Thread: 72elk

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You'll need to post everything you know or can find out about the heads you bought. Have they been fitted with different springs and retainers to allow more valve lift over stock? Stock L31 heads were designed for a valve lift of no more than about 0.430". Every yahoo and cowboy will tell you that they will take a 0.480" valve lift....and they will, IF YOU USE UP THE 0.050" SAFETY MARGIN THAT CHEVROLET ENGINEERED INTO THE PRODUCT. The correct way to get more lift out of the L31 heads is with a different spring and a different retainer......or you can conduct the ghetto grind on the stock L31 retainers, where you turn them upside down on a surface grinder table or Blanchard grinder table and grind 0.080" off the bottoms of them. That will allow a valve lift of 0.500" and still keep a safety margin. Use a socket (I think 1/2") to gently tap the valve guide seals down onto the valve guides solidly before assembly.

You can use cast iron rail rockers like the original L31's used, or you can opt for aftermarket full roller rockers such as these offered toward the bottom of this post, by Pace Performance. Here is the stamped steel rocker arm like Chevrolet used on the L31 motor.......
Chevrolet Performance stamped steel 1.5:1 ratio, narrow body rocker arms with balls and nuts....
https://www.summitracing.com/parts/nal-12495490

Chevrolet Performance does not manufacture a 1.6:1 stamped steel rocker. You will have to go to an aftermarket manufacturer if that is what you want, and they won't be stamped, they'll be aluminum full rollers. Please stay away from the Comp Magnum rollers, they are a joke, having a roller tip and a conventional fulcrum. That's exactly backward from the way they should have been designed. They should have had a conventional tip and a roller fulcrum. The roller tip is useless. Their only saving grace, in my opinion, is the fact that they are a true 1.52:1 ratio rather than a hit or miss stock Chevy 1.5:1 (or more, or less) due to manufacturing tolerances.

https://paceperformance.com/i-895190...-aligning.html
I know nothing about these particular rockers and will not recommend them nor say anything negative about them. I am offering them up just so you can see that they are available in an affordable product. You should expect to pay close to $300 for a quality, known brand of rocker or you can take a chance on these.

If you use any 1.6:1 rockers, I would recommend that you use a Louis Tool to correct the holes in the heads where the pushrods come up through from the lifter cups. Actually, I would do this operation to ALL L31 heads, regardless of rocker ratio.
https://www.summitracing.com/parts/pow-pow351305
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To bring you up to date, I may be going over board with the heads but more is good right? I picked up a set of vortec heads on eBay from a head shop, they are the 906 castings. Took them to a local head shop and they checked out good and are in prime original shape. I ran accros a guy on a local web site that had recently bought a house with a lot of stuff left in the garage. He advertised comp Cam b hive springs no 26915-16, retainers no 795-16 and seats no 705-16 all for $50 so of course I picked them up. I still need to get locks but don't know what I need. I've also got the Mr Gasket pin kit. I have the Eldebrock AVS thumper 650 carb and the eldebrok RPM manifold is on order. Not sure what push rods I need and with the new springs what Cam specs I should be looking at. I think I'm going to be WAY over 300 hp, but that's ok. Might as well go for 400. Any help you can give would be appreciated.