944T Engine Rebuild

[barks944]

I'm about to embark on the rebuild of my 944T's engine. The engine is from a 220BHP car and will have a rebuilt K26/6 turbocharger (probably), lightly modified cylinder head, adjustable cam gear, maybe 3" downpipe with 3" front section, 2.5" rear section, stage 1 intercooler, late 944 NA cam and LR wastegate. Injection system will hopefully be my new modified motronic based system although probably standard with promax lvl2 chip to begin with. You can't beat the experience of those that have done it before so I'm going to post what I think I need and hopefully people can spot anything I've missed.

Widefire headgasket set
Short block gasket set
front engine seal kit
intake and exhaust gaskets
belts
Clutch Kit
Clutch release fork
9 Flywheel Bolts
9 Pressure Plate Bolts
T/O Bearing Guide Sleeve
Rear Main Crankshaft Seal
Clutch Fork Bearings
Pilot Bearing
Alignment tool
Clutch Fork Shaft
Engine Oil Thermostat and Seals
Air Oil separator o-rings
Turbo thermostat?
Thermostat
Connecting rod bearing set
Main bearing set
balance shaft bushings and bearings
Piston pin clips
Piston rings
engine block freeze plugs
oil pressure relief valve seals
connecting rod nuts
Loctite 574
Liquid Moly Assembly Lube

Any input appreciated! Including things to watch out for, top tips, cheapest places to buy etc etc!

Any tips on rebuilding a TT? Think the bearings are gone in mine....

Tom

 

[GPF]

I would have the flywheel lightened and the crank knife edged etc. and fit the LR steam vent kit.

I would also look into fitting the oil sprayers that point up the bores (like the 968 had I think?) and isn't there a mod to the baffles in the sump?

I'd also look at 3 peice crossover pipes and cross members - depending on funds.

Oh, I'd also ditch that k26/6 of course. []

How different is the late NA cam? A Cam could well be my next mod if it's likely to return a decent improvement.

 

[barks944]

The 9R camshaft has 1mm more lift and 3° more duration on the exhaust side than the 5R, turbo camshaft.

 

[barks944]

Crank/flywheel/clutch are going to be balance when they are out. How much weight should I take off? Its going to be a daily driver. Are there significant benefits to knife edging the crank?

 

[TTM]

ORIGINAL: barks944
The 9R camshaft has 1mm more lift and 3° more duration on the exhaust side than the 5R, turbo camshaft.

[] - Didn't you just copy/paste this from "somewhere"?

At the risk of repeating myself I wholeheartedly agree with ditching the K26/6. You just do not want to do anything with such a rubbish piece of turbo. Maybe try Pauertuning for a ball bearing hybrid if you cannot afford SimonP's.

 

[barks944]

No! That's original material right there...... Might go for GPF's old SFR turbo. So many options....

 

[sawood12]

I agree with the cylinder head steam valve kit from LR - not sure if it actually works, but it can't harm and is quite cheap. Also i've seen brackets that support the oil pick-up tube - it has been common (ish) for cars regularly tracked that the oil pickup tube can fracture resulting in an instantaneous knackered engine - again quite cheap if you've got your engine already stripped and can't harm things but will give you piece of mind.

On the turbo - I admire your desire to keep it standard, but when it comes to turbo's i'm in the 'modernise it' camp. However Vitesse was developing a modified K26/8 K26/8 to incorporate some new kit (not sure if it included BB's) which brings these turbo's bang upto date retaining the convenience of easy installation but giving you more flow, better spool up.

I think the lightened and knife edge crank is a bit OTT, but lightened flywheel was something on my wish-list.

Good luck and keep us posted!!

 

[barks944]

Great read on exhaust sizes from a guy from Garret:

http://www.tercelreference.com/tercel_info/turbo_exhaust_theory/turbo_exhaust_theory.html

My current stance on exhaust is 3" all the way back but with a tapered downpipe. Downpipe apparently should start at the diameter of the turbine outlet and increase to 3". Maybe this is a hard thing to build?

 

[DivineE]

I would save yourself a lot of hassle and bypass the LR wastegate that many like myself have upgraded to a Tial. The bigger Tial (46mm) is the same fitment and a far superior unit. If you've got an LR wastegate then its not the end of the world but I've held the two side by side a few times now and I know which I'd want. Rick found his LR wategate to be a pretty big leak when he was trying to track down boost leaks on WUF - that's why he changed to the Tial.

P.s. I still have my spare LR75 turbo for sale. You can do a lot better but its half the price of the next best thing and its used on both of the two 2.5ltr cars in the UK which make over 400hp.. so it can't be that bad.

 

[u63af]

I had about 3 kg removed from my flywheel, difference is great. I use mine as a road car and on tracks (in the future).

Is it just a standard camshaft out of a 2.5 944 that you are putting in? I will be rebuilding mine over the next couple of years so will start sourcing parts.

