I refreshed a 351m a little over a year ago- checked all the clearances, replaced all the bearings, had the heads rebuilt, etc.
I replaced the old emissions cam with a comp 268H while I was in there and for some reason I didn't have the presence of mind to replace the valve springs...
It has run fine for nearly 20K miles but has always had a fair amount of valvetrain clatter, I can only assume I have bent pretty much every pushrod in the engine.
Now, I am looking at doing a few more things to this engine first of all being an attempt to undo this screw up.

Of course I am going to replace the springs, but the pushrods perplex me.
Ahould I replace the pushrods with those of the same length? I read that they are 9.5" long, is that correct?
The pushrods that comp recommends for that engine and cam aren't even 8.5" long.
That seems a little short to me. Or is that correct?
I'm using stock rockers and don't have the rotators.

 

. Whether you need stronger springs or not is a matter of if the lifters are pumping up at highest RPMs... the 268H (218/218?) cam prolly gives a max power shift point of around 6,000 RPMs... will it rev cleanly that high or does it suddenly stop revving lower at lifter pump up? (Assuming 4 bbl. carb., power may start slowly dying after 3500 RPMs with small 2 bbl. carb.) ... Hard to guess at actual RPMs, should hook up a tach temporarily, it's not hard... (Also, if old springs have over 100,000 miles I'd replace with new ones to avoid breakage, since a bigger cam is harder on springs)


. Pushrod length can change by standard or reduced base circle cam, flat tappet or roller lifters, and rocker arm design... for your purposes, you prolly only need to adjust the thickness of the shims under your stock rocker arms to get proper piston preload distance into the lifters... your pushrods prolly aren't damaged, since solid lifter cams run lash clearance and clicking all the time...


. 351C and 351M/400 engines use the same cams, but 351M and 400 engines have about 1" taller block height so pushrods would vary about 1" in length...


. First step would be do a compression test on all 8 cylinders to make sure your current hydraulic lash isn't so tight on any cylinder(s) that you have valves that can't fully close/seal... this would manifest itself as some cylinders at 125 psi or so and some at 75 psi or lower or even -0- psi... then loosen rocker arms and re-tighten to see how far down the pistons are going in the lifters as each lifter is sitting on only the base circle (not the lobe) of the cam... this requires rotating the engine some by hand to make sure each one being checked is down on the base circle... usually want the pistons down about .020" - .040" into the lifters to allow piston movement for automatic adjustment to -0- lash via oil pressure with engine running...

 

Honestly, you need to measure your push-rods.

Read post #109 here:

https://www.ford-trucks.com/forums/1...l#post14824073

Read posts #46-51 in this thread:

https://www.ford-trucks.com/forums/1...rt-deux-4.html

My recommendation:

Read both of those above links. Then call Tim Meyer, tell him you will be ordering pushrods from him and need to order a push-rod length checking tool and an oil pump priming setup. Set the pushrod checker to the needed length, send it to Tim and he will send you 16 rods of the proper length.