Building a 400bhp+ 2.5 ltr 944 Turbo

[PSH]

Big update for tonight, so bear with me, so fitting of the Crankshaft. Before refitting the crank there are a few things that need checking, the oil clearance and end float. I tend to check things twice if possible when building things for safety(Although only had one way available to me for oil clearance ) in different ways so first thing I did was to measure the crank journal diameters followed by the inner bearing shell diameter to see if there was enough oil clearance. the normal way of doing this is by using a plastic-gauge that you crush within the bearing shell by fitting the crank and temporary torquing down to the correct force and then measure between the crush marks checking a tolerance chart for correct measurement. Unfortunately I don't have any suitable gauges so relied on measurements using a vernier making sure that the shell was sufficiently larger than the journal to allow a correct oil lubrication, happy to report that Serdi had done a good job when grounding the crank, in fact the differences between each journal was very close, closer than Porsche tolerances for a new crank and the oversize OEM bearings were correct. Next was the end-float, this is checked during assembly using a dial gauge but beforehand I also checked the width of the thrust bearing compared to the crank centre journal clearance, any problems here would mean a new crank but the difference here of 0.115 clearance suggested that the actual play would be well within that of a new crank so no discernible wear there at all. btw a new crank should have between 0.110-0.312mm end-float with 0.40 being the max limit for wear, so not much to play with, I'll double check anyway with my dial gauge in the morning once I dig it out. First picture tonight shows the bearing shells fitted to the upper engine casing, also in the picture is the MPZ engine assembly lube that I'm using and a bearing shell that will be fitted into the lower casing just to show the difference between the two, the upper bearing having the oil way while the lower is plain.

next picture shows the lower bearing frame with the plain halved bearing shells fitted, the thrust bearing in the centre is identical for both top and lower shells. The ( missing) front bearing shell is one piece so goes onto the crank first and has to be aligned with a small locating pin to stop it spinning.

crank in position awaiting the lower frame, note the Loctite 574 sealant being applied to the block, the normal procedure is to apply this with a small roller to the lower from but it's not that important as long as it seals. The journals will have more lube applied before assembly.

Finally the frame is now torqued down following Porsches sequence but not their torque settings. Raceware settings are in 3 steps, 12mm are 20-40-55ft/lb and the 10mm are 15/20/30ft/lb, the smaller bolts are Porsche's so done to their settings.

I've left the oil pickup tubes off for now as they'll get in the way when fitting the con-rods which I hope to do soon.. Pete

 

[George Elliott]

Hi George I had written a long reply but when trying to post i had been logged out somehow and lost what I had written..lol To cut a long post short yes I'm aware they are dowels, Porsche call them fitting bushes which is why I did the same The front dowel position is shallower than the rear and with only one size available from Porsche I decided that there never was one fitted. Backing this up is the fact that the Porsche parts diagram only lists one dowel and on looking at TTM's thread his engine also didn't have a front dowel fitted. However like you my head was telling me that studs alone can not align the crank as accurately as two dowels can, hence why I decided to machine down one dowel to fit into the shallower front position. Of course there's always the possibility that Porsche did originally fit both dowels to earlier cars but discovered a problem only rectified by removing the front dowel. I thought this to be an unlikely scenario but did dry fit the lower crank frame using two dowels and then carefully checked that the journals were running true, as all seemed well I decided to fit the second dowel. Like you say using studs only allows too much movement and yes you can move the front journal out of line by a few millimetres although of course this is only possible without the frame being torqued down. I didn't like this and since the block was originally machined for a dowel I took advantage of it to fit one. Hope this makes sense, as i said I had written a better description but can't rewrite it again now, I'll now copy this before posting.. Pete I agree that it can't slide lengthwise but it can pivot on the rear dowel and thus put the front journal alignment out a little, which also effects the other journals although to a lesser degree the closer you get to the rear dowel. Now with new bearings matched to a reground crank this shouldn't be an issue as the crank once torqued down should seat within the journal correctly or if it doesn't it will be as close as not to make much difference due to no play within the new bearings, although I'm sure a learned engineer would argue that any miss-alignment no matter how small will cause faster wear to the bearings. However where it could prove more problematic is when refitting a used crank using it's original bearings, although technically they may still be within their wear limits, the crank could be torqued down out of line. We are talking tiny amounts here but such things do matter, especially when asking a lot more out of the engine than standard. Pete

