911 sc 3.6 to 3.8 engine rebuild thread

[-Levi-]

Hey everyone,

I wanted to share my 3.6-to-3.8 engine build.
The chassis is a 911 SC from 1981, I have been building the car over the past 15 years from bone stock and overall pretty tired to what it is today. The car is stripped down to the basics and the weight is around 2,250 LBS depending on the level of fuel (not including me of course.) Around 7-8 years ago I purchased a 1995 993 3.6 engine, added the VarioRaM intake manifold, S-car-Go 1'7/8 headers and a 997 GT3 exhaust to complete the engine conversion. During that time I put around 50K miles on the car.

Earlier this year the car started smoking consistently on every drive. After a teardown we discovered the expected valve guide wear and low compression in two cylinders. This prompted a rebuild, initially my plans were to just rebuild the engine in stock configuration, but a small savings on 3.8 P'Cs started me down that rabbit hole and my lack of self control kept it going.
Here is the car

[-Levi-]

During this time I also wanted to rebuild and upgrade the factory transmission to better deal with the 3.8 power. i assumed I would break the 915 a year or two after I did the 3.6 conversion, but it never let go, I never had any issues, so it stays.

Engine Parts List.
The base engine is a 1995 993 engine with a varioram intake conversion from a later 993. Mahle 3.8 liter piston& cylinders @11.4:1 compression
993 RS Intake Valves
993 RS Exhaust Valves
Light Port and Polish
Pauter Lightweight Connecting Rods
AASCO Titanium Valve Springs
AASCO Titanium Retainers
AASCO Titanium Keepers
FVD Mechanical Rocker Arm Conversion
FVD Sport Cams for Mechanical Rocker Arms
Fabspeed Carrera Cup Intake
S-Car-GO 1 7/8 Headers
Gt3 muffler (top and bottom feed)
Arp hardware
Patrick Motorsports Light Flywheel
Patrick Motorsports 3.6 conversion Clutch
Rothsport Single Belt Pulley
Steve Wong Chip


It seems like horsepower figures are all over the place with other peoples builds, I assume crank will be somewhere between 300-325? Does anyone have any input?





Transmission Parts list
1981 915 with LSD. At some point prior to my ownership the transmission had some significant damage and repair work as seen by the massive welds. I decided to keep the 915 case with the repairs as it has held so far and I like that it's part of the cars history.

Wevo Bearing Retainer
Wevo External Shifter
Wevo Solid Shift Joint
Wevo Reinforced Side Plate
RSR Spray Bar Kit
Wevo Internal Gate Shift Kit
Wevo Transmission Mounts
Wevo transmission pump
Setrab transmission cooler
Modified 964 Axles

[msmall215]

Been following the action on IG, should be a riot when done. As far as expected power, I would actually expect a bit more than 300-325 crank.

I will preface this with it's not a 1:1, but just another data point is a 3.6 build I had in a previous car. 964 based 3.6, 11:5 CP pistons, DC21 cams (pretty mild), heads rebuilt to all stock specs (no port/polish, stock valve sizes), Jenvey ITBs/Motec, M&K 1 5/8 headers with heat and a 2 in/1 out powerhaus muffler...272hp/240tq at the wheels, so around 320hp crank with 15% drivetrain loss.

I think you'll do at least that and probably more, definitely in terms of torque with the Vram.

[Mixed76]

Please say more about the titanium valve springs? I've seen this described before but it always turns out to be just the retainers. Does aasco actually make valve springs out of titanium now?

Especially it seems galling between the spring, retainer, and keepers would be a concern?

Cool build, thorough and fit for purpose

Sent from my Pixel 7 using Tapatalk

[-Levi-]

Originally Posted by Mixed76

Please say more about the titanium valve springs? I've seen this described before but it always turns out to be just the retainers. Does aasco actually make valve springs out of titanium now?
Especially it seems galling between the spring, retainer, and keepers would be a concern?

Interesting, I’m going off what I heard from my builder so i may be mistaken. Looking online you may be correct.

