I have the adjustable length checker and have tried my best to figure it out but im out of ideas and am about to let the machine shop figure it out for me. I have a flat tappet hydraulic xfi 268 comp cam in a 355 with dart pro one heads (the earlier style 200cc intake runners 64 cc chambers). Im using the springs that were in the heads when they were assembled. my rockers are 1.6 magnum full rollers. I have very thin head gaskets and a slightly decked block (just to clean it up). Is there anyone running a similar or the same combo that can give me a length to get me close? If this was a solid lifter motor i would have no problems finding the length but since its got hydro lifters they are compressing and i cant figure out the reading. I kno there are test springs that can be used but the heads are already bolted on permanently so i dont want to go backwards. Any help would be greatly appreciated.

 

You're either going to need a solid lifter of the same length (maybe get another one of what you have and fix the plunger in place somehow) or take the springs off and put lightweight checking springs in place. You dont have to take the heads off to get the springs off, its just like the procedure for swapping valve stem seals. That is what I would do, get a couple springs off. Short of that, hopefully someone else has the same combo and can at least get you close.

 

You need to remove a spring and install a light spring. I use one I bought from the harware store. You don't have to remove the head to swap the spring. Just use a holding fixture to charge the cylinder with compressed air. Then use a soft hammer, striking gently on the retainer, so the locks will come loose. Now use a pry type valve spring compressor to compress the spring. You can buy this compressor cheap at most parts stores.

Once you have the light spring in place with the adjustable push rod checker, adjust the length until the angle between fully closed and fully open is evenly split. You want the rocker to be parallel to the retainer, at 90degrees to the valve stem, when the valve is at mid travel. Set up this way, you get the most lift at the valve. During this process, be sure the lifter isn't collapsing. It's okay to use a solid lifter for the length checking process. As long as it has the same height as the hydraulics you're using. Though it's not necessary if you use a light enough spring.

 

A solid lifter or a hydraulic lifter modified so that it's solid is the best way to go. Unless you have something weird, the height of both styles of lifters should be the same. SBC pushrods are all the same size for solid and hydraulic cams. Roller cams may be slightly different depending on the style and year.

The adjustable pushrods can only take so much force. The open pressure on SBC springs isn't very much but there's always the chance of bending the checking pushrods. That's why it's recommended to use lightweight checking springs. On my engine, the valve spring open pressure is around 800 pounds. The checking pushrods will break long before a valve opens. My valve springs have seat pressures higher than some SBC springs have open pressures.

As mentioned above, lightweight springs don't need to be brand name springs. A hardware store spring can work just fine. They only need to be long enough and strong enough to hold the valve closed so that the retainer and keepers don't fall out. A modified compression tester and some sort of air compressor can be used to fill the cylinder with air long enough to swap out the valve springs. If possible, make sure the piston is exactly at TDC. The air pressure won't push the piston down into the bore and if you accidentally do something wrong like losing air pressure before the springs are swapped, the valve will only drop down until it touches the top of the piston.

 

I borrowed a solid lifter from my machine shop to use but the seat where the pushrod sits was lower than my hydro lifters from comp. Im not sure what brand it was.

 

Add the difference in height between the two to your pushrod length then.

 

Tried that and came up with a number that is WAY too big so i did something wrong.

 

Im sorry, I forgot about this thread. Did you get it figured out?

 

No worries. I actually ran into another problem and i "think" i have it solved. I thought i needed a new oil pan because of the fitment with the one piece felpro gasket that i got for it but it turns out there are two types of 2 piece gaskets with the difference being how thick the gasket is between the timing cover and oil pan. Well i got the thin one and needed the thick one.

As for the pushrod length..my buddy had a solid lifter that he used to find his length so im going to snag it from him and try finding my length again..starting with a stock rod. I'll update this post if and when i figure it all out. Thanks for checking in

 

Ok so bringing this back. I got a whole bucket full of used lifters from my buddy and every one of them were hydros. So...i modded one to be solid and set the seat where the pushrod sits to the same height as the lifters that are going into the motor. I first threw in the stock pushrod and checked the geometry by using a sharpie on the tip of the valve and taking note of the pattern the rocker left. With the stock pushrod the pattern was slightly towards the outside of the head (towards the exhaust side). Is this what i should be looking for? I was trying to figure out where midlift is and couldnt. The only thing i could think of is marking the lifter at full lift and dividing that mark in half to get the halfway mark.

 

Don't worry about where the mark lands on the valve stem tip. That DOES NOT MATTER (Comp's WRONG instructions on their site notwithstanding).

What you should REALLY be looking for, is the NARROWEST POSSIBLE mark on the valve stem, WITHOUT regard to where it falls. This indicates that the rocker tip is doing the MINIMUM amount of sliding across the tip. Find that length; then order the next length SHORTER than this, whatever it is. If it lands right at the .050" dividing line, go to the next increment shorter. The idea being, you want the rocker tip to be "biased" toward pushing straighter on the stem when the valve is at full open, i.e. when there's max force on the whole system, rather than being straighter at the seat when there's less force on the system and then having it at more of an angle when there's the most force on everything.