Topic: Is tuning around a standard cam worth it?

[lordmoonpie]

Hypothetical question - let's say I have a four cylinder engine and there is no way on earth I can change the cam. For the cost involved, are the performance gains of doing the head work, new valves, new carbs and a free flowing exhaust going to outweigh the performance gains? Interested in the tuner's thoughts (pro and am)...

[voxonda]

Just my two cents, from idle to say mid-range it can, but in the higher regions you need a good cam. Infact few cams out perform a good OEM one in these area's.

Rob

[lordmoonpie]

Thanks Rob - kinda where I was at. The problem is a real one, the cam is gear driven and no-one sells performance upgrade replacements or re-grinds, nor can you realistically get the gear off and back on to alter timing so I'm kinda stuck!

[754]

Talk to a cam grinder..
 For every engine with hot cams, there was a time before they had them...

 I dont think that problem slowed Burt Munro down....

[lordmoonpie]

Ha ha - nice analogy 754 I like it!

Will talk to Phil Joy on this side of the pond when I get to tearing the engine down. He may know what to do...

[simon#42]

phil joy will certainly know what to do , he will be able to hardweld the cam to alter the profile ,also if the gear has a woodruff key  you will be able to make offset keys to alter the timing . so what are you up to now simon?

[754]

There is one record nobody breaks.. being the first to do something..

 If you cut out the gear centre(not always possible), you can make a new hub, bolt gear to it and change timing.

 Cam can be altered a bit by grinding some off the base circle.

 If you want it bad enough, there is usually a way...

[kos]

Get that cam over to the bench grinder with a very fine stone/wheel and grind the base circle down a millimeter or so. Just like Pops Yoshimura used to do. Heat it up and dip in a bucket of hot oil... to re heat treat it and give it a try.

Be the first on your block to do it.!
KOS

[bucky katt]

what motor?

[lordmoonpie]

It's a CB250RR - I'm embarking on a 250-4 Hailwood replica but it has gear driven cams and the gear is an interference press fit to the cam. No-one seems to offer over the counter tuning but I do know people (Mainly in Oz) who have pressed the gear off to effectively dial in the cam. If I'm gonna go to that trouble I want some steeper and longer duration lobes! I will have the head flowed and ported, hopefully with lighter stainless valves and the obligatory FCR28mm carbs but I'm wondering if all that expense is gonna deliver me only a couple of horsepower?

Although usually Hailwood reps, mine will be a tribute to Kunihiko Akiyama. Without resorting to google - who knows what the story is there...? (he's a hero of mine...)