TheDice951

i have been searching for the answers to my questions and i may have answered them but i want to make 100% sure.

i have the engine completely torn down, i will be cleaning the parts this week and will start putting it back together.

1st- the block, i heard that i need to have the cylinders coated with some paste. BUT from what i read, this is not the case? the cylinders are dirty but not scored in anyway. so all i have to do is "condition" the cylinders with a special polishing paste and felt hone?

2nd- pistons, if i go with Wossner 20cc 100mm pistons will i still need to get the coating put on? i read both yes and no and dont know what to do...

3rd- how much boost/hp can the stock rods and pistons hold? i may not need to replace the rods/pistons depending....

4th- FINAL ?, bearings, i read OEM is best but im wondering if "performance" bearings would work just as well or better???

any more input would be healpful.

i have rebuilt A LOT of engines but mainly american and japanese. this IS the first Porsche engine i am rebuilding though. i have however been all through the engines doing different jobs, i have rebuilt a few heads and have done some headgasket jobs as well.

im looking to run around 20-25psi on my gt30r with the M-tune. i will be using this as a street/track car. mainly street with weekend track days....

the reason for the "high" boost is because i feel the 18psi i run now with vetesse SW seems slugish and i want more responce and power, hense the M-tune and higher boost. im thinking with a fresh engine and the M-tune it should feel much better at 18psi anyway so really i am wanting to build the engine with the ability to run 25+psi...

ready to take it all in!! bring it!!

magcuda

I've done a lot of Porsche motors and never used any paste on the cyl walls. Matter of fact just clean the walls, don't hone them. In the workshop manual it gives a step by step cylinder hone using a Sunnen honing machine with special grit stones, but I haven't had to do it. You use the wrong stone and it damages the coating.
20-25 psi of boost??? you are going want to get a heavyduty head gasket and O ring the block

TheDice951

I was thinking about o-ringing the block, the engine currently in the car is o-ringed. Like I said before With the fresh engine and new software I may be content with 18 psi still... I want the option though if I feel I need a bit more

TheDice951

BTW

Thanks for your info!!

TheDice951

Anyone else have any input??

xsboost90

stock rods are good supposedly to about 450hp but i wouldnt push them past 400. I ran my car up to 22psi on a cometic head gasket and had no issues with a rebuilt stock longblock but thats my experience. Tuning is what i would worry about more than pressures. Run it lean and it will melt the head gasket, valves or pistons quickly. I ran good bearings from paragon or rennbay and i always try to stick to a std bearing and make sure the crank is mic'd for standard and is polished. I usually just clean the pistons and bores with some atf on a cloth and always use stock/porsche rings.

CDH-CTT

Im built my engine with stock rods and pistons just recoated( better rings), the head has been gone through, high rev springs, bigger valves, gasket ported and polished, ceramic inserts have be smoothed out, and the head has been o-ringed( a local guy here does a ton of Porsche machine work) I'm still just going to run a Widefire HG ...but Im not looking for anything crazy just 18 psi MAX with a K27/29 with a #8.... +/- 350hp I would be happy with... Just check the stamping on the back of the bearings to make sure what size they "really" are.... Good time to upgrade the crank and install an oil baffle

Good luck with the build

blown 944

Regular fuel?

Like others have said just cleaning the cylinders works.

IMO the rods are pretty good, however they can be bent if tuning is off. Keeping the rpms down also helps IMO.

I don't know the pistons but if the are not coated with the factory metal type coating that will need to be done.

Also pressure isn't everything, you may think about having the head worked a little while it's apart.

toddk911

Yes! A/F and timing spot on and proper octane and a lot of boost (20+) is safe.

fast951

TheDice951, when the car is running rich it will be sluggish. Did you ever figure out why your car was running so rich. Did you backtrack to see what the previous owner did and/or correct existing problems? I emailed you multiple times suggesting what to check, but never did hear back from you.

As I recall, you purchased the car that had the parts on it, and it was a older setup. Were you running 18psi on pump gas? If so, you were operating outside the parameters and possibly the KLR was pulling timing??

When parts exchange hands, it's a good idea to go over the basics just to make sure everything is installed and operating properly. Not to mention following the recommended settings for the particular setup.

Stock rods will hold up fine. Just make sure you have them checked for any existing cracks. The stock pistons are good quality as well, make sure they are within spec.

reno808

....

TheDice951

fast951, I believe I emailed you back? I did look at everything you told me and it turned out the aftermarket FPR was set wrong. It smokes now because it’s burning oil from the turbo. I’m sure the car feels the way it does because of the leaking turbo and the age of everything.

I’m rebuilding the head and do plan on doing some work to it for a bit more flow.

My wife just surprised me with a nice k-27/6, literally just now, like in the middle of me typing this...lol so I will be replacing my leaking turbo with this nice piece this weekend!! Maybe

So the stock pistons and rods are good? What benefits would I get with aftermarket pistons and rods? i know they are stronger and can stand up to more pressure and HP but how much better are they compaired to stock?

fast951

No never did hear back from you. I have seen many adjustable regulators fail, which is why I recommended replacing it. Glad you got it sorted out.
If you were getting oil in the intake, it lowers the effective octane rating of the fuel, which causes knock. When there is knock, the KLR pulls ignition out (as it should), which causes the car to be lazy.

Stock pistons are fine, for your application. I'm not sure what you would gain by going to aftermarket ones. Of course, you must measure the stock pistons to make sure they are in spec.
Aftermarket pistons are a bit lighter, but the 944 engine is not a high revving engine, so the gains from the few grams saved are questionable.

Aftermarket rods are lighter and in some cases stronger than factory rods. All the factory rods "I have seen" are forged, some claim that some 951 rods are not forged. So if you have the forged rods you are fine, unless you are running huge HP/TQ and constantly revving the heck out of the engine.
Stock rods, they must be checked, especially for cracks. Finding a machinist with the correct equipment to test the rods may be tough. In your area (maybe Raleigh) there are a few performance shops for domestic engines. Call a few and see who has Magnaflux equipment. That would be a good start...

Of course, if money is no object or you need new parts anyway, there is nothing wrong by going to aftermarket pistons & rods.

Congratulations on the K27/6.

TheDice951

sorry for not getting back to you. im in the military and have a few friends that work NDI (Non-Destructive Inspection) they test Jet Engine parts for microscopic cracks and such so i can have them test my rods if need be.

if my pistons are within limits do i need to get them coated? if so where can i get that done? machine shop?

GARG

Speaking of pulling the timming. Is there an output of some sort we can get an indication of this happening to hook up to a light.
tks Gary