620 Land Speed Record

[datzenmike]

W58 are round port exhaust and used from '78 -'80 on the L20B.

 

A87 depends is modified or not. If it flows good stock, U67 and W58 would flow even better.

 

Closed chamber 41cc heads are from JDM engines that were cheaper to import than rebuilding a customer's head here. This is why there are dual L series Hitachi SUs floating around and long dogleg 5 speeds. All that was used was the block or head and manifolds and transmissions were incompatible with the vehicles here.

[distributorguy]

I believe my A87 came from a 1600 here in the US.  My W58 came from a 720, and unlike many posts that specify different, its a closed chamber head.  CCs?  Well that's a whole different conversation.  I left the quench area alone on mine, the rest is opened up to unshroud the valves and to work with the domed pistons. 

 

Stock A87 head flows 172 cfm at .500" lift intake, 146 cfm exhaust.  I've gained about 50% over that so far, but managed to keep ratios around 80%.  

 

The port placement on the FIA is much improved over stock, but stock heads are incredibly thick and the port can be moved as well, especially when you start with 1 3/8" intake ports.  That extra 1/8" is a HUGE amount of volume when you shed the turbulent areas and go a little bigger on the valves.  Go too big on the valves and you just shroud the airflow into the cylinder.  Its a fun balancing act that you can't get right until you go past the point of no return.  No one is lucky enough to build the ultimate head on the first try.  So far I have done the "safe" modifications.  From here on out it comes down to creativity.  At this point, I may have the best flowing A87 head at .500" lift ever built. ?  Valve size may be keeping me from getting better flow above that, although my cam ends at .550" lift under the assumption I wouldn't be able to prevent coil bind above that, and running out of spring can stop us from hitting the rpms we need to win.  One hell of a balancing act.  

[G-Duax]

I have a few pictures of L-series head cutaways. PM if you would like to see them.

[Jester]

 PM if you would like to see them.

 

WTF???  I wanna see too. Please, post em up. 

[datzenmike]

A closed chamber head was likely imported. It isn't the best choice for an L16 but what do mechanics know. A closed chamber L head will drop the stock L16s compression from 8.5 down to 8.2. They (open chamber A87) are really an L18 and early L20B head. Closed chamber (A87 even W58) are probably from import engines in the '80s. 

[distributorguy]

Yes from Datsuns imported to the US market.  The W58 closed chamber head came on the 1980 720 new.  One owner, never registered for road use.  This was donated to the Brainerd International Raceway here in MN and used for a security truck.  Its history is well documented, and that's the way it was built.  The other truck I own is a '73, which had the head I'm porting installed.  It was pretty clear that engine had never been apart, nor had it probably run for more than 10 years before it was parked - shipped up here from NM.  

There is a lot of false info about what heads are open and closed chamber.  Either that, or I got lucky and both trucks I bought had them.  ???  The closed chamber heads have smaller chambers than open chamber, so how will they drop compression ratio?

[datzenmike]

The L16 came with a 210 or (number) head. The combustion chamber size is 38cc. Closed chamber heads are 41cc. The only closed chamber head used on an L16 came on the L16SSS engine only on the Japanese 510 Coupe. To offset the compression loss flattop pistons were used. 

 

N Am L20B normally have 8.4 compression. A closed chamber head bumps the compression to 8.9 and would seriously throw the emissions readings off the charts. Plus it might likely ping at or near the 12 degrees timing with the shitty gas we have because closed chamber heads have an ineffective quench area. This is because L20B pistons have a huge 11.36cc dish and not flattop pistons..

[distributorguy]

Emissions readings have no direct correlation to compression.  In most cases, increased compression makes the engine more efficient, so it can be tuned to run with less fuel,lower emissions.  Those who think they can modify an engine with a high compression head and no tuning shouldn't be working on engines.  Apparently there is no documentation on which heads went where, because I don't have a SSS head, and it came on a US market 1600, in a 620.  Clearly a large quench area, clearly small "peanut" chamber.  Bone stock truck right down to the original bench seat cover and vinyl floor mat.  This was no "performance truck" yet it had a small chamber head with factory dished pistons.  Sorry Mike, your facts are incomplete.  

[G-Duax]

OK, a few head cut away shots.

I probably will start a seperate thread on this, since forum search functions create more vacuum than a stock engine being reved to 8k, and banging the throttle closed.

(nice way of saying they suck)

 

Only one of these is of a known head, and L6 Y70, that looks to have had the steel inserts in the exhaust, that were removed.

Here it is:

 

 

Here are the rest:

 

 

 

And I have a cut away here, that I picked up out of Japan years ago, but never took any pictures of.

Also an L6 head, as it still has the letter 'N' on the part I have. Not sure how many heads had the prefix 'N'.

I'll try to get that done at some time in the future.

[datzenmike]

Yes they do, and why compressions dropped and EGR was introduced in the early to mid 70s. High temps and high compressions increase the bonding of Nitrogen and Oxygen in the air during the combustion process, producing 'smog'. You are right about higher compression increasing the energy capturing efficiency.

