Fastest928

I have overbored over 50 blocks for 104mm bores and have never seen a block as thick as Sterlings 104mm overbore being thicker post boring than a stock S4 was preboring!!! With Porsche min/max tols per Reynolds it had to have been a block that was a defect (core shift) and got through QC.

Maybe Bud can comment with his experience boring and honing blocks for 104mm pistons?

slate blue

I have the parts for two engines, one is the full house effort with a billet crank the other was designed to be much cheaper and has a capacity of 327 CI or almost 5.4 litres. I have built a custom manifold for this engine, it has high flow heads, around 265 to 270 cfm at 0.500 lift which is what the cams go to. The pistons are custom and designed for the alusil block material with manufacturer's recommended clearances and rings. They are light also and you should use the S crank and have the offset that the factory pistons have. Comp will be around low 11s. Power should be in the 400 to 450 range, get lucky maybe a touch more.

Greg

terry gt

what is the minimum aceptable wall thickness for a 104.5 bore ? I have a 86 block that is already bored . At the top of the bore the cyl . measure min .230 inches to max .265 inches . is this ok?

danglerb

Some wall thickness info in these old threads.
https://rennlist.com/forums/928-foru...hift-data.html

https://rennlist.com/forums/928-foru...r-stroker.html

https://rennlist.com/forums/928-foru...-strokers.html

RKD in OKC

If you go Nikasil make sure you get the correct rings for Nikasil. Rings for stock Alusil will start chunking the Nikasil in 17K to 20K miles. Just ask just about any 911 racer shop. I learned this the hard way from a car I bought that I thought the Nikasil the previous owner had done was a good thing.

RicerSchnitzzle

Okay, I'm pretty stupid... Read the wrong side of the caliper. Need to replace the battery so I don't have to figure it out.

It was just shy of .4" Looked again and my bore ranges from 8.5 to 9mm measured at the top.

What's the easiest way to check bore spacing as this might be a decent block for boring. I still think I'm staying with a 6.0L and stock pistons, but who knows, I might find an extra $2K sitting around for block work.

Vilhuer

That sounds much better.

If you have two blocks which have 8.5mm+ walls I might be able to help make decision easier by buying one. Using any 100mm stock pistons together with stroker crank is problematic as there isn't room for full piston skirt in block when stroke is longer than stock.

9x8

6.0 with stock pistons won't work indeed, but it might be possible to go with 944 ones from what I heard.

Lizard928

Erkka,

Both of my 86 blocks have 8mm cylinders. From what I have been told the S4s are 7mm.

One is being used, the other does ned a rebore but is otherwise good........

kccampro

Yet another post that's beyond my knowledge... I have two Euro S motors (M28/11 & M28/12) and a complete S4 motor. Which option in this thread is the cheapest if you want to replace the pistons as part of a rebuild? I just want a stong running motor for the DE project that I can beat on a few times a year, for many years, without spending stroker money. Are 944 pistons cheaper? I'm lost... back to searching the threads...

danglerb

Sell the S4, buy a MUCH cheaper 85/86 short block, and build a straight up normal Euro hybrid (Euro top, US bottom) its a solid known performer and should be plenty for DE.

What year is your chassis? Anything CIS would make an easy drop in.

kccampro

I have 4 motors at the moment... two Euro S 4.7L (M28/11 and M28/12), a running S4 motor and a running US '83 4.7L

I need to decide what my best option is and then freshen up that engine. The chassis is a '80 Euro with a full chrome molly cage, coil overs, LSD and S4 brakes. I need to figure out which engine to use and just go with it... otherwise this thing will never make it to the track. Definately using the CIS set-up. Also, want to send the Euro S heads to 928 Motorsports for the porting and polishing since what I have in mind is just a good breathing, good compression strong running NA motor.

Bill

danglerb

80 Euro is CIS, and so are both of the Euro S motors you have. Either one, pick the best etc. should drop right in and provide plenty of go power in a track car.

The S4 and US 83 would be a wiring nightmare to put in your car, neither have spare parts that would useful either, so I would sell them to somebody that can use them.

I don't think porting and polishing a stock Euro S head has any real benefit, the cam is the limiting factor on the breathing combined with the intake system.

If I took the heads off of a Euro S motor for any reason, they would not be going back on anything but a US 85/86 shortblock. Too much bang for the buck to ignore, at least a 10% increase in HP and torque.

For a track car, and if my state wasn't smog bonkers, I might get a set of long tube headers, but at the minimum 85/86 exhaust manifolds and a Y or X merge pipe.

kccampro

Ok... now we're gtting somewhere. I think I'm starting to understand. I thought a 'hybrid' meant 16v heads on a 5.0L block, but it sounds like not all 5.0L blocks are the same. What's unique about the '85/'86 block that makes more power than my '88 S4 block? Thanks for the info danglerb.

terry gt

Danglerb , thanks for the links , has anyone tryed reinforcing the cyl walls using devcon 3874 ? Filling the water jacket with sugar or salt ( it disolves) and filling the top 1/2 inch with epoxy , then drilling it for water pasages ? to create a reinforcing ring ?