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Wed Jul 27, 2011 1:43 pm

My sand rail's engine is 40 years old and has never been rebuilt. I plan on rebuilding it soon and was wondering if it would be worth my time to use a 74mm crank instead of a 69mm. Reasoning for a 74mm crank, its not a huge amount of gain, i don't have to do any clearancing on the case, and its costs just as much as a new 69mm crank (cb performance). I understand ill have to put more spacers between the head and the cylinder. But, if i have more spacer will i have to get longer push rods? And, Will there be a very big difference at all. Will i be able to feel the difference? I understand its only a 5mm stroke gain.

thanks, Colton

Wed Jul 27, 2011 1:57 pm

More than likely you will have to do some case clearancing even with a 74mm crank. Inside case webbing has changed over the years so sometime even using a stock 69mm crank needs the case clearance.
You will have do some clearancing on the pistons to clear the crank and rod when it at the bottom of it stroke.
Depending on camshaft you may have to clearance center bearing surface and thrust surface of camshaft.
You will notice a difference in power. There will be more torque.
With so much available now then in the early years going to a 78 or 82mm stroke can cost you less in time and labor then it use to be.
What cylinder heads do you plan on using?

Wed Jul 27, 2011 2:06 pm

all your answers are probably in these old threads

http://www.thesamba.com/vw/forum/search.php?search..._chars=200

Wed Jul 27, 2011 2:41 pm

yep, I still had machining and some hand clearance work to make mine fit. Go 78-82 and call it good.

Wed Jul 27, 2011 3:29 pm

I just did one going from 69mm to 74, noticed a big difference in the low and mid rpm's.

the only thing that needed clearanced for me was the piston skirts because I went with the shorter 5.325 race rods. it ended up being easy, even though I was scared. but it turned out fine and runs great. http://www.thesamba.com/vw/forum/viewtopic.php?t=472324&highlight=clearanced+piston

my case was clearanced for a counterweighted crank in the past though.

Wed Jul 27, 2011 3:31 pm

if you go with a bigger bore the 74/76 and 5.325" rods works great. If you use 85.5s the skirts need extensive clearancing, which can be a pain.

Thu Jul 28, 2011 5:34 am

http://www.thesamba.com/vw/classifieds/detail.php?id=1053124
These might be of some help.

Mon Aug 01, 2011 6:38 pm

[email protected] wrote: if you go with a bigger bore the 74/76 and 5.325" rods works great. If you use 85.5s the skirts need extensive clearancing, which can be a pain.

Will the skirts on 94's need clearancing with a 74 mm crankshaft?

Mon Aug 01, 2011 6:56 pm

i think he said. if u go with a bigger bore.. its fine

Mon Aug 01, 2011 7:03 pm

oops.....so he did....gotta polish up on my reading skills :P

Mon Aug 01, 2011 7:21 pm

reading skills comes later..

just do a build thread now will you :)

wonder wat u finally decided on !

:D

Mon Aug 01, 2011 7:45 pm

ralf wrote: reading skills comes later..

wonder wat u finally decided on !

Come on Ralphee, read!! :lol:

From the Non-stroker motors thread:
I've learned that quite a bit of what I hear on this forum is not worth the time it took to read.....STROKER....gotta build a STROKER.....Lol! .....whatever......1915cc is the way I'm going and I'll be paying special attention to matching everything up with my combo....that's right....it's in the combo..........1915cc....ported 40x35 heads with dual springs....match ported manifolds with Weber 44's...Engle 120 with 1.25 rockers...chromoly pushrods.....balanced rotating assembly and pistons......1 and a half inch merged header with single phat boy muffler to keep good back pressure for the bottom end....Bosch 019 distributor and yes it will have an electronic ignition conversion..(points and condenser will be in the glove box just in case) 12.lb flywheel balanced with the crank and a Kennedy sage 1 pressure plate with stock disc to keep it smooth and not harsh....

Mon Aug 01, 2011 8:38 pm

ralpheeee ? wrong spelling darthy beibery hahaha

:) yes saw that thread

but also he wonders of a 74 stroke a 78 an 82 i think and alot :)

saw ur sad face on the 1807 build bfor.. i guess i should do that LOL to make u smile? hahahaha

Tue Aug 02, 2011 2:32 am

ralf wrote: ralpheeee ? wrong spelling darthy beibery hahaha

:) yes saw that thread

but also he wonders of a 74 stroke a 78 an 82 i think and alot :)

saw ur sad face on the 1807 build bfor.. i guess i should do that LOL to make u smile? hahahaha

yes......I'm guilty of waffling........think I should have bought motor parts first instead of the beam, wiring harness, body work...blah blah blah.....too many choices for the motor.....cash for moor partrs will be availale next week so we'll see...gonna be a crap shoot...

Tue Aug 02, 2011 2:35 am

justreally like the old school stuff.......not set in stones but it's probably oing to be a 2054 cc motor......if I remember correcty the 74 crank was one of the first "stroked" hi po motors...reground stock stroke crank....give me about 100 grand and I'll build one of each

Tue Aug 02, 2011 2:03 pm

If you use the Mahle FORGED 85.5 pistons you do not need to clearance the skirt. Any big bore Mahle (90.5, 92, 94) already have the short skirt design.

I love my mini stroker but would put 90.5s if I were to do it again.

Tue Aug 02, 2011 2:26 pm

derluftwagen wrote: If you use the Mahle FORGED 85.5 pistons you do not need to clearance the skirt. Any big bore Mahle (90.5, 92, 94) already have the short skirt design.

I love my mini stroker but would put 90.5s if I were to do it again.

And what about the AA pistons?

Tue Aug 02, 2011 3:13 pm

as stated by derluft ,

the forged 85.5s have shorter skirts = clearancing not needed

which was already answered by a dashing fellow by the name of John Connoly

90.5s up has shorter skirts, and the B stroke pistons are even shorter..

but the problem with the cast 85.5mm isnt the skirt being long.. its the bore being small so it hits the cheeks of the crank

ever wonder why90.5 A pistons dont hit the crank like a small bore?

the dashing fellow by the name of john connoly also did answer this a few postststs back

HTH

Tue Aug 02, 2011 6:22 pm

ralf wrote: as stated by derluft ,

the forged 85.5s have shorter skirts = clearancing not needed

which was already answered by a dashing fellow by the name of John Connoly

90.5s up has shorter skirts, and the B stroke pistons are even shorter..

but the problem with the cast 85.5mm isnt the skirt being long.. its the bore being small so it hits the cheeks of the crank

ever wonder why90.5 A pistons dont hit the crank like a small bore?

the dashing fellow by the name of john connoly also did answer this a few postststs back

HTH

So.....74 x 94 2054cc won't have piston clearancing problems?......I think that's what I got out of it....soryy, but I'm quite ignorant when it comes to anything other than stock 69mm stroke motors......
which motor, in your opinion, would be easier to build? 74 x94 or 78 x 94 or 82 x 94?

Tue Aug 02, 2011 6:25 pm

74x94 on B pin height

use 5.5 rods

and ud have about 0.060" deck.. u can turn the barrels on a lathe
to get ur desired deck.. or turn the barrels enough that it would let u use a 0.040" copper headgasket

call it a day..

74x90.5 works too..

ofcourse like most would say. it would make sense to run
78.4-82 strokes its easier..

example

78.4 stroke and using 5.5 rods on B pin height pistons,
ud need maybe 0.050" to 0.060" shims to get to ideal deckheight
so getting a set of copperhead gaskets of that thickness.. would let u have ur deck nice..

ofcourse mocking it up will have the final say on where ur stuff fals.. as far as deckheights go