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Valve adjustment for dummies?

General engine tech -- Drag Racing to Circle Track

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speedphreake
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Valve adjustment for dummies?

Post by speedphreake »

Can someone give me a detailed simple way to adjust valves correctly? How far should the exhaust be open or how far from closed should the intake be? Seems the harder I try to get it right, the worse I seem to do.
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Re: Valve adjustment for dummies?

Post by technicaltom »

http://www.youtube.com/watch?v=89o5rLpbCgI&feature=fvw ." Google is your friend ", Boxwrench Videos on YOU TUBE, are just one of the many excellent valve adjustment tutorials .Second thing here is that practice makes perfect, so spend some time and maybe get some friends to get involved .On this side of the pond us older mechanics used to use the rule of " 9 "when adjusting "tappets " as we describe the task , on 4 cylinder engines.The procedure was when number one valve closed then adjust valve number eight 1+8 = 9. Then number two closed ,adjust number seven , 2+7= 9 and so on.
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Re: Valve adjustment for dummies?

Post by ZIGGY »

What's happening? If your lash is walking around, it's not necessarily because of your adjustment technique.
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Re: Valve adjustment for dummies?

Post by Boz-Race Engines »

i do it like this: when exhaust is 1/4 the way open adjust the intake, when the intake is 3/4 closed adjust the exhaust. that way you are always on the base circle.
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Re: Valve adjustment for dummies?

Post by CamKing »

If you want the 100% full proof "valve adjustment for dummies", do each valve one at a time.
What ever valve you are on, turn the engine over until the valve is at max lift, then turn the engine over 360 degrees and set that valve.
This puts you dead center on the base circle, with zero chance of being on the clearance ramp.
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Re: Valve adjustment for dummies?

Post by F-BIRD'88 »

Boz-Race Engines wrote:i do it like this: when exhaust is 1/4 the way open adjust the intake, when the intake is 3/4 closed adjust the exhaust. that way you are always on the base circle.
Don't know where you got this method but it is sure to get a bad result.

Intake closes (just arrives on seat), set the exhaust....exhaust opens ( just begins to open), set the intake. Repeat as necessary.

Setting and locking the poly locks takes a bit of practice to get it right.
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Re: Valve adjustment for dummies?

Post by pdq67 »

Or do it the old messy way running at hot idle using either "the spin the p/r between your thumb and finger" method or using a pair of feeler gauges like the old Mechanics taught me way back when I was a pup!

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Re: Valve adjustment for dummies?

Post by MadBill »

Are you confused yet, speed? :)
The longer the 0.001" duration of the cam, the shorter the base circle and the more critical the cam's position when setting lash. if you sketch out the open/close events on a 720°-long event line, all will become clear. Short answer: If you want a no-brainer, perfect cam position every time, at the expense of a little more rotating of the engine, use CamKing's method. For any cam that I've encountered, setting the intake when the exhaust just starts to open and the exhaust when the intake just hits the seat does the job with a goodly number of degrees rotation tolerance. (besides, I find repeating the mantra: "Intake opening, exhaust closing." very soothing. OMMMM.... :D )

It would be very worthwhile at first to go through the sequence carefully, then without looking at the selected feelers, check for correct 'pull' on each valve a time or three and then see if you came up with the same clearance. (FWIW, a story going the rounds a few years ago was that at a Motorsports conference, a number of Pro builders were asked to lash an engine to 'X' & 'Y' cold lash, and the results were checked with a dial test indicator. Apparently the results varied by ~ +/- 0.005"... #-o
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Re: Valve adjustment for dummies?

Post by treyrags »

If you really want to get it right, do it like Mike suggested or use the "previous intake-next exhaust" method. For example on a SBC following the firing order: when #1 is TDC adjust previous intake of the firing order (#2) and the next exhaust of the firing order (#8). Turn 90* so that #8 is at TDC - prevoius intake is #1, next exhaust is #4 and so on ....
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Re: Valve adjustment for dummies?

Post by brket racer »

http://stevecoxracing.com
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Re: Valve adjustment for dummies?

Post by MadBill »

Err.. I'd condense the method F-BIRD and I described as: I.O.E.C.: Set the Intake as the exhaust Opens, set the Exhaust as the intake Closes.
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Re: Valve adjustment for dummies?

Post by speedphreake »

I've been using the IOEC method, but then I read somewhere the intake had to be partially open an a certain amount and exhaust not closed all the way. I'm going to go back to basics, then recheck it with camking's method. It's been awhile since I had to lash a motor and have had a hell of a time. Thanks.
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Re: Valve adjustment for dummies?

Post by rally »

Using firing order method, very simple. I do this with my race engine. #1 CYLINDER, on firing order. Adjust both valves, intake and exhaust, turn 90 degrees, adjust this cylinder, and so on.
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Re: Valve adjustment for dummies?

Post by Boz-Race Engines »

F-BIRD'88 wrote:
Boz-Race Engines wrote:i do it like this: when exhaust is 1/4 the way open adjust the intake, when the intake is 3/4 closed adjust the exhaust. that way you are always on the base circle.
Don't know where you got this method but it is sure to get a bad result.

Intake closes (just arrives on seat), set the exhaust....exhaust opens ( just begins to open), set the intake. Repeat as necessary.

Setting and locking the poly locks takes a bit of practice to get it right.
bullshit how do you work that out?? you obviously didnt read my post properly. have a look where the lifter is on the cam with my method. i will tell you! on the base circle thats where!. youve basicaly repeated what i said lol.
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Re: Valve adjustment for dummies?

Post by MadBill »

The difference between your methods, '1/4 lift' Vs. 'barely off/almost on the seat', is likely ~ 30° for a typical cam. For most cams the difference won't matter, but the 'barely' spec gives more latitude for positional error without getting tripped up by the beginning/end of a long slow ramp on a big cam.
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.
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