murrayg

Hi everyone,
A while back I bought a rough 89 S2 with a noise (subtle knock – oil pressure good) in the motor. My plan is to use the drive train in my 84 after a rebuild of the 3.0L engine. Mostly a street car, but a few track days a year. After finally removing and tearing down the engine, checkout the photos of what I found. I've also discovered that parts (pistons) for a non-turbo 104.5mm 16valve is limited.


My Options:
1: Overbore and use OEM pistons for Alusil cylinders ($2500) – not really an option, I just put it here as a joke!
2: Overbore and use JE / Mahle / Wossner for Alusil (set of 4 = $800 – $1000) Any preferences here??
3: Cast Iron sleeve and use regular pistons. Not sure of the availability of NA 3.0L non Alusil pistons.
4: Iron sleeve and fit SBC pistons – Anyone know anything about this option?
5: Sell a perfect 3.0L std crank, head and cams and put the money toward an LS1. Really don’t want to go down this road but what can I get for the crank, head and cams?

Any engine builders with advice is appreciated. Actually, all comments welcome (except on how good the 84 would be with the LS1)!

cheers!
Gord.

Jfrahm

A good used engine is generally the cheapest and IMO the option most likely to be successful. A factory motor in good shape will have good rings and bores for 300K miles. Overbores, plating, sleeves etc. are expensive and have a good chance of misadventure. If you spend enough money to buy a good used running 968 you might get one of those solutions to work out.

With S2 motors you can find them with a bad head for pretty small money (probably under $1500) or get a good runner (under $2500) and part out what you have.

-Joel.

V2Rocket

Re: SBC stuff

https://rennlist.com/forums/944-turb...44-design.html

murrayg

V2, that's a really cool engine build! I've been following it, but it is for a 8 valve head and low compression for a turbo. Mine is a 16 valve head and high compression, both of which complicate it somewhat.

V2Rocket

There are so many piston options that you could find one that would suit you

murrayg

ya, the SBC world is quite a bit bigger than ours! I built a 350 for an 80's vette last year and paid less than $100 for all 8 pistons!

944meister

i had the exact same problem with my S2 engine, in my case it was only cylinder #4 that was severely scored like the pictures you posted above. before you do anything, check to make sure your cylinders are not cracked! cylinder #4 in my block was cracked and not repairable. with that said, after you varify that you dont have any cracks, i have a set of brand new Wössner pistons and connecting rods from my rebuild that fell through, that are much lighter and stronger than stock. this way you dont have to wait weeks for the pistons to be manufactured, pm me if interseted. the piston specs are stock and 10.9:1 compression (same as factory), however they are coated for use in Nikasil or steel sleeved cylinders and have the appropriate piston rings. if you are not aware, Nikasil is what they use in the 911's and is significantly more durable and scratch resistant than our Alusil bores. to get your cylinders Nikasil coated you would have to send your block out to 928 motorsports, but in my honest opinion it is the best way to rebuild these engines.

BisimotoSales

Greetings murrayg,

Bisimoto Engineering can gladly assist you with a set of custom oversized forged pistons designed to be used with your factory Alusil sleeves.

Bisimoto has spent many years working hand in hand with the engineers at Arias Pistons bringing new technology and innovation in piston design. With benched flowed crowns for improved flame travel, CNC machined from the highest quality aluminum to provide a lightweight design without jeopardizing integrity and have spent a countless amount of time working with piston coatings to improve effiency.

Bisimoto Spec. forged piston kits utilize ceramic coating on the crown to retain thermal energy within the combustion chamber and a moly-based coating to greatly reduce internal friction, while increasing piston life. From testing we have documented a 4% increase in horsepower and as well anti-detonation properties from these coating alone and a total of 8% gains over competitor shelf units.

Here is an example of a Bisimoto Spec. high compression race piston design.



- Julio A.

North Coast Cab

This is a personal preferrence issue and you will get "do this, do that" from several different people.
To add to the mix....you can have the bores nikasil plated by US Chrome or someone similar for around $1k too.
To me it depends what you are trying to make of the car, how long you will keep it, how hard it will be driven etc....

I personally would hone and install aftermarket pistons.

Eric_Oz_S2

I'm curious as to whay caused you cylinder cracking. I would have though that only mechanical impact such as a broken rod could cause this to occur or perhaps severe overheating.

944meister

The coating on the piston wore off and was evident that it was happening on the others as well. my guess is that the piston started to slap and with the coating worn off it created more friction, which gualled up the surfaces, so it could have just been heat created by the friction that caused the crack. It was a hairline crack at the bottom section of the cylinder, below the water jacket.

murrayg

I've got the blocked stripped and cleaned up. No sign of cracks in the bores. Other than the trashed cylinders / pistons, the rest of the motor is in great shape. Bearings dated 12-88 and not overly worn or dirty. Crank, heads and cams are perfect. Something drastic happened to this engine to destroy the bores like this. Still unsure how to proceed, lots of advice for all options!

Gord.

944meister

if you haven't already, the covers that plug the empty space around the cylinders on the bottom side of the block, have bolts that need to be heated up to unfasten. locktight has been used on them from factory. if you dont, you risk snapping off the bolt heads, ask me how i know . depending which way you go, you might not need to touch them.

Jfrahm

S2 and 968 motors run pistons with very short skirts, they are easy to scuff with some detonation. Maybe the motor was overheated or run hard on bad gas or something.