I read a couple of threads, but didn't find my situation.  I have an L28 (N47 head) in my 240Z.  Can I put a square hole exhaust manifold from a 240Z on the round hole N47 head?  If so, will it bolt right on.

ADVICE REQUESTED:  I have a header on the L28 right now, but the heat is extreme.  Here IMO are my three options:

1. Wrap the header (about $80)
2. Have it ceramic coated (about $300)
3. Remove header and install the 240Z manifold (if it will work) ($0)

What are your thoughts?

Cost is not really the issue, but thought I'd share costs.

I would search around the parts web sites and see if the same manifold gasket, diamond shape is what they call it, would fit the '77 280 and whatever year 240 exhaust manifold you have are compatible.

Felpro makes one that would be the most universal I think.

I've got the gaskets downstairs I could put over each other and take some pics tomorrow and let you decide. It'd be close. Actually I think that's why Felpro makes the diamond shape. To cover both exhaust ports.

Edited February 19, 20223 yr by siteunseen

Wait a minute! You have the injector holes on the N47. Are you running carbs?

@Jeff G 78 can tell you. He runs a p79 with carbs. Same as n47.

 

Edited February 19, 20223 yr by siteunseen

14 minutes ago, siteunseen said:

Wait a minute! You have the injector holes on the N47. Are you running carbs?

@Jeff G 78 can tell you. He runs a p79 with carbs. Same as n47.

 

To answer the question Cliff, yes, the carbs work fine on the N47 or P79.  I used a round port header with a P79 manifold gasket.  There was no issue at all with the injector notches.

As to the original question, I've read that you can run the square port header on a round port head, but I've never tried it and I'd imagine that you'd lose a bit of low end power, but not a lot.  I'm not sure which gasket to run when you do the square/round combo.  I'd ceramic coat the header or sell it and buy a round port header already coated.  I would only wrap the header if it's a race car that is always run hard.  Florida is too humid IMHO for wrap.  The header will rot quickly.  I learned after a lot of trial and mostly error that the header coating/wrap will not prevent vapor lock.  On my race car, I finally figured out that ditching the fuel rail and running rubber fuel lines to the carbs with no return was the best way to keep the fuel cool.  The steel rail bolted to the head was a recipe for conductive heat right into the fuel.

Yes, I'm running SU carbs.

Thanks guys.  It's definitely not a race car.  The header is new and correct to the L28, so it's already round port.  I'm reading more bad things than good when it comes to wrapping the header, so I think I'll put that option on hold.

Between the other two options, I may investigate which gasket to use and try the 240Z exhaust manifold on the L28.

@Jeff G 78Do you still run the fuel rail on a non-race car? Or, do you run hoses?

3 minutes ago, HappyZ said:

Thanks guys.  It's definitely not a race car.  The header is new and correct to the L28, so it's already round port.  I'm reading more bad things than good when it comes to wrapping the header, so I think I'll put that option on hold.

Between the other two options, I may investigate which gasket to use and try the 240Z exhaust manifold on the L28.

@Jeff G 78Do you still run the fuel rail on a non-race car? Or, do you run hoses?

Just run the L28 gasket.  I never ran SU's on the street, so I cannot answer, but try it as-is first and see if you have any heat issues.  If so, then you can address the heat.  FYI, don't attempt to wrap the fuel rail to keep the heat out.  It won't work.  It will just make a nice thermal layer to hold the conductive heat in.  If you have issues in the FL heat, you can perform a simple test to see if eliminating the rail fixes it.  It took me less than 10 minutes to cut some hoses, add T fittings and clamps and clamp off the return hose.  I did this during a pit stop in a 14 hour race.  $10 worth of fuel hose, T fittings and clamps will prove or disprove that the issue is the rail.

When I raced, the manifold and later, the header, would glow cherry red.  You couldn't see it during the day, but it was really wild to open the hood during a night pit stop and see the glow.  We'd always open the hood and check the oil at every 2-hour fuel stop.  We were obviously making a LOT of heat compared to anything on the street.

@Jeff G 78thanks for the help.  I may start another thread, but I'll ask here first.  Do you know if I can run a 240Z distributor in an L28?

 

6 minutes ago, HappyZ said:

Do you know if I can run a 240Z distributor in an L28?

Why would you want to?  Run a ZX distributor.

6 hours ago, HappyZ said:

@Jeff G 78thanks for the help.  I may start another thread, but I'll ask here first.  Do you know if I can run a 240Z distributor in an L28?

 

6 hours ago, Jeff G 78 said:

Why would you want to?  Run a ZX distributor.

I believe @HappyZ is intending upon running a Pertronix or some other electronic ignition that can be retro-fitted into a 240Z distributor. Yes, you can put the 240Z distributor on the L28. And as for heat rise, I fabricated my own heat shield for my setup with an L28 with a Maxima head. I also have square port headers on it that I've been running for 5 years. I don't know if the engine is losing low end power. It pulls well.

That’s very encouraging … thanks.  I think I’ll try to fabricate my own first.