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martyrg
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Joined: February 29, 2004
Posts: 492
Location: South Lyon, MI. 48178
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 Posted: Sat Sep 12, 2020 7:18 pm Post subject: Camshaft Knowledge |
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I just want to check and see if what I think I know about camshaft selection is in the ball park.
The more duration a cam has, say above 300 degrees advertised duration, the higher in the RPM band it will make power. These cams are intended more for racing. A cam with more lift, say 0.500" and less duration, say under 300 degrees is more streetable and makes its power at lower RPM's. Cams with high lift tend to be "rampy" and are harder on the valve train.
Using duration measured at 0.050" what is considered at long duration cam? |
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Danwvw
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Joined: July 31, 2012
Posts: 8895
Location: Oregon Coast
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| Posted: Sat Sep 12, 2020 8:51 pm Post subject: Re: Camshaft Knowledge |
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I have my cam conspiracy theories too. I suppose it depends on more than lift and duration. it depends on cam timing too. The right choice for a cam needs to include how rough the cam will be on the valve train and that the valve train is made to handle a given cam. Also Heads Valve Sizes and head work needs to match the cam there is a lot to it way more than I know.
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1960 Beetle And 1679cc DP W-100 & Dual Zeniths! |
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anthax
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Location: Hälsingland, Sweden
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Danwvw
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Joined: July 31, 2012
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Location: Oregon Coast
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| Posted: Mon Sep 14, 2020 2:27 pm Post subject: Re: Camshaft Knowledge |
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Cams also need to match the engines compression ratio. Exhaust valves need to open sooner on higher compression engines. A good all around performance cam would be the Web-Cam 163. It works well with stock heads and dual carbs stock rockers etc... It's good to run Single HD valve springs with it. Light Weight lifters and Aluminum racing pushrods are always a good idea too.
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1960 Beetle And 1679cc DP W-100 & Dual Zeniths! |
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mark tucker
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Joined: April 08, 2009
Posts: 23950
Location: SHALIMAR ,FLORIDA
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| Posted: Mon Sep 14, 2020 2:50 pm Post subject: Re: Camshaft Knowledge |
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different cams for different people. what many might think is a wild race only cam is what some may consider a small street cam. I put one of those 163's in a guys motor I did for him by his choice by reading exspurt's toutings...I presonaly would not have one in any engine of mine...not even on the shelf. but I dont mind somebody else using it. IMHO cams should match the driver& driving style& vehicle to be used in. CC , CR & such.  |
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bugguy1967
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Joined: January 16, 2008
Posts: 4368
Location: Los Angeles, CA 90016
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| Posted: Mon Sep 14, 2020 3:22 pm Post subject: Re: Camshaft Knowledge |
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As cam profiles improve, materials and processing becomes more refined, spring quality improves, and pushrods get stronger, the rules of thumb become less and less relevant.
For the most part, you’ll be really safe if going with your suggestions. But even that alone can still get you in trouble. Look at the VZ series of cams. Low duration, under .500” lift, but will wreck guides or lifter bores in no time. Then let’s look at the FK8 and FK10. Both lift well over .500” and have plenty of duration. Still, they’re soft, gentle profiles that can see over 100,000 miles in the right engine.
Some important longevity factors:
Whether the springs can handle the profile and mass of the valvetrain
Spring pressure
Valvetrain rigidity
Duration is a good thing as lift goes up. It allows the designer to regulate valve acceleration.
