5.7L OMC valve lash adjustment

[HotKetchup]

Hi -got 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..

 

[Flysfloatsor]

Re: 5.7L OMC valve lash adjustment

Are they Hydraulic Lifters? Its 1/2 turn preload.
Youve got about a 2 millimeter "window" if its in there your golden. Too little they tap and the vlaves tont open all the way. Too much and youll wipe a cam lobe.

1/2 turn puts you righ in the middle of the 2 millimeter window. Hydraulic lifters use a "cushin" of oil that the push rods ride on. As long as your not "topping" out or bottoming out that cushin, its all the same.

 

[HotKetchup]

Re: 5.7L OMC valve lash adjustment

Yes Hydraulic lifters. 1/2 it is - thanks for the info.

 

[lynnboy021]

Re: 5.7L OMC valve lash adjustment

if you also tight it up to much the motor wont run cuz the valves will always be open..

 

[cr2k]

Re: 5.7L OMC valve lash adjustment

Books say 3/4. but 1/2 will work. You get very covered in oil doing this. Go slow and give the lifters time to bleed down between turns on the nut.

 

[HotKetchup]

Re: 5.7L OMC valve lash adjustment

Books say 3/4. but 1/2 will work. You get very covered in oil doing this. Go slow and give the lifters time to bleed down between turns on the nut.

Yep - Ill go around and set them with 1/4 turn then go back around and put another 1/4 on em. Now if itll quit SNOWING here in Spokane Ill get out there and do it tomorrow. Thanks for the help.

 

[cr2k]

Re: 5.7L OMC valve lash adjustment

If it quits snowing it will be raining so what is the diff?

 

[HotKetchup]

Re: 5.7L OMC valve lash adjustment

If it quits snowing it will be raining so what is the diff?

Yeah this weather is killin me...

 

[Howard Sterndrive]

Re: 5.7L OMC valve lash adjustment

on boats I always set valves with a compression tester
Crank on the starter, tighten each valve until compression drops off, then loosen until the rocker rattles, then retighten to split the difference.
all that 1/2 turn 3/4 turn stuff is great for cars. too risky on a boat. You can set them that way, but verify after with a comp tester. I like visual confirmation that my valve is opening and closing perfectly. too easy to burn one up in a boat with the continuous full load operation. Especially on my 80's V6 where the heads are just car heads.... stock chevy valves and springs.

 

[lynnboy021]

Re: 5.7L OMC valve lash adjustment

my book says remove lash and then just turn the nut one full turn. so you guys are saying that 1/2 is better then 1?

 

[Don S]

Re: 5.7L OMC valve lash adjustment

my book says remove lash and then just turn the nut one full turn. so you guys are saying that 1/2 is better then 1?

Come on now, you know that service manuals mean nothing and DIYers know more than anyone. Everyone that has ever touched a keyboard and put a wrench on a Chevy engine knows more about adjusting valves than General Motors, and GM is the one that gives the specs to OMC, Mercruiser, Volvo, PCM, and everyone else that sells Chevy engines for boats.

The "3/4 or one turn down from 0 lash" shown in manuals does nothing more than put the hydraulic lifter mid way of its working range.
1/4 turn will work just as well as 1 1/2 turns. The problem is, you aren't midway in the range and you may have problems earlier as the lifter wears from use.

The best thing you can do is follow what every everyone says and avoid the manual. Just pick the spec that sounds closest to what you want to hear and you should have a great running engine in no time.

 

[HotKetchup]

Re: 5.7L OMC valve lash adjustment

The best thing you can do is follow what every everyone says and avoid the manual. Just pick the spec that sounds closest to what you want to hear and you should have a great running engine in no time.

Will do...Thanks DonS. :facepalm:

 

[lynnboy021]

Re: 5.7L OMC valve lash adjustment

ok so tomorrow i am going to install new lifters, old ones was bad and from 0 lash i just do 1/2 turn and call it a day???/

 

[Don S]

Re: 5.7L OMC valve lash adjustment

ok so tomorrow i am going to install new lifters, old ones was bad and from 0 lash i just do 1/2 turn and call it a day???/

What??????? you never heard of sarcasm before?

The best thing you can do is follow what every everyone says and avoid the manual. Just pick the spec that sounds closest to what you want to hear and you should have a great running engine in no time

 

[lynnboy021]

Re: 5.7L OMC valve lash adjustment

dont know what sarcasm means but i dont wanna hijack this thread so i just started my own. i dont know its a old motor and i just want it to run good. when i went to pick up the new lifters the guy told me to do 0 lash then 1 1/4 or 1 1/2 turn.

 

[HotKetchup]

Re: 5.7L OMC valve lash adjustment

Wow 1 1/4 to 1 1/2 sounds pretty heavy to me. YOur cylinders may be kissing your valves after that much. Don S Yes Im all about some sarcasm. I threw some back at you. And no Im not trying to buck the manual with what I want to hear. I WANT to hear what works for my boat. Like I said Ive been scouring the internet for 3 days and the biggest answer I got from all the self proclaimed "professionals". (and yes they may be) that have been building 350's since they were making patty cakes out of diaper s*** is 1/4 to 1/2. With higher load & rpm applications going more toward 1/4. Not just from here but lots of other places. Chevytalk, Hotrodders.com etc etc. Im comfortably convinced that that is what i need. however lnnyboy thats the first time Ive heard of 1-1/4 to 1-1/2.

 

[lynnboy021]

Re: 5.7L OMC valve lash adjustment

well i think i heard 1-1/4 before not here but somewhere. but i do need some answers on my thread lol

 

[Joshua Nichols]

Re: 5.7L OMC valve lash adjustment

This thread has gone off the deep end..:redface:.
My book said 1 turn after you find zero lash too?

"On certain engines, the exhaust valve pushrods are longer then
those for the intake valve". Also said that so keep stuff in order

I have overhauled everything from a chainsaw to big industrial diesel engines.. Always went by the book on specs.. Always seemed to work.. So I always stuck with it...

"Loosen the adjusting nut on the rocker until you can feel lash (play in
the push rod) and then tighten the nut until the lash has been removed.
Carefully jiggle the push rod while tightening the nut until it won't move
anymore-this is zero lash. Tighten the nut an additional full turn"

 

[lynnboy021]

Re: 5.7L OMC valve lash adjustment

lmfao we should rename this thread... just saying.... how about my thread??? oh i think everyone went to bed lol

 

[cr2k]

Re: 5.7L OMC valve lash adjustment

I can see the logic in the compression method, but I would guess it has very little to do with a correct adjustment. How would you know where the lifter travel is?