Buckeye19

Hello all. I have been looking for a 964T for a little while and just haven’t found the right car yet. I have been considering buying a non-turbo Carrera and going with some aftermarket internals (Pauter rods and some forged lower comp. ratio pistons) suitable for a custom turbo setup. I know there are a few guys around here who have gone this route.

There are a number of reasons why I think this may be the route to go for me. However there are a few things that I’m not quite sure about which would easily change my mind about this project depending on the answers:

1. What is the difference (if any) in the strength of the 3.6L Carrera case vs the 3.3L turbo case?

2. What is the difference (if any) in the strength of the 3.6L Carrera crankshaft vs the 3.3L turbo crankshaft?

Once the aftermarket pistons and rods are in they should no longer be the weak point. I would hate to start cracking cases or snapping crankshafts if they were significantly weaker then the factory turbo counterparts.

3. Does the Carrera case use the same bellhousing bolt pattern as the turbo? If/when the Carrera transmission breaks from the added power, I would prefer to bolt on a stronger G50/52 tranny and want to make sure this is an option ahead of time.

4. I would assume that the turbo halfshafts are stronger then the Carrera halfshafts, which will probably be the second weak point in the drivetrain. Will the turbo halfshafts bolt up or do the rear hubs need to be changed?

Thanks ahead of time for any insight to these questions that you may have.

-Brett

GrantG

Brett - I'm far from an expert on this topic, however, I'll venture an opinion on your first question anyways:

The normally aspirated 964 & 993, 993TT, 996TT, GT1, GT2, and GT3 all used the 964 block, so I imagine it's mighty stout. Not like turbocharging a normally aspirated 996 Carrera which could spell trouble...

Geoffrey

The 964T engine is essentially the same as the 78-89 930 engine and is different from the 964/993 N/A engine. Both engines have their strengths and weaknesses. Here are my opinions:

1 The cases are similar in design and I would suspect that running improvements may make the 964 case slightly better. Either one will work fine.

2) The 930 crankshaft is a better crankshaft because it is fully counterweighted and is straight. The 964 crank is not fully counterweighted and requires a heavy balancer. Both are good crankshafts and either choice you make will be fine.

3) The 964 engine has wider stud spacing so you run the risk of head lifting moreso than the earlier engines. Conservative boost pressures will go a long way for longevity. You can also get a nice sealing ring design on the 964 engine that will help with sealing.

4) I think the oil pump in a 930 is a better unit made from cast iron and aluminum rather than magnesium. A GT3 pump is better yet

I personally like the 964 N/A engine to be used as a conversion base. You can take the stock pistons and mill them down to your desired compression ratio. These are strong Mahle units. I'd run 8:1 for 1bar and might experiment with 8.5:1 with lower boost pressures assuming aftermarket engine management. I'd install a 1mm larger exhaust valve along with 993 8mm valve stem size valves and clean up the ports slightly. I'd install a larger set of injectors, and run the basic engine stock with possibly a good set of Carrillo rods.

The bellhousing pattern is the same between 930 and 964/993 so the transmissions are interchangeable.

I don't think there is any strength differences between stock turbo and N/A halfshafts, only length is different.

Sameer

I got this off the 996tt forum posted by Kevin. Hope it helps.
Hear is a picture of a handful of connecting rods... From right to left we have:

1) Factory 930, 964, & 965 conn rod, very durable and provides long life when one balances and installs ARP rod bolts...

2) One of my favorites.. A Carrillo 930 conn rod, very strong, another benifit is that it has holes at the 4 & 8 o'clock position to provide oiling from the oil squirters that are in the case...

3) My new Titanium Pankl conn rod for my engine project... Extremely lightweight, strong and track proven for Porsche

4) 993TT & 996TT conn rod... This rod is the weakling of the bunch, it has some limitations. If you look at the neck of the rod, it is very narrow. Also, the rod bearing are much narrower. The GT3R uses 930 bearings!

5) and for fun, you boys can guess the application...

