Pushrod length problem with pics

[knever3]

I changed the valve cover of my new to me 4.7L stroker, I was alarmed by the way the pushrods were sitting crooked on the rockers. I took pictures on how off center the pushrods are sitting in the holes in the heads. They are close to grinding on the sides! I repositioned them by turning the stud and they re-centered for now. For all I know they will just move around again. My guess is they are too long?

What do you guys think??

I don't know exactly how to measure the proper push rod length, I'm sure it has to do with TDC.

 

[O-Gauge Steamer]

Is that head reman'd?

The valves in the photos do not look to be perpendicular to the head. I.e. crooked as all get out. If the guides were improperly installed resulting in the valves being incorrect, that would explain the pushrods. As the valve seats are ground to match the guides, your head could be toast.

But, the push rod length is 9.640" to 9.660" for a stock engine or, an engine that has not been "decked" or has the alunimiun head. Dimensions are from my FSM.

 

[old_man]

First pull one of the offending valves and make sure the stem isn't bent. From the pix (which can be distorted due to the closeup angle) it looks like the guide is either not perpendicular or the stem is bent. From as bad as it looks, if the guides are not straight, you should be able to eyeball the heads of the valves and compare angles from cylinder to cylinder.

After that, look at the metal bridge between valves. Ever wonder why it is there? It's purpose is to hole the rockers straight, which is not happening. Are they bent, as in not holding the rocker mating "washer" parallel.

It appears that the head is off. Are there any dings in the head of the pistons?

 

[offroadordnance]

Alldata shows pushrod length as 9.5" for 1993 block and 9.64" for a 1998 block. Deck height is listed as 9.32" for 1993 and 9.45" for the 1998.

 

[gradon]

You should buy Comp Cams' 7704-1 pushrod length checker and see what length pushrods you need. Variables that change with the stroker/engine work are shaved head, decked block, cams with larger/smaller base circles, and rockers. I would not run it from the way your pics look. 96 head/block stock deck height is 9.450-9.456" and pushrod lengths are 9.640-9.660". I ended up using 9.602" pushrods for my 4.6l.

 

[knever3]

Thanks for all the feedback guys, I will look into this when I get a chance tomorrow hopefully. I was worried about this and I coudn't just ignore it and take a risk when I know it doesn't look right. So with that info how do I determine what length of pushrod I need without knowing how much they decked the block or head?

 

[GrimmJeeper]

post above yours has the info you need to find the answer.

 

[NorCalChris]

How much can you machine of the deck or block without needing new pushrods?

 

[cruiser54]

The bridges look tweaked to me just as OldMan suggested.

 

[Talyn]

Its not a push rod problem. The bridges are bent. It can clearly be seen in this image:

Take them off and bend them back. While tightening the bolt hold the vertical part of the bridge and torque the bolts to 21 ft-lbs.

 

[cruiser54]

Yep. They're bent.

 

[Talyn]

I just re-read the original post and realized it was ran like this. If significant material was removed from the push rod I would replace them. Once you fix the issue change the oil and filter. I would also make sure that the valve tips as still flat and don't have heavy wear on one side.

 

[knever3]

Ok, some excellent feedback from all of you. MUCH appreciated, I have not got the chance to pull the valve cover back off yet (got called into work lately) but the bridges you mention do seem bent and they move when I try to loosen or tighten the hold down bolts. They seem to have no affect to hold the rockers in place (side to side wiggle).

Question:

When tightening the rocker mounting bolts should you put that cylinder at TDC to take the spring pressure off them first? I have never done this on GM engines but they don't have that bridge that's supposed to locate them. How about getting new bridges? I don't feel like bending them back is going to solve this.

Also in another related question I don't know what kind of cam they installed so should I run high zinc type oil that I have been reading about? I don't want to ruin the cam if I assumed otherwise.

Thanks again!!!

 

[old_man]

No need to do that, just make sure that when you tighten you don't twist the bridges.

 

[GrimmJeeper]

Also in another related question I don't know what kind of cam they installed so should I run high zinc type oil that I have been reading about? I don't want to ruin the cam if I assumed otherwise.

Thanks again!!!

yes, run a high zinc oil. flat tappet cams need the zinc content to keep from trashing the lobes and the lifters.

 

[Talyn]

You don't have to bring the cylinder to TDC w/ valve closed. But if you do have a valve open you will want to start tightening that one down first. There will be some side to side wiggle in the rocker, but those are clearly out of wack.

 

[knever3]

yes, run a high zinc oil. flat tappet cams need the zinc content to keep from trashing the lobes and the lifters.

Will high zinc oil ever hurt an engine if the cam is not a flat tappet like you mention? How do you KNOW for sure it's a flat tappet cam? I thought you had to adjust the valves every so often on flat tappet cam type engines. I like Castrol oil and to my research they only sell synthetic 20w50 oil which seems too heavy for a regular motor.

 

[cruiser54]

You're thinking of solid lifters not hydraulic lifters like we have. No adjustment needed but it's still flat tappet, not roller.

 

[knever3]

So if I understand correctly what was the original cam in our engine? Why do I have to switch to a different oil? Is there a Castrol product out there I can use with this engine? Thanks for the clarification on the cams.

 

[cruiser54]

Flat tappet hydraulic. The high zinc oils were required more for break-in than anything. If you are not breaking in a new cam, you can use pretty much what you like. The general consensus is that Shell Rotella has higher zinc and works well. I use it in everything.

Know what's just as important if not more important at this point? What brand of oil filter you use. Alot of these cheapie oil filters have a pi$$ poor anti-drainback valve in them and they empty out every time you shut the engine off. Then, on restart there's no oil immediately available to lubricate your engine's vital parts.

What brand are you using?