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My Turbo L-Series Build (Previously question for best turbo L-series head)


D52E

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So I've been contemplating the idea of turbocharging the L20B and I had several questions to ask other members. I have asked a company about producing the manifold flanges and they requested that I ship them a cylinder head so they can measure and create the pattern.

1) Which exhaust port shape is best for the turbo manifold? - I have an open chamber W58 head with round ports in my collection. Round ports would be easier to fabricate at the flange?

2) Should I search for a U67 square port - is there any advantage?

3) The company has tentatively agreed to sell me 10 manifold flanges for the cost of 5 in exchange for shipping them the head. If I do go this route, I would prefer to get the more desirable shape round/square so I don't get stuck with 9 flanges no one wants. I am leaning towards the round port flanges.

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For flow purposes the larger ports of the square exhaust would be beneficial, however the U67 and W58 (roundport) heads have the same valves. Since roundport heads are generally avoided, squareport would probably be preferred.

 

Or, you could hybrid it. Take both a square and roundport gasket and open up the overlap (squareports are taller, but roundports are wider), then design the flange to fit that so that the outlet doesn't shroud either. Then it'd work for both, as the bolt pattern is identical anyway.

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I cant say for sure which one has better flow #'s, but the square port was run on many models for many years, and the round port was only for 2-3 years. If you are looking to sell these, I would go square.

Too bad, I just had a couple laser cut last week.

 

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A turbo will make just about any head flow. For example... to get 9 pounds of boost into a cylinder you may have to push a little harder is all. Just dial it up to 11 pounds.

 

For L20B, a U67 or W58. Remove the exhaust liners on the W58.

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So I've been contemplating the idea of turbocharging the L20B and I had several questions to ask other members. I have asked a company about producing the manifold flanges and they requested that I ship them a cylinder head so they can measure and create the pattern.

 

3) The company has tentatively agreed to sell me 10 manifold flanges for the cost of 5 in exchange for shipping them the head. If I do go this route, I would prefer to get the more desirable shape round/square so I don't get stuck with 9 flanges no one wants. I am leaning towards the round port flanges.

 

If the flange is all that's stopping you from using the square port head, I can get them in singles from the local waterjet place I use... Have to call and get an updated price though, I haven't cut one in a couple years.

 

flgn002s.jpg

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My concern is that I only have a round port head and I was wondering if I should go thru the effort of finding a square port for better performance and more common use of the flanges.

 

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Other than the round exhaust port and liners the W58 and U67 are pretty much the same. You can run a square port header or manifold on a round port. If making a turbo manifold I would imagine round tubing is way easier to match to a round port than square.

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There used to be a guy on the 510 realm that sold 1/2" thick round port flanges for $85... As previously mentioned square port stuff will fit a round port head, and not the other way around. I would personally not pull the trigger on getting a bunch of round port flanges made... I don't know if it still bodes true, but for the most part the round port heads were not that desireable, and even if they are desireable now, they were only used for a short period of time as compared to the long time span that the square port head was used.

 

I talked to the waterjet place yesterday while I was picking up parts. They still have all my old flange drawings (which is good because I lost all my old files on a HD crash).

 

A 1/2" sq port flange would be $75 shipped (to the lower 48), a bit more to anywhere outside the US... If you are interested.

 

Unfortunately my round port flange drawing was never sent to waterjet for a quote, but I could re do it. I have a couple round port heads, and probably the gaskets hanging around somewhere I could take measurements off of. I imagine the price would be about the same.

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I talked to the waterjet place yesterday while I was picking up parts. They still have all my old flange drawings (which is good because I lost all my old files on a HD crash).

 

A 1/2" sq port flange would be $75 shipped (to the lower 48), a bit more to anywhere outside the US... If you are interested.

 

Unfortunately my round port flange drawing was never sent to waterjet for a quote, but I could re do it. I have a couple round port heads, and probably the gaskets hanging around somewhere I could take measurements off of. I imagine the price would be about the same.

 

Wow, thanks for looking into this for me. I've been working on a deal to purchase a few square port flanges. if it does not wok out, I may have to take up your offer to help.

I have requested to get square port 1/2" thick flanges from the source I found. I will update the group when I get them but it may be some time. Perhaps a few weeks.

 

Mike and H5WAGON, thanks for the tips on the exhaust liners. I will be removing them and doing a light port job on the head when i get some time.

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  • 2 weeks later...

OK, so i have a small update;

I found a U67 head and U20 cam at the local pull and save. it has unmodefied ports and origial bronze/brass intake valve seats. Te plan is to change the valve seats and use 44mm intake valves. Also, get some porting to intake and minor exhaust porting.

 

The head has been shipped to the company that will be making the manifold flanges for me. Hopefully in a month or so i can get these done.

 

I was hoping I could get thoughts on a few items:

What additional head modifications should be done?

What camshaft - stock U20 or Rebello 279 duration with about 0.500" lift

Exhaust manifold - log or long runner style

Intercooler - what is the best way to limit the core support modifications to the car.

