Building a 400bhp+ 2.5 ltr 944 Turbo

[PSH]

ORIGINAL: Ex Skyline Forgot to ask, who is doing your machine work Pete?

Hi Pete 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. They don't like look much from the outside, but inside is a different matter altogether, if you know your machines that is and their work is first class. General lightweight machining I can do myself at home in my own workshop. Cheers Pete

 

[PSH]

Just a small update guy's, change of plan , I decided that I didn't like silver so have now gone red, well let's face it there won't be any hiding the fact that this engine is far from standard so why hide it...

The block is hardening off now so may get more done over the weekend although Sunday's out due to other commitments but I will try to get the crank back in soon although I was waiting for the crank scraper but may have to fit that later before refitting the sump naturally. Pete

 

[robwright]

Confusing me there by turning your block upside down there Pete. PS I am now taking a completely different tack!!

 

[PSH]

ORIGINAL: robwright Confusing me there by turning your block upside down there Pete. PS I am now taking a completely different tack!!

I'm intrigued what are you up to good sir...?? Pete

 

[422hp944]

Looking good! Is that powdercoated or VHT paint? Either way it look's great!...Will be easy to keep clean too... John Daly

 

[PSH]

ORIGINAL: 422hp944 Looking good! Is that powdercoated or VHT paint? Either way it look's great!...Will be easy to keep clean too... John Daly

VHT paint John, like you say easy to clean but also easy to touch up if it gets knocked in the future.... Ooo errr.. Pete

 

[robwright]

Same car but got the offer of an engine less plumbing for turbo but basic block and bottom end at about half mileage mine is. So I figured now I have 2 engines and I have the best of both worlds. The engine will now be coming out and residing in my garage where I can play with both engines in the dry!!! The car is SORN anyway so let's make her perfect!! Well not 400 BHP perfect but it's a start.

 

[PSH]

Sounds like a plan Rob , feel free to give me a call if needed, as they say two heads are better than one. Bet you'll still be on the road before me..... I miss my car... Pete

 

[PSH]

Well i managed to find a few minutes this evening to install the Raceware main bearing studs following Raceware's instructions. All studs 10-12mm were first dry fitted to check all is ok. 10mm were fine with plenty of thread to fit the the washers and nuts but the 12mm varied a little. The instructions state to install studs by hand until they bottom out and use one drop of thread lock if wanted, not compulsory. On checking the 12mm hole depths they varied by as much as 3 mm and if screwed till they bottomed out the securing nut would not be fully screwed home. When taking the OEM studs out it was obvious that they had not bottomed out by the pool of loctite found in the bottom of each thread so I decided to dry fit the lower crank frame, unscrew a stud until the nut and washer just cleared the thread, as shown in the first picture.

The frame was then carefully removed and the stud measured to see how much was needed resulting in 76.66mm, although the studs were not fully home none of the thread was showing so still fully engaged. As a check I compared the OEM studs with Raceware's and found both were of the same length, however the Raceware nuts are a lot deeper explaining were the difference came from. Another point to note is the fact that Raceware's studs have different pitched threads for the nuts were as the OEM are both coarse thread, reason for this is that a finer thread has a lot more clamping force and therefore holding the frame better. Next thing found is that Porsche machined the block for two fitting bushes although from what I can tell only fitted the rear one. at first I thought that I had lost a bush and ordered two new ones, when it came to fitting them it was obvious that the front recess was 6mm shallower than the rear and one bush would need machining down. So I checked the parts list and found only one bush listed, so did Porsche change the design, did they have a problem using two bushes or was it quicker to fit only using one which certainly would be the case but only by a minute or so. I decided to machine one of the bushes down and see if the frame still lines up ok? Next picture shows the difference between the two bushes.

Now I could be wrong in doing this as I have no R&D to rely on and still don't know for sure if the engine didn't indeed use both but going by what I've already stated I doubt that this is the case. Anyway the result is that using one bush there is a lot of play at the front which granted would not be there once the crank was torqued down but the front ridge between upper and lower crank cases was more pronounced than when using two bushes. I dry fitted the frame using both bushes and the bearing journals line up perfectly so I'll use both bushes. Two of the stud holes had a pronounced ridge that I removed using a fine half round file so as not to damage the face. Don't think these could have happened during use although possible so suspect they had been left after the machining process, there are many rough parts that have been left unfinished, due of course to mass production.

Final picture for today showing all of the studs and both bushes fitted.

Next will be to fit bearing shells and the crank, I hope to get to this over the next few days. I know I've probably gone overboard on details but it may be of use to others for either following what I do or indeed not following if I make a mistake... Pete

 

[TTM]

ORIGINAL: PSH I know I've probably gone overboard on details but it may be of use to others for either following what I do or indeed not following if I make a mistake...

Check pictures in the Engine Build Progress thread, some showing these sleeves in the block.

