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Aftermarket BIG Valve Cylinder Head

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1 hour ago, Bigfatredpig said:

Your point ignition, you use a centrifugal advance or a vacuum setup?

how do you get around spring bounce at high rpm? Your dyno went past 16k 

Why does every single engine builder using the older xr100s update to a Cdi ignition?

 

Think about 'points bounce' like this:

A twin point V8 Chevy distributor has 8 lobes and runs at half engine speed.  How many times per minute are the breakers opening at 6000 engine rpm?

I don't have a dyno. I mentioned building one.

 Engine speed was measured with an inductive device.

Edited by Momus

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13 minutes ago, Momus said:

I'm not sure what you mean by my training thread.

To build a 230F - say 250 cc actual capacity to make 35 hp at 8500, let alone less would not be easy at all.  It requires 22 lb/ft of torque which works out to a BMEP of 221 psi which is a fully developed Nascar Engine 2 valve bench mark figure. It would require a lot of specialised components and development.  Unless someone wanted to fund it as a project I would not be trying for that figure.

But a 230f top end on a sl 125 bottom end, it would be possible you say? Then teach us dummies how YOU would do it. And you will get all of the credit you desired. We don’t do NASCAR stuff here in this thread, that’s a different thread also. 
I don’t care one bit how many cc’s it has or even if it has been converted to (retarded timing) points ignition and lives at 16,000 rpm or higher, as long as it’s a 230f top end (of any year model) and has 35 or more HP with massive torque from just off idle, please spill the beans and tell us how it’s done. 

Edited by adnohguy

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25 minutes ago, adnohguy said:

But a 230f top end on a sl 125 bottom end, it would be possible you say? Then teach us dummies how YOU would do it. And you will get all of the credit you desired. We don’t do NASCAR stuff here in this thread, that’s a different thread also. 
I don’t care one bit how many cc’s it has or even if it has been converted to retarded points ignition and lives at 16,000 rpm or higher, as long as it’s a 230f top end (of any year model) and has 35 or more HP with massive torque from just off idle, please spill the beans and tell us how it’s done. 

I said I was contemplating building a 230F on an SL100 bottom. They have the close ratio gear set.

You are making the stipulations; about 8500 rpm "and has 35 or more HP with massive torque from just off idle"  not me.

I'm talking about a MX racing engine- and I made that clear.

It's an engineering exercise- move the torque up the rev range using all the usual techniques and stop when you get your horses and then work on reliability and range.  Not easy though getting 140 hp per litre from 2 valves.

Edited by Momus

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49 minutes ago, Momus said:

I said I was contemplating building a 230F on an SL100 bottom. They have the close ratio gear set.

You are making the stipulations; about 8500 rpm "and has 35 or more HP with massive torque from just off idle"  not me.

I'm talking about a MX racing engine- and I made that clear.

It's an engineering exercise- move the torque up the rev range using all the usual techniques and stop when you get your horses and then work on reliability and range.  Not easy though getting 140 hp per litre from 2 valves.

Sounds like your back peddling and it’s not possible for you to make it happen, ever, no matter what cases you bolt the 230f top end on, or what type of ignition system is used? What gives, why not, or if I’m guessing incorrectly, then when?

I was hoping for an enlightening education and am more that willing to learn from you or anyone for that matter. That’s why I joined TT, to learn.  
Please don’t let us down sir, man up and make it happen. Soon. 

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11 minutes ago, adnohguy said:

Sounds like your back peddling and it’s not possible for you to make it happen, ever, no matter what cases you bolt the 230f top end on, or what type of ignition system is used? What gives, why not, or if I’m guessing incorrectly, then when?

I was hoping for an enlightening education and am more that willing to learn from you or anyone for that matter. That’s why I joined TT, to learn.  
Please don’t let us down sir, man up and make it happen. Soon. 

Who are you mate- this forum's talking parrot?  Demanding this and demanding that.  LOL.

I said I have an interest in building a decent big capacity SL100 type race engine for a vintage racing class.

It will happen, and like some of my other builds, will probably be a bit advanced for the average IC engine enthusiast.

 

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A torquer engine doesn't normally equate to a high hp revving engine. The torquer produces good bottom end torque but if it doesn’t rev and not great hp. 
The bikes Momus are talking about appear to be race engines producing high rpm and very high HP. 
Got to get some of those bikes on a dyno to see what they really produce. 

Edited by SteveThe Snakes

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On ‎1‎/‎15‎/‎2021 at 7:42 PM, MetricMuscle said:

I believe Doogee is referring to my project.  

  Correct-uh-moon-do there Metric.

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22 hours ago, mixxer said:

I clay molded to cc measure the "potential change to compression"...

  What'd ya come up with on that John? The 230 head, right?  I haven't tried to fix the port break thru on the head I got from Ricky but the chamber weld up went well. Do you think it's worth the trouble. I'm still looking at adapting a 230 head on my XR200 vintage bike motor. (though that project is moving slowly due to other more pressing projects, ala my Bro's Hawk, and other things).

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10 hours ago, Momus said:

race engine for a vintage racing class.

  I'm all ears to hear about that. Although I'm more interested in an XR200 platform since that's what I'm putting in an RM125N (1979) chassis. Max power "under the curve" and not just big peak power #'s is what I'd be interested in.

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4 hours ago, Doogee57 said:

  I'm all ears to hear about that. Although I'm more interested in an XR200 platform since that's what I'm putting in an RM125N (1979) chassis. Max power "under the curve" and not just big peak power #'s is what I'd be interested in.

The big SL100 is something I've been contemplating for a while and working up to. Class rules require standard appearing castings for the period so the early SL100/125 type clutch case and cylinder casting and probably the crancase located cam chain tensioner rather than the 230 type cylinder thing. The 230 head is probably what I'll go with but a welded up split type early head may be as good. I'll have to cut one up to see if there is any worthwhile difference.

