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Old 04-19-2010, 02:55 AM
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1.6:1 Roller Rocker arm troubles...

I have some Summit Racing aluminum roller rocker arms 1.6:1 that I am installing on mid 80's GM crate motor heads. They have hardened exhaust seats and I have reground the valves. I was test fitting with the stock length pushrods 7.781" give or take a couple thousandths... and I have an adjustable pushrod ordered so i can check my geometry and get it right but my biggest concern was that the trunnion bearing portion of the roller rocker was sitting on the casting around the 3/8"s mounting stud. Is this something that when I change my pushrod length will be corrected or is something way off? I have looked through dozens of forums and have not seen anything like this? That is just where the rocker happens to be sitting as all of the lash is taken out of the lifter. So I'm assuming that when I measure for the correct pushrod length, it will perch the rocker up higher and will not touch the casting around the mounting stud? Any help with this will be greatly appreciated. Thanks!

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Old 04-19-2010, 03:24 AM
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Also I forgot to add... I've been wondering about the rocker arms because they are NOT self-aligning and I am not running guide plates for the pushrods. Since the rocker arms are NOT self-aligning, what do I need to do to make sure that they are going to work correctly?... These are the first roller rocker arms I have played with. The stock 1.5:1 stamped steel rocker arm fit just fine on the heads without rubbing like I stated above about the roller rockers hitting... Anyways, sorry to confuse. I have two issues troubling me about these roller rocker arms.
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Old 04-19-2010, 04:07 AM
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Were the stock rocker arms self-aligning?? There has to be some means of guiding the rocker, either the rocker is of the self-aligning type or the head has slotted pushrod holes. If the stock rocker arms were non-self aligning then that means the rockers were pushrod guided, which means there is a guide slot in the head for the pushrod and not just a clearance hole. If there is not a guide slot for the pushrod and just a clearance hole the head will have to be machined for screw-in studs and pushrod guideplates or you will need to get a different set of rocker arms that are self-aligning

When you add 1.6 rockers you will need to check to see if this slot is long enough as making the 1.6 ratio moves the pushrod end of the rocker closer to the stud. You may have to grind the slot longer toward the stud to get clearance, and this is a common modification if the cam is bigger than stock, you don't want the bottom of the slot to interfere with the pushrod as that will bend the pushrod or pop it out of the pushrod cup in the rocker arm.

You may have to go to a +.050" pushrod to get the rocker off the cast boss for the stud, as long as this doesn't screw up the geometry. Other solutions would be to grind or file the bottom of the rocker for clearance or machine the head for screw-in studs. There is no gaurantee that the correct pushrod for getting the geometry right will get the rocker up off the stud boss. You may have to cheat on the pushrod length a little to get it all to fit or else you are back to grinding the rockers or machining the head.

The stock rockers fit just fine because they are physically smaller around the pivot area. The interference you have is common, especially if you have a larger than stock cam where the base circle has been made smaller, which sets the lifter in the hole farther. Add rockers with a big body and wham, you have an intererence problem.
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Old 04-19-2010, 04:43 AM
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Sorry, I forgot to mention that... I already have had the heads machined and have screw in studs installed otherwise the spring pressure I'm running would pull the studs out of the heads.

I just had a hole in the heads for the pushrods and I opened those up quite a bit to add clearance for the pushrods and I already ran into that problem of the pushrods rubbing or close to rubbing.

I'm just thinking that the longer pushrod will hopefully be enough to get the rocker off the head and let it pivot freely.

I just don't completely understand the self-aligning rocker arms, I don't think I've ever seen anything like that. I don't really know what to look for to know if what I have is one way or another. Plus the screw in studs I have do NOT have a wrench head at the base of them. My machinist installed them and I do not know if he used some type of thread lock or sealant when he installed them. The difficult thing is, he has since retired... I just do not know if it would be worth running guide plates even if the rockers ARE self-aligning. I'm not completely stupid about this, it's just the first problem I have run into that I have never heard of anyone else having this problem before... The rocker arms sitting on the heads...
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Old 04-19-2010, 04:59 AM
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If you have opened the pushrod guide holes with a hand grinder. You will need guide plates or guided rockers. To use non guided rockersyou will need to have the stud bosses shortened approv 3/8" and guide plates with hex based studs installed.
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Old 04-19-2010, 05:44 AM
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On my mid eighties heads the slots were the guides, I swapped to World Products heads and the slots on those were also the guides, hardened pushrods were the only requirement.
I also have 1.6:1 roller rockers , used them on both types of head.

