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jor 10-04-2007 03:56 PM

Valve Lash
 
87 Chev, 5.7L, TBI

Well, I decided to change out my valve stem seals to address a smoking issue. No prob, I figured. I put in new umbrella seals and o-rings for good measure. Then I followed the shop manual to adjust the valve lash. It says to put the motor at #1TDC and adjust intake 1,2,5 & 7 and exhause 1, 3, 4 & 8. Then go to #6TDC and do the rest. It says to take all the lash out, then go one more full turn. I'm spinning the push rod til it won's sping, then turn the ratchet 360 degrees for the one full turn. This thing now runs like crap and I can't figure out what I'm doing wrong. Thanks.
jor

DoubleVision 10-04-2007 04:04 PM

Back off the rockers and start over. When you get to the point of the push rod no longer spins, give it a little less than 1/2 turn. I`m not sure if your book is instructing correctly, but know the lifter must be on it`s base circle when you adjust the rocker, if it`s in a lift position the adjustment will be off.
I don`t adjust them this way, I always adjust them with the vehicle running. I adjust them until the ticking goes away, then I give them 1/2 turn in slow increments.

F&J 10-04-2007 04:08 PM

Just a guess; I think by checking for zero lash by turning the pushrods, you got them too tight rather than zero lash. You should have been moving the rocker back & forth while tightening to zero lash. I think by going until the rod wouldn't spin, you were way too tight already.

Quickest (but messy) way now, is to remove one cover at a time. Then at a low idle, back off each one til it Clacks loudly, then gradually tighten til the loud clack goes away, then do the one turn. If you do the one turn too fast, you will feel it miss a little as the hyd lifter "adjusts" itself.

Oil will fly all over if you don't have the little clip-on deals that are made for adjusting valves; maybe throw a clean rag over them to stop the spray.

Blazin72 10-04-2007 06:11 PM

Ditto on wiggling the rockers. If you're spinning the pushrod you should begin to feel a light drag when trying to spin it, not necessarily so tight it won't spin.

When you adjusted them did you make sure you were at #1 TDC compression and not on the exhaust stroke? You can verify #1 TDCC because #6 will be in overlap. When you went to the second set of valves did you rotate the engine one full turn before starting?

jor 10-04-2007 06:49 PM

Thanks to all. Yes, the damper mark was right at zero and the distributor rotor was pointing at #1. After I did the first eight, I rotated one revolution so the rotor was pointed at #6. From what everyone says, it sounds as though I just have them way too tight. I'll try it again in the morning. I'll stop at the "any resistance" point and then go 1/2 turn. Just to be certain, when you say 1/2 turn you are talking about 180 degrees, right. In other words, two 90 degree turns on the ratchet. Thanks.
jor

57 Chevy 10-04-2007 10:20 PM

If you got them so tight that they wouldn't turn and then went 1 turn down, then you may have bent the push rods. Take them all out and roll them on a flat surface to check them.

It sounds like you did everything right, you just didn't have the "no lash" touch yet. Rotate to you feel a drag and then one more turn. A lot of rodders only go 1/2 or 1/4 turn to keep the lifter from pumping up and hanging a valve open at high RPM. I'd stay with the ONE turn on your motor.

curtis73 10-04-2007 10:46 PM

I... uh, how do I say this... stroke the pushrod up and down like I was.... uh, you know, practicing for something.

When its loose you'll feel the pushrod go up and down. As you reach zero lash it won't anymore. Don't use spinning as your guide. Your low-duration flat tappet cam has very light springs, and you could probably spin those pushrods at full lift if you wanted, so its not a good indicator.

carsavvycook 10-04-2007 11:10 PM

re valve adjust
 
The best way to get them adjusted correctly is to have #1 at TDC and adjust the intake and exhaust valves on cylinder #6, next put #8 cylinder @ TDC and adjust the intake and exhaust valves on cylinder #5, next put #4 cylinder @ TDC and adjust the intake and exhaust valves on cylinder #7, next put #3 cylinder at TDC and adjust the intake and exhaust valves on cylinder #2, next put cylinder #6 @ TDC and adjust the intake and exhaust valves on cylinder #1, next put cylinder #5 cylinder @ TDC and adjust the intake and exhaust on cylinder #8, next put #7 cylinder @ TDC and adjust the intake and exhaust valves on cylinder #4, and next put #2 cylinder @TDC and adjust the intake and exhaust valves on cylinder #3.

In other words adjust the valves in the cylinder opposite in the firing order.

example: firing order 1843-6572 1843 adjust 6572 and 6572 adjust 1843



I always go 1/2 turn unless it has high rev lifters. Then I use a .002 thousands feeler gauge to adjust them at the valve. Check the rocker for looseness and also spin th push rod. You might have a collapsed lifter.

