Engine Refresh

[GPF]

Hi All,

I've been trying to decide for ages whether to have Ferdie's engine out and give it a refresh - new rings, bottom end etc. It's done 150k and there has always been just a little bit smokey from time to time - nothing worth worrying about at all but you know it's there.....

The next service was belts which crystallised things and so I took him off the road about 2 years ago - just for the winter......... and he's been SORN'd ever since!

However, I finally bit the bullet a couple of weeks ago so he is now staying at the local OPC hotel for a while

The engine is out now and I'm trying not to think of too many 'while you're in there' jobs/mods but - it's hard not to!

Bores are fine, so it's rings and bearings plus a clutch while it's out. Water pump too of course and spend a bit of money cleaning and painting/powder coating a few bits like ARBs, hangers etc. and clean the engine bay.

I keep thinking 3 litre crank and new rods to go 2.8 but I've resisted so far - he really doesn't need it and I've no intention developing him much further.

However, a lightweight flywheel keeps calling me.......

Anyone have any experience of this in a 944 Turbo?

Anything else I should be considering??

 

[924Srr27l]

Lightweight Flywheel is quite a Touchy Subject, as are cranks !

I went for both but as any changes it was a risk, however they both turned out to be a brilliant decision for my application
but only because I also had a massive vehicle weight reduction (250kg)

On a stock 952 car, with a lower Comp ratio, forced induction and the longer ratio 3.374? Gearbox...

I'd probably NOT recommend it.

These cranks are are Big and heavy but this gives you great inertia, a Large heavy spinning mass on tickover means you don;t need much throttle application to pull away, but you will require more RPM if you lighten the Flywheel and with the Turbo Lag, & longer box this will have an effect which you may not like, which would be annoying if you get the car back from the engine refresh and it's no longer enjoyable.

In contrast a High Compression N/A with a short ratio gearbox and probably 400kg less vehicle weight than a 952 it does not have any issues at all with not only an Aluminium lightweight Flywheel but also a lightened Crank / pistons and rods, a Total loss of spinning mass is approx (10kg) and this is the shorter stroke 2.5 crank but with a big bore 105mm.

The upsides are the engine increases it's RPM's much quicker than stock, and gets to 60 and 100mph much quicker
The flipside of this is when you lift off the throttle it has very little inertia and it slows up (The RPM needle drops quicker & dies) much quicker which is not an issue as it saves wearing out the brake pads!

Stick it all back as it....

R

 

[TTM]

Very pleased with my lightened standard flywheel (-1.6kg).
As the engine drops revs quicker with a lightened flywheel, the gearbox will have to be smooth enough to allow for quicker gearchanges - synchro ring condition? Oil quality?
If you keep the standard heavy rods then perhaps your engine won't drop revs as quickly as mine but I'm sure your standard gearbox should still allow for gearchanges that will be quick enough if you lighten only the flywheel. Even on a 100% standard turbo I would recommend lightening the standard flywheel.

 

[blade7]

Have another read of PSH's rebuild thread, plenty of good info in there. If there's even a hint of a ridge at the top of the bores there's likely to be some ovality/taper present. How much effect that has I don't know. My spare 2.7 block doesn't have a mark on the bores but it's got around .001" ovality, I'll probably get someone like Serdi to measure it properly and take their advice on whether to have it machined. If your 2.5 block is stripped I'd consider having some windage ports machined in too. Or you could just go to 3.0 [].

 

[blade7]

You most likely know, the best way to go to 2.8 uses a 3.0 crank, standard length rods and custom pistons with the gudgeon pin moved up to compensate for the increased stroke. For custom pistons you're probably limited to Wossner, and unless you can provide them with a drawing you will be at the mercy of the septics and a £1k+ bill.

 

[edh]

..might happen to know the whereabouts of a 3.0 crank...[]

 

[924Srr27l]

Have another read of PSH's rebuild thread, plenty of good info in there. If there's even a hint of a ridge at the top of the bores there's likely to be some ovality/taper present. How much effect that has I don't know. My spare 2.7 block doesn't have a mark on the bores but it's got around .001" ovality, I'll probably get someone like Serdi to measure it properly and take their advice on whether to have it machined. If your 2.5 block is stripped I'd consider having some windage ports machined in too. Or you could just go to 3.0 [].

Isn't a 2.7 Block the same as the 3.0 ?

Do you mean if it's Machined , it will then be Steel lined ? I thought you can hone Alusil but once machined it's lost it's Silicone content?

