Head identification

[Speedracer906]

 So in another post, http://community.ratsun.net/topic/69184-a46-intake-on-l20b/

I asked about the functionality of an A46 intake. Well that had now turned into what head do I have.

 In the discussion datzenmike pointed out that the head seemed to be a A87. I left with the new knowledge that I had a L18 head that was gasket matched at some point. In looking up the specs on this head, I noticed that this head was used for some L20Bs, but also some L18s. I took some measurements and some pictures and I feel like I have a head that, if nothing else, would be a fine head atop a L20B block, No?

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No code, filed off for some reason.

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Valves...

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Rim of intake port.

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Inside the intake Ports

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Rim of exhaust, the inside does taper in some.


 To me, this head seems very L20B-ish, what do you all think?



 

[flatcat19]

I think k it would be fine on an L20B or L18.

If the surface is flat, you're good to go.

 

 

I also think you didn't need to start a second thread about the same thing as your other thread.

 

 

They're simple motors. Don't over think it.

[datzenmike]

The A46 intake. Never heard of it being mentioned to identify an L series intake. A46 is most likely a casting revision code and there may be dozens of different codes for basically the same intake casting. The U67 head uses a vastly different intake from the W58 head in that it is bolted to the exhaust manifold and does not have coolant flowing through it. The L16/18 intakes have smaller ports than the L20B intake and the '74 L18 has an EGR manifold bolted to the intake similar to the L20B but the earlier L16 does not. 

 

 

I'm told the A87 was used only rarely on some very early L20B engines. I've checked part numbers and cannot confirm this.

 

Earliest use of the L20B was the '74 610. The only other vehicles then with L 4 cylinder engines were the 710 and the 620 and both used L18 engines in '74 and switched to L20Bs in '75. As far as I know only the U67 was used on the L20B through '77 and the W58 from '78 -'80.

 

The A87 head would be a fine swap onto an L20B as the combustion chambers are the same volume as the U67 and W58. The valves and port sizes are slightly smaller so it would not breath as well.

[Stoffregen Motorsports]

A46 is a casting number. The A46 intake is probably the best stock intake for a L 4cyl.

 

If there is not a casting number on the side of the head, it's likely on the front of the head, next to the timing chain inspection cover. Judging from the casting, it looks to be a late casting, but a nice one.

[datzenmike]

What was the 'A46' used on? If an early L16 it won't be the best for breathing on an L20B I expect.

 

I have an L20B one marked W58 here for measuring. Also one from a '75-'77 L20B but can't find the marking.... it's not much good as it's the co-joined model that bolts the intake and exhaust manifolds together.

[Stoffregen Motorsports]

The A46 intake came on early L16's. They work well even on large engines.

 

Mods to make them work better include cutting out the splitter between the primary and secondary ports (where the carb mounts) and blending the area or even slightly growing the bowl area. Match porting to the Weber carb adapter usually makes a difference too.

 

I have seen guys weld the Weber adapter in place and hog the crap out of the bowl, but I've never tested such an intake.

[datzenmike]

I think that's what Ztrain did on his 2.3. It makes impressive torque numbers down low. Probably from the increased air speed.

 

The W58 that I have has 1.33" ports. Pretty sure it's from a '79 truck (with W58 on it) so that matches up well with their 1.375" intake ports. I removed the EGR and ground away some, then JB filled the two holes and drilled and tapped the PCV...

 

[Speedracer906]

I didn't measure the ports on the A46 but compared to the gasket and then the gasket to my intake ports on the head the intake looked too small. I suppose I could try my hand at hoging it out to flow and match but the allure of side drafts have my attention now. Good to know that It may not be a poor choice to use the A46 intake though!

 

I was looking at the cam on my A87 head. The cam is a crane and based on my friend assesment of the stampings I might have 272 lobes.

 

 

It was said that the 272 is about max for a Datsun l motor. Yes/no?

[Stoffregen Motorsports]

Be careful porting that intake. Since the restriction is not the 4 port area, but the area upstream instead, porting can actually hurt the flow.

[Stoffregen Motorsports]

And there's a lot more to spec' ing the right cam than the cam itself. Lift and duration are highly dependent on compression ratios. Too low or too high a CR and the cam can't do its job.

[Speedracer906]

So theres my concern then. I have 20 over stock dished pistons used in my rebuilt block.

I'm not looking for absolute max return on these parts I have but I certainly don't want to have unreasonable issues. Any wild guess what the decreased CR would be from the over bore on my block?

 

I'm still looking for the reason to use or don't use this head. Would it be best to use on a differently built block? Should I support it's flow-ability with sidedrafts and a header? Etc. I'd like to end up with the best outcome, and spend the right moneys on getting what I have, put together with the best outcome; for the money.. :)

[Stoffregen Motorsports]

Increasing the bore size also increases the CR as the swept volume is now larger.

 

You probably need to do some engine math to figure out what your CR is. There are engine calculators online, but I like to do the math. Here is a link showing the calculations for basic engine math. http://www.lunatipower.com/Tech/Pistons/HelpfulCalculations.aspx

 

As far as the side drafts go, that's a whole 'nother can of worms. You probably want 44 or 45 mm carbs, a good intake (there are some very bad ones out there), good isolators and centerpull cable linkage to get it all working properly. A mechanical fuel pump can supply dual carbs, but an electric fuel pump is a safer bet. Also be sure to get a good low pressure regulator (Holley makes a good one).

 

Headers are a good idea too, but the only good one out there is the one from Nissan Motorsports. I don't know if it's still sold through Nissan, but someone like Rebello can supply one for you. Then you're going to want a sizable exhaust, 2.5" with a turbo muffler or a lazy s muffler (Dynomax or Borla). Recurve the distributor too.

 

There' you've just spent $5000 to put dual carbs on your L motor.