GREENBIRD56 10-04-2007 11:49 PM

TDC base circle
 
I realize this is my germanic heritage speaking - but my dear departed uncle who taught me about the 4 cycle engine - would only set dead engine lash on a cylinder that was at TDC. He told me that was the best guess a man could make at being on the base circle (with no dial indicators).

He (I) would pull all of the plugs and mark which hole they came from. Turn the engine to the compression stroke of cylinder one and stop with your damper and indicator aligned on the zero mark. Put marks on the damper at 90 intervals - measure the circumference if you have to, and divide by four to get the distance between them. With this method - you adjust number one cylinder - then turn 90 and adjust the next cylinder in the firing order and so on for two complete revolutions of the crankshaft. Its a dance to do this but you will get consistent results with a variety of cams and manufacturers. It works for solids and it works for hydraulics.

That gets you on the base circle, hole for hole - next you get experience with finding "near zero" lash. Making the lash tight enough to feel the "right" drag in the pushrod with your thumb and index finger is a tough learn. The polished seats for the pushrod ball ends and the lubricant will work against you. It is purposely designed to have minimal drag and what you have already found is that the pushrod will spin fairly easily even when preloaded. Zero lash is where the pushrod is on the lifter, the rocker is resting on the pushrod - and there is no clearance at the valve tip. Work at getting down close to zero clearance at the valve tip - the rocker ratio is working for you. For example, with a 1.5:1 rocker a .002 tip clearance is only about .0013 over at the pushrod end. A consistent (very) minimal clearance is better than preload.

You are trying to get consistent low clearance at the valve tip on every valve - even if you are wide by say .002 - it can't hurt. Because the next step is to turn down the rocker nut to compress the hydraulic lifter and apply the preload. Whether you turn the rocker nut down 180 or 360 - whatever - you are using the thread pitch of the stud as a sort of micrometer to establish the compression of the plunger. If you had .002 static clearance at the valve (as described above) - instead of a perfect zero - this compression will only be off by .0016. If you error by preloading the pushrod while trying to guess at the rotational drag the difference can and will be, a much higher value. There are preload schemes that deliberately set the valve tip clearance even higher than .002 - and then correct with the turn of the rocker nut.

carsavvycook 10-05-2007 12:19 AM

Quote:

Originally Posted by GREENBIRD56
I realize this is my germanic heritage speaking - but my dear departed uncle who taught me about the 4 cycle engine - would only set dead engine lash on a cylinder that was at TDC. He told me that was the best guess a man could make at being on the base circle (with no dial indicators).

He (I) would pull all of the plugs and mark which hole they came from. Turn the engine to the compression stroke of cylinder one and stop with your damper and indicator aligned on the zero mark. Put marks on the damper at 90 intervals - measure the circumference if you have to, and divide by four to get the distance between them. With this method - you adjust number one cylinder - then turn 90 and adjust the next cylinder in the firing order and so on for two complete revolutions of the crankshaft. Its a dance to do this but you will get consistent results with a variety of cams and manufacturers. It works for solids and it works for hydraulics.

That gets you on the base circle, hole for hole - next you get experience with finding "near zero" lash. Making the lash tight enough to feel the "right" drag in the pushrod with your thumb and index finger is a tough learn. The polished seats for the pushrod ball ends and the lubricant will work against you. It is purposely designed to have minimal drag and what you have already found is that the pushrod will spin fairly easily even when preloaded. Zero lash is where the pushrod is on the lifter, the rocker is resting on the pushrod - and there is no clearance at the valve tip. Work at getting down close to zero clearance at the valve tip - the rocker ratio is working for you. For example, with a 1.5:1 rocker a .002 tip clearance is only about .0013 over at the pushrod end. A consistent (very) minimal clearance is better than preload.

You are trying to get consistent low clearance at the valve tip on every valve - even if you are wide by say .002 - it can't hurt. Because the next step is to turn down the rocker nut to compress the hydraulic lifter and apply the preload. Whether you turn the rocker nut down 180 or 360 - whatever - you are using the thread pitch of the stud as a sort of micrometer to establish the compression of the plunger. If you had .002 static clearance at the valve (as described above) - instead of a perfect zero - this compression will only be off by .0016. If you error by preloading the pushrod while trying to guess at the rotational drag the difference can and will be, a much higher value. There are preload schemes that deliberately set the valve tip clearance even higher than .002 - and then correct with the turn of the rocker nut.


