330 or 370 ESR PV

[KRMit]

A buddy of mine is running an ESR 330 PV cylinder and recently killed it. The powervalve broke in half and slid down into the cylinder, rubbing grooves in the piston. He's going to send the cylinder back to ESR to either put a new powervalve in it or possibly talk to them about swapping it for the 370 cylinder.

My question is, what can he expect from a 370? Will he have to do further case porting? Will it run much hotter? What are the power characteristics in comparison with the 330?

Thanks!

[TheFontMaster]

The 370 will give you a more broad powerband, more low end than the 330, and overall more horespower. On the downside the motor wont rev as quickly. Some people prefer the smaller motors for good overall power, that still revs quck, and has good top end.

[wilkin250r]

I don't think you can swap for a "370" top end.

Somebody correct me if I'm wrong, but I believe the ESR 370 is basically a standard top end for a 350cc (uses a 78mm piston). However, it has different porting and a head specifically designed to go with a +4mm stroker crank.

You might be able to swap for a 350 cylinder, but not the 370, unless you plan on stroking the crank at the same time.

[rebeltoad57]

I recently spoke with ESR and they told me that the 370 uses a stoker crank.


On a different note how is that Duncan 340 Wilkin250r?

[KRMit]

Oh ok. Sounds like he'll be sticking with the 330 then. It has plenty of power anyway. Thanks for the info!

[wilkin250r]

Originally posted by rebeltoad57
On a different note how is that Duncan 340 Wilkin250r?

Lots of torque and low-end power, and a smooth powerband.

It had a vibration problem that killed the top end, and it never really revved out like it should. I never got around to getting it fixed, it's just been sitting in a crate for a while, so I can't really tell you about peak HP.

[slick250]

Originally posted by TheFontMaster
The 370 will give you a more broad powerband, more low end than the 330, and overall more horespower. On the downside the motor wont rev as quickly. Some people prefer the smaller motors for good overall power, that still revs quck, and has good top end.

Tom from ESR told me that the 370PV is more of a top end motor and is best suited for drag racing. He advised the 330 and 350PVs would make better torque down low.
I am waiting on an ESR 330PV with a 2mil stroker crank that should be here after the 1st of the year. They are machining my cases as we speak. They predict 58-60 HP out of this engine with a very nice torque curve.