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Username Post: 350 valve lash SPECS        (Topic#261670)
Forum Newbie
Posts: 2

Reg: 04-21-11
04-21-11 08:11 PM - Post#2080128    

Hi - new a quick question..I know theres probably a million threads on SBC valve lash adjustment and trust me I think Ive read every one on the internet. But heres what I got..I have a 20' ski boat with a 1988 OMC 5.7L Chevy. All fairly stock. I just put a new top end gasket set on and Im adjusting the valves. Ive pored over about every option available on how to do it. Ive opted for the "running method" since Its so damn hard to turn the HB by hand while in the boat. I got it back running good but want to get it tuned for optimum BOAT performance. I need to know how much past 0 lash to tighten it. Ive read tons of "professionals" swearing on everything from 1/4 turn to 1 full turn. My pressing question is: What would be best for a BOAT engine - one that runs at 80% load & higher RPMs for pretty fair amounts of time (20-30 minutes) Would going MORE like 1/2 to 3/4 be better for sustained high-load/rpm applications? Or 1/4 to 1/2. I know the procedures for doing the adjustments..I just need some no BS advice for whats best for a boat application. I sure dont want any bent or burnt valves 20 miles out from the boat launch. Thanks guys..

Edited by Spyder202 on 04-21-11 08:12 PM. Reason for edit: No reason given.


Very Senior Member
Posts: 3272

Reg: 10-06-03
04-21-11 08:48 PM - Post#2080137    
    In response to Spyder202

Here is somethin i posted a couple of days ago:

"here is a good article I found. Its the EOIC method

Work one cylinder at a time. When the exhaust valve just starts opening, adjust the intake rocker(because, when the exhaust valve just starts to open, the intake lifter is definitely on the base circle)

When the intake just starts to begin closing, adjust exhaust rocker(again....when the cylinders intake valve just starts to close...the exhaust has to be on the base circle, which is why you can adjust it)

Start with the number 1 piston and follow the firing order.

back off all your polylocks at least two full turns. back off the setscrew in each one at least two full turns. turn the engine with balancer bolt or remote starter switch till #1 exhaust just starts to open. judge this by eye, you can see it the pushrod move up. spin the intake nut down to zero lash, confirm by rattling the pushrod up and down and spinning untill the play goes out. adjust the intake to 1/2 turn preload. run the setscrew down to lock, then give the nut another 1/16 turn to jam the setscrew firmly. go to number 8, turn the engine 1/4 turn, see the #8 exhaust pushrod start to move up, adjust the #8 intake. then turn the engine 1/4 turn, see the #4 exhaust pushrod start to come up, adjust the #4 intake as before. go thru the firing order 1-8-4-3-6-5-7-2. back to #1, turn the engine till the #1 intake valve goes to full open and starts to close. adjust the #1 exhaust at this point. turn the engine 1/4 turn, see the #8 intake go to full open and start to close. adjust the #8 exhaust as before. Give the engine 1/4 turn, see the #4 intake go full open and start to close.adjust the #4 exhaust as before. go the rest of the way through the firing order as before. Sanity check: when done all the nuts should be about the same height, all the setscrews should be about the same depth. If any are way off do that valve again.

By the time youre done....your going to follow the firing order through twice. Set all the intakes first...going a 1/4 turn each time and following the firing order.....then just keep on rolling straight back through the firing order again, setting all exhaust, 1/4 turn of the engine between each cylinder/rocker.

That'll keep things straight forward and able to be kept track of. Ya cant just wing it because you have no idea where the lifter is at on the cam when you run the rockers down, and they definitely cant all be on the base circle at the same exact time.

If you wanna go back through and adjust them runnning, you can....but no need if you dont want to. Hit the engine with an oil pump primer. Run it for a bit, rotate the engine 1/4 turn at a time through two full revolutions, letting it run for a bit at each position. By now the lifters should be flowing a steady stream of oil with the plungers totally pumped up. If you set them all as noted above, and preload them all 1/4 turn to 1/2 turn....they ought to be where they are supposed to be at this point. You can re-adjust if youd like though, but if its quiet...Id leave it be. "

you dont necessarily have to do it this way. Once you get a good feel for it and have done it regularly....maybe you might just want to work the intake and exhaust on each cylinder instead of all intake, then all exhaust. You just have to be familiar with where you are at concerning TDC and the firing stroke and being sure your on the base circle(going back to EOIC).

About preload.....whos lifters are they?

Here is why lots of guys go to looser lash (like 1/4 turn) on a performance build.

For one...if you float the valves, the engine recovers faster. If you preloaded to the point that you put the plunger all the way down in the lifter, and then floated the valve.....that plunger can actually pump up upon losing control of the valve/lifter.

You cannot compress a liquid, so the only way for the preload to go back to where it supposed to be is for the oil to eventually be squeezed back out of the lifter, and the plunger drop again.

If you barely preload them, and then float valves...the plunger has a real short travel before pumping up to the top of the lifter. Recovery is faster because it wont take as long to squish that oil back out to regain that small amount of preload.

The factory used tighter preload settings because the valvetrain typically runs quieter with more preload. Quiet, smooth performance was more important in most cases for OE manufacturers than high rpm performance.

But...I do ask what lifters, because some lifters do like more or less preload. I might talk to the lifter manufacturer and tell them your usage, and ask em what they think about preload, and even oil viscosity. For steady high rpm performance below "redline", but sustained at higher rpm either way....Id probably try 1/4 to 1/2 and see how it feels somewhere in there.

Forum Newbie
Posts: 2

Reg: 04-21-11
04-21-11 10:48 PM - Post#2080158    
    In response to greg_moreira

Cool - good info..Thanks. I have the procedures in order - just lookin for the proper amount of preload. I gather from that 1/4 to 1/2 woube be the ticket. Think Ill go "3/8ths"

Senior Chevytalk Moderator -- Performance Subject Matter Expert --
Posts: 17151
Age: 70
Reg: 03-16-01
04-22-11 06:39 AM - Post#2080233    
    In response to Spyder202

"go to looser lash (like 1/4 turn) on a performance build."

Ive always preferred to get the engine temps up to about operational temp levels and adjust the valve train on hydraulics for 1/4 turn in from the point they just stop clicking at idle as it tends to maintain the best compromise on both low and high rpm valve train stability


Posts: 158

Age: 65
Loc: Mpls, MN
Reg: 06-11-11
02-28-12 09:22 AM - Post#2196252    
    In response to greg_moreira

A few questions. I have been putting a few emails on the Chevys 40s forum. I have a '47 chevy and I put a '59 chevy 235 motor into it. It has hydraulic lifters. I'm pulling the lifters one at a time due to cleaning / sticking etc. I was under the impression I need to preload (load lifter with oil) lifter. is that true? Next on valve adjustment, I have heard and see so many different ways. This is what I was going to use.
One cylinder at a time
Rotate engine until # 1 exhaust valve begins to open, adjust intake to zero lash plus 1/2 turn.
Rotate engine until #1 intake valve is fully open, adjust exhaust vavle to zero lash plus 1/2 turn
Then to # 2 etc
What do you think about the two questions.
Thanks for your help!!

Posts: 620
Age: 73
Loc: Shellman Bluff, Coastal G...
Reg: 01-08-03
02-28-12 11:21 AM - Post#2196298    
    In response to Daves4757

Dave, the "preload" we've been talking about over in your other thread is not "loading the lifter with oil", it's the turns (1/4 or 1/2 or whatever) on the adjustment from zero lash, which I think is preloading the internal spring.



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