A46 intake on L20B

[Speedracer906]

I'm putting together a l20B, opened up +20 over and installing an unknown head, but one that looks like it was nicely ported and I was told it was a racers head that was replaced for another build spec. I can add a photo later.

The question today, as I'm sure I'll have a few later, is about the intake I have. Th doaner engine that I happen to have, for all sorts of anselary accessories, is an l16. On that L16 is the intake pictured, an A46.

Kinda small ports for any l20b let alone one with bigger pistons and a free-er flowing head, no? Well I wanna use it unless a consesus says no. If I do use it, should I try and massage the port opening on the intake to minimise the shoulder the atomised air will pass over on the way to the head? BTW I plan on useing a weber 32/34 but may pose the question about re jetting the stock carb that came on this l16' it looks in decent shape.

 

-now, to figure out how to post a pic..... Nube!

[datzenmike]

The head is ID'd by looking between the #1 and #2 spark plug along the bottom of the head just above the block. You should see something like MADE IN JAPAN  U67 or W58, possibly A87. These are L20B heads with fairly large valves and posts,. The most common are the first two. The A87 is an L18 head but sometimes found on the very early L20B.You do not want a 210 head as this was for the L16 and has small ports and valves.  

 

The best breathing head for an L20B would be the 219 head from an L16/18 SSS or the re-issued 912 head. Large valves and ports and a closed combustion chamber.

 

The best intake for an L20B would be a '78-'80 L20B intake. They would be the largest.

 

 

Pictures...

http://community.ratsun.net/topic/54932-photobucket-ratsun/

[Speedracer906]

Thanks datzenmike

 

So, I'm working on uploading to my Photobucket. Tic toc.....

 

On the head, the only # on the head is on the back side and that # is 70. It appears that the heads reference was filed down for reasons unbeknownst to me.

My question on the intake, the real reason behind this post, is will the A46 work without too much issue when I run it into this now better breathing longblock setup, ie better flowing heads and 20 over pistons? I do like the simplicity of the A46, should I do a bit of grinding away to match the dia anybetter?

[wayno]

In the end it is an L16 intake manifold, sure you can grind on it to port match it to the head, but it is still an L16 manifold with small runners, it is a restrictive manifold bolted up to a L20b head, it will likely work fine without even touching it as it is a small hole emptying into a big hole.

Does your head have the water ports below the intake holes?

You would be better off spending your money on Dual SUs or some other side draft setup, they already have the large runners.

I always think of an hour glass whenever someone talks about a stock L16 intake manifold, it likely will work fine if you keep your foot out of it, but you can only get so much air thru an inch and a quarter hole/intake runner.

[datzenmike]

Should look something like this...

 

 

 

ABOVE

Look just below and between the two pair of intake ports. Does your head have those holes?

 

 

 

BELOW

Or does it not have them?

 

 

You'd better post a picture of what you have. I don't know why anyone would grind away the ID letters.

[banzai510(hainz)]

read olddatsuns.com the tech section

eveything is on there. read alot

[Speedracer906]

Wayno, you made the sale. Golf ball through a straw....

Datzenmike,

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This above is what I got's for a head.

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see, no markings...?

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Banzai510(Hainz), I watched your timing chain video yesterday with coffee and a danish. Good info and put things together for me from past projects that eluded me then. As soon as I redo the valve stem seals I'll be able to tackle the front housing like a boss! And yes, the olddatsuns.com page is a great site.
I need to organize all my bookmarks to allow for an easier read on all the tech stuff out there.

 K, so I'll forgo the A46 intake idea and look for something more fun, instead of thrifty, but now that we brought it up, what head would this be?

 Thanks, Y'all!
 

[bilzbobaggins]

What are the intake and exhaust valve sizes? Picture of them too please. Size of the opened up intake ports? I'm on my phone so it's hard to see the pics well. Does it look like it's rough like someone ground off the id marking or just nothing? I believe some of the early 210 heads had no id markings on them

[Speedracer906]

I'll take better pics and post tonight.

[datzenmike]

I can tell you what it isn't. It isn't a W58 and it isn't a U67. If it was ported it's unlikely a 219 or 912 as they already have huge 1.5" ports... I suppose someone might sand them down or polish them but no need to 'open them up'.

 

This would leave the L18's A87 and the smaller stock L16s 210

[Speedracer906]

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 Ported fairly nice

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1.5 is right on

 

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Exhaust, Sorry a bit blurry

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Valves

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#70 ??

So this is what I got. Thanks for looking into this!


 

[datzenmike]

 

These are likely just a casting revision or a mold identification. They sure wouldn't have used a single mold to make hundreds of thousands of heads.

 

 

 

 

NOT a 210 L16 head. The intakes are too large.

 

NOT a W58 or a U67 head.

 

It's likely an A87 head from an L18. They had small 1.25" intake ports, just right for a smaller L18. It's common enough to gasket match them to the intake gasket. This isn't opened up all the way to the valve, just an inch or so. I wouldn't call it 'ported' but gasket matched to smooth the flow

 

The U67 and the W58 are L20B heads ports are larger and are about 1.38" all the way.

 

The 219 and 912 heads are the only true 1.5" intake port and flow the most air.

[Speedracer906]

I gotta think about my choices.
I'll measure this A87 to my U67 and and make a judgment call later, my day is dun for now.

 Thanks!
 

[datzenmike]

Definitely run the U67 if it's going on the 77 620.

[wayno]

The U67 already has big valves and intake ports, and since the mystery head has big valves/been ported, and is also open, I would just use the one in better shape, use the one that needs the least work. 

I am a big fan of side draft carbs, I have dual SUs myself, they are way better than a Weber downdraft in my opinion, I have had the same SUs on my work truck since 1995, but I bought them new from Nissan when they had a clearance sale, wish I had bought 2 or 3 sets now, but I didn't have the money back then.

I gotta think about my choices.
I'll measure this A87 to my U67 and and make a judgment call later, my day is dun for now.

 Thanks!
 

[datzenmike]

Yes if one is in better shape run it. The A87 isn't ported out to 1.5" only gasket matched so it still has much smaller 1.25" ports. The U67 port is 1.365" all the way to the valve and is a true L20B head. If both in good shape run the U67.