Piston & Rod upgrade or not?

slickv8 · Nov 7, 2016

Hi All, long time since I've posted. My 944T had popped a conrod while being dyno'd so I've had to source a new engine - now got one so I'd appreciate bouncing a few ideas off you before its re fitted to my car.

So to give you an overview; my plan is to build a fast road/track widebody 944T. I'm shooting for a torquey power delivery and expect around about 300hp. I've stripped the car, new adjustable shocks, Custom made 3" SS exhaust, oversize injectors, race fuel pump, 3bar regulator, new DPW, ceramic coated manifolds and a newly rebuilt k26/8 turbo, short shift, LSD... so it should be pretty swift! Its also got a widebody kit painted and sat waiting to be fitted over the winter and some deep dish custom wheels.

However I'm in a quandary over the engine and how far to go with it. I dont have limitless funds [taken 3 years to get this far!] The engine I have sourced has an excellent service history and was apparently much loved prior to its donor car being side swiped and Insurance written off. I heard it run and it all sounded sweet, I'm confident I could have just dropped it in the car and got on with getting on...As a matter of course I'm going to fit a new widefire head gasket & valve guide oil seals but I just cant decide whether or not to go with upgraded [wossner?] pistons and/or rods and also a lightened fly wheel? In my heart (and with unlimited budget) i know i'd do it but the extra couple of £000 it'll cost isn't just sat in my back pocket. I've no problem coming back to doing this in months [years] to come but the fact is the engines sat on a bench right now so access is relatively painless.
Do you think if i ever sold the car i'd recover the investment of Wossners or am i spending money that'd be better used elsewhere on the car?
Or would a rebuilt engine with standard internals be equally appealing/value?

As far as the lightened flywheel goes, I'm thinking it'd spin the engine up faster giving faster response but i cant find too much data on this. Being that the engine is on the bench, changing it doesn't appear to be a major financial consideration but i dont want to ruin the drivability for the sake of just doing it and likewise dont want to miss opportunity for a possibly effective upgrade?

Thanks in anticipation...

blade7 · Nov 7, 2016

I'd check what rods are in the engine you've sourced, if they're cast a fairly cheap upgrade is a set of used Rarst forged rods from an early turbo engine, have them properly checked over though. As for the pistons, if they look undamaged and the bores are in reasonable condition I'd stick with them. 300 bhp is fairly unstressed from properly tuned turbo engine running up to 18 lb boost.

edh · Nov 7, 2016

Doesn't seem that necessary for a 300hp car - easy enough to get there on a standard engine with DPW and a 26/8.. No experience with a 944 LWFW though, sorry.

Worth bracing the oil pickup tube while the engine is out.

PSH · Nov 7, 2016

As stated above, for 300 BHP you don't need to go overboard with these engines, 300bhp is pretty tame. I would bet that it was No.2 rod that failed as this is the weak point. If your new engine has the forged rods (early cars) there's no need to change them, you won't find much better IMHO, I would, however, check out the wrist pins for wear, especially if you plan more power.

Ditch the idea of a lightened flywheel, you need that engine braking power. If you want things to spin quicker fit a crank scraper, it's easy and it's cheap and from my experience makes a big difference in how the car responds to the throttle, it also means you can run with less oil if required.

Also, bear in mind if doing a rebuild that any crank work will involve undersized bearings and these are very expensive (only use genuine) , if the bores need doing I can recommend oversized IASA full race spec pistons.

Regards

Pete

Pete

924Srr27l · Nov 7, 2016

Hi Slick,

My 944T had popped a conrod while being dyno'd

Was this a stock engine or modified? also what Mileage?

my plan is to build a fast road/track widebody 944T. I'm shooting for a torquey power delivery and expect around about 300hp. I've stripped the car, new adjustable shocks, Custom made 3" SS exhaust, oversize injectors, race fuel pump, 3bar regulator, new DPW, ceramic coated manifolds and a newly rebuilt k26/8 turbo, short shift, LSD

I had many times in my 3.5 year project where a decision was needed on many sections of the car's performance, and it would seem your also unsure what to do?

With most Automotive projects it's easy to knock up a large attractive spec list but then realise

the expense can soon run away, you need to ask yourself what you want at the end of it ? and what could be the worst case scenario if you do decide to go Budget, or Semi Budget rather than the ultimate.?

