Adjusting Valve Lash Order?

[bingham72]

Ok, I started to adjust the valve lash on my SBC engine, but somehow I think I have the sequence wrong. I thought you set zero lash at TDC of the cylinder. However, I did 1,8,4 and then doing 3 noticed 1 was WAY loose. What is the proper sequence?
With any luck, I'll be disturbing the neighbors with a new CAM tomorrow.

Thanks in advance...

[Tom Welch]

I adjust the valvetrain on my Pontiac using the base circle of the cam as a guide to tighten the rocker arm nuts, go until the pushrod gets stiff when twisting it back and forth. set it there, adjust again after running until valvetrain is quiet.

[bingham72]

I adjust the valvetrain on my Pontiac using the base circle of the cam as a guide to tighten the rocker arm nuts, go until the pushrod gets stiff when twisting it back and forth. set it there, adjust again after running until valvetrain is quiet.

I get that part. I'm just trying to figure out at which position (i.e. TDC #1) to adjust that cylinder. Is it correct that when #1 is in firing position, the lifters are on the base circle?

[fishtail8]

Bring the engine around by hand until the exhaust valve on #2 just starts to open. I'm talking just moves a little. Then set lash in #1, spin the push rod gently in your fingers tightening the nut till you feel a bit of resistance, then add an eighth of a turn. Roll the engine over till #1 exhaust valve just opens. Set lash on #8. Continue this way through the firing order 1-8-4-3-6-5-7-2. If there's still a bit of tick when the engine's warm, give em a little bit more. Done dozen's of SBC's this way...

[bingham72]

Cool. Thanks! Got that. I figured out I was 360 degrees off. I had forgotten that I had rotated the engine to tighten the cam bolts once more before buttoning up the timing chain cover.

Ok, second question. How critical is the alignment on roller tip rockers? I noticed a couple are not exactly centered on the valves. I had to adjust the guide plates so the pushrods would clear the runners a little more. How much clearance should be between the pushrods and intake runners?



Moderators... I guess you can move this. I'm done for the day.

[MrQuick]

Ok, second question. How critical is the alignment on roller tip rockers? I noticed a couple are not exactly centered on the valves. How much clearance should be between the pushrods and intake runners?

The length of the push rod will determine the valve stem/tip position. There should be an air gap at the intake.

[Pro Stock]

The rockers do not need to be exactly centered on the tip of the valve, they can be off center as much as .030, push rod clearance at the intake port can be a little as .010. Push rod length determines geometry, the Comp Cams catologe explains this in detail if you suspect a problem there.

Dale