Which Head Should I Run?

[Jewosh]

Hi. Recently I pulled my motor after I got some bad clicking and knocking and then it wouldn't start. I pulled the head and found that one of the valves was stuck. Now I'm faced with the choice of which upgrades I want to do since the motor is out .

 

Motor Specs:

 

NAPS-Z Block bored to 2.3 (or 2.4 I don't remember)

KA Pistons (dished)

Currently with a stock 1600 head from a stock L16 so its high compression (rebuilt about a year ago)

 

I don't plan on ever running forced induction or anything that would require me to run lower compression and I don't mind using Premium fuel.

 

Choices for Headwork:

 

Keep the 1600 head and run a more aggressive cam and port and polish

Find a U67 Head (and probably have to keep it stock due to budgeting at the moment )

 

Any other heads that would work?

 

 

While I have it out I also plan on replacing bearings and piston rings, anything else I should replace? Sadly, I'm on a pretty tight budget, wanting to keep everything under $1,000

 

If I forgot to mention anything or if you have any questions please post, sorry if I forgot (this is my first motor pull and rebuild).

[DatDoug]

Go with the U67. W58 open chamber would worj too. U67 is the best bet tho. What are you running for carbs?

[Jewosh]

Dual SU's

[Dimerforlife13]

Go for a U67, I have the same set up(z22/ka24 pistons). I went for it because of the port size, and I had a really nice virgin u67 head. Your 210 head is definitely holding you back, the ports on those are too small. I would use any of the larger port open chamber heads. I had a lot of port work done and also had big valves installed. My compression ended up in the 10.5-1 range. Only have ran it for 500 miles with a single weber dgv but the mikunis are going on now...best of luck

[Jewosh]

Go for a U67, I have the same set up(z22/ka24 pistons). I went for it because of the port size, and I had a really nice virgin u67 head. Your 210 head is definitely holding you back, the ports on those are too small. I would use any of the larger port open chamber heads. I had a lot of port work done and also had big valves installed. My compression ended up in the 10.5-1 range. Only have ran it for 500 miles with a single weber dgv but the mikunis are going on now...best of luck

 

Thanks! Glad to know someone else has the same setup. Yea, I just really need to find a nice U67 now, and probably port and polish it as well as a nice cam :) How was it with the Weber and let me know how it is with the mikunis. I really want a nice set but they're out of my budget at the moment :( so my SU's that I got for a steal will have to do for now!

[datzenmike]

LZ23 with 210 head is like almost 11 to 1. Get rid of it and any open chamber L20B head would be better like the U67. This will give you a 9.8 compression.

[datsunz]

Here ya go.

http://www.ebay.com/itm/Datsun-Nissan-510-L20B-620-Pick-Up-Truck-U67-Rebuilt-Cylinder-Head-w-Cam-Nice-/160693708829?_trksid=p5197.m7&_trkparms=algo%3DLVI%26itu%3DUCI%26otn%3D5%26po%3DLVI%26ps%3D63%26clkid%3D4678690973633118445#ht_1418wt_1026

[Jewosh]

LZ23 with 210 head is like almost 11 to 1. Get rid of it and any open chamber L20B head would be better like the U67. This will give you a 9.8 compression.

 

Yea I figured my compression was pretty high but I had no clue how high. So with the U67 what do you think I am looking at power-wise? Especially torque. With the old head it make bucketloads down low but you could tell it was choking in top end. Also, do you think I should do a port and polish, cam, and oversized valves or just save money and time and eventually do a different swap? I really do like L-series but a modern engine would be pretty nice.

 

 

Here ya go.

http://www.ebay.com/...#ht_1418wt_1026

 

Thanks! It's shipping soon :)

[datsunaholic]

Run the U67 as-is first before you start porting and polishing. The bigger ports and valves will help the top end. You had great bottom end because the tiny ports/valves in the 210 head gave you excellent port velocity but as you noticed they were too small once you got to where the power band was supposed to be. The 210 head was bordering on too small for the L16, for a L20B or your frankenmotor it was just way too small.

 

Now, you may want to eventually port and re-valve to bigger stuff, but what I'd do is find a GOOD U67 to run now, and then look for a cheap U67 that needs a valve job anyway and have that one reworked in the future if you think the U67 is too small (and it might be for a 2.3).

[Jewosh]

Run the U67 as-is first before you start porting and polishing. The bigger ports and valves will help the top end. You had great bottom end because the tiny ports/valves in the 210 head gave you excellent port velocity but as you noticed they were too small once you got to where the power band was supposed to be. The 210 head was bordering on too small for the L16, for a L20B or your frankenmotor it was just way too small.

 

Now, you may want to eventually port and re-valve to bigger stuff, but what I'd do is find a GOOD U67 to run now, and then look for a cheap U67 that needs a valve job anyway and have that one reworked in the future if you think the U67 is too small (and it might be for a 2.3).

 

Alright, sounds like a good idea. Yea, it was diesel like almost. Torque way down low but ran out of steam above like 4k RPM.

 

So you think a stock U67 with a stock cam is going to be a good balance of torque and high end?

 

Just wondering, does anyone have a guess as to how much power the motor was making before (with Dual SU Round Tops) and how much you think it'll make now? Just curious

[Jewosh]

I've got a few more questions. First, for the head gasket, are there any that fit properly or will I need to do the same as I did with the old head and just modify/make one?

 

Since I will no longer be running high compression is premium a must?

 

 

Thanks!

 

I plan to have it all back together (I'm doing some engine bay work and wiring) in January and will post pics then!

