Author Topic: solid lifters  (Read 844 times)

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Offline dr evo1

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solid lifters
« on: June 09, 2015, 08:39:57 AM »
would you please explain why you can't run solid lifters in a twin cam street bike.

Offline aswracing

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Re: solid lifters
« Reply #1 on: June 09, 2015, 01:48:06 PM »
I guess I don't understand the question. Why wouldn't you be able to? The lifter doesn't know whether the bike is on a street or a racetrack.

Whether or not it's a worthwhile thing to do is a whole 'nother question.

Case in point. I own a Buell XBRR. It's one of 56 factory race bikes made back in 2007 for road racing. It's motor is 1350cc, it's got trick down-draft heads with 2.250" intake valves and 1.750" exhaust valves, a pair of 62mm throttle bodies, the ports are so straight you can look down the throttle bodies and see the intake valves. The bike puts 150hp to the back tire and spins 9000rpm.

What's it got for lifters? The same exact lifters that come stock in Twin Cams.

How does it get away with that? Good valvetrain control.

The whole problem with a hydraulic lifter is that when you lose control of the valvetrain, a hydraulic lifter does what a hydraulic lifter is supposed to do, it lengthens to take up the slack. But now the valve isn't making it to the seat anymore, because the lifter "pumped-up" when the valvetrain had slack.

Keep the valvetrain from losing control, though, and it's fine, as the XBRR design proves.

We've been doing a package lately, for XL's, that's power peaking in the 7600-7700 range. Here, let me find a chart ...

Selling a ton of these packages, and it's 121hp derivative. It's a 1250 (76ci). We've actually tested the valvetrain to 8000rpm on numerous occasions. No signs of seat bounce or float. Stock lifters.

So I guess I look at solid lifters as a solution looking for a problem. And you sure don't need them for a Twin Cam that may turn what, 6500rpm typically? 7000 is a high winding Twinkie. Hell, we don't use Ti retainers on most of them. The valvetrain is easy when you're twisting 7000rpm max.