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Identifying “Peanut” Heads for L Series


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There appears to be no universally accepted way to distinguish between them. So I’ll tell you what I’ve come up with and feel free to correct me.  I’m gathering this information for building about a 115 hp L20b in a 74’ 620.  Currently I have a U67 head off an L18.  


Step 1

I sat down with my trusty copy of How To Modify Your Nissan & Datsun OHC Engine by Frank Honsowetz, pg 42 states:

 

”For 2000cc-or-larger-displacement L-series engines, use a standard L20B head, part number 11041-U6702.  This head is identical to the SSS head except it has a larger chamber volume-45.2cc versus 40cc.  This larger chamber is more compatible with the swept volume of the larger-displacement engines.” 
 

Looking up that part number I’m inclined to believe it implies a version of the U67 head.  I’d also read elsewhere that the “peanut heads’ (closed chamber) were the best ones for a mild street build.  A set of heads such as the 219 SSS 510 heads. I kept going down the rabbit hole...


Step 2

I used the search feature... stumbled on some old threads that lead me to this article Julian Serles covers things in much greater detail with pictures than I will here. 
 

“The U67 casting is marked in the typical L-series head location.  The U67 head was used on L20Bs in differing applications up to about 1976.  U67s have 35mm (1.375”) intake ports and square exhaust ports.  Intake valves are 42mm (1.65”) while exhaust valves are the familiar 35mm (1.38”).  The U67 head is an open-chamber design.  The open-chamber heads have combustion chambers of approximately 45.3cc.  These are typically the head of choice for L20B and larger engine builds due to the larger combustion chamber compared to closed A87 heads.“

 

http://dimequarterly.blogspot.com/2012/02/tech-how-to-l-series-cylinder-head.html

 

Serles goes on to discuss the rarer U60, 219, and V912 heads. There could be a V912 out there that was special ordered which would suit my needs but I’d probably die before I find one. 
 

Further there appears to have been an OS Giken aftermarket head made... but let’s keep this simple.  
 

Step 3

Ask for clarification.  It appears I need an open chamber, U67, with cooing ports, mated to an L18 exhaust manifold with some quality side drafts. Annnnd... probably cams.

 

What do you think?

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The big problem is that in the 80s it was cheaper to buy the head off of a Japanese import engine than to do a valve job or find one just to replace a damaged one. Often the entire engine was swapped in.This introduced closed chamber heads and odd ball number heads where there were none before. As emissions were becoming very restrictive and lower compressions were the order of the day I doubt very much Nissan randomly slipped closed chamber heads and 9 to 1 compression on some engines and not on others.

 

It's my experience that all L16s came with a 210 number head only as it has the smallest combustion chambers ports and valves and 8.58 compression. The only other 'number' head is the larger closed chamber 219* head used on the L16SSS and L18SSS but only in conjunction with flattop pistons to keep the compression up and reasonable. Open chamber heads would drop the compression into the 7s. 

 

L18s never came with U67 heads though someone could very well have put one on. Usually an open chamber A87 'letter' head was used and 8.4 compression. A87 heads were on the '74 620 and 710 and the '73 610. The A87 was also on the first ever used L20B on the '74 610 then switched to the U67 for '75. A87 heads have slightly smaller ports and some have a smaller exhaust valve than the U67/W58 heads.

 

L20Bs use the open chamber U67 from '75 through '77 then all L20Bs use the W58 from '78 through '80. The U67 does not have the two holes for the matching coolant cooled/heated intakes though you can easily drill them out. The W58 and all other 'number' and 'letter' heads have the coolant holes. The W58 like the U67 has 1.375" intake ports and unique round exit exhaust ports an steel liners intended to glow red hot and help burn away emissions. They can be removed easily enough with the valves out making the W58 head comparable to the U67.

 

 

219* heads were available for competition use and all sold and used up so because of demand, Nissan later re-issued them as the 912 head. Both of hese had the largest of all intake ports 1.5" than any letter or number head.

 

 

There are exceptions to every rule. A different letter head may have been substituted for a U67 but it would have been the same open combustion chamber to prevent altering the compression ratio. In upwards or 50 years many heads could have been swapped but generally this is what I believe was produced and sold in North America in the '70s.

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It’s good to see I was on the right track.  I really did try to “use the search” but there’s conflicting information from credible sources.  I’ll just take my time and attempt to source a U67 that I can rebuild and an L20b.

