Building a 400bhp+ 2.5 ltr 944 Turbo

[333pg333]

Pete I never heard of Porsche running the Inline 4 to anywhere near 500hp but of course I'm sure they might have tried it in testing. Remember that the Porsche 934 had less than 450bhp. I've never seen one of the famed LeMans Rods but I'd be betting that it wouldn't resemble a stock rod 100%. I've got nothing against the stock rods by the way. I've ran them on motors up to approx 30psi (by accident) and run them regularly up to 23psi and not had a problem. If I was building a new motor though, I'd be looking at other options just the same. Of course it's possible to throw any rod with the wrong tune or assembly. If that happens though it won't be the worst of the damage! With your Vitesse software he's generally pretty careful/conservative at the limit. Otherwise LINK / Vipec (check TTM's setup) or Motec would be my recommendation.

 

[PSH]

ORIGINAL: 333pg333 Pete I never heard of Porsche running the Inline 4 to anywhere near 500hp but of course I'm sure they might have tried it in testing. Remember that the Porsche 934 had less than 450bhp. I've never seen one of the famed LeMans Rods but I'd be betting that it wouldn't resemble a stock rod 100%. I've got nothing against the stock rods by the way. I've ran them on motors up to approx 30psi (by accident) and run them regularly up to 23psi and not had a problem. If I was building a new motor though, I'd be looking at other options just the same. Of course it's possible to throw any rod with the wrong tune or assembly. If that happens though it won't be the worst of the damage! With your Vitesse software he's generally pretty careful/conservative at the limit. Otherwise LINK / Vipec (check TTM's setup) or Motec would be my recommendation.

Hi Patrick from what I've read Porsche certainly wound the Inline 4 up to 1.5 bar achieving 500bhp, then reduced it to 1.1bar 420 bhp for racing. of course you could look at the 944 GTR with over 600bhp, some say +700bhp but that has little resemblance to a stock 944 engine although still an Inline 4 non the less and certainly has some of the standard cars castings, block, cam tower etc, not sure on internals but very much doubt they are Porsche as it was a special built for the Americans. Anyway that car is a world away from what I'm building, I guess over time things get forgotten including how much Porsche associated the then new 944 turbo with it's Le Man car the 924 GTP also known as the 944LM. However the info is out there if you look, one such quote is: "The similarities between the GTP and the 944 Turbo are therefore quite apparent. As if to draw a more concrete connection, Porsche made notable associations. Interestingly, the cam cover of the GTP’s engine featured beveled text reading “944 Le Mans”, a hint at the car’s prototype status. In fact, some sources even refer to the car as the 944 GTP. Even Porsche commented in an advertisement for the 944 Turbo in 1986 that “efore we start production on a car, it’s already finished”, obviously referring to the similarities between the retired GTP and the production 944 Turbo." There are others but I'm getting a little off topic.. Regarding EMS/ not decided on this yet and as stated it's part of stage 2 so plenty of time to make a decision . Pete

 

[PSH]

Not had long for the engine today ( working on pond) but got one of the seized studs out, for those who are not sure about doing this it isn't too difficult, just take your time. First centre punch the end of the stud as close to centre as possible, drill out the stud starting with a small drill bit up to the correct size ( I started with 2mm up to 5mm) as if you were drilling a tapping hole. Use slow speed High Torque setting with plenty of cutting fluid. If by chance your off centre all is not lost just be extra careful and only drill out close to thread, you can either then use an easy out ( i don't like these, too easy to break) or manually grind away ( small dremel will do)until the hole is more central and then continue with correct drill size. Others may use a different approach, this one works for me, finally I re-tap the hole with a HSS tap, don't use the cheaper carbon type, although they are very sharp they are also very brittle and more likely to snap which is a possibility when working by hand at an angle. hole at 3mm size

final 5mm size drill, note the tape used as a guide to stop before drilling too deep. It's interesting to note that here in my eyes is a design flaw and why the studs were so corroded in the first place. The corroded studs ,all to a varying degree progress into the water way, some clearly go right through whereas others just barely break into the inner surface. I haven't yet checked with the Porsche manual for this stage but either the studs are left alone to their own devices and hence have corroded due to entering the water way, they were originally sealed which has failed due to age or if they should indeed be sealed the water pump when replaced previously wasn't done properly and studs were inserted dry. Knowing which independent did this work and the problems they have caused me before this wouldn't surprise me at all but i digress. What ever the facts are surely the use of stainless studs here would have avoided this extra work now?

finally after re-tapping the hole 6mm I replaced one of the old studs to check the depth was sufficient, I also inserted a short 6mm bolt and torqued it up to it's 6lb setting to ensure the thread is still up to the job. don't get me wrong this is overkill but it's the way I work so forgive me for taking extra care.

