Author Topic: Building for torque? Hopefully not a stupid question (Read 6709 times)

stever · « **on:** November 09, 2010, 06:47:34 am »

Here's one in the opposite direction of max horsepower at moon shot RPM levels. 77 F2 836 motor in works. What should I pay attention to to maximize torque in LOWER RPM range? like 2500-5000 RPM? Im figuring MikeR port job for max low lift flow and velocity. 3 angle or 30 degree valve grind for flow, stock carbs. I am hung up on cam though. Everything I see seems to be geared towards high end HP gains. What should I be looking at in cam area? CycleX has a .360 lift but even that seems a little high. Any thoughts would be helpful. I'd like to see how much of a "stump-puller" I can make this thing into. Thanks, Steve

754 · « **Reply #1 on:** November 09, 2010, 06:57:38 am »

I am with you on the torque quest..more fun for everyday riding. next motor I build will be putting midrange torque over all out hp.

I have had very good results with Weber carbs, any carbs with good accellerator pumps should be a step in the right direction.

I also ran an RC 315 cam with great results, with a stock port head with springs and a good valvejob. Also lightened alternator, and at time very low gearing.

I may be wrong on this, but I dont think you can do too much to the ports and still get great lowend power.

stever · « **Reply #2 on:** November 09, 2010, 07:24:17 am »

Thanks 754, MikeR seems to think he can do it. I imagine it will involve not changing the shape or size of the ports too much, mostly cleaning up any major disruptions to smooth flow and maximize swirl,eliminating shrouding at low lift,and equalizing chamber and port size. Since the valve is only at max lift once and lower lifts twice it seems to follow that the more charge you can pack into the chamber at low lift would maximize the efficiency of the port and chamber and produce more *power* at a given RPM. This would require maximum velocity to efficiently accomplish. But the cam remains the wild card in the equation. Compression and porting must match the cam profile, I think. Am I way off base on this theory?

754 · « **Reply #3 on:** November 09, 2010, 07:34:48 am »

What he said makes sense, I was thinking that most heads modified for top end HP may not help your needs.

Cams are dependent on the the combination of your other parts, and can vary with different riding styles..

stever · « **Reply #4 on:** November 09, 2010, 07:58:44 am »

Hmmm. I dont suppose you have the cam card from the RC315? Curious about lift and duration. Dynoman has a 360 lift, 250 at .050 duration one they recommend for F engines. I would like to stay away from heavy springs due to the wear that can result from them. Hondaman also mentions in his book using adjustable cam gears and advancing as much as 10 degrees to lower the torque band, not sure how far an F motor will go, but the theory sounds logical. Also using 4-4 megaphone exhausts with longer head pipes to try to lower the torque band. In *theory* should work.

Sam Green Racing · « **Reply #5 on:** November 09, 2010, 08:36:39 am »

Megacycle 125-65 gave me 62ft lb with just 86bhp. 836, Ported head, KW 5mm stems and 2mm up on inlets. CR31 carbs, free flowing exhaust and Boyer ignition. I think in the torque department, this motor out performed all the bikes that were dynoed and posted their figures on here, even MikeR was shocked when it out performed the 98bhp Million dollar CB in the torque stakes. Mike didn't port this one but he played a very big part in the bikes success. My current CB836 sports a JMR racing sticker though.

Sam.

MRieck · « **Reply #6 on:** November 09, 2010, 08:49:09 am »

Quote from: SamCB750A on November 09, 2010, 08:36:39 am

Megacycle 125-65 gave me 62ft lb with just 86bhp. 836, Ported head, KW 5mm stems and 2mm up on inlets. CR31 carbs, free flowing exhaust and Boyer ignition. I think in the torque department, this motor out performed all the bikes that were dynoed and posted their figures on here, even MikeR was shocked when it out performed the 98bhp Million dollar CB in the torque stakes. Mike didn't port this one but he played a very big part in the bikes success. My current CB836 sports a JMR racing sticker though.

Sam.

That CR engine had more compression built into. That helps torque too.

stever · « **Reply #7 on:** November 09, 2010, 09:01:45 am »

Wow Sam, thats a pile o' torque! At what RPM did it make the torque peak? Can you post a dyno pull please? If it made that torque at 5000 or less I'll just have to ponder building one just like that, damn the cost! I sure would like a nice flat torque curve but Im not sure it will happen with these motors.

Sam Green Racing · « **Reply #8 on:** November 09, 2010, 09:14:52 am »

It started just after at about 5,400 through to 6,500.

http://gallery.sohc4.net/main.php?g2_itemId=298879

Sam.

Sam Green Racing · « **Reply #9 on:** November 09, 2010, 09:17:39 am »

All graphs. http://gallery.sohc4.net/main.php?g2_itemId=13118

Sam.

