VC440 Speed Update

[slonomo]

I'm just not sure how much air one can flow through this little head on the clone engine. I have ported it, not aggressively though. I do have a spare head I could experiment with to get more flow out of. I also could mill this one down and get 11:1 compression or more. Right now I'm still below 9.5:1 I think. So my engine is just barely modded. I have the internals done, now I need to get better rockers and better carb. I'm not afraid of running at higher rpm at short bursts though. If a 34mm or 36mm won't bog down at low rpm then I'd be open to that. I'd just like to see someone else experiment on their dollar first LOL! At $80 I can get a Kehin copy of a Harley Davidson carb with an accelerator pump, it's 32mm. I know guys have run these without any low end loss. Parsons Racing sells a 40mm alky carb that is said to really rip! But it's $300.

So what other kinds of mods need to be done to run at higher rpm? Roller rockers? I don't think there is anythink else available for the clones. I think I have 32lb dual valve springs, might be 55lb not sure. There are 65 lb springs out there. So heavier springs at really high rpm right?

[1989Marathon]

You need the stiffer springs to keep the valves from floating. Not sure what that means for a clone. Common sense goes a long way when experimenting.

[1989Marathon]

Originally Posted by slonomo

I'd just like to see someone else experiment on their dollar first LOL!

My wife says the same thing... but that doesn't stop me...

[slonomo]

Originally Posted by 1989Marathon

You need the stiffer springs to keep the valves from floating. Not sure what that means for a clone. Common sense goes a long way when experimenting.

It comes with heavy duty dual springs, which is what I have. I just don't know how much rpm they are good for with the torque cam I have.

I think I'll start on the "cheaper" end with the $80 Keihin copy and see where that leads. If it's not enough, I'll look at something larger.

Wonder what kind of jets these carbs use. If they are copies, wouldn't you assume they are Keihin type jets?

[1989Marathon]

I'm a Mikuni freak. Don't know nothin bout Keihin carbs. Sorry.

[slonomo]

So the benefit of the Mikuni is the ease of tuning correct? I'd go for a Mikuni if I could find one that wasn't $150. Genuine Mikuni is all I find, no copies. Does tuning with the needle do what an accelerator pump does? Fuel at off idle to mid?

[slonomo]

What about this?

http://www.parsonsracingengines.com/...tor%20525.0018

[Warlordsix]

Originally Posted by slonomo

I'm just not sure how much air one can flow through this little head on the clone engine. I have ported it, not aggressively though. I do have a spare head I could experiment with to get more flow out of. I also could mill this one down and get 11:1 compression or more. Right now I'm still below 9.5:1 I think. So my engine is just barely modded. I have the internals done, now I need to get better rockers and better carb. I'm not afraid of running at higher rpm at short bursts though. If a 34mm or 36mm won't bog down at low rpm then I'd be open to that. I'd just like to see someone else experiment on their dollar first LOL! At $80 I can get a Kehin copy of a Harley Davidson carb with an accelerator pump, it's 32mm. I know guys have run these without any low end loss. Parsons Racing sells a 40mm alky carb that is said to really rip! But it's $300.

So what other kinds of mods need to be done to run at higher rpm? Roller rockers? I don't think there is anythink else available for the clones. I think I have 32lb dual valve springs, might be 55lb not sure. There are 65 lb springs out there. So heavier springs at really high rpm right?

The way I see the 32mm size is this...That size CV carb has come stock on a LOT of 400-450cc quads, and they don't lack in the power department...nor do they lack for grunt down low...so it seems reasonably sized for our typical applications.

[Warlordsix]

Originally Posted by slonomo

It comes with heavy duty dual springs, which is what I have. I just don't know how much rpm they are good for with the torque cam I have.

I think I'll start on the "cheaper" end with the $80 Keihin copy and see where that leads. If it's not enough, I'll look at something larger.

Wonder what kind of jets these carbs use. If they are copies, wouldn't you assume they are Keihin type jets?

KeiHin jets fit. The carb looks identical, too. Quality seems similar, too.

[geoffw]

Stock clutch is maxed out at 5500on the STOCK engine. All those mods make great power up to 5500 but you are choking that thing out with the stock carb.

-Geoff