Thread: Valve adjust on Small Block 350

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Hi All,

Replacing heads on a 87 Blazer.

The problem was no compression on one cylinder. (#5)

Pulled the head.. Bent valve. 50k miles on crate motor. Driver was tootling down the freeway, long distance, and it started missing badly at about the halfway point.

Springs are fine.. It's the rotator equipped exhaust valve.

WHY???


Putting on a set of newly rebuilt GM heads as apposed to Mexican Heads(Crate motor origin).


Okay putting the new heads on. My usually very sharp mech buddy thinks that the new deal on valve adjustment is:

1) Bolt(torque) down heads.

2) Install push-rods and rockers.

3) Tighten down rockers until the play is gone then go 3/4 turn more. (ALL with the engine just static!) I think he's crazy! I can only imagine doing it with the engine running as; A) Valves that are not supposed to be closed will be left horribly loose as soon as Mr.Camshaft rotates to an open position. B) The lifters may have no oil in them and be bottomed as soon as the lash is gone during this static madness.

Am I correct?

Lastly, what 'is' the adjustment on this thing? Zero lash plus 3/4? or Zero plus 1?? Or ???

Thanks all, for your help.

Just did this on my car, if stock cam 1 full turn puts the travel 1/2 of the lifter, if not a stock cam about 1/2 to 3/4 of a trun, these are Hyd roller lifters correct?

Steve

With intake off,put lifter in bore,rotate engine untill lifter is all the way down on the base circle of the cam,install push rod,install rocker ,tighten it untill the push rod compresses the lifter guts past the retaining rings on the inside of the lifter body.Then repeat for every single one,There is a lot of play in there to work with,take the first one you install and go ahead and tighten it till it fully depresses the guts of the lifter ,then loosen ,and you will see the amount you have to work with, tighten the push rod approx 1/3 of the play you have inside the lifter body and all will be fine.Use this method ,to keep from doing it engine running ,and there should be no further adjustment .

Originally Posted by kcress

Pulled the head.. Bent valve. WHY???

My guess is either 1) you had a weak valve spring and because of this, the valve did not shut quick enough for the rpm he was revving. (as in passing another vihicle)
or 2) the valve stuck open for a split second due to carbon.

Originally Posted by kcress

3) Tighten down rockers until the play is gone then go 3/4 turn more. (ALL with the engine just static!) I think he's crazy! I can only imagine doing it with the engine running as; A) Valves that are not supposed to be closed will be left horribly loose as soon as Mr.Camshaft rotates to an open position. B) The lifters may have no oil in them and be bottomed as soon as the lash is gone during this static madness.
Am I correct?

It is impossible to adjust the valves without rotating the engine as you go. Yes he is crasy! Don't start the engine.
Many will be too tight in this method, and many will be too loose. I see bent valves. Do not adjust your valves till they bottom out, rather adjust them to the point where the push rod makes contact with both the rocker and the lifter. You will feel an ever so slight restriction as you turn the push rod to get the feel of things.

Originally Posted by kcress

Lastly, what 'is' the adjustment on this thing? Zero lash plus 3/4? or Zero plus 1?? Or ???

I would go with half a turn after I feel the push rod contacting the lifter and the rocker.
There is a sequence to do this in. If you need that, please ask. In other words, you need to rotate the engine to eight different positions to adjust 16 valves.

Do you have that sequence? We would use it!!

Ok, when looking at the engine bay from the front of the car, the cylinders on the right (driver’s side) are numbered as follows. The most forward is 1, then 3 then 5 and then 7. On the left ( passenger side) the most forward piston is 2, then 4, then 6 and then 8.

Turn the engine with the plugs removed (if you can rotate it without removing them, then that is fine) but do not rotate with the starter, just in case you already have a few valves adjusted too tight.
Firing order is 18436572
Rotate the engine and watch for the #1 exhaust valve to open half way, then adjust the intake valve on #1 and the exhaust valve on #6.

Next, rotate engine so that the #8 exhaust valves opens half way, then adjust the intake valve on #8 and the exhaust valve on #5.

