That could be a great idea but it could be a lot of money.
So here’s the deal. In my opinion it’s a waste of money to rebuild a nice motor. That being said, now that nice motors are at least 24 years old..and as much as 33 (2022) it’s something to think about.
A rebuild of a 964 motor at this point is going to set you back $10-12K since you may as well do studs. Also note that as of the summer of 2015 we are starting to see more and more case though bolt leaks. If you get that it’s a top end minimum, plus you are pulling through bolts so you may as well split the case.
Let’s look at some scenarios. Start with:
- Early 964
- top end.
- increase the bore to 3.8, and simply do a top end
- increase the bore and completely rebuild it
- convert it to a 993 VRAM RS 3.8 with solid rockers
- 993 VRAM
- Add cams, valves and solid lifters
- convert it to VRAM 3.8 with Cams and valves
- 993 VRAM and convert it to solid lifter VRAM RS 3.8
** NOTE THE PRICES BELOW ARE 2015 or so, scale accordingly *****
Lets say you got a 964 3.6 with leaky heads for $12000
1) Replace the P&Cs with late used ones for a $1500 then add rod bearings, bolts, and head studs along with basic top end, $4,000 parts, $4000 labor, $20,000 motor.
2) If you simply increase the bore to 3.8, the only difference in price is the P&C set and a little head work and tuning $4800, but you save $1500 on the used P&C, $18,800 total
3) for the complete rebuild add $300 in parts and $1700 in labor and you are at $20,800
4) To go with a 993 3.8 VRAM RS you need to port the heads, increase valve size, intake and exhaust, change out the cams, buy all the parts it takes to change over to 993 intake, harness and brain, plus the large runners for the intake and replacement stacks, and don’t forget better springs and caps etc. We recently did this. $29,000 including bottom end, fuel injectors and a few other odds and ends, after selling off the surplus 964 stuff.
5) Now buy a VRAM that has some worn exhaust guides. Get one with euro electronics and you’ll still pay $14,000 or so. Now increase the intake valve size to 51.5 mm RS, add some RS hydraulic cams, do the top end and you are looking at $8600 in parts ($6800 from (2), top end, rod bearings and studs plus $1800 in cams and valves) and $3,200 in labor to make it a round $26,000.
6) To convert to a true euro RS 3.8 you add the larger RS intake stacks and runners, if you can find them ($2000) port the heads ($600) and just to put icing on the cake add some nice springs and retainers ($800) and you are at $28,400, but you may as well do a bottom end so lets just call it $30K
7) Now let’s put in some REAL cams. That means 12 solid rockers and adjusters, and you are going to need them modified, so add $2K. $32,000
The difference between 4) and 6) is mainly in whether or not you want hydraulic lifters. If you want to get some more power I’d go with the solid lifters and a more aggressive cam. You could also convert the 993 to solid lifters (the factory did this on the race cars, about $1800) in which case the 993 motor will be a bit nicer. In case you are thinking about starting with a ’95 993, that’s fine, you just have to figure out the engine management and buy the VarioRAM Intake and throttle body, hoses, etc. so that may or may not be cheaper. Depends on what you have available.
All of the above assume you invest in a decent set of headers (1-7/8″) and a free flowing exhaust. If you look at the factor figures below, the 18 hp of the 3.8 RS is less than impressive considering all the work. On the other hand, if you think about it, it wouldn’t have cost the factory any more to do them all as 3.8 RS!
Look at the figures though:
|Stock Models||Torque at 4000 RPM (ft-lb)||Change||Max Torque at 5000 RPM (ft-lb)||Change||Max Power at 6200 RPM (HP)||Change|
|95 993 (type 06/07)||199||243||272|
|96-98 (type 21/22/23/24)||238||+20%||251||+3.2%||282||+3.7%|
|96-98 3.8 RS (type 20)||248||+24.6%||261||+7.4 %||300||+10.2 %|
|Tuned Models w free flow exhaust||Torque at 4000 RPM (ft-lb)||Change||Max Torque at 5000 RPM (ft-lb)||Change||Max Power (HP)||Change|
|95 993 (type 06/07)||230||254||286|
|96-98 (type 21/22/23/24)||276||+20.0%||286||+12%||297||+3.8%|
|95 993 3.8||240||+4.3%||265||+4.3%||300||+4.8%|
|96-98 3.8 VRAM (type 20) (5) *||288||+25.2%||296||+16.6%||328||+14.6%|
|96-98 3.8 RS VRAM (4 and 6)**||300||+30.4%||312||+22.8%||343||+20.0%|
|96-98 3.8 RS solid VRAM (7)**||320||+39.1%||332||+30.7%||365||+27.6%|
*Euro 3.8 RS Hydraulic Cam
**More aggressive solid lifter grind
Is it worth it? That’s up to you!
What isn’t on the chart is that if you take a 993 VRam motor, and just put on headers and a tune you are at close to 300 HP, a 964 with exhaust will get you to 290 or so, and if you take a 993 and add cams and valves you are at 325.
Bottom line is that the 3.8 conversion gets you about 4% based on displacement alone, that’s only 12-15 HP, but it also allows you more flexibility and opens up other doors.