TheSamba.com :: View topic - 74mm crank and 94mm P&C

Sun Nov 02, 2008 12:51 pm

I was planning on building a 1914 - 94mm p&c with a stock 69mm crank and an Engle 110 cam. Heads with 44/35.5 valves, and dual icts or kads. If I go with a 74mm crank, will the case need clearancing and can I use the same p&c and stock rods? Also I am going 36 doghouse fan shroud.

Sun Nov 02, 2008 1:07 pm

74 should not have any issues with clearance

Sun Nov 02, 2008 1:25 pm

That is an odd engine that you are building. Are you certain that you have the correct intake valve size. I would never build that with the stock crankshaft. Nothing wrong with 69mm, but for sure it should be counterweighted. That engine will not play nice with the stock exhaust and heater boxes.

Sun Nov 02, 2008 2:00 pm

TWD wrote: That is an odd engine that you are building. Are you certain that you have the correct intake valve size. I would never build that with the stock crankshaft. Nothing wrong with 69mm, but for sure it should be counterweighted. That engine will not play nice with the stock exhaust and heater boxes.

Why - I am going more for a reliable daily driver. Good breathing on the heads.

Sun Nov 02, 2008 2:05 pm

The crank should be a drop in. I just did the exact same thing. I used a 74mm cb crank with CB Unitech rods. Absolutely no clearancing required.

You should be able to get to a good compression ratio with .060 shims or head gaskets. I used .060 to get .040 deck height which yeilded a 9.4:1 compression ratio.

I built my engine with a 120 cam, 1.25:1 rockers, am running 42 x 37 hand ported heads (VW castings) with 40DRLA's. The engine runs very strong with great low end grunt. It doesn't feel that far off of my 2332.

The engine had been built with a Melling 30mm cast iron oil pump. This caused the engine oil to overheat and fried the bearings. I replaced it with a 26mm Shadek. The engine now runs cool as a cucumber with good oil pressure.

Sun Nov 02, 2008 2:20 pm

Jeff Pyzyk wrote: The crank should be a drop in. I just did the exact same thing. I used a 74mm cb crank with CB Unitech rods. Absolutely no clearancing required.

You should be able to get to a good compression ratio with .060 shims or head gaskets. I used .060 to get .040 deck height which yeilded a 9.4:1 compression ratio.

I built my engine with a 120 cam, 1.25:1 rockers, am running 42 x 37 hand ported heads (VW castings) with 40DRLA's. The engine runs very strong with great low end grunt. It doesn't feel that far off of my 2332.

The engine had been built with a Melling 30mm cast iron oil pump. This caused the engine oil to overheat and fried the bearings. I replaced it with a 26mm Shadek. The engine now runs cool as a cucumber with good oil pressure.

So stock rods and 94mm P&C should work fine!!

Sun Nov 02, 2008 5:45 pm

I think the CB rods are clearanced. So, you may have to do some grinder work on stock rods. This involves grinding around the radius of the big end, in particular at the heads of the rod bolts.

You need to balance them after grinding.

Mon Nov 03, 2008 12:06 pm

Stock size uni rods and the 94 a pistons will work,i'm building the same only i use different rods but stock length :evil:

Sat Jun 04, 2011 5:39 am

I wanna get this straight... If you were to use a 69mm or 74mm stroke crank, you can use STD 94mm P/C's with either crank?

Sat Jun 04, 2011 6:51 am

I built a 74x94 2054 with the $90 CB unitechs, "A" pistons, and didn't have to do any clearancing.

Mine had a 110, 40mm kads w/ svda, ported stock valve heads, and a 1 3/8" hideout header, w/ stock heater boxes.

It ran amazing, had a ton of power, and was pretty easy to build. It did run out of steam at about 5500, but pulled hard and got 29mpg the day i sold the car.

If I were to do another 2054, I would do a 120 or FK8, CB los panchitos, or Tims stage 1 40 x35 heads, 44 IDF's, and a good header. It would make more power for not much more $ and still be easy to build.

Brian

Sat Jun 04, 2011 7:39 am

Jeff Pyzyk wrote: I think the CB rods are clearanced. So, you may have to do some grinder work on stock rods. This involves grinding around the radius of the big end, in particular at the heads of the rod bolts.

You need to balance them after grinding.

Gene Berg claimed that making the big ends of stock rods any thinner than about.310"-.320" thick was when they would fail. And with some of the failures that happened with other people's clearanced rods, he was calling it right. You will have to do some case clearancing with a 74mm crank and stock rods (and maybe notching the bottoms of the barrels just a little bit), but you're nowhere near compromising the strength of the case. And don't go crazy on the rod bolts. The CB rods have a great, compact design and for the price can't be beat.

Sat Jun 04, 2011 2:19 pm

Will you have to use .200" thick cylinder spacers with "A" pistons to compensate for the 5mm stroke?

Casey

Sat Jun 04, 2011 3:04 pm

Half the stroke increase (74-69=5mm.) 2 1/2mm= .100" (approx)

Sat Jun 04, 2011 3:52 pm

I build lots of 74x94-A engines. If you use stock rods you will have to do extremely minor clearnace work on the case. So minor it could be done with sand paper. DO NOT CLEARANCE THE STOCK RODS, clearance the case, that is just nuts. The CB unitech rods will eliminate any clearancing.

The spacer needed under the cylinders will vary by how the case is decked. The last one I build needed .090 under them for a .040 deck. I have had to use as little as .040 and as much as .120 to set the deck at .040. (all that I have built used either stock rods or unitech 5.4" rods.

I haven't bought a 69 stroke crank in years, the 74 is the same price and engines with it are as easy to build as stock stroke.

Sat Jun 04, 2011 4:07 pm

ALB
your right, had a little brain fart.

Casey

Sat Jun 04, 2011 5:07 pm

earthquake wrote: ALB
your right, had a little brain fart.

Casey

LOL! That's why we're all here; to help each other out.

Tue Jun 07, 2011 8:26 am

I'm kinda, sorta in the middle of the same "build" and am relieved to hear that the clearancing is so minor! I haven't order the shims yet, but I guess that a set of .060s ought to get me there.

I have the Kads, 120 cam, heads, and smaller oil pump as well. Header will be whatever one is necessary, haven't picked one up yet.

I was wondering why the larger pump would yield so much more heat and if a remote oil cooler would help with this? I was also wondering if anyone had a super rough estimate of what the horse power might be on this size/configuration engine? At the flywheel or rear wheels, doesn't matter, I just want to figure the power to weight for the car that I'm building so that I can run up a comparison chart with the cars that I've driven.

Thanks ! !

TC

Tue Jun 07, 2011 11:07 am

I went a different route with the 74 crank and instead of the 94 A pistons went with stock sized 85.5 pistons but i had to clear the case a bit with the 74 crank and stock sized uni tech rods for it to turn smoothly.
It depends on how the case is i think and always mock up to see if it will fit.

Greets :twisted:

Tue Jun 07, 2011 11:35 am

With a 74mm crank and mag case, you will need at least a .100 shim jut to get "zero cylinder deck". Aluminum tall deck cases are another story.

Tue Jun 07, 2011 12:11 pm

not true!

http://vwparts.aircooled.net/5-325-H-Beam-Connecti...ournal.htm

http://vwparts.aircooled.net/4140-Forged-Chromoly-...kshaft.htm

Been doing this a long time!!! Using Porsche length rods saves you some work on the top end.

derluftwagen wrote: With a 74mm crank and mag case, you will need at least a .100 shim jut to get "zero cylinder deck". Aluminum tall deck cases are another story.