With the squarish bore stroke dimensions you end up with at round 250 cc, the inlet valve area is pretty small.

Getting top end is the issue, not a strong mid, is the way I see it.   Well developed MX 250 4 valve race engines are using 2 intake valves about the same size or larger than, the biggest single valve commonly fitted in the SL/XR/CRF's,  to get their tractable, reliable 50 hp.

  

Edited by Momus

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Small minds and all.

I'm building a HONKI  (HONda suzuKI) at the moment as well. 1977 RM125B frame based.

Mine has an XL250 centerport engine though.

Just about ready for finish welding- still have to tab for the CDI box and coil and a coule of other things.

001.JPG

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5 hours ago, Doogee57 said:

  What'd ya come up with on that John? The 230 head, right?  I haven't tried to fix the port break thru on the head I got from Ricky but the chamber weld up went well. Do you think it's worth the trouble. I'm still looking at adapting a 230 head on my XR200 vintage bike motor. (though that project is moving slowly due to other more pressing projects, ala my Bro's Hawk, and other things).

Nope Doogee... It was the aftermarket 100 head that I did that on... There wasn't enough compression change to make it worthwhile...

If it was, I was going to use it with the big bore almost flat top wiseco piston I already had ... But changing the combustion chamber in that manner would have meant that any domed piston would need additional work to be compatible with it...

I ended up going with a Takegawa higher comp big bore piston... Adding a stroker crank to go from 120 to ~130cc with that bore kit.... and ordering a .005" thick custom copper base gasket to pull assembled squish clearance into the low 30's....

All that in combination yielded a final measured compression ratio of 11.3:1 for my little woods thumper... Basically 2 full points up from stock comp with 130cc vs 100cc....

It would be worthwhile to try on the 230 because you are starting with the stock combustion chamber size and compact combustion chambers are more efficient than big open ones... But a lot more work than finding compression with different pistons/ displacement/ squish tightening....

The aftermarket head I was using for my 100 had a much larger combustion chamber than stock... The valves had to be farther apart in the head than oem to accommodate the larger valves and keep them from interfering during overlap...

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2 hours ago, mixxer said:

changing the combustion chamber in that manner would have meant that any domed piston would need additional work to be compatible with it...

I read about a Harley head that had a "bathtubbed" chamber that used a domed piston with a 30 degree squish area, at about .030"-.035", to match the heads shape. Made best power with only 23-24 degrees of total spark advance. Ran much cooler too. That's a seriously efficient, quick burning, chamber. Kinda whit I was contemplating with the 230's head. "Hammerhead" I'm pretty sure it's called.

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On 1/17/2021 at 9:34 AM, Doogee57 said:

I read about a Harley head that had a "bathtubbed" chamber that used a domed piston with a 30 degree squish area, at about .030"-.035", to match the heads shape. Made best power with only 23-24 degrees of total spark advance. Ran much cooler too. That's a seriously efficient, quick burning, chamber. Kinda whit I was contemplating with the 230's head. "Hammerhead" I'm pretty sure it's called.

Hammer Performance is probably what you were thinking of but one of the Buell engines had close to that set up.

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Edited by MetricMuscle

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On 1/18/2021 at 1:34 AM, Doogee57 said:

I read about a Harley head that had a "bathtubbed" chamber that used a domed piston with a 30 degree squish area, at about .030"-.035", to match the heads shape. Made best power with only 23-24 degrees of total spark advance. Ran much cooler too. That's a seriously efficient, quick burning, chamber. Kinda whit I was contemplating with the 230's head. "Hammerhead" I'm pretty sure it's called.

Link to article or a test graph?

\

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8 hours ago, MetricMuscle said:

Hammer Performance

   Yeah, that's them. It was in one of Kevin Cameron's columns that I first read about that set-up and the really short spark advance. The compression was pretty high too, like >12:1. Hammer Performance doesn't give real deep details on their web site. Still, the principles and tech involved are solid. That's where I got the inspiration for modding the 230's chamber.

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2 hours ago, Doogee57 said:

   Yeah, that's them. It was in one of Kevin Cameron's columns that I first read about that set-up and the really short spark advance. The compression was pretty high too, like >12:1. Hammer Performance doesn't give real deep details on their web site. Still, the principles and tech involved are solid. That's where I got the inspiration for modding the 230's chamber.

So link or details?

23 or 24 degrees for maximum torque is a very low number.

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2 minutes ago, Momus said:

So link or details?

  I can machine a combustion chamber, fab a tapered header tube, etc. etc., but I'm not computer 'techish' enough to do links (sorry) but if You Google "Hammer Performance" they've got pictures of their chambers and matching pistons that use this technique. No in depth info on ignition or cam timing though. I think their stuff is the off-shoot of the Harley Twins class road racer that Kevin Cameron wrote about.

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On 1/17/2021 at 9:34 AM, Doogee57 said:

I read about a Harley head that had a "bathtubbed" chamber that used a domed piston with a 30 degree squish area, at about .030"-.035", to match the heads shape. Made best power with only 23-24 degrees of total spark advance. Ran much cooler too. That's a seriously efficient, quick burning, chamber. Kinda whit I was contemplating with the 230's head. "Hammerhead" I'm pretty sure it's called.

I remember reading Kevin Cameron's writing on that....

The squish band becomes like a 2 stroke design where the piston crown angle matches the angle of the squish band in the head for better aiming of the turbulent squish charge into the combustion chamber...

You also have to clearance around the valves so you don't add shrouding restrictions to flow as you close up the chamber...

Not a small amount of work...!

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34 minutes ago, mixxer said:

Not a small amount of work...!

  Something you are quite familiar with, I'm sure.

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