Cam swap on a curvey?

Looking to squeeze a couple extra horse powerings out of my engine, and having read around this sounds like a nice way to get it done. I'm swapping the heads over (eventually) anyway so thought why not have a pop at some of the old cam action at the same time.

Questions are:
- Which cams do I want? Is it just the K3 ones that do the business, and is it just the inlet ones?
- Has anyone got some they would like to part with?

Ta
Jase

[northwind]

Aye, you want the K3 intakes on the intake side, and then you move your curvy intake cams to the exhaust side (the markings don't work but otherwise they're find). It's not an optimum, max-power option but then, the entire swap costs less than even one cam for the optimum solution, and is much simpler as there's no dialing in. You get most of the benefit too, in an otherwise standard engine.

It is, IMO, the best overall power mod for the curvy, because it's so relatively cheap, there's no set up time, no monkeying about, no real tradeoff other than the usual power increase risks/wear... And it's not difficult to DIY, then again, it's also not difficult to completely **** up and mangle your top end or drop bits into the cases. Even buying new cams is only around £130 with the gaskets, that barely buys a jet kit. I think every cam from K3 up is identical.

On the other hand, if you hang around Ebay you can buy a whole engine with a bad bottom end for under £100, and liberate the tensioners too (or, if you buy a K5 onwards, the tensioners don't fit but the gear selector mechanism does) then sell the cases and heads for £50 (sometimes). The big end usually goes quick enough that the rest of the engine is fine. But this is all more hassle, I just got them new.

Northy, o wise man of SV tweakings, is it possible to slot in a pointy engine into my curvy frame, and have the fuel injection etc etc?

[EDIT] just a thought experiment, thats all

Or will it just not be worth it?

Matt

[the_lone_wolf]

Originally Posted by alpinestarhero

Northy, o wise man of SV tweakings, is it possible to slot in a pointy engine into my curvy frame, and have the fuel injection etc etc?

[EDIT] just a thought experiment, thats all

Or will it just not be worth it?

Matt

what would be the point? it would still look like a curvey

[yorkie_chris]

Worst points of both there mate!

The curvy carbs work fine, they can be set up to give about as much power anyway, and why would you want extra complications?
Such as doubling the size of the wiring loom to 50 million connections, finding somewhere to put the ECU etc. etc.

I reckon a pointy lump would fit in a curvy if you just swap the CPS for a pickup coil.

[northwind]

Yeah, more or less. I don't know exactly how it's done, but it's been done, keeping the carbs at least. Some electronic swappery and the carb boots need to be swapped with the FI boots. Maybe more, not too sure, it sounds like a mug's game to me, pointies have their own issues too. Arguably the curvy motor's slightly more reliable.

Using the FI would be, well, tricky... Fuel pump, frame and tank clearance etc could be problematic. I think it's been done, but if I remember rightly it was a massive job, the guy basically swapped in the engine and whole electrical system.

It's interesting I suppose, but i wouldn't touch it with a 10 foot pole, don't really know very much about exactly what's needed. I think Robw#70 does, maybe, he's miles better at this stuff than me. Or Zadar would as well.

[yorkie_chris]

Also begs the question why bother

Are the casings the same size? ifso could you drop the pointy engine into curvy frame and keep the curvys ignition and carbs?

[northwind]

Originally Posted by yorkie_chris

Are the casings the same size? ifso could you drop the pointy engine into curvy frame and keep the curvys ignition and carbs?

Yep. I'd stick with a curvy one though, even if it was as simple as a straight swap, some pointies have rod issues, others have crankcase cracking issues, and all of them have the stupid ******* clutch cover.

(though the rod and crank thing is very rare, and might be specific to particular years or runs, the curvy doesn't have it at all)

What sort of increases are you going to be looking at with the cam swap?

[northwind]

It depends how much of a liar you are... 3-7bhp at peak, is my generic copout amount, I actually have no idea how much mine got as my "before" dyno run turned out to have an airflow issue because of the Renegade airkit I hadn't, at that point, thrown in the bin. There was a 10bhp difference but no way is that all from the cams.

But, it's not all about the peak, frinstance, mine now doesn't drop off hard after peak, and it's close to the peak for far longer. I'd actually sooner have 65bhp and my power curve, than 75bhp and a standard curve, for the ridability. Though that's not all the cams either.

There's another option I forgot to mention, which is using another set of curvy cams in the intake side. I think either Carsick or TSM has this, with an old set of mine Not quite as good, but still probably 3-4 bhp and it should help the fall-off past peak as well. Cheaper, though, in fact it's possible I have a pair of curvy cams in the garage, if so they'd be for sale, £50