Makes total sense to me, only belt and braces I would suggest is ask Serdi, Promax, Barry Hart, JMG for their opinions on the double dowel to be sure to be sure. and don't ask an OPC......they will ask you if its a tiptronic, and if so - is it a 3 door or 5 door...[:-] interesting to see the progress George

 

[PSH]

[/quote] Makes total sense to me, only belt and braces I would suggest is ask Serdi, Promax, Barry Hart, JMG for their opinions on the double dowel to be sure to be sure. and don't ask an OPC......they will ask you if its a tiptronic, and if so - is it a 3 door or 5 door...[:-] interesting to see the progress George [/quote] Well bit late for that George as the crank is now in but I'm confident that the extra dowel can only be better with rather than without. I guess the proof is in the pudding as they say but the lower frame fitted perfectly with the crank in position and the front face is near perfect for the oil pump although I'll give it a once over to be sure. So all in all I'm happy with the result.. Pete

 

[PSH]

A one picture from yesterday that I couldn't upload due to technical issues with photobucket. Overall view of block with crank refitted

I'll probably need a full day for fitting the piston's due to how critical ring gaps are so will take my time doing this stage, shouldn't be too long though... Pete

 

[Mike_Pollock]

I'm loving this Pete[]

 

[MarkK]

Me too[]

 

[PSH]

Cheers guys I've had a busy day today although haven't actually built anything. Spent the day researching the best ring gaps for my planned application which involved a lot of head scratching, I knew the formula for working out the gaps and knew that I needed to allow extra for the heat developed from an engine producing 400-450bhp but how much more should I open up the Porsche recommended gaps to. Added to this is the fact that the car won't be driven at full power that often and I didn't want to open the rings to far and risk reaching the wear limit sooner. Having said that the IASA rings are full blown race rings which are around half the thickness of standard rings and thus will wear quicker, so I'll have to change them at some time, mind you the difference that they will make in less friction in the bores will be significant. Just turning such an engine over by hand will require around half the energy of an engine with standard rings. So, Porsche gap average is: 1st: 0.30mm 2nd: 0.30mm oil: 0.45mm using the formula for a modified street/drag strip engine an engine of my bore will work out at 1st: 0.48 2nd: 0.53 oil: 1.49 ( I didn't like this gap at all and question it's validity but that's what the formula adds up to) But I adjusted these setting to what makes sense in my head for the job in hand so have decided on the following: 1st: 0.45 2nd: 0.50 oil: 0.55 Once I had decided on these settings I sent my findings to IASA with details of the ouput planned for my engine and was very happy to get a green light back from them this evening. all systems go then... Pete

 

[PSH]

Setting ring gaps Ok so first thing was to get all 4 box sets and label them 1 to 4 , next was to fit each ring into it's corresponding numbered bore and note it's measurement. Each ring must be square within the bore , you can use a ring square tool or a used piston to do this job. For anyone taking notes if you are gaping rings on a used engine, ie it hasn't had a rebore you need to check the ring at the top and bottom of the bores in case of any tapering. If the bore is tapered but it's still within allowed tolerances then you set the gap to the smallest part of the bore. Ok so results: No.1 1st: 0.40 2nd: 0.57 oil: 0.62 No.2 0.39 0.58 0.77 No.3 0.39 0.57 0.62 No.4 0.40 0.57 0.77 Obviously I can't do my planned gaps of 0.45 0.50 and 0.55 but I can now see why IASA gave the green light so quickly as I'm very close to the ones that they have machined too. So I'll have to live with the 2nd and oil gaps since I can't add material back to them and they are very close anyway but I can take the 0.05 from the first ring which is the most important of the three and the one that would seize if too much heat is generated under full power. First picture using a table sander to take a tiny amount of easily and squarely from either end followed with using a fine cut No.2 file to finish.

