L28 turbo head/manifold question

[Volition73]

Hello,

 

I'm posting to ask about opinions on L28 head and manifold options...After a bit of reading, it seems the P90 (non A) is the most popular head for L28et setups. I have an N47/N42 combo and have been looking for a P90 to begin a turbo build. I have read that the P90 has square exhaust ports and the N47 has diamond shaped ports. To this end, I haven't had much luck finding a P90 in good condition...I found a reputable fabricator who has quoted me at $600 to $1k to make a custom tubular manifold, for any flange. For this, would you suggest keeping the N47 for the build or keep trying to find a P90 for the custom piece? As far as power goals, I'd like to achieve 300hp to the wheels, but have plenty of room to grow if I wanted it later. I know a stock L28et is capable of this..but I'd like to build the block I have...Any input would be appreciated.

 

Volition

[datzenmike]

Just get and install a square port gasket.

Spray paint it.

Remove the gasket

Grind away any painted area.

When done, taper the inside of the port to smoothly match the walls.

 

You now have a gasket matched square port N47 head.

 

Do the same to the turbo exhaust manifold.

 

Now the head and the exhaust manifold perfectly match without any misalignment or overhanging lip

 

 

 

OR just use a square port turbo exhaust as the diamond port shape really isn't going to make one bit of difference. Spend the $1,000 on an engine management ststem.

[Volition73]

Datzenmike,

 

I was hoping you would weigh in, so if I understand you correctly. If I did what you suggest, I would be able to use the stock 81-83 turbo manifold on my N47 head?

[datzenmike]

Don't see why not. Probably would have no problem even without any grinding. The parts all fit together. I would port match both the head and the manifold. I did this recently on my L20B. U67 head and the cast iron L16 exhaust manifold using an eletric drill and a carbide burr. The head is very soft so go slow and the burr won't plug up with aluminum. The intake is iron and much harder. Just take your time and have fun. I thoroughly enjoyed doing this. It's great doing things with your hands.

[Volition73]

Datzenmike, Thank you, this is what hung me up on choosing the L28 over the LS idea. I've decided to keep the L28, but go turbo. I agree working with your own hands is most rewarding. Seems there are plenty of options for the stock manifold too for turbo upgrades. Looks like I'll be calling Motorsport for a manifold...Thank you!

[datzenmike]

I think the N47 head has steel liners in them. They extend from the exhaust outlet all the way to the base of the valve seat. They should be removed to increase exhaust flow. I have removed them before on a W58 head from an L20B. The valves have to come out as the liner surrounds the valve guide. I slit them in two or three places, using a 6" chisel and a hammer, along their length and folded the soft metal into the port so it could be pulled out with vice grips. There may be better ways as it took me 45 min on the first to figure it out. By number four it was down to 15 min.

 

The liner is thin steel and is held away from the port walls by bumps in the port wall casting. This is so they get glowing hot and will ignite any unburned fuel to reduce hydrocarbon emissions.

[Bleach]

P79 has the same valves and cylinder area but with round ports and those exhaust liners. P79 is much easier to find as it came on all the non-turbo 280ZX 1981-83.

In theory you may be able to use that head and remove the metal liners along with port matching the exhaust ports a bit.

 

Or if you find a head and block combo just buy the whole thing. P90/F54 block. You'll have your dished pistons and an L28.

[ArchetypeDatsun]

I've ran a P79 head in my old L28ET those liners are not coming off but if your worried about them go ahead and remove them I've only heard of a few cases where they came off.

[datzenmike]

They don't come loose for sure. I've taken them out and no frigging way they will ever come loose or out without removing the valve. If this wasn't for a turbo application I would just leave them in there.

[Bleach]

I've ran a P79 head in my old L28ET those liners are not coming off but if your worried about them go ahead and remove them I've only heard of a few cases where they came off.

So what did you choose for an exhaust gasket?

Round port head matched to the square port manifold. Do you choose a round port gasket or square? Did you have any trouble with exhaust leaks or a gasket burning?

