Thread: tuning and timing questions???

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You guys are awsome...I did a search and found this thread.

After reading the entire thing i realized this is the place to get answers. I have a similar set up and problems with my bored 60 over 283. Edelbrock 600 electric choke out of the box. Edelbrocks 400 cam 214/214 @. 050 .442/.442 lift. Here is the kicker.....Summit roller tip alluminum rockers 1.6 ratio. I have no idea what this is doing to the valve train......DOES ANYBODY FEEL LIKE TAKING A STAB AT IT???

waste of money on the roller tip rockers. from what just happened to me, i just bought a set of stamped steel rockers for my 400+ hp small block build.

you should be fine with them tho, do you kick the $h!t outta it or not?

It has very little miles. Maybe 1500 or so...It screams!

I am trying to get my throttle response where it should be. I'm where you were. Can't wait to get it right. Great motor though I love the fact that it is so old.

Originally Posted by espo1980

You guys are awsome...I did a search and found this thread.

After reading the entire thing i realized this is the place to get answers. I have a similar set up and problems with my bored 60 over 283. Edelbrock 600 electric choke out of the box. Edelbrocks 400 cam 214/214 @. 050 .442/.442 lift. Here is the kicker.....Summit roller tip alluminum rockers 1.6 ratio. I have no idea what this is doing to the valve train......DOES ANYBODY FEEL LIKE TAKING A STAB AT IT???

If the cam lift is 0.2946" at the lobe, then theoretical valve lift with 1.6 ratio rockers will be 0.471", bringing the valve heads closer to the piston crown during the overlap period. Depending on piston crown configuration, piston deck height, gasket thickness, whether or not the heads have been shaved and how far the valves are sunk on the seats, you may want to run through the operation of checking valve to piston clearance, either with the clay on the piston crown method or the light checking spring and dial indicator method.

As far as whether your valve train geometry is gonna work out or not, read this answer I posted for another board member.....

Sean, I think what Pat was sayin' is that the checker you're using might work differently rocker to rocker, as he has gotten different results using using it and prefers not to use it any longer. Apparently he uses the same method most of us use and that is to verify that the rocker tip travels through its arc making the shortest possible trip across the valve tip and the extremes to the intake side and the exhaust side are equal.

The rocker changes its effective ratio as it swings through its arc. The ideal setup would be: Starting off at zero lift with the rocker tip on the intake manifold side of the valve, then moving to the exhaust manifold side of the valve at mid-lift, then coming back to the intake side of the valve at full lift. On the return trip to zero lift, the roller would cross the center of the valve tip and go to the exhaust side of the motor at mid-lift, then back to the intake side of the motor with the valve back on its seat. In this way, the rocker would be at its longest effective length halfway through the lifting of the valve. Its effective length would be shorter at both zero and full lift.

Whether you're using an adjustable checking pushrod or a pushrod that you think might work correctly, de-grease the valve stem tip and color it with a black Sharpie pen. Then, install the pushrod and rocker arm while the lifter is on the base circle of the cam. With hydraulic lifters, jiggle the pushrod up and down while tightening the adjusting nut until all play is removed. Twisting the pushrod with your finger and thumb will not work. You'll be compressing the spring and not even know it. Jiggle the pushrod up and down to remove play. With all play removed, tighten down the rocker adjusting nut to your normal preload. Using a socket on the damper retainer bolt head at the front of the crankshaft and long bar for leverage, turn the motor over several times clockwise. Obviously this is more easily done if the spark plugs are out of the heads. Remove the rocker and check the mark left on the valve tip. The roller tip on the rocker should leave a shiny spot in the center of the valve tip where it wore away the ink you put on the valve tip. The width of the shiny area will tell you the intake side to exhaust side extremes of travel of the rocker tip across the valve tip. Measure this width with your dial caliper and record it in your toolbox notebook.

If the pushrod length is correct, this mark should be centered across the valve stem. If it's too high (closer to the intake manifold), try a slightly longer pushrod. If it's too low (closer to the exhaust manifold), try a slightly shorter pushrod. This method works well when using an adjustable checking pushrod.

Every time i take it out I blast it up to 7000rpm or so. So far so good with the new build up.

With so many variables in tuning a motor, I have not had it performing at 100% yet. Need to nail down timing, Initial timing, curve, vacuum, carb jeting, idle , and so on. I've been doing my homework though... and with this forum i think I'll get her tuned right for good.. Would like to here more about how your 283 runs. Power band details. How it Idles and sounds. Where the redline is and so on.....Those sort of things. I realy have nothing to compair to. They would help.

Once it tuned perfectly I want to introduce nos into the picture. HeHe

Techinspector,

I have been running this set up without it being tuned. It has worried me though the plugs look ok and for the most part it sounds great. I did not relize how different building a 283 compaired to a 350.

I did check the clearence when I put it together. The question I'm wondering about now is the cam set up and the 1.6 rockers to much for the little 283? Keeping in mind it is bored 60 over.

Must sleep tonight...be back tomorrow.....