Lifter preload, EZ way to set
09-17-2007, 10:51 PM
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Lifter preload, EZ way to set I just finished installing the Yella Terra #6645 on my 1999 C5 a few hours ago. AFR 205 heads, stock head gaskets, heads cut 0.028”, 7.400” push rods, Comp 224* 0.580” cam, stock lifters, PRC Ti retainers and double springs.
Purchased from New Era, $415. There are several grades of rockers from Yella Terra, the “Easy fit” direct replacement for original rockers and the Platinum/Platinum Plus. Their web site give some details. www.yellaterra.com.au
I had to chuck all the rocker bolts into my lath to remove a few thousands from the bolt shank to make the bolts fit into the rocker shaft holes. I tried taping a few in, some bolt shanks were so tight that I couldn’t tap them in with a machinist brass hammer. The few that would tap in were so tight that I couldn’t feel the threads engage in the AFR heads and they started to cross thread. If you don’t have a lath, chuck the bolts heads in an electric drill and run a file over the shank while they’re spinning. The rocker shafts are hardened, I couldn’t de-burr the holes with a scraper or a rat-tail file. The holes could have been finished with a smoother surface. The rest of the rockers are beautifully machined and all the tolerances that I could check with a dial caliper were spot on from set to set.
I had to use the supplied 0.048” shims to get a ½ turn pre load. My 1999 rocker bolts are 20 tpi or 125m thread. 20 tpi equals 0.050” travel for one turn of the bolt. They must be an oddball metric size, they were larger than 8m125 and smaller than 9m125.
I couldn’t find a midget to hold the push rods to tell me when they stopped spinning. I could only get one index finger on one hand and maybe the little finger on the other hand on a push rod. The push rods lie to you, they feel like they’re turning and they aren’t as I marked them with a drop of white paint, I could not get an accurate zero setting using this procedure. Maybe this is why some have a problem with their installation.
What I did and I thought it worked great was put a cylinder at TDC and tight down on the rocker bolt with a 0.013” feeler gage until you couldn’t move the feeler gage and back off the rocker bolt until the feeler gage just moved. I used a 0.013” feeler gage because this is ¼ turn with the 20 tpi rocker bolt. (Well, close enough!) I removed the feeler gage and went ¼ turn in for zero preload on the lifter. If you can push down on the push rod with your thumb, the lifter has collapsed, in this case just watch the rocker when you pull the feeler gage out, if the push rod end of the rocker moved up, you were compressing the lifter internal spring so do it over again until it doesn’t move. I did this on both banks incase there was a tolerance stack, both banks came out the same. I got an acceptable wipe pattern on the valve stem. Yella Terra instructions call for ½ to ¾ turn past zero preload.
With my head, gasket, cam and push rod length, I had to use one 0.048” shim under each stand. This gave me a 0.023” pre load when torqued down to 22 foot lbs. About ½ a turn, the instructions call for ½ to ¾ turn past zero pre load. I didn’t follow the shop manual procedure for installing each rocker because with the Yella Terra common shaft for both intake and exhaust rockers you will put the shaft in a bind and could maybe bend a bolt. Just turn both bolts down evenly so as to not bind the bolts in the shaft bolthole. The rockers didn’t hit the valve covers and they had good clearance on my double springs.
The motor is as quiet as before and I had a stock rocker puke it’s needle bearings on one side. The bad stock rocker didn’t make any valve train noise that I could hear. The bad rocker had a noticeable valve stem off center wear pattern. I did a DE at VIR and from the wear mark, it might have happened just before or at the beginning of the DE, I had trailered the car and hadn’t driven it since. I found two needles in two cylinder stud holes and a bearing cage with one of them. I’ll look for the rest when I change the oil.
I went into detail on this to help those who have never had to deal with a system that has to seat on the head and also have the correct lifter preload set. Not like adjusting the hydraulic lifters on an old small block, with a friction lock nut. I read all the threads and David Vizard’s valve train book (doesn’t cover the LSx) and I can see why there is so much confusion. Anyone who can add to this or catches a mistake, please jump in.
