U67 Cylinder Head Valves

[datzenmike]

When the throttle plate is wide open there is virtually NO vacuum advance signal. It has no impact on full out performance. For example the vacuum advance canister on the  L16 in the '73 620 does not even begin to move the timing until over 5.9 in. of mercury. Easy enough to put a vacuum gauge on the vacuum advance hose and go for a drive and floor it under load to see there is none.   

[JumboFett]

9 hours ago, Stoffregen Motorsports said:

SImply disconnecting the vacuum line will make it rely purely on centrifugal advance. But there are ways to adjust the throw of the weights and the rate at which they advance. It's called re-curving a distributor.

 

I don't think there are any instructions, as it used to be done with factory Nissan parts, which are no longer available. Now you need to weld up the slots and grind them to fit. Then remove one of the springs and adjust the tension on the remaining spring by bending the tab that holds it.

¡Ay Carumba!

Do we at least know what the total mechanical advance is if starting at 12°adv? I’d love to get to 32°.

 

Also, it just continues to baffle my mind that someone hasn’t connected the market on manufacturing high quality aftermarket datsun parts. We all seem to be living off scraps from the past! 

[JumboFett]

9 hours ago, Stoffregen Motorsports said:

 

Edited December 23, 2022 by JumboFett

[datzenmike]

What distributor are we talking about here???? '74??? L18?? The L18 in the '74 620 mechanical advance starts at 850 and maxes out at 2,000 and total mechanical is 11 @ distributor and 22 @ crankshaft. Plus the initial or static this adds to 34 degrees. There is no rule for total advance on any engine, some like more some less. 34 is in the ballpark for an L series.

 

edit: 12 is L20B timing. L18 is 5 distributor or 10 crankshaft + 22 mechanical for 32?

 

There is no market for Datsun parts. No demand volume to make it worthwhile. This is why I always say to never throw old pars away. Just ask Mklotz70. It's all R&D and investing your own money to run a batch that only partly sells. Do you know the story of how copper wire was invented??? Two Datsun owners were fighting over a penny. That's how cheap they are.

[Crashtd420]

8 hours ago, JumboFett said:

¡Ay Carumba!

Do we at least know what the total mechanical advance is if starting at 12°adv? I’d love to get to 32°.

 

Also, it just continues to baffle my mind that someone hasn’t connected the market on manufacturing high quality aftermarket datsun parts. We all seem to be living off scraps from the past! 

It depends on what you are looking for, some stuff is out there but they are expensive....

Are you looking for a better distributor?

If so have a look at the 123 ignition distributor... again not cheap but an extremely well built unit.... 

Programmable timing curve,  I only use the mechanical advance because I am using a side draft carburetor...  

https://123ignitionusa.com/new-category-1/

 

Been using mine for 5 years now,  only thing I recommend is get an extra rotor or 2.... I couldn't find a proper replacement other than the one they sell.... the cap i tracked back to a BMW part which you can get it at the dealer or a parts store.... 

 

[Stoffregen Motorsports]

4 hours ago, Crashtd420 said:

It depends on what you are looking for, some stuff is out there but they are expensive....

Are you looking for a better distributor?

If so have a look at the 123 ignition distributor... again not cheap but an extremely well built unit.... 

Programmable timing curve,  I only use the mechanical advance because I am using a side draft carburetor...  

https://123ignitionusa.com/new-category-1/

 

Been using mine for 5 years now,  only thing I recommend is get an extra rotor or 2.... I couldn't find a proper replacement other than the one they sell.... the cap i tracked back to a BMW part which you can get it at the dealer or a parts store.... 

 

I'm happy you're happy with your bluetooth ignition. I tend to avoid adding electronics to old vehicles and I have my reasons, not all of which are related to performance. Mostly, I just like to keep things simple.

 

But...if someone I trust has had success with the part in question, I'm all ears. I trust you Neil.

 

I just checked out their website and the cap and rotor look like older Bosch stuff. I bet the rotors are VW.

 

Yep - https://vwparts.aircooled.net/Bosch-04-008-Ignition-Rotor-Fits-010-and-019-Dist-p/04-008.htm

[Crashtd420]

1 hour ago, Stoffregen Motorsports said:

I'm happy you're happy with your bluetooth ignition. I tend to avoid adding electronics to old vehicles and I have my reasons, not all of which are related to performance. Mostly, I just like to keep things simple.