- Budget, leave it alone and put it in and run it

- Semi change a few items Hone & Rings ? Rods& Pistons?

- Ultimate, a Full rebuild, tuning and fit different and lighter to OE components.

I went for the middle one, but then this escalated and then became a full rebuild and

no stone unturned!

So there' a lot to be said for leaving it, any tuning to an old used stock motor will put it under more

stress than it's had previously and it could blow, but then plenty are subjected to this treatment

so it might be fine! ?

I don't know how much the Turbo Horsepower engines lose power in time and age? but for example a 3.0S2

can be in the 180's for Horsepower and the Book spec is 208, many 2.5 8V N/A engines are only pushing out

bhp in the 130.'s and NOT the 160's.

My point being this Engine may of ran great but could be down 10% + due wear bore / Rings? and if so any tuning

will put more wear on it, this is what I was faced with, doing a little without Everything being 100% can cause

other problems so.........I didn't want no gains so I delayed the project further , saved up and went for the Lot !

Many times I felt I'd gone excessive and why was I Spending so much, however once the car

was finished and I've done over 2000 miles in it now, I would never do anything again other that the Full works because the final effects and results are simple staggering, and any half way house would of been just that!

I took advantage of the Dollar (At the time, Not now the Brexit thing has made a mess of it) and bought an engine

that was sourced and tuned in the USA from Lindsey Racing.

2nd hand

- 3.0 944 S2 Block - Checked to be a great bore shape + a Hone to 105mm

- 2.5 951 Crank - Full Race Lightened (Knife edged) 3Kg loss!

- 968 3.0 Conrods Balanced & Modified to fit

- 944 2.5 8v Cylinder Head (Stage II Inlet porting) + 28% more flow (CFM)

- 944 2.5 Inlet Manifold (Extrude Honed)

- 944 1/2 Lobe Racing Balance shafts

- Live Mapped by someone that really knows how to extract the maximum

from these Engines. (Chip Wizards - Wayne Schofield)

Fitted with Brand New Wossner Pistons 105mm CR 10:9:1

Capacity 2707cc

- Spec Stage II Clutch

- Spec Aluminium Flywheel

Everything was balanced including the crank / clutch & Flywheel together

205bhp / 205ft Lbs and a great 190 Ft Lbs @ 2850rpm

The car also went through a Huge 250KG Weight loss, so it's the same Power to weight ratio

as a (stock weight) 944 Turbo modified with a Genuine 300bhp, but will be faster on the road as

the Engine Spins up quicker than stock due to the lightweight crank / flywheel & Pistons etc... And the

body is less draggy (924) and the unsprung weight is less (Wheels / tyres / brakes)

The Lightweight Engine components do NOT produce more power but they make the car quicker from point A to B compared to non lightened Spinning components.

I was concerned about all the weight loss would make it drive difficult and I read loads of things on the net about

loss of inertia and tricky to pull away etc...

The reality, (which I think my 250Kg weight loss has helped) is nothing is difficult or a problem whatsoever!

If your close or fancy a Drive to North Wales I can Demonstrate! I'd be 99% sure you'll want to replicate the same or have more! and this car is normally aspirated....

It does however lose speed quite rapidly when the throttle is off, but this is not an issue because the upside of the

quicker upshifts and the way it whips up the RPM is a Huge advantage.

There's lots of pretty pictures on the car's build website : www.924srr27l.co.uk

So to conclude, don't touch this engine (LOL)! else like me you'll end up spending thousands!

Roger

924Srr27l · Nov 7, 2016

PSH said:
Ditch the idea of a lightened flywheel, you need that engine braking power.

Regards

Pete

What is this ? and what does it do?

R

PSH · Nov 7, 2016

sorry it was me being a bit sarcastic......do you really want a kangaroo effect each time you change gear? it's a balance and a matter of what type of drive you want, lightened flywheel is not good for road use, well not unless you like the car bucking when lifting off. Don't get me wrong, my flywheel is lightened but it's not a full-blown custom affair. The 944 (especially the turbo) has relatively long legs which is not ideal for lightened flywheels, you need that inertia when changing gear. If you want a lightweight just get the standard flywheel skimmed down to minimum. IIRC this is just under 25mm and add a crank scraper. My own car is very responsive but then the upgrade list is very, very long in both items used and development span.