[datsunaholic]

The head will mount exactly the same, so the gasket is the same. The only difference on the mating surface will be the larger combustion chamber, but you need a gasket to match your bore size. I'm assuming that's why you had to modify it?

 

Datzenmike said your compression will be around 9.8, which is still higher than stock by quite a lot. There's no hard set rule on what octane to use for which compression (cam timing, ignition advance, and RPM all play factors) but for the L-series with more or less factory timing (cam and ignition) as a guide you don't want to run 87 on anything over 9.0, and anything above 9.5:1 or so will need 91+. But using that rule, your old compression ratio around 11:1 would have needed 112 octane. Heck, my relatively stock L20B gets slightly better mileage on 91 than 87, but not enough to justify the cost.

[Jewosh]

Alright. Thanks so much for the info. Im actually outside right now prepping the bay for paint!

 

As for fuel, I might as well keep paying the slight extra for 91.

 

Ill keep you posted!

 

Thanks again

[datzenmike]

Just wondering, does anyone have a guess as to how much power the motor was making before (with Dual SU Round Tops) and how much you think it'll make now? Just curious

 

No way to know how much the restrictive ports and valves would affect this motor. It wasn't the best on an L16 which is almost 1/3 smaller displacement.

 

We know that the L20B (two liter) makes about 110 at the crank. So increasing the displacement by 15% should roughly increase the power by that amount.... say 125hp? This is not exact by any means. The U67 may make 110hp on a 2 liter but has to flow an extra 15% more air for the LZ and may be slightly restrictive. Or not. Maybe it hasn't reached it's limit but I would err on the side of caution and just say 120 hp. For a rear wheel hp rating subtract 17%. About 100 RWHP ....and could be more. Compare this to a stock L16s 60 RWHP.

 

I've got a few more questions. First, for the head gasket, are there any that fit properly or will I need to do the same as I did with the old head and just modify/make one?

 

 

KS pistons, so the bore will be 87mm...... so get a Z24 gasket from a 720 truck and trim the front off. Make sure you compare to an L head gasket and add more holes to the manifold side. You'll notice that the intake/exhaust side on an L gasket has more holes than a Z series head gasket. This is because the intake ports are closer to the hot exhaust ports and this area needs more cooling.

 

Cut the front off an old L head gasket and use for around the timing chain area. It doesn't have to contain any pressure, just fumes and oil spray, so just a thin thin thin smear of RTV on both sides to prevent oil splash leaks.

[Jewosh]

Thanks. That doesn't sound too bad. As for power that should be better then. With some head work and a cam in the future 120 rwhp sounds reasonable.

[datzenmike]

Sure.

[Jewosh]

Great. I'll get back to work on it, and post pictures of it all once I'm finished. Now to decide on the block, bay, and valve cover colors...

[wayno]

I am a little confused again, I have a Z22 block bored to fit Z24 stock pistons(LZ23), and I have a W53 peanut head, and I was lead to beleave that my CR is about 8.9 to 1, do KA dished pistons have less dish than the Z24 pistons? I am running regular gas(87), and I am certainly not up in the 10+ to 1 CR like you guys are talking about, again.

[datzenmike]

Stock Z24 piston dish......... 15cc.

KA24E piston dish................. 2.8cc

 

There was even a 2? cc domed KA piston during the first few months of the 240sx.

 

Car KA24E pistons are fitted to full floating pins on bushed rods. Trucks are press fit pins.

[Jewosh]

So, slight hold up in my build. The new head (U67) came in today, and I tore it out of the box and set it down next to my current head, and low and behold, they appear to be the same size. Now I was told by Troy (and stupidly never checked) that I had the "stock l16 head" Now I don't know if he was referring to the 210 or the 219 but when next to the new U67 head, they appear to be the same.

 

Both have square exhaust and 1.5" intake. The valves are just about the same on both, with the "210" head possibly being a little bigger (I don't have an exact measurement).

 

The combustion chamber on the old "210" head are actually slightly bigger than the U67.

 

 

Basically either the old head is a U67 (and has no markings saying so), a highly modified 210 or 219, or the new head isn't actually a U67 (though it says so on the casting).

 

 

 

Here are some pictures. Post if there are specific shots that I should take.

 

 

 

 

 

 

 

 

 

 

old block has a water jacket under the intake ports and the new one doesn't

 

 

 

 

 

 

OLD BLOCK "Niss" "Japan"

 

 

Old block's markings

 

 

Markings on the old head "A" "S" "#17" "12-5 or S"

 

 

 

Old Head

 

 

Thanks! Please post, I don't know which to use now or what head is really what. Any help is appreciated!

[wayno]

I don't know what your old head is, but it is not the closed chamber high compression head, it is open chamber. That said, IF it is a 210 head, it has been highly modified, definitly some porting to the intakes has been done, but I am doubting it is a 210 head, the valves look wrong to me. I bet datzenmike could shed some light here.

[Laecaon]

The chambers dont look like a 210 head to me... No casting on the side saying what it is? what about casting on the Cam itself? All of my 210 cams say 210 on them.

[Jewosh]

The chambers dont look like a 210 head to me... No casting on the side saying what it is? what about casting on the Cam itself? All of my 210 cams say 210 on them.

 

The cam says Nissan U20 on it. The casting number on top has a 4 and an M. The new one says U20 and M17.

 

The U67 is an open chamber head as well isn't it?

[wayno]

All U67s are open

[datsunaholic]

You took pictures of everywhere except the front, and the side near #3 & 4. Almost always there's a casting number, but that head has some odd bosses on it covering part of the NISSAN lettering.