blown 944

I don't have a 3.0 block in my possession ATM. I would like to know the OD of the cylinders and cylinder wall thickness.

TIA

Dougs951S

I smell something awesome coming..

Tom M'Guinn

I have a 104mm block bored to 105.25. The cylinder walls are now about 7.8mm thick, so figure about 120.85mm OD (105.25+7.8+7.8) or maybe an even 121 with better calipers? If you add back the 1.25mm taken out of the bore, that would make the original thickness at about 7.8 + (1.25/2) = 8.425mm +/- caliper error...

blown 944

Thanks Tom.

I'm doing some calculating regarding the largest "safe" bore I can go with the sleeves we are using.

I believe I may have found another off the shelf piston for a "BIG bore" 3.2L using my current crank and rods.

I'm not sure whether I'll do it this round because I currently have 105.5mm pistons in my possession that I can use with a sleeved 2.5 block.

What I need is a junk 3.0 block and info on what I need to use my 2.5 S head.

So far all my experience is with 2.5 stuff. However, since I'm doing a new block, I might just go for it if doable.

Paulyy

Just for thoughts, the larger we go with displacement wouldn't you be more limited on how much you can rev?
So if you do a large 3.2+L engine, using an 8v head would be more beneficial then a 16v head for drag racing as you'll get your torque sooner? As where a 16v head would be good for 600hp at high rpm?

Tom M'Guinn

The connected cylinders and raised floor webbing all cast together make for a nice base to build on -- just say'n...

blown 944

No not really, the larger bore should actually be even better for high rpms, due to the un shrouding of the valves. Along with the possibility of even larger valves.

The pistons are still very light.
Retaining my current stroke, I'm very confident that 7000 rpms are safe. looking at my bearings after all the abuse I threw at this engine lady year is my rational.

I have a couple of ideas regarding being able to retain my low end torque. One being a split profile intake cam, the other being dual adjustable cam gears.

Either way ie; even if I don't do anything with the cams, the added displacement should get the turbo going even sooner=torque.

Plus, TBH, it had too much of a torque spike as it was.

blown 944

I know. Sounds like the foundation I NEED for my goals..

However, I believe we have a pretty solid solution coming very soon regarding 2.5l block strength. Part of me wants to prove that out before moving on to the 3.0 block.

Dougs951S

Folks have taken the 3.0 blocks, and the 5.4 928 blocks out to 110 mm bore, but that is pretty much removing the entire stock bore and replacing it with a sleeve. The big bore 3.35 liter is very much like the 2.8 liter big bore based off the 2.5 liter block. The latter doesn't seem to last long term, although I tend to think build design and the architecture of the 3.0 block would lend strength not obtainable with the 2.5. The ~108.5 bore you are looking for I think would be very doable with sleeves and would be no more stressful to the block than say, a 2.5 sleeved and bored to 104.

Paulyy

You'll be able to get cams that'll give you a power-band from 3500 rpm to 7500 rpm with out a split profile cam. The 8v camshaft in my motor now is capable of power from ~3500 to ~7300 with a rpm limit of 7500. Should be able to easily actieve over 500 rwhp from 23psi but my bottom end isn't capable of that as it's standard.

333pg333

Just a completely different concept. Has anyone looked at the 2L Iron closed deck 924 block for sleeving while retaining a lot of integral strength?

Anyway, looking forward to whatever the next phase of your project is Sid. Always makes great reading from down here!

RajDatta

You mean like the Supra 3.0 or the Audi 1.8-2.0 turbo engines?

blown 944

I don't know much about the 2.0, but from what I've seen it looks completely different.

My new engine will be closed deck for sure. Hoping to have it built in a couple months.

I'm still a little angry that the valve seat broke in my 2.8. That engine was just getting started. I'll be more cautious with decking the head so far from now on. I believe that was the cause.

michaelmount123

You have to alter the coolant bypass at the front of the head to keep the thermostat functional. It's a pretty easy mod; we've done it numerous times. Section in a hunk of aluminum, weld it up, then drill to connect the new water passage to the old one. Surface the head and you're done.

Compare the two head gaskets and you'll see exactly what's needed.

Oh, you also need to use 2.7L head studs (with the revised 2.7 torque).

MM

refresh951

Sid,

Be interesting to look at cylinder stabilization/stiffness given different sleeve thicknesses. Seems that the more iron the stiffer the cylinders will be up to a certain point. Not sure how thin the aluminum bores can get and how thick of a sleeve is available but it would be good to look at it in some depth.