SBC Gurus HELP!!!!!!!

OK guys, I humbly bow before you and seek guidance. I purchased a fresh 350 rebuild a while back and have yet to take it down the road. The guy I bought it from had mentioned that the rockers might need adjusting. Well, here I am without the guys number or any idea how to get a hold of him! The engine is definatly built and I have reason to trust the guy. But, my question is what do I have to worry about? I mean, the rockers don't have very much wiggle room if any. So, is there a specific amount they are supposed to be tightened?? Please help, fellas. If anyone knows, y'all will!


Brian

 

Need more information such as whether its hydraulic or solid cam/lifters. Did you receive a cam spec card with it?

It would be a good idea for you to buy "How to Rebuild a Small Block Chevy" Motorbook and start educating yourself how everything works.

 

Once you get it running you will know if they need adjusting. ***uming that it has hydraulic lifters the way we used to do them was to tighten the rocker nut just enough so you could still twist the push rod with your fingers. Pick up a service manual or small block chev book and you should be able to figure it out, unfortunatly I don't think there is any real torque spec for sbc rocker arm nuts.

 

They are hydraulic lifters and all he told me was it has a 510 lift cam. I have the "how to rebuild SBC" and the "how to hot rod SBC" from the 70s and neither have any info on it and i've read them cover to cover. Maybe I'm overlooking something.

 

With hydraulic lifters and stock steel rocker arm...the way I always did it was:

Run the engine to operating temp. Then shut it down.

Take off one valve cover. Use aluminum foil to cover the end of the rocker where the oil from the push rod squirts out. You can also use those store bought rocker arm plugs...little plastic plugs with the wire clips on them.

Fire the engine back up...it'll probably smoke a little from some oil dripping on the exhaust manifold...but you should be able to minimize this with the aluminum foil covering the oil hole.

Back the nut off slowly until it starts to tick or clack...then tighten it a quarter turn back in. Just do each rocker arm nut like that and you should be good to go. Sounds messy, but it's really not.

But like I said that's only for hydraulic lifters and stock stamped steel rocker arms.


Also...if the engine is out of the car...Bryan6902 is right about tightening the rocker arm just enough so the push rod is snug but you can still twist it...this'll get you in the ballpark. Then you do your final adjusting with the engine running. Once they're adjusted...you shouldn't have to adjust them for a long while...unless you got a bad or loose rocker arm nut.

 

the first book should have the info on adjusting the valves

has the motor ever been run? i ask because you say it's a fresh rebuild....when i rebuild a motor and don't plan on using it right away i leave the rockers loose and don't adjust them until i'm ready to fire it

 

It's fresh in the sense it doesn't have any "miles driven" after the build. I've cranked it and it "sounds" fine, but when he said that the rockers may need adjusting, it scared me to put any imediate miles on it! Am I being over cautious? There isn't any ticking to be heard, and the rockers feel normal as is. I just don't want to mess up the engine if something is overlooked.

 

When I adjust valves I do each valve separately.

Beginning with the first cylinder, crank the engine slowly until the exhaust valve just starts to open...then set the lash (or preload for hydraulic) on the INTAKE valve for the same cylinder. Then rotate the engine until the intake valve has opened and is almost closed again...then set the lash on the EXHAUST valve. Repeat for each cylinder and you should be good to go.

Set lash according to cam specs. For hydraulics, tighten the adjusting nut until the pushrod can just be spun by hand...then put 1/2 to 1 full turn on it to set preload.

 

They really like to see .010 preload on a stock lifter. I have seen aftermarket (crane) cams that couldn't go tighter than 0 lash.
I always set them cold. Use the dist and whatever cyl it is pointing at, adjust that one. As mentioned, spin the pushrod between your thumb and forefinger. tichten untill you feel a slight drag. then a bit (1/4-1/2 turn) more. This will get you real close.

 

sounds like he may have adjusted the rockers while engine on the stand. I have a Haynes manual on a 70 to 81 camaro that goes into depth about adjusting the rockers while engine is not in the car. This method works fine and I like the fact that I don't have oil clean up and the foil trick works great if you rather adjust while running. Usually if the valves were tight it would backfire or pop in the exhaust or carb, loose is the obvious tick. If you don't have either you should be fine. They guy who sold you the engine may just be cautious. Hope this helps

 

Thanks guys, I'll take all this and give it a go in the coming weeks. I didn't have any back-firing when I started it up but I also haven't let it run longer than 5 minutes at a time. Y'all have been tremendous with the advice. Maybe I can get it running like a "****d-ape" and put up some video for y'all. Thanks again.




Brian

 

Here's an easy way to adjust them running.


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Where in IN are you.

 

I don't tighten them down "until you can twist it by hand" or "until you feel drag" or "until you can't spin it by hand"... I know this was outlined in the "How to Rebuild an SBC" book years ago... and the method was also shown in several magazines of the time... but you can get "off" settings if you have lube on your fingers, or parts... too many variables IMHO. Some guys may do it with success... but they have probably done it on a daily basis, or quite frequently.

The way I was shown 20 years ago was to tighten the nut to zero lash You can find this by moving the push rod up and down while you tighten the nut. You can "Feel" when it is at zero lash because it doesn't move up and down any more.

After you get it there, tighten the nut 1/4 turn to 1/2 a turn and you're good.

The studs on a stock/ mild SBC are 3/8" 24... so one revolution of the nut makes the nut go down .0416... so, 1/4 turn s roughly .010

So, zero lash and a quarter turn.

The "method" at which you find zero lash is up to you.

Sam.

 

Just watched the video... hard telling how far he compressed the plunger. After it stopped ticking, he cranked it down 3/4... which is .030... which is 3 times what it should be.

The question here is... is, "when does it stop ticking"????

Does it stop ticking at zero lash?

Does it stop ticking at .010 compression??

Does it stop ticking at .020 lash???? (which is what it should be to be about right)

I don't really know.

Sam.

 

you better check to see if your man broke the new cam in or not. That is priority #1. Don't even start it unless you know.

 

I'm going thru the same ting right now. I would like to do it right. Withonly 500 or so mls on my new mill I don't want to screw it up & I'm a little new at this stuff. Any help from you guys would be great. PM me w/recomendations

 

Look up the EOIC method of adjusting valves. It's the best way.