Hey guys, I'm building a Predator 212 for a minibike. I'm going to be running 14cc heads, flat top piston with .020" lower compression height, and a billet rod that's .020" longer to account for the lowered compression height. I plan on running 1.3:1 ratio rocker arms and I was wondering what the maximum safe cam lift would be? Thanks in advance for your help guys :thumbsup:
Predator 212 valvetrain question.
- Thread starter dansybrant
- Start date
- Tags compression honda clone lift predator valvetrain
Without knowing what cam you are using there is no way to tell. Longer duration cams have more overlap (depending on LSA) which keep the valves open more at TDC. You need to check Valve to piston clearance when building up your engine. Safe minimum is .080 on exhaust and .060 on intake. Also for good squish you want piston to head (squish area) clearance around .030.
For the cost of the rockers and uppgraded parts you could buy a modest cam and get something that's easier on your valves and runs better.
Its been spoken about to death, but I will repeat this.
The Isky Momba Jr is probably one of the best cams of its type.
More lift and duration and it preserves torque while adding top end.
Tim Isky did all beginners a great favour by making this entry level cam that has no compromises.
It was designed for minibike builds.
If I had the choice and I was you I would use a real Honda GX160 18cc head ( for one things the valve train is stronger than clone )
14cc head:
That's a lot of compression, what do you plan to use for fuel.
91 Octane will probably give you trouble and I reserve judgment on 93.... ( if your tolerances are right that will be in excess of 12:1 )
With a stock cam I would expect it to detonate even at 93.
Its been spoken about to death, but I will repeat this.
The Isky Momba Jr is probably one of the best cams of its type.
More lift and duration and it preserves torque while adding top end.
Tim Isky did all beginners a great favour by making this entry level cam that has no compromises.
It was designed for minibike builds.
If I had the choice and I was you I would use a real Honda GX160 18cc head ( for one things the valve train is stronger than clone )
14cc head:
That's a lot of compression, what do you plan to use for fuel.
91 Octane will probably give you trouble and I reserve judgment on 93.... ( if your tolerances are right that will be in excess of 12:1 )
With a stock cam I would expect it to detonate even at 93.
Good advice from NOS. That cam will not have any interference issues. If you already have the 14cc head you could use a .045 predator head gasket to lower the compression.
Here is one on ebay
Cylinder Head Gasket Fits Predator 212cc 4000W 69728 Generator MPN 1 | eBay
your piston to head clearance will be kind of big (I don't know how far your piston will be below the deck but if it is a non hemi it will be around .030 + the .045 head gasket. will be around .075 not much benefit from squish area.
I
Here is one on ebay
Cylinder Head Gasket Fits Predator 212cc 4000W 69728 Generator MPN 1 | eBay
your piston to head clearance will be kind of big (I don't know how far your piston will be below the deck but if it is a non hemi it will be around .030 + the .045 head gasket. will be around .075 not much benefit from squish area.
I
I agree.
And that open head space now is more sensitive to timing troubles.
The reason you go with a 14cc is to get that quench and tight chamber, even the 18 is as good if its got a decent quench.
But once you open it up with thick gaskets to relieve the detonation and pre iginition issues it looses that great mixing and you need more top end timing.
With the extra top end timing you get into loss of torque at lower RPM.
And that open head space now is more sensitive to timing troubles.
The reason you go with a 14cc is to get that quench and tight chamber, even the 18 is as good if its got a decent quench.
But once you open it up with thick gaskets to relieve the detonation and pre iginition issues it looses that great mixing and you need more top end timing.
With the extra top end timing you get into loss of torque at lower RPM.
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