 

But...if someone I trust has had success with the part in question, I'm all ears. I trust you Neil.

 

I just checked out their website and the cap and rotor look like older Bosch stuff. I bet the rotors are VW.

 

Yep - https://vwparts.aircooled.net/Bosch-04-008-Ignition-Rotor-Fits-010-and-019-Dist-p/04-008.htm

They do have the USB one, set it and forget it... the only reason I got the bluetooth one is the ability to lock it with the app.... becomes a really good anti theft device....

 

As far as the rotor I'm not sure... I found a couple that looked like that but were not correct..... they just didn't seat properly.... hard to explain.... 

I could cross check the cap, it was the brand beru?

But the rotor I could not.. even finding the exact brand rotor .. only 123 ignition came up selling it....

[JumboFett]

On 12/22/2022 at 8:31 PM, datzenmike said:

What distributor are we talking about here???? '74??? L18?? The L18 in the '74 620 mechanical advance starts at 850 and maxes out at 2,000 and total mechanical is 11 @ distributor and 22 @ crankshaft. Plus the initial or static this adds to 34 degrees. There is no rule for total advance on any engine, some like more some less. 34 is in the ballpark for an L series.

 

edit: 12 is L20B timing. L18 is 5 distributor or 10 crankshaft + 22 mechanical for 32?

 

There is no market for Datsun parts. No demand volume to make it worthwhile. This is why I always say to never throw old pars away. Just ask Mklotz70. It's all R&D and investing your own money to run a batch that only partly sells. Do you know the story of how copper wire was invented??? Two Datsun owners were fighting over a penny. That's how cheap they are.

Honestly, I have kind of a Frankenstein. The truck is a ‘74, but it has an L20B supposedly out of a ‘76 and and front suspension with disk brakes and ball joints, indicating that it might be a ‘78. The exhaust manifold was definitely not laden with smog crap, so I’m thinking that’s a ‘74 part, and the distributor used points so that was probably out of the ‘74 as well (my guess is if they had a matchbox they didn’t want to figure out how to wire it up). I’m not certain how to tell the difference though, I’ve learned a lot since jumping back into the Datsun world but I still have much more to learn.

[JumboFett]

16 hours ago, Crashtd420 said:

It depends on what you are looking for, some stuff is out there but they are expensive....

Are you looking for a better distributor?

If so have a look at the 123 ignition distributor... again not cheap but an extremely well built unit.... 

Programmable timing curve,  I only use the mechanical advance because I am using a side draft carburetor...  

https://123ignitionusa.com/new-category-1/

 

Been using mine for 5 years now,  only thing I recommend is get an extra rotor or 2.... I couldn't find a proper replacement other than the one they sell.... the cap i tracked back to a BMW part which you can get it at the dealer or a parts store.... 

 

🤤

Oh baby! That thing’s making me breathe heavy! Full control of timing via Bluetooth, as well as a lockout feature?!

 

And you have personal experience with its durability?!

[datzenmike]

All L20Bs through '77 were points so could be anything. If it has a U67 head then a '75-'77 L20B.

[JumboFett]

3 hours ago, datzenmike said:

All L20Bs through '77 were points so could be anything. If it has a U67 head then a '75-'77 L20B.

Are there serial numbers on the side of the distributor that might indicate model year?

[datzenmike]

If the numbers agree with what you know for sure about the engine year, this only confirms. If it doesn't agree, after close to 50 years, it simply could have been swapped.

[distributorguy]

If you look under the points plate, there will be a number stamped in the piece that has 2 slots for the weights like "11".  This is 11 distribtor degrees, doubled at the crank via the timing chain set.  Earlier ones were 13.5 but it could be anything.  

[Stoffregen Motorsports]

Holy crap. Where have you been?

 

I've been thinking about you lately. We're heading to Sears Point for our first race in the MG this week and was wondering what you've been up to.

1 hour ago, distributorguy said:

If you look under the points plate, there will be a number stamped in the piece that has 2 slots for the weights like "11".  This is 11 distribtor degrees, doubled at the crank via the timing chain set.  Earlier ones were 13.5 but it could be anything.