Next, rotate engine so that the #4 exhaust valves opens half way, then adjust the intake valve on #4 and the exhaust valve on #7.

Next, rotate engine so that the #3 exhaust valves opens half way, then adjust the intake valve on #3 and the exhaust valve on #2.

Next, rotate engine so that the #6 exhaust valves opens half way, then adjust the intake valve on #6 and the exhaust valve on #1.

Next, rotate engine so that the #5 exhaust valves opens half way, then adjust the intake valve on #5 and the exhaust valve on #8.

Next, rotate engine so that the #7 exhaust valves opens half way, then adjust the intake valve on #7 and the exhaust valve on #4.

Next, rotate engine so that the #2 exhaust valves opens half way, then adjust the intake valve on #2 and the exhaust valve on #3.

One last thing. Rotate the motor where the timing mark is at 10 degress advance with the #1 piston valves both having been closed for the up stroke (compression stroke), set the ignition rotor to the #1 wire on the cap or rather turn the distributor base so that the #1 wire will line up with the cap, and wala. No back fire, just music.

Someone please double check me on this.

Just a nice, simple, structured procedure!

Thanks Denny, you saved me a lot of work. That's the way I always do it, very easy and a lot less turning over and over. And just so we dont mess up the new guy, not to be picky, but

the cylinders on the right (driver’s side)

.....right and left when you're talking about the car and engine, are as if you are sitting in the drivers seat. So, the driver's side is left, and passenger is right.

Hey Denny, I can see that working as well. In either case, the engine only rotates two cycles, both in the way you describe it as well as in the way I describe it. I only rotate the engine 90 degrees at a time as well, just at a different point of the cycle. I might try it your way next time.

In my eyes, you have described it adequately, but maybe for the new guy we should add that in your method number 1 has to be at tdc on compression stroke to start off. You did mention that both valves should be closed for that particular cylinder which says the same thing. But in the case of a mild cam with little to no overlap, it could cause confusion.

Actually I have heard of another method which involves only two positions of the crank in order to adjust all 16 valves but I think it only works on stock to mild cams. Maybe someone can post that method.

I used the section for hydraulic lifters on page 4 to do my valves: http://www.compcams.com/Technical/In.../Files/145.pdf

Ahh.. You guys are the greatest! This will help us immensely! We will be sooo happy to avoid the smoking, dripping, hot oily mess we are so familiar with..

Many Thanks!

Just a short question:
supposing the engine has been run before, then how can I be sure that zero lash isn't already a bit further down than the fully expanded position of the lifter? In use, the lifter compresses a little bit and stays there. Do all hydraulic lifters have springs in them to decompress them as soon as the pressure exerted by the pushrod is gone?
How would I set the lifters in an engine that has been run, lifters full of oil, but I don't want the mess? Is that possible to do correctly without the engine running?

MadMax here is what we experienced.

All the lifters were not compressed, they where all extended, (full length). This is because of the springs in them, I believe.

When we tried to compress them they would not compress at all, not in the least bit!! The associated valve just opened. This meant we really couldn't discover the "lifter piston stroke". We shelved that idea and instead used the method by which we rotated the pushrod until it stopped turning (very obvious point) then added one turn. You have to be a little careful because this whole '1-turn' results entirely in the the valve projecting into the cylinder. You could have a valve ram a piston even with the engine not running. So if you feel a sudden increase in pressure while adding the turn STOP! note where you are and come back in 10 minutes for the rest of the 1-turn.

With number one at top dead center we were able to adjust all but 6 valves. We then turned the engine 1-revolution and were able to do 5 more. Then we turned the engine another few degrees until the last lifter was obviously down and did it.

What we discovered MadMax was that after about five minutes all push rods could be easily rotated with the fingers again. So they will leak down. Of course this means you need to be kind of time considering when adjusting the valves. If you take 5 minutes to creep up to the 'pushrod-doesn't turn, zero-lash point' that one valve WILL NOT actually be set to 'zero+1-turn' but will be more than one turn!

We may be turning the key today. I'll let you know how things work out.