L21 "Long Rod" Tune-Up?

[LOOGLE]

Looking for help figuring out proper specs for a tune-up (timing and valve clearances on a "Jason Grey L21 Long Rod" as seen here http://: https://ratsun.net/topic/996-jason-grey-info/ 

 

Build as follows: 

 

- L20 bored to 89mm with shortened KA24 Pistons 

- A87 head with Isky race cam and springs (.530 lift)

- Weber DCOE 45's (if that matters)

 

I'd suspect stock valve clearances would not apply here. 

 

Currently have timing set @11 degrees BTDC and getting a slight knock and low idle (3-400rpms) on a cold start (I think it's an a/f adjustment on carbs but want to start with proper timing and valve adjustments first as I think that's the proper sequence of a tune-up.) 

 

Sny help is greatly appreciated!

 

[Stoffregen Motorsports]

Ok, for starters, 11 degrees should be ok, but what is more important is the total timing. What is the timing all-in? Shouldn't be more than about 32 degrees.

 

Second, .010"/.010" on the valve lash (at the tip of the rocker with the engine cold) is probably fine. You need to know the brand of the cam and the grind to know exact specs. But, the only time valve lash is crucial is if they are too tight and the valves hang open.

 

Who built the engine?

[iceman510]

Looks like 0.010 would apply to what you listed in the original post (if Z-196 is the grind).

 

 

Edited January 3 by iceman510

[Stoffregen Motorsports]

I forgot to ask - what distributor are you running? And has it been re-curved? I assume (hope) you're not running the vacuum advance.

[LOOGLE]

Z-196 is the grind! - Isky comp Cam. So that's .10 Intake and Exhaust? 

 

Datsun Spirit in Virginia built the motor but It was pretty much just an assembly job from an l20 with a blown head gasket. I'm the 3rd owner after the build with 5k miles on it.  As far as I know, it's never been professionally tuned, dyno etc. 

 

It's a mallory EI dizzy with msd coil and box. No Vaccum advance.  I know I need to replace the whole set-up but its not in the budget right now. A 123 bluetooth was suggested by the original owner which is around the same price as a refurb matchbox (but that's another thread). 

 

I'm fairly new to carbs and distributors but I know how to turn a wrench, do my homework to properly adjust things. I can set timing at idle but not sure how to set overall timing - yet..   Is that 32 at a certain rpm?  

 

Thanks for all the help so far! 

[Crashtd420]

38 minutes ago, LOOGLE said:

Z-196 is the grind! - Isky comp Cam. So that's .10 Intake and Exhaust? 

 

Datsun Spirit in Virginia built the motor but It was pretty much just an assembly job from an l20 with a blown head gasket. I'm the 3rd owner after the build with 5k miles on it.  As far as I know, it's never been professionally tuned, dyno etc. 

 

It's a mallory EI dizzy with msd coil and box. No Vaccum advance.  I know I need to replace the whole set-up but its not in the budget right now. A 123 bluetooth was suggested by the original owner which is around the same price as a refurb matchbox (but that's another thread). 

 

I'm fairly new to carbs and distributors but I know how to turn a wrench, do my homework to properly adjust things. I can set timing at idle but not sure how to set overall timing - yet..   Is that 32 at a certain rpm?  

 

Thanks for all the help so far! 

You can't really set the overall timing only verify it, well you can modify things but its not just simple turn of a screw.... usually about 2500 maybe 3000 rpm... when you Rev up the motor the timing advance should climb to around 32.... usually I see it as being 20 over what your base timing is.. in you case I'd expect to see 31....

 

And the 123 distributor is well worth it, excellent build quality and flawless function... only issue I ever had was the Bluetooth doesn't like the extreme cold.... 

 

Another thing to think about vs paying to have it tuned is to add an air fuel gauge.... helps out a lot for tuning...

[Stoffregen Motorsports]

Not .10"

 

.010"

 

You'll need a skinny feeler gauge to fit in the lash pad under the tip of the rocker.

[Stoffregen Motorsports]

I would stick with the Mallory. No modern electronics to go bad. You can also convert the Mallory to use a magnetic pickup and run with your 6AL box. I have one right now that I'm modifying by installing an MSD trigger wheel and magnetic pickup inside the distributor. It will be indestructible.

 

The only thing I don't like about the Mallory distributor is the advance mechanism. It's held tight with screws, and if those screws become loose, the advance curve becomes out of adjustment. Loctite on those screws will keep it solid.

[iceman510]

Are we talking Mallory points or Unilite distributor?  I have the Unilite mechanical with MSD 6AL on my B- sedan car.  Been solid so far. I will have to check on the advance mechanism as you mention Matt. 

 

I bought spare cap and rotor last fall since not sure Holley will keep supplying the Mallory parts forever as they are phasing them out in favor of MSD brand.  What are the part numbers for the MSD parts you are using to modify yours Matt, and is it a points distributor originally?  That would be a good backup plan in case the Mallory module becomes unobtainium. 

[datzenmike]

Stock valves and rockers are going to expand the same no matter the cam, so what the FSM recommends. 0.010" intake and 0.012" for the exhaust on a HOT engine. The manual shows it being set on the cam lobe. A 0.010" cold setting on the rocker tip will expand from the heat when the engine warms. This cold setting is likely quieter than the hot setting on the lobe.  

 

 

 

 

 

 

[Stoffregen Motorsports]

7 hours ago, datzenmike said:

Stock valves and rockers are going to expand the same no matter the cam, so what the FSM recommends. 0.010" intake and 0.012" for the exhaust on a HOT engine. The manual shows it being set on the cam lobe. A 0.010" cold setting on the rocker tip will expand from the heat when the engine warms. This cold setting is likely quieter than the hot setting on the lobe.  