 

[GPF]

Oh, forgot - I'd also be looking at crank & rods to go to 2.8 "while you're in there"......[]

You will also need the 2 oil seals for the top and bottom of the turbo, and new crush rings for turbo to downpipe and turbo to crossover.

You can also get a different turbo water temp sender to increase the run time.

Also new o-ring and spacer for dipstick tube.

I also replaced the gasket for the water elbow that comes off the nsr of the head as it's a pig to get at later.

I don't think tapering the downpipe would be worthwhile though, I'd just stick to the full 3".

With a bigger turbo, you will also need to address the intake plumbing as the inlet will be bigger so the original j-boot won't fit. I have that sorted for the SFR turbo of course if you do want it - although I'd probable change it to lose the standard air box.

 

[TTM]

Ideally the plumbing ahead of the turbo inlet has to be at least as large as the inlet itself, meaning anything bigger than a K26 cold side won't work well with the original AFM/airbox combination and its "strangled" rectangular section.
Are you using the barn door AFM or plugging a MAP sensor to the Motronic?

 

[barks944]

Dunno exactly yet, I've got a LR MAF kit which has a 3" pipe to go from the turbo to the MAF. I will prob use the lindsay MAF kit initially.

 

[barks944]

ORIGINAL: GPF

Oh, forgot - I'd also be looking at crank & rods to go to 2.8 "while you're in there"......[]

I'm tempted but I dunno if I can justify the extra £££...

 

[Diver944]

ORIGINAL: GPF

Oh, forgot - I'd also be looking at crank & rods to go to 2.8 "while you're in there"......[]

I'd agree with Graham 100% and perhaps ditch some of the other 'bolt ons' so you can afford it.

Let's not forget that when Hartech dropped a 3L engine into their car they left EVERYTHING else totally standard and ran the factory 0.8 bar of boost to achieve just over 300 bhp but more importantly a whacking 350 lbft of torque with virtually instant spoolup.

You will no doubt be raising the boost and coupled with your standalone solution I think you'd surpass those figures easily and leave yourself an easier upgrade path of further bolt ons, as and when you can afford it. If you rebuild as a 2.5 now it will be a big ballache to go back in their for more capacity at a later date.

 

[barks944]

Anyone got a decent S2 crank?!

Can the standard clutch take that much torque?

 

[u63af]

I thoguht you needed an uprated clutch. Think K.e.p. (Kennedy Engineering) are good from US.

 

[u63af]

When I was speaking to the guy who is going to be doing the work on my engine he said putting a longer stroke crank in it will bring in the power lower down but it will suffer top end and will not rev as well. What is the best compromise for a track car?

 

[barks944]

Heres my understanding....

As the final volume of the 2.8 stroker is essentially the same as the 2.5 the maximum charge mass (before you get knock) for both engines is essentially the same. The 2.5 engine would of course require more boost to get the same charge mass. Due to its shorter stroke the 2.5 engine will produce power higher in the rev range than the 2.8 stroker. Its all about moments, the 2.8 has a bigger lever but as a result rotates slower.

The benefit of producing power higher in the rev range is that you are in a lower gear. So if the 2.8 is doing 80mph at 4000rpm in 3rd the 2.5 might might be doing 6000rpm in 2nd. Even if both engines are producing the same power the 2.5 has the benefit of being in a lower gear thus the wheel torque is much higher and thus it accellerates through 80mph faster than the 2.8.

The benefits of the stroker are that the engine has a much broader torque curve which makes it a more effortless car to drive, even if it isn't ultimately as fast. So in short for a race engine the 2.5 makes more sense!

 

[Lowtimer]

Not quite right, Barks, otherwise Barry's 300 hp 3.0 would be outperformed on the track by everyone under the sun's lightly modded 300 hp 2.5 , when in fact the reverse is true.

To correct your example of a 2.8 doing 80mph at 4000rpm in 3rd and a 2.5 doing 6000rpm in 2nd.
You say "Even if both engines are producing the same power the 2.5 has the benefit of being in a lower gear thus the wheel torque is much higher and thus it accelerates through 80mph faster than the 2.8."
Not so.
It would be true to say "Even if both engines are producing the same torque the 2.5 has the benefit of being in a lower gear thus the wheel torque is much higher and thus it accelerates through 80mph faster than the 2.8." But if both engines are producing the same power at that same speed in different gears, then the 2.8 must, by definition, be producing a lot more flywheel torque than the 2.5, because it is producing the same power at lower revs. That extra flywheel torque cancels out the effect of the higher gear to give the same rear wheel torque.

The real reason that a 300 HP stroker quickly pulls out a big lead over a 300 hp 2.5, all other components being equal, is that the bigger engine spins up the turbo a lot more quickly, reducing lag, and typically has a much fatter power curve with much more area under it through the working rev range. Both engines may have 300 hp at their different individual peak bhp rpm, but on the track the bigger capacity engine will be able to produce more bhp more of the time at revs below the BHP peak.