All of the 1st rings were filed until the clearance was 0.45 as planned, note as my block is freshly machined I can measure close to the top rather than the preferred position of the ring's TDC location.

Picture of the IASA piston and rings, note the extra machined V groove between rings 1 and 2. This helps stop fluttering of the top ring and greatly reduces any possible blow-by. There is another machining process that can be done to the piston if intending over 7000 revs. You can machine half round holes in the lower edge of the top ring groove, the amount of holes differs depending on bore diameter, a bore of this size would require 5. I've decided these are not needed for this engine as I do not plan on exceeding 7000 rpm, however I did do this to my son's Cossie and the top ring seal was greatly increased thus increasing power.

Now for today's set back, I should have checked this before but unfortunately I forgot, I checked the tolerances for the wrist pin bushes only to discover that they are out side tolerance Results were No.1 24.04 No.2 24.04 No.3 24.05 No.4 24.04 Porsche's guidelines state 24 +0.018 - 0.028 icture shows bore gauge being used to measure the bush

Final picture shows the damage sustained to one of the bushes, if you look closely you'll see two things, one is the discolouration of the bush were the outer layer has been worn through and secondly you can just see that the bush itself is thinner on that side when compared to the opposite side, so good job I decided to do a rebuild as the little ends are very close to failing.

So a slight set back but no big deal, I've spoken to Serdi UK and I'll drop off the con rods early next week to have the bushes pushed out and new ones inserted. This is not a job to do at home, the rods need to go onto a machine that will insure they are square and give the correct centre's between big and little ends. Once the new bush is in it will need machining and finally reamed to the correct diameter, also the oil holes need doing. Oh and the cost will be £180+vat plus the cost of new bushes which are around £8 each. Pete

 

[422hp944]

Total admiration for what you are doing Pete, You must have great satisfaction in building this engine!....Definitely an education for us watching it coming along...

 

[VanhireBoys]

Too Right John ... What a fantastic job Pete.....! I cant wait ....! [] The pictures are a big help in my education ... Id love to strip a 944 mill now - Under supervision of course as always []

 

[PSH]

hmm well for some reason I lost tonights post so will just repost pictures this time with a little info, can't rewrite it all... first off to ex-skyline and vanhireboys, thanks for the comments guys but must say that there's nothing difficult about this, just follow Porsche protocol and all will be fine. this is the upper shaft with it's new bearing fitted

next shows the shaft fitted, note the new seal on the bearing housing, this is for when the turbo oil exhaust ( return) pipe is fitted. Hold this in with a little grease to unsure it doesn't fall out when fitting the cover.

final picture shows the repainted housing fitted, the front bearing housing is only temporary fitted to ensure that the housing sits correctly.

Pete

 

[PSH]

The 944 engine's secret weapon... both balance shafts back in their housings.. Pete

 

[Diver944]

Blimey Peter, I go away for a week and the engine changes colour and half the bottom end is back together already. Really hope you've got those ring gaps correct, it's quite a large difference to the standard Porsche spec []

 

[PSH]

ORIGINAL: Diver944 Really hope you've got those ring gaps correct, it's quite a large difference to the standard Porsche spec []

me too..., nah they will be ok, only .05mm larger than IASA had pre-set them too ( still .03mm less than the formula recommends) and ok'd by IASA when given my planned bhp out put, need to allow for that extra heat or she'll just loose power at the top end with piston binding or worse still seizing up... Pete

 

[PSH]

Well it was very hot in the workshop today but decided to brave the heat and do a little turning on the lathe. I needed a tool to drift out the balance shaft bearings in the front housings so using a scrap piece of brass I turned up a piece that fits in the bearing shell with a small step so that i could drift the bearing out with small taps using a hammer. The same tool is then used to fit the new bearings. Picture shows the left housing with it's new bearing fitted and the tool used alongside the other new bearing for the right hand housing.

