How much clearance should i have between the rocker arm and the valve spring retainer? the rocker is comp 1318 and the springs are 1.5 dia. lunati set at 1.85 installed height.

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ICON Motorsports
1st & 3rd

 

The Comp Cams Catalog might have the correct installed height information. It's very informative. You just replied to my Poly Lock question, thanks. Where can I get them and how much do they usually go for?

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i buy most of my stuff from jegs. i usually buy lunati cam stuff. most poly locks will run around 25 to 40 dollars, just guessing.

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ICON Motorsports
1st & 3rd

 

Ed,

I wish I had an absolute, measurable number, but I don't. I try to follow the rule that the clearance shouldn't be less than would be required if the roller was out of the rocker, but since I haven't had my fingers on the new design rocker, I'm not sure that would apply.

The rocker fulcrum should be perpendicular to the valve stem at 1/3rd of the gross valve lift. Any clearance should be adequate to allow that. If not, the push rods might be a little off optimal size (generally too short). If the retainers are getting uncomfortably close to the undersides of the rockers in the valve closed position, this might be another indication of short push rods.

I went through this with my last cam/valve/head project on the old LT1. Milling the stud bosses twice was not my idea of fun, and searching for the correct push rods was another minor frustration. I ended up with Mopar push rods for a 318 truck engine. They were about 0.020" from optimum length.

Fun, ain't it?

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Later,
Vader
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"No matter how hard you try you can't stop us now"
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well vader i guess i was asking this question knowing the answer. i tried to slide a .005 feller gauge blade under the rocker and the retainer and it was no go. the little engine is just dummied up (one head to degree cam) with out a head gasket so i'll pick up .04 in height (i like to check piston to valve clearance with out head gasket, extra insurance). i was thinking my push rods are too short, i was also wondering about running lash caps on the valves to increase the height between the retainer and rocker.

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ICON Motorsports
1st & 3rd

 

Ed,

Lash caps would probably raise the rocker, but might only serve to change the angle of the rocker further in the wrong direction. They work, but add mass to the valve train and scare me a little. The thought of extra parts floating in there is a little unsettling.

Do you know how much base circle you lost with the new cam? If you have a length checking push rod, you should be able to determine a push rod length that would be appropriate. I made a couple of old stock pushrods into adjustables. I think I've lost one, but one is enough. It's not as nice as the purchased ones, but it works.

I usually try to get stock pushrods from something that are within 0.050-0.080" of ideal. Finding "plus" lengths for factory rollers is not as easy as the old flat tappets, which is why I ended up with Mopar rods at 7.350 or so. They're close enough to get the rocker angles right, and are a lot cheaper than custom push rods. If I screw one up, replacements are available everywhere instead of special order items. And if the valves/seats ever get ground deeper in the heads, I've got a couple extra thousandths adjustment in the right direction. The 4130 tubing set was about $60.00 instead of $200.00 for customs.

Without the right rods, the rockers tend to be a little too deep on the studs (which is why mine were milled twice - no fun). After a second milling and more playing, I changed to the right rods and geometry was restored. Your new rockers might have a different geometry, so you have a better view than I do.

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Later,
Vader
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"No matter how hard you try you can't stop us now"
Adobe Acrobat Reader 4.0

 

Ed,

Sorry it took so long, but I am not that fast with the "home Cad system". This is what I try to use as a starting point, then adjust lengths from there:



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Later,
Vader
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"No matter how hard you try you can't stop us now"
Adobe Acrobat Reader 4.0

 

man you're good vader. i've gave up on the lash caps. actually i knew it wasn't for me when i said it, but was grasping at straws. i have to make a trip to jegs next weekend for parts for my sons car so i'll get a set of push rods to check length with then, if i don't try to make a set. how'd you do it since it looks like i have 12 that won't work for me?

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ICON Motorsports
1st & 3rd

 

Ed,

If your factory pushrods aren't hardened (probably not) you can cut a tube about an inch from the end, braze or sivler solder nuts on the cut ends, and use a 10-32 headless screw and jam nuts to lock the rod in place. If they are hard, it's just a little more difficult to cut them, but I think you have the means to get it done. A TIG welded nut would be even better.

Since you have several "donor" rods, you can make them in steps of about one-half inch in ranges from 7.00" to 8.50". That should cover most of you SBC and BBC needs, regarless of cam and lifter design.

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Later,
Vader
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"No matter how hard you try you can't stop us now"
Adobe Acrobat Reader 4.0

 

Here's a dumb question for someone. Which way do the retainers go? In my rebuild books I never saw which way they go. Grooves up or down? I put mine down, but I was having trouble with setting the lash, and just wondered if I was wrong.

Thanks,

Scott M.

 

only one way a retainer will fit the spring. one way it fits other way it falls off.
vader:
i was looking at it today. stock push rods are 7.165 or so. i figured i could cut a push rod and silver braze a machine screw in one end and tap the other and use a jam nut to lock the length after i get it figured out. another chance to play with my lathe i asked how to make them before i looked or thought about it.

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ICON Motorsports
1st & 3rd

[This message has been edited by ede (edited December 17, 2000).]

 

hmm. guess that's not the name. I meant the peice that drops in between the lock nut and the rocker. which way does that go? Grooves up or down?

Thanks,

Scott M.

 

the rocker ball?
the groves would go down, the round part goes down the nut sits on the flat part.

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ICON Motorsports
1st & 3rd

 

Guess I should have drawn that in, too.

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Later,
Vader
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"No matter how hard you try you can't stop us now"
Adobe Acrobat Reader 4.0

 

Vader, i think you need to pull out the die grinder mouse and pocket port that head...careful of the water jacket though

 

merf:
i liked the die grinder mouse. this was a good thread, just sorry it involves me, my parts, and my cash.

vader:
as always thanks for all the help.

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ICON Motorsports
1st & 3rd

 

I don't know of a minimum clearance there; but I'd like to see at least .050".

If the rocker is rocked so far back that it is in danger of hitting there, then the pushrods are almost certainly too short. You might want to get one of those pshrod length checking tools, or just buy .100" long pushrods. They aren't alot of money.

Generally, the rule of thumb is that the pushrods should be .050" longer than stock for every .075" of valve lift over about .400". That should keep the geometry close to the factory's. However the farther from box stock the whole system is, the more you need to check to b sure. Comp sells pushrods in .050" increments over a huge range of lengths, unfortunately they're the good ones so they aren't as cheap as the others; but they stilll aren't going to break the bank.

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