JohnRR

Hi all,

I installed the Katech Torquer 110 cam, the heads were milled .030 by WCCH, and I'm using the stock head gasket. The problem I'm having is determining the proper pushrod length. With the intake and exhaust lifters on the cam base circle (AIC + 30 degrees), I adjust the rocker bolt until I get zero lash. Then, when I tighten the rocker bolt down, I consistently get 2-3/4 turns on the intake, and 2 turns on the exhaust.

2-3/4 turns sounds excessive to me. Can someone please tell me what is optimal?

When I install an adjustable pushrod, and set it to zero lash (no lifter preload) with the rocker fully tightened, the adjustable pushrod is about .200 shorter. Add about .075 preload and it says I need pushrods that are .125 shorter than stock. Again, this sounds excessive to me.

Please help me figure out what am I doing wrong?

Thanks,
John

Vito.A

There are several issues here. The first is the hydraulic lifter plungers may not be at the top of their travel. So when you add .080" preload they end up lower or at the bottom of their travel. Are these new GM LS7 lifters?


The second issue is pushrod manufacturers use gauge length to account for the oil hole and end radius. This makes it difficult to measure a pushrod with calipers and get a proper length. An easy method is to purchase multiple sets of pushrods. Your engine will probably use 7.725" or 7.750". Some of the vendors will allow you to purchase two different length pushrod sets and return the unused set.


The last issue is it's difficult to locate the cam base circle. Turn the engine to #1 TDC. The trick is to determine if #1 is on the compression, or exhaust stroke. You can figure this out by checking the #1 exhaust valve cam lobe. If it is on the base circle, its on the compression stroke. If not, then you are on #6 TDC and you can skip to the second group below and then rotate 1 turn and come back to the first set.


Exhaust valve rocker arm 1, 2, 7, and 8.
Intake valve rocker arm 1, 3, 4, and 5.

Rotate the crankshaft 360 degrees.

Tighten or check following valve rocker arms:
Exhaust valve rocker arm 3, 4, 5, and 6.
Intake valve rocker arm 2, 6, 7, and 8.
Hope this helps.

JohnRR

The lifters are the original stock LS7 lifters. I found the cam base circle by putting my fingers on both of the #1 pushrods and rotating the crank. I could feel the exhaust open and close. Then I could feel the intake open and close. Then I rotated the crank approx. another 30 degrees. If the lifter pistons were not at the top of their travel, then I would have less turns on the rocker bolt.
Is it common for the intake and exhaust lifter preloads to be so different? It makes it look like the intake and exhaust should have two different lengths of pushrods.

Confused,
John

Vito.A

No, the LS7 should use the same length pushrod for both intake and exhaust. Other engines like the Big Block Chevy use two different lengths (Big Chief cylinder heads use three different lengths).
Choose a different cylinder and try again.

Josh B.

I did a K501 cam with WCCH heads milled .030". At .070" preload, my measurement was 7.752 (back in Feb). Just yesterday I measured a friend's build with same cam and milled heads, his came in at 7.757.

I ordered 7.750" BTR 3/8 PRs for both. My lifters have been relatively quiet in operation, not that sound is really indicative of anything. I have heard engines that have over .100" preload and my lifters are definite "louder" at their katech's recommended .070" preload. I would bet that the same 7.750 measurement would be expected on a Torquer cam with heads milled .030". Hope that helps. Vito is right on the money about measurements.

Josh B.

Is it possible you didn't install the lash caps? That would throw the measurement way off...

JohnRR

The lash caps are all on. If the lash caps were left off, then the preload would be less.

All the measurements I checked are on the driver's side. I'll check the passenger side and get back with more data.

Thanks all,
John

Josh B.

Ah, my mistake for not reading closely, I only noted that you had intake/exhaust differences. .125" shorter is not common with what I have seen on the two engines I measured.

The only thing I can think of is if the lifter is not seated on the cam. If the lifter is dry enough, as well as a dry lifter tray, the lifter will "feel" seated even when it takes a solid shove to seat it on the cam lobe, such is the friction of the lifter tray, again, if it's dry. Doubt that's it, just thinking of what that could be, .125" is a lot. Unless they seriously milled your heads beyond the requested .030", but that's a long shot.

JohnRR

Here's a followup on the pushrods I ended up with:
The Intake pushrod is 7.725" long with 1.6 turns preload.
The Exhaust pushrod is 7.750" long with 1.4 turns preload.

I still have to install the intake and then get a dyno tune.

John