 

While it would be cool to have the 219/912 head, the calculations I’ve seen on the compression indicate this is less than optimal.  My notes say that would give me a compression ratio of 8.903. Unfortunately I don’t remember where that number came from.  
 

Although @flatcat19 is saying I should start with scrapping the L20b in favor of Z20S. That’s without stepping into the Jason Grey info on Frankenstein engines.

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8 minutes ago, Stoffregen Motorsports said:

Z20E had the long rods. Did the Z20S? I didn't think so.

Yes the Z20S has the long rods also. 

 

Soundline - If your looking for a Z20S block with caps/bolts, got one in storage for sale. PM me, located in Clarkston Wa.  No rods / pistons or crank, sold them. 

Edited by 420n620
cause it's an option, lol
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3 hours ago, datzenmike said:

It's my experience that all L16s came with a 210 number head only as it has the smallest combustion chambers ports and valves and 8.58 compression. The only other 'number' head is the larger closed chamber 219* head used on the L16SSS and L18SSS but only in conjunction with flattop pistons to keep the compression up and reasonable. Open chamber heads would drop the compression into the 7s. 

 

For what it's worth, there are also two different 210 heads, one open chamber, one closed chamber. Both were used on USDM engines.

 

Same with A87 heads, although closed chamber A87 heads are not USDM. But plenty of them made it over here from importers as you said. 

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1 hour ago, 420n620 said:

Yes the Z20S has the long rods also. 

 

Soundline - If your looking for a Z20S block with caps/bolts, got one in storage for sale. PM me, located in Clarkston Wa.  No rods / pistons or crank, sold them. 


PM sent. Thanks!

 

40 minutes ago, datsunfreak said:

 

For what it's worth, there are also two different 210 heads, one open chamber, one closed chamber. Both were used on USDM engines.

 

Same with A87 heads, although closed chamber A87 heads are not USDM. But plenty of them made it over here from importers as you said. 


Nooooo.... so, what I’m getting out of this is: take them off, flip them over, and look. Only way to be sure. 

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9 minutes ago, Soundline said:

so, what I’m getting out of this is: take them off, flip them over, and look. Only way to be sure. 

 

Yeah, basically. I've never seen or even heard of a W58 closed, or a U67 closed. A87 comes both ways, as does 210 and W53. 

 

And to add another level, the closed chamber 210 is not the same as the others. The chamber is sort of oval shaped, not heart shaped. They are really only useful if you want maximum torque from an L13/L14/L16. 

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A closed chamber A87 is a good head for an L20b, and is usually the easiest one to find. Smaller ports/valves than a U67 for more torque, and a "free" compression bump with stock pistons. 

 

Can you get 93 octane there? 

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7 minutes ago, datsunfreak said:

 

Yeah, basically. I've never seen or even heard of a W58 closed, or a U67 closed. A87 comes both ways, as does 210 and W53. 

 

And to add another level, the closed chamber 210 is not the same as the others. The chamber is sort of oval shaped, not heart shaped. They are really only useful if you want maximum torque from an L13/L14/L16. 


Ok, so basically I need to tattoo how they should look in my mind and go off memory to find the right head. Sounds like I should skip the 210 heads then.

 

4 minutes ago, datsunfreak said:

A closed chamber A87 is a good head for an L20b, and is usually the easiest one to find. Smaller ports/valves than a U67 for more torque, and a "free" compression bump with stock pistons. 

 

Can you get 93 octane there? 


Cool, so the A87 closed chamber works despite Honsowetz?  I know that Jason Grey made some claims about Honsowetz focusing too much on the 6 cylinders and having some errors with the 4 cylinder engines.

 

and.. tragically... no.  The People’s Communist Republic of Washington doesn’t give us good gasoline.

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27 minutes ago, Soundline said:


Ok, so basically I need to tattoo how they should look in my mind and go off memory to find the right head. Sounds like I should skip the 210 heads then.

 


Cool, so the A87 closed chamber works despite Honsowetz?  I know that Jason Grey made some claims about Honsowetz focusing too much on the 6 cylinders and having some errors with the 4 cylinder engines.

 

and.. tragically... no.  The People’s Communist Republic of Washington doesn’t give us good gasoline.

 

I'm running a closed chamber a87 on an L20b. Works great, but didn't notice any difference in performance.