Pete

924Srr27l · Nov 7, 2016

PSH said:
sorry it was me being a bit sarcastic......do you really want a kangaroo effect each time you change gear? it's a balance and a matter of what type of drive you want, lightened flywheel is not good for road use, well not unless you like the car bucking when lifting off. Don't get me wrong, my flywheel is lightened but it's not a full-blown custom affair. The 944 (especially the turbo) has relatively long legs which is not ideal for lightened flywheels, you need that inertia when changing gear. If you want a lightweight just get the standard flywheel skimmed down to minimum. IIRC this is just under 25mm and add a crank scraper. My own car is very responsive but then the upgrade list is very, very long in both items used and development span.

Pete

Ok I thought it sounded weird, Engine braking a good thing which it might be if your Disc Brakes were poor?

- Kangeroo effect when changing gear?

- Bucking when lifting off?

- Need Inertia when changing gear?

- A turbo responsive?

Blimey, here's some bizarre thoughts you have!

I will say I read so much what I' now call (Tripe) about lightened cranks and flywheels on the net...and several times

and even up to driving the car for the first time in 3 years I was concerned, but it was all for nothing!

There is no Kangering or rooing, or bucking ? when changing gears up or down the box and I'm on softer springs than you?

(190 lbs / 220 lbs Front /rear) but then I'd estimate I'm 350Kg+ lighter

Inertia is a great thing to have with a road car as the heavy Crank and flywheel have so much energy they continue spinning

for so much longer compared to a lightweight set up like mine where when you lift off the car's RPM decreases more quickly.

For road use your long legged gears and heavy crank make for easy motorway cruising, my car's RPM will accelerate much faster due to the

lightweight crank, rods / pistons and Flywheel it's normally aspirated like all the great car's !

(McLaren F1 and the new V12 Aston martin Red Bull road car etc...)

So it has no Lag at all, less Unsprung weight (lighter wheels / tyres / brakes) and also less Sprung (Body) weight,

Sure I don't have three hundred and whatever horsepower you have? but I really would be up for a drag race with such a car as it could be surprisingly quicker .

Talking of quicker the gear changes up are brilliantly fast, the 944 Gearbox (3.889FDR) is nice and short and built for acceleration and I can literally

slam the gear through as fast as possible and it's in no crunching etc... changing down also no issues whatsoever..

R

slickv8 · Nov 8, 2016

Hi all, thanks so much for your input. [Roger] the car was actually being dyno'd by Wayne @ chip wizards when it popped so I'm happy its being tuned properly... i've family in Chester so i might just take you up on the road test!

As your all surmising my mind is stuck between a rock and hard place..I did a '73 RSR backdate a few years ago and i cant tell you how much that cost me to finish...it was nice though!

So with the 944 I want a fast, reliable track car. My play time is quite limited so i need it to just start and go on demand but equally if opportunity knocks I'm as likely to jump in it on a thursday night and head south for a schlep around the 'ring [love the journey too much to trailer it] thus the aircon and a bit of carpet are staying as a nod to comfort.

Reading your comments has got me thinking though...I'm keen to get it finished so i think I'm going to give the std engine a light rebuild and get the car 'externally' finished then plan a more comprehensive engine build for the future when i can get it all done at once.

I'm basing this on the assumption i should get a quick, fun car as it is now, with the few new bolt-ons already done.

Adding rods wont [at this stage] give any tangible benefit without also looking at the pistons, then lightened, balanced crank and on and on....so for the cost of dropping and refitting the engine again i think i need plan for an extra £5k+ to do a 'proper' job at some stage in the future? As i cant spend that this winter [apparently my kids are expecting christmas presents that dont also fit on a 944 for a change[

]] I'll do that and as a bonus i get to spend some happy winter nights getting the thing looking awesome too, decision made....thank you!

924Srr27l · Nov 8, 2016

slickv8 said:
Hi all, thanks so much for your input. [Roger] the car was actually being dyno'd by Wayne @ chip wizards when it popped so I'm happy its being tuned properly... i've family in Chester so i might just take you up on the road test!

As your all surmising my mind is stuck between a rock and hard place..I did a '73 RSR backdate a few years ago and i cant tell you how much that cost me to finish...it was nice though!

