AllCammedUp

I've read/searched/read again on this subject, and I think I've got a good handle on it, but I want to throw my numbers out and see if everyone is in agreement here:

I've got TEA Stage II 5.3L heads. These are milled 0.010". All else being equal, I'd need a .010" shorter p-rod to maintain stock geometry.

My TR224 cam has a .030" (that's the commonly-used #) smaller base-circle diamter than stock, so I'd need a 0.030" longer p-rod to maintain stock geometry.

Put the two together, and my optimal p-rod length is as follows:

Stock - Heads + cam = ideal

7.400" - 0.010" + 0.030" = 7.420" pushrod.

Is this correct? Reason I'm asking is that I've currently got comp cams 7.400" p-rods and the yella terra's are installed w/o a shim. I was able to get 22 lb/ft w/ a hair over 1/4 of a turn past 0-lash. If I install longer p-rods (lets pretend I could actually buy 7.420" p-rods), then would I be able to get more turns before I get to 22 lb/ft, or less turns?

If I install the spacers that come w/ the yella terras, will that serve to effectively 'lengthen' or 'shorten' the p-rod in relation to everything else? It was my experience that installing the spacers (washers) caused me to need less turns past 0-lash to get to 22 lb/ft. Is this because the p-rod was being treated as longer or shorter w/ the spacers installed?

So, in order to get more turns (like 1/2 or 3/4 past 0-lash = more preload), should I have a shorter or longer p-rod?

Also, what is the effects of not running enough preload or too much preload? With hydraulic lifters and not running enough preload, do you leave power on the table... what is the long-term effects on the lifters to run w/ too little preload?

Sorry for so many questions in one post... I've been thinking a bit about this, and wanted to get it all pulled together as a scenario rather than a bunch of one-off questions.

Thanks!!

mobius

aren't the yellows adjustables???

Bink

If I install longer p-rods (lets pretend I could actually buy 7.420" p-rods), then would I be able to get more turns before I get to 22 lb/ft, or less turns?
>> Less turns
If I install the spacers that come w/ the yella terras, will that serve to effectively 'lengthen' or 'shorten' the p-rod in relation to everything else? It was my experience that installing the spacers (washers) caused me to need less turns past 0-lash to get to 22 lb/ft. Is this because the p-rod was being treated as longer or shorter w/ the spacers installed?
>>>If you put in a shim it INCREASES distance between the rocker arm and lifter...so it will require more rotation , in your case, to meet 22 ft-lbs.You'll have to go through more rotation to compress the internal lifter spring and thus meet the required 22 ft-lbs

So, in order to get more turns (like 1/2 or 3/4 past 0-lash = more preload), should I have a shorter or longer p-rod?
>>>Shorter rod or..... put in a shim



>>>I think it would help to think about how a Hydraulic lifter works .

Bink

AllCammedUp- maybe this lifter link will help. Hyd lifters and preload
Check out the 'Pedestal shim info"Good Luck and HAPPY 4TH!!!!!!!
joel(Bink)

Tin Indian

Question: If I install longer p-rods (lets pretend I could actually buy 7.420" p-rods), then would I be able to get more turns before I get to 22 lb/ft, or less turns?

You would get more turns with a longer rod. (more preload)
__________________________________________________ ________

We measured Thunder Racing's 7.40" rods with a mic. They actually measured .015" longer than the stock rods. I believe these are the same rod as the Comp Cams 7.40" rod you are using. If so, your combo would be within .010" of the stock geometry [IF] you had used the stock rocker arms. And thats very good.

Now, you are using Yella Terra rockers, so that has obviously changed things a bit.

You state than right now you only are getting about 1/4 turn of your rocker arm bolt past zero preload in order to achieve the required torque on the bolt. Thats not really enough, and that would indicate that you need a longer rod in order to get more turns from the bolt. Pushrods come in .050" incriments, so I would say you need a 7.45" rod (.050" longer than the 7.40" rods you now have).

Installing shims under the rockers will act as if you have shorter pushrods. Thats will have the oposite effect of what you really need.

Your preload seems very strange to me. If Yella Terra is telling you to use the supplied shims under there rocker arms, that would indicate that the company believes the use of Yella Terras needs a shorter pushrod when there rockers are used (all else being equal). In your situation, you need a longer rod. Are you sure the valve was completely closed when you checked the preload?
I would turn the engine a couple of times and check another valve to see what you get.

Ron,

AllCammedUp

The only adjustability to the YT's is either leaving the shim in or out.

Thanks for the link, blinks. I'll give it a read.

Ron,

The YT manual states that the shims aren't to be used unless the proper preload cannot be obtained and it becomes necessary to 'cheat' a little bit. The YT's do seem to want a different amount of preload, as their instructions state around 1/2 to a full turn of preload is ideal, I believe, and that's not what the stockers want, based on what I've read here.

I am 100% positive I had both valves closed, as I turned the motor over 3 or 4 times to make sure I was gold on that before I unbolted everything.

If I did have 7.450" p-rods, then that would put me @ .030" over w/ the yella terras vs. .010" over w/ the stockers, and that seems like a worse position to be in, IMHO. ARGH!

However, I really don't feel like I've got enough preload w/ the current setup... if I do, I'm on the fringe, and the stockers were much closer to the 1.5 turns or so that everyone states is 'gold' using the stock rockers.... it just seems to me like I was better off using the stock rockers, but I'm trying to justify the installation and make it right!