Player0

So I've been reading through hundreds of build pages and taking notes but I have a few questions on which parts to order that it might just be easier to ask.

So again, I am getting the 968 block, crank, and 2.7L NA head, and my intention is to throw this in a 944 Turbo body.

Goal for the engine is primarily reliability. I'd love this to be around 400ish. Anything higher is probably super hard to drive. I'd just like to have good torque on the entire RPM range and do so without pushing over 16-18PSI.

1.) Oil pan - I have seen a bit on this, enough to know anything is going to need a modification. I heard that some early 968 pans have an oil drain line? Is there a part number around for that? It sounds rare, so what's the next best thing? 968 pan or some other pan?

2.) 2.7L head - Can I just assume this is the same as any 8v head except with 3.0L water passages and larger intake valves? I know I need the turbo exhaust valves, but what cam do I run with a turbo? Is the 2.7 cam any good, or do I need to find a turbo cam? Or just go to web cam or NA cam or some other strange option.

3.) I just had my 86 951 diff rebuilt with a Guards LSD. Would this be compatible with the power? Does the LSD work do anything to make this thing stronger?

I may not use this transmission as I might want to leave the perfectly fine running car as is. Or, I might swap this transmission over to the new tub with the 3.0L as I may not have the budget to rebuild a new one unless absolutely necessary

4.) How do I mate a non-968 transmission to the 968? Is it as easy as using 951 components from the crank back or will this end up being custom somehow? Obviously I'll go with some beefier clutch but this area is generally fuzzy for me.

5.) Timing belt - Admittedly, I've done the least research here. Do I just buy all 968 timing components and waterpump, and then the 2.7L cam tower just works? Or am I going to need to mix and match somehow?

Kris H

ad 2) why not go the 16v route? The 16v heads flow significantly more for the same lift (between 30-80% more). As for the camshaft - the guide profile - timing, duration, overlap are very different between turbo and NA engines, I guess you can use the na camshaft, but it will not be an optimal combustion.

Thom

1.) Use the later style oil pan with the lower oil pick up tube. Most if not all S2 sumps feature a plug in the pan where the turbo oil return line is normally used with a turbo. I could be wrong but I think all 968 pans have this plug as well.

2.) The 2.7 head fits straight onto any 104mm block - 2.7, S2 or 968. Other difference with the other 2.5 8V head is the shape of the inlet ports which are oval instead of round, and larger. The stock intake needs to have its runner ports opened to fit with the oval ports of the 2.7 head. The stock and the 9R (same as 2.7) stock cams should get you to 400hp with ease.

3.) A standard 951 AOR trans in good condition will work fine with a 400hp engine. I have no experience with the Guards LSD but it is said to be one of the best LSD available for this gearbox, so I would guess your current one will work just fine.

4.) Not sure I understand your question, but if you are concerned with possible compatibility issues of using the 968 block with a 951 trans, it will fit as both blocks have the same mounting points with the clutch bellhousing. Use the complete 951 FW + clutch set up with the 951 bellhousing. Makes things easier if reusing the stock Motronic (or Vitesse or M-tune). Pauertuning may be able to supply with a complete standalone that will work with all factory sensors, if needed.

5.) There are two main set ups : one for 8V engines, another one for 16V engines. Since you are building an 8V engine, use the 8V set up, preferably with the spring tensioner instead of the eccentric tensioner originally found on the '86 cars.

Thom

On other platforms it may be true, but the stock 951/early NA (5R) and late NA (9R) camshafts are actually very similar in spec. The 9R cam has, on the exhaust side, 1mm more lift and a very little more duration. It makes a difference when used on engine with most stock restrictions removed (turbine, intake, etc), less so when using a restrictive KKK-style turbine and the stock intake that hinders engine breathing above 5500rpm. I would not bother with an aftermarket camshaft when using the stock intake.

Player0

Why not 16V head? Many posts here seem to advise against it as it increases cost. Also, it seems that this would require a lot of custom fabrication. I'm a beginner so I'm looking to keep that to a minimum.

On #2, the head has oval ports. I was assuming I'd need to use a 951 intake manifold. So I just grab a die grinder and oval it up? That easy? Or is more precision needed here?

I guess I use 2.7L intake gaskets? Or do I modify the 951 gaskets?

