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I have an L48 with upgraded top end including full rollers (1.6 ratio) and mild cam. I have new 7.8" hardended pushrods. I used the sharpie method and found that my wipe was just below center as you can see on the pics below. I used a pushrod length checker and the pushrods I currently have are between .018" and .020" too long which matches up with the wipe seen below.
So 7.8" - .018" = 7.782" or 7.8" - .020 = 7.78" Cylinder #1 Cylinder #3
Closet pushrods I find available on summit are 7.775" long
Question is? Am I close enough with current pushrods that are off .018" to .020" or do I need to buy the 7.775"
That dimension is not horrible, but you want it better than that. Too long of pushrod could stress the valve-guide and cause excessive wear.
I think you should take a third measurement. If the checker tool is allowed to move one iota, it will throw off the actual length.
I don't have calipers to measure more than six inches, so I had to take my checker to a auto shop to verify the length I needed for non-std pushrods.
Custom made rods will cost more and is seldom worth it for street use. Those 7.75 from Summit should work out better.
Then sell your new, very popular size rods to recoup your spending.
The witness marks show a need for shorter pushrods. The plastic tool is questionable especially when used to measure for non-stock rocker arms. It would be better to use an adjustable length pushrod along with the actual rocker arms being used.
That said, the hydraulic lifters will give away under the full valve spring pressure. That will generally make it look like your pattern needs LONGER pushrods than it actually does. Your pattern needs shorter pushrods so getting those off the shelf shorter pushrods seems to be a good way to go. Close enough for what you are doing.
I have both solid and hydraulic lifters here. The solid lifters are not the same length internally as the hydraulic ones I have. I tried that a few days ago. Same manufacturer.
Solid on left - hydraulic on right. The height difference of the pushrod cup is significant.
The soft checking springs will work for any lifter if you go that route.
Last edited by stingr69; May 15, 2023 at 03:18 PM.
Are you running stock heads with those 1.6 rockers?? I’ve seen in many cases there’s not enough pushrod clearance when running 1.6 rockers on stock heads.
No, I'm using Brodix IK180's. I used an adjustable pushrod and got the best centered witness mark with the pushrod set to 195MM or 7.677 inches. The pushrod's I have are 7.8" so that's a ,125" difference which is significant and more than the .020" i got using the platic tool. I'm assuming that like others mentioned, the non stock rockers expecially with a 1.6 ratio means that the plastic tool is not accurate for this application.
I'm assuming the most important thing is the centered witness mark so I'm ordering 7.675" trickflow pushrods from Summit.
Set up pattern for the skinniest "sweep". Don't worry as much if it's dead centered. Often it won't be and the sweep will hurt a lot more than being off center.
.050" doesn't change things a lot one way or the other in the big scheme of things.....but get it as close as you can.
The little plastic checkers are useless especially with heads that may have things in different places, longer than stock valves and different rocker ratios...even if you get the one for a 1.6.
Pushrod length tolerance