Originally Posted by msmall215

Been following the action on IG, should be a riot when done. As far as expected power, I would actually expect a bit more than 300-325 crank.

I will preface this with it's not a 1:1, but just another data point is a 3.6 build I had in a previous car. 964 based 3.6, 11:5 CP pistons, DC21 cams (pretty mild), heads rebuilt to all stock specs (no port/polish, stock valve sizes), Jenvey ITBs/Motec, M&K 1 5/8 headers with heat and a 2 in/1 out powerhaus muffler...272hp/240tq at the wheels, so around 320hp crank with 15% drivetrain loss.

I think you'll do at least that and probably more, definitely in terms of torque with the Vram.

Thanks Mike, appreciate the input as well. Big fan of your blue 911, spent more time looking at that than I should admit, lol. I would love to run. Motec, maybe in the future when I refill the bank accounts.

[-Levi-]

[-Levi-]

Getting closer

[Bill Verburg]

I know that you are using a 3.2 engine mount and crossbar w/ Sheridan f/g.

But am curious as to the possibility of using the Sheridan paces w/ a 3.6 mount and cross bar, any feelings on the subject?

Last year when I rebuilt my 993 in my '76 the engine was in and out a number of times, The main obstacle to raising the rear up was the 3.6 tin, I can see from your pics that the Sheridan f/g is ~1" lower than the 3.6 tin and if it can be used w/ the 3.6 aluminum console that might be the way for me to go.

Been looking for a 3.2 console for a few years now, from what I can gather(just a guess) Jeff Gamroth has been buying up all the spare 3.2 consoles.

[Ryan_Cunningham]

I just saw your IG post - Can't wait to keep up with this. Debating picking up a local '95 engine to swap into my 81SC.

[-Levi-]

Originally Posted by Bill Verburg

I know that you are using a 3.2 engine mount and crossbar w/ Sheridan f/g.

But am curious as to the possibility of using the Sheridan paces w/ a 3.6 mount and cross bar, any feelings on the subject?

Last year when I rebuilt my 993 in my '76 the engine was in and out a number of times, The main obstacle to raising the rear up was the 3.6 tin, I can see from your pics that the Sheridan f/g is ~1" lower than the 3.6 tin and if it can be used w/ the 3.6 aluminum console that might be the way for me to go.

Been looking for a 3.2 console for a few years now, from what I can gather(just a guess) Jeff Gamroth has been buying up all the spare 3.2 consoles.

Hey Bill!!
I wish I had more input for you. The engine mount came with the engine when I bought it years ago, at the time it bolted up so I didn’t give it much thought. I’m not a big fam of how my setup looks and I’m considering replacing it with something else.
Can I sent you an in depth video next time I’m around the engine so you can get a better view of it? Maybe some extra pictures?

[-Levi-]

Originally Posted by Ryan_Cunningham

I just saw your IG post - Can't wait to keep up with this. Debating picking up a local '95 engine to swap into my 81SC.

Absolutely do it!!!
Let me know if you need any help along the way

[-Levi-]

Rebuilt and refreshed the Varioram intake manifold. Not the lightest setup, but I cant pass up the extra torque.
Refreshed hardware, all gaskets replaced and intake cleaned in and out.

[stanglife]

Curious what options there might be for running an aftermarket ECU with varioram..

[Bill Verburg]

Originally Posted by -Levi-

Hey Bill!!
I wish I had more input for you. The engine mount came with the engine when I bought it years ago, at the time it bolted up so I didn’t give it much thought. I’m not a big fam of how my setup looks and I’m considering replacing it with something else.
Can I sent you an in depth video next time I’m around the engine so you can get a better view of it? Maybe some extra pictures?

