SBC Solid Cam, Rockers Hitting Valve Covers?! - Hot Rod Forum : Hotrodders Bulletin Board
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Old 04-30-2007, 11:51 AM
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SBC Solid Cam, Rockers Hitting Valve Covers?!

OK-
I finally started this thing up over the weekend and did the recommended 2500RPM cam 'break-in' for 20 minutes.

The weird thing is that the rocker arms were hitting the inside of the valve covers (on the pushrod side)-
When I removed the valve covers, I noticed that the rockers were looser than the specified .026/.028 lash and snugged up the nuts. Even with the .026/.028 lash, I still had the rockers hitting the inside of the covers!
The exhaust side seemed to be the ones rubbing the most, so I systematically started tightening the nuts until the rockers no longer hit the valve covers (about a 1/4 turn!).

Since this is the first time I've ever tried a solid lifter cam, I have no idea if this is 'normal' or if I'm just an idiot when trying to adjust these lifters initially?

Based on my measurements now, it appears that I'm down to about .022 lash to prevent any hitting of the rockers to valve cover.

Has anyone had this happen before? Is something wrong or am I just really off the mark on this lash adjustment process?

The engine appears to run OK otherwise- I have decent vacuum for a performance cam and I have marked the studs/rocker nuts to confirm nothing is backing off while running.

I have about 40 minutes on the engine total and don't want to run it any longer than I have to until I have this resolved.

I am running the cast iron, large port Vortec 'Bow-Tie' heads with stamped steel 1.5 rockers (Elgin 'long slot'), stock length pushrods and guide plates (NOT using self-aligning rockers). 400 +.040 SBC, 10:1 CR, Lazer Cam 243/248 @ .050 and .511/.480 lift, .026/.028 recommended lash.

Any advice or direction would be greatly appreciated.
Thanks!
Elm

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Old 04-30-2007, 12:13 PM
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This is not to uncommon an event with a high lift cam. You'll most likely need to lay your hands on a set of tall covers.

I think your lift is a bit tall for a ball fulcrum rocker, you should seriously consider something with a roller fulcrum. It won't take long before the ball will fry with this much lift while working against the spring pressure to close these valves. You're not in super serious territory but a half inch lift is about the reliability limit for those things.

Bogie
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Old 04-30-2007, 12:41 PM
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Tall Valve Covers?

Thank you for the response- But I'm confused regarding your 'tall valve cover' comment?
The rockers are hitting the side of the covers (closest to the pushrods), not the the top.
Unless taller valve covers are also wider somehow, I don't see how it will help.
It's almost like if I could grind off a few 32nds off the back of the rockers, my problem would go away..
Elm
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Old 04-30-2007, 12:45 PM
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I assume you are using stock covers? If so, make sure you have them on correctly. They do have a very slight angle to them and if you have them backwards, the pushrod end of the rocker will rub the cover.

Mark
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Old 04-30-2007, 12:59 PM
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Interesting.. I'll need to look more closely-
One side of the cover has a continuous lip and the other side only has a lip for a portion of the length.
Both the stock aluminum L-46 covers and the chrome aftermarket cover that I'm using have the same configuration.

I put them on with the full lip towards the exhaust side the the partial lip towards the intake side.
Please let me know if this is incorrect?

Thanks!
Elm
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Old 04-30-2007, 01:58 PM
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If snugging up on the nuts seems to have solved the problem, it sounds like a vertical clearance issue. But however it is hitting, it might work as well to get the newer silicon gaskets to add height, rather than using tall covers.

Pat
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Old 04-30-2007, 04:57 PM
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Quote:
Originally Posted by ezobens
Thank you for the response- But I'm confused regarding your 'tall valve cover' comment?
The rockers are hitting the side of the covers (closest to the pushrods), not the the top.
Unless taller valve covers are also wider somehow, I don't see how it will help.
It's almost like if I could grind off a few 32nds off the back of the rockers, my problem would go away..
Elm
Hitting where on the side, high up where the cover begins to radius into the top? If this (I ask the question because from here I can't see your original thread) is a roller cam, you may find you need shorter push rods. Most roller followers are taller than the flat tappets they replace, this requires a custom length push rod. This problem is exacerbated by milled heads and or block deck which makes the distance between the rocker and the lifter shorter still. If you haven't I highly recommend getting in there with a pushrod length checking tool and finding out what the exact required push rod length is.

Bogie
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Old 04-30-2007, 07:35 PM
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Bogie,
The rocker arms are hitting low on the intake side of the valve cover- About 1" up from the gasket surface.
It's the rear 'tip' of the rocker arm that is making contact with the cover- Back by where the pushrod sits. This has nothing to do with height or lift of the cam, it actually appears to be hitting more at the bottom of the cam travel when the rocker tends to 'wobble' due to the solid cam lash.
I am running a solid flat lifter cam- No roller cam.
The heads are brand new out of the box and the block was only mildly decked (.005) to clean it up when I had it bored. I used one of those Manley rocker geometry checkers and the pushrod length appears to be dead-on to the valve tip.
Thoughts?
Thanks!
Elm
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Old 04-30-2007, 09:48 PM
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Maybe it's the redneck in me, or the fact that I've spent two days making large by huge rotors and calipers fit on my GTA but either way it sounds to me like you need to introduce your valve covers to Mr. ball-peen hammer

If you want it to look pretty you could use a lead bag and a wooden dowel and get those few 32nd's ...Assuming they're steel.

If they're cast aluminum a die grinder could convince them to play nice..

Seriously, there are ways to add that little clearance without it looking bad, if it's noticeable at all..I've had issues with the small, center bolt type, valve covers and if after checking to make sure all is well engine wise (like it sounds like you have) I just "help" them along.
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Old 05-01-2007, 06:25 AM
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Tall valve covers

I have had this problem before, and seen it many times at the track. 26/28 sounds sort of like a Speedway cam. If everything is set right, and the engine runs great, and you set the lash hot, not cold, try the rubber valve cover gaskets and a set of steel, thin-wall valve covers from PAW, tall stlye. These you can actually manipulate by hand. Let them sit in the sum or boil them, and sort of form them by hand. If you are not into looks, Mr. Ball-peen does the job perfectly. Don't use the pretty aftermarket thick covers. Don't adjust the valves with a deep socket--it pushes down on the balls and gives a false reading.
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Old 05-01-2007, 09:16 AM
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you know I haven't seen this problem in a number of years and rereading your original thread I saw these are Elgin rockers. Thinking back to when Elgins were popular, this was a fairly common occurance. It seems the Elgin has a little more meat, as did Isky and Howard versions, than the GM rocker and certainly more modern designs by Crane, Comp, etc.

As has been suggested you can dimple the covers with a ball peen, and sometimes doubling the gasket helps. Another trick is to use a raised guide plate (<<<http://www.competitionproducts.com/prodinfo.asp?number=8032>>> for a picture). This takes some of the side to side rotational movement out of the rocker by supporting the push rod at a higher location. Check the inside of the guide for clearance to the push rod, this should not touch at any lift point. If it does the pushrod will bind and a few things can happen, the obvious is the push rod bends but the other is that the push rod tries to pull the rocker back toward the rocker cover, it's not much but might be just enough.

Finally you can kiss a little metal off the back side of the rocker, while shape and thickness provide strength, the load on the rocker behind the pushrod pivot point isn't nearly so high as loads between that point and the valve tip so it can sacrifice some metal on that back side.

Bogie
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Old 05-01-2007, 01:24 PM
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beat it it with a hammer, I did it, and it worked just fine, can't even really tell unless I point it out to people.
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