Hi folks!

I'm about to have the engine rebuilt in my 997.1 Turbo (2007 manual coupe). Long story short, it's leaking compression past an exhaust valve on one cylinder -- unclear why, have to tear down to find out. Given that it's got almost 80K mi on the engine, I planning to just do a full rebuild and refresh everything. I'm looking for advice on cost effective and longevity promoting upgrades while in there.

Mods right now:
-Sachs clutch upgrade
-Tune from Sam at ByDesign
-Kline catless exhuast
-DO88 turbo inlet tubes
-Coolant pipes pinned
-Sharkwerks coolant elbows

Current rough plan:
-Upgrade to 3.8L mahle pistons and sleeves
-Replace rods with pauter or carrillo
-Refresh heads, valves, replace / machine anything that looks troublesome
-Replace other wear items: Replace all lifters, replace chain tensioners, replace timing chain rails / guards
-Pin cams
-Keep stock crank, but split case and refresh bearings
-Keep stock turbos

A couple questions:

(1) My goal is a bit higher than stock power, but nothing crazy. Mainly, I want engine to last another 100K mi. Is upgrading to 3.8L an unwise choice? Idea would be to get same power at slightly less boost, more cautious tune. However, if I go up to 3.8L, are there a bunch of other things that should be upgraded to support? For example, the stock intake and exhaust manifolds were designed with 3.6L in mind -- will they be suboptimal for 3.8L? Would it be wise to upgrade to gt3 crank / oil pump when moving 3.8L? Or is stock crank fine at this displacement?

(2) Anything else I should consider replacing while in there that I haven't listed? Engine is at 80K mi. What else is typically worth replacing when splitting the case on a mezger? I've read around the forums to piece together the plan I've laid out here, but I'm curious to know to hear from folks with more knowledge.

(3) For pistons, sleeves, and rods, what is current preference? Do we like carrillo rods with mahle pistons and sleeves? Or are there better options I should be looking into? Any specific brands / parts to avoid?

Thanks for any advice you can give!

 

I'd talk to an engine builder before you make all kinds of plans. They know what works well for your goals and budget. Different builders like different things. 80k isn't all that high of mileage for these cars too. There is a 996tt with a turbo upgrade running around with 500k miles. You could just repair your car and throw some rods and heads studs in there and you would be good. Pauters will go in without splitting the case. If you want to really spend some money I'd call here: http://evo-spec.com/

I have a 996tt with Pauter rods, 12mm heads studs, 997 stock pistons, 997 lifters, and k24 billet turbos. The thing is great with that setup.

 

Thanks! That's good to know -- yes, if the stock pistons and liners look good I may go with your approach. Do you think the 12mm studs were necessary in retrospect? Or I guess good to just have the extra peace of mind? The engine builder has a bunch of experience with mezger gt3, but not so much with turbos. I went with a local builder rather than one of the big shops to save money -- hopefully I don't regret it later. Thus, I'm making sure to do my own research

 

budget? how are you using the car? power goals?

 

The 12mm studs are great but required machining I had to go out of my way to get done. My failure was related to a blown head gasket that let water into my cylinder. I wanted to be able to hold 900 hp or so. You can do 10mm but run more risks. Some guys are able to get the stock studs to hold quite a bit of power.

 

Thanks for the advice! My budget is around $15K. Car is daily driver that I daily drive pretty hard, and take on canyon runs each weekend. Want engine to last -- so longevity is a priority. My power goals are modest. Right now, car has a tune, clutch, and catless exhaust -- nothing else. So I'd be more than happy with 600hp or less at the crank.

 

If you do rods and one of the 10mm stud upgrades that will get you 700-800 if you would like easily. If you split the cases to change out all of your bearings that is going to be quite an expensive option, but on the other hand it is nice to be 100% fresh and rebuilt, so you will have to make a call there as this may push your budget. For your needs a stock crank and oil pump are good. Your stock pistons and liners are also fine. A 3.8 piston/liner kit is nice for a bit more torque, up to you. If you get a CP kit with iron liners it will be cheaper and strong, and the Mahle kit with Nikasil liners is pretty pricey but really nice. Evoms guys say the Nikasil liners are good to 1000hp or so, that goes for the stock ones also.

So I'd suggest:
Base: Stock crank and oil pump good to 1000+ hp. Split case with new bearings? Your call. Depends if you want to keep the car for forever.

Rods: Pauter if no split case.
Pauter or CP if you split the case. Both are good, you must clearance the oil pump for CP rods.

Pistons/Liners:
CP pistons/ iron liners: Strong and good to 1200hp, not too expensive. Might add good value to your car.
Mahle pistons/ Nikasil liners. Nice kit but expensive.

Racewear head studs 10mm is what I would go with over the stock units. 12mm studs are nice but a nightmare to install.

Stock cams are fine.

 

Thanks! That's very helpful advice. I'm leaning towards 10mm head studs, CP rods, split case for new bearings. If stock pistons/liners look worn, Mahle 3.8 kit. Worth letting them do their magic on the stock oil pump to improve flow? Or is that likely not worth the money? Builder has someone who says they can polish the internals or something like that to improve oil pump flow. Never heard of such a thing before this.

 

Might be possible to improve the flow a little. I wouldn't spend much on it. $200 bucks.

 

Just out of curiosity, what were the symptoms of the compression leak? And what made you look for that, did a Durametric scan show something?

 

My suggestion is to reach out to Sam from ByDesign, he can get the right kit for you, for your needs.
He also works closely with John Bray from EvoSpec - where I got mine from (through Sam) and who blue printed it for me.

I went to a full 3.8L conversion, and would highly recommend it. Where it really makes a difference is the low end torque - which oddly no one talks about.

Costs for materials may have gone up recently, so would expect the costs to have changed, maybe even substantially, however in 2019 the full engine internal kit was just under 9k USD.
The real expense is the service and small parts cost of your mechanic. That is the most important factor of the entire exercise. FIND A GOOD MECHANIC TO DO THE WORK. The alternatives will drive your costs up substantially and also potentially increases the risk of things going sideways, sometimes after the build is complete.

I wouldn't worry about the intake and throttle body etc. They are highly recommended for better response, power etc. but those are bolt ons that can be added later. I have larger turbos (68mm VTGs), larger air hoses, y-pipe, throttle body, light weight pulleys, 1300 injectors, etc. etc.
I'm running 93 octane and the injectors were a pain to diagnose and get just right with the tune - car had developed a random stall. But we sorted it out.

BIG SHOUT OUT TO: Todd from Protomotive who has been a genius with the COBB tune. Getting it just right and diagnosing many little gremlins with the custom build.

Also I'm running a decat exhaust thats 3" ... all of these items add the the responsiveness and power through the entire curve. The thing is a BEAST!

Lastly I'm also running a meth kit - which was a pain getting it just right, primarily as we are using solenoids for safety and needed to wire it in, in a rather bespoke way - so some experimentation needed to happen there.
We're still finalizing the tune, to get it just right. Essentially coding it that non-sport mode it will run fine with meth off and sport mode on will require meth.

Good luck with your build!
Keep us posted.


Here are my internals from EvoSpec.

 

Yes I would go for the CP piston setup with the Iron liners. You will be set to make over 1000 hp easy.

 

On these sorts of higher HP builds, do you need to factor in beefing up the transmission or differential or anything?

 

The 997 transmission will hold it. A big time clutch of some sort is needed.

 

who did your motor build - I’m interested in a simple pauter rod and 10mm stud build on my 997tt, inorder to make a nice 1000whp?