Confused by crankshaft choices

[gimmesomeshelter]

Hello-

I'm investigating the feasibility of installing a 912 crank into my 36hp engine case. I’ve been looking at my options, but I’m still not sure what’s the best course to take. Buying new (e.g. one of the billet cranks from Scat) would be the easiest, but also the most expensive route. New cranks seem to run between $1000 – 2000, but the web sites where I’ve seen them listed (NLA, Pelican) don’t list any information about the cranks. Used cranks are appealing from a price perspective, but I’m aware that a crank that looks good can still fail the magnaflux test. Are there certain cranks that offer exceptional value? Likewise, are the certain cranks I should stay away from?

Thanks,

Paul
_________________
"I would rather have questions that can't be answered than answers that can't be questioned."

Richard Feynman

[cassa]

What you are talking about here is total overkill both engineering wise and price wise. The only question to be asked is why?

Are 36hp vw cranks so hard to get over there in the states? I am sure you could find a 36hp engine and grab the crank out of it a lot cheaper than you could buy any 356/912 crank. Here in Australia, complete 36hp engines are not exactly common but are certainly more common and cheaper than any 356 crank and we got a lot less early vw's than you guys did.

I recon you should just find a complete 36hp engine and grab the crank out of it. What exactly are you trying to do anyhow?

Cheers

Michael

[gimmesomeshelter]

Hello-

I'm glad you asked. Over the past few years I've collected enough parts to build a virtually 100% NOS 36hp engine (case, crank, rods, cam, heads, etc.) During this same period I've been working on the suspension - making it safer and more fun to drive. For the longest time I thought a stock 36hp engine would keep me happy. Not any more! I know realize that I'm either going to have to have two engines (the stock engine and a more driveable one), or I could put the money into a single 'old speed' engine.

BTW, used 36hp are very easy to find in the US. There's even a shop in Los Angeles that will 'stroke' them for customers. Unfortunately, 36hp cranks frequently failed in stock engines, so I don't want to consider them for an 'old speed' engine.

The old speed engine would have the following attributes:

NOS 36hp case
356/912 crank and 912 rods
77mm stroker pistons
8 dowel flywheel modified to take 12volt clutch
Compression ~7.5 (from 6.6)
1378 cc (from 1196)
Ported 36hp heads with larger valves
Riechert linkage/manifolds
28PCI or 32PCBI carbs
40hp fan
Gerg 36hp sump
Gerg full flow filter

I realize that it would be much less expensive to just stick in a DP 1600, but this path would save space in the garage, and would be a lot more fun to show off.

Thanks,

Paul
_________________
"I would rather have questions that can't be answered than answers that can't be questioned."

Richard Feynman

[Shorrock]

Paul,

I am building up a similar oldspeed 36hp:

NOS Case "late"
80mm Shasta Design DuraBar Cylinders
80mm Shasta Design "JE" Pistons
Okrasa or Pre-A Heads
912 NOS Crank
Dual Pepco Superchargers or a Shorrock C142B Supercharger
Single 2" SU Carb

Here is the issue with fitment of the 912 crank. You will need to turn the crank down to fit the 36hp case or have the 36hp case modified to accept the 912 journals. The two center crank sadles on the 36hp case are 50mm where the two center 912 journals are 55mm. You should find a very special shop to do this work as there are a couple of other issues to make sure the 912 crank and 36hp case match up perfectly.

If I had to do it again I would hunt around until I found a good condition 912 crank and have it turned down to fit the 36hp case.

The best route would be to have the case modified but there are very few shops that can do this and if they mess up the NOS case is toast. Less risk turning the crank.

Read this link for further information on old speed racing 36hp engines:

http://www.thesamba.com/vw/forum/viewtopic.php?t=96565

Keep me posted on your build.

Howard

[mpribanic]

What are you putting the 36hp engine in?