So with the 944 I want a fast, reliable track car. My play time is quite limited so i need it to just start and go on demand but equally if opportunity knocks I'm as likely to jump in it on a thursday night and head south for a schlep around the 'ring [love the journey too much to trailer it] thus the aircon and a bit of carpet are staying as a nod to comfort.

Reading your comments has got me thinking though...I'm keen to get it finished so i think I'm going to give the std engine a light rebuild and get the car 'externally' finished then plan a more comprehensive engine build for the future when i can get it all done at once.

I'm basing this on the assumption i should get a quick, fun car as it is now, with the few new bolt-ons already done.

Adding rods wont [at this stage] give any tangible benefit without also looking at the pistons, then lightened, balanced crank and on and on....so for the cost of dropping and refitting the engine again i think i need plan for an extra £5k+ to do a 'proper' job at some stage in the future? As i cant spend that this winter [apparently my kids are expecting christmas presents that dont also fit on a 944 for a change[]] I'll do that and as a bonus i get to spend some happy winter nights getting the thing looking awesome too, decision made....thank you!

Yes it's not an easy thing to do once you start thinking of how far to go the project is delayed further

and the spends keep coming! unyet I kept telling myself if I'd gone this far, (carry on) as there's no rush otherwise the

car will have some weak area's if I'd skimped which I know would annoy me.

Sure, give us a call or mail if your in the area.

R

PSH · Nov 8, 2016

I think £5k for a 'proper job' may be a bit light, think mine came in around twice that and I did the rebuild myself which saved a lot of money but then what's a 'proper job'? to me it's just doing whatever work is being done properly, that doesn't mean it needs to be some all power monster, you can do a proper job and still have the engine as 'standard'. It's good to know that Wayne is still around, I haven't spoken to him in some time and will need to get my car back up to him when time/money allows. Technically, I'm still on a 'running in map' with the smaller 55lb injectors and standard ignition, not using fully the new MAP sensor installed as per my request, I have some very nice base maps including an aggressive ignition map to try once the 80lb's are fitted and then I need to get the car to Wayne, there is no one else to match him IMHO.

Pete

slickv8 · Nov 8, 2016

haha, yep i can see where these mods can get way out of hand...although I'm relatively confident i wont be spending £10k on it anytime soon [famous last words!] i really need get over this old Porsche addiction and buy a push bike!

slickv8 · Nov 8, 2016

[attachment=IMG_1407.JPG]

slickv8 · Nov 8, 2016

PSH said:
As stated above, for 300 BHP you don't need to go overboard with these engines, 300bhp is pretty tame. I would bet that it was No.2 rod that failed as this is the weak point. If your new engine has the forged rods (early cars) there's no need to change them, you won't find much better IMHO, I would, however, check out the wrist pins for wear, especially if you plan more power.

Ditch the idea of a lightened flywheel, you need that engine braking power. If you want things to spin quicker fit a crank scraper, it's easy and it's cheap and from my experience makes a big difference in how the car responds to the throttle, it also means you can run with less oil if required.

Also, bear in mind if doing a rebuild that any crank work will involve undersized bearings and these are very expensive (only use genuine) , if the bores need doing I can recommend oversized IASA full race spec pistons.

Regards

Pete

Pete

I'm quite intrigued by the crank scraper suggestion. a quick google and theres Paragon products at $79 or crank scrapers.com seems to be $600odd. Which are you running and are they a simple bolt in mod?

thanks

PSH · Nov 8, 2016

There are a number of types out there, I have one by Ishihara-Johnson who do a variety made from different materials. I chose the steel scraper which will be the cheaper option, Teflon costs more. For the steel version, you need to custom fit the scraper with use of a hand file to remove unwanted metal to give clearance for the crank, if you are fitting such to an old engine don't make the fit too close as you may find the crank has excessive endfloat and will foul the scraper. The Teflon type is a much easier affair to install , fit, run engine and let the crank do the cutting, teflon being easily cut by the rotational mass of the crank, no damage is caused to the crank btw. Don't be put off with the steel version, it takes just minutes to file to fit, most of the profile is already there. Both types are very easy to install if doing so during a full rebuild, I wouldn't like to try it with the engine still in the car.