R

 

[924Srr27l]

You most likely know, the best way to go to 2.8 uses a 3.0 crank, standard length rods and custom pistons with the gudgeon pin moved up to compensate for the increased stroke. For custom pistons you're probably limited to Wossner, and unless you can provide them with a drawing you will be at the mercy of the septics and a £1k+ bill.

Or 2.7 Litre
- (short stroke) 2.5 Crank, 3.0 Block, & 2.5 Head
Lindsey Racing did mine with Wossner pistons CR 10:9:1 (2707cc)

R

 

[blade7]

..might happen to know the whereabouts of a 3.0 crank...[]

You'll need the 3.0 crank damper to go with it though....

 

[edh]

Well I know that's somewhere in the garage....just haven't had a spare day to have a good sort out ..

 

[TTM]

Well I know that's somewhere in the garage....just haven't had a spare day to have a good sort out ..

Please remember from the "Spares listing" thread that you were going to look if you had a spare crank damper for me

 

[edh]

I remember Thom... I don't think Graham was seriously contemplating a 2.8 build.
Lift is pretty hectic at the moment ( although I have 3 days of for a track day at a nice little place in Germany next week )

 

[PhilKent]

My advice would be replace the turbo!
I did an engine out full strip and re-build back in 2009 at roughly 150k miles due to slightly smokey engine, only just run in now as I don't do that many miles. I didn't replace my turbo (or have it re-built), I checked the play in the bearing and they were within tolerance acording to the specs, however I ended up with a still smokey engine. Replacing the turbo is WAY easier with the engine out! A nightmare with it in I think. I went for a Lindsey Racing turbo myself. Again the turbo took some miles to run in and the car has come alive now. I love it.
I didn't go for any 'fancy' bit and pieces and don't regret it, the stock engine has always felt strong, balanced and I'd agree with other comments regards the inertia at low revs being a bonus.

 

[blade7]

My advice would be replace the turbo!

Click on the blue text at the bottom of Grahams post [].

 

[blade7]

Well I know that's somewhere in the garage....just haven't had a spare day to have a good sort out ..

Crank without the damper is a pointless buy IMO.

 

[924Srr27l]

GPF "Anything else I should be considering??"

Lightweight wheels? will make the car faster...

R

 

[924Srr27l]

Well I know that's somewhere in the garage....just haven't had a spare day to have a good sort out ..

Crank without the damper and vice versa is a pointless buy IMO.

Why is it so critical on the 3.0 and not the 2.5 & 2.7 ?

R

 

[Diver944]

Good to hear from you Graham and great to hear that Ferdie will rise again. Is it Leicester doing the work, and what sort of timescale before it's finished?

 

[PSH]

Have another read of PSH's rebuild thread, plenty of good info in there. If there's even a hint of a ridge at the top of the bores there's likely to be some ovality/taper present. How much effect that has I don't know. My spare 2.7 block doesn't have a mark on the bores but it's got around .001" ovality, I'll probably get someone like Serdi to measure it properly and take their advice on whether to have it machined. If your 2.5 block is stripped I'd consider having some windage ports machined in too. Or you could just go to 3.0 [].

Isn't a 2.7 Block the same as the 3.0 ?

Do you mean if it's Machined , it will then be Steel lined ? I thought you can hone Alusil but once machined it's lost it's Silicone content?

R

Alusil blocks can be machined but there are very few companies with the knowledge/operating procedures and correct tools to do this, Serdi UK being one of the few in the UK. If you use the standard method/cutting pads you'll destroy the engine as they will dig into the alloy. Alusil is not a coating as some think, it's impregnated into the block itself and then etched in the factory to bring the silicon crystals to the surface, the rings basically run on microscopic rocks that are extremely resistant to wear. I can't recall the full process but you must have the correct cutting pads and paste and you must leave more material on the bore before the final hone, something like 3 times the normal IIRC, Serdi will be the best people to talk to on this. My own bores are now 101mm, IIRC this and the piston dish gives me something like an extra 60cc capacity, I would check in my build thread but I'm useless with the search engine....lol...it's all in there somewhere


Pete

 

[924Srr27l]

Ok, Interesting info, although my 3.0 block was honed and each bore is also 1mm oversize @ 105mm Which Lindsey Racing did
but i wasn't aware it was nothing other than a hone, unless they did as Serdi do, only 1mm is a lot of material ?

R