Ok, Im in a dilema. I keep bending pushrods. I installed a bigger cam but it still fits in the specs of my vortec heads.....could i have degreed the cam wrong? what are other reasons for pushrods bending? Both intake and exhaust valves are bein bent...any ideas would be greatly appreciated!

 

Did you check the pushrod length? Maybe they are too long, that can happen when you swap heads, cams, etc.

Also, I know there are some limitations on the lift of a stock vortec head, they may require some modifications for your cam to work.

 

I think there are several reasons they could be bending.

Are your valve springs bottoming out before full lobe lift is achieved?

Are you using guide plates for the pushrods, or self-aligning rockers? IIRC, with the Vortec heads, you can use guide plates OR self-aligning rockers, but not both!

Degreeing the cam is ALWAYS a good idea, the cam manufacturer can make a mistake too, and give you one that is out of spec. The only sure way to tell is by doing the whole degree bit.

Are your lifters pumping up? Are they running at hydraulic lock, and basically making them into solid lifters?

Did you follow the proper sequence when adjusting the lifters?

Is your head gasket too thin?


These are just some of the things I thought of now, I'm sure there are other possibilities.

Hope this helps, hope you find the problem, and hope it's not too expensive!
Paul

 

heres the cam :Cam Specs, Int./Exh: Adv. Dur. 278°/290° , Dur. @ .050” 222°/234°. Lift: .467", .494" everyone said that should work without modification....and the pushrods are the same from when i had the motor with its stock cam.......we had it cranked for alil yesterday...but it bent 3 pushrods

 

1.well...the springs are compressing alot......
2.umm..whatever vortec heads come stock with
3. k
4. they are anti pumpup crane lifters...
5. yes, adjusted them to where u could spin the pushrods
6. its a felpro vortec headgasket.....

 

I have Vortec heads. I remember the maximum lift tolerable without modifying the heads is .480. That has got to be your problem.

 

I was reading in another recent Vortec head thread that you could get
"beehive" springs for them - from Crane - I think. This is an easy fix for
a high lift cam. With compressed air, you can even do them with the heads on.
Strange you are bending BOTH intake and exhaust, though - with .480 limit.

Good luck :seeya

 

:iagree:
ive been looking into the vortec and ive been told the highest you can go is .48
either grinding down the setas of using the LS1 style eehive springs sounds like what you need to do.
Just too much lift for the stock Vortec heads i think.

Also other than bent pushrods how do you like them cause i think im going to get some soon.

MAtt

 

You might want to check your lifters, if you are putting enough force to bend the pushrod, you are probably damaging the lifter too, and probably the cam. I've found that checking the pushrod by pulling up and down is more dependable than spinning them.

 

The "spin" method (twisty-turny) is known to be a pushrod bending, valve bending and piston destroying method of adjusting hydraulic lifters/rockers/valves.

I cannot count how many engines I have had to repair for customers who have tried that "book" method.... this includes many Forum members.

Don't do it.

The internal spring resistive state of any particular lifter is dependent on several things, and all lifters to not behave the same under pressure. One lifter may bind up the pushrod at zero lash, another identical lifter might react the same at .120" down (internal spring compressed). This is true regardless of who made the lifters, and, regardless of whether they are new or used.

If you assemble an engine, and find that for some stroke of luck, all of your lifters behave identical.... you are in the Twilight Zone. Consider it the exception... not the rule.

Following the proper sequence (lifter on the base circle of the cam), loosen each rocker until there is slop between the pushrod tip and the rocker. To determine this, hold the pushrod so it is in contact with the lifter, but not exerting pressure on the lifter plunger & spring. Gently rock the rocker . You can hear and/or feel when there is air between the pushrod and the rocker. As you continue to rock the rocker with one hand, adjust the rocker down until the pushrod & rocker have zero clearance. Make sure you are NOT compressing the internal spring of the lifter when you do this. Depending on manufacturers recommendations, then take the adjustment down 1/2 to 1 turn further. Pretend you are doing brain surgery. Practice on one until you get your method down, then do the rest. The procedure works best when there is no oil film between the tip of the pushrod and the rocker cup..... so you can hear & feel the gap more accurately. You can work some oil into each joint when you are done by rotating the engine & squirting them with an oil can. This is unnecessary if you use a pre-lubing tool to pre-lube the engine, or if you establish oil pressure before you allow the plugs to fire.

I have no idea who came up with that "spin the pushrod" witch hunt, but they never worked out in the "real world". I've seen it several service manuals.... and all I can do is just shake my head. Actually, maybe I shouldn't complain because it has sent many new customers to my door step.

1) I am only responding to the adjustment method, not the combination of valvetrain parts you have assembled.

2) This is another one of those topics that has been repeated (on many forums).
There may be more stuff in the archives.

PS- I have been in the "engine" business since dirt was invented.

Well... almost.



[Modified by Tom454, 3:20 PM 1/2/2004]

 

It sure sounds to me like you are getting into spring binding to me. You really ought to look into cutting the guides down and widening the seats for higher lift springs.
It'll mean pulling the heads, but you can buy the tools from Comp Cams and do it yourself with a 3/8" drill. There is a mandrel and two cutters, one cutter cuts down the height of the valve guide and the other wideneds the spring seats. Chevy High Performance has an article on doing it. http://www.chevyhiperformance.com/te.../148_0208_vort