HELP - l20b timing - cam dowel on bottom?

[rjgilligan]

I'm replacing the head gasket and am putting the new beck/arnley sprockets on. The block is set to TDC, but my dowel is/was on the bottom, not the top.  After watching this Hainz video, he mentions that the dowel should be on the top. Should I rotate the cam 180 degrees so I can line up the chain correctly, or is this they way they are on the l20b? Did I pull the head with it not on compression stroke? Let me know if you need pics..

[Eagle_Adam]

little confused by the way you worded it but if i understand properly heres your answer

 

the bottom sprocket has a groove in it to line up with the keyway on the crank itself, the cam sprocket needs to line up with the Dowel(that can fall out) on the cam istelf.

 

The chain should have 2 bright links on in. One goes on the "dot" on the crack sprocket, the other lines up with the cam gear 

[Eagle_Adam]

oh, after re-reading it i see what you were after, ignore my previous post.

 

Look at the cam, the lobes for the first cylinder should be at a "Y" 

[rjgilligan]

Hey Eagle_Adam,

Yea that was a bit confusing.., I meant the dowel on the upper cam sprocket that you use when choosing 1,2, or 3rd position for the sprocket. That is not on the top of the sprocket shaft, but on the bottom. The lobes of the 4th cylinder are in a Y, and the first cylinder are in an upside down Y.  I guess I should rotate it?

[DanielC]

The crankshaft turns twice as fast as the camshaft.  Two cylinders on the engine are at Top Dead Center (TDC) at the same time, #1, and #4.  When you took the engine apart, it was at TDC, firing stroke #4.  No big deal.

 

When you put the head back on the engine, turn the camshaft 180 degrees to put the camshaft back in the proper position for reassembly. 

 

You did block the cam chain before you removed the cylinder head, I hope.  You cannot turn the crankshaft with the cam chain blocked.

[rjgilligan]

Thanks for the info! I just wanted to be certain that was all there was to it. I'm replacing the old chain as well, so I already have the timing cover off. I'm able to move both shafts independently right now.  

It seems like it would be a good idea would be to take the bottom off TDC a little bit so I don't bang any valves on the top of the pistons when rotating the cam.

[Eagle_Adam]

 

When you put the head back on the engine, turn the camshaft 180 degrees to put the camshaft back in the proper position for reassembly. 

 

correct

 

 

 

 

 

 You cannot turn the crankshaft with the cam chain blocked.

 

Wrong :P Ive done it several times 

 

 

using this

 

[Eagle_Adam]

[datzenmike]

I would turn the cam first before installing the head. You're at TDC and rotating the cam will bring #1 and #4 valves to max lift. You will kiss the piston tops and bend a valve.

[datsunaholic]

Also, your distributor drive is also now at #4, instead of #1.  So if you rotate ONLY the cam before installing the sprocket, you'll have to rearrange your spark plug wires to match.  Now, if you pulled the timing cover too (since you mentioned replacing the sprockets), you'll have to reinstall the drive spindle so you'll be OK, set cam with dowel on top (turn cam BEFORE installing head on block), install spindle properly, should be OK.

[banzai510(hainz)]

set block to TDC or the first piston on top.

put the cam/head on with the dowel in the 12o clock postion right now. this should be close enought to do fine adjustment .

 

PS its hard to get the head to TDC or dowel up if it was removed in another position. so what you can do  is if you have the front cober off already is rotate the crank so the istons are in the middle. put head on using the 2 center head bolts and rotate the cam to TDC as in my vid.

 

then put the crank piston on top. and install head. install cahin ect.

 

if L20 youl pick #2 on sprocket

[rjgilligan]

Thanks, this was all a lotta help and I got everything lined up correctly.

Except.... I read Hainz last post too late, set the sprocket to #1, and the crank pulley reads 15 degrees advanced instead of 0 when the noch lines up with the v.

 

Yea, I put the timing cover on already. 

Is it possible (after wedging that chain really well this time) to pull the top sprocket and rotate it? The chain is tight... seems like it would be difficult to get the sprocket back up on the cam shaft.  Has anybody succeeded in this, or am I shitouttaluck?

[Eagle_Adam]

Is it a new chain?

[rjgilligan]

Is it a new chain?

 

Yea, it's new.

[Eagle_Adam]

i was under the impression that the numbers were used in reference to chain stretch, as is new chain is set to one, and unknown chains are set to 2 or 3 depending on what fits bets. I think your ok man. 

[datsunaholic]

The numbers (dowel holes) are to account for chain stretch and/or head milling.  However L20Bs were set at #2 from the factory.  However the factory manual I have, it wasn't noted until the 1976 manuals (1974 L20B manuals use the same wording from the L16/L18 manual, showing #1).  It'll RUN both ways, just not optimally (depending on other factors, of course).

[rjgilligan]

Hmm, now I'm wondering if I should just run it like this. Engine is off 15* BTDC on #1 with all new timing parts. I know I didn't put the chain on wrong. Does that mean #2 is 0 TDC and #3 is 15* after TDC? Or is it dependent on the manufacturer as well? 

My worry is that if I rip off this sprocket to turn it, I'll end up with #2 and #3 advancing it BTDC more and more instead, leaving me scratching my head wondering

 

Looks like this when I line up the v-notch

Looks like this when I line up the crank

[rjgilligan]

Is this okay to run like this, with a 15* cam advance? It's advanced and set to #1 cam hole, which means I can't get it back any more. Does anyone know why this wouldn't line up with all new parts? 

[datzenmike]

It might run but this is not where it's supposed to. Severe power loss and possible burnt valves.

Set to TDC on the crank. Get it to this...

 

Your cam in this picture is about 6-8 degrees (cam) advanced. Twice that on the crank. If you are on the #3 hole go back to #2 hole... if on #2 go back to #1 that will remove 4 degrees.

 

If you are on #1 hole move sprocket counter clockwise back one tooth. This will remove 9 degrees. Check the timing and if needed move from #1 to #2 hole to correct.

[rjgilligan]

Alright, thanks a King Rat.  I'm on #1, so I'll move it back a tooth and recheck.. 

Sure is a bit frustrating that the teeth count between the sprocket marks, gold chain links, and dots were all correct but it's still off a tooth.

[rjgilligan]

Alright, thanks a King Rat.

 

I mean.. .Mike.

[datzenmike]

Agreed. All that matters is that the cam sprocket and the mark line up no matter how many teeth between cam and crank.

 

Be sure that you set TDC in a clockwise direction only. If you overshoot, back well up before and try again. If you don't you will get chain slack on the tension (driver's side) Accurately setting TDC is the key.

 

Don't for get to block the chain tensioner!

[rjgilligan]

 

Don't for get to block the chain tensioner!

 

I won't make that mistake again!