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lifter preload and push rod length procedure?
Hello
I can find plenty of information on this subject for engines with adjustable rockers and/or stud type rockers, but not stock non-adjustable shafted mounted rockers. How is it done? This is my guess on how it's done: I assemble the engine up to the cylinder heads The lifter I check is on base circle - E.O.I.C. I install a length checker tool - screwed in so it's too short install the rockers and shaft screw out length checker until all visible play is gone but, no preload remove tool and measure with 12-in calipers Then I add my lifter preload to the that measurement and that will tell me push rod length From what I can tell, preload is usually in a range and if the camshaft isn't a stock replacement the numbers should be provided by the cam manufacturer. Ideally all the cylinders should be checked. At the very least the four corners. So, how wrong am I? |
I looked for information on hydraulic cam pushrod and non adjusting rockers in the mopar engine book and there was zip it was all mechanical cams and adjustable rockers. But your idea looks sound, if you haven't cut the heads or decked the block you can compare your measurements to the stock pushrods.
If your using a retrofit hydraulic roller cam good luck. |
For hydraulic lifters you may wish to consider adding 1/4 turn to the checker tool to give the necessary lifter preload. When adjusting my old T/A rocker arms it took 1/8 < 1/4 turn to preload the lifters sufficiently. I believe the adjuster screws were 24 tpi/ 0.0416 " per turn.
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Your procedure and math looks good to me.
Check how your supplier measures as some ball and ball pushrods have a small flat spot on the end, some measure to the flat some measure as if the ball was round with no flat spot. Check your lifter supplier as some HP lifter preload is as little as .006". |
Thanks everyone. We'll see what happens,
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Well, it looks like this plan may have back fired..
At least for the Summit K-6900 option. I contacted Summit and they don't have a lifter preload spec. What they did give me is this: Thank you for the inquiry on the correct preload for our camshaft. You would adjust it down to 0 lash and a half of turn out. After you run the engine, I would re adjust. Thank you for your business You are using hydraulic lifters you have to be sure they are fully pumped up. For start up you adjust to 0 lash and back off 1/2 turn. At this time we do not have any preload measurements Thank you for your business I assume they think I have adjustable rockers like a chevy.. either way. Those instructions don't make sense to me. They want me to tighten everything... then loosen it... were is the lifter preload? I don't get it but, that could be my ignorance. Camshaft Manufacturers Description: Smooth idle, excellent low-end torque/horsepower, towing, good fuel economy in stock engines. Good camshaft for turbocharging. Frankly I don't know how I would confirm lifter preload with a stock cam after decking and gasket replacement. The spec isn't in any of my books. I can't find consistent numbers online Anything from .020" to .095" or "load it 1/2 way down" I assume it's not in my books because it's already "engineered" into the stock non-adjustable drive train.. Well, I don't know were to go from here. Now what? |
In the mean time.
I sent Melling an email about their MTD-1 camshaft which appears to be identical spec wise to Summits SUM-6900. Like the summit cam it say it will work with a stock engine. Does that mean I can just throw it in my engine and forget preload and thinking? (minus break-in of course) No thinking sounds nice. I feel there's been too much of that lately.. I mean I have you seen my posts? :D I'm going to bed. MTD-1Product Information
Product Attributes
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See a lot of .020"-.060" , I like .050"-.060" on a street engine, this would be for a OEM style not a HP style lifter.
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Alright, so more preload for street. Less preload for high performance.
I finally have some numbers to aim for. Thank You In other news, Melling got back with me. "Stock valve train can be used" "Use factory settings, preload will be the same as the original cam" Plus, since the stock valve train isn't adjustable. The stock length push rods should preload it correctly. Of coarse I'd try to confirm using a push rod length tool. I'm also awaiting reply from comp cam on their product recommendation. This cam of theirs has caught my eye: 20-210-2 Hydraulic-Great for 360 4bbl. in medium to heavy-duty applications. Great performance cam for 318 withpower brakes and air. We'll see what happens. |
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