Lifter preload at startup question

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74desertduster

74desertduster

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I am getting closer to finishing my 360 LA with Magnum heads.

I have read through the tech archives and anything else I could find about checking lifter preload prior to startup......but I want to make sure I understand.

Once I check the lifter preload and it falls within the .020 - .060 number....I am good?

And this is where I get lost...if it is not within the specs.....what procedure do I use to adjust?

Once all the preload numbers are good....are there other valve adjustments later?

Sorry for the questions...and thanks for all the great help here. The engine is starting to look like an engine now!

Brian
 
If you have adjustable lifters, which Magnum heads do, then you can adjust them. The lifter should be depressed a min. of .020 and not more than .the .060 for safety sakes.

If you need to adjust, the lifter should be on the base circle, not being lifted by the lobe of the cam. No other adjustment should be needed.
 
Thanks....and this is done with lifters dry before startup, correct?

And do each lifter/rocker combo?
 
yes. but then I always prelube the motor after you set the lash and hand spin the motor over as you spin the oil pump. that way you won't hang up a valve and you don't get the lifter knocking when you first fire it up from starting dry. if you try to prelube them before you could possibly get a valve that hangs open.
 
I was wondering about the prelube...since if I am turning the engine over by hand, the lifters are gonna wipe away a lot of it from the cam, yes?

I need to buy some more.
 
either way when you adjust it some will. I wait to put the intake on so you can check for issues and apply lube before the final button up. then all you do is right before you fire it up prelube it one last time, checking for any leaks or other problems then drop in the dizzy and fire it up.

oh and if your wondering how to get the lube on just get a small brush and with the intake off you can reach all the lobes.
 
Ok...I understand the lube part and actually already got a couple brushes figuring I was gonna need them anyway.

So please bear with me...this is what I do to check the preload:

Check the preload on each lifter....on a compression stroke so valves are closed.

If preload is bad, adjust it...but how? Shims?

Thanks for helping!

Brian
 
Much more important than the lube is the engine MUST start immediately when you turn it over, and it must NOT idle. So make sure you have spark and fuel and a decent cooling system (not totally filled but close) and be ready for it to run for 20 minutes at higher than 1800rpm. It's ok to have it turned 8-10 times over during final checks and assembly, and installation after the break in lube is there. But it shouldnt be turned by the starter say to get oil pressure up. Use a priming shaft and turn by hand no more than 2 turns after the drill gets dragged down and oil's flowing.
 
like stated get yourself an an adjustable pushrod checker. all you have to do is install the tool with the lifter all the way down so its on the back side of the lobe then tighten the rocker down. then adjust the pushrod out until it just gets rid of the slack between the rocker and pushrod. don't put pressure against them, just until it touches and there will be no play if you try to move the rocker back and forth. then remove the rocker and pushrod and measure the pushrod length and add about .040 to that number. that will be the length you need to order. if you look online at say summit they will come in increments of .050. as long as your in that spec of about say .030 to .060 you will be fine.
 
Someone before stated that the magnum heads have adjustable rockers and this is wrong. That is why it's so crucial to get the preload correct the first time and order the right pushrods. Stock magnum heads have pedestal mounted rockers and have no adjustment. The adjustable pushrod length check is a must. Once the rocker being checked is in the right position in respect to the cam and torqued down then you can start adjusting the pushrod for correct length as stated above. Take your time and do it once. (speaking from experience:)) And I'm sure you know that the rockers oil through the pushrods so you need the pushods with oiling provisions.
 
That's good info about the adjustable pushrod for checking. I was set to order 7.650 pushrods because that is what I had seen on other posts for using Magnum heads on an LA block.

So when I take the measurement with the adjustable pushrod and order the length I need....making sure I have it correct.....do I just put the pushrods in and tighten up the rockers? No more adjusting or measuring at that point?

And yes, I will be getting rods that oil through.
 
I think you might be comfused with using a solid lifter rather than a hydraulic lifter to set the preload. If you are using a hydraulic lifter you do want to make sure you are getting on the hydraulic curcuit on the lifter when you tighten down the rockers. The stock magnum heads rockers are not adjustable. You will need to order the mopar performance pushrods that are 7.650" with the oil passages.
 
If your using stock heads with the pedestal mount rockers you should be able to drop in the pushrods and torque them down and be done with it as long as your measurements are good. Also I would highly recommend upgrading the springs if your running a flat tappet cam. I don't think the stock magnum springs where designed to be used with a flat tappet cam. I had lifter tapping noise that sounded like a "sewing machine" that I could not get rid of no matter what I did. I never did upgrade my springs or check what the specs are on the stock ones. but I just think it may be the issue with the flat tappet cam and the 1.6 ratio rockers.There is a post about using chevy v6 beehive springs and retainers that may be a good choice. Good luck on your build.

http://www.forabodiesonly.com/mopar/showthread.php?t=66298&highlight=beehive+springs

After reading the article it looks like there may be installed height issues with the chevy beehives if you running more than around .450 lift on the cam. Still a good article though.
 

I am using a flat tappet Lunati cam with hydraulic lifters in an LA block with magnum heads, Hughes 1110 upgrade from stock springs and retainters. Was going with 7.650 pushrods, hollow for oiling.
 
as long as the pushrods give you the proper amount of preload on the lifters you will be good. always check though. too little and it will clatter like crazy and too much and the valves might not close all the way.
 
those pushrods may in fact be the ones you need. I would just check to make sure that way you know for sure it's right. "Just peace of mind". With rebuilt engines tolerances change as metal is removed. Also you can make a checker pushrod with an old pushrod to keep the cost down.
 
OK, just ordered an adjustable pushrod for 9 bucks shipped...

So can someone make sure I have this right?

I use this to check the pushrod length with the lifter on the backside of the cam (valve closed).

Once I have the tested length, add .040 to it and that will be the pushrod length I want to run?

Believe it will put me in the middle of the .020/.060 lifter preload?
 
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