Cam thread

[Jim Ratto]

Should we start a new thread just about cam thoughts, questions, valve timing...etc?

[Jon]

ABSOLUTELY 

[Cheesepanzer]

What would you like to know, Jim?     J/K.

A friend and I have had numerous discussions on cam profiles, timing, the differences between advertised durations vs. durations at .050", and more.  When you step back and begin comparing different cams available today it can be very confusing.  I think most people just go with the crowd, or what the guy behind the counter recommends, or what their head builder recommends, etc.

We've had fun trying to "map" cam profiles and look at valve timing.  While its been entertaining, I feel like I am no further along in understanding what the perfect cam is than I was before.

On my current build, I've managed to get myself very confused around whether to go with a FK8 cam that I have or buy a W125.  The engine will be a 2332cc street engine with 40x35 unwelded heads, IDF's, etc.  An FK8 cam is a great all around cam, but I had a great experience with a 2016 engine I built with a W125 cam.  I've been comparing the FK8 with 1.4's to a W125 with 1.25 rockers, and can't make up my mind.  On paper the cams campare fairly well.  The FK8 has 258 deg duration @ .050" compared to the Engle 125 with 262.  However, the advertised durations are very close; FK8 @ 298, W125 @ 301.  The extra duration might work well with the big stroke.  As for lift, the FK8 w/1.4's is .535" whereas the W125 would be .523".  I think the W125 would produce more horsepower.  But what you can't see unless you compare the cam cards is the valve timing.

I just dunno...

I'm faced with a similar dilema with my race engine where I'm considering some of the newer FK series cams and a couple of CB cams.  Or, I could toss back in the tried and true FK89.   

[Jim Ratto]

 

Same here. I've read the words away in some books I have read them so many times, and I "get" some of it, but there's still a whole universe of cam stuff I don't comprehend as of yet. I take what I've been taught over the years, and tired it, and the stuff that didn't break stuff or make the cars run like pigs, stuck with.
I used to have a row of big VW cams....and for fun one day, plotted all of them with graph paper and colored pencils. every .010" I measured duration....yes it took hours and hours and what did I get out of it? Well, I saw the 86B Web, has more duration in the mid lifts than the good old K8. The clay Smith 320 is wilder than the FK87 and the 86C, as far as ramp acceleration and duration at all lifts. Don't remember what else, and I don't have the graph any more. There are so many things that come into play with cams, and still, I've yet to find one that "turns me on" when combined with my heads, carbs, cc's, etc. I guess I'm still looking for that "early 911S" powerband.... in a VW motor. 
Lobe centers? Intake centerline @ ___? Seat duration vs. .050", duration vs. single cylinder displacement, duration vs. compression ratio, big ports-short duration, small ports (high air speed) long duration?  Cam and lifter life? Gosh we could go on for years, couldn't we? Throw any thoughts out there.... fact, theory, question, voo doo, rumor....

[redbluebug]

What would you like to know, Jim?     J/K.

A friend and I have had numerous discussions on cam profiles, timing, the differences between advertised durations vs. durations at .050", and more.  When you step back and begin comparing different cams available today it can be very confusing.  I think most people just go with the crowd, or what the guy behind the counter recommends, or what their head builder recommends, etc.

We've had fun trying to "map" cam profiles and look at valve timing.  While its been entertaining, I feel like I am no further along in understanding what the perfect cam is than I was before.

On my current build, I've managed to get myself very confused around whether to go with a FK8 cam that I have or buy a W125.  The engine will be a 2332cc street engine with 40x35 unwelded heads, IDF's, etc.  An FK8 cam is a great all around cam, but I had a great experience with a 2016 engine I built with a W125 cam.  I've been comparing the FK8 with 1.4's to a W125 with 1.25 rockers, and can't make up my mind.  On paper the cams campare fairly well.  The FK8 has 258 deg duration @ .050" compared to the Engle 125 with 262.  However, the advertised durations are very close; FK8 @ 298, W125 @ 301.  The extra duration might work well with the big stroke.  As for lift, the FK8 w/1.4's is .535" whereas the W125 would be .523".  I think the W125 would produce more horsepower.  But what you can't see unless you compare the cam cards is the valve timing.