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54 minutes ago, datsunfreak said:

 

Yeah, basically. I've never seen or even heard of a W58 closed, or a U67 closed. A87 comes both ways, as does 210 and W53. 

 

And to add another level, the closed chamber 210 is not the same as the others. The chamber is sort of oval shaped, not heart shaped. They are really only useful if you want maximum torque from an L13/L14/L16. 

 

A2932D04-3AA9-464A-9652-B0DACE0393A1.jpeg

3E82D137-3A38-4110-A92E-0E1B1DEB318D.jpeg

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5 hours ago, Soundline said:

It’s good to see I was on the right track.  I really did try to “use the search” but there’s conflicting information from credible sources.  I’ll just take my time and attempt to source a U67 that I can rebuild and an L20b.

 

While it would be cool to have the 219/912 head, the calculations I’ve seen on the compression indicate this is less than optimal.  My notes say that would give me a compression ratio of 8.903. Unfortunately I don’t remember where that number came from.  
 

Although @flatcat19 is saying I should start with scrapping the L20b in favor of Z20S. That’s without stepping into the Jason Grey info on Frankenstein engines.

 

Probably got it from me, 8.903 is what I have written down.

 

What Keith means is the Z20 rods and pistons as the Z20 and L20B blocks and crankshafts are (basically) the same. 

 

 

3 hours ago, Stoffregen Motorsports said:

Z20E had the long rods. Did the Z20S? I didn't think so.

 

All Z20 engines had the long 6" or 152.5mm rods and flattop pistons. Z20 engines use the L20B crankshafts.

 

 

2 hours ago, datsunfreak said:

 

For what it's worth, there are also two different 210 heads, one open chamber, one closed chamber. Both were used on USDM engines.

 

Same with A87 heads, although closed chamber A87 heads are not USDM. But plenty of them made it over here from importers as you said. 

 

 

I'm aware of the 210 closed chamber but I don't think it was sent here on any engines. Again probably on an import engine. My info shows a succession of L16 head part numbers and all later numbers refer back to a former part number. Usually if there is a radical departure they do not because there isn't any similarity to a previous head. If you can get the closed chamber 210 head part number I can compare it and update this and my own info. 

 

Unlike the A87 closed which are not exactly common they are out there. The closed chamber 210 head is never talked about. I think it was something Japanese for giving the L16 a slight edge racing but keeping the stock 210 number. Maybe Nissan made them available over the counter just like they did with the 912 head.

 

 

 

1 hour ago, datsunfreak said:

 

Yeah, basically. I've never seen or even heard of a W58 closed, or a U67 closed. A87 comes both ways, as does 210 and W53. 

 

And to add another level, the closed chamber 210 is not the same as the others. The chamber is sort of oval shaped, not heart shaped. They are really only useful if you want maximum torque from an L13/L14/L16. 

 

 

I had a closed chamber W58. Junk yard tag said 200sx on it.

 

Only picture I have of the 210 closed chamber is this one...

 

x8WHzyU.jpg

 

tjSOOEe.jpg

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What... is... that abomination...

 

Ive definitely learned something in this thread.  Everything you think you know about L-series heads is wrong.

 

Thanks for ruining my day Draker... 😥😢😭

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40 minutes ago, Draker said:

 

I'm running a closed chamber a87 on an L20b. Works great, but didn't notice any difference in performance.

 

Popular wisdom has it that for every point of compression increase you gain 4-6% efficiency increase. Assuming you run a higher octane gas and run the ignition as advanced as is safe. Going from 8.4 to 8.9 is barely 1/2 of 4-6%. On a stock L20B that (on a really good day) makes 93 hp that an increase of 2.75 hp at what ever the maximum HP rev is. You would notice  it more on a heavily modified  engine.

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1 hour ago, Soundline said:

Cool, so the A87 closed chamber works despite Honsowetz?  I know that Jason Grey made some claims about Honsowetz focusing too much on the 6 cylinders and having some errors with the 4 cylinder engines.

 

Yes, that. A lot of what's in that book is based on what BRE/John Caldwell was doing, and they stuck to the 219 and FIA heads. 

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3 minutes ago, datzenmike said:

 

Probably got it from me, 8.903 is what I have written down.

 

What Keith means is the Z20 rods and pistons as the Z20 and L20B blocks and crankshafts are the same. 

 

All Z20 engines had the long 6" or 152.5mm rods and flattop pistons. Z20 engines use the L20B crankshafts.

