Mechanics of using 1.25 rocker arms

[dubhead74]

I was told by a VW parts supplier that installing 1.25 rocker arms on my stock heads and using the stock cam would make my cam shaft prefrom as if it was a aftermarket 110 cam.He tired to explain over the phone how this would work but I didnt understand how it would do so.
Could someone please explain it to me so I can read it for a better understanding?Thank you
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1974 Standard Type 1
"She may not look like much, but she's got it where it counts....."Han Solo

[krusher]

the stock cam has .334 valve lift (in the intakes) .334x 1.25 = 4.18

engle 100 has .392 if your just using the stock 1.1 rocker with it .392 x1.1 = 4.3

so the valve lift with be almost equal. (but actually the engine 100 is .420 lift so more the equal of the stock cam with 1.25 rocker)

however and here is the big how ever, the stock cam has 214° duration (time valve is open) This will be slightly lengthened by the 1.25 rockers So lets call it 220°

the engle 110 has 247° so there is your significant difference

So a stock cam with 1.25 rockers does not = a engine 110 with 1.1's it does not even = a engle 100.

if people cold just get a engine to think it had a engine 110 by putting 1.25's on there stocker no one would be buying 110's
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(06:31:07) RoachGhia: "i drink dick way too fast"

[vwracerdave]

[dubhead74]

Thank you..... Krusher that helps and makes a ton of sense
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1974 Standard Type 1
"She may not look like much, but she's got it where it counts....."Han Solo

[spencerfvee]

right on vw racer dave . you allso for got to tell him that a stock cam is not ground to use high lift rockers of any kind . i know i am going to catch hell for saying that lol but its true and yes guys will tell you it works great use a cam thats made to use high lift rockers . allso there are some real cheap junk 1.25 rockers being sold. if you must use 1.25 buy good ones . to me you wont feal any more power . buying the 1.25 rockers . just my two cents spencerfvee

[krusher]

Would you like to name the "parts supplier" that tried to sell you this idea?
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(06:31:07) RoachGhia: "i drink dick way too fast"

[Bruce]

[JasonBaker]

[Bruce]

[JasonBaker]

[mark tucker]

I dont think the stock cam cares what rocker you use on it, the rocker changes nothing the cam is doing, just after the end of the pushrod to the valve.and the oe cams are deburred&champherd correctly whtch I havent seen on any aftermarket cams, thus I do it my self so the cam dont eat it lifter lunch.

[ALB]

When the cam/rocker combo is already providing all the lift the heads need, Dave is right (and this is what he is referring to). A good example is stock heads with an Engle W100 or W110; either cam with 1.1 rockers will give about .420-.430" valve lift, and since stock heads don't really flow any more past .400" there is very little to be gained by adding 1.25's and increasing the lift another .060". Take those heads and port them, and now you have a different scenario; the intake ports will increase in flow and level off at about 1/2" valve lift and that extra .060" is needed to make the heads perform to their potential. NOT using 1.25's is leaving power on the table. Going from 1.1's to 1.25's also increases the duration as measured at .050" valve lift; 4-5 degrees in some cases (Engle W125, noted by John Maher in this thread- http://cal-look.no/lounge/index.php/topic,13225.0.html look for the graph 2/3 down the page).


As Krusher's numbers tell, this is why adding 1.4's to a stock cammed motor (with added carburetion and exhaust) works- the added lift now uses all the flow the heads can give. Adding 1.25's instead will also make a difference, though not enough to really be noticeable, and since the rockers will cost the same (or close) the higher ratio is the best choice here. The dur @ 0.050" will increase (7? 8? 10? degrees), but since VW was so conservative with their cam timing (214' @ 0.050") this is nothing to worry about.

As usual, just my 2 1/2 cents (I'm Canadian, eh). Al
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On a lifelong mission to prove (much to my wife's dismay) that Immaturity is Forever!!

[mark tucker]

correct in the added lift wont help much if the heads are already at thier max, but having the valve open longer will and thats what your doing.porting will help, but biger valves unshrouded and ported corectly will help morebetter, and a bit more cr helps too in most all cases.this is a never ending thing till you sell it& get a toyodie so you can race garfield and get to the speggettiiee first for a change.