MCRider · « **Reply #10 on:** November 09, 2010, 09:27:50 am »

I think your goal of 2500 to 5000 rpm is tough to meet. Its the nature of the engine to make torque higher up. However, maximizing it at 5000+ will likely maximize it at sub-5000. So you'll have more torque lower, than stock, but the big result is higher. Still shifting at 6000 will stretch the shoulder sockets nicely.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #11 on:** November 09, 2010, 09:47:03 am »

Quote from: stever on November 09, 2010, 07:58:44 am

Hmmm. I dont suppose you have the cam card from the RC315? Curious about lift and duration. Dynoman has a 360 lift, 250 at .050 duration one they recommend for F engines. I would like to stay away from heavy springs due to the wear that can result from them. Hondaman also mentions in his book using adjustable cam gears and advancing as much as 10 degrees to lower the torque band, not sure how far an F motor will go, but the theory sounds logical. Also using 4-4 megaphone exhausts with longer head pipes to try to lower the torque band. In *theory* should work.

Dynoman also sells his RC315. Why not ask him?

stever · « **Reply #12 on:** November 09, 2010, 09:50:11 am »

Wow Sam, thats GREAT info! Thanks! Nice smooth rising torque curves from 3500. If I read it correctly CBenF1 had a whopping torque spike about 4500, what would cause that? I knew I wouldnt get miles of torque way low, but I think I would settle for a flatter torque curve. Is it just impossible on these guys?

stever · « **Reply #13 on:** November 09, 2010, 09:55:00 am »

Thanks Jerry, I saw DP and Webcams listed, no RC315. Is this something Id have to call about?

Sam Green Racing · « **Reply #14 on:** November 09, 2010, 09:57:34 am »

Bens motor didn't have much done to it if I remember correctly, just the 836 kit.

Plus he is in Aus so his float hight will be up the cock.

Sam.

MCRider · « **Reply #15 on:** November 09, 2010, 09:57:59 am »

Quote from: stever on November 09, 2010, 09:55:00 am

Thanks Jerry, I saw DP and Webcams listed, no RC315. Is this something Id have to call about?

I think the DP (DynoMan Products) is a converted RC.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #16 on:** November 09, 2010, 09:58:08 am »

DP315. This is supposed to be the RC315.

simon#42 · « **Reply #17 on:** November 09, 2010, 10:41:44 am »

i use a megacycle 125 65 cam in my 1978 f2 and i would strongly recommend one for street use , is better in every department than the standard cam and as sam said has a very strong mid range

paulages · « **Reply #18 on:** November 09, 2010, 11:08:40 am »

BIG BANG cam...

kos · « **Reply #19 on:** November 09, 2010, 01:17:49 pm »

Quote from: SamCB750A on November 09, 2010, 08:36:39 am

Megacycle 125-65 gave me 62ft lb with just 86bhp. 836, Ported head, KW 5mm stems and 2mm up on inlets. CR31 carbs, free flowing exhaust and Boyer ignition. I think in the torque department, this motor out performed all the bikes that were dynoed and posted their figures on here, even MikeR was shocked when it out performed the 98bhp Million dollar CB in the torque stakes. Mike didn't port this one but he played a very big part in the bikes success. My current CB836 sports a JMR racing sticker though.

Sam.

That is a high torque number....

KOS

kos · « **Reply #20 on:** November 09, 2010, 01:23:39 pm »

Big bang cam, here in stock at m3 Racing USA

1 & 4 go boom, then 2 & 3 go boom....

Going into my 750 SOHC Trackmaster flat track racer for next year. Neat thing is, all you do is drop it in, no changing timing are anything else.

KOS

paulages · « **Reply #21 on:** November 09, 2010, 03:44:04 pm »

Quote from: kos on November 09, 2010, 01:23:39 pm

Big bang cam, here in stock at m3 Racing USA

1 & 4 go boom, then 2 & 3 go boom....

Going into my 750 SOHC Trackmaster flat track racer for next year. Neat thing is, all you do is drop it in, no changing timing are anything else.

KOS

mark- how low will this cam allow the engine to idle? is the stock crank/rotor heavy enough carry it through? i imagine with a 180 degree orientation it shouldn't be too much of a problem, right? to i've always wanted to try one.

Retro Rocket · « **Reply #22 on:** November 09, 2010, 03:57:56 pm »

More info on the big bang cam please......Especially what it does to performance {torque and hp} and if it changes where about in the rev range things start to happen.....Intrigued....

Mick

MRieck · « **Reply #23 on:** November 09, 2010, 07:46:02 pm »

I have an AMA Hill Climb Champion buddy that used that set up. Rick Stetson did that engine.

MRieck · « **Reply #24 on:** November 09, 2010, 07:51:58 pm »

Quote from: BobbyR on November 09, 2010, 07:49:18 pm

What kind of oil should you use in these engines?

Slippery stuff Bobby. Real slippery stuff.

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Author Topic: Building for torque? Hopefully not a stupid question (Read 6709 times)