has anyone converted a Datsun 280zx Turbo Intake Manifold to fit a L18(20,16)?

[pondking]

??

[Fat510]

yes, but i dont know who does it

[bananahamuck]

yes, but i dont know who does it

 

The ZX intake has full webbing(?) in between the runners which would IMO make it impossible to cut and piece together.  The one we have on the shelf  is an older type,,, without the webbing.

 

HRHs' friend made it.

[datzenmike]

Yes but some manifolds are not parallel to the head and tilt farther away at the front. Front runners are slightlu longer than the back ones. When sectioned they don't line up very well.

[pondking]

why isnt there a adapter by now?

[620Turbo4X4]

I'm in the process of cutting a 280z n42 down for a l20b now. It's not as easy as one would think. Like datsun mike says once the center cylinders are cut out the two half's don't line up well. Truthfully, making one from scratch with tubing is almost easier. The ports on the z car efi manifolds are tiny (about 1-1/8") and there is not a whole lot of meat on the runners, so opening up to 1-3/8" is about as far as you can go safely without grinding it paper thin, or worse, through it.

 

I'll see it I can't snap some photos of it tonight when I get home...

[datzenmike]

Smaller diameter runners are good for keeping the air speed up. This high speed can be beneficial in helping to fill the cylinders because of inertia. The problem is that this only works at certain RPMs. Too small restricts the motor at high RPMs and too large has no effect at low RPMs. Someone needs to invent an intake that changes diameter as needed.

[620Turbo4X4]

Here is some picts of what I've done so far….

 

 

Here is what you end up with when the two half's are lined up with, and bolted to the head. About 3/8' too long and 1/2" too low on the front set. if you don't care so much about looks or performance, and just doing this for economy, it could be welded as is.

 

 

I did care. The easiest way I could see to fix was cut about a 3/8" slight wedge out of the first set of runners.

 

 

 

Lines up much better now.

 

 

Now that your have it cut open you have a good opportunity to open things up on the plenum side.

 

 

In addition to filling the holes where the EGR ports are, 1/2" of material was added to fill the dip in the runners where the EGR chamber used to be. (This might not have been necessary if I had used a non egr manifold??)    Sorry I don't have a before pict.

 

 

Has a much better "velocity stack" to the entrance or the runner now.

 

 

Then I  started hogging the ports out.. Being careful to remove material evenly all the way around the circumference or you will grind it too thin on one side, or worse, through it!! Long reach carbide burs and long nose die grinder is pretty much a necessity here. Be sure to revert to the L20b gasket when opening up the ports (the location of the 280z ports were way off). It is also helpful when opening up the runners to use something like a old exhaust valve to check diameter and out of round as to go so you don't grind too much in one spot. (I used various sized washers on a piece of all-thread)

 

Last 1 inch of runner is slightly undersized from 1-3/8" to leave room for "fine tuning" of the port matching once everything is welded together Aluminum expands and contracts a lot when welded. Even though it will be bolted to the head during welding, things will still move around on me...

 

 

 

Next step is to weld and fine tune the fit. To clean things up I'll use a fuel rail like the intake pictured below. Injector holes will be bored to 14.5mm for a "domestic" type injector and old stock type injector screw holes will be removed. They have remained in place only to ease the alignment until final welding is done. Fuel rail will be mounted with adapters to the bolt hole bosses I left on the top runners.

 

As you can see, I found making a decent intake out of a 280z manifold really isn't that easy (or quick I should say). There is probably a easier way? (maybe using the plenum,

and cutting it differently?) Don't know. I couldn't find any info on doing this either..

 

I think when all done, I'll have less time onto this L20b intake made from scratch...

 

[620Turbo4X4]

Hope everyone had a great thanksgiving!!!

 

After everyone left I had some time to finish welding the intake. Almost done!!!

 

 

[DaveZilla]

Wow that's a lot of work cutting down a 280zx manifold but it looks like you got it just about done... Very nice job for sure!!

I was going to recommend something like the fabricated one made from aluminum tubing in the last pic you posted.

[620Turbo4X4]

Wow that's a lot of work cutting down a 280zx manifold but it looks like you got it just about done... Very nice job for sure!!

I was going to recommend something like the fabricated one made from aluminum tubing in the last pic you posted.

The cutting and welding was pretty quick. It was all the port work that took forever.

 

The tubing intake took some time too. This will be for my turbo engine. I flared and tapered the runner tubing so there is a good velocity stack and a slight taper to the runners 1-5/8 to 1-1/2". Wished I had done a bit more research before I built the flanges. I didn't know that the EFI manifolds used just the one bolt on top. Could have got the injectors spraying on the tulips of the valves better with the bolts out of the way...