Replacing valve springs

[msmith10]

Is there enough clearance between the bottom of the valve stem and the tappet to replace valve springs without removing the head?

[Dave Neptune]

Yep

Mark, you will need the head off to hold the valves down while compressing the springs.

Dave Neptune

[msmith10]

Thanks, Dave. Won't do it until I have to, then.

[romantic comedy]

I have seen, but never used, a compressed air tool, that holds the valves closed. You just put it in the plug hole, and hook it up to 120 PSI.

I dont know if it would work, but it is a thought. Plus you need a compressor.

[msmith10]

Removing the head isn't such a big deal. I haven't checked my valve lash in a couple of years and will probably do it this spring. I'm just preparing myself for a broken valve spring, although I don't really have any reason to suspect one other than my half empty cup expectations when it comes to boats.

[Al Schober]

Mark,
Don't know the age of your engine, but if it's old new and longer valve springs may be in order.
Last engine I did had the old short valve springs - with shims. Not my way of doing things - installed the longer springs. Want some shims?

[msmith10]

I'll open up the valve cover this spring to adjust valve lash. Too cold to do anything now. If springs are OK, I'm not going to do anything else. If they're not, then obviously I'll have to pull the head and replace them.
The motor is 1977, in good shape, most of its years in fresh water.

[lat 64]

Mark,
Don't know the age of your engine, but if it's old new and longer valve springs may be in order.
Last engine I did had the old short valve springs - with shims. Not my way of doing things - installed the longer springs. Want some shims?

Just to clarify; I believe the new springs from Moyer's are at the correct or original spec height. Old springs from an engine often are shorter because they are worn and squished down and tired. The spring shims sold for rebuilding an engine are meant to squish the spring a bit and restore the seating pressure of the valve. I remember that a .060" shim would increase by around 5 to 10lbs pressure for a tired Chev 350 v8.(is that correct Dave?) Those are much stronger springs than an A-4. We're working with less pressure here.
If you can see a significant difference between new and old springs it's probably time for new ones.

russ

[hcrisp]

Valve/tappet clearance

Is it correct to say that when #1 cylinder is TDC and the valve stem/tappet clearances are properly adjusted for that cylinder that the clearances for #4 valves/tappets will not be correct even though #4 cylinder is also TDC and its valves are closed?
If so, how do you know whether to work on #1 or #4 when the roll pin on the crank is vertical.
I'm confused. Maybe I'm thinking too much.
Howard

[hanleyclifford]

Is it correct to say that when #1 cylinder is TDC and the valve stem/tappet clearances are properly adjusted for that cylinder that the clearances for #4 valves/tappets will not be correct even though #4 cylinder is also TDC and its valves are closed?
If so, how do you know whether to work on #1 or #4 when the roll pin on the crank is vertical.
I'm confused. Maybe I'm thinking too much.
Howard

Howard - That is actually an excellent question. When #1 is at TDC, it's companion, #4 valves are not closed so that an adjustment could be checked. When checking clearances it's best to do it the old fashioned way: check each cylinder in firing order by carefully rotating the flywheel by hand.

[ndutton]

What you want Howard is to be sure the cam lobe for the valve to be adjusted is at it's lowest point. The place you're guaranteed that happens is TDC, the point where the piston is at it's highest on the compression stroke. The piston also reaches its zenith on the exhaust stroke but there the exhaust valve is at the end of being forced open by its cam lobe and the intake valve is just about to open as well.

How to tell TDC? There are a few ways but a vertical pin in the crankshaft by itself isn't one of them.

1. You can rotate the engine by hand observing the intake valve in the cylinder in question. After it closes the next time the piston reaches the top of the cylinder is TDC. The crankshaft pin can then be used to confirm.
2. You can rotate the engine by hand holding a finger over the spark plug hole for the cylinder in question. Once you feel positive pressure on your finger the next time the piston reaches the top of the cylinder is TDC. Again, the crankshaft pin can then be used to confirm.
3. Finally, if your engine runs prior to this exercise you can use the rotor in the distributor as an indicator of the compression stroke. When the rotor points to the plug wire for the cylinder in question you're there. Use the crankshaft pin to confirm.

Follow any of these methods for #1, from then on as you rotate the engine each time the pin is vertical you're at TDC in succession of the firing order.

[lat 64]

Is it correct to say that when #1 cylinder is TDC and the valve stem/tappet clearances are properly adjusted for that cylinder that the clearances for #4 valves/tappets will not be correct even though #4 cylinder is also TDC and its valves are closed?
If so, how do you know whether to work on #1 or #4 when the roll pin on the crank is vertical.
I'm confused. Maybe I'm thinking too much.
Howard

You are thinking properly.
When #1 is TDC on compression stroke, then #4 is TDC and at the end of it's exhaust stroke. The Ex valve will be just closing and still on the back of the cam lobe.
Since you are adjusting valves, you will have the cover off and you can watch as the tappets go about their business. You will see the #1 valves remain seated on the full compression stroke.

If tappets are not visible:
To figure out when #1 is coming up on compression strike, you can feel the compression come up with your finger on the open spark plug hole. Or, look at you can watch the rotor on the distributor(cap off) come to the position of #1 plug lead. This only works if it is certain the distributor is installed correctly. This will get you on the right cylinder so then you can Find TDC by watching the rolled pin on the crank.

If you have the engine on a bench, then do this a whole bunch to get comfortable with the way it goes.

R.

[lat 64]

good gravy! three of us answer at the same time. Too rich.

[hcrisp]

tappet adjustment

Thank you. I drove myself a little bit kookoo by adjust #1 and #4 at the same time and then #2 and #3 together since I was wrongly thinking, since both cylinders were up, those tappets would drop together.
I put a sign on my workbench - COMPRESSION stroke!
I also filed a mark on the accessory drive pulley.
Now the clearances repeat correctly after hand cranking a couple dozen times.
Howard

[hanleyclifford]

If you have filed a mark on your acc drive sheave (pulley) at #1 TDC and have a reference on the fixed casting, you have set yourself up to time with a strobe light with the engine running.