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getting the valve train geometry correct


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This is great information, and I will be doing the same thing fairly soon. I was wondering what length push rods to get, and now I know I need to measure to determine the proper length. It looks like a solid lifter will be useful for checking the piston to valve clearance as well as determing the proper push rod length. Can you buy just one and is there a specific model/size I would need to buy (for my 94 LT1 engine)?

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michael, the final measurment wasn't enough different to post more pics. Take a look at the last two and that's pretty much what I ended up running. The actual wipe was very narrow, didn't measure the width.

 

I installed the rods and rockers friday, got the intake glued on and now I need to find some tall valve covers that look ok. I used to have some Comp polymer valve covers, I might pick up a black set.

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  • 3 weeks later...

I ordered a solid lifter and an adjustable length pushrod to determine the proper length needed for my setup.

 

My question is once I determine the length required with the solid lifter how do I adjust for the hydraulic lifters I will be using? I assume I need to add or subtract the difference in the height of the solid versus the hydraulic lifter, but is that difference with the hydraulic fully pumped or fully depressed?

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To check you can measure the over all length of the solid lifter and the hydralic your going to use. Then check the depth of the sockets the push rods sit in, if they are the same then you should be very close. Whatever lenth push rod you determine w/ the solid lifter will work w/ the hydralic with the pre load set.

 

Shouldn't be an issue.

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I looked closely at my stock LT1 lifters and I decided to go ahead and replace them. I called Comp Cams for advice and the person I spoke with in tech support was extremely helpful. Since I was looking at ordering a new set of lifters he recommended to take one of the old lifters apart and shim it up with washers to use for valvetrain geometry checking. He also recommended putting on checking springs before running the test (they cost a whopping $2.28 for a pair). He also sold me the lifters at a lower price than their list...and even lower than Summit's price.

 

Once I figure out the proper pushrod length I'll be calling them back...and based on the support I got I'm happy that I have all Comp parts (cam, lifters, rocker arms, springs, and pushrods).

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I removed the retaining lock from one of my stock lifters...at least I thought it was stock. Based on what I'm looking at and what I've read, it looks like I have a solid lifter! I couldn't get the pushrod seat to compress before I took it apart, but I thought maybe I wasn't pushing hard enough or the amount of travel is so small it's hard to notice. The center of the lifter is open, but it looks like there's an internal step inside the lifter body preventing the pushrod seat from moving.

 

It would be pretty hard to take a picture, but I can if it would help. How much travel should there be in my stock LT1 lifter? It looks nothing like the drawing of a hydraulic lifter in this tech article http://www.cranecams.com/?show=techarticle&id=2. I guess it's not really a problem since I'm getting new hydraulic lifters, but I would like to know for sure what my old one's are (if they are solid, now I can easily check my piston to valve clearance and valvetrain geometry).

 

edit: I found a site that has some good pictures of a stock LT1 hydraulic lifter and a solid one. Maybe I just haven't been able to get the piston assembly out of the lifter body. I will investigate more tonight.

http://www.caspeed.com/gallery11/

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If you are not going to use it, pull it completely appart, you can put it back together pretty easily. The piston inside is SUPER close tollerance fit, so the vacume it creates when you pull on it might make it seem like it won't come out, but it will. Hook it w/ a paper clip or something .

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If you are not going to use it, pull it completely appart, you can put it back together pretty easily. The piston inside is SUPER close tollerance fit, so the vacume it creates when you pull on it might make it seem like it won't come out, but it will. Hook it w/ a paper clip or something .
Yes, it was a SUPER close tollerance fit and the vacuum did make it seem like it wouldn't come out; but I did manage to get it apart last night. Now I can shim it up with washers and use it for checking.
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So I installed my checking springs and placed my new head on the block with the old head gasket. I didn't want to use the new one because I had to cut out around the pushrod hole to allow the adjustable length pushrod checker to fit. I turned the engine a couple of rotatons and with the checking springs my old hydraulic lifters stayed expanded so I used them as is. After playing around a while it looks like I got a pretty good wipe pattern. The picture isn't the best, and I didn't touch up the red marker at all...but I think I got it.

DSCF2645.JPG

It was actually pretty fun and easy to do. Because of the nuts on the pushrod checker I actually had to have the checker in place and then set the head down over it...otherwise I couldn't get the tool in place. I also had to be really careful installing and removing the rocker arms so that the wet ink didn't get messed up.

 

So thanks for all the info and now I'm ready to order up my pushrods!

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Bart, the exhaust looks perfect. Sorta hard to tell about the intake, looks like it's smudged some. As long as the valves and valve job were done right they should be the same anyway.

 

Good Job!!!!

 

jt

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  • 11 months later...

Found the following thread on Chevytalk.org. Interesting.

http://www.chevytalk.org/fusionbb/showtopic.php?tid/156966

 

The thing I found most interesting and gratifying is this link in that thread:

http://www.mid-lift.com/intro-mid-lift.htm

 

I have thought for a while that the whole "the witness mark from the rocker must be exactly centered on the valve tip" was not correct. I had thought that what was really important was to have the smallest travel of the rocker across the valve tip. Seems Miller agrees. I mean, you need to have the roller NEAR the center so that you don't get close to the edge and peen over the valve tip, run off the edge, etc., but being exactly in the center is not the "Best" thing, IMO.

 

To bad I don't have a spare 8 or 900 bucks sitting around for those neat rockers! LOL

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