Author Topic: 74 Mm Crank (Read 2915 times)

66split · « **on:** January 28, 2004, 12:49:37 PM »

my motor is crap and squeals. its a 1776. i need to split it. can i replace the 69 crank with a 74 w/o machining? anyone? where is darren when you need him?

James Buchan · « **Reply #1 on:** January 28, 2004, 01:01:58 PM »

I've heard people say yes and no to that question - If the answer is yes might as well drop in an 82!

Geoff · « **Reply #2 on:** January 28, 2004, 01:11:14 PM »

The 74 will go in with little or no clearancing. ( i have never seen one that needed to be clearanced) The 74 will use the same \"A\" type pistons as the 69 stroke after 76 mm you will need the \"B\" pistons.

Glenn · « **Reply #3 on:** January 28, 2004, 01:17:55 PM »

I have a 1904 (90.5 x 74) and mine needed no clearancing. But with any engine building... you should check before you close up the case.

And i'm using \"A\" pistons.

Stephan Schmidt · « **Reply #4 on:** January 28, 2004, 01:57:07 PM »

what is the difference between the A-B type pistons?

Stephan

Glenn · « **Reply #5 on:** January 28, 2004, 02:02:42 PM »

\"B\" Pistons have the wrist pin lowered and require longer cylinders. Otherwise you would raise the compression too much.

66split · « **Reply #6 on:** January 28, 2004, 05:18:32 PM »

you guys dont sell 74 s do you geoff?

66split · « **Reply #7 on:** January 29, 2004, 07:57:33 AM »

geoff?

Geoff · « **Reply #8 on:** January 29, 2004, 08:57:24 AM »

Hwy 66split,
Yes we do, we have a few to choose from. We have welded counterweight or we can order cast. The cast is weaker and i would not recomend it in a high HP motor that would see any track time but a low rpm torque motor it would be fine.
If you would like prices or more info send me a PM

mikeT · « **Reply #9 on:** January 29, 2004, 11:37:06 AM »

how much more power would adding a 74 crank give to a 1776cc, is it worth it? is it a whole lot more inexpensive then adding a bigger crank(78-82mm) and cylinders?machining the case expensive?

Cameron · « **Reply #10 on:** January 29, 2004, 12:59:14 PM »

Hey 66split!
There is no machine work involved in getting a 74mm crank into a stock case. Just some hand work, you will have to notch the case in a few places to clear rod bolts. You will also need some spacers under the cylinders, to make up for the extra stroke. You will not know exactly how much until a trial assembly is done. Should be around 0.100\", plus some shims for deck height. I would strongly advise that you spend the extra $, and get the welded crank. Think about balancing $ also. Think about new main and con rod bearings. And a new set of rods. Every time I've heard an engine squeal, it's been a spun rod bearing; something else to think about too. 82mm crank requires lots of clearancing, and different piston and cylinder kit. If you're willing to put out a little more $, you can go 2110cc.

The difference between A and B pistons is the pin height. B pistons have pin closer to the top of the piston.
Good luck!
Cameron

66split · « **Reply #11 on:** January 29, 2004, 01:29:15 PM »

i have heard yes and no as well. I have an aluminum case that I may build out later. For now I want to go turbo and I figure since I am rebuilding anyways, might as well get some more stroke out of it. go ahead and email/pm me a price geoff. i prefer cw, balanced. The only other place i know that has them is Demello.

Author Topic: 74 Mm Crank (Read 2915 times)

Stephan Schmidt