 

[PSH]

ORIGINAL: TTM

ORIGINAL: PSH I know I've probably gone overboard on details but it may be of use to others for either following what I do or indeed not following if I make a mistake...

Check pictures in the Engine Build Progress thread, some showing these sleeves in the block.

your pictures seem to confirm what I suspected unless I've misread them, that being that Porsche for some reason didn't fit a bush in the front location. I decided to fit the second bush as in my mind it holds the frame in it's correct location more securely. Of course there's always the possibility that Porsche left the front bush out to give a little play when torquing down the crank and make it easier to get in-line. As I said I don't have the luxury of any R&D on this engine but I will check that when torqued down the crank is perfectly aligned to the blocks centre line with all measurements for radial/ end play being within Porsches specification. What I'm not decided on yet is whether to wait for the crank scraper before refitting the crank or do it later. I don't like the idea of doing it later for obvious reasons but may be forced too. I really hate suppliers who don't live up to their word...lol Pete

 

[TTM]

I must say this detail went way above our heads when Sly and I did my engine. At this point my only guess is that this sleeve was required at the back to possibly prevent the girdle from moving far enough to possibly mess around with the alingment of the rear main seal and make it leak? Regardless of the crank scraper I would suggest leaving the girdle torqued on the block all the time. As you may already know the factory manual mentions using an oil stone after the girdle is torqued, to compensate for the possible gap that may appear between the block and the girdle on the surface against the oil pump My 968 block had been sitting in a barn for 4 years before I bought it, but when the previous owner disassembled it and removed the crank he immediately retorqued the girdle. 4 years later, as I brought the block to the machine shop that rebored it, they observed it was a good thing that the girdle was already torqued because it would prevent unobservable movements to take place during the machining. When we finally assembled it the girdle was absolutely flush with the block, meaning no need to use the oil stone. My conclusion is that the few times girdle cannot be on the block should only be when either removing or installing the crankshaft, and otherwise always leave it on the block full torqued.

 

[PSH]

Regardless of the crank scraper I would suggest leaving the girdle torqued on the block all the time. As you may already know the factory manual mentions using an oil stone after the girdle is torqued, to compensate for the possible gap that may appear between the block and the girdle on the surface against the oil pump My 968 block had been sitting in a barn for 4 years before I bought it, but when the previous owner disassembled it and removed the crank he immediately retorqued the girdle. 4 years later, as I brought the block to the machine shop that rebored it, they observed it was a good thing that the girdle was already torqued because it would prevent unobservable movements to take place during the machining. When we finally assembled it the girdle was absolutely flush with the block, meaning no need to use the oil stone. My conclusion is that the few times girdle cannot be on the block should only be when either removing or installing the crankshaft, and otherwise always leave it on the block full torqued.

Yes that makes sense to me and one of the reasons why I had left the frame still torqued to the block (until recently) after it was machined November last year. Not so important now as the ambient temperatures are pretty stable but I probably will fit the crank before the scraper arrives, as you say it makes good engineering sense to do so but also I want to get on... Pete

 

[George Elliott]

Pete, those bushes you refer to are dowels. They are as you suggest for location which cannot be provided with sufficient accuracy by the shank of a stud. They will typically provide a location accuracy of less than a thou, maybe down to 3 tenths, 0.0003" slide fit in old money. They are among the first features to be machined on the block. When the Block/girdle were manufactured the assembly would have been put together and correctly torqued up, and mounted on a precision CNC boring machine. The alignment of the crank in the block is at stake here, and in the other plane the height of the pistons in the block when connected on the crank. Absolute critical to the engine. I would guess your front dowel is on the workshop floor somewhere. If it was missed at assembly some-one needed sacking, and you are lucky it did not move. George 944t

 

[PSH]

ORIGINAL: George Elliott Pete, those bushes you refer to are dowels. They are as you suggest for location which cannot be provided with sufficient accuracy by the shank of a stud. They will typically provide a location accuracy of less than a thou, maybe down to 3 tenths, 0.0003" slide fit in old money. They are among the first features to be machined on the block. When the Block/girdle were manufactured the assembly would have been put together and correctly torqued up, and mounted on a precision CNC boring machine. The alignment of the crank in the block is at stake here, and in the other plane the height of the pistons in the block when connected on the crank. Absolute critical to the engine. I would guess your front dowel is on the workshop floor somewhere. If it was missed at assembly some-one needed sacking, and you are lucky it did not move. George 944t

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

 

[TTM]

I don't think the girdle can slide on the block with just on dowel on, otherwise I'd have spotted that.

 

[PSH]

ORIGINAL: TTM I don't think the girdle can slide on the block with just on dowel on, otherwise I'd have spotted that.

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

 

[TTM]

Well I should also have said that I would have spotted if it could pivot around the rear dowel... Nervermind.

 

[barks944]

Looking good! Look forward to seeing the results.

 

[Ex Skyline]

Nice one Pete, block looks superb! Shame it's Red. Are you a Man Ure fan by any chance?...[]