69mm stroker crank in predator 420

[slonomo]

Originally Posted by KRAZYMATT

I put a torque cam in my 469 when I built it so I do have a stock/oem 460 cam I could install while I’m in there. Will the stock 420 rod hold up with the 460 cam in there? Motor govenor is still instant and valve train has been beef up a little bit. Also when swapping the cranks is there clearancing required to the balance shaft?

It'll hold up as long as it's not over revved. It's the rpm that kills those rods and pushrods.

[raydhd]

My early (2014) VC came with a stock clone camshaft. I seen some of the late DIY kits listed the torque cam as an option. But at others times the torque cam was part of the engine. The cams are stamped on the drive gear so it is easy to tell what you have.

[sho305]

I thought all VC460 had the cheater cam. A cheater cam is same lift as stock because its made from the same casting that only has room for that much lift. But they grind it with a lot more duration so the lobe is much fatter but same height. This also makes it as easy on the valvetrain because there is no added lift though your rpm may go higher you still have to beef it up. In my 420 it may have lost a little power down low at 2K rpm but at 2500 and up it gained. However it will rev right up to 6K if you want tho depending on mods you have on it. Over 5K the stock rod will not last long, it is always recommended you put a billet rod in with any cam in the clone or honda engines. I ran 5100 with my stock cam but that was only a few speed runs over the years I ran it, I never went that fast on trails in normal use.

Here is the VC cheater cam and the stock lifan 420 cam, check the lobe shape. Of course with 1.3 ratio rockers you end up with about the same lift as a performance cam.

[KRAZYMATT]

Originally Posted by raydhd

IMHO While you are in there get rid of another weak point the stock rod.

Well I should of listened. Finally got the ds back together I had been waiting on Vegas carts motor mount to be back instock to put it back together using that because I love their adjustability but I also wanted to get this cart back together and out of the garage so I went ahead and put it back together. Took it for a spin last night. Ran excellent tons of torque with the 97 rear end. Had the govenor still hooked up after about 30 minutes or so of driving it I started returning towards the house, it seemed to be loosing power on my quickly then right in front of my house about 50ft from the garage it let loose! Huge hole in the block smoke everywhere. I thought would of been louder- at first I thought I smoked the belt and it was the rubber melting. The slapping noise I heard turned out to be the crank shaft lobes slapping the govenor arm. Parked the cart probably won’t mess with it for another month or so. Block crank and rod so far are bad won’t know until I get into it but I think the starter, carb, clutch, flywheel, and roller rockers r gonna be about the only salavageable stuff on it. Oh well.

[KRAZYMATT]

[Shepard]

What did you have happen????????????????

[KRAZYMATT]

Originally Posted by Shepard

What did you have happen????????????????

Rod came apart

[raydhd]

Modded engine + stock rod = Bad news

[slonomo]

Stock rod has no bearing. Over revving wears the journal into an egg shaped pattern. Slap occurs. Rod fails. Seen it many times.

My original VC460 build was assembly lubed, broken in properly, zinc and phosphorus additives, never over revved. It developed a knock after just 20 hours of run time. Took it apart and the stock rod journal was out of round. My theory is that it was not perfect out of the factory, but I would never be able to prove that. I also think the metal used was some weird kind of pot metal alloy crap lol . ARC rod fixed that issue.

Judging by the color of that rod, it must have gotten pretty hot.

[Low-Tec]

Put in a skylight? Niiiice!