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valve adjustment question

gumbydood

Jr. Member
Joined
Jul 5, 2009
Messages
81
I'm putting a rebuilt 302 into my 71. The motor has zero miles on it, but it was rebuilt about 5-6 years ago, according to the guy I bought it from. When I bought it all of the rockers were tightened completely, holding the valves slightly open (why??? no information). I'm assuming this caused the lifters to be completely compressed. I have loosened all of the rocker bolts (I actually removed each lifter, applied assembly lube, and replaced loosely)... so here is my question:

Do I need to provide oil pressure to pump the lifters up before I adjust the valves? I've got the engine on my stand, and would like to put it in as "ready to run" as possible... so should I fill it with oil and spin the oil pump before I adjust the valves?

Thanks
Eric aka Gumbydood
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
Kinda depends most 302's do not have adjustable valves(not from the factory anyways) unless the heads have been modified. So basically if its a stock rebuild you just tighten the rockers down and torque to spec. I wouldnt bother with trying to pre pressurize the lifters at this point but I would do it before engine startup.

Sounds like you have 77 up type heads if you have rocker bolts if so then you just torque them down.
 
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gumbydood

Jr. Member
Joined
Jul 5, 2009
Messages
81
sorry, they are studs and nuts, not bolts. standard shoulder-type studs... the main shaft is larger than the threads, and there is a tapered shoulder.

what should I torque them to? I'm used to screw-type adjusters (nissan, honda) not hydraulic lifter stuff...

G'dood
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,355
Other things that effect that relationship though, are any machining done to the heads and block (though minimal, it's worth mentioning), new pushrods of a different length than stock, mixing and matching components from other engines, pulled studs (opposite effect though) or studs seated into holes drilled too far (unusual, but not impossible) and probably other things as well.
Since the rockers are non-adjustable and you just turn the nut down to the stud shoulder, you have to rely on everything else still being kosher. If one thing is not, you cold be over-tightening things enough to open a valve.

The way to tell (from memory) is to cycle the engine to get every cylinder to TDC before you tighten the nuts. Turn the nut down to zero lash, and measure (or count the turns) the distance that the pushrod is then pushed into the lifter.
There is a spec, but I forget what it is. Say it's half an inch, just for discussion's sake. If the pushrod is pushed in from 7/16 to 9/16, it's within spec. If it goes less, it's not enough. More than an inch, and it's going to lock the valve open.

Someone will probably have that spec, but it's how you check the setting of the valvetrain when first torquing down, to make sure it's all within spec.

That make sense?

Paul
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
The only spec I remember requires you to torque the rocker arm down to spec then collaspe the lifter then measure the gap between the valve tip and rocker arm. cant remember the exact spec but I think you need to have at least .100 clearance with the lifter collasped. Will have to pull the book out in the morning to check the actual spec. Of course if you tighten the rocker arm down and the lifters dont collaspe any then maybe the pushrods are to long or something was machined wrong in either case shorter pushrods would be required.
 
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gumbydood

Jr. Member
Joined
Jul 5, 2009
Messages
81
Well, since the engine was assembled by a "well known engine guy" in the Couer d'Alene area (according to the guy I bought it from), and the valve covers were installed, I'm going to assume (hate to but...) that he knew what he was doing and put the right pieces in when he built it. I have no way of knowing if the deck was blocked, or the heads were milled... so torque 'em to spec and hope for the best!

Thanks for the advice
G'dood
 
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