[datzenmike]

I would think the square port gives the most coverage around a round hole.

[Volition73]

This is what's confusing me...it's from Motorsports website on the suggested gasket for the stock manifold for 79-83...

 

This is the gasket that spans the intake and exhaust manifolds where they mate to the cylinder head. The gasket "shape" above matches what Nissan supplied as a gasket for all 280ZX heads, and is often called "diamond" port because of the exhaust port shape. It can be used with either a "round" exhaust port cylinder head (N47/P79), or a "square" exhaust port cylinder head (P90/P90A). This casting number can be found between the #1 and #2 spark plugs on the bottom edge of the head. If you know your cylinder head number and would prefer a specifically "round" or "square" gasket to match your head instead of the Nissan design, see Related Items below. For an "N47" or "P79" ("round" port exhaust) head, choose part 10-2513. For a "P90" or "P90A" ("square" port exhaust) head, choose part 10-2512. If you are unsure or have a question, just give our sales technicians a call at (800)633-6331.

 

Turbo Note:

The 81-83 Turbo Exhaust Manifold has a port shape that matches the gasket pictured above. The Turbo cylinder head has an exhaust port shape that matches the square port gasket (10-2512) in Related Items below. So if you choose the 10-2515 gasket, it will match the "diamond" port exhaust manifold, and still work fine with the square port exhaust head. If you choose the 10-2512 gasket, it will match the "square" shaped cylinder head exhaust ports, and still work ok with the "diamond" shaped port on the exhaust manifold.

 

 

 

I thought the N47 was diamond, not round like the information above states...

[I'm BLUE]

All (4) of my N47's are round. They be referring to the liner.

 

You need to do some heavy HEAVY.... reading at hybridz.org ... for your benefit of course. Read all the rules at least 5 times .. no joke.

 

This site has a minority of zcar owners.

[Volition73]

I'm Blue...guess I'm down on my Z knowledge...I was referencing this page for my info...

 

http://datsunzgarage.com/heads/

 

He states the N47 has the diamond ports, that's a site I used to do most of my research...I'm not trying to be a dick, or call this guy out..I just haven't pulled my engine apart to see for myself...Is this link reliable or?

[datzenmike]

The port itself, the aluminum part only, not the liner has small bumps cast into it that supports and holds the liner away from the port wall so it is not cooled and becomes glowing hot to burn off any unburned hydrocarbons. It you look at the port it's possible that these bumps may make the ROUND port look sort of diamond shaped.

 

 

They are NOT diamond but round. Those bumps can be ground away, I've done this.

[I'm BLUE]

I'm always down on my z knowledge... I like to learn and I make mistakes.

 

Round gasket is what fits on my engines with the N47 heads.

 

That's a decent info page to go off of... It's been a while since I've looked at that page

The author could be accurate... Maybe just referring to what the metal liners look like squished inside the port (a couple of ports in one of heads looked a little squished diamond-ish) ... Just didn't explain the last few details I suppose ? I'm not sure

[Volition73]

Datzenmike, thanks for the picture for reference. I can see how the bumps could make it appear as you mentioned...I agree with your earlier post that it would all bolt up the same anyway...

 

I'm BLUE, thank you for your input too. It could be as you suggested too...I'll try and read more on the stuff over on hybridZ as well. Thanks for that..also, can I get your opinion on the N47 since you mentioned you had several? Do you prefer it to other types? What is your build with them as far as turbo or na?

[ArchetypeDatsun]

P79 has the same valves and cylinder area but with round ports and those exhaust liners. P79 is much easier to find as it came on all the non-turbo 280ZX 1981-83.

In theory you may be able to use that head and remove the metal liners along with port matching the exhaust ports a bit.

 

Or if you find a head and block combo just buy the whole thing. P90/F54 block. You'll have your dished pistons and an L28.

I believe I used the square port manifold gasket. Did not leak what so ever.