Hey everyone I have a quick question. If I have undecked heads, block, factory cam, factory head gaskets, factory lifters, and factory rockers. Why are my srock 7.400" (measured closer to 7.395") pushrods way too long. When I put a cylinder to tdc and torque the rocker to 22 ft lbs both valve springs compress well over 1/8".

I understand when I do things that will change the distance between the rocker tip and the can base circle but I have not. I have a adjustable pushrod checked coming so should know soon what size I need just confused as to what is throwing off the measurement.

Thanks
Shane

 

The cyclinder you are checking is on the overlap stroke I would bet. If it is on the overlap strike they will both be open a certain amount. Rotate the crank 360 degrees and try it again.

 

Also, do they initially compress and then the valves close or do they stay open? When you first torque the rockers in place, they will open the valves a bit until the lifter bleeds down. That may be what you are seeing assuming you are doing this by the correct procedure, i.e., both lifters are on the base circle of the cam.

 

Both valves are closed. Confirmed with a dial indicator on the top of the spring retainer. If I torque the rockers down all the way if I turn the motor over very slowly by hand it stops on the compression stroke of that cylinder. Assuming its hitting the valves cause they are open. When I back the rockers off so the valves are closed engine turns over no issues.

 

They stay open

 

Like vettenuts said, I've seen valves open about an 1/8" and then close when the lifters bleed down. Seems to take a good 15-20 minutes for the lifters to bleed down. This is assuming you're working with used lifters and haven't taken them apart to remove the oil. When you tighten the rocker can you also see the pushrod moving down a bit?

 

Why are you concerned with your valve position? That is a secondary action of the lobe position of the cam. Put the cam on the base circle and remeasure.

 

I am concerned because I have stated multiple times that the cam is on the base circle. When I checked. I just don't see what about my combo would cause this.

 

I'm not sure what you're actual goal is, but the valves are not going to be closed at TDC. You're going to be in the middle of the overlap between the intake and exhaust lobes. Therefore, you're not on the base circle of the cam when you're making your pushrod measurement.

 

I am checking at the top of the compression stroke which both valves are shut

 

Missed this post. This is your answer.

 

I would understand if I was measuring at TDC between the exhaust and intake where the overlap is but I am measuring at TDC between the compression and power strokes. How are the valves not closed right now?

 

If you're sure the lifters are completely bottomed out and you're still not able to rotate the crank 2 complete revolutions, the only possibilities I can think of are that your pushrods are not actually 7.400", or your cam is not degreed properly.

 

Without turning the engine, check the pushrod lengths for #6 cylinder.

 

Are the pushrods seated correctly on the lifters...?

Are the rocker rails installed (underneath) the rockers...?

 

How did you determine the cylinder was at TDC firing stroke? Also, please don't find this insulting but it has happened before to a few good people who had a similar problem, are the stock aluminum rocker stands in place?

If using the dots on the sprockets, the cam dot must be at 12 o'clock for cylinder #1 and not at 6 o'clock.

 

Easy way to do this is to rotate the crank until the intake valve is open all the way on cly 1 and check the exhaust pushrod on the same cylinder. Then rotate crank until cylinder 1 exhaust valve is open all the way and check the intake pushrod on the same cylinder. Start on another cylinder of choice and repeat until all 8 cylinders are done. You might need different length pushrods on intake and exhaust.

 

The aluminum rocker stand is in place. I used my adjustable pushrod and it is measuring in at 7.290". I am rotating the engine while monitoring the cylinder pressure with my finger. When the intake rocker closes I put my finger in the spark plug hole. Rotate the crank ~180* until I feel the cylinder stop building pressure (just past TDC). With the adjustable pushrod checker inplace I can rotate the engine by hand and the rocker never gets loose with it set at 7.290"

I am just confused what is throwing this off. Everything in this combo tells me that the factory length pushords should work since it is a factory setup and nothing has been changed that would change the distance between the center of the cam and the pushrod cup in the rocker arm.

 

If the 7.29" pushrod is perfect, it should lift the intake valve ~0.17" and then the valve will close after 15-30 minutes because the valve spring pressure will slowly push the plunger in the lifter down ~0.100".

 

Could the lifters be messed up? At TDC between compression and power strokes I can see the pushrod for the intake is much higher than the exhaust one and I have swapped both pushrods and rocker assemblies. #1 exhaust measured fine...... I have only been checking #1 intake. #6 exhaust is fine. #6 intake is not