3.1 Short Stroke Build 66 X 100

[356RS]

Started on my 3.1 short stroke engine. I have been looking at all the parts for almost a year. This build will be based off a 930/02 early 3.0 Carrera case. Ollie's went through the case and Pauter modified the 2.0 crankshaft. Improved oiling mods and rod journals cut down to 1.99" for Clevite/Mahle rod bearings and lightweight Pauter rods.

[BURN-BROS]

Looking good Mark!

[jpnovak]

My dream motor! Love a 66mm crank. especially one with high rpm oiling mods.

Keep going Mark. I am watching with interest.

More details on the build please.

[Trackrash]

Are those rods titanium?

[rennzeit]

The crank is super tasty!
cheers,
dug

[jbell959]

Very nice Mark... that's going to be a great engine for the 72

[Henry Schmidt]

Beautiful start Mark
It looks like your plan is to spin that puppy so make the piston and pin package as light as possible. We chose a lightened JE FSR piston for our 3.1 spinner.

[356RS]

Rods are 4340 Chrome-moly weighing in at 523 grams. Pistons are from JE and are the later FSR design. Did some trading and ended up with a very good deal on a GT-3 oil pump. 930 pump would have been fine. I have to do a little grinding on the case to fit the GT-3 pump. Photo with toothpick shows what I had to remove.

[tocobill]

Nice build. I used R&R rods. Super lite and still forged 4340. Rods were 480g each for my 3.6 build. Who did your crank work? My first go around was this sort of build but never could find the turbo case so I went the 993 3.6 route. Good luck.

[0396]

Looks like a well thought out build.
Congrats and looking forward to seeing the future updates.

[Flieger]

Forgive me for the silly question, but how much smaller is the 1.99" bearing compared to stock? If I remember correctly the 70.4mm stroke crank got its extra stroke from making the rod bearings smaller and offset grinding them. We know the 70.4mm cranks had rigidity problems, so does making the rod bearings smaller on a 66mm crank reduce one of its inherent advantages?

[BURN-BROS]

Hi Max, journal diameter was reduced by about 6.2mm from the original 2.0 liter. It is 1.8 mm smaller than a 2.4. The journal width is still 22mm, not the 24 of the 2.4 crank. Which I believe is the problem with those particular cranks.

Does the journal diameter reduce the advantage? To some degree, yes. But we run 53 journals on 2.0 liter cranks with no harmonic issues that are quantifiable.

Reciprocating weight as well as counterweight mass are a real factor in where the harmonics will show up.

Originally Posted by Flieger

Forgive me for the silly question, but how much smaller is the 1.99" bearing compared to stock? If I remember correctly the 70.4mm stroke crank got its extra stroke from making the rod bearings smaller and offset grinding them. We know the 70.4mm cranks had rigidity problems, so does making the rod bearings smaller on a 66mm crank reduce one of its inherent advantages?

[Cairo94507]

Wow..... this is the deep end of the pool for sure. Beautiful parts and work.

[356RS]

Aaron gave a great answer to the journal question. The main reason I had the rod journals cut down was so I could use the Clevite/Mahle rod bearings. Very good bearings.

[KTL]

Nice Wilton vise Mark! I have the same one and it is a brute.

Brian & Co. at Pauter went to town on those counterweights! I had my crank knifed a bit by Marine and David only took a slight amount off. I see they also grooved #4 main and certainly must have cross drilled it. NICE.

Shuffle-pinned main supports on the case too!

I'm surprised you didn't choose to use a straight cut I-shaft gear set? Pauter makes a nice pair of gears.

[356RS]

Thanks Kevin. Yes I thought about the stright-cut gears but put that $ toward Pauter's rocker arms instead. Moving along, main bearing are Glyco std/std and coated with Calico's CT-1. Cranks ready, I.S. cleaned inside & out. Replaced I.S. gear and flipped timing chain gears. Checked oil pump drive shaft fore & aft play. Test fit I.S. and checked backlash. Checked crank rotation clearance. New chains installed, lubed all bearings and sealed everything up, case together and torqued down. The case had shuffle pins installed so the last 1/4" of closing up the case I needed to use the help of a rubber mallet. Worried thought's went thru my head about if any of the oil pump seals got moved around or misaligned while I was tapping the case together??

[KTL]

Those new Pauter rocker arms are the cat's a$$ They really turned out a beautiful product with those.

Thanks for sharing and don't fret over those pump seals.

[356RS]

Installed a set of Henry's studs. Was thinking about the 993TT studs which I have used before and think they are great, but for the price of Henry's kit with washers & nuts you can't beat it. Pistons are JE's newer 932P FSR with coated skirts and are in the 509g range. Piston rings all filed to correct gap. Setting up #1 & #4 for some deck height calculations.

[Henry Schmidt]

Beautiful werk Mark.....It's a pleasure to watch.

[KTL]

Mark,

What's the proposed comp. ratio & pins for those pistons, if you don't mind sharing?

Thanks,
Kevin