Pushrod Length Check

[RonJones]

I am installing F3ZE Cobra GT40 heads with stock valve train on the ‘95 F150 roller cam 5.0 in my 73 Bronco. I wanted to check pushrod length, as I’m not sure if they’ve been resurfaced. I came across this discussion:

https://classicbroncos.com/forums/showthread.php?t=51328

“I'm assuming you're working on a stock 302 in the '72 EB listed in your
profile? from the factory that engine would have positive stop
(non-adjustable) lifters. the procedure for those would be to bottom
the nut (i.e. turn it until the pivot bottoms and turning torque increases)
then final torque the nut to 17-23 ft.lbs.

if you think your pushrod length and lifter preload is out of spec due to
engine changes then checking involves: turn crank/cam until valve being
checked has lifter on the cam base circle; tighten the nut down until you
achieve zero lash; then count the number of additional turns until the
nut bottoms out. if it takes 0.8 to 1.75 to go from zero lash to
bottoming then things are within spec and lifter is at proper pre-load.
otherwise you need +-0.060" pushrods“

I tried doing that, but my results vary in and out of spec considerably depending on where I call zero lash (my lifters are bled down). The ‘95 Mustang manual calls out a procedure where the lifter is bottomed out and the rocker/valve stem clearance is measured (see manual excerpt).

The problem with that procedure is that it calls out a tool T71P-6513-B, which is kinda expensive (170$). Australians sell a less expensive variant, a Toledo 304032 or a T&E 92120, $40-60 US + shipping, works out to a C note.

At this point I’m thinking of trying to pump up my lifters by priming the oil pump, in order to get a more precise zero lash, vs fabbing a bleed down tool vs blowing it off, and torquing to 20 ft lbs and calling it done.

Any suggestions?

 

[bax]

do you have an adjustable pushrod around? get on the backside of the cam, install the adjustable push rod. Make sure is it too short. Torque the rocker down. Adjust pushrod to zero lash. remove rocker, remove pushrod. measure pushrod and add .060. That should work for a pushrod length for your set up.

 

[fishinman78]

I just finished installing GT40X heads on my 347 build. I am using a late model 5.0 block and the GT40X heads us the same non adjustable valve train as the GT40 iron heads so the procedure should be the same.

I started out with stock length 5.0 push rods and stock lifters.

Install all the lifters in the bores and install the hold down. Do not soak the lifters in oil.

The lifters have an internal spring that returns the plunger the top.

Making sure your on the base circle of the cam rotate the push rod back and forth in your fingers while slowly tightening the nut that holds the rocker arm. I used a nut driver to tighten the nut so I could do it slowly and carefully. Once you feel resistance while rolling the push rod you are at zero lash.

Now, take your torque wrench and torque the rocker arm bolt to 20 ft lbs. Final torque should be achieved within 1/2 to 3/4 of a turn of the torque wrench. If it takes more than 1/2 to 3/4 of a turn your push rods are too long. Mine started out at 1 1/4 turns to reach torque. The easiest way to address this is shim the rocker arms.

I order a kit from Ford Racing, M6529A302, and after some trial and error I had to use the .060 shims under all of my rocker arms. This put everything in spec for me.

If it takes less than 1/2 of a turn to reach torque than your push rods are too short and you will need to order a push rod checking tool to dial in the proper length.

 

[cs_88]

X2 on using the rocker shims.
Worked well for me.

 

[jagbucket]

after you do the above You will want to double check where on the valve stem your rockers are hitting, in the middle is the object . mark the valve stem with a felt tip and roll the motor over to mark the stem and check i used an old lifter that was stuck so it did not compress other wise a weak valve spring is used. there are several videos to do this on interweb In my case the push rods were in stock locally at a wholesale distributor so i bought through my friendly machine shop , btw i have adjustable push rod kit to set the length.

 

[RonJones]

My understanding is you can’t remove a 302 roller lifter without removing GT40 heads; apparently Edelbrock and other aftermarket heads have a channel or groove placed facilitating such easy lifter removal. I don’t know about other stock heads. I’ve attached a photo showing a “spare” lifter I stuffed with Aluminum Foil for just that purpose. After removing the Spyder and dogbones it’s still too tall to get out. The only way I can figure to do the center valve stem check is to have 16 stuffed roller lifters and extra head gaskets or a whole bunch of head gaskets, prob not feasible unless I’m missing something.

 

[RonJones]

Fishinman78, your nut driver trick helped! I may be wrong, but at least now my zero lash determination is consistent. I liked doing this so much, I ordered a set of Scorpion 1021 1.6 pedestal rockers. Thanks for your help, y’all!