Cheers, Curt
Purchased from New Era, $415. There are several grades of rockers from Yella Terra, the “Easy fit” direct replacement for original rockers and the Platinum/Platinum Plus. Their web site give some details. www.yellaterra.com.au
I had to chuck all the rocker bolts into my lath to remove a few thousands from the bolt shank to make the bolts fit into the rocker shaft holes. I tried taping a few in, some bolt shanks were so tight that I couldn’t tap them in with a machinist brass hammer. The few that would tap in were so tight that I couldn’t feel the threads engage in the AFR heads and they started to cross thread. If you don’t have a lath, chuck the bolts heads in an electric drill and run a file over the shank while they’re spinning. The rocker shafts are hardened, I couldn’t de-burr the holes with a scraper or a rat-tail file. The holes could have been finished with a smoother surface. The rest of the rockers are beautifully machined and all the tolerances that I could check with a dial caliper were spot on from set to set.
I had to use the supplied 0.048” shims to get a ½ turn pre load. My 1999 rocker bolts are 20 tpi or 125m thread. 20 tpi equals 0.050” travel for one turn of the bolt. They must be an oddball metric size, they were larger than 8m125 and smaller than 9m125.
I couldn’t find a midget to hold the push rods to tell me when they stopped spinning. I could only get one index finger on one hand and maybe the little finger on the other hand on a push rod. The push rods lie to you, they feel like they’re turning and they aren’t as I marked them with a drop of white paint, I could not get an accurate zero setting using this procedure. Maybe this is why some have a problem with their installation.
What I did and I thought it worked great was put a cylinder at TDC and tight down on the rocker bolt with a 0.013” feeler gage until you couldn’t move the feeler gage and back off the rocker bolt until the feeler gage just moved. I used a 0.013” feeler gage because this is ¼ turn with the 20 tpi rocker bolt. (Well, close enough!) I removed the feeler gage and went ¼ turn in for zero preload on the lifter. If you can push down on the push rod with your thumb, the lifter has collapsed, in this case just watch the rocker when you pull the feeler gage out, if the push rod end of the rocker moved up, you were compressing the lifter internal spring so do it over again until it doesn’t move. I did this on both banks incase there was a tolerance stack, both banks came out the same. I got an acceptable wipe pattern on the valve stem. Yella Terra instructions call for ½ to ¾ turn past zero preload.
With my head, gasket, cam and push rod length, I had to use one 0.048” shim under each stand. This gave me a 0.023” pre load when torqued down to 22 foot lbs. About ½ a turn, the instructions call for ½ to ¾ turn past zero pre load. I didn’t follow the shop manual procedure for installing each rocker because with the Yella Terra common shaft for both intake and exhaust rockers you will put the shaft in a bind and could maybe bend a bolt. Just turn both bolts down evenly so as to not bind the bolts in the shaft bolthole. The rockers didn’t hit the valve covers and they had good clearance on my double springs.
The motor is as quiet as before and I had a stock rocker puke it’s needle bearings on one side. The bad stock rocker didn’t make any valve train noise that I could hear. The bad rocker had a noticeable valve stem off center wear pattern. I did a DE at VIR and from the wear mark, it might have happened just before or at the beginning of the DE, I had trailered the car and hadn’t driven it since. I found two needles in two cylinder stud holes and a bearing cage with one of them. I’ll look for the rest when I change the oil.
I went into detail on this to help those who have never had to deal with a system that has to seat on the head and also have the correct lifter preload set. Not like adjusting the hydraulic lifters on an old small block, with a friction lock nut. I read all the threads and David Vizard’s valve train book (doesn’t cover the LSx) and I can see why there is so much confusion. Anyone who can add to this or catches a mistake, please jump in.
Cheers, Curt