The right hand housing with the bearing half way through removal, also the old bearing from the left housing is seen alonside it's housing. I was surprised how good the old bearings were, very little wear to be seem but since the engine is in pieces it makes sense to change these things now, however I haven't changed the top hats, or should I say I'm still in two minds whether I should or not. I can always do this later if a see fit.

A close up showing the small plastic spacer washers that are important so for anyone else doing this job don't forget them, interestingly there should only be one of these fitted but the right hand shaft had three. Perhaps there had been a wear problem or during past services they just weren't taken off, this is the first time that I've worked on the shafts but the seals were changed by that specialist who messed so many things up in the past , so I'm not too surprised to find more problems. I'll check end-play later.

Final picture for tonight shows the left housing now fitted with new bearings and seals, I was going to finish the right housing as well but it looks like the oil pump needs fitting first so my next job is to rebuild the oil pump.

Pete

 

[PSH]

Afternoon all I Hope to have a busy weekend over the next few days, hopefully getting the pistons installed but thought I'd post this picture of the rods which I have just picked up from Serdi UK just in case the weekend doesn't go to plan. As usual the work by Serdi is first class, new wrist pin bushes fitted, drilled, reamed and then oil ways cleared. I'll check for balance over the weekend but when previously weighed before cleaning they were all within 1 gram of each other so I suspect they will all match perfectly without needing me to play around with them.

On a side note while at Serdi's this morning they had another 944 block on the boring machine going through the same process as mine did. It was interesting to see and I wish that I had taken pictures to show you guys, I remember when first buying my car being told it was impossible for the 944 block to be rebored, it was great to see the impossible in action.. The block was from a customer in Belgium so unlikely to be anyone here but if it was please make yourself known. Each time I go to Serdi's it's like a child visiting Aladin's cave, there was every type of high performance engine that one could think of there having the Serdi magic performed. They get a lot of Ferrari's, Lamborghini's, Aston's,Porsches etc etc, added to the old classic types and F1 cars, the list is endless. I was shown around by the engineer who was working on the other 944 block, he showed be a few damaged Diablo blocks and others that had been modified by Serdi to overcome bad designs. Evidently Lamborghini's are not very well built when compared to Porsche's and one block he had there was badly damaged from a thrown rod, looked new, scrap now. I was also shown a few Ferrari Daytona blocks that were in for work, one who's owner tends to thrash his engine was in to have all of the block stud threads heli coiled. Well I won't be back there until it's time to get the head done but I look forward to that day as it really is a petrol heads dream, next time I'll take pictures if allowed... Pete

 

[944 man]

Salisbury Road, Uxbridge, Pete?

 

[PSH]

ORIGINAL: 944 man Salisbury Road, Uxbridge, Pete?

Yep That's the one Simon Pete

 

[AndrewS]

ORIGINAL: PSH For anything that needs specialist equipment I have been using Serdi UK(01895 232215), based in Uxbridge, Middlesex, who I believe did the machining for Andrew S's famous 422bhp 2.8l stroker, as it was he who reccomended them to me, I'm sure he'll correct me if I have any of this wrong.

Hello Pete, Yes, that's correct and I spotted a couple of posts from John Daly too who still has the 2.8 (which he purchased from me in 2004 - Hello John!). Very interesting thread. Looking forward to seeing the end result, could we be looking at the UK's most powerful 944 Turbo soon? All the best. Regards, Andrew

 

[PSH]

ORIGINAL: AndrewS

ORIGINAL: PSH For anything that needs specialist equipment I have been using Serdi UK(01895 232215), based in Uxbridge, Middlesex, who I believe did the machining for Andrew S's famous 422bhp 2.8l stroker, as it was he who reccomended them to me, I'm sure he'll correct me if I have any of this wrong.

Hello Pete, Yes, that's correct and I spotted a couple of posts from John Daly too who still has the 2.8 (which he purchased from me in 2004 - Hello John!). Very interesting thread. Looking forward to seeing the end result, could we be looking at the UK's most powerful 944 Turbo soon? All the best. Regards, Andrew

Thanks Andrew Good to hear from you, it will be powerful that's for sure, not so sure on the 'soon' part though, let's hope not too long though. regards Pete