I just dunno...

I'm faced with a similar dilema with my race engine where I'm considering some of the newer FK series cams and a couple of CB cams.  Or, I could toss back in the tried and true FK89.   

You need a Cam-o-Matic!

Same here. I've read the words away in some books I have read them so many times, and I "get" some of it, but there's still a whole universe of cam stuff I don't comprehend as of yet. I take what I've been taught over the years, and tired it, and the stuff that didn't break stuff or make the cars run like pigs, stuck with.
I used to have a row of big VW cams....and for fun one day, plotted all of them with graph paper and colored pencils. every .010" I measured duration....yes it took hours and hours and what did I get out of it? Well, I saw the 86B Web, has more duration in the mid lifts than the good old K8. The clay Smith 320 is wilder than the FK87 and the 86C, as far as ramp acceleration and duration at all lifts. Don't remember what else, and I don't have the graph any more. There are so many things that come into play with cams, and still, I've yet to find one that "turns me on" when combined with my heads, carbs, cc's, etc. I guess I'm still looking for that "early 911S" powerband.... in a VW motor. 
Lobe centers? Intake centerline @ ___? Seat duration vs. .050", duration vs. single cylinder displacement, duration vs. compression ratio, big ports-short duration, small ports (high air speed) long duration?  Cam and lifter life? Gosh we could go on for years, couldn't we? Throw any thoughts out there.... fact, theory, question, voo doo, rumor....

I have been doing the same thing Jim.  It takes some time, but it is interesting to see how the cams stack up on paper.  I think WardVwracer will have his chance to stare at the indicator and degree wheel soon

[Jim Ratto]

More thoughts guys.

all out hot street motor, powerband.... ? Fair idle, with heavy beat, come off idle cleanly, good torque above 2700, "rush" between 4000 and 6500-7000, 540cc per cylinder, 44 x 37.5 valves, 9.5:1....

What ideas?  268 @ .050", 108 lobe separation, intake lobe peak @ 104- 5?-6?
?

[haldex201]

My new racing engine willl be with and Fk 87, and the man behind say to me that the lobe Center must be in between 105 to 106 comp. ratio 12,3:1 Valve size 48mm in 38mm out.  Crank 72mm, with 5,7" Rods.

Had hope to use a FK 89, but i need the torque from the buttom of curve. The FK 89 dont deliver torque before you hit 4500 RPM

I hope to dyno it in May

Best regards

Haldex201

[Jim Ratto]

yeah, FK87 needs some squeeze to get it to pull hard, which your motor should!

Where is that Johannes at? I want to hear more of his thoughts....

[Gabetion2000]

Ive got a question. Why arent split duration cams used more in aircooleds (sp?)? Its seems you could control dynamic compression easier this way. Another, in general how much different is advertised duration from seat duration? Me and my friends argue about this all the time. I would like to degree a couple of popular cams and see how far off they acually are. Also what effects would high lift and low duration( .550 lift and 230 duration @.050) and the opposite (.430 lift 280 duration @.050) have on a motor? Has anybody ever experimented with this? or is this a stupid question? Just curious.

[Jim Ratto]

Ive got a question. Why arent split duration cams used more in aircooleds (sp?)? Its seems you could control dynamic compression easier this way. Another, in general how much different is advertised duration from seat duration? Me and my friends argue about this all the time. I would like to degree a couple of popular cams and see how far off they acually are. Also what effects would high lift and low duration( .550 lift and 230 duration @.050) and the opposite (.430 lift 280 duration @.050) have on a motor? Has anybody ever experimented with this? or is this a stupid question? Just curious.

