FMS cam specs......coming soon

[FestYboy]

wow, LOWER exhaust durration!?! that's rather unusual.

what kind of lift numbers are we talking?

[blkfordsedan]

Well, like I said, take it with a grain of salt. I didn't have the time to really devote a lot of attention to it. I ran the dial indicator directly on the lobe, but I'm not completely sure that was giving me accurate readings. The geometry of the follower style rocker arm is different than an OHV V8...where you have a crowned lifter that contacts the lobe in its center. I think I need to run the rocker arm on the cam so the pad can be taken into account. I may need to grind a flat spot on back of the rocker on which to rest the dial indicator stem. In any event, I need to think about this some more. I was surprised to see more intake duration, but a lot of SBC cams are that way. If the exhaust port flows good, it keeps the ratio of intake to exhaust flow at optimum. I'm just used to Fords and their crappy exhaust port design. Ill get lift figures when I get the rocker arms figured out, but its just over .400" judging by the lobe. I'll get it all figured out, it'll just take some time.

[blkfordsedan]

Well, I fiddled with it all afternoon trying to get a good measurement of lift at the valve. This OHC is a major PAIN. The valve retainer is so small in diameter and sits so far down in the head that its next to impossible to get the stylus of the dial indicator on it without interferance with the rocker arm. I even went to HF and bought a flexible shaft holder, but still couldn't get at it. I'll keep on it, eventually I'll get it.

[blkfordsedan]

Managed to get some more precise measurements today. I still want to measure directly on the cam lobe for comparison, but the results I got by using the indicator on the backside of the follower have been repeatable by double and triple checking, and jive with what I would expect for a mild performance cam. I will finish up tomorrow and do some more verification. I have devised a spread sheet with the results of all 3 methods I used and the measurements I took. I will also include lobe centers, overlap and all valve timing events so we can enter the specs into Desktop Dyno. After 2 of 3 methods, here's what I have thus far. Like always, they are subject to change, until I'm 100% confident with the results:


Advertised Duration (based on 0-.002" follower lift @ lobe)-

INT = 295*
EXH = 290*

Duration @ .050" Follower Lift (at lobe) -

INT = 214*
EXH = 206*

Lift @ Valve-

INT = .433"
EXH = .433"

Overlap - 25* (this looks a little low to me)

Lobe Centers - 103*

[zoom zoom]

Very interesting stuff here man, I don't know what any of it means, but its cool to read about!

[Chobobulous]

Very interesting stuff here man, I don't know what any of it means, but its cool to read about!

+1 no idea what he is talking about

[getnpsi]

I know what I know for only a few engines by comparing features, watching others waste money and change combos etc. . Now airflow of the entire head dictates if a cam with different values is going to hurt or help across the board. Losing torque is a terrible idea on a b3 less bad with a b6 acceptable with a 1.8 and also with boosting,as you can change sweet spots all over the place. I do have curiousity on the specs if there was custom cam market showing itself.

[blkfordsedan]

Very interesting stuff here man, I don't know what any of it means, but its cool to read about!

+1 no idea what he is talking about

Now is a great time to learn! Here's a link to one of the better sites i have found that is devoted to camshaft design & theory. It covers all, from basics to lobe profile design and calculations.

You don't need to understand the really technical stuff, but it helps to understand the basics. Like getnpsi said, there is a reason that you can buy of 100's of different camshafts for an engine (at least popular engines). Each profile has a different effect on the dynamics of the engine and needs to match all other aspects of the engine such as head flow, bore, stroke, rod length, compression, operating range, etc.. Understanding the basics allows you to choose a camshaft that is optimum for your application.

http://tildentechnologies.com/index.html

[Movin]

It also allows you to look at your motor and know if it is in time or not
without crank or cam marks.

[blkfordsedan]

Final results should be up in the next few days. Right now, I'm checking out the factory camshaft for comparison. The final specs on the FMS cam will be slightly different than I posted earlier. I got it figured out now and I can explain why, but it would only put everyone to sleep. I'll save that for the final detailed post (consider this fair warning, LOL).

[DriverOne]

Final results should be up in the next few days. Right now, I'm checking out the factory camshaft for comparison. The final specs on the FMS cam will be slightly different than I posted earlier. I got it figured out now and I can explain why, but it would only put everyone to sleep. I'll save that for the final detailed post (consider this fair warning, LOL).

I eagerly await your findings!

[kellen302]

We need one of them Thumpr Cams.... the roar of 1.3L of angry Korean Fury
Edit* The Thumprs just have bonus Exhaust duration I believe

[blkfordsedan]

Actually, I finished every thing up Friday afternoon. I have a spread sheet with tons of info, but I couldn't attach it to my post. I don't have internet at home (just my Blackberry) so I'll post everything up on Monday. There is some explanation that needs to go along with the results to understand it. I also wanted to play around with Desktop Dyno before I posted as well.
In addition, I want to talk to an Engineer with Crane or Comp about the design of OHC follower style cams. They appear to have some strange things going on in terms of geometry and I want to make sure I have the correct measurements.
I've never looked at the Thumper cams, but it would be the overlap that gives the choppy idle. That can be accomplished by having close lobe centers, even with relatively short duration.

[kellen302]

^Cool, I was just going off what I read in an issue of HOT ROD awhile ago

[yelo festiva]

neat

Can't wait for spec's. I have one of these to put in yelo when I get a chance. Roger never did email the spec;s to me when I got the cam. I have heard good reports on the increase in power without loss in fuel mileage.

I appreciate all the research you have done on this!