On #4, well in another thread it was recommended that I use a S2 harmonic balancer instead of the dual weight flywheel from the 968. It sounds like I can just use a 951 flywheel, clutch, from that point back and it will Just Work. I'll be using M-Tune so easier is better.

On #5, so there is nothing really 968 specific about the timing? I can pick up all S2 timing components easily. The 968 has a different tensioner though right? I wasn't sure if 968s ever had an 8v option and I wasn't sure if using a non-968 tensioner would be problematic here. Also if using the harmonic balancer on 968 kit would cause any fitment issues.

These might be silly questions, but I don't know much at all about the 968 and how much it differs or is the same.

Thom

2.) Yes, grab a grinder and open up the ports. Some may say that this should be done using a flow bench to equalize the flow between runners, but stock runners already do not flow equally.
Use 2.7 gaskets. Stock 951 gaskets are too small to be modified.

4.) The S2 harmonic balancer is the alternator/AC pulley at the front of the crank. It features a thick piece of rubber that no other engine in the series uses but the factory 3L 8V turbo. This pulley is independent from the timing & balance shaft belts layouts, 8V or 16V.

5.) The 968 hydraulic tensioner set up was designed to work with the thicker 16V timing belt, and I am unaware of cases where it has been used with an 8V set up. Using the complete 8V set up (from a later 951, with the spring tensioner) may be more straightforward and seems to be the norm. You will just have to remove the stud on the lower balance shaft front cover that is used, on the 968, as the pivot axle for the tensioner arm.
You will need the 8V-specific crank pulley for the timing belt, as the 8V timing belt is narrower than the 16V's. A shim is used to compensate for the difference in thickness between the two types of belts, and to push on the oil pump pulley.

Player0

Very excellent information, thank you.

michaelmount123

Actually, my flow bench has shown that the 951 intake runners do flow equally. It's a popular misconception that they do not. Also, don't be too quick to "grab a grinder" to open the ports. Although not rocket science, it takes care and the right tools to do properly so the ports between the intake and the head line up. The 2.7 ports are considerably larger than the 2.5.

Also, the 4V and 2V crank pulleys are the same width - there's no shim to compensate. The "shim" is used on both pulleys and its purpose is to seal against the o-ring inset into the oil pump drive.

Thom

I think it's clear to anyone that "grabbing a grinder" does not necessarily mean doing a bad job, which I think the OP is aware of.

The flanged 8V crank pulley got me confused about thickness, and yes the shim is always there. The 8V pulley is still needed, unless you suggest modifying the 16V pulley?

Interesting to hear you were able to get equal figures on your flowbench, even if it is not my experience.

Player0

Michael, what tools would you recommend? When I've port matched and polished intakes before, I've really just used a marker, the grinder with various bits and extensions, and patience.

I don't know how much more I'll have to cut this time but I'm assuming that I need to remove a lot more material and thin out the walls significantly. So I might use calipers or other measurements to stay honest.

I don't have access to any real machining tools other than a drill press, which some might argue isn't a machining tool at all

Player0

What flywheel should I use? Some 3.0L flywheel I imagine? Or do I move to a turbo flywheel for some reason? Any lightened flywheels out there worth considering?

Player0

Joshua from Rogue mentioned the Rogue DME I have will work fine for this. He mentioned using the 951 flywheel.

I just noticed while browsing the Katalog that the 968 doesn't have the usual crank/speed hall sensor arrangement. It's got a different bracket. If I'm using a 951 ECU, harness, and fly wheel, do I use the 951 crank/speed sensor bracket?

Jay Wellwood

You need to use the 951 flywheel and bell housing if you plan on using the 951 engine management system. The reference sensor that is needed for the electronics to work is mounted in the bell housing to read the speed signal from the flywheel IIRC.

Player0

I guess I should get a new oil pump for this thing rather than used, at 10x the cost. Just the 924/944/968 ALL 944-107-014-11 pump then that the katalog mentions? Or does the turbo variant fit and do I need that?

Chris White

No need for a new oil pump, they last forever. Double check for any damage and reuse. The only issue is very early na pumps 82-83) have a smaller seal.
Btw - I think the grinding mentioned by the poster was just port matching the 2.7 head to a 951 manifold. Leaving a big step is not a good solution!