"I just had a hole in the heads for the pushrods and I opened those up quite a bit...."

Not a good idea.

The guiding slots.

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Old 04-19-2010, 05:56 AM
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The pushrod holes were just that... holes. They did not look slotted as your picture shows. I had to open them up or they were going to rub on the top side of the opening due to the 1.6:1 rockers. These are SBC heads if I didn't mention that earlier. I figured out the SA/non-SA rockers and I have Summit exchanging the rockers I have for the SA rockers. I still need to figure out the right pushrod length and hopefully the new rockers won't sit on the heads like the old ones. These will be the narrow arms instead of the wide arms I am sending back. Malc, the picture really did help clarify that for me. Thanks!
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Old 04-19-2010, 06:21 AM
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How to check pushrod length and how to measure for correct length.
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Old 04-19-2010, 06:33 AM
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Quote:
Originally Posted by Caballerokid
I was test fitting with the stock length pushrods 7.781" give or take a couple thousandths
Standard length is 7.8" just for reference.

Push rods generally come in 0.050" length changes, but you can order any length.

Last edited by cobalt327; 04-19-2010 at 06:39 AM.
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Old 04-19-2010, 09:04 AM
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Quote:
Originally Posted by Caballerokid
That is just where the rocker happens to be sitting as all of the lash is taken out of the lifter.
What procedure did you use to remove all the lash. Twisting the pushrods or jiggling them up and down or what?
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Old 04-19-2010, 09:09 AM
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Quote:
Originally Posted by techinspector1
What procedure did you use to remove all the lash. Twisting the pushrods or jiggling them up and down or what?

I agree, when it comes to hydraulic lash, just jiggle it until it tightens up then tighten it down an 1/8 turn. IMO jigglin' beats spinnin' any day of the week.
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Old 04-19-2010, 11:52 PM
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Quote:
Originally Posted by techinspector1
What procedure did you use to remove all the lash. Twisting the pushrods or jiggling them up and down or what?
I was twisting them until I felt resistance and an additional 1/2 turn.

I sent the summit roller rockers SUM-G6906 back to summit and they are sending me the Proform Parts 66915 rockers that should do the trick for the SA rockers. I just hope that when I get the pushrod length checkers I can figure out why the rockers where sitting on the heads. So far things are working out, hopefully the trend will continue...
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Old 04-21-2010, 03:41 AM
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Quote:
Originally Posted by Caballerokid
I was twisting them until I felt resistance and an additional 1/2 turn.
Unless you are a professional engine builder and do this every day, all day long, you probably got the valves too tight. That's why the rocker trunnion was down against the base of the stud in my opinion.
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Old 04-21-2010, 04:08 AM
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I don't do this all the time but I am a technician... I was finger tightening them down until I felt resistance and they were sitting on the heads. Just the rocker arm set in place was enough that is was maybe at most an 1/8" from the head. That was with 7.8" pushrods... I think the roller rockers are just that much bigger where the trunnion bearing was because I set the original 1.5:1 stamped steel rocker on and it had plenty of clearance.
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Old 04-21-2010, 06:41 AM
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Quote:
Originally Posted by Caballerokid
I don't do this all the time but I am a technician... I was finger tightening them down until I felt resistance and they were sitting on the heads. Just the rocker arm set in place was enough that is was maybe at most an 1/8" from the head. That was with 7.8" pushrods... I think the roller rockers are just that much bigger where the trunnion bearing was because I set the original 1.5:1 stamped steel rocker on and it had plenty of clearance.
your lifters have too much preload, meaning you overtightened the rocker arm adjusting nuts.

You also need to either take a picture of your rocker arm setup OR take your heads to a machinist to see if you need to run guide plates, from the way it sounds you do but can't tell for sure without seeing it.
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