Jughead

I'm working on a 454 with a solid lifter cam.

I'm doing initial valve lash with new rocker arms. Measuring 0.022 intake and 0.025 exhaust. At 0 on the timing mark I have #1 and #6 at TDC. At the 5 o'clock position I have #5 & #8 at top of the cylinder.

7 O'clock---#4 & #7
11 O'clock---#2 & #3

Chilton states to start at TDC #1 and adjust:
Exhaust: 1,3,4,8
Intake: 1,2,5,7

Rotate 360 degrees and No 6 should be at TDC. Then adjust:
Exhaust: 2,5,6,7
Intake: 3,4,6,8

But in my observations #1 & #6 are at TDC at or near together. :confused: Why is it necessary to rotate from #1 TDC back again to to zero on the timing mark and is this the correct proceedure?

Thanks
Len

Larry B.

What you need to remember is that ... When #1 is TDC on compression stroke... #6 is TDC on exhaust stroke. Think about that and you'll undrestand.. Sometime we overlook the obvioius.

Chuck Gongloff

Believe your Chilton manual. Another point is that you have 2 crank rotations for each cam rotation....so you have 720 degrees of rotation...therefore you have a cylinder firing every 90 degrees on the harmonic balancer.

SO...to my way of thinking, if the timing mark is 12 o'clock, #1 fires there, then #8 fires at 3 o'clock, #4 fires at 6 o'clock, #3 fires at 9 o'clock, then you're back to the top when #6 fires........and so on. Chuck

Larry B.

Chuck..that's a good explaination. It is harder to explain cam,crank and distributor timing. I have tried numerous times to explain why you can't just move the distributor a tooth when the timing chain jumps.!! :banghead: Engines need fuel air and spark to run but.... It all has to happen at the right time too.


[Modified by bluevetteman, 9:44 AM 7/19/2003]

Jughead

Ok. so how can I determine when #1 is on the compression stroke....That's where I start to set the lash? #1 is at the top of the cylinder at Odeg, 360 and 720! :confused: I can see the top of the piston thru the spark plug hole at each of those positions. :confused:

On the compression stroke, will the intake rocker arm on #1 just start to tighten as the balancer approaches zero? And the rocker arm on #1 exhaust will tighten 360 deg later? :confused:


[Modified by 1970 Stingray, 10:55 AM 7/19/2003]

Matt Gruber

good question!
1 vs. 6
the wrong one will be at overlap, one valve opening and the other closing.
the correct one valves will be asleep. :sleep:
(not moving at top of compression stroke)

Jughead

So I was wrong, if #1 is at TDC compression, both rockers should be loose. Just trying to get my bearings here(engine humor).

Larry B.

Correct! When the#1 cylinder is on compression both valves should be closed so the rockers are loose. This is where you set the lash. I prefer to adjust them in the firing order rotating the crank m90 degrees at a time. The book method is a little confusing and it's easy to get mixed up. It is just a little slower to do one at a time but you can trust it.

Matt Gruber

:iagree: with a solid cam, you are safer this way. just mark the balancer with chalk

Jughead

Thanks for enlightening me guys. I think I got it now. :lol: Matt, I can see the timing mark clearly, the engine is on an engine stand. :D

Jvette73

I like the 90 degree rotations and folloe the firing order myself too. Its one of the faster ways.

Another fool proof way is to do like this. You have an exhaust and an intake for each cylinder. Whenever either one of them is all the way open for a particular cylinder, the other is on base circle and in a good position for adjustment. example: #1 cyl intake valve is all the way open, then adjust exhaust valve for that cyl. use a small piece if masking tape to mark the rockers to remind you which ones are done as you move along.

Jughead

But how can I determine when #1 intake valve(or any particular valve) is completely open just by looking at the head & rockers? What if the intake is on already?

Larry B.

That is the reason I do them in the firing order. Then you know for sure that both valves are completly on the back side of the cam lobes and not partly on the ramp.

GDaina

how I do mine....only way.....take your harmonic balancer to a reputable engine builder/machine shop, they can degree your balancer, the cost is minimal, and after that, it's a walk in a park.

Chuck Gongloff

A "sure fire" way to determine if #1 is coming up on the compression stroke vs. the exhaust stroke is the old "thumb" method. Rig up a remote starter button, or have your wife/bud bump the starter. Remove #1 spark plug, and put you thumb over the spark plug hole. Bump the engine over. When #1 comes up on the compression stroke, the compressed air will pop your finger off of the hole. When this happens, look at the timing mark. Line it up with the timing tab using a breaker bar and socket. You've most definitely got #1 at TDC on the compression stroke.

You can mark your own balancer. Use the formula "pi X diameter" to determine the circumference of your balancer. Then divide that number by 4. Then measure off that amount, and mark it with chalk, or I prefer typewriter "white out". You'll then have 4 equal marks around the balancer, each 90 degrees apart. Adjust your valves. I usually "add" .002 to the "hot" measurement when adjusting them "cold". After you've got the thing running, then adjust them again "hot" to the specific lash. Chuck

427Hotrod

Lots of good info here....

With large cams sometimes it's real tough to get things on the base circle without lots of experience.

Here's how I do it.

You're right on finding compression stroke of #1. Both valves should be closed.

But......it really won't matter if you follow this method.


Slowly turn or bump the engine with starter and watch valves open and close. Easiest to start at #1, but it doesn't really matter.

Watch the EXHAUST valve just start to open. Not critical how much, just watch valve START to move. At that point, adjust the INTAKE valve.

Now rotate it some more (in direction of engine rotation) and watch intake valve. Watch it go all the way open and then start to close. When it is almost closed, adjust the EXHAUST valve.

INTAKE closing....set EXHAUST valve.
EXHAUST opening.....set intake valve.

That's how I do it and it will always work no matter no matter what engine you are working on.

I also set them cold usually. It's awful tough to set valves hot while engine is in the car. The valves will cool and clearances will change as you go through them all unless you re-run engine somewhere in between or unless you are VERY fast.

Setting them cold allows you to be sure that no matter what happens during heat cycles/expansion rates etc. they will all be set the same.

You have to set valves a few .000's tighter when setting them cold. Aluminum heads/iron block...I usually set them .005-.006 tighter than spec when cold.

JIM



[Modified by 427Hotrod, 1:06 PM 7/20/2003]

MotorHead

Here's how I do it, when one cylinder is on the base of the cam another is in overlap follow this guide :

1...8...4...3
6...5...8...2


When #1 is on the base of the cam #6 is in overlap, by turning the crank slowly you will see the exhaust valve closing and the just when you see movement on the intake valve or you can see they are both equal then you are in the right spot to adjust the exahust and intake of #1 cylinder. I don't think this method is difficult to understand at all.

Now rotate 90 degrees and you will the same thing happen to #5 meaning #8 is ready to adjust.


[Modified by MotorHead, 1:37 PM 7/20/2003]

Jvette73

You can watch the pushrod fo a particular cylinder rise up as you turn the engine over. When its as high as it will go then you can conclude that its on the top of the lobe. At that point the other valve for that same cylinder must be entirely on the base circle and in position for adjustment.