Hello, so today i installed my new heads that are ported and polished 862. My old ones were the 706 that were cracked. I also installed some pac1218 springs with felpro headgasket. I also put in a texas speed stage 2 truck cam 212-218 .600 112lsa. Ive measured my pushrod length both exhaust and intake and i get 13 turns with the pushrod checker which starts at 6.8 plus 13 turns at .050 each turn puts me at 7.45 before preload and after .050 preload it puts me around 7.5. Does that seem good? Ive tried it both hand tight and torqued down to 22ftlb and it stays the same. I installed the old pushrods and they are waaay to loose. So they arent the stock length thats forsure. Truck is a 04 silverado 5.3

 

Were your previous heads milled? Stock length is 7.400, BTW.

 

i dont think so. My current 862 heads are just resurfaced. Isnt stock pr 7.385? I compared them with my comp cam pr checker at 11.75 turns and they are identical which is 7.385ish

 

What is the base circle on this cam?

 

Not sure. Here i took a pic of the specs

 

I was reading that a bigger lift cam will require a longer pushrod because they have to grind the base circle of the cam to get the longer lift on it.. seen in this vid.

 

Seems longer than I would expect.

Did you do this by the "twist the push rod" method? If so, that's probably why. It PRACTICALLY ALWAYS produces this particular error, because of how subjective the "feel" of twisting the push rod can be.

Zero lash is when all the VERTICAL play in the push rod and rocker are taken up, but WITHOUT depressing the lifter plunger. Remember, VERTICAL play. Looseness, rattling, freedom to move. "Twist the push rod" usually allows the lifter plunger to be partly, or even fully, depressed, before it becomes noticeably too hard to "twist" it.

Correct technique is, install the push rod, set to the low end of the range you expect it to be within, and check for VERTICAL play in it. VERTICAL PLAY ONLY. If you install it, and it still has VERTICAL play, remove the rocker, adjust the push rod out ½ turn (that being the increment you can buy push rods in ... .025"), re-install the rocker, and check again for VERTICAL play in the push rod. Repeat until all VERTICAL play is removed, without depressing the lifter plunger AT ALL. The exact length for "zero lash" then, is between the incremental setting where it still DID have some VERTICAL play, and the length at which all VERTICAL play was gone. You can tweeeeek on it in finer increments if you want but it hardly matters since you can't buy push rods that way anyway unless you're willing to spring for $$$custom length$$$ ones which don't make sense on a stock motor like that with a mild street cam in it. My suggestion would be, purchase ones that are .075" longer than the last adjustment increment that still left VERTICAL play; that will guarantee that your preload is between .050" and .075", assuming that all 16 valves measure the same. I like to measure both I & E on the 4 corner cyls: that way if there's either front-to-rear variation or a difference between the 2 sides, I have a good chance of spotting it.

Notice that AT NO TIME did I ever say ANYTHING about "twist the push rod and feel for resistance". That is because it is UNRELIABLE. The indicator you need to use to determine when you have reached zero lash is VERTICAL PLAY in the push rod and rocker ONLY.

 

Yes i only checked for up and down play. At 13 turns exactly wad the sweet spot. At 12.75 it had ticking at 13.25 it was to tight.

 

Well, if that's what it measured then, that's what it is. Might "seem" suspiciously short but that's why we measure, no?

 

Yea i checked on different cylinders and its always 13 turns. I emailed texas speed to know what the base circle of my cam that i got is since i already have almost everything boltednyp. Hopefully they'll give me an answer.

 

Checked the 13 turns its dead on 7.45

 

Hmm. Ill check the pushrods when they get here.
The stocks measured in at 7.36 i rechecked the 13 turns an its exactly 7.46. so i guess thats where the extra .1 came from?

 

Can't measure push rods with a caliper.

Well, you can; you just won't come up with the same thing as they list in the catalog. The "specs" assume that the entire end is spherical; but since there's a hole there, which takes away some of the sphere, they'll always "measure" shorter than "spec". Most if the time the difference is in the neighborhood of .015" but it could be something else depending on the dia of the oil hole.

The threads on the 7702 are .050" each (after all it's ¼"=20 threads), and it's 6.800" fully screwed in. That's more accurate, as far as matching to a catalog "spec", than anything you'll come up with using a mic.

You can "smell test" your results by putting it together with a stock one and seeing where it comes out. Stock length, by the aftermarket spec method, is 7.400". By your measurements there should be around .050" of free play with a stocker. Exactly 12 turns on your 7702 should very closely match it.

 

If you order pushrods through Summit they send a (free) return shipping label with the order. I second guessed my measurements (7.525 aftermarket heads) and came up just a titch short. Ordered a new set and sent the first set back for a refund, no questions asked. Double check final preload using the rocker bolt turn method for piece of mind.

 

I got them from texas speed. Hopefully i got the right ones lol