This is the website.. http://www.crank-scrapers.com/Porsche.html

They have a lot of written detail as to the benefits of using a scraper, ie some engines at high RPM can have the entire contents of the oil pan stuck around the crank, that's a lot of weight/mass and thus 'drag' to be spinning around your engine.

Now the 944 engine has a design flaw in it's oil supply which effects mainly No.2 rod bearing, a scraper will greatly if not entirely remove this flaw from the equation as it stops the oil becoming entrained with air bubbles . Your engine will rev quicker, be more responsive and safer to drive hard. It's difficult for me to quantify exactly which particular mod did what on my latest rebuild as so much has been changed but I can say that the car's response has changed remarkedly and I feel that most of this is down to 3 things, the scraper, the lighter flywheel and the throttle body rebuild with race seals installed.

regards

Pete

[h1] [/h1]

924Srr27l · Nov 8, 2016

On the 104mm block from 1989 (2.7) and then the 3.0 S2, Porsche modified and changed the block design from the 2.5.

They not only added a "Windage Port" for more power and reliability, but also reduced the blocks weight by 5kg,

with less waterways.

Scroll down almost 3/4 on the link below to see this mod can be done to 2.5 blocks as this example from Lindsey Racing USA

http://www.lindseyracing.com/hptalk/0808.htm

Also the 2.7 / 3.0 S2 Sump design had a different sump part crank scraper baffle

See here, just over half way down there are two photos pre 89 and after.

http://rennlist.com/forums/944-turbo-and-turbo-s-forum/341799-i-m-still-confused-about-updating-an-86-oil-pan-baffle.html

R

Dan944t · Nov 9, 2016

Hi Pete,

im currently rebuilding my 944 turbo as I had a cracked cylinder and that was not long after a top end rebuild and loads of nice mods, but I am now doing the lot including having my bores milled down and racing wet liners installed along with new racing rods of some sort when I source them and already have some racing pistons to put in. I'm having everything balanced together after.

i am am considering having my flywheel lightened slightly? But didn't want to go too mad, could you or anyone r commend a good weight for road use that will not ruin the gear change too much as I've heard allot of bad stuff on the net but didn't want to believe all the negativity?

also coukd you elaborate on your throtle body rebuild as I'm unsure what it consists of? I have a contact that will hone and polish my standard body and I believe he said he will install a new butterfly.

I am new to the forum and this is my first post but I have owned a 944 since the age of 17 and I'm 36 now so dont know why I havnt found this forum up till now as I sure could have done with it years ago!

thanks daniel

PSH · Nov 9, 2016

Hi Dan... I have tried to search for my build thread as iirc I covered it all on there along with complete details of the development of the car, alas I have failed to find the thread...lol

Re flywheel this needs to be done carefully, I think I had around 2mm removed, whatever it was it was a fraction under Porsche's stated minimum , the last thing you want is the flywheel to burst, this can happen and it can kill, so don't go overboard a well modified Turbo kicks out a lot of torque. If you want to loose more weight better to buy a steel or alloy alternative. I'm not a fan of losing so much weight but it's a personal decision.

Re throttle body there's a kit available that replaces all of the factory seals as believe me I guarantee that every 944 out there with the originals is leaking, turbo or N/A. My seals literally fell apart when taking the thing apart, I didn't open it body up at all but some do, I just polished it and kept the original butterfly. In the kit (might be Armworx but can't remember) you get two sets of seals, direct replacements and what they call race track seals, the difference being the later give a better seal which is ideal when using high boost, however there's a trade off as the throttle doesn't always return to total idle with these seals fitted. I haven't had many issues with this, it usually closes as per normal with the odd accoasion when it might sit a little higher at around 1000rpm, a blib of the throttle usually clears this.

Perhaps some other kind forum member can operate the search function better than I and post a link.

Hope that answers your questions and welcome to the forum, you should be able to find the answers that you need here, they're a friendly bunch...

Pete

blade7 · Nov 9, 2016

slickv8 said:
[attachImg]https://www.porscheclubgb.com/forum/download.axd?file=0;942560&where=message&f=IMG_1407.JPG[/attachImg]

You'll need some big wheels to fill those arches [

]

PSH · Nov 9, 2016

aha..at last I found the thread...the forum search engine is useless...lol anyway here's the link to my build Dan...hope it helps.... https://www.porscheclubgb.com/forum/tm.aspx?m=705721&high=PSH

Pete