Setting up the Valvetrain

Wednesday, 08-Nov-00 12:23:20

216.189.45.86 writes:

How does everyone set up their valvetrain? By this I mean rocker arm geometry, cutting pushrods, etc. I read the Hot VW's article on the

Dyno Motor and they seem to check everything to the N'th degree, using dial indicators, jigs, etc. I've also been told that was overkill; that

as long as the rocker geometry is correct on the valves everything is OK. Does everyone measure each rocker for actual lift? Do you match

a particular rocker to a particular cam lobe? Just how nit-picky do you get? Does spending days blueprinting this stuff gain horsepower?

Add engine life? What about pushrods? Do you cut each one for a particular valve, or do you cut them all the same and use the adjusters to

get the final set-up?

How far would you go for a hot street engine?

scott s

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Replies:

Most blueprinting has to do with clearances and making sure things are straight/true (crank, rods). All rockers within one set should be fairly close to each other, and the lifter "heights"

(lobe contact base to pushrod contact area) shoud be about the same. Just dial in one pushrod to get the correct length, then match the others to it. (n/t) (george brown) (08-Nov-00

13:08:47)

Re: Setting up the Valvetrain (Loïc CHARPENTIER) (08-Nov-00 14:38:21)

Re: I'd check it all, but that's me. If it's a street motor, some guys put it together, and as long as nothing interferes, they run it! I'm usually not that lucky!... (Tom Simon) (08-Nov-00

16:13:06)

The idea is to have the center of the rocker shaft exactly perpendicular to the head of the valve at 50% lift. Tough to see with lots of curvey things in the way and valves that are at an

angle. Use a straight edge to help visualize it. Shim rockers shafts to get it right then cut pushrods to fit.... (n/t) (Ohio Tom) (08-Nov-00 21:58:06)

Forgot to mention that if your valve stem heights vary by much you can "customize" a set of lash caps to get them all the same. (n/t) (george brown) (09-Nov-00 16:50:44)

It Depends on if you are running Stock Rockers or Pad-type High Ratio Rockers (Jim Ratto) (09-Nov-00 17:14:05)

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A correct valve geometry is one of the most important job when you blueprint an engine especially with a hi-lift cam: Less wear on the

entire valve train, less guide and spring heat and more power!

The biggest problem is the most of aftermarket hi-lift rokers set haven't the same ratio (unless the factory ones). the best solution for me is

to use the 4 highest ratio on the intake valves.

Loïc CHARPENTIER

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I would ask myself a couple of questions. What's the worst that can happen? If the answer is ruin a set of custom Wiesco pistons, Manley

vavles and Manton double tapered cromoly pushrods, then check everthing! If it's maybe hurt $75 worth of used stuff, and can afford to take

a chance, heck, go for it. Am I willing to go back and redo the valve train if I have a problem? I personally don't like doing things over, but

thats a personal deal. What is the engine? The further away from stock you get, the more "blueprinting" and machinework is required to

make the whole system work. At an absolute minimum, for hot street, I would "clay" the pistons to check valve-to-piston clearence, make

sure the rocker pad isn't riding off the edge of the valve, and if using a cam and heads that haven't been run together before, check for valve

spring coil bind and boss-to-retainer clearence. A lot of the "gnat's eyelash' measurements are for race motors going together. Good Luck!

Tom Simon

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For stock rockers: I dial indicate approx actual lift at the valve. Then I put light checking springs in the heads, bolt the rockers onto the head

with dial indicator on retainer. I dial up 1/2 of actual lift, and view how the swivel foot screw is contacting valve stem tip. At half lift, it

should share the same 'imaginary' centerline as the valve stem. This way, at NO lift, and at FULL lift, the adjusting screw is at a

symmetrical angle from the centerline. I set up the geometry once I know the deck height needed (i.e. which spacers are required/flycut of

heads....before assembling bottom end. There is a good reason for this). If the screw is not within the centerline at half lift, you may need to

shim rockers or use a lash cap. As George said, it is important to make sure your stem heights are equal. Once you have determined your

shim stack or lash cap height, then you can set up your pushrod length at TDC. Make sure your valve adj screw has ample travel for future

adjusting (don't screw it all the way in or out!). Using your dummy pushrod (and the light springs still!), open the pushrod until your

adjusting screw contacts valve stem. Then just adjust accordingly for your lash.

For high ratio rockers, I still dial up approx full lift (be careful with high ratios, because sometimes they can throw your 'mathematical'

figuring out the window, so try to be as exact as possible), then install light springs, open rockers up on head (with dial indicator) to 1/2

lift. Check to see if the arc of the rocker pad is 'cresting' on the center of the lash cap. You may have to shim or use different lash caps to

achieve this. Then check at NO lift and at FULL lift to see if the contact area of the rocker pad mirrors itself in each of these positions. I

have noticed that at 1/2 lift on my rockers, when the arc is centered on lash cap, that also the adjusting screw (on pushrod side) is following

the same centerline as the pushrod, so I use this as a guage too to check. Then determine pushrod length as stated above.