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"A petrol engine can start readily, run smoothly and give every appearance of being in good order, without necessarily being in good tune." - Colin Campbell, "The Sportscar Engine" |
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Rome
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Joined: June 02, 2004
Posts: 10524
Location: Pearl River, NY
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| Posted: Mon Sep 14, 2020 5:27 pm Post subject: Re: Camshaft Knowledge |
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| Quote: |
| Then let’s look at the FK8 and FK10 |
My first several years of building my own engines from the late '80's thru the mid '90's would be considered as "luke warm"- mostly stock displacement 1600, a 1641, and even a 1776. Cams were Engle 100, 110, or the equivalent Scat C25 and C35. Dual carbs, starting with Kadrons and then dual-throats. I read many of GeneBerg's tech articles and his parts catalog. In 1996 I drove out to the inaugural GeneBerg Memorial Cruise in Michigan, where several participants came out from the West with their strong 2+ liter engines. At the host hotel, Matt J from Lincoln, NE had a maroon oval window Beetle with a 2-liter engine that he built himself using mostly Berg parts. He had built numerous engines, drove them hard but they held up. His cam was an FK-8. I already knew Matt from a few years before, but I regarded this engine as quite hi-po. I always remember what he told me- "nah, it's really a grandma cam!". Smooth running, but can downshift on highway at 3000 rpm and it'll pull to whatever- 6500 if the rest of the engine parts are suitable. |
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martyrg
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Joined: February 29, 2004
Posts: 492
Location: South Lyon, MI. 48178
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| Posted: Mon Sep 14, 2020 7:44 pm Post subject: Re: Camshaft Knowledge |
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Thanks for the replies, keep 'em coming! I did watch the YouTube videos from Moss Motors (https://www.youtube.com/watch?v=bnfdYc2GAz0&list=bleep) - very helpful, especially explaining the key role overlap plays.
Are most of the popular cams out there (Engal FK 8 & FK 10, Web 86 A, B, & C W110 & W120) more or less the same when it comes to valve overlap?
How big of a difference does it make from one cam to another? |
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Danwvw
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Location: Oregon Coast
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Dan Ruddock
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Joined: October 25, 2012
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Location: Sarasota, in my adopted state of Florida
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| Posted: Tue Sep 15, 2020 7:15 am Post subject: Re: Camshaft Knowledge |
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| martyrg wrote: |
Thanks for the replies, keep 'em coming! I did watch the YouTube videos from Moss Motors (https://www.youtube.com/watch?v=bnfdYc2GAz0&list=bleep) - very helpful, especially explaining the key role overlap plays.
Are most of the popular cams out there (Engal FK 8 & FK 10, Web 86 A, B, & C W110 & W120) more or less the same when it comes to valve overlap?
How big of a difference does it make from one cam to another? |
Two things will increase overlap. One, with all other specs equal is more duration equals more overlap.
Two, less lobe separation increases overlap without changing duration. In most cases I like to Keep the standard 108 degrees of lobe separation. You can move the power band up or down by changing the lobe separation but I like using using duration to do that instead. If you have to change lobe centers to get the engine to run the way you want maybe you have the wrong cam.
I like to use duration @.050" to evaluate cams for apples to apples reasons. Most cam grinders will come up with their own method to create advertised duration which is apples to oranges. 260 @.050" is starting point for long duration cams for VW engines.
For a stock VW engine the best cam is the stock VW cam for many reasons. Adding ratio rockers to a stock engine is not a bad idea and it will add some power. Some people like cheater cams for a stock engine but that is a mixed bag if it is poorly designed.
Choosing a cam for a performance engine there is a whole list of factors that need to be taken into account. Just a few are, car weight, gearing, displacement, carburation, head work and what type of heads and what will the engine be used for and what are your preferences.
This glossary is a good start for increasing cam knowledge.
Dan
http://www.webcamshafts.com/pages_misc/cam_glossary.html
http://www.webcamshafts.com/pages_misc/degreeing.html |
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GARRICK.CLARK
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Joined: June 30, 2012
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Location: Lancashire UK
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| Posted: Tue Sep 15, 2020 8:49 am Post subject: Re: Camshaft Knowledge |
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| I'm looking for a type 4 turbo cam with more than a 112 lobe Centre, doubt it exists though. The 86a with a 108 is bleeding too much boost/fuel out the exhaust causing me problems. |
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Dan Ruddock
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Joined: October 25, 2012
Posts: 3668
Location: Sarasota, in my adopted state of Florida
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| Posted: Tue Sep 15, 2020 9:02 am Post subject: Re: Camshaft Knowledge |
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| GARRICK.CLARK wrote: |
| I'm looking for a type 4 turbo cam with more than a 112 lobe Centre, doubt it exists though. The 86a with a 108 is bleeding too much boost/fuel out the exhaust causing me problems. |
Going more that 112 will have downsides, it will increase turbo lag because of the latter intake closure. The engine will be lazy off boost. I do agree 108 in most cases is too narrow for turbos. I can supply a 86a will 110 or 112 lobe centers. Dan |
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