kgkern01

I'm instaling ported and milled heads with Impala gasket and 1.7 rockers and need to determine correct pushrod length, i have an adjustale pushrod and dial caliper, cylinder 1 is at TDC with lifters on base circle. Whats the best way to check various pushrod lengths?

kgkern01

Tell me if this method is right, I set the lifter at zero preload, then turned the crank by hand 2 revolutions and checked the sharpie mark I put on the valve tip. By this method it looked as if 7.100 or 7.050 would be the correct pushrod length based on the markings on the valve. Does this sound right? Both of these marks looked similar, which rod should I go with to err on the side of safety? I have to order these tonight to get them in by this weekend.

Heads are milled at least .020 but not sure if more, and using .029 Impala head gasket and 1.7RR.

mattbailey

7.100 sounds closer. You may get away with 7.125-7.150 Mine are 7.100 with a zero deck, milled heads(alot), and stock gasket. Make sure that the lifter is pumped up also.

speed_demon24

You can't check it that way without a solid lifter....

kgkern01

I heard you can make a hydrolic lifter a solid, how is this done?

2QUIK6

There is no one on here that can tell you what length should be correct..it depends on waaayy too many things....gasket thickness, rockers you are using, and cam base circle...you have to measure it and it should be somewhere around 7.2 +- .3 or so.

To make a hyd lifter solid, take out the retainer spring and take the lifter apart. Take a bolt and cut the head off then grind it down and insert it into the lifter and reinstall the cap and retainer spring, they should just barely fit back on, if not, grind a little more but don't go too far.....this makes the lifter not able to compress.
If its a lifter you'll be using again, make sure to keep it clean.

12SCNDZ

A better alternative to using a solid lifter is available. You need to pull one valve spring and install a very low tension spring in it's place. Doing so will keep the lifter plunger from moving when the engine is rotated.
I came up with this solution because of my use of Morel link bar hydraulics. I have to pull the head to get the lifters in/out.

Frank
CPT

mdacton

the low tension springs are the easiest way to do it.....I use the ones that are in my cam degree kit

JP95ZM6

I tried using the light springs first, but I couldn't get a very clear pattern that way.

With intake off, I found that it takes several minutes for my stock lifters to bleed down the first couple of mm's under valvespring pressure, and when simply turning the engine over there was no noticeable leakdown. Once bled down they stay that way until I prime the motor again, so it was easy to double check by feeling for easy lifter freeplay, which was noticeable on the lifters that had been under valve pressure for a long time.

I checked the recommended 7.150 pushrods this way, and got good patterns. Is anything wrong with this technique with a fully pumped lifter, considering the slow leakdown? It is admittedly more error-prone, but seems to work fine if you are careful about it. I can see having a few thousandths error, but when pushrods come in .050 increments, that seems negligeable.

mrseven

Found this article on lifter preload, maybe this will help. Pulled from:

http://www.zzperformance.com/grand_p...les1.php?id=50

"All said and done you need to add up the changes in head milling, block decking, head gasket thickness, pushrod length, valve tip height, camshaft base circle lobe diameter, and rocker arm type. This will allow you to calculate the length of pushrod needed.

To check for lifter preload or lifter squish you need to first get to zero lash. Turn the engine over so that one valve on a cylinder is open. Because one is open, you know the other is closed, meaning the lifter is sitting on the base circle. With that lifter on the base circle loosen the rocker bolt and then retighten with one hand while spinning the pushrod with the other. This way you can tell when everything first makes contact (the valve is touching the rocker tip, the pushrod is touching the rocker & and lifter and the lifter is touching the cam). At this point of first contact you are at zero lash. Everything past this point is lifter preload. Continue to tighten the rocker bolt until the bolt hits its snug point. This is how much lifter preload you have. Each 1/2 turn of the rocker bolt is ~.050 of lifter preload. Your goal is to have between 1/2 turn and 1.5 turns if you have stock lifters or 1/8 turn to 3/4 turn if you have Comp lifters. As you can see the stockers have a lot more room for error."

Good luck

kgkern01

Made a lifter solid and checked again, seems that 7.100 is about perfect so thats what I ordered.

SS MPSTR

congrats. that's the way I did it too. keep us posted on how she runs after it's all together.