Bus?Bug?Ghia?
_________________
Call your Cunado's:

https://vimeo.com/67661950

[gimmesomeshelter]

Hello-

'57 Oval. I want it to look as stock as possible, but be fun/safe to drive.

Thanks,

Paul
_________________
"I would rather have questions that can't be answered than answers that can't be questioned."

Richard Feynman

[OMT]

This Engine has a "B" 356 Crankshaft.
86mm pistons
912 Heads
MFG,
Al

[Shorrock]

[OMT]

Hallo Shorrock,
The "B" crankshaft has 50mm main bearing journals. Same as 36hp VW.
No "Special modifications" are needed to make this combo work.
When You go "Exotic"........Super 90; 912, where do You find Main Bearings?
Al

[gimmesomeshelter]

Al-

My understanding is that the C/912 were the most durable. How much of that durability is lost when using a 'B' crank, or by turning down a 'C' crank to 50mm?

Thanks,

Paul
_________________
"I would rather have questions that can't be answered than answers that can't be questioned."

Richard Feynman

[Jacks]

if you want to come by my shop in san clemente i will be happy to show you a large pile of broken/cracked 356 crankshafts including standard size as well as reground,S90,C SC/912,B,A crossdrilled, rewelded, hard chromed, oversize dowels, aftermarket etc. the reality is that these crankshafts are only made of metal and when subjected to the rigors of literally millions of revolutions over hundreds of thousands of miles, countless stresses of acceleration, deceleration, red line+ , not to mention unbalanced clutch/flywheel assy's and other components, improper clearances, bad align bore, too high compression, over advanced ign, and use of less than premium octane fuel, any crankshaft will fail. that being said, i have no trepidation installing a used, correctly reground, magnifluxed crank of any type in appropriate applications. hot rod 36hp? anything has to be an improvement to those weak crankshafts. back in the days when those motor were prevalent broken cranks were common experience.

[Shorrock]

[quote="OMT"]Hallo Shorrock,
When You go "Exotic"........Super 90; 912, where do You find Main Bearings?
Al

Hey Al, I just admire your work! 912 std std bearings are available locally. Walt can do the modifications to the 36hp case as well as Rimco. I like the thicker journals as well as the CW. My other thoughts are how far do you go with the case. I am thinking that modifications to put modern "late" lifters in would also be desirable. This I can do at my shop if I only had time. Your mods regarding through bolts on the centers is also of interest. My plans are to supercharge the engine so high rpm to make hp is not needed. Thanks, Howard

[Gunter356]

hello I read the replies to your post and they all make good sense.several years ago I had a porsche shop build me a warm sc/912 motor and he suggested we use a "c" model crank verses the 912 I asked why his response was the C crank was a better everyday crank it is lighter and spins -up faster he stated the 912 was beter for sustained high rpm(track work)I know this is just his opion he also stated he saw less problems with the C verses the 912 in terms of breakage.good luck with your motor project. PS I ran that motor for several years sold the car to my brother who drove the wheels off it never had a problem.

[towd]

if you guys might be interested,, I'am about to list on the Bay,, A Sp roller, coming out of a early B case. Not sure what the stroke is, but as I can find it's 74 or 75 mm.

The motor has been stored since early 70's only started a few times a year to keep it from rusting...

It was a sweet running motor ,, No one was interested on these sites,, I guess because of the stroked crank....LOL..

so it's part it out, I've already made the $$$'s in parts that I was asking for the whole motor,, and I haven't even really gotten to the long block yet or the 48's...

[gimmesomeshelter]

Hello-

I was at the machine shop this morning discussing my project with the owner when he forewarned me that even if I find an expensive used crank, I'm still going to have to spend close to $400 to have it reground and nitrided. He opined that many people skip the $250 nitriding step and live to regret it. Based upon his comments, those used cranks on eBay aren't a very good deal. Am I missing something?

Thanks,

Paul
_________________
"I would rather have questions that can't be answered than answers that can't be questioned."

Richard Feynman