New 340 cam -bent pushrods

[Dustu]

  I just changed the cam in my 340 {lobe down} to a voodoo very close to same spec. as the comp . cam I had now .2 cylinders are bending pushrods ,I can't believe it would be hitting the piston ! No. 5 and no. 7 .  int. .475 lift and one exh.494 lift  2 deg. adv..Old cam was .488 .491 lift 2 deg. adv..Trw forged pistons and 1.5 rockers. This motor was a problem from the start of the rebuild !

[Chryco Psycho]

what pushrods are you using?
 with th ehuigher spring loads & fast ramps onthe Voodoo cam it may be enough to bend them

[Dustu]

Was using a set of summits,ordered a set of crane's twice the price . Bent 2 of those .Same dia. Higher tensile.Same springs.

[ChallengerHK]

If I understand what Chryco is saying, it's that the lift on the Voodoo may be the same or less but because of the ramps it maybe opening sooner, so that it's at maximum lift earlier, while the piston is closer to TDC.

[Oldschool]

You might want to take a quick look at your valve springs and retainer to valve guide clearance.  The lift increase is minimal and this SHOULDN'T be a problem but it doesn't hurt to look.  Make sure the valve spring/springs/dampers are not coil binding and that you have clearance between the under side of the valve retainer and the valve guide. If you have valve to piston issues, you would know it more than by having bent pushrods.   Just my old 0.02......        

[360 'CUDA]

Are they exhaust pushrods?

[Dustu]

I had removed the spring and checked for the retainer hitting was ok .Guides had been cut down for teflon seals.I could spin the valve with the air pressure off ,seems to be seating ok and not bent .I did measure max lift  the valve was opening and hold it down for full revolution of the crank .There was a slight hit but I couldn't really tell when it was in relation with the cam lobe- piston position ,I was turning it with the starter under the hood ,so I'll have to get my son to help and turn by hand. Had roller rockers and tried 273 type also.

[Chryco Psycho]

the lobe diameter is less with higher lift cams so you may need .050 longer pushrods

[Dustu]

The new ones I got were longer .Will check more next week.

[Oldschool]

There was a slight hit but I couldn't really tell when it was in relation with the cam lobe- piston position ,I was turning it with the starter under the hood ,so I'll have to get my son to help and turn by hand. Had roller rockers and tried 273 type also.

You stated that you had longer pushrods and you definately felt it "hit" something.  I'm leaning towards coil bind of the inner valve springs or damper springs if you can't see any coil bind involving the outer spring.  Turn the engine by hand and use a light and look closely when you feel the "hit".  Let us know....   

[Dustu]

I had removed the spring and released the air pressure.There was no spring on it I was holding it with my hand open to max lift .But I can't say if it was btdc or after .Will do more checking mon.

[Dustu]

No coil bind . I did see that the 2 bent p.rods are rubbing where they come through the head ,must be bowing them from that a max lift.several others are close I see.Looks like the entire shaft needs moved up to center the p.rods in their holes .If you know what I mean !Pain !           

[Chryco Psycho]

when I port heads I usually grind beside the pushrods to gain clearance there

[moper]

You shouldnt center the pushrods in the holes. You center the rocker over the valve tip. Is there any chance you bolted the shaft down and those two pushrods were not centered in the right place? Wouldnt be the first time it happened. You have retainer to guide clearance. You have spring clearance. You did bend the pushrods so the holes will be marked already. Something's fishy. I've run some larger cams on factory type heads and stamped steel rockers and never, ever, did pushrods (even the larger 3/8 ones) hit the factory holes. Aftermarket heads have issues with it. But not factory stuff.

[gomopar440]

you could have a left and a right rocker swapped. That would possibly cause the pushrod misalignment.