split duration cam

Eurolook71 · Post by **Eurolook71** » Sat Mar 27, 2004 4:02 pm

I'm building up a 1600, and since I'm buying a new cam anyways, I'm curious what the advantages are of the split duration cams. At acnet, they are only $10 more than a regular cam, so I figure it would be worth it. Any comments? Oh, and I'm staying with the 1584cc, since i already have the crank, pistons and cylinders, thats why I'm making this cam a possible option. thanks.

Sharkey · Post by **Sharkey** » Sat Mar 27, 2004 6:43 pm

Eurolook71 wrote:I'm building up a 1600, and since I'm buying a new cam anyways, I'm curious what the advantages are of the split duration cams. At acnet, they are only $10 more than a regular cam, so I figure it would be worth it. Any comments? Oh, and I'm staying with the 1584cc, since i already have the crank, pistons and cylinders, thats why I'm making this cam a possible option. thanks.

Split duration cams are no better or worse than standard cams in the most general sense of the term, so it doesn't follow that the extra costs would "be worth it". The extra cost is more than likely extra labour time to make the cam.

Split duration camshafts have intake valve durations and exhaust valve durations that are not the same. Some particular engines run better with more intake duration than exhaust, while some work better the other way around. Simply dropping a split duration camshaft into an engine without knowing what the other components are or what the final purpose of the engine will be is no guarantee of success.

You have two choices at this point: accept the wisdom of others that have built dozens of engines with dozens of camshafts (not me) and use what they suggest for your particular engine/purpose, or buy books on camshaft design and read, read, read (and even then, you'll want the advice of those wise guys I mentioned above).

Camshafts are really the soul of an engine. I don't think I can say it any other way. For your engine, you probably can't go wrong with an Engle W-100. Anything more radical than that and you'll lose more than you'll gain.

Searoy · Post by **Searoy** » Sat Mar 27, 2004 9:39 pm

Split duration cams serve a specific purpose for a specific situation. Unless you have a specific reason to require a split duration, as in you are doing something off the wall, a standard cam will work better for you.

If you are doing a stock or near stock engine, then split duration would not necessarily do you any good.

Choose a mild performance cam. There are tons.

Dizzy · Post by **Dizzy** » Mon Mar 29, 2004 8:03 am

i have an engle 100 cam in my 1600 dp dual baby dellorto motor in my bus and i love it. it pulls pretty good and idles great. definately a step up from stock.

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Mon Mar 29, 2004 9:42 am

95% of the cams I use are split duration. This goes for Type I and TIV engines both.

I have never made as big of dyno numbers with straight pattern cams as I have with split duration. The engines have a great midrange, awesome torque and really like compression...

Sharkey · Post by **Sharkey** » Mon Mar 29, 2004 6:39 pm

MASSIVE TYPE IV wrote:95% of the cams I use are split duration. This goes for Type I and TIV engines both.

So which combinations have you tried? Most split duration cams feature longer intakes than exhausts. Any thoughts on running vice versa?

Honda's Killer · Post by **Honda's Killer** » Tue Mar 30, 2004 10:36 am

Bob Tomlinson swears by them.

BTW, CB doesnt post here?

PS. I just checked my "Lifter rotation" last night(from VW Trends)
OMG they do spin. I had no idea. Makes sence

Eurolook71 · Post by **Eurolook71** » Tue Mar 30, 2004 11:56 pm

Sharkey wrote:
Eurolook71 wrote:I'm building up a 1600, and since I'm buying a new cam anyways, I'm curious what the advantages are of the split duration cams. At acnet, they are only $10 more than a regular cam, so I figure it would be worth it. Any comments? Oh, and I'm staying with the 1584cc, since i already have the crank, pistons and cylinders, thats why I'm making this cam a possible option. thanks.
Split duration cams are no better or worse than standard cams in the most general sense of the term, so it doesn't follow that the extra costs would "be worth it". The extra cost is more than likely extra labour time to make the cam.

Split duration camshafts have intake valve durations and exhaust valve durations that are not the same. Some particular engines run better with more intake duration than exhaust, while some work better the other way around. Simply dropping a split duration camshaft into an engine without knowing what the other components are or what the final purpose of the engine will be is no guarantee of success.

You have two choices at this point: accept the wisdom of others that have built dozens of engines with dozens of camshafts (not me) and use what they suggest for your particular engine/purpose, or buy books on camshaft design and read, read, read (and even then, you'll want the advice of those wise guys I mentioned above).

