Thread: Chevy 350, zero compression. engine not starting

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Originally Posted by JbRat

Mechanic says they will self straighten... this is after about 2 mins of running at 2000rpm

This "mechanic" should have had his head pinched off at birth. You are headed for expensive trouble with those fosdick rockers. Do not run the motor with them, not even for a second. Jerry gave you the link to Jegs, for the proper rockers to use with L31 heads (self-aligning rockers).

If you feel the need to use roller rockers, here are the ones to use, narrow body to fit under your center-bolt valve covers and self-aligning roller tips......
http://www.jegs.com/i/Scorpion+Racin...P1035/10002/-1

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Thanks for confirming my suspicions... I'm ordering as we speak..

I think you said he installed bigger springs-----------well as other things have showed up, I'm wandering if the rockers will even clear those retainers underneath side-- I would suggest that yu get a vortec vavle and compare the tip length to the ones in your heads. vortec valve tips were longer for the alignment dealie with the rockers------


GM made a very good flowing head but sure intercourse themselves(and the rodding world) with a bottom line $$$$$ that throw away the years long development of the screw in stud/guide plate just to save GM a few bucks-----


I have done several sets of these with mods for the screw in studs, larger springs, and don't remember just where we ended up on push rod length( every thing done here is custom so no off the shelf numbers)

Not sure if he installed bigger springs... he said he installed a stage 2 cam... with no specifics. He did use screw in studs and trying to verify the size before I order anything.

what about these? I can get them today, instock, locally...

http://www.summitracing.com/parts/slp-r-973/overview/

sealed power

Originally Posted by JbRat

what about these? I can get them today, instock, locally...

http://www.summitracing.com/parts/slp-r-973/overview/

sealed power

These are not self-aligning. You'll have the same problem.

Says they are self aligning and looks like it to me

Yeah, Jerry, I guess you're right. I didn't look at the alternate photos. My bad.

Happens to all of us old timers --------

Originally Posted by jerry clayton

I think you said he installed bigger springs-----------well as other things have showed up, I'm wandering if the rockers will even clear those retainers underneath side-- I would suggest that yu get a vortec vavle and compare the tip length to the ones in your heads. vortec valve tips were longer for the alignment dealie with the rockers------

JbRat, Jerry makes a valid point here. When you get the proper rockers installed, roll the motor over with a breaker bar/socket and inspect each and every rocker tip for missing the top of the retainer. If the side of the rocker that hangs down over the valve tip contacts the surface of the retainer, the ball game is over because the locks will be loaded/unloaded, loaded/unloaded, loaded/unloaded until they fail and you drop a valve or 3, resulting in destroyed pistons and cylinder walls and probably the heads as well. Have a buddy do the turning while you slide a small piece of plastic between the rocker rail and the retainer. I have measured the thickness of a plastic coffee can lid at 0.023" (twenty three thousandths of an inch), so cutting two of these pieces from a lid to slide between each rocker and retainer (one on each side of the rocker) will prove at least 0.023" clearance and that should be plenty. I'm visualizing the strips at maybe 1/2" wide, by 4" long. This will take some patience, so don't get in a hurry. There is a word that describes this checking and re-checking of parts for a specified clearance, it's called blueprinting. I'll bet that somewhere in the blueprints of the L31 heads, you could find the exact figure that the Chevrolet engineers specified for rocker to retainer clearance, but lacking that information, I'm of the opinion that ~0.020"/0.025" would be sufficient. The old saying is that a miss is as good as a mile, but taking clearance measurements with the motor sitting static is a whole lot different than taking clearance measurements with the crank twisting 5 grand or better.

If there is insufficient clearance, then you will need to change to longer valves made specifically for L31 heads or use locks that have the internal lip moved up in the lock to move the retainer down in relation to the tip of the valve. These are called plus 0.050" or minus 0.050" locks. Caution though, while using a minus lock gives more valve stem sticking up beyond the retainer, it also reduces the valve spring installed height and could contribute to valve spring coil bind, which usually results in bent or broken pushrods, but in extreme cases, could do mechanical damage to the lifters/camshaft if stout pushrods were used or if your personal kharma is S.O.L., or the increased valve spring pressure could take a toll on the lifter/lobe interface and roach the cam (actually the lifter goes away first, then takes out the lobe).

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Here's a set of stock stamped steel, 1.5:1, self-aligning from JEGS for $61 with free shipping.

http://www.jegs.com/i/GM+Performance...FVFsfgod6vgBmg

Roller tips are tricky and if not installed correctly, all of what Tech says can come true! This is also a real danger if the roller walks across the tip of the valve stem. This is not one of my engines, but I'm pretty sure that this did not end well!

Glenn

Pinched his head off at birth. Heh heh, that's harsh.

Originally Posted by firebird77clone

Pinched his head off at birth. Heh heh, that's harsh.

That's why I have very few friends. I tell 'em like it is and if they don't like it, they can just keep movin'. I will not suffer fools.

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Originally Posted by techinspector1

That's why I have very few friends. I tell 'em like it is and if they don't like it, they can just keep movin'. I will not suffer fools.

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And hotrodders is full of them.

Not everyone is who they say they are, and not all conversations need commentary. Everyone I meet is a friend, not all are good at it (including myself).