When you have a cylinder at the compression stroke, the cylinder opposite to it in the firing order is in valve overlap! A stock hydraulic lifter needs to have a pre-load of at least .030 to.060 thousands. A high rev lifter needs to be adjusted with a feelers gauge to .002 thousands clearance, also at the cylinder opposite of it in the firing order. I do agree with you that by marking the harmonic balancer every 90 degrees helps, and is more accurate than checking each cylinder for TDC. I personally use a degree wheel when I am assembling an engine. I started using these procedures as a "teen", after gaining 24 Horse Power on a dyno, on a Boss 302 Ford. I got 560 Horse Power out of it, as a High School Project.

GREENBIRD56 10-05-2007 09:14 AM

it takes two revolutions
 
??????
As I said before, it takes two full revolutions of the crankshaft to go through the firing order. There is an obvious difference between the compression stroke and exhaust stroke - even though both go to TDC position on every rotation. If you start with number one on compression - the second cylinder in the firing order will come up in 90 and so on - there will be a second piston at TDC in every case - but adjusting the closed intake valve on it risks being off the base circle. Every 90 the cam closes both valves on a cylinder - that's the one you want.

The micrometer effect of the rocker nut -
A 3/8-24 UNF nut moves the pivot down .042 per turn 6 flats = .007 per flat. For a 1.5:1 rocker this means that three flats (180) will compress the lifter plunger 3 x .007 x 2.5 1.5 = .035". If you turn it 6 flats (360) its doubled to .070".

For a 1.6:1 rocker - the math is 3 x .007 x 2.6 1.6 = .034" (in 180)

carsavvycook 10-05-2007 10:46 AM

None of this information is new to me at all. I have been building Hot Rod and Racing Engines for 36 Years. Just take a minute and look at my pictures. These pictures are of some of my latest work.

GREENBIRD56 10-05-2007 11:26 AM

yeah, well.....
 
I figure we are educating some young guys with all sorts of motors - so a pragmatic method of adjustment that only requires knowing the firing order isn't a bad start.

Chill out dude! My first flattie barked to life in '66 so my hair is white too - and the motor still lives in my dad's '53 Merc (which is a complete rust-bucket these days). Not worth a picture but it has run for forty years!

jor 10-05-2007 12:57 PM

Hey, thanks to everyone for the excellent information. I got it going this morning and actually drove that baby around the block. It's an 87 suburban that I repossessed last year from one of my kids. I decided to fix it up a bit and man, that did get out of hand. I ended up switching out the front and rear ends so I could get a ready made 4.10 gear ratio. I replaced all the bearings, races, bushings and u-joints. Then, I ran into the little annoying valve lash issue. Anyhow, it's running now so my next challenge is to get it through emissions. It still smokes even after the stem seals (oh, well, it was worth a try). I really enjoy reading the posts in this group. A lot of you guys really know your stuff. My situation is that I retired this year and I've always enjoyed screwing around with cars so that's what I'm doing. My stuff's not worth anything (67 & 68 Ford pickus, the Suburban and a 69 Blazer) but I have a lot of fun messing around with them. I know just enough after shade treeing for years to do some jobs well and really screw up others. Thanks again. Here's a photo of the Suburban. My wife will be ecstatic to see it off blocks (neighbors too). Thank God I don't have a neighborhood association!
jor
http://i102.photobucket.com/albums/m...a/100_5591.jpg

Notorious 10-05-2007 02:20 PM

Y'all are making this way too hard. Although many engines spec valve adjustment for all valves from two different positions in the 360* of cam rotation, which of course is at two crank positions a full turn apart, here's a fool-proof method for any engine with an even number of cylinders. All you need to know is the firing order for the engine you're working on. I'll use the SBC firing order since it's permanently ingrained in my feeble mind. 18436572 Now, split this in two like this
1843
6572
You can start the process from any position in the firing order by watching the rocker arms. And by understanding that any two paired cylinders will be at TDC at the same time. In this case and with this firing order, the paired cylinders are 1&6, 8&5, 4&7 and 3&2. One will be on the compression stroke and it's mate will be in the valve overlap period. That's the time at which the exhaust is almost closed and the intake is just starting to open. We'll refer to this as the point at which the valves for that cylinder are "rocking." Begin by hand turning or bumping the engine over with a momentary switch set-up hooked to the starter solenoid. Watch for an exhaust valve that is closing. Continue turning until it's accompanying intake valve just starts to open. Stop there. Now you adjust the valves in the paired cylinder to this one. This will be the one that is at TDC on it's compression stroke. This means that most assuredly that those two valves are fully closed. From this point on, you now know precisely where you are in the firing order and can proceed from there. Take note of the valves that were "rocking" and go to the next cylinder in the firing order. As you begin to turn it again, you'll see that it's exhaust valve is in the process of closing. Watch it just as before while turning the engine until it's almost closed and the intake valve for that cylinder just starts to open. Stop again and adjust the valves for the "mated" cylinder in the order.
Kapiche?


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