Hot Rods Trying to set lash the proper way on a SBC 350!

Hi guys! I have been trying to set the lash on my SBC 350, I have been following the EOIC valve lash settings to the T! (Haha, at least from what i been following, exhaust opens on cylinder #1...adjust intake on cylinder #1, hand turn engine crank and wait for intake to open on #1...then set lash on exhaust valve...so on and so on) this is with a mild cam, roller rockers and hydraulic lifters...my question about this is that everyone talks about shaking the push rod up and down and as soon as there is no up and down movement, twist the rod in your index finger and thumb until there is tension, or it starts to get some tension while twisting ...WTF does that even mean? Hahahaha, sorry...but does that mean you have to have a bit of a hard time twisting it in your fingers? I tried this and then gave it a 1/4 turn to set the preload and my truck started right up, but was popping through the exhaust and was at a high rev..it scarred me so i shut it down. I then removed the valve covers, spark plugs and then reset all the valves again using the EOIC method. This time i just moved the push rods up and down until all up and down movement was gone, once i found zero lash, i set the preload to 1/2 a turn and locked the set screw. Put it all back together and started her up, fired up quick but it still pops out the exhaust on acceleration. What is the proper way to set valve lash on a mild cam, roller rockers and hydraulic lifters, do you just remove the up and down movement then add your 1/4, 1/2 or 3/4 turn? Or do i need to twist the rods in my fingers for tension and then set my preload...i just need to move past this troubleshooting so that i can move on to other scenarios...Thank you guys!

 

If it is a new set of lifters they are not pumped up out of the box. I have always adjusted new hydraulics while the intake manifold was off. Tighten the rocker until the slack is out of the valve train, then tighten the rocker while watching the plunger on the top of the lifter. When you can just put a paper clip between the plunger and retaining ring... You are there.

Doing it with the intake on you can get fooled by the plunger... It can be pushed down pretty easy so you probably adjusted all of the slack out, the plunger hit bottom and when you added 1/2 turn... You unseated the valve. Back off all of the valves one full turn and fire it back up. After it runs a very short bit you may notice some ticking lifters that quickly get quiet. When that happens... Readjust them! You should be good to go... Just break the cam in.

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tighten down til no slack then spin with your fingers as you tighten a bit. When you feel resistance then 1/2 trun should do it BUT are you sure you are setting them at proper with your method? If as you say, hydraulic then try this
#1 position-then adjust ex-1,3,4,8 int 1,2,5,7 then on #6 position ex 2,5,6,7 in 3,4,6,8 get on #1 position-look at mark on timing tab and damper. Then spin around til the mark comes up again-#6 This is from a chevrolet factory manual.

 

This is from Crane Cams, I go 3/4 turn;
In order to adjust the preload the lifter must be properly located on the base circle or "Heel" of the lobe. At this position the valve is closed and there is no lift taking place. You will need to watch the movement of the valves to determine which lifter is properly positioned for adjusting.

1. Remove the valve covers, and pick a cylinder you are going to set the preload on.

2. Hand rotate the engine in its normal direction of rotation and watch the exhaust valve on that particular cylinder. When the exhaust valve begins to open, stop and adjust that cylinder's intake rocker arm. (Why? Because when the exhaust valve is just beginning to open, the intake lifter will be on the base circle of the lobe, the correct position for adjusting the intake.)

3. Back off the intake rocker arm adjuster and remove any tension from the pushrod. Wait a minute or two for that hydraulic lifter to return to a neutral position. The spring inside the lifter will move the pushrod seat up against the retaining lock if you give it time to do so. (If you are installing brand new lifters they will be in the neutral position when they come in the box.)

4. Now spin the intake pushrod with your fingers while tightening down the rocker arm. When you feel a slight resistance to the turning of the pushrod, you are at "Zero Lash". Turn the adjusting nut down one half to one full turn from that point. Lock the adjuster into position. The intake is now adjusted properly.

5. Continue to hand turn the engine, watching that same intake. It will go to full open and then begin to close. When it is almost closed, stop and adjust the exhaust rocker arm on that particular cylinder. (Again, when we see the intake almost closed, we are sure that exhaust lifter is on the base circle of the lobe.) Loosen the exhaust rocker arm and follow the same procedure described before in steps 3 and 4 to adjust this rocker arm.

6. Both valves on this cylinder are now adjusted, and you can move on to your next cylinder and follow the same procedure again.

 

Take the valve cover off and cut a piece of card stock to fit next to the springs and rockers. Place it just inside of the valve cover rail on the head to catch the oil.

Fire that puppy up and go down the row one at a time, and back each one off until it clacks, then tighten it 1/4 turn. When your done, shut it off and do the other side. Good to go!

I hope you didn't bend an exhaust valve already.

 

If you want to adjust while running, we used to take a junk VC and cut the top just enough to adjust lifter/rocker. You can even get fancy and use a hole saw cutter strategically cut holes directly over adjuster nut. Less messy this way...............................

 

^^^^ this too-got an old valve cover cut like this.

 

Ok, i am using all the parts that are in the truck engine now...i just wanted to adjust the valves just to be sure that it is all good. No new parts at all except for spark plugs and a new distributor. The engine needs reconditioning, so i rebuilt the carb, changed out to new 8mm wires, spark plugs and entire distributor, along with a new Holley red series fuel pump....Fixed fuel level sending unit and new air and fuel filter. Truck starts up easily, just pops out the exhaust when accelerating ...its starting to get to me as it has been 3 months trying to fix this issue.

