Ok......got the cam in and roller rockers on. Question is now about adjusting valves. Followed the procedure to get TDC for cylinder #1. My question is about finding zero lash. I am twirling pushrod until I feel a change in resistance. I guess were I am confused is were the resistance begins. If the rocker arm is making no contact, it twirls effortessly. As I tighten the hex nut as soon as I feel some resistance I stop, and go 1/2 turn more. Am I stopping too soon? Is the resistaance supposed to be were twirl gets really noticeably tighter? I dont want to end up with bent pushrods, but I dont want the rockers clattering either. Any advice is appreciated.

 

when you are using your index finger and and thumb to turn the pushrod when your fingers stop turning and start sliding is the moment you have just gone beyong zero lash.... just back off until you can turn it again in your fingers....after doing this for a couple of times your fingers will lose strength and will get oilly and start slipping right at the moment of resistance...

remember you want TDC of compression stroke not exhaust stroke....ask me how i know...

 

BTDT on a 351C....never again!

 

BTDT???? whats that ? i see you were working on a ford but i don't know the acronym

 

for TDC on cpmpression stroke, rotated the crank till both valves are closed on number 1 and timing marks are at 12 on crank and 6 on cam sproket. Reading your post, i believe i was being to conservative with my stop. Will try again as you suggested. thanks.

 

i don't know about the alignment on the cam sprocket, i adjusted mine with the timing chain cover on and it took me about three cylinders and one post before i realized i was on the exhaust stroke. so i went back to the basics as was suggested and followed the the valves on the number one cylinder and confimed that the intake valve had opened and closed and then up to TDC..its funny how you get dumb when you get excited about getting the new engine started....good luck

 

move pushrod up and down until play stops, that is zero . twirling is fine for pros, not good ur 1st time.

 

Been There Done That. BTDT

 

If you have a VERY thin feeler gauge, like .002, you can use that. It's close enough to zero that it's negligible. The resistance is something you learn -- it can be a challenge for those of us who are, well, "challenged."

 

I adjust my lash in firing order turning the crank 90 degrees at a time. If I start with #1 at TDC of the firing stroke, I ensure that the lifters are on the base circle. By doing it in firing order, I have never had a problem.

Here is a link to Lars' valve lash tech tip: https://www.corvetteforum.com/techti...=116&TopicID=3

 

i even used an index tape on the harmonic balancer to mark the 90*

 

I adjust lash after having warmed the engine up and with the engine idling, valve cover off and a good 1/2 drive socket wrench, I:

Back a rocker lock nut off until I hear rocker noise, turn it 'in' to the point when the noise stops (my understanding is that this is just past the point of or AT zero lash) and then 1/2-3/4 turn beyond that. I have found that with approx 30k miles on my rebuild that 1/2 turn past the point of when the rocker noise stops just doesn't do it anymore; I get too much valvetrain noise. I currently have all rockers at 3/4 turn 'in' from the point where the rocker stops 'clacking'.

 

I just bought a DVD on engine removal, rebuilding and installation and it covers this. Made by
www.boxwrench.net
Good stuff and apparently they are coming out with more videos.

 

I agree. People always call me AFTER they use the "twisty turny" method and have punched holes in their pistons, bent their valves and/or pushrods. Then they ask... "I followed the Service Manual Procedure", what did I do wrong?

The twisty turny method is described in just about every service manual I have used.... and it's a bogus method.

Why? Because the lifer plungers do not always exhibit a uniform amount of back pressure or resistance to compressive forces. The point at which the pushrod stops turning depends on how hard your built in rotometer is set. Just like your built in torgue wrench for tightening main bearing caps. 99% of the time, this is not zero lash.... it's almost always PAST zero lash. When I was still in business as a Machine Shop owner/operator, I gave seminars on this procedure. On any given day, I could take a new box of lifters off the shelf and use the twisty turny method of adjustment with them... and get bogus lifter pre-load settings every time. My "students" were amazed. It's worse with used lifters. The design of the lifter, the internal valving & spring, and the amount of oil currently in the lifter influence how much compression the plunger will take before your "twisty" stops twisting.... It is a non-determinate point, and it gets people into trouble... even the self proclaimed "pro's".

Zero Lash is when all slack has been taken out of the valve train with the lifter on the base circle of the cam... and in the case of hydraulic lifters.... when the push rod is touching but NOT pushing in on the lifter plunger. By the time the built in rotometer in your fingers says it's time, it's too late. I have seen (and shown others) hydraulic lifters compress with just the weight of the pushrod sitting on them.

Been preaching this for years on this forum... but I always get arguments. Take yer chances, pay yer money.

Do it this way.... forget what y'all read in books... this is real world experience... not an opinion.

Following the sequence you prefer, get the subject lifter on the base circle of the cam (lifter is not being raised by the cam lobe).
If not already loose, loosen the rocker until you can see/feel slop between the rocker, pushrod, and lifter.
Hold the rocker firmly against the valve tip.
While continuously moving the pushrod -GENTLY- in the direction it moves while running (up & down) slowly tighten the rocker nut until you can see/feel no clearance... watch the lifter plunger.... make sure it does not compress.... it may be rock solid, or it may be exhibiting no resistance to compression at all, so you have to watch it carefully. If it starts to compress, you have gone past zero lash. Back the nut up & try again.

At zero lash.... adjust the additional number of turns specified by the lifter manufacturer... varies based on manufacturer, thread pitch of the rocker studs, engine, etc,

I used this method in my business for about 30 years and NEVER had to re-adjust hydraulic lifters.... I put the valve covers on & was done.

 

I never rotate the push rods. I move them up and down until all play is gone then go 3/4 turn tighter.
For setting valves I go to top dead center and that is easy to find with the valve cover off, exhaust opens, closes, intake opens, closes and bring the mark to top dead center then use set certain valves , rotate to BDC and set other valves.
I have a chart on my shop wall outlining which valves to adjust.

 

too many guys agree
How could the twirl method be in so many books?
I bet it dates back to when solid lifters were the norm. Twirl works fine with solids.

 

There is a difference between "pure" and "applied" science, or between "theory" and "reality".

The people writing service manuals are not mechanics... most of them never get their hands dirty. It all looks good on paper.

If all lifters were manufactured so perfect that you would need a DNA test to tell the difference between them, then maybe, MAYBE the procedure would work.... sometimes. The oil inside also makes a difference.

Try taking one apart sometime & removing all but a trace of oil and reassembling it. Press on the plunger. Then compare it to one with oil in it. The difference in compressibility is directly correlated to how much twisty pressure it takes to stop the pushrod from turning during adjustment.... indeterminate.


Like .008 endplay for rear spindles.... just because it is "written" doesn't make it true. Can't learn how to ride a bike by reading about it.

 

it's too embarrassing for publishers to correct it. i'm sure they got tons of letters over the years. Even i sugar coated my advice - "it's fine for pros" (i lied to avoid confrontation with any old timers that might swear it works)
What does the assembly manual say? i can see the foreman at the vette engine plant telling a new guy DONT GO BY THAT

 

great info on the bogus twirl method definitely makes since.

 

Just out of curiosity what would David Vizzards motivation be to misinform people on adjusting valves?