I'd be very interested in anything that you come up w/

here's mine, 993RS console/mount, 993 cross bar 993RS crank pully, modified 993 tin


very similar the setup I used when I had a 3.8RS vram in there



This setup provides a lot of room around the crank pulley for even the 3 sheave 993 pully and of course room to change belts., The 3.2 console you use has room for a single sheave pully, the older 3.0 consoles lack that room

The issue is that these 1" spacers are used to lower the rear of the engine for fitment, which in turn leads to exhaust fitment issues


You can see here how high the 993 tin is compared to yours, I'm fairly certain that the cross bar height is the same or at worst very close to the odder 911 cross bar






I'm thinking of buying the Sheridan f/g just to see how it fits w/ the 993 mount and cross bar

[Bill Verburg]

Originally Posted by Bill Verburg

I know that you are using a 3.2 engine mount and crossbar w/ Sheridan f/g.

But am curious as to the possibility of using the Sheridan paces w/ a 3.6 mount and cross bar, any feelings on the subject?

Last year when I rebuilt my 993 in my '76 the engine was in and out a number of times, The main obstacle to raising the rear up was the 3.6 tin, I can see from your pics that the Sheridan f/g is ~1" lower than the 3.6 tin and if it can be used w/ the 3.6 aluminum console that might be the way for me to go.

Been looking for a 3.2 console for a few years now, from what I can gather(just a guess) Jeff Gamroth has been buying up all the spare 3.2 consoles.

Spoke w/ Sheridan yesterday, The definitive answer is , No, his f/g won't work w/ the 993 console and crossbar.

[-Levi-]

Just a bit of progress this week, dropped the car off for additional body harness cleanup and got the intake manifold mounted.
Also, I got to drool over a real RSR and a SCRS at the shop.

[-Levi-]

And the engine

[stanglife]

Lots of varioram excitement.

Anyone used an aftermarket ECU for these? Is the variable runner length specific to RPM or does it also take into consideration throttle position or engine load? Just wondering how people are tuning for this. One of my wants for my build is DBW but I'd trade it for varioram intake, if I knew I'd be able to use an aftermarket ECU.

[Bill Verburg]

A) Vibrating tube induction

If the gap (5) between sliding section (4) and central
intake distributor (6) is closed, the intake system is a
single-chamber vibrating tube induction system. Intake
air flows from the central intake distributor via vibrating
tubes designed for maximum torque to the cylinders.

B) Resonance induction

If the sliding sections (4) open, switching the system
from vibrating tube to resonance induction, the air flow
branches downstream from the air mass sensor (1).
One branch is connected to the central intake distributor
(6) of the single-chambersystem and one to the resonance
system (7) below the intake distributor.

From the central intake distributor, part of the intake air
flows through the intake pipe extensions, which act as
resonance tubes, directly to the intake funnels of the
short vibrating tubes and to the cylinders. The main intake
air stream flows via the second throttle flap and
the first large resonance tube of the resonance system
(7) to the resonance chambers. The resonance induction
system optimizes air flow to the short vibrating tubes.

C) Resonance induction with open tuning flap

The tuning flap (3) is installed in the second large resonance
tube. Initially, the tuning flap is closed. At a defined
enginespeed (5920 rpm), the tuning flap is opened,
increasing the flow area between the resonance chambers.
Air now flows to the resonance chambers via all
the connecting pipes.

Switch over conditions for intake pipe extensions
and tuning flap

1. When the ignition is switched on, the DME control
unit activates the solenoid valves. If the engine is
started, the intake pipe extensions and the tuning flap
are operated. When the engine has run up to idle
speed, the signal to the solenoid valves is deactivated
and the intake pipe extensions and tuning flap
are set to their basic positions.
2. If the engine speed reaches 5160 rpm and the
throttle valve is at least 50° open, the DME control
unit transmits an electrical signal to the solenoid
valves of the intake pipe extensions and the extensions
are operated, switching the intake system over
from vibrating tube to resonance induction.
3. If the engine speed is higher than 5920 rpm and the
throttle valve is more than 50° open, the DME control
unit opens the tuning flap, increasing the resonance
tube cross section.

yes, Motec and the like can be used to operate this

main vram benefit is midrange torque, for max hp use a GT3 intake

[Bill Verburg]

Any progress?