 

Only way your L16 has a quench area is if it had flattop pistons. All L16 had dished pistons. Only the L16SSS came with them or they were replaced. Do the math. L16 with 41cc head = 8.2 compression. L16s were 8.5

 

Show me a Nissan part number for any N American vehicle with anything but a 210 (L16), A87 (L18), or U67/W58 (L20B) that is anything but an open chamber 45.3cc combustion chamber. Thousands of engines were imported in the 70s and 80s as a  cheap replacement or parts for domestic cars and trucks, rather than rebuilding or replacing them. There may be a rare W53 or an A87 on an L20B but they will be open chamber. If closed it was imported. Yes there are closed chamber heads out there. I've looked and the W58 head is used on all 620/S10/A10/720 applications and it is the same part number. There is no 'peanut head' part number.  

[datzenmike]

I think we are discussing L4 heads but thanks.

[G-Duax]

I posted those per request of the OP.

And they are of heads......

And were pretaining to his earlier posts on porting.

[distributorguy]

Closed chamber and peanut head are interchangeable terms used by Datsun owners.  I have quench area with the 1973 A87 closed chamber head on my L20b.  Stop arguing over semantics Mike.  You don't have to prove yourself on every post.  My 1973 is a 2-owner truck and my 1980 is a 1-owner truck, both with original engines.  Both with closed chamber heads.  I'm stating clear facts that can't be argued.  

Bummer those head cross-sections have nothing to do with the head we're talking about.  

[thisismatt]

Mike has a closed chamber head

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Awwwwwwwww yeaaaaahhhhh

[G-Duax]

Bummer those head cross-sections have nothing to do with the head we're talking about.  

 

Yeah, I know, but you can see some simularities.

But if I stumble across any DOA heads, I'll add to collection. they are faily easy to cut.

[distributorguy]

I wonder if the cross section of an open chamber head is the same internally as a closed chamber?  If so I'd cut up a spare here but you just never know if they used different internal cores to reduce casting thickness in certain areas.  The issue comes down to available material for porting.  If you go too deep, you start over.  I'm 30+ hours into this head already and don't really want to do that.    My concern is the coolant jacket shape near the valve guides, especially on the intake side, A87 closed chamber.  

 

 

Mike has a closed chamber head















Awwwwwwwww yeaaaaahhhhh

Now that's funny!!!

[G-Duax]

I've seen a lot of heads that had to be welded up due to a break through into a water jacket.

Often wonder how welding ended up closing off an important water passage...

[Stoffregen Motorsports]

I don't think there's an issue breaking through near the valve guides on any L4 head. That part of the port doesn't need to be raised that much at all.

 

This link here http://www.yoesheadporting.com/is the guy who does the porting for Rebello Racing. He and I worked together at Rebello's and now he's off on his own. Check out some of his pics and give him a call if you have any q's.

[distributorguy]

It looks like his photos are also 6s, or newer 4s, other than one chamber photo.  I'm well versed on using the flowbench, just not with the internals of this casting.  So far so good, although I've done a couple things most cylinder head gurus would scratch their heads about.  But then again my flow numbers are the highest I've seen posted anywhere, and my bench was calibrated just last week so I know its within 1% accuracy, for whatever that's worth.    Back at it.   :poke:

[datzenmike]

 

If using these pistons with a closed chamber (peanut) head on an L20B... yes you will have a quench area. If stock L20B pistons you will not is what I was saying.

 

Can you post a picture of your combustion chamber?

[Jester]

  Stop arguing over semantics Mike.  You don't have to prove yourself on every post.  

 

:lol:  :lol:  :lol:

 

Mike has a closed chamber head

 

 

 

 

 

 

Awwwwwwwww yeaaaaahhhhh

 

:rofl:  :rofl:  :rofl:  :rofl:  :rofl:  :rofl:  :rofl:  :rofl:  :rofl:  :rofl:  :rofl:  :rofl:  :rofl:  :rofl:  :rofl:  :rofl:  :rofl:  :rofl:  :rofl:  :rofl:  :rofl:  :rofl:

[wayno]

According to the WIKI literature I have, the L20b was introduced in 1974 in the 610, and was not put in the Datsun 620 till 1975.

According to the Chilton manual the 1973 Datsun 620 came with a L16 and L18, the 1974 Datsun 620 came with the L18, and the 1975 Datsun 620 came with the L20b.

[distributorguy]

Yes Wayne my '73 has a 1600, '77 had an L20b. Both with closed chamber heads.  

 

Yes Mike those are the pistons I'm using and half the chamber is flat, just like the piston - same contour.  Quench area.   I had to radius around the plug area for clearance, but that will help the spark travel over the dome.  I'm still playing with combustion chamber design.  There are areas I wish I had welded but its too late now. I'll post a pic when I get one finished.  There is so little clearance anywhere at 15:1 that you could say the whole combustion chamber is quench area.   :hug:

[distributorguy]

Pretty crude at the moment, a bit camouflaged with Dykem, but here it is:

[/url]">http://http://s1148.photobucket.com/user/distributorguy/media/head%20chamber_zpsgayfspmw.jpg.html'>

 

What you can't see is valve height/diameter versus seat location.  

[datzenmike]

I always thought for all out performance that the valve guides and those lumps around them should be ground away. :thumbup:

 

The quench area below the plug is ground away...for the piston dome?