Modded 212

Shadow99

Shadow99

New Member
#1
#1
I am working on a 212 for a dirt kart. Bought a new head with 32 lb dual springs and 3:1 roller rockers. I'm trying to figure out pushrod length. The cam being run is a 308. And the head is original height, no machining other than being ported.
 
sparkwizard

sparkwizard

#2
#2
Do you have the original pushrods? Try those and see if they just might be what you need. That is how I figure it out. I you can't set your lash, then measure how far off you are and add or subtract that number from the stock rod length.
With 32Lb springs and 3:1 rockers, I think you need some big fat pushrods.

Welcome to OldMiniBikes!
 
VeritableFox

VeritableFox

Active Member
#3
#3
Guess that depends on the rockers you got. DJ-2103 rockers from ARC require 5.160" rods, for instance. Running what will end up being a 404 lift with those ratio rockers I assume/hope you are not building a Hemi as that WILL coil bind without relief cuts and knock the stock piston regardless. Personally, I'd also look at getting into stainless or chrome moly push rods, switch to billet tappets and stainless valves because of the 32 lb springs and extra heat.

While I haven't gotten around to doing anything to my predator as I'm still researching and putting together a parts list, mine is a Hemi and I've run across the lift problems in my research.

And welcome to OldMiniBikes.
 
ole4

ole4

#4
#4
When you redo the valve train depending on if you have fixed fulcrum rockers which require geometry to be set on both the valve side and the pushrod side or adjustable fulcrum which only require geometry set by pushrod length, you should be calculating the correct pushrod length. With all the variations possible you cant just say use this one and it will work. Actually it will work but your geometry may be way off losing lift and wearing parts out prematurely.
 
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panchothedog

Well-Known Member
#5
#5
Gage, the company that makes the very best roller rockers, has a very informative video on how to determine correct pushrod length. Had you purchased from them, website would have been included. I'm pretty sure you can Google it.
 
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