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Engine Mechanical TopicsDiscussion for motor builds, cams, head work, stripped bolts and other engine related issues. The good and the bad. If it goes round and around or up and down, post it here.
What was it about the 67's that you did not like?
I am putting together a 107 and was going to use the 57's due to the good reviews from the pros on here.
I *think* the 57's are going to be completely different than the 67. I didn't pick the 67- I let my builder pick it for me and it was really the wrong choice. My tuner (who is also a hell of an engine builder) was flabbergasted by the choice. Basically the 67 is really a hot rod cam and meant for lighter bikes. My compression was set at 10.83-1 as well and from what I've been told, it really needs to be 11.2 or so to shine. To much for my tastes. The 67 cam ALIVE at 3200 RPM all the way to the redline, but too late for me on a bagger. The Tman 590 that I have comes alive almost as wicked, but from 2200 to the redline.
I think the 57's will be fine for you, but do you think you're really going to gain much? Is it going on your current build?
Drago's 580 cam comes on at about 2200 as well.
The 57's come on at about 1800.
Yeah it is going on my current or I should say it will be a whole new motor.
I have another set of ACR heads and then the 107 S & S cylinders and the 57 cams.
Last edited by lionsm13; Jan 21, 2018 at 03:01 PM.
A 58mm throttle body is an improvement on anything over a stock 103 engine. Now is it worth the coin to do it, becomes a question only you can answer. When we build these bike engines its not cheap and the extra for a throttlebody might not be in everyone budget. I can assure you there will be an improvement but each case is different based on your build. All I can tell you is I see about 2 ft lbs and 3 HP on the dyno on a stock 103 with exhaust. I can also measure the restriction in the intake system. While that's not a lot it does show it improves a stock 103, so what is it going to do for your build and is it worth it to you?
My C ported heads from FuelMoto have 1.76" intake ports. More than likely am leaning towards the HPI-55FBW-76. Probably won't see much gain under 3k rpms but all gains above that! Thanks for that Dyno graph!
Engine build is similar to the older FM Hellraiser 107 build with a few changes, just never upgraded the throttle body.
I am in the process of clearancing the rocker covers for S&S roller rockers, and installed a SE 58mm throttle body. I feel better with the new TBW motor than HPI using my old one due to pin fretting.
Engine ran pretty good as it was, first time i maxed out the speedometer rather quickly and go power is present when needed. I wish the cams had a little more torque on the bottom end, but am not going to replace them any time soon.
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