hey quick question on l16 cam timing

[mswit209]

im putting together my l 16 and i was wondering what each mark means i know they are for torque curves but which one is for low end and which one is for top end.

[Jesse C.]

The number 2 hole advances it 4 degrees and the number 3 takes you to eight degrees advanced. There is no provision to retard the cam with the sprocket.

 

Advancing the timing will produce some more power and in some cases give you more mileage, but, you also run the risk of detonation and can harm your engine in the process. Retarding it will make your mileage and performance suck. Retarding is usually done when crap gas is only available or at different altitudes.

 

Have fun!

[datsunaholic]

As Jessie said, each hole is 4° advanced from the next.

 

From the factory, L16s and L18s were set at #1. According to my Factory manuals, early L20Bs were also set to #1, but by 1978 the factory manuals stated they were set to #2 (this corresponds with the roundport smog heads).

 

#1 is really only ever used when the engine is factory fresh. Any timing chain stretch and a noticeable head milling will require running #2. On an L20B, the increased deck height means that #2 is almost always the right selection once he head has been skimmed in the least amount.

 

Just for info, each TOOTH of the cam gear is 9° from each other. I drove a truck for 6 years with the cam off by one tooth and set to #1... and it ran pretty darn good, because it gave it an overall advance of 5deg (if #2 had been zero).

[datzenmike]

You mean the 1, 2 or 3? They are for compensating for chain stretch or wear that would tend to effectively retard the cam from it's stock setting. When on TDC look through the top cam sprocket hole. On the cam thrust plate is a horizontal etch mark and just in front on the cam sprocket is a small V notch. The cam is perfectly timed in relation to the crank when the etch mark is directly above or just slightly to the left of the V. Depending on wear or stretch it could be any hole. This is the ideal position for all around performance/emissions/economy.

 

Now having said all that, a slightly retarded cam gives a late closing intake valve which is an advantage at ultra high RPMs. (of all the valve events early or late, intake or exhaust, a late closing intake has the most beneficent results) This is because at extreme RPMs there is also extreme intake velocity and even though the piston is well on it's way past BDC and rising upwards, the intake air keeps packing itself into the cylinder because of inertia. A late closing intake 'holds the door open' just a little longer to capture this effect. Tuned properly it's possible to pack more that atmospheric pressure.

 

This effect is quite small on a stock cam where all the other cam events may detract from the full effect. On a race cam these other openings and closings, lift and duration are optimized and work with the late intake closing and so the effect is much stronger.

 

Naturally a late closing intake will severly detract from low speed power as the piston will have or time to pump air back into the intake destroying intake vacuum.

 

Each hole the cam dowel is moved forward will advance the cam 4 degrees. I think the L16 is already on the #1 so you can't retard it any further. The 20B is factory set on the #2 so it could be moved back. In addition you could move the cam forward or back one tooth. Each tooth represents 9 degrees of cam timing..

[mklotz70]

Did a vid of this awhile ago....hope it helps :)

 

http://community.ratsun.net/topic/16542-reclocking-cam-sprocket/page__view__findpost__p__223758__fromsearch__1

[mswit209]

hey thanks for those vids that was helpful. does anyone know where i can get one of those timing chain wedges for this little project of mine. im used to taking everything apart since thats my job haha. even my own car when i did the hg on the dime i just went ahead and put in a new timing chain kit.

[datzenmike]

Piece of softwood 6 1/2" long by 1/2" thick tapering from 1 3/4" down to 1/1/4" will also work.

[mklotz70]

[banzai510(hainz)]

http://shop.oreillyauto.com/productdetail.aspx?MfrCode=PBI&MfrPartNumber=648831&CategoryCode=3491

 

see if this site works might have to add zipcode