Be sure your adjusting screws are NOT screwed in too far when you set this up, or you will find that they will break at high rpm use. I like

to see 2-3 threads above jam nut on my stuff.

Hope this helps. I have done it this way for a decade on countless engines, never with a problem.

Jim Ratto

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Coil Bind Checking

Tuesday, 14-Nov-00 20:07:44

206.28.203.160 writes:

I've used feeler gauges with everything assembled but am not comfortable with the measurements.

Is there a better way to check?

Thanks,

Don Jiskra

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Re: The way I do it

Tuesday, 14-Nov-00 20:39:49

128.115.225.110 writes:

I start by checking 3 or 4 springs from the set to ensure they are all the same, by putting them, loose, in a drill press, and compress the

spring until it bottoms out. I measure this coil bind heigth with a dial caliper. Then, assemble the lower end and one head with a "check

spring" in place of the regular springs. At maximum lift, I measure the distance between the retainer and the spring seat pocket bottom(in the

head), also with a set of dial calipers. Subtract this number from the spring coil bind number, and you have the clearence, or distance from

coil bind.

The other way to do it, on an already assembled engine, is to set up a 0-1" travel dial (dial indicator) on the top of the retainer. Spin the

engine over and measure the total valve lift. Now, crank down on the adjuster, as to open the valve, say .100". SLOWLY spin the engine

over, by hand, and check for interference. Don't force it. The problem with this second method is if you DO have interference, you still don't

know if it's valve-to-piston or coil bind. This is hard to explain via text, and I'm sure someone knowlegable could walk you through it in

person. Good luck!

Tom Simon

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cutting push rods, and setting geometry...need help. Wednesday, 03-Jan-01 09:14:01 216.126.165.175 writes: Hey Gang, I am just about to start setting up my rocker arm geometry, and want to make sure I am doing this right. I already have an adjustable push rod , and if I remember correctly I have to set it up so the tip of the rocker is centered over the valve at half lift. Is this correct? (what is best way to get half lift? Just measure the total lift on a valve with my dial indicator? ...intake? or exhaust valve?....and then divide by 2? Or should I do it another way?) Then once I get the adjustable one set to the right length, I can go about cutting my own. (Bugpack) Correct? I work at a small mold making shop, so I have access to grinders and such, so cutting them to length is not a problem...just setting up the geometry is a bit confusing. Is there a website that deals with this? Any help and / or advice you guys can give would be greatly appreciated. BTW I am using 1.4 ratio rockers, web cam 86b, and its going on a 2276 (if that matters) Thanks again Jay Boudreau Jay Boudreau

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Re: what you do is take a dial indicator and put it on your retainer so it wont move sideways and such as the valve travels up and down,then you find your total valve lift and spin your engine once around to verify the total lift,you get the total that you got and devide by half spin your engine to that amount at that point either your adjusting screw should be in line with your valve or in your case using 1.4 rockers your adjusting screw being in the bottem should aling with your pushrod if it doesnt adjust your adjustable pusrod until it does mind you might have to shim your rockers a bit,good luck. (n/t) (lazaro ) (03-Jan-01 12:19:23)

More importantly, The rocker should be perpendicular (90deg) to the valve stem at 50% lift. This minimizes "scrubbing" the valve stem sideways and reduces guide and stem wear. This is a tought one to visualize as some ratio rockers are curved in shape. A straight edge set on top of the valve stem at 50%lift should pass through the center line of the rocker shaft... (n/t) (Ohio Tom) (03-Jan-01 18:58:33)

How is it you guys can turn the engine over with an adjustable push rod? I did that once many years ago with some regular dual springs and bent the threaded portion in half. Do you just use the dampner? (n/t) (Victor Hirth) (03-Jan-01 21:28:16)

They make a checking spring, or you can use any real light spring as long as it strong enough to hold the valve shut. You could just use a used stock spring. Remember to relube your cam and lifters when you get done. (n/t) ( James2) (03-Jan-01 22:00:48)

So it looks as if i can't use my adjustable pushrod to open the valve?! Do i have to go out and buy a special tool to remove one of my valve springs (dual springs)..or is there another way. I havent done this yet, but i will soon. i was waiting till i actually could put the engine in my buggy...because i have heard about the cam lube comming off if it sits to long. So far my short block has been together for almost 3 months, and the lube still looks like the day i put it on. I think i will assemble it for good soon, and install it in my buggy this spring. Thanks for all the help guys! (n/t) (Jay Boudreau) (04-Jan-01 18:40:31)