 

Is a 3/4 or 1/2 turn to much? At zero lash? Oh boy...

 

I will try this method to the T, i dont mind soing this again and again till i get it right...thanks

 

1/2 turn would be best for you.................................
On the twirling thing, I don't do it that way anymore. Just wiggle pushrod up and down till no more slop is felt than 1/2 turn. I do twirl only to see if I can feel a bent push rod.
Like said hope you haven't bent a push rod.
Could also be a broken inner or outer spring, inner being hard to see..............................

 

I can still spin all push rods freely...after finding zero lash...i think it is in my best interest to do this with the intake manifold off, to check all my rods...if all these checks out fine, i will check my carb jets, i am thinking the primary jets are fine since it idles well?

 

Have you checked your Firing Order is correct?

 

Yes, all good! 1-8-4-3-6-5-7-2

 

Don't get to much going on at one time, if pushrods are seated in lifters and rockers there's no reason to take off intake, JMO..............................

 

If you go 3/4 turn you are at or near the bottom of the lifter adjustment. This could cause problems if the lifter pumps up. The valve may not seat properly, causing it to backfire.

On the other hand, the rocker arm geometry needs to be in the middle of the arc of travel to get the most lift for that cam profile. It could be 1/4, 3/8, 1/2 or 3/4 turns to be correct. But right now, you have it backfiring and you need to back off until you get it running good.

That's why I only go 1/4 turn after it quits clacking while tightening it.

I'd also be checking everything you have messed with. Wires, coil, distributor cap, etc. A weak coil can raise havoc and backfire too.

 

Did you put a Timing Light on it. You said it was in need of Reconditioning. Check timing Chain play with the Crank Shaft looking @ your Dissy Rotor. Valve Adjustment is pretty simple to do, The way you Described it should have been Pretty Close. All the Replies are pretty much saying the same thing. Was Engine running like Shit before you started.

 

Ok, i got a question...so i did notice that when i start the engine for the first time after doing all these adjustments...the engine starts off like its ready to take off...then it actually starts to idle just fine...is this normal? maybe the first setting i did with finding zero lash and then setting 1/4 preload was the right setting...oh, and my spark plugs are very sooty when i take them out, but i havent opened her up on the highway yet, just parked and idling...

 

Your timing is way off, or your advancing to much, new dizzy?
Take the vacuum advance line off of where ever you have it connected to and plug the vacuum port sores. Take it for a ride and report back....................................

 

Do you own a vacuum gauge and a compression tester ? How about a leak down gauge? Sounds like you have a problem that can be mechanical and be diagnosed with some basic tests.
Your method so far has been what we used to call shotgun mechanics. Throw enough stuff at it and you might hit the problem. Go back to basics and you will probably find the problem.

 

Broken or weak valve spring? Sticking valve? Burnt exhaust valve?

You may be expecting too much from a valve lash adjustment.

 

I like to go conservative especially with a flat tappet cam, I'll approach a 1/2 turn and that's it. Once I get the cam broken in, then I do it running and do a 1/4 turn, let the engine settle and then another 1/4 for a total of a 1/2 turn. Or follow what the cam/lifter instructions suggest.

 

Hey guys read post #8 he doesn't have a new motor or cam. He's just working on an old motor. Sounds as though it might not be valve lash at all. As suggested check what you've done as far as timing, firing order and because you've been changing valve lash redo it. One question. Was it doing this before you started changing parts?

 

You mentioned locking the " set screw", there is no set screw just a locking nut that you don't touch again once you crank the nut down 1/2-3/4 turn.

 

I do not have these tools and i have never really worked on a SBC, so i was trying to do basic trouble shooting, but the basics are advanced for me, i will try to ask my buddy for his compression tester. I was about ready to buy all new rods, springs, lifters, and a stock cam since this will be my daily driver, but as you say...hoping to throw parts at it may be what i am doing...it starts up fine, but pops on acceleration, previous owner said he went through at least 3 carbs...i have the the 3rd one still on it and it starts and sounds just fine, so i am trying valve lash just as a final test, before diving in the engine internals.

 

Your not by any chance using some weird adjustable pushrod??

 

It's been a while since I've done this and I'm not an expert nor am I as smart as most. And at the request of the families, all names have been changed to protect the innocent.

But I had good luck doing it the messy way, engine running, and the "1/4 turn" OR LESS for racing and high RPM applications. I was taught that less pre-load meant less chance of lifter pump up and valve float and could net you 500+/- more RPM. Plus you get all the valve specs you paid for in your cam. I found that to be true in my case. The negatives are you're walking closer to the edge of the cliff, more chance of mistakes, do-over adjustments, burnt valves, etc. For the street, where you're not pegging the tach, a 1/2 to 3/4 turn is not an issue and you don't have to worry about adjusting the lash as often. My personal theory is higher quality, name brand lifters shouldn't be as prone to pump up but I don't have anything to prove that one way or the other. As always, I remain subject to correction by my betters.

If you really like a challenge, try installing and adjusting a set of Rhoads lifters. Thankfully my minds pretty much a blank about doing that. All I recall is the solid lifter sound effects and more torque down low after it was done.

 

he has the rocker arms with the allen screw on them, roller rockers I think

 

My bad,I did not read the 1st post close enough. I'm more of a stock guy anyway so I'll shut up and defer to the experts. Ralphie