Other items - front mount intercooler - sidemount intercooler - water to air intercooler - water injection

What modifications need to be done to weber DCOE carbs - sealed bearing throttle shafts?

Electric fuel pump and rising rate regualtor?

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U-67 should have the hardened seats. I think Datsun started using them in the late '60s

 

Very little needs to be done to the head. Look at it this way the engine has to work hard to suck air through the ports so sharp bends and obstructions will make this harder BUT a turbo pushes air in under pressure so the motor doesn't care much how well or bad the ports flow. There's an old saying that God made man, but Samuel Colt made them equal. A turbo is a great equalizer. It makes all heads flow better. Yes you can port them if you want won't hurt.

 

All cams have what is called overlap, a small amount of time when the exhaust valve is closing while the intake is opening. Both are slightly open at the same time. Everything works because the exhaust is flowing out the pipe so fast that it hasn't time to turn around and try to get out the opening intake. Likewise, the air in the intake port was flowing towards the valve and can't stop instantly and collects there. When the intake opens it rushes in. A race cam increases the duration because at ultra high RPMs there is even less time for the exhaust to reverse and the intake port will build even more pressure from the inertia of the fast moving air. Now the problem with a turbo is that with high overlap, the intake pressure is so great that gas and air will be forced into the combustion chamber, over the piston top and right out the open exhaust valve. The more overlap the bigger the waste. Look at the specs for a real turbo cam and you will see very little overlap increase over stock. A stock cam is fine for a turbo.

 

Exhaust: This is very expensive to make right (nice round bends and tight space) but individual pipes into a collector for the turbo is most efficient. Log manifolds are cheaper and easier.

 

Inter cooler. Can only be used in a blow through set up. Don't like the looks of front mount. They look like you failed at engineering a proper set up or are running a fake for show. Keith Law has a custom one in it's own air box with ducting to the front grill area. Not sure if he has an electric fan to force air through it, but with enough air flow you could make it smaller right?

 

Water injection? If I went to that much trouble I would make it water alcohol injection to drop ambient air temps.

 

If running a blow through set up you don't need to seal the throttle shafts as the air around the carb is pressurized.

 

Yes the pressure regulator needs to keep pace with the boost +3 PSI for the carb at all boost levels.

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  • 2 weeks later...

You must be getting the flanges dirt cheap? I'm just curious why you would commit to sending some place your head, and buying 10 sets of flanges (even though you're only paying for 5 sets), when there are multiple places to get the flange without buyin 10 sets... Why spend more than you have to, and reinvent the wheel at the same time?

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round port is easier to build since tubing is round. i paid a shop 20 bucks for my napz flanges. tyey were only 1/4 inch and needed cleaning up cause he used a plasma table but i had to clean them up after welding any ways. if you want all i need is to give him a gasket and he can make it(1/4 is the the thickest he can go though.

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Racnjsn95 - The flanges should hopefully be about $30 to $40 a piece after adding up all costs (shipping back and fourt plus cost of the 5). I figure that there has to be a few members on this forum that would be iterested in the 8 flanges I wont need. Hopefully the quality is good and I can pass on the savings.

 

Also a small update:

I got a Garrett GT22 cheap - shaft feels tight

3A12A8DF-A958-45DC-A4DA-E1A02538C79F-2498-0000062473EBE548.jpg

I found a small water to air intercooler for a good deal

D30DD497-00F5-47EC-AB42-E8DED2E16A15-2498-00000624608B2430.jpg

Bypass valve

3CACE3D7-AE23-4BEC-9F71-88B26D92ACC7-2498-00000624F288E74D.jpg

Nismo hedgasket

AD65D1FE-0EB3-41CE-9C9A-2528590FE580-1947-000003556C5B46FB.jpg

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  • 1 month later...

Latest aquisition - Z22 engine block from 1983 720 4X4 truck.  Bore is at 87mm and looks like stock pistons (mileage unknown).  headgasket was original looking and labeled Nissan.  Oil looks and smelled ok - no aparaent metal debris visible in oil.  Engine turned over freely and compression resistence felt on all 4 cylinders.  Clutch that came on it was coming apart (possible reason for truck in junkyard?).  I will take the oil pan off and check rod/main bearings later.

 

If I match this block with the U67 head i will have to do some valve unshrouding and combustion chamber CC'g to reduce compression.  According to the OZDAT calculator this will yield 9.7:1 static compression.  I will have to remove about 6CC's to bring the static compression down to 9:1.

 

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297BCA7B-8DE4-4B8E-BEE7-1D85C3116A6B-182

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  • 3 weeks later...

I don't care for the calculators. I get 9.84 compression. Nothing wrong with high compression on a turbo motor. It will have more snap when not on boost, which is most of the time. Definitely remove meat around the intake valve. You can also round off that edge where the peanut shape transitions to open chamber.

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One more aquisition - Fuel rail from a fuel injected Mitsubushi pickup - mid 1990s?  Looks like the injector locations lined up pretty good with the L20b head.

 

089DFEF2-93B8-4EA6-9499-4701631A4CA6-110

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