Author Topic: Big cams for big bore engines.  (Read 755 times)

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Offline gschuld

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Re: Big cams for big bore engines.
« Reply #25 on: October 01, 2018, 04:17:23 pm »
Brian,

Out of curiousity, the valve diameter reduction on the exhaust valves, you trimmed down factory valves or aftermarket?

And what did you use for 35.5mm intakes?

George

Offline bear

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Re: Big cams for big bore engines.
« Reply #26 on: October 01, 2018, 05:29:41 pm »
We used stainless Mitsubishi valves for both intake and exhaust.
Not as light as some would like but they suit both the package and the purpose.
The older I get the faster I was.

Offline bear

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Re: Big cams for big bore engines.
« Reply #27 on: October 01, 2018, 05:43:00 pm »
Brian,

Methanol certainly is an advantage regarding its natural cooling effect.  Corey Ford’s green 1204cc road racer(engine built by RPE, factory stroke but huge modifications in the cylinder to accept 78(?)mm bore pistons) is an interesting example.  They run straight port heads and produce a pile of power as well.  They run methanol too correct?

I remember you not recalling your static compression numbers, but I imagine it’s pretty high.😎

George

Methanol has a very low flash point as well.  This reduces the chance of detonation issues.
The RPE bike runs methanol, yes.
From what I remember they use a solid sandcast block similar to one of ours with offset bores.

Cheers,
Brian
The older I get the faster I was.

Offline BPellerine

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Re: Big cams for big bore engines.
« Reply #28 on: October 01, 2018, 06:32:38 pm »
I visited a friend today. He had recently got a new old cam. Kenny Harmon Super F ( KH SF). Brand new in a KH marked box. Cam looked beautiful, black, grey on lobes and journal surfaces. Really good condition like made last month except for the box and aging papers.
Instruction followed with the small cam card with big numbers. Instruction that was clear is NOT FOR STREET USE.
I understand those that will have a package like this in the living room to be admired when needed ;D Lets see if this cam will enter an engine.
there is a khf cam and the super f you mention pewe,the super f is a big cam!
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Offline MRieck

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Re: Big cams for big bore engines.
« Reply #29 on: October 02, 2018, 03:45:43 am »
Brian,

Methanol certainly is an advantage regarding its natural cooling effect.  Corey Ford’s green 1204cc road racer(engine built by RPE, factory stroke but huge modifications in the cylinder to accept 78(?)mm bore pistons) is an interesting example.  They run straight port heads and produce a pile of power as well.  They run methanol too correct?

I remember you not recalling your static compression numbers, but I imagine it’s pretty high.😎

George

Methanol has a very low flash point as well.  This reduces the chance of detonation issues.
The RPE bike runs methanol, yes.
From what I remember they use a solid sandcast block similar to one of ours with offset bores.

Cheers,
Brian
Those offset bores have their own problems too.
Owner of the "Million Dollar CB"

Offline gschuld

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Re: Big cams for big bore engines.
« Reply #30 on: October 02, 2018, 06:03:47 am »
Brian,

Methanol certainly is an advantage regarding its natural cooling effect.  Corey Ford’s green 1204cc road racer(engine built by RPE, factory stroke but huge modifications in the cylinder to accept 78(?)mm bore pistons) is an interesting example.  They run straight port heads and produce a pile of power as well.  They run methanol too correct?

I remember you not recalling your static compression numbers, but I imagine it’s pretty high.😎

George

Methanol has a very low flash point as well.  This reduces the chance of detonation issues.
The RPE bike runs methanol, yes.
From what I remember they use a solid sandcast block similar to one of ours with offset bores.

Cheers,
Brian

Brian,

Thanks for the info.

Not to intentionally derail my own topic, but I believe the class Cory Forde races in requires using factory cylinder blocks(might be wrong on that).  Anyway, they used a factory cylinder block, sort of.  They milled out giant section and inserted new paired cylinder sections made from a casting using old pistons.  Bonus points for creativity😁. Then bored the new sections and installed new sleeves.  Boy those sleeves are close together.  I didn’t read any mention of offset bores, but they also made their own rods so who knows.

I’d think starting with a new cast cylinder, or a JMR billet cylinder, would be preferable if the rules allow.  But there are several factors I may be missing there.

George
« Last Edit: October 02, 2018, 06:22:58 am by gschuld »

Offline bear

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Re: Big cams for big bore engines.
« Reply #31 on: October 02, 2018, 02:03:36 pm »
George,

Major components in this case cylinder blocks can be manufactured outside the period, provided that they "look visually indistinguishable from the period components when assembled".

Mike,

Your right regarding offset bores, not a road I have been tempted to go down.
I've given myself more than enough agrivation stuffing around with these machines without opening that can of worms.  ???

Cheers,
Brian
The older I get the faster I was.

Offline Tintop

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Re: Big cams for big bore engines.
« Reply #32 on: October 02, 2018, 05:30:55 pm »
George,

Major components in this case cylinder blocks can be manufactured outside the period, provided that they "look visually indistinguishable from the period components when assembled". .........
Cheers,
Brian

I had thought about using one pf Mike's blocks (until they changed the rules >:(), as it has a similar look to a JAPauto 1000.
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Offline Don R

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Re: Big cams for big bore engines.
« Reply #33 on: October 04, 2018, 08:18:41 pm »
 I run a KH F in my 836 K0 bike, I pocket ported the head and matched things up. New stock valves. It runs good, I doubt that I really ever see the power band. (At least often) I believe I have a exhaust leak at a port, gotta get after that.

 My old 1124 drag bike has an Engle cam. It doesn't appear to be welded like the KH F road race/hot street cam. Maybe a regrind?
« Last Edit: October 04, 2018, 08:20:59 pm by Don R »
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Offline scottly

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Re: Big cams for big bore engines.
« Reply #34 on: October 04, 2018, 09:00:18 pm »
Maybe a regrind?
One of the clues that the mystery cam in my bike is a regrind is that there are almost no threads exposed over the adjuster lock-nuts; near as I can measure with the cam installed, the base circle has been reduced by about .050".
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Offline kmb69

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Re: Big cams for big bore engines.
« Reply #35 on: October 05, 2018, 07:36:13 am »
Maybe a regrind?
One of the clues that the mystery cam in my bike is a regrind is that there are almost no threads exposed over the adjuster lock-nuts; near as I can measure with the cam installed, the base circle has been reduced by about .050".

The reduced base circle cams exacerbate the rocker arm geometry problems.

 

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