Valve train geometry problems

Started by Beck, March 05, 2018, 12:18:31 AM

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Beck

I am having some valve train geometry issues. I am a rookie at this. It has always been just "stick the stock length in" for me.

I am using stock rocker ratios. I have stud mounted Scorpion roller rockers going on a Trick Flow A460 head. For those unfamiliar, this is BBF stuff. Because of the raised deck of the heads, custom length push rods are needed. Intake and exhaust pushrods are different length.

My online research tells me to mark the center line from the rocker trunnion center to roller tip center. I did this with masking tape, straight edge and pen. Then I am supposed to make that line 90 deg to the valve at ½ lift. OK got that.

Then I'm instructed to mark the valve tip and rotate the motor to check where the roller sweeps over the valve.... BAD....  The roller is way at the outside of the valve. I needed to shorten the pushrods by .300" to get them near the center of the valve. When they are this length that 90 deg angle is off quite a bit.

What takes priority??

enjenjo

This is the method I use  
 I made up my own adjustable pushrod out of an old pushrod, a couple nuts, and some all thread. There are a number of places that will make the custom length pushrods for you.
Welcome to hell. Here's your accordion.

Beck

Thanks enjenjo,  I was trying to use a combination of that one and this one
.
Using this one the valve pattern wasn't right. I kept adjusting my home made adjustable pushrod length in .050" increments until I got an acceptable pattern on the valve stem.  

Another part I am unsure of is my compressed head gasket thickness. I am using a regular Victor Reinz head gasket. I believe these are about .040" compressed.

enjenjo

If it's a composition head gasket, you are pretty close,.041. If it's a MLS gasket it is thinner.
Welcome to hell. Here's your accordion.

chimp koose

There is some debate over the best sweep for a roller tip over the valve . One suggestion is to have the roller get to center of valve right at max lift , the thinking being that at max valve spring pressure it is all aligned and at its worst at little or no spring pressure .