mtnman82

Up front, I won't have the time to really do anything with this until next summer, but in the meantime would like to develop a plan and maybe get some parts worked. That is - if it is even worth it...

I picked up a sleeved short block from a reputable engine builder here in S. California. I came by the block because the owner had another build just about ready to go and needed some funds so decided just to install that and sell this one. With this block, he was flagged for excessive smoke and had started burning oil profusely after running the sleeved engine for several weekends. Iron sleeves, and a big name sponsor on this forum told him to use the stock pistons/rods/rings. Engine builder said he questioned this but was assured all would be fine. Engine builder also said rings wore down which is why it started to burn oil.

Originally I wanted to do a 2.85l hybrid stroker build (would still like to). But now I have this sleeved block. The best I can measure the bores to (at the top anyway) is 99.720mm and the sleeve thickness appears to be 1.7mm. I was hoping the sleeves would be thicker and I could bore them out to accept ~101.6mm (4.000") pistons. I'm guessing this is not going to work with the 1.7mm sleeves?

So in that case, I'd be contemplating ~standard size pistons with rods and crank set up for the offset grind, assuming there's something available. Using the same stroke/rod lengths as the 2.85l works out to 2.7l (?). Opinions on if it would be worth it? Is this a good place to start (i.e. am I really ahead of the game)? Or is there really nothing readily available? Should I just sell this setup, get a cheap scored block and start from scratch?

I would imagine others have the same parts in their collection and are pondering the same? Hera are a couple of crappy phone pics of what I have - I can try to post some better ones if someone wants a better look at something.

FWIW, I see several distinct regions in the bores - at the very bottom appears to be a lip of original material that the sleeves sit on, the bottom of the sleeve appears untouched, original cross-hatching, a few mm's of 'light' ring wear, the majority of the stroke with ring wear, another few mm's of lighter ring wear, then another few mm's to the very top where there are carbon deposits.

refresh951

Yes

V2Rocket

I've found myself in a similar spot.
I have a sleeved block that I'm not sure if I want to proceed with. It was a 4.00" steel bore but needs to be taken to 4.020" to be usable again.

I was intending to do a hybrid stroker and have a crank needing work that should work out to 2800cc give or take a few.

But I think I'd be happy with a regular 2.7na or 2.5 turbo.

With regards to your engine, wouldn't there be galling issues running the Porsche iron coated pistons in an iron bore, like running an aluminum piston in alusil?

refresh951

These block are the foundation of your motor. Consider what it will take to complete. Do you know who did the sleeves? Do you know for a fact it was done right? Imagine you design your whole build around a bore you do not even like and then you drop a sleeve. It is not much more to get a block from Lart and have the sleeves done right and the way you want.

mtnman82

Yep, I know you are in a similar situation Spencer. Have no idea regarding the galling - I would have thought the same. I'll take some pics of the pistons/rings and post. So you're not sure about even going the additional 0.51mm? How thick are the sleeves?

I'm trying to get more information on the block Shawn. I hear you on this being the foundation. But it was a good deal, I have it in hand, and have limited resources here. I do know it was run for quite a few weekends so I feel 'better' about the sleeves being settled in/not dropping and a good job done. It also sounds like the owner and builder have been in the 944 game for a while and I believe they would take it to someone with experience. On the other hand, it does not appear the block was skimmed after the sleeves were installed (but that can be done locally). And the stock pistons/rings were used. I think you know where I'm coming from - trying to be as cost effective as possible...

So am I hearing a loud and clear: sleeve really can't be bored out any?

If the block does have a solid pedigree, would it be worth it to do a ~2.7l?

PaulD_944S2

Your options are:

1. Bore the sleeved block to the next oversize and build the engine as you see fit;
2. Remove the sleeves and have the block machine for new sleeves to go to the displacement you want;
3. Buy a different block and build it, sell your current block;
4. Buy an S, S2, or 968 block for 2.8 or 3.0L displacement and run Alusil or iron sleeves, depending on the block's condition.

None of the options are going to be cheap, but you can price out the parts and see which way is cost/benefit best for what you want to achieve.

Dave W.

Is your bore measurement accurate? I think I have a plan.
Get a set of Subaru STi pistons, Wiseco offers a set with 99.75mm bore. If your measurement is good you just need to hone the block .03mm larger for proper piston-to-wall clearance.
STi pistons have a compression height (piston pin height) of 1.181" so if you use a 3.0 crank and have it offset ground to 93mm stroke, and use typical Eagle 6 bolt rods the deck height works out to be very close. This is not the full stroke offset grind, if you can find pistons that are 2mm shorter that the STi then you can get the maximum offset grind of 95mm.

Wiseco #K600M9975
these pistons have a dish of -18cc, so the comp ratio will be around 9.2 depending on final dimensions and headgasket thickness.
displacement is 2905cc.
Please check my math before committing to a purchase!

V2Rocket

the sleeves are plenty thick for overbore. i could probably take this block to 4.030 or 4.040 if i wanted and still have enough steel left.

its more an issue of cost - will the low-end gains, which i certainly would like to feel, be worth the many $$$ outlay to build the engine, to me?

part of the appeal for me of getting a bigger engine was to have more torque available at low rpm since my car is a street car exclusively and daily driver. but a few weeks ago i bought another car to use as the daily with an automatic so that argument has kind of lost its value.

mtnman82

How thick are your sleeves Spencer? Are they thicker than mine (1.7mm)? I guess I should be asking - how much sleeve material needs to be left if I want to entertain boring out?

Dave I'll measure again tonight and try to get some pics of the pistons posted. If I can find a deal on a proper 3.0 crank I might go that way, but every time I look at those cranks they are major $$$. I would love to talk to you about getting the machine work done (especially turning the crank) if that'd be cool?

Still waiting to hear back from the original owner about the sleeve work. I'd be willing to bet it was done correctly at a reputable shop, knowing where it came from. But definitely want to find out what I can...

V2Rocket

eyeballing with calipers looks about 3/32" material left or about 2.4mm

the shop i am/was thinking of using (who got their start in mid-60s making hot cylinder heads for some guy named "Carrol") said that 1/16" is the minimum thickness of a sleeve. about 1.5mm.

on your block, doesnt the bore seem a little small? shouldnt the cylinder be ~100mm and the piston 99.xxx to fit?

mtnman82

Yes, the bore does seem small to me but I am thinking it's a me thing with the measuring. I'm wondering if there is a better technique or tool - I'm just sticking my digital caliper in the bore at the top and looking for the max dimension I can find by wiggling it around? I will measure the pistons too.

V2Rocket

dial bore gauge is more accurate but maybe pricey?
your shop should have one.

mtnman82

I definitely need to get a dial bore gauge.

Dave W.

Sure, I'll help where I can.

V2Rocket

running the math now..
1.181 piston + 150mm rod + 1/2(95mm stroke) = 227.5mm or 2.5mm (0.098") below the 944 deck height which sounds pretty good.


Summit's CR calc, with the above info entered and a 1mm gasket/56cc chamber...
Compression Ratio : 8.32 : 1
Total Displacement (in.3) : 181.47
Total Displacement cc's : 2974.92