Needless to say I won't be covering all such problems but thought it worth recording this to help others, if everything had gone badly wrong I do have heli-coil kits but prefer to try and avoid using them if at all possible, the important thing is that the hole remains true to it's original position. Pete

 

[George Elliott]

Pete you do a better job of stud extraction than our local dentist...well done. just on that, I have found MIG welding an oversize hex nut to the stub can sometimes persuade them to release, the objective is to get as much heat as possible down the stud. Maybe this releases the sealant from the factory, or maybe they loctite them, I don't know. Just on the Rods point, my engine is a perfect bore block with early OE rods. Its not a serious power unit, but slightly improved all the same. Simon at SPS was very confident these rods were good. I accepted his view for two reasons, one you do have to draw the line somewhere, and two - there's not much point in using flashy 1000bhp rods in an engine with half that power. There will be those who take the while your at it viewpoint, and for sure none of us want to risk putting a leg out of bed, but there is no unbreakable rod either. The crank weighs near 30kg I understand, so a few grams of extra rod weight is unlikely to hinder the unit, but the balance is key as always. It's not going to be a Vtec Honda after all. Have you considered a steam vent kit off the back of the head? Its not big cost, and analysis of engine failures is often close to this area, just a thought as you have the head off. Thanks for all the info. Good luck with the project George 944t

 

[MarkK]

Loving the thread!Great read and pics!

 

[PSH]

ORIGINAL: George Elliott Pete you do a better job of stud extraction than our local dentist...well done. just on that, I have found MIG welding an oversize hex nut to the stub can sometimes persuade them to release, the objective is to get as much heat as possible down the stud. Maybe this releases the sealant from the factory, or maybe they loctite them, I don't know. Just on the Rods point, my engine is a perfect bore block with early OE rods. Its not a serious power unit, but slightly improved all the same. Simon at SPS was very confident these rods were good. I accepted his view for two reasons, one you do have to draw the line somewhere, and two - there's not much point in using flashy 1000bhp rods in an engine with half that power. There will be those who take the while your at it viewpoint, and for sure none of us want to risk putting a leg out of bed, but there is no unbreakable rod either. The crank weighs near 30kg I understand, so a few grams of extra rod weight is unlikely to hinder the unit, but the balance is key as always. It's not going to be a Vtec Honda after all. Have you considered a steam vent kit off the back of the head? Its not big cost, and analysis of engine failures is often close to this area, just a thought as you have the head off. Thanks for all the info. Good luck with the project George 944t

Hi George As the saying goes great minds think alike.. I did try welding nuts onto the studs as you suggest after failing to move them with Molgrips etc, I had got a little movement with the grips but alas they were just too tight. Unfortunately the welding weakened the steel which I was half expecting as the studs were in a very bad shape, you'll probably be able to see in one of the pictures just how much of the thread had been eaten away so I wasn't surprised they gave up. Saving weight on the crank and it's components will give a little more power and and a quicker revving engine but as you say 'were do you draw the line' Technically the crank is already a little lighter due to being reground but this won't make much if any difference, pistons will be lighter but the real saving will be from using a crank scraper which I've read will save around 7lb's in rotational mass on the crank. More importantly it will greatly reduce the build up of entrained air bubbles within the rotating mass which has been known to cause No.2 rod bearing to fail. Add to that the lightweight flywheel and things are certainly moving in the right direction. The steam vent kit is an interesting one and something I'm considering especially as I have had two gaskets and a valve fail all around No.4 exactly where the air pocket that the steam vent kit is supposed to reduce is know to occur. So there's a big possibility that I'll go this route although I'm still researching what other ideas may be out there. Thanks for the input George, the more the better.. Pete

 

[Ex Skyline]

Great piccy's Pete and, great input from everyone so far! I am learning a lot from this thread. Pete []

 

[PSH]

thanks for the kind words everyone... Ok so regarding

ORIGINAL: TTM Will be interesting to follow your progress, good luck with this project! What compression ratio with these pistons?