Hi Gabe, I think Web Cam offers a number of split duration cams. I've never played with one. Certainly not a stupid question!!!
I would like to hear beliefs of moderate lift/long duration cams vs. high lift/short duration stuff. Just thinking about the two, I belive the former would be gentler on valvetrain than the latter. If it helps the theory, when I ran the FK87, it was by far, the quietest valvetrain I've ever run. I'd have to say the VZ25 or the Web 110 with rockers were the loudest.
I think when it comes down to it, it goes beyond just lift and duration....meaning things like ramp acceleration (lift per degree per degree) and how long the cam has the valve in the mid lift area, and where the valve is held open (vs crank position).

[Roman]

Ive got a question. Why arent split duration cams used more in aircooleds (sp?)? Its seems you could control dynamic compression easier this way. 

I know Johannes Persson is using a lot of split duration cams. I saw a big pile of Engle cams - FK89-91, FK89/87 etc.

[Jim Ratto]

anyone's thoughts on Engle FK47 for hot street, 2165cc, IDAs, 44x37 sideways D-port 9.5:1+
?
civilized under 3K isn't mandatory. Would use with 1.3 rockers.

[Gabetion2000]

Also, say you have a (hypothetical) cam with a seat duration of 320 and duration at .050 is 220 degrees. Then you have a cam with a seat duration of 320 degrees and duration at .050 is 310 degrees. Ive been told you want the cam with more distance between the .050 measurement and the acual mesurement, or the motor will be "Lazy". How would the two different cams drive? It seems to me that you would want the cam with the closer specs because it has more time with the cam open at higher lift. Any ideas?

[nicolas]

as much as i would like to know about it i have no clue what cams do and why they do what they do... so somebody needs to step up and put some knowledge in our little heads

[Jim Ratto]

as much as i would like to know about it i have no clue what cams do and why they do what they do... so somebody needs to step up and put some knowledge in our little heads

there are lots of good books out there, that will probably give you the answers...

"Four Stroke Performance Tuning" by AG Bell
"Scientific Design of Intake and Exhaust Systems" by Philip Smith and John C. Morrison

also this website, though aimed at Datsun tuners, has some good explanations too!
http://www.datsport.com/Racer_Brown_Menu.html

If I had a scanner I could copy some of the papers I have left over from school.

[Jim Ratto]

Also, say you have a (hypothetical) cam with a seat duration of 320 and duration at .050 is 220 degrees. Then you have a cam with a seat duration of 320 degrees and duration at .050 is 310 degrees. Ive been told you want the cam with more distance between the .050 measurement and the acual mesurement, or the motor will be "Lazy". How would the two different cams drive? It seems to me that you would want the cam with the closer specs because it has more time with the cam open at higher lift. Any ideas?

Hi Gabe,
I would "assume" you would want the .020" (or seat) duration to NOT be much greater of a figure than the .050" number, within mechanical limits (if they were too close, the valves would "slam" open and shut, breaking things), I think the closer you can get these numbers (within safe limits), the more you have the valves open, giving better cylinder filling and scavenging. Somewhere I have a graph that shows this and explains it (basic message was why you'd want valve to open farther than the lift that the valve-port stops flowing at).

The Smith book has some very interesting studies done on pressure within cylinder, dependent on piston travel vs. valve lift.  Amazing what some longer duration can do to get cylinder pressure above 1 Atm even before piston gets to BDC on the intake stroke.

What's next?

[Harry/FDK]

F+".K, couldn't the whole world be Inch OR Metric. (Excuse my french).

[Jim Ratto]

F+".K, couldn't the whole world be Inch OR Metric. (Excuse my french).

no kidding! I often read euro duration figures and wonder WTF? You guys measure @ mm?
or ?

[OldSpeed]

I also have a few questions which i'm hoping you guys could help me with.

I'm interested in building a 'hot' 1300 engine just for the novelty of experimenting with my '72 beetles stock displacement size as a bit of a mouse motor challenge.

The specs should be roughly:

AS41 OG Case
69mm 4140 Forged Counterweight crank.
Stock heads ported and flycut to increase compression a little.
Lightened flywheel, 8 doweled.
Fully balanced crank, rods, flywheel, clutch etc.
1 1/2 Inch header.
Power Pulley.
Full flow oiling with external filter.
Twin 40mm Kadrons with retro velocity stacks and perforated steel filters.
010 Distributor.

