So I installed my 7.425 pushrods and it’s still clackin from what seems to be everywhere, I know .025 isn’t a big difference so it does seem I should still go longer but as it was running it seemed to be having a misfire as well. This could be caused from me taking the valve covers off and not putting something back in the right spot but as I was installing the rockers, I was tightening them down and the springs began to compress as well. I don’t remember this happening with the other pushrods before but then again I could have easily forgotten a detail as such but is that normal-like is that the preload occurring with the lifters as well? And if it isn’t normal is that causing my misfire? (Misfire seemed to come from passenger side-so again I could have put everything back together wrong)-note:this could be a placebo but it did seem to be just a little more quiet

 

So I just found another forum stating this :

Re: Pushrods too short = misfire?
Todd ...

with your cam and unmilled heads, you need the stock 7.40" rods.

As far as checking preload, just look at this:
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CHECKING LIFTER PRELOAD

Turning the engine, bring one of the cylinders to TDC. The valves will be fully closed.

Now, fully loosen one of the rocker arm bolts on that cyl.

Then start turning the rocker arm bolt down until the lifter is at "zero lash". You will be able to tell it is at zero lash when the rocker bolt gets very hard to turn. It gets hard to turn because the valve spring starts to compress. Again, stop turning the bolt as soon as you feel resistance to turning.

Mark the bolt with a marker.

Now count how many turns it takes to completely tighten the rocker bolt to 22 FT/LB.

The bolt should have turned between 1 3/4 to 2 turns for the acceptable GM lifter peload.

If you don't get the 1 3/4 to 2 bolt turns of preload, you need a different length pushrod. (IE: you need a shorter rod if it takes much more than 2 turns, and a longer rod if it takes much less than 1 3/4 turns).

I really think anywhere between 1 to 2 turns is acceptable. Remember, hyd. lifters can operate within a fairly large margin of preload as long as it's not excessive.


NOTE: You really only need to do this on one cylinder. The rest will be the same.

NOTE: If you have aftermarket Comp Cams “Type R” lifters, I understand that those like less preload than stock lifters. Instead of 1 3/4 to 2 full turns as indicated above, about 1/2 to 1 turn may be more acceptable.

NOTE: Allways run the engine prior to checking the preload so as to get the lifters pumped up. This is important if you just installed new lifters or had the old ones out while installing a new cam.

Ron,

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going off of this i tried this and I have stock lifters and I got 1 1/4 turns before it was at 22 ft/lbs. and this forum also cleared up that the spring is supposed to begin compressing so I was much too short before and I still am now. So I really should rock some 7.480 push rods

 

Find zero lash measure pushrod tool add preload and that is it. People make this job more difficult than it is. You said the stock pushrod was zero lash so you just add the preload of your lifter to a stock 7.4 pushrod. The new cam has a smaller base circle that is why you need a longer pushrod. 7.450 would give you .50 of preload. With stock lifters you might want to go with 7.475 for a tighter preload.

 

So I still have some ticks with 4.750 pushrods, at this point I’m not gonna really worry about it, but I believe it is significantly quieter than the first time. I could go even longer but that’s another $100-$200 that at the moment I can’t afford. I also believe my janky Exhaust may be adding to the noise. But referring back to previous information, It took about 1 1/2 turn on the torque wrench until I hat 22 ft-lbs and before it was like 1/2 a turn so I believe I’m in a good area at the moment.

 

Seem to be wasting lots of time on this. Get a comp cams pushrod checker. Install the rocker. Torque it down. Lengthen the pushrod till you have zero lash. No up and down movement. Little side to side play. Take the pushrod out and check it with calipers. Add your desired preload value to that number. Call Manton and order pushrods. They will be perfect. Done.

 

I totally agree. NOTE!!!!! I don't know who this "Ron" guy is, but unless I'm thinking wrong, and full of **** (depends on who you ask!!), "Ron" has his thought process completely backwards!!! If you turn a rocker bolt for almost 2 turns, and you are just getting to zero lash, you want a LONGER pushrod, not a shorter one!! Also, on the other side of the coin, he says if you get less than 1-3/4 turns you need a longer pushrod. NO!!! If you don't get enough turns of the bolt, you would want a SHORTER PR, not a longer one! Anyway, as I said, I agree with you. This is making this way too complicated. OP should just use an adjustable pushrod checker. It would seem "Ron" is writing a complicated recipe for a P&J sandwich, ferchrissakes!! All ya need is P&J, and 2 slices of bread. This isn't that difficult.....

 

It is explained backwards, I noticed that back then.

Also the OP says he has a pushrod length checker and explains how it's being used and seems correct. OP's thinking is off about get to zero lash and add some oddball number instead 'regular' lifter preload.

I'm amazed at how many people say get a PR length checker and explain how to use it and get several post likes after the OP already said he has one and it using it properly in the first (unedited) post. Seems strange to me.