[Steven69]

I have a 69 Chevelle: 454, .100 domed pistons, 781 heads, .553/.573 crane cam 236/246 dur at .050, 1.7 roller rocker arms, th350 3000 RPM stall, 3.31 rear.

I was installing my new RPM Air Gap manifold, when I discovered the majority of my pushrods are bent, not broken. Any advice other than buying the proper length pushrods? What could have caused this other than the pushrods too long? Roller rocker arms too tight?

 

[davis95]

Wrong rods or improperly adjusted. You got it.

 

[VinceS427bb]

check valve retainer to guide clearance

check for coil bind also

what kind of cam? solid-hyd.-solid roller-hydro roller???

 

[Steven69]

Hydraulic Flat Tappet crane cam
H-296-2

 

[Tom Mobley]

check carefully for clearance everywhere in the valve train. pushrods can bottom out in the guideplates, retainer can hit the top of the valveguide or seal, springs can coilbind, etc, etc. That cam has enough lift to cause any of these problems.

Does it have the right valvesprings for that cam?

 

[Steven69]

My car was running fine before I replaced from original rockers to roller rocker arms and setting zero valve lash myself. Now I can't tell what the appropriate pushrod length is since they are bent. I am at a loss, and no one in San Diego has been very much help.

 

[BillK]

Steven,
Do you have a machine shop that you deal with ?? If so, take one of each pushrod to them and ask them to get you a set to replace them, Any halfway competent automotive machine shop should be able to figure it out. I would just straighten them as good as I could get and then measure them. Then order new ones. If you order the parts from them, and ask nicely, they might even explain how to properly adjust the valves Its a lot easier to show someone in person than to try to explain it on the internet.

By the way, after all is said and done, dont be surprised if you have bent some valves

 

[Steven69]

I just spoke with my machine shop and they said to come down like you said. Although he did suggest longer rocker studs for roller rocker arms, and .100 longer pushrods than what I have does that sound legit or is he just trying to get more money out of me? These pushrods only bent after I installed the roller rocker arms so maybe it has something to do with the studs or how I set the valve lash.

 

[VinceS427bb]

I just spoke with my machine shop and they said to come down like you said. Although he did suggest longer rocker studs for roller rocker arms, and .100 longer pushrods than what I have does that sound legit or is he just trying to get more money out of me? These pushrods only bent after I installed the roller rocker arms so maybe it has something to do with the studs or how I set the valve lash.

unless you checked the pushrods before the stocker-rockers were replaced=
i would suspect that they were already deformed.
were the pushrods stockers, or cheap aftermarket, or of a known quality/thickness (like 0.060" or 0.080")???
stockers and light/cheap aftermarket pushrods can flex and deform from valve float which can occur at relatively low rpms 4500-5800 if you have weak valve springs.
i don't know how you set the lash, but on a hydraulic FT-cam it is easy and if the engine doesn't run good afterwards you may have made an error...
guy at the machine shop sounds like he is trying to solve your issue, but all you may need is some quality stock length pushods....

 

[BillK]

My car was running fine before I .........

This tell me that you just made a mistake adjusting the valves. Changing to rooler rockers should not have caused bent pushrods. Only problem is .... did you hurt anything else. Pushrods dont usually bend unless something else hit too

 

[bornazen]

I bent one of mine after putting in a cam one size smaller than yours with new valve springs that had more pressure than the stock ones that I replaced with the new cam, cause in my estimations was keeping the stock pushrods in place, cure new .080 wall pushrods the size of elephants

 

[Steven69]

The pushrods were already in the engine when I rebuilt it, I checked them and they were straight. I am guessing I set the valve lash a little loose therefore maybe the pushrods were jumping around and landed on the side of the lifter causing deflection? How would I know if I bent a valve without pulling the head? Also, I have been confused on the options on pushrods...I have guide plates and the pushrods I have are 3/8 not sure of diameter though. There are some I saw that make the exhaust pushrods +.100. Do I go with those on the exhaust or just regular?

 

[Steven69]

And how thick of a wall should I go? .168, .080? I am guessing heavier duty since my last ones bent and the norm seems to be .080.

 

[Steven69]

Do Pushrod length depend on how big the lift in my cam is?

 

[Dave Birdwell]

Do Pushrod length depend on how big the lift in my cam is?

Depends more on the geometry of your valvetrain, best found with an adjustible length pushrod. There's a thread going right now that shows the best way to check geometry. I'll see if I can find it, or if someone beats me to the post. :thumbsup:

Here's one.... http://www.chevelles.com/forums/showthread.php?t=347797&highlight=miller+valve

And another... http://www.chevelles.com/forums/showthread.php?t=333336&highlight=pushrod+geometry

 

[BillK]

Steven,
One more time ....... if the engine was running fine, and all you did was change to roller rockers, then you DO NOT NEED any different pushrod than what you had. The roller rockers do not change anything as far as geometry goes etc. If you had the valves too loose, then you probably did not bend any valves. If they were too tight, then you need to do a leakdown test, that is the easiest way without pulling the heads, to see if there is anything drastically wrong.

And once again ....... "IF" the engine was running fine before, then all you need to get is another set of pushrods. The only way your machine shop can tell you otherwise is to look at the engine.

 

[Steven69]

THanks for laying it down simple for me, the whole "correct geometry" is a little more in depth than I have time for, and yes the engine was fine before, but I guess I adjusted the lash a little loose.

 

[Steven69]

I just got my intake and exhaust pushrods measured. I used a micrometer and the tube diameter was around .312 (5/16) and the tip was .309. Are these pushrods too small in diameter for my 454 and the .553/.573 lift cam?

 

[BillK]

Steven,
Mercruiser uses 5/16 pushrods in a lot of thier engines with at least that much lift, but I dont like it that way. I think you would be best off getting a set of 3/8" ones and guide plates to go with them. You have to buy pushrods anyway and the guide plates are not that much additional. That way you will be safe for sure.

 

[Steven69]

You are right for a total of eight I think its a little over $100, so not too bad. Better safe than sorry, I dont want to have to go through this whole thing again. So 3/8 .80 wall thickness it is. Thanks everyone