The thing is that i'm not sure which valvetrain set up to go for. With the motor being relatively small displacement i'm thinking i should stick to stock ratio rockers and go for a relatively mild cam with plenty of lift but little duration as overlap would affect low RPM compression i think?

What would you recommend? I'm thinking maybe an Engle 100 but maybe i could go for something a little more wild?

Thanks 

[OldSpeed]

how about Engle FK7 with 1.4's

Thanks for the suggestion.

That would be a good combination for producing maximum BHP from the engine size i think but the bug is my first and only car at the moment so i need it to be torquey at low revs and to idle nicely. Will the FK8 and 1.4's be lumpy at low revs?

If i can avoid it i'd like to either just change the cam or the rockers as my budget is relatively small and i can't really afford both unless its essential. Student budget...

[OldSpeed]

The K8 is even a hotter cam than K7.
If you need good torque all around, then stock cam with ratio rockers or Web 218 or Engle 100
The VZ14 would intrigue me too.... but be prepared for worn out stuff.

Sorry, that was a typing mistake, i meant the K7.

So for maximum torque and drivability an Engle 100 or ratio rockers sounds best to me. I don't want to experiment too much as it needs to be reliable!

Thanks for your help.

 

[Tony Wilkie]

I like the engle 100 with 1.25 rockers. Lots of torque and will pull to 6500rpm 

tw

[Harry/FDK]

F+".K, couldn't the whole world be Inch OR Metric. (Excuse my french).

no kidding! I often read euro duration figures and wonder WTF? You guys measure @ mm?
or ?

Yep @ mm and to make things worse the germans calculate/index the lobe centers differently.
Jim you got PM.
Bye,
Harry

[SlingShot]

The K8 is even a hotter cam than K7.
If you need good torque all around, then stock cam with ratio rockers or Web 218 or Engle 100
The VZ14 would intrigue me too.... but be prepared for worn out stuff.
[/quote]

I run a VZ15 in my 1600 STF motor, pretty noisy, has a cool camy idle too. I know the clock is ticking on my lifter bores, will see how many miles I can rack up on it.

[Jim Ratto]

The K8 is even a hotter cam than K7.
If you need good torque all around, then stock cam with ratio rockers or Web 218 or Engle 100
The VZ14 would intrigue me too.... but be prepared for worn out stuff.

I run a VZ15 in my 1600 STF motor, pretty noisy, has a cool camy idle too. I know the clock is ticking on my lifter bores, will see how many miles I can rack up on it.
[/quote]

in the 90's Buggy House built a 1915 for a customer running CB 044 (out of box) and VZ15. The motor ate an exhaust valve one day. We kind of knew it was coming I guess, Jerry said the exhaust valves were tight every time the car came in for service. 
We put new heads and p/c and rebuilt bottom end, still with VZ15 and installed 1-5/8" header and the heat trouble and tight valves vanished.
It ran really really hard, and surprisingly, was "cammy"
I do like that cam. I know they get a bad rap, but the VZ15 gets rpms NOW

[NEWK]

Hey Jim!  Sorry for a small hijack/sidetrack.  I seen you talking about cams and had a deja'vu from the old CLF days.  I remember talking about cams/springs with you back then.  Good to see your still around...   

Jeff 

[Tony Wilkie]

What about this combo.

88x94 Street engine in a split bus.
Any recomdations?
I was going to use in my street car with comp heads and turbo with a fk-89.
Now installing 044's 40x37.5 and was thinking about keeping the fk-89 but also thinking changing to a k-8.

My last bus I ran my little 78x94 with the fk-89 & comp heads. It was streetable but really came on hard at 5k  And dyno'd at 207hp.

tw

[Tony Wilkie]

By the way...I always ran vz cams in my 5/1600 & 2/1600 score legal race engines.

tw