So, do ya think that there would be a noticable difference betweeen these motors

[gryphon]

I've been collecting motor parts so that I would have a new motor (minus cases and heads) sitting here in case I ever blew up my current motor. Not long ago I got a set of cases on a whim and started thinking about building the new motor now and installing it. Not sure if there would be enough torque or HP difference between them though to really be noticable. My present motor is a 97" S&S short stroke motor. It has a 4" bore with a 3.875" stroke and 9.5 to 1 compression. The new motor would be 107ci with 4" bore and 4.25" stroke T&O Torque Monster wheels and 10.2 to 1 compression (approx). Both motors would be sharing the same S&S super E which has been bored and modified and Supertrapp 2 into 1 supermeg exhaust. I would expect that the short stroke 97 inch motor would wind up faster but that the 107 inch motor would develope more torque down low because of the longer stroke and highr compression ratio. With the 107ci motor I would like to be able to  drop one tooth on the rear sprocket (chain drive) giving me a 3.00 final drive ratio.

[wfolarry]

They would be 2 different motors. Those heavy T&O flywheels will be right at home at low RPM's because that's what they're built for. That short stroke S&S can be wound up a lot faster. If you like winding out the gears then the S&S is better. If you never go over 4K on the tach The T&O would better suit you.

[gryphon]

Well that's sort of my thinking. The short stroke motor is a lot of fun (they all are actually) but honestly with my solid mount frame, and because I almost never wind out the first 3 gears, I really very seldom go over about 4000 RPM which puts me at about 80mph in fourth and about 100mph in fifth. I think it would be a great motor in an FXR type frame. The 107ci on the other hand might be more suited to my RPM range with the 97ci kept safe in the house in case I ever need to switch it out for some reason. I'm also thinking that the 107ci might be better suited to the taller gearing I run. I'd bet that short stroke motor would really scream in an FXR with a final ration in the upper 3.20's to mid 3/30's. I am open to others opinions though. I hate doing stuff and later saying "Yeah shoot, I didn't even think about that".

[Bullwinkle]

If you ran the same heads on both, the 107 would run out of breath earlier.  Larger engine + same breathing area = lower RPM torque and power peak.  Put bigger valves in the 107 heads, which you can run due to the larger bore, it should wind out just fine.  At least to any reasonable RPM.

Riding and shifting at a lower RPM and with the longer stroke and higher compression of the 107 it will be stronger than the shorter stroke 97.

Bullwinkle

[stroker800]

   Hey Gryph....you think kinda like i do,,,,,I like to mess with styles of builds..My pan was suppose to be a short stroke (3 31/32) big bore 3 5/8 motor..I realize for todays standards its not that big.....My motor guy wantd to take it to 4 1/4 cause we had the S&S wheel and stroker cyls( got the cyls for $ 40.00). The motor pulls hard with good torque ,but I wanted a short stroke to rev..very happy with the build..Now my shovel has a 4 3/4 stroke which should have a ton of torque,,,BUT NO,,,I had stumbled on a set of S&S drag wheels and rods, they're small diameter and super light...So I have a fast revving stroker (short piston life)..The bike is a rigid and a blast to ride and still pulls hard,,,not suitable for 2 up or trailer,,,,the 2 motors are like night and day...So I think you'll love the short stroke build ,,never run aotta throttle....I tryin to build the short stroke motor again(3 31/32x 3 3/4),,,TC upper on a 74 " lower ,,kinda like a fatso but tryin to avoid the special raised deck cases....I'm ramblin ,,, to many drugs after surgery...Test ride the new motor and give us a detailed description,,,always curious whats happenin on differnt styles..
Dave

[rdkng]

Gryphon, I'm really looking forward to your results.  I almost went with T&O flywheels
when I was doing my 89 inch stroker ( 3.5 in bore & 4 5/8 stroke) in my road king.
I love the down low torque from the long stroke as I rarely go over 4K RPMs, but
of course, now that I'm use to it,  I'm thinking 'more'     The 107 sure is tempting,
but I cant do anything soon.   What cam are you going with in the 107 ?
Enjoy, thanks,  & keep us posted
rdkng 

 

[gryphon]

rdkng,
   Initialy I'm gonna try a VT-5005. I'm a little worried that with a 10.2 to 1 compression ratio the 38 degree closing on the 5005 might be a little too soon. If that's the case I'm probably going to go with my old VT-3030. I'll probably catch some flack for that one but my experience so far has been that for my riding style I really don't gain much with a large lift increase. That cam worked well for me in my 97 incher and with the higher compression in the 107 it should really wake up.

[Buddy WMC]

Gryphon,
When I spoke with Andy at Revolution the other day, the recommended cam combo for the 3.875 big bore combo at 100" was a Woods 8. My current VT-5015 has only one degree difference in the timing from the Woods 8 and should be fine. You might want to look at the VT-5010 as it has a little bit less duration than the 5015. Photojohn runs one and loves it, I'm waiting to see his Dyno results as I might go that way if it shows an improvement as I'm a bit over cammed at 85".

[gryphon]

Buddy,
   I have given a lot of thought to the 5010. I like the VT cams and the specs on the 5010 look good. I have run the 5005 before in my 97ci motor with good results. I was experiencing some pinging at high altitudes and in hot weather so I swapped it out. Later I determined that I had mistakenly set the advance curve on my ignition to the most aggressive one. I think that had it been set properly I could have avoided that. I'm thinking I might just go ahead and do my headwork and re-install them on my 97ci. I can then use it as a platform to determine what I might like to do with the 107ci. I was going to mill the heads by .030 but instead I may just go .020 and use a .036 cometic head gasket to give me the .030. If I have trouble then when I go to the 107 I'll go back to the standard .045 head gasket.

[Buddy WMC]

Gryph,

I'm interested, so please let me know how that works out. I have no pinging on 93 octane with the 5015. I have a Dyna 2000 set on single fire curve #4, we tried #5, but lost 7hp. I'm a bit overcammed at 85" and my exhaust system is hurting the Dyno numbers a bit. We know there is at least 10-15 more HP that can be achieved it's all in how we get there. I think that Photojohn is still at 80", but I'm not sure. I have the perfect setup with my ported SE heads for a 97"-100" setup and slowly I'll get there.