Buckeye19

Guys, thanks for all of the excellent replies.
This goal of this project is to eventually end up around the 500rwhp range after all of the work was done. I know that there are plenty of cars out there making more, but I don’t see too many around, so I want to make sure I have things researched in terms of reliability fairly well ahead of time.

Geoffrey, since the stock 964 NA pistons are made by Mahle, do you know if they are cast or forged? I wouldn’t imagine they felt the need to use forged pistons in a factory NA application, but being that they are made by Mahle who knows.

Are the oil pumps interchangable (with minimal modifications) within the 964 NA case so that I could upgrade if needed?

Also, does running aftermarket head studs significantly help with the head lifting issue? At what boost or power levels do you typically see this become an issue if the upgraded sealing ring is used?

So here are the reasons I think this may be a good way for me to go. Any other comments/ideas are appreciated.

1. If I purchased a factory turbo car instead it would most likely end up getting built internals soon enough anyway.

2. The Carrera already has 3.6L displacement as opposed to 3.3L displacement (I wouldn’t chop up a factory 3.6T for this project)

3. The car will already have a Carrera intake manifold instead of the pancake turbo intake manifold

4. Won’t have to find another set of heads to use for the Carrera manifold like when converting on a factory turbo motor.

5. The stock turbo/headers would be replaced/upgraded anyway.

6. The car will run an aftermarket EFI system, so the CIS fuel head etc won’t be needed anyway.

7. Knock sensor hardware is already in place, since this will be a vital tool in the EFI tuning.

8. Inexpensive and clean Carrera’s to use for this project are relatively easy to find.

Thanks again for all the great info.

Geoffrey

The Mahle pistons in a 964 n/a engine are in fact forged. In a 993 however, they are cast.

The oil pumps are interchangeable

38D

But if you buy a NA 964 you won't have flares, larger brakes, stronger tranny, and the LSD (to name just a few). The flares alone are huge, as there is no way you are going to run 500hp through 265s (unless you are crazy). IMHO it will be less expensive to start with a turbo.

Buckeye19

Actually, the flares are already high up on the to-do list as well. I love the look of the wide fenders, and would like the car to actually hook up decently, so I wanted to be able to run wider rears then what I could run on a factory turbo widebody anyway. I currently have a 300ZX twin turbo as my weekend toy that dynoed 540rwhp, and even with 285 wide Kuhmo Ecsta V700's (R-compound tire), I have serious traction issues until 3rd gear. 3rd and 4th gear pull like mad though.



After owning a couple tire spinning TTZ’s, having a 964 with all that nice engine weight over the drive wheels sounds very appealing.

I figured I would live with the NA tranny until I either broke it or came across a good deal on something stronger with an LSD.

The brakes I was also going to live with until I came across a good deal on an upgrade of some sorts.

And I agree, if I was paying a shop to build this car it would indeed be cheaper to just buy a factory turbo and do some bolt-ons to make it more entertaining. But I plan on doing a majority of the work myself in stages so that the cost isn't so prohibitive.

Buckeye19

Thanks for the great info!

Geoffrey

The only real difference between the G50 N/A tranny (01, 02, 03, 10) and the turbo trans (50, 52) is the size of the ring and pinion. The gears are interchangable between the two.

A turbo body car with 295s doesnt' really have traction problems, even with 550-600hp. A narrow body car can have 275s and sometimes 285s depending on wheel offset and tire brand.

FWIW, a 964 turbo can fit only 285s because of the trailing arms. You need to switch to narrow body trailing arms to get the wider wheels that the older 930s run.

Perhaps I could interest you in my EFI 89 930 which is for sale...

Buckeye19

Do you have a link to pictures and info on the 930 you are selling?

Sameer

Buckeye,
If I can add, Geoffrey's ride is the real deal.

38D

Both DrJupeman and I run 295s on our 964Ts, but it is tight.

Sameer

I'm on 275 and going 285 next round on my 10inch wide rear wheels which is the max it can take.