 

 

 

 

 

 

I get your logic Mike, but when a custom cam grinder specs a valve lash, it's almost always cold, and at the rocker, not at the cam (as the FSM shows).

[Stoffregen Motorsports]

8 hours ago, iceman510 said:

Are we talking Mallory points or Unilite distributor?  I have the Unilite mechanical with MSD 6AL on my B- sedan car.  Been solid so far. I will have to check on the advance mechanism as you mention Matt. 

 

I bought spare cap and rotor last fall since not sure Holley will keep supplying the Mallory parts forever as they are phasing them out in favor of MSD brand.  What are the part numbers for the MSD parts you are using to modify yours Matt, and is it a points distributor originally?  That would be a good backup plan in case the Mallory module becomes unobtainium. 

I believe both points and Unilite Mallory distributors use the same advance mechanism.

[datzenmike]

I always find the FSM method still kind of noisy.

[LOOGLE]

Sorry guys getting a little confused here. 

 

This is an a87 head with an isky comp cam and springs, no where near a factory head. I would assume to go with what Isky's recommendations and not the fsm? 

 

...and - those settings are .010 for both intake and exhaust under the rocker, cold?  I'll be doing it cold as I'm no where quick enough to do it hot yet. 

 

I'm working off this thread/video: https://ratsun.net/topic/16539-l-series-valve-adjustment/

 

 

Side note: It's a unilite. I had a really hard time finding replacement rotors for it - like, there are no more. I bought a mallory marine cap with the same dims and specs but have yet to try it. Also, previous owner said he put different advance springs in it to make it more streetable which it seems to be.  

[Stoffregen Motorsports]

Yes, .010" intake and exhaust. Cold, under the rocker.

 

Do you have a feeler gauge that will fit inside the lash pad? If not, you can cut a wide one with a tin snips, but then you need to smooth the edges of the cut so it doesn't screw up the measurement.

 

Here's a narrow feeler gauge set - https://shop.advanceautoparts.com/p/lisle-mini-blade-type-010-to-035-feeler-gauge-68000/22984247-P?c3ch=PLA&c3nid=22984247-P&srsltid=AfmBOoq6C1bqs6U2_wiy0Xe12sGbq_0tszYdPTWjC1yHwulFFeo17NDNodU

[LOOGLE]

Yeah,  I have pretty much the same set. 

 

Thanks for clarifying! Couldn't own a datsun without ratsun! 

[iceman510]

What's your distributor assembly part number?  I have the 4558901 which is the Unilite with no vacuum advance.  I bought caps and rotors direct from Holley (they own everything now...).  

 

I believe this is the rotor I bought.  I will get out to the race trailer this weekend and check the cap and rotor part numbers I have.  I can't find the cap p/n on the site right now.

 

https://www.holley.com/products/ignition/distributors/distributor_accessories/distributor_caps_and_rotors/parts/340

[iceman510]

 

From an old Mallory catalog:

 

 

 

Added tune up parts info.  Found the 271 cap.  Looks like it is discontinued.  Glad I bought some.

 

 

https://www.holley.com/products/discontinued_product/parts/271MAL

 

 

 

 

Edited January 5 by iceman510

[LOOGLE]

Yep that's the same rotor I used although I had to shave the plastic on the bottom of the rotor down a little so it would fit correctly under the cap. Maybe something to do with the different advance springs? 

 

old rotor vs. new one that still needs to be shaved down:

 

 

271b is the marine cap I bought but havent put it on yet. I think the only difference is it's black. 

 

It's a 45 series from what I remember. no vacuum advance.  

 

 

 

[LOOGLE]

Maybe an obvious answer here so my apologies. 

 

With the valve closed (cam lobe @ 10 & 2ish) I'm way way higher than .010 under the rocker (above lash pad) BUT about .010 under the cam lobe.  

 

With a valve open I'm closer to .010 under the rocker (above lash pad) Obviously no gap under rocker/cam. 

 

Should I be taking reading under rocker with valve open or closed? 

 

(smaller feelers coming this week)

 

http://

[datzenmike]

The rocker arm ratio is 1.5 :1 so whatever you read at the cam it will be 50% wider at the valve tip. Theoretically a 0.010" at the cam will be 0.015" at the valve tip

 

Valve most certainly must be closed and not on the lobe when measuring and the rocker pad or the tip. Valve clearance is critical to give the valve the most time closed where is physically conducts heat by contact with the valve seat.

 

That cam has obviously been reground down a lot.

[banzai510(hainz)]

what Mklotz has on the vid is good enough i say

[LOOGLE]

Got the mini feelers and cleared up my confusion (thanks @Stoffregen Motorsports) and of course theres no clearance on the rocker with the valve open - duh. 

 

Measured all lobes and multiplied by 1.5 to get ~ .530 or so of lift (wanted to make sure no one pulled a switcheroo in between owners). Must have been sent to isky for a regrind. "Japan u20 19 M" is stamped on the shaft. 

 

Under cam clearance:  .008/9 across the board

Under Rocker clearance: .013/14 

Pretty much clarifying @datzenmike 1.5:1 rocker arm ratio 

 

Does adjusting lash .003 (.013-.010) across the board seem excessive?   

[Stoffregen Motorsports]

Yeah, that's a massive cam. On a custom cam, usually the numbers are scribed into the back of the cam.

[datzenmike]

It will be less than 0.530" because of the rocker clearance but still......