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Old 01-23-2005, 08:30 PM
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Push Rod Length for this SBC?

hi whats up guys im building a 355 CI SBC for my 77 firebird strictly a street car, the deck height is stock and my heads are Dart Iron Eagle 180cc intake runner, 72 cc combustion chamber 2.02/1.60 valves, and im using a .100 solid dome piston, and 1.6 roller rocker arms with 3/8 stud, it says on Darts website that the stock length pushrod can be used but thats not the case on mine, with the rocker arm tightened down i still have just enough play that i can pull the pushrod out of its seat in the lifter, i know im probably just gonna have to bite the bullet and get a pushrod length checker but i thought some of you guys may have ran into the same promblem on a similar engine, by measuring it with a tape measure and using my caliper the best i can tell i need a pushrod thats .100 longer but thats just "redneckin it" give me some advice guys

i forgot to add something too i called my local machine shop and he told me it we be better to be on the longer side than the shorter side, would it be safe to say i could get the ones that are .150 longer? or would that cause a bind or improper valve train geometry?

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Last edited by 79 Malibu327; 01-23-2005 at 08:30 PM.
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Old 01-23-2005, 08:50 PM
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It seems that you have something else going wrong to me, maybe the lifter is collapsed? Longer pushrods are used to get rocker arm geometry correct, so that the roller tip (or standard tip) of the rocker rides near the center of the valve tip throughout the duration of the lift. This helps keep deflection off of the valve stem and reduces guide and valve train wear as well! Even if you did need 0.100 longer pushrods for correct geometry, you should be able to adjust out all of the slack with a standard length pushrod.
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Old 01-23-2005, 08:53 PM
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all the lifters are brand new clevite, did i do something wrong?
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Old 01-23-2005, 08:58 PM
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You need to check and make sure that the rockers do not roll off the valve stem when fully open if you go longer. I would just borrow a checker from a local shop if you know them. I did this with my Dart Heads and everything was dead on. Course they were setup with stock length valves and I bet yours are .100 longer. You really want to measure and not just guess. All you do is measure the difference between the geometry checker and the pushrod. Then add that to the length you have.

Chris
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Old 01-23-2005, 09:06 PM
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before i do that Chris, could oddrodder be right about my lifters did i do something wrong there?

Chris i checked with the guy i bought the heads from (dirttrackthunder.com) he said the valves are stock length manley valves, so what do you think is the problem

Last edited by 79 Malibu327; 01-23-2005 at 09:06 PM.
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Old 01-23-2005, 09:09 PM
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Yeah, when the lifters are new (not filled with oil), the plunger will collapse very easily! Hydraulic lifters have a very light spring in them that can be overcome with light pressure! You need to lightly seat the pushrod in the lifter so that there is no more side to side slop on the pushrod and then add another 1/2 to 3/4 turn to properly preload the lifter, I also have Dart Iron Eagles, I'm pretty sure they all have standard valve lengths unless you get the big 1.5 springs!
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Old 01-23-2005, 09:12 PM
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i soaked the lifters in regular 10W30 engine oil over night before i put them into the engine, was that the right thing to do? do i need to "pump them up" so to speak
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Old 01-23-2005, 09:15 PM
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It is possible you are pushing down the lifter, but I doubt it from what you said. If the rocker is not even touching the pushrod then they are too short.

Chris
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Old 01-23-2005, 09:18 PM
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see i tighened the rocker down like oddrodder said and got it to where the push rod had some drag to im talking about turning it side to side and it had no up and down play, i turned the engine a full revolution so the valve would open and close then the pushrod was loose again
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Old 01-23-2005, 09:24 PM
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You can pump the lifters up in a coffee can with enough oil to cover the top of the lifters and an old pushrod (pain in the rearend), but I would just adjust them like I suggested.
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Old 01-23-2005, 09:27 PM
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see i didnt pump them up at all, like i said the guy i purchased the heads from said the stock pushrods should work, i hope your right about pumping up the lifters.
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Old 01-23-2005, 09:30 PM
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By the way, I have dealt with dirt track thunder = good people and good prices!!!!
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Old 01-23-2005, 09:42 PM
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thanks ma its nice to have someone with experience to talk to i didnt realize that pumping them would matter that much, im young gotta lot to learn, ive help my uncle build several small blocks, a 383, and a 327 (sold them both with i had them back) im building this one for a friend of mine actually, what do you think about our setup


bottom end is a 4130 forged steel scat crank, forged scat rods, speed pro .100 solid dome pistons, .030 over, heads of course are the dart iron eagles 180 cc inake runner 72cc chambers 2.02/1.60 valves, cam is crane cams blue racer 280/290 adv dur .442/.465 gross lift, vic jr intake 750 cfm edelbrock carb
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Old 01-24-2005, 04:18 AM
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Sounds like you got more bottom end than you need, but each to his own.

Now I am thinking you are not understanding the proper way to set the valves. Do a search on this site on the engine forum and you can find alot of information on setting valves.

Chris
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Old 01-24-2005, 08:00 AM
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Sounds to me like the slot on the bottom of the rocker arms are hitting the radius of the rocker studs. I've seen this with wide bodied aluminum rocker arms. You can grind the edge of the bottom slot a bit but that can get messy and requires a lot of cleaning due to the grit that might get in the bearing. Going with a CompCams type steel or stainless steel pro magnum rocker usually gives enough clearance. Otherwise the boss where the stud is screwed into would have to be lowered or look for studs with a smaller radius.
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