Hi TTM Well I had a few minutes today to look closer at the CR possibilities, I've used the standard head cc for the calculation as I don't know what my Lindsey stage2 head is and it will be some time before I get around to stripping the head and polishing ready to measure it's cc, plus the head needs machining first, due to the resulting damage sustained in No.2 chamber from the damaged iridium plug mentioned previously and thus will get deeeper, although only by a very small amount. Also another consideration is gasket bore size, unless someone knows better the closest that i can find to my new 101 bore is 100.5 or 103mm so I'm thinking that 103mm may be for me. Also the choice of Cometic gasket thicknesses for the 944 is massive, from 0.68-2.03mm so I have a little to play with here. For ease I've used a bore of 101mm for the calculation on the gasket, using a thickness of 0.70mm so what do we have? Displacement = 101 x 78.90 (10,1 x 10,1 x 3,1412 / 4 * 7,89) = 632.05cc ( considering deck as 0) per cylinder with a total displacement of 2,528.2cc... nice.. Head = 55cc (standard approx) Piston volume dish= 26.0cc 101x0.70mm gasket = 5.6cc (aprox) CChamber = 55 + 5.6 +26(piston dish) = 86.6cc Therefore: 632.05 +86.6 ) / 86.6 = CR 8.26:1(using a 0.70mm gasket) Now this is using the thinnest available Cometic gasket , so the CR will only get less with the other gaskets available to me, add to this the possible larger bore of 103mm and I'll have no problem maintaining 8:1 or less. So the question is gasket bore size, 100.5 vs 103mm, the way I look at it having a gasket with a smaller bore than the cylinder is a no go (unless someone knows better?) so I guess it will be the 103mm Anyway that's my head fried enough for tonight.... On a good note i got the two remaining water pump studs out tonight, just the 10mm mounting stud to go and that's going to be a real bitch All opinions very welcome as usual Pete

 

[George Elliott]

(10,1 x 10,1 x 3,1412 / 4 * 7,89) = 632.05cc

Pye = 3.14159 = Ans 632.13cc [8|] For this level of performance it may just matter...[] George 944t

 

[PSH]

ORIGINAL: George Elliott

(10,1 x 10,1 x 3,1412 / 4 * 7,89) = 632.05cc

Pye = 3.14159 = Ans 632.13cc [8|] For this level of performance it may just matter...[] George 944t

hahahahahah... you just made my day, nearly fell off my chair.....I think I meant to say 3.142, not sure where the extra 1 came from but if we want to be really accurate although pye is infinite you could use.............................. 3.14159265358979323846264338327950288419… 0348 2534 2117 0679 8214 8086 5132 8230 6647 0938 4460 9550 5822 3172 5359 4081 2848 1117 4502 8410 2701 9385 2110 5559 6446 2294 8954 9303 8196 4428 8109 7566 5933 4461 2847 5648 2337 8678 3165 2712 0190 9145 6485 6692 3460 3486 1045 4326 6482 1339 3607 2602 4914 1273 7245 8700 6606 3155 8817 4881 5209 2096 2829 2540 9171 5364 3678 9259 0360 0113 3053 0548 8204 6652 1384 1469 5194 1511 6094 3305 7270 3657 5959 1953 0921 8611 7381 9326 1179 3105 1185 4807 4462 3799 6274 9567 3518 8575 2724 8912 2793 8183 0119 4912 9833 6733 6244 0656 6430 8602 1394 9463 9522 4737 1907 0217 9860 9437 0277 0539 2171 7629 3176 7523 8467 4818 4676 6940 5132 0005 6812 7145 2635 6082 7785 7713 4275 7789 6091 7363 7178 7214 6844 0901 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Pete

 

[George Elliott]

hmmmm...... eemmmmmmm....... ........that looks more or less correct ....[] good luck

 

[Mike_Pollock]

Tried using those figures and had to sharpen my pencil 28 times.........[8|]

 

[PSH]

you need an auto pencil sharpener Mike.. Although there's not much to show for it, this weekend was a full on working on the engine affair. First was the seized 10mm bolt as shown in the picture, this truly was a bitch. I tried all of the normal methods, grips, hammer and chisel, welded nut,heat and finally the horrid easy out but none would budge it, the steel had become welded to the alloy for good.

So I decided to drill a 10mm tapping size hole (8.5mm) but since the previous methods had left the bolt in a mess I needed a way of keeping the drill as true as possible. The picture shows the Alternator bracket ( not engine mount as I originally thought) bolted to the block, I them found a suitable sized piece of brass tubing that both the drill could fit through and also fir into the bracket hole. This was cut to length and had two functions, protect the bracket and act as a depth stop for the drill bit.

This worked reasonably well with the newly tapped hole close enough to the original position so that the bracket fits with all bolts tightened up. It was a pig of a job and it took a lot of time but at least I got there in the end.

