's my thought process: The car has 175k miles on it with no record of a rebuild. It's harder and harder to pass smog each time. Smokey exhaust more frequent. I'm having a LWF installed so an engine & trans drop is already happening. And maybe the biggest reason is peace of mind. I worry about a failure more and more these days when I'm on multi-day rallies 8 hours from home or more.

I've read some, but they were all from a long time ago and wanted a fresh take after some folks lived with it for a while

I like the point you've brought up about upgrading to RS components. Here's where I'm stuck. I'm anticipating to have to replace all listed parts. (keep in mind the numbers I'm about to rattle off aren't gospel) New valves, guides, and seats +/- $3000 Labor $1500 Total $4500 for just this portion. Add Cams $1200. Add rocker grinding $? Now I'm looking at a price tag of around $6000 to rebuild existing heads.

The package Colin quoted me is $10,864, but this is with SAI ports. It should be about $400 cheaper without the ports. 9m billet head x 6, 9m Intake valve x 6, 9m Exhaust valve x 6, 9m Valve Spring set, 9m Sport Camshafts, 9m Rocker shafts, ECU chip

So for around a $5000 difference you get 20 to 30 HP. Outside of a supercharger (not interested) that's the best bang for the buck in air cooled HP gains.

The top end rebuild was partly justified by some slippery slope rationalization of getting a LWF installed.

I also enjoy taking the car to new levels. Back when I started my rally/safari build I was faced with some large bills and hurdles to overcome that people didn't agree with either. Not in a negative way, just didn't see my vision. I really appreciate all the input and am open to better options. I'll ask my shop for the price to do the "stock +" RS components route you suggested so I can compare actual numbers.

This car has been my hobby for over 6 years and I want to keep it healthy for many more to come.

95_993

I totally understand.

nothingbutgt3

I have no experience as mechanic, I opened the engine of the submerged 993 and I found heads in perfect shape, valves were perfect, spring, etc, only the exhaust valve guides had some play, and only then I searched for infos and I found out that this is a common issue on our engines.
The rectifying shop cdisassembled the heads, cleaned them, checked them, reworked the valve stems and the valve seats where they mate each other, without removing the valve seat inserts, disassembled the spring, Cleaned them, changed the sealing tuppets, cleaned the in/out ports, and changed the exhaust valve guides with new ones able to resist to higher temperature.
Then I basically rebuild the engine balancing the component, chains, rockets, sprockets, all the bearings and supports brand new, oil pump, etc. And the engine will be basically back with at least the same power it had when new, maybe a bit more.
I don't think all of this, parts + labor, would cost me more than 6/8k.

The other way is a very good one, but I would send the engine to 9meister and let them rework the 3,6 engine to another level.
I think for improvements, one needs to go tk the masters.
If you like to do it by yourself, maybe with some help from here and from a local mechanic, I would just rebuild it.

If you want improvements in performance, I will send the engine to who knows what to do and how, and what not to do. In this case you'll be out of every play.

Both the ways have pros and cons.

For my very first engine I wanted to be present and see and participate to the engine rebuild.
But if I'll ever go for a step 2, I am not sure if it's the case to do the same, it could be not only be very expensive, but also not provide the expected results or even worse, lead to demages.

IainM

Excellent advice.
a friend went down the halfway-house approach of billet heads reusing everything that was serviceable and ended up rebuilding the engine 3 times total before he was happy.
Either stay with Porsches formula (stock) or go all the way with a 9m or other alternative.
this is not a mix & match situation

Bill Verburg

(M heads are great but expensive

I'd just send what you have the Xtreme, be sure to spec the rest of the engine so that they know what needs to be done

Mike J

175,000 miles?? Nice, but you are likely to take that "top end" to a complete rebuild - that is a lot of miles on the rings/chains/sprockets/main bearings/rod bearings/oil pump/nose bearing never mind all the seals etc.

I would not run higher performance heads on a bottom end with that sort of miles, as a minimum check the barrels and new rings. For a 993, it would be prudent to rebush the wrist pins and replace the rod bolts with ARP, given the possible higher revs. Of course, that can be done without splitting the block, but it's better to use a stretch gauge on the rod bolts - not possible with the crank in the car. Now the bill even for just the parts and machining gets much higher, and if the barrels are out of round then there is the temptation to go to a 3.8 .. and on and on ... very steep slope.

I think it's likely not money well spent on just a top end on a 175,000 mile engine .. just my 2 cents. :-)

Cheers,

Mike

John Kleven

CMW also makes billet heads for the 993, I would be curious to see how they compare also?

MarinS4

I spent a LOT of time reading about heads during my Harley hot rod years. Learned a lot about port velocity, valve shrouding and optimizing the combustion chamber. Used that knowledge to build nice stoker Evolution. While it put down healthy numbers on the dyno it really shined on the street with incredible throttle response.

Investing in the best heads possible is money well spent. I kick myself for my pulling the trigger on the 9m’s when I had the chance. Based on the conversations I’ve had with Colin he really optimized the design. While HP gains may not be too impressive I bet the engine really wakes up throughout the power band.

My only word of caution is choose cams wisely. 9m offers some nice grinds but I’d opt for something a bit more mild. You’ll want to ask him for flowbench data. With that you can better chose what’s best for you. WebCam is a great option for something custom. Nothing off the shelf (other than 9m) with have enough lift to make those heads shine.

PZB993

Thank you for sharing your friends experience, that is exactly what I need to hear. Sounds like I need to reevaluate expectations and budget. From what I read it sounded like it was just "bolt up performance". I should have known better. Thanks!

What is Xtreme? I'm assuming a race shop. Where are they and how do you ship an entire engine and trans? Thanks!

I thought the bottom end was supposed to be solid for +- 300k miles, that's what I was reading. My wallet was hoping the case didn't need to be split . I definitely want to do the right thing and will plan to have a large contingency for what the doctor finds when it's under the knife. Thanks!


Sounds like I'm in for some more research before I pull the trigger. Thanks for the insight on the cams.

Moriartyhlms

I agree with Bill on Xtreme. I sent them my heads and they did a beautiful job CNC-porting and installing bigger valves. I think it cost me ~$5k

People may throw rocks, but I think the performance gains from Xtreme’s reworked heads are very close to those seen from the all-new redesigned heads (including their own). And, of course, engine mods need to be accompanied by a fresh software tune.

EckFe1

What about the ceramic port liner on the exhaust port?
You can only port the intake side from what I know.
It doesn't make much sense to install bigger valves or port only one side if you can't get rid of the burnt gas afterwards.