Camshafts are really the soul of an engine. I don't think I can say it any other way. For your engine, you probably can't go wrong with an Engle W-100. Anything more radical than that and you'll lose more than you'll gain.

I've had a previous 1600 that ran pretty good and it had a W-100, this time I think I'll try the web cam variation (119 i think??) I need this badboy to be running by yesterday, but I keep coming up with ideas to try and make this first build up a work horse. Any way, from what it sounds like, I should save the split cam for that 2.2L T4 someday....
doing the custom length pushrods for a 1.6 really doesnt seem worth it, since it's not a track car or anything.

Also...the heads are getting a 3-way valve job, SCAT HD single lifters, SCAT chromo retainers, HD keepers. Going to keep the stock valves, (is this ok??) Using SCAT HD shafts, 1.1:1 rockers, and I need help with a selection of adjusters....do I go stock? what are the real benefits of porsche style adjusters, they're really expensive...

OK, one more...I'm gonna go the head work on my own, just a real mild port/polish, and de-burr... but need some info on it. Could you guys lead me to sites that give basic techniques, kinds of stones to use, etc, etc...

Thanks alot!![/img]

Sharkey · Post by **Sharkey** » Wed Mar 31, 2004 8:09 am

Eurolook71 wrote:OK, one more...I'm gonna go the head work on my own, just a real mild port/polish, and de-burr... but need some info on it. Could you guys lead me to sites that give basic techniques, kinds of stones to use, etc, etc...

If all you're going to do is what you said (de-burr, mild porting, etc.), you should be ok. The moment you go beyond simple de-burring and polishing, you run a risk of losing performance instead of gaining it. The likelihood against this happening is based primarily on familiarity with the ACVW cylinder head. The real gurus in the field don't reveal their secrets.

An excellent "in print" source for porting and polishing can be found at your local V8 Speed Shop and perhaps even in a used book store. Any of the Motorbooks International Series of books (eg: "How to Build & Modify Chevrolet Small-Block V8 Cylinder Heads" by David Vizard) will be of great help to you, even though they concentrate on the V8 engine. Theory is still theory, at least as far as a newbie is concerned. I wouldn't attempt to perform any more drastic porting unless you have some scrap cylinder heads to practice on, and preferably a home-made flow bench to test your results.

Guest · Post by **Guest** » Fri Apr 02, 2004 12:08 am

scrap heads???
thats exactly right...I have some lined up to practice on.

And a homemade flow bench...got any links on the how-to????

Thanks for the help.

volksbugly · Post by **volksbugly** » Mon Dec 02, 2019 2:30 pm

Here is what my split duration 2109 sounds like.

Also all the videos I have up right now 12/2 and older are on low boost 7 lbs. I'm now on 12lbs but I am running out out of fuel soonish. I need to get a higher psi unit. So I stopped tuning on it for now.

Ol'fogasaurus · Post by **Ol'fogasaurus** » Mon Dec 02, 2019 4:23 pm

Split duration cam shafts work well in some motors but not as well in other motors but I am not sure exactually why.

https://www.bing.com/search?q=split+dur ... lang=en-US

If I remember correctly the intake is angled to open up sooner than normal and the exhaust opens up later than usual. It is supposed to help with airflow in cooling and scavenging as I remember. I don't remember ever hearing about an ACVW motor using one but I did a quick search and:

https://www.thesamba.com/vw/forum/viewt ... p?t=217266

If you do a search on specifically on split duration camshafts for ACCVW engines the first post (from TOS) I got the initial post talked about dual lobed camshafts then the conversation got into split duration camshafts but at one time there were double lobed camshafts, they were called 1/4 speed cams as the cam gear rotated the cam at a 1/4 speed rather than the 1/2 speed as normal. I guess they worked OK but their use faded out and I haven't heard anyone talking about them for a while.

https://www.bing.com/search?q=quarter+s ... lang=en-US

Lee

woodsbuggy1 · Post by **woodsbuggy1** » Mon Dec 02, 2019 6:00 pm

Interesting to see this brought up, it is funny how people forget that VW factory camshaft is split duration and also has different lift on intake and exhaust. I am sure there are advantages to it but it is so easy to just order a single pattern camshaft that seems to work quite well, unless you have the the resources to test various combinations that best fit your goals.
Kenric

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