Next was to remove all of the main bearing studs, this turned out to be a lot easier than I feared having struggled previously with the head studs, so much so that 3 of them I gave up on and let the engineering shop remove them before boring, mind you they struggled themselves and it cost me £160 + vat in labour.. ouch. studs were removed first using still-son's to crack the seal and then finished using the two nut system.

After all of the studs had been removed ( I left the small stud seen ( oil pick-up) as it was in good condition and not a stress item) it was time to re-tap all of the threads, this is very important and took a number of hours to do properly ensuring all of the old loctite had been removed before tapping, it's also important to ensure no metal or as little as possible is removed during this operation.

With the bottom finished it was time to re-tap the 10 12x1.5mm head studs, I was worried about this for two reasons. First they are deeply recessed which means very difficult to fix if something goes wrong and also the state of the threads from the 3 that had previously proved difficult to remove was very bad indeed. There are a number of tapped holes in the 944 block that for some reason ( i guess space) enter waterways, other tapped holes or both, one such is the front head stud above the water pump, this thread was particularly bad. Re-tapping the head studs took half a day , all of which was a nerve wrecking experience. The picture shows what I had to make up just to be able to reach the threads, still they are all done now so one more job out of the way, the picture also shows the nice job that Serdi's UK did on decking the block.

Now a question, I need to decide what finish for the block, I originally planned on polishing it but this tends to look very dirty quickly even with lacquer, so i was thinking of an engine metallic silver heat resistant paint that would look the same but last and be very easy to keep clean. What do you guys think???? Pete

 

[944 turbo cabrio]

For sure the latter option - will make you just as happy but for way longer Very nice thread indeed although reading of all this thread tapping makes me really scared for my own build in the winter Thumbs up from Copenhagen! /Niels

 

[PSH]

ORIGINAL: 944 turbo cabrio For sure the latter option - will make you just as happy but for way longer Very nice thread indeed although reading of all this thread tapping makes me really scared for my own build in the winter Thumbs up from Copenhagen! /Niels

Hi Niels Thanks for the kind words, I think your right about the paint option, still not sure though as my instinct is a lovely polished alloy but that's only good for a show car, not one planned for everyday use. My son brought home some 500c silver paint tonight for me to try out so I think I'll give that a go and report back. BTW don't let me put you off your own build, I probably make it sound worse than it really is and if all else fails a good machine shop should solve it for you. I had planned on removing the alternator stud by machining it out on the mill but unfortunately the block will only fit upright on my mill bed and I hate adjusting the head to a horizontal position and then having to reset after, so by hand it was... Kind regards Pete

 

[PSH]

Evening all Only one picture for today although it took a lot of work before taking it. I went over the block with a wire brush fitted in the drill and after blowing all of the crap off wiped the block down thoroughly with IPA. Next was the laborious job of masking everything up followed by a dusting coat of Hycote VHT aluminium paint , left for 15 mins and then two more full coats. VHT is a very high temp self etching paint that has very good adhering properties and is resistant to petrol and oil, let's hope so. As always when dealing with paint, cleanliness is next to godliness and even more so for this application, it's rated for over 500c so will be interesting to see how long it lasts.

Just need to get some loctite 574 or equivalent and I can re-install the crankshaft, so hopefully the next instalment will be just that, of course that's if I haven't forgotten anything which is more than possible... Pete

 

[barks944]

Check the bearing cage alignment very carefuly. You may find the cage has grown/warped over the years. When building my engine we had to make an offset alignment peg to get it all back in line. Best place to check is at the front of the engine where the oil pump bolts on.

 

[PSH]

ORIGINAL: barks944 Check the bearing cage alignment very carefuly. You may find the cage has grown/warped over the years. When building my engine we had to make an offset alignment peg to get it all back in line. Best place to check is at the front of the engine where the oil pump bolts on.

IIRC The workshop manual does cover how to ensure the alignment is correct using a VW gauge which I suspect is similar to a plastic gauge. Thanks for the heads up though, there's a lot to remember when assembling a Porsche engine. I've been in the city all day at a film screening so not had time for any work on the car. Hopefully I can pick up some suitable flange sealant soon and get the crank in. Pete

 

[Ex Skyline]

I'm having Manthey rods on my 2.5ltr rebuild this coming winter. Dont know if they are in house manufactured or,wether they are indeed manufactured by Paulter and bought in. I am going to Manthey Motors in September whilst on my birthday trip to the "Ring" so i will talk to them and find out. I may also buy some other parts for Jon Mitchel to incorporate into the rebuild as long as i'm able to take another dividend this year (50/50).

 

[Ex Skyline]

Forgot to ask, who is doing your machine work Pete?