1990 4.3 block and 1995 heads, which rocker tightening specs to follow?

[1990-190-freedom]

This is the 1st head project I've done, or even tore down the engine this far. The boat has a 4.3 from 1990 but the heads are from 1995 (forgot to winterize in a non-cold state & had a shop replace the heads in 1997). Forward to 2023. I just got my heads back from the machine shop and I have them on and I was following the "lashing technique for 1990 when tightening for the valve rockers, then I started to 2nd guess myself. Should I follow the 1995 version at 40 pounds tightening with the rockers or stay with the 1990 version of tightening with zero lash and 1 full turn?

Thanks for your help,
Matthew

 

[Bondo]

Ayuh,.... Welcome Aboard,...... I like the 0 lash, plus 3/4 turn myself,....

 

[Lou C]

I thought these changed when they went to the non-adjustable valve train. A 1995 should be pre vortec IIRC. Non adjustable was on Vortec only correct? That & roller rocker arms. When I did mine I used the factory spec of 1 turn after zero lash.

 

[alldodge]

Ayuh,.... Welcome Aboard,...... I like the 0 lash, plus 3/4 turn myself,....

I have to agree, unless the push rods and rockers are changed they will be different length from the vortec IMO

 

[1990-190-freedom]

Thanks all! I'm mechanical but never torn apart a boat or car engine & the rockers was the part I just felt unsure. I ended up doing 0 lash and a full turn but the full turn didn't always happen as the nut stopped/bottomed out. So then I went back and did 20#'s on each one since I remembering taking them off and it felt like 20-30#.

 

[Lou C]

Something there doesn't seem right. Is the # you posted the casting #?

Cylinder Heads

machineworldny.com

I plugged in that # and it looks like you have the right heads for your range of model years

What's the block casting #? I see you have the later model roller lifter alignment parts, mine has the older style tin piece in the cam valley.
PS I have the same engine but 2 years older. Pre-vortec but with the roller cam, when I got reman heads I made sure to match up the casting #s to the originals.

GM 1987-1992 4.3 LTR /262 ci - V6 cyl Cylinder Head - Casting : 14098768

machineworldny.com

this is the one my engine has, these have press in rocker studs instead of screw in.
The only difference I can see is that yours have the screw in studs instead of the pressed in studs, I wonder if the pushrod length is different?
PS what I could see in comparing the 2, is that the threaded area on the stud seems to extend lower on the ones I have with the pressed in studs, vs the ones you have with screw in studs. That might explain why you are running out of adjustment.

 

[Bondo]

Thanks all! I'm mechanical but never torn apart a boat or car engine & the rockers was the part I just felt unsure. I ended up doing 0 lash and a full turn but the full turn didn't always happen as the nut stopped/bottomed out. So then I went back and did 20#'s on each one since I remembering taking them off and it felt like 20-30#.

Ayuh,..... Each cylinder has to be at it's Tdc, 1st,.....

 

[Lou C]

In the OMC shop manual they have the GM procedure for adjusting the preload or the depth of the plunger of the hydraulic lash adjuster....I did mine that way, had no problems even though it was the first time I ever did it.

 

[flashback]

I can't help ya much but I had an old 1980 model 350 that had the studs pressed into the head and it was bad about jacking the studs loose. I had to knock them back in and pin them..

 

[alldodge]

Been thinking about this and zero lash would not be the way to go "IF" your not using lock nuts.

What about finding out the push rod length of the original and a vortec? Might be worth the change to go with rods and rockers and not worry about it. Keep same lifters

 

[froggy1150]

The way I have always done Chevys with hydraulic lifters and rockers like that is I have a set of little clips that cover the oil hole on the lifter. Set pushrods just past touch. With Warm motor and clips installed loosen stud nut til lifter rattles, tighten til just quiet then 1/4 turn.

 

[1990-190-freedom]

The rockers are non roller style. I have the engine buttoned up and just sitting right now, haven't even fired it up due to work and kids. I follow the lash technique in the manual but with 2nd guessing myself I'm going to do a compression test to see if they are too tight, before firing it up. When I had the heads off I got TDC 100% and marked the fly wheel a new mark( since other boat shops had 3 other marks on the wheel that was at least 30%-BTDC ). Then I dropped the distributor in at 6% BTDC as my air cleaner cover sticker says. Reason I took this project on was there are no good boat shops in Phx besides the 1 that is backed up 6 months.

 

[Bondo]

When I had the heads off I got TDC 100% and marked the fly wheel a new mark( since other boat shops had 3 other marks on the wheel

Ayuh,..... As I mentioned earlier, Each individual cylinder has to be at itself's Tdc, when adustin' the rockers,.....

 

[Lou C]

Here’s how I did mine…
PS
I found it easier to judge when the lash was at zero by trying to lift the pushrod up and down ,vs turning it.
Also, mark the cyl #s and Intakes and Exhausts with a piece of tape so you don't get confused.

 

[1990-190-freedom]

OK, I finally had some time to work on the old boat again and I starter her up with earmuffs and the heard some slight ticking. I also noticed I have the plastic lifter brace so I tried the 1995 method and with ear muffs she sounded great so I took her out to the lake and did a couple 500 yard runs. The 1st run was great but on the way back it did a small backfire(hoping I didn't mess anything up). I tore her down last night and did the 1990 lash plus 1 turn but I came onto a miss print that I think affected my original test with lash plus 1 turn. See attached 2 pages from the manual, it has #3 cylinder "intake" twice and no exhaust. I was trying to figure it out myself and at TDC on #3 with lash plus a turn the nut goes all the way down to the 1/2 round washer but all other cylinders the nut is just on with maybe 1-2 threads showing on top of the nut & not close to the 1/2 round washer.
Also curious how much oil comes out of other 4.3 rockers? Mine does about 1 drop a stroke even when brought up to 2000rpm & it doesn't seem like much.
Again sorry for the novice questions but this is new to me. This boat has been in and out of shops for 1 year, nickel & diming me & I just want to get it back on the water.

 

[Lou C]

I'd follow the ones I posted, (#14) they worked for me.

 

[alldodge]

It's a misprint
Me I pay no attention to books for valves. Turn motor until intake or exhaust is down. Then adjust the opposite valve that is not down. Mark with grease pencil and rotate some more until all have been marked

 

[Lou C]

The one I posted is right from my OMC shop manual which in turn is right out of the GM shop manual. I think you can trust that!

 

[1990-190-freedom]

Thank you! Working on her right now.

 

[froggy1150]

Hope you didn't roach your cam or lifter with a adjustment that was too tight