Valve Timming quick reference Options

[-JR-]

I'm troubleshooting some blow back I'm getting on a new, never run, engine.

At Top Dead Center (ATDC)
Cylinder---Intake-----------------Exhaust
1-----------CLOSED----------------CLOSED
2
3
4

Options – OPEN / CLOSED / OPENING / CLOSING

Can anyone complete this chart for me? But I’m mostly interested in 3 and 4.

If someone knows it, can they tell me if the 1and 3 valve positions are the same as 2 and 4 when the crank is 180deg out from TDC?

Thanks!

-JR-
Soon to be driving his 914

[type47]

only help i can give is firing order 1-4-3-2 (if i recall correctly)

[-JR-]

Ha ha... Thanks, but I'm well past that.

But you are correct and it's stamped into the fan shroud on the 3/4 bank.

I think I am narrowing down my problem though...
The heads I had done at a very reputable shop in town and it seems that #3 intake valve is NOT seating and it's blowing the compressed air and fuel out the carb.

Going to put my compression tester hose into #3 during a compression stroke and prove it though.

[ArtechnikA]

QUOTE (-JR- @ Feb 28 2005, 10:18 PM)

...it seems that #3 intake valve is NOT seating and it's blowing the compressed air and fuel out the carb.

and yet you have lots of clearance on the rocker?

i only ask because it's pretty easy for the pushrod to come out of the lifter and cause valve seating issues.

but it could also be issues with the valve job; it happens... good luck!

[ClayPerrine]

Here is a simple (well, simple to me) way to do the valve adjustment.

Take a look at the camshaft on a 914. It only has 4 lobes for 4 cylinders. Each pair (1 and 3, 2 and 4) use the same cam lobe for intake and exhaust.

Picture of cam from factory manual....






So if you take both valve covers off and bump the motor over until the exhaust valve on #1 is wide open, you can adjust the exhaust valve on #3, because it is in the base circle of the cam.

I actually use a remote starter button on the starter to crank the engine over until the valve on the left side of the engine opens, then I adjust the right side valve. Then I go back and watch the right side valves and adjust the left side.


Hope that helps.

[joes]

There is a hole in the bottom of the transmission bell housing, there is a notch in the flywheel (not the front fan pully) that will line up in the hole in the bellhousing when the engine is 180. I do TDC on the top then turn the wheel (lock the other wheel with a jack under it) from underneath and line up the 180 mark. Repeat.

[Dave_Darling]

Crap, I wish I had time to do this up correctly...

Four stroke engine; intake-compression-power-exhaust.
On the intake stroke, the intake is open. On the compression stroke, both valves are closed. On the power stroke, both valves are closed. On the exhaust stroke, the exhaust valve is open.

"TDC" is TDC between the compression and power strokes. Both valves will be closed.

Firing order, as noted, is 1-4-3-2.
So at TDC#1:
#1 is between compression and power.
#4 is between intake and compression.
#3 is between exhaust and intake.
#2 is between power and exhaust.

#1 both valves are closed
#4 intake valve may be open; if so it is starting to close or will be soon.
#3 one or both valves may be open; exhaust is closing and intake is opening.
#2 exhaust valve may be open; if so it will be closing soon.

--DD