Replaced Heads 96 4.3
 

Hey,

I just finished replacing the heads on my son-in-laws 96 blazer. I did not use the same heads that was on the engine. Now for my question, I had everything ready to try and start the engine and when I hit the key the engine spins like it has no compression. I feel like maybe the valves are not closing all the way. It has screw in studs, which you just torque the nuts to 22 foot #s. If these heads had been grind any at all this could cause a change in the valve opening. What do I do to get the right setting for the valves? First timer on this type heads. Thanks for any info. Greg

RE: Replaced Heads 96 4.3
 

The first thing I would do is to pull the valve cover and loosen the rocker arms on one cylinder. Then do a compression check on that cylinder.

*EDIT* - But the more I think about it...

With screw in studs and no support beam, you are supposed to go to zero lash then a 1/4 turn if I remember right... Basically, tighten the rocker while spinning the push rod until you feel resistance, then another 1/4 turn and you've set the preload on the hydraulic lifter.

The factory rockers have a support beam that holds all of the rockers on one side and have bolts that hold everything in place. This setup requires the 22ftlb torque.

RE: Replaced Heads 96 4.3
 

From what I read, there is not adjustment on these rocket arm nuts. They just tighten all the way down to the offset on the stud, and torque to 22lbs. I will pull everything back apart and check the compression.

RE: Replaced Heads 96 4.3
 

With screw in studs, you have changed from stock. The stock rocker arms have a pedestal support beam that goes under the rockers. The rockers are then set on top and a bolt down through both the rocker and the support beam.

Here is a picture of the stock setup:
https://i11.photobucket.com/albums/a...r_pedestal.gif

RE: Replaced Heads 96 4.3
 

Kyle,

We took the rockets offthe oldheads and put on the recon. heads we put on the truck. They only had a nut, a roller inside the rocket arm and the rocket arm, nothing under them. Here is a pic of one of the old heads.
http://i141.photobucket.com/albums/r...n/heads001.jpg

RE: Replaced Heads 96 4.3
 

FYI,
I spoke with a machine shop this morning about this problem. He told me they have to check the valve height and if the valves are to high they grind them down. If they are to low the replace them. It is the only way to make sure the valves are set right with these type screw in studs, with no adjustment. Thanks for all your help. Greg

RE: Replaced Heads 96 4.3
 

That must be a throw over from the older CPI motor. Being a '96 I can assume that your head arrangement was a left over. Sorry about that. Weird things happen in change over years though.

Looking at the pictures, yes, it does look like your screw in studs have positive stops similar to the style used on the later SCFI motors I posted earlier. It definitely looks like the only way to adjust this would be to either grind down the valve stems or get different pushrods. Have you checked that the push rods are proper? Where on the valve stem does the rocker arm contact? It should be slightly off center towards the rocker arm.

When you said screw in studs, I pictured the modification that many people do for after market rocker arms - screw in studs that add adjustability.

RE: Replaced Heads 96 4.3
 

Okay guy's,

Pulled the valve cover, and plugs. Backed the number 1 cylinder rocker arm nuts off 3/4 turn. With a pressure gauge I get 140 # pressure, so this tells me the valves are not closing. I have come up with and idea, what if I pull the studs, buy some shimes (.025 to .035) and find the rightheight with the nut torqued to 22 foot lbs. and get the 140 #s pressure. Locktight the stud into the head. What is your thoughs?
Greg

RE: Replaced Heads 96 4.3
 

This would be very difficult to do while maintaining the proper preload on the hydraulic lifter...

RE: Replaced Heads 96 4.3
 

Kyle, the speed shop said the same thing.

Okay, trying to find the right size shims to shim up the screw in rocket arm studs is not an easy task. I went by Street & Strip Speed Shop and they had adjustable screw in studs and self locking nuts for a 4.3 chevy. $70.00 bucks