 

Unlike the A87 closed which are not exactly common they are out there. The closed chamber 210 head is never talked about. I think it was something Japanese for giving the L16 a slight edge racing but keeping the stock 210 number. Maybe Nissan made them available over the counter just like they did with the 912 head.

 

I had a closed chamber W58. Junk yard tag said 200sx on it.

 

Only picture I have of the 210 closed chamber is this one...

Not to point out the obvious... but I think you’re in all the tech threads after 2012 or so.

 

Interesting, it’s nice to see my individual research was wrong, and right... basically it comes down to a “all bulldogs are dogs, but not all dogs are bulldogs”.

 

Do we have good solid pictures I can use for reference when sourcing a head?

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For what it's worth a closed or peanut head is not just a compression bump. There's more to it than that.  Anywhere outside that 'heart shaped' combustion chamber is separated from the piston top by only the thickness of the head gasket. As the piston approaches TDC the air caught in this 'pinch' or quench area is violently pushed out into the open part of the combustion chamber promoting beneficial turbulence that homogenizes the gas and air mixture reducing hot spots. Naturally a flattop piston is ideal but even a dished piston will gain some from this.    

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6 minutes ago, datzenmike said:

 

Popular wisdom has it that for every point of compression increase you gain 4-6% efficiency increase. Assuming you run a higher octane gas and run the ignition as advanced as is safe. Going from 8.4 to 8.9 is barely 1/2 of 4-6%. On a stock L20B that (on a really good day) makes 93 hp that an increase of 2.75 hp at what ever the maximum HP rev is. You would notice  it more on a heavily modified  engine.

 

3 minutes ago, datsunfreak said:

 

Yes, that. A lot of what's in that book is based on what BRE/John Caldwell was doing, and they stuck to the 219 and FIA heads. 

Given these two bits of information I think I need to start all over again, head back to the drawing board and reassess. 

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If looking for a U67 head just look for the U67 on the side. There were no peanut or closed chamber U67 heads.

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17 minutes ago, datzenmike said:

I'm aware of the 210 closed chamber but I don't think it was sent here on any engines. Again probably on an import engine...  The closed chamber 210 head is never talked about. I think it was something Japanese for giving the L16 a slight edge racing but keeping the stock 210 number. Maybe Nissan made them available over the counter just like they did with the 912 head.

 

The one I had came off an early '68 510, and I have heard in the past that some '68s got them factory. I've seen two others, both supposedly from stock early '68 engines. 

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1 minute ago, datzenmike said:

For what it's worth a closed or peanut head is not just a compression bump. There's more to it than that.  Anywhere outside that 'heart shaped' combustion chamber is separated from the piston top but only the thickness of the head gasket. As the piston approaches TDC the air caught in this 'pinch' or quench area is violently pushed out into the open pat of the combustion chamber promoting beneficial turbulence that homogenizes the gas and air mixture reducing hot spots. Naturally a flattop piston is ideal but even a dished piston will gain some from this.    

I definitely read that in some of the Grey stuff.

 

So let’s address this from another angle.  Let’s say I’m wrong, which I often am, and relying solely upon Honsowetz isn’t my best option.  Staying in the L20b block, what is the best head to make power for a fun to drive street truck?

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2 minutes ago, Soundline said:

 

Given these two bits of information I think I need to start all over again, head back to the drawing board and reassess. 

 

Not necessarily. I think you just need to find a good U67 head, port it a bit, and go on.

 

An A87 peanut is only going to help you if you can get good high octane fuel, because...

 

11 minutes ago, datzenmike said:

Assuming you run a higher octane gas and run the ignition as advanced as is safe. Going from 8.4 to 8.9 is barely 1/2 of 4-6%. On a stock L20B that (on a really good day) makes 93 hp that an increase of 2.75 hp at what ever the maximum HP rev is. You would notice  it more on a heavily modified  engine.

 

It's only going to help if you can run your timing right at the limit (around 14 degrees initial) to take advantage of the closed chamber head's resistance to detonation. Which means 93 octane, usually. 

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Just now, Soundline said:

Staying in the L20b block, what is the best head to make power for a fun to drive street truck?

 

Just now, datsunfreak said:

I think you just need to find a good U67 head, port it a bit, and go on.

 

 👍

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Well, could be then. Info shows only 37cc chamber volume and the stock one was 38.5 so not much compression difference really. Also '68 there was not much concern about compression ratios as there was in the early '70s.

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