Dollars to donuts your clearances are to tight on those valves or those valves are bent. It doesn't take much.

 

everything in this motor is brand new and was assembeled at the machine shop so i dont understand why i am having trouble. I appreciate all of you giving me ideas Thanks

 

i have pulled the timing cover to be sure the chain was on rite and it is so the only thing left must be something wrong with the heads huh guys????

 

OK, when you turned it over and bent more pushrods...you had to be turning it awfully hard and ramming the valves into the pistons....or...you have more cam lift than you have rocker arm radial motion and you bound up the rocker arm on the stud and again were turning it over very hard to do damage.....or.....you smacked a valve into a piston and bent the valve stem and the valve is wedged tight in the guide and again you had to really exert extra force to turn so hard that you bent more pushrods. Now you know for sure that you have a major issue, its time to pull the intake and turn it over with no plugs in the heads and watch these 2 lifters for any lack of movement and also watch the pushrods for hitting things and also watch the rocker arms to verify that they are not binding up....now do this slowly and carefully. If you feel a bind, stop. Get a light and investigate. You need to find the problem. I bent a pushrod once on the second cylinder back because an intake bolt was to long and was against the pushrod. Started the new engine and within 2 min I heard a terrible valvetrain tick and took it apart and found the problem by slowly investigating. Take your time, and please try not to get angry just yet. It may be an honest error, God knows I have made a few.

 

allrite i will pull the intake and check things out tonite and see if i can find anything susspicious. I will let you know what i find out if anything. Thanks you guys Matt

 

who knows maybe it could be the bolts. I just find it really strange that it is happening on opposits cylinders 1 and 5 and it is the exhaust push rods on both sides that keep bending, who knows

 

What's the retainer to guide clearance at max lift? You said it had a mild cam, so maybe the heads can't handle it. Lots of cams have more lift on the exhaust side, which would explain why just the exhausts are bending. Maybe 1 and 5 are just tighter under the retainer than the others? Valvesprings might also be getting into coil bind. Are those two valves shorter than the others?

 

Also, have you checked the valve springs to make sure you're not getting into some coil bind?

Brad

 

The slot in the rocker arm could be hitting the folcrum at full lift also.

 

Allrite i pulled the heads tonite to see what i could find and everything looks fine. The valves look normal, so i guess tomorrow ill take the heads back to the machine shop and have them make sure they are fine, so if they are i guess the only other thing it could be is the cam????? Thanks guys Matt

 

I am not sure what you looked at, but you missed the problem. You put the good pushrods in these 2 cylinders and bent them by hand. At the point that they bent, you had to be exerting alot of pressure on your breaker bar.

You need to keep it assembled with heads, pushrods, and rockers together. You take the intake off, and if you need to, get a friend or your wife to come and help. You need to be feeling the force needed to be put on the bar while someone is watching the movement of the 2 springs, 2 pushrods, 2 lalves, 2 rockers, and 2 lifters.

You need to NOT bend more pushrods, this time be slower and more carefull. Roll it with the breaker bar with NO SPARK PLUGS and when you feel a bind stop. Now look at every detail.

You told us that you bent more pushrods last time you did this, that tells me you went too fast and jammed something up. Slow it down a bit and treat this like a mystery, you know the system, now trouble shoot it. Its really not to involved, there are only 5 parts on each cylinder that can be causing this....unless its piston to valve. The 5 parts are lifters, pushrods, rockers, springs, and valves.

Lifters could be tight in the lifter bore if there is a bur, this can bind it.

Pushrods can be out of the pocket on the rocker and being wedged to the side, this will bend it.

Rockers can be hitting the nut, or not have enough radial stroke, or be pushing the valve so open that the coils of the valve springs are all touching.

If the spring coils all get squeezed together you no longer have a spring, you are acting as a solid chunk of steel under the retainer. If the rocker is still trying to open you will without a doubt bend the pushrods.....this is most likely what you have going on. Be very suspicious of the valve springs binding.

Next is the valve itself, this could be bent and binding in the guide. I assume the valves are new or at least the guides are new and the shop installed the guides with proper clearance.

If all else looks good and you feel pressure on your bar....and the springs and all are good....stop. I wonder if your valve guides are correct? I doubt this is a problem, this is very unlikely...but its a rare chance that this is it.

If your at this point, I would take my bar and back it off a 1/8 turn and go up again until I felt the bind. I would do this back and forth about 4-6 times. This should take the edges of the valve and make a shiny mark on the piston...just do it easy, dont try to break/bend stuff....just try to touch.

If your here, you now need to yank the heads and look close at the pistons. Do you see a mark where the valve touched those pistons during the 4-6 back and forth movements? If you make it this far, I bet you will see it. Now you know whats going on...one way or the other, this should trouble shoot the valvetrain down to the exact issue.

Good luck.
Larry.

 

How big is your cam ?

 

When I reassembled my 351, the intake didn't seat correctly and leaked coolant into a couple cylinders. When I tried to start it, it bent 2 pushrods, broke off one of my screw in rocker studs, and snapped a rocker arm in half. My engine sat for awhile before I started it though, so the cylinders had time to almost completely fill up. Just a thought, you said your motor at least ran when you started it.

 

On my 1980, 370 rebuild I had a rough running motor after first assembly.
I thought it was timing.
But, low compression and exploratory surgery revealed bent push rods and exploded hydraulic lifters.
My rocker arms were not adjustable. But you can buy different rod lengths to repair wear on cam, lifting rod ends and rocker arm cups.
My parts were all new so stock length was used.
I found, by doing the slow crank of the crankshaft, that the valves were hard to move.

So I removed the rocker arm from the valve in question, threaded a short bolt into the rocker arm post.
Then used a claw hammer, with the claw around the bolt and the head against the spring end of the valve to gently try and compress the valve.
This confirmed the sticky valves.
I removed the heads and disassembled the valves in question.
They had a caramelized black residue, (I think it was a chemical reaction between different lubes and solvents used in the assembly process.
So I used a bit of alcohol to loosen the goo while I gently compressed, rocked/tapped the valve out of its seat.
Make sure you apply pressure directly down or risk bending a valve.

Once apart, I cleaned and lubed the valve and guides.
I re-assembled the valves and test installed the heads, old gaskets for proper spacing and clearance, to see if cranking the engine by hand would work.
It did and there were no bent rods this time.
Make sure you install and torque the rocker bolts in the proper order and when they are clocked to the proper position, (i.e. intake or exhaust, open or closed).
I followed a sequence in a rebuild book and made sure the engine and valve train parts would move after every rod install sequence.
After it was all verified, I disassembled and installed head gaskets and then repeated the whole sequence.
By seeing the various valves in the various modes as I clocked the engine, I was much more confident that my timing gear and distributor positions were correct.
Then I cranked the engine with the starter, no gas or plugs, to see if she would turn by starter.
Next she was all properly assembled and started. Sweet Success.
Also check and re-check firing order because I believe that exploding gas at the wrong time can place undue stress on valve components.
Be glad that the push rods are the weak link. Otherwise it could have been a valve, piston rod or maybe even a cylinder wall that yielded.