Installing plain TBs on twin-carb manifold

[Hezath]

Hi guys, I've picked up an N42 L28 that came with a british SU setup.

 

 

I actually want to put the SUs aside and set up some simple throttlebodies in their place - to run LPG. I'll fabricate up a plenum etc and eventually I'd like to turbo the car through that setup so I need throttlebodies that can deal with a bit of boost. Don't need a TPS or anything, preferably something nice and simple and not too expensive or hard to find a pair of (it could be off a carb'd or injected car with no problem at all), but obviously something very old where the throttleshafts have become loose isn't really suitable either.

 

Really like to hear people's ideas, don't mind if it's an OEM thing I could get from a car at a wrecker, new aftermarket part which is reasonably priced etc. Any advice is appreciated

Edited July 8, 2012 by Hezath

[Six_Shooter]

I thought about it as well, but decided to add the turbo sooner than originally planned, and went right to a port set-up using an N47 intake.

 

You could using single bbl TBs from mid to late '80s GM vehicles, most commonly found in FWD cars, and usually on 4 cyls.

 

If you really wanted to, and found a set cheap enough, the Crossfire set-up from the '82 and '83 F-body and '82 and '84 Corvette used two single BBL TBs.

 

While I haven't tried it personally, it has been said by a couple knowledgeable people on the subject that they can be mounted sideways, so mounting them to the SU intake should be pretty straight forward.

 

Another option, would be to use the more commonly available 2 BBL TBI from many GM vehicles, most commonly on '88 to '94 GM trucks. You would have to build some sort of plenum to mount the TB onto and then connect to the runners of the SU intake. The issue I see here is that 90* turn at the entry into each intake runner set.

 

As far as controlling the set-up goes, MegaSquirt could be used, or my favorite is to use GM (Delco ) ECMs in swaps, easy to come by, easily tunable, reliable, and inexpensive.

[randy 77zt]

Another member on here put 2 280zxt throttle bodies on a su manifold.I would like to try this manifold with 2 mikuni's from a harley

 

 

[Hezath]

Thanks for the input guys, with the LPG system that I'm planning on using, I won't need any ECU stuff at all haha.

 

In Australia, we don't really have any GM trucks or econoboxes (the only GM stuff is Holden Commodores or european things like Astras), but I guess I can start to scout out some wreckers with measurements and see what works off simply whatever I find.

 

Are the 280ZXT TB's hard to find? They are not the same TB as the L28E I take it? Do you know if the bolt pattern matches or anything like that?

 

I've had it suggested by someone else just then that Z32 300ZX TB's may be a good thing, and keep it in the family too. Anyone heard of people using them? Not sure what size or bolt pattern they have.

[Six_Shooter]

Sorry, I didn't notice that you were in Australia.

 

You might have some luck with ideas about some EFI components, from www.delcohacking.net, they are based in Australia, and know what parts come on what vehicles.

[19762802+2]

Somebody used some Mitsubishi 4g63 throttle bodies, I can't remember if they bolt straight up but they might, I know 280zx throttle bodies do not bolt up as I had a TB setup for a SU fuel injection manifold for a while, but you could weld the SU holes shut and drill and tap new holes pretty easily.

[Xnke]

To my knowledge, no, there are no stock throttle bodies that include a fuel injector that also match up to the stock SU carb manifold. I run a pair of 4G93 throttle bodies on my carb/FI manifold and I did have to weld the old holes shut and redrill the bolt pattern. The ZXT throttles are not hard to find if the ZXTs are not hard to find...but they are not the same bolt pattern either. You will need to enlist the services of a reasonably skilled TIG welder to fill the bolt holes properly. They are deep, threaded, dirty, narrow holes and it is a real pain to work down in the bottom of those holes.

[Tony D]

Z32 Bodies fit easily enough when you replace the stock phenolic spacers with a 25mm thick adapter plate allowing whatever bolt pattern you want to use, sharing as many common bolts as you wish.

Z32TB's have a nice centre linkage which can be shortened to retain synch feature and almost literally bolt right on (other then modifying the centre linkage for distance between T/B's)

 

But why stick on duals? Put a plenum on there of 1.5 X Engine Displacement, and a Mazda two-barrel throttle body (twin 45mm I think, and also a progressive option if you look...) would make plumbing that LPG system easier!

Edited July 8, 2012 by Tony D

[Hezath]

Yeah I could just go an open plenum with a throttlebody at the front but the twin TBs would just be so much 'nicer' I think, particularly while it's still N/A

 

I found a nice cheap pair of Z32 throttles that had already been bored out (almost 60mm) but I think they're just too damn big for the manifold. Shame

Edited July 9, 2012 by Hezath

[ozconnection]

Hey Heath!

 

You could try something like this?

 

Or this!

Edited July 9, 2012 by ozconnection

[Tony D]

Interesting 4bbl TB...

[Hezath]

haha that four barrels arrangement wouldn't really get me out of trouble. If I was just wanting to 'make something work that's easy' I'd go an EFI manifold with a single TB - I've already got the pipe that goes from the compressor outlet to the throttlebody lol! The thing is I don't think it really looks period in a H230.

[Six_Shooter]

Interesting 4bbl TB...

 

 

That's just an aftermarket 4 bbl TB, many companies produce them, such as F.A.S.T. and Holley.

 

Here's a real 4 BBL TBI...

 

 

This is on a friend's car, that I tune. This unit flows over 1100 CFM dry!

[ozconnection]

OMG, that's really ugly, but functional, I guess?

[Xnke]

That....is that what I think it is?

 

Did you cut one V8 and one V6 two-barrel rochester throttle body, match them up, and stick them together??? That is dedication to a product!

[Six_Shooter]

OMG, that's really ugly, but functional, I guess?

 

It looks less ugly sitting on the engine, the bench clutter doesn't help.

 

That....is that what I think it is?

 

Did you cut one V8 and one V6 two-barrel rochester throttle body, match them up, and stick them together??? That is dedication to a product!

 

Yep, basically. The rear bbls on this one are actually bored out 454 TBI, and the front were 5.7L IIRC. This is throttle body number 7 I believe, the first one that has the fueling feed layout that it does, the previous ones used a series system, where the feed went into the rear pod, out from there into the front pod, and from there out to return. The rear fuel pressure regulator was bypassed essentially, and used more of an accumulator than a regulator, the front regulator actually did the job of regulating the fuel pressure.

 

The new TB, uses an aftermarket regulator, and feeds fuel to each pod, through the 4 tubes, so 2 feed tubes for each pod.

 

It works well.

 

 

Sorry for the hyjack, back to the topic at hand of other throttle bodies.

 

So are you only looking for throttle bodies, as basically "air valves", no fuel or other control requirements? If that's the case, take a look at some of the Ford 4 cyl stuff. I know around here there was a 1.8L in the '90s Escort that had a small TB, with a 4 bolt pattern that may work.

 

In the end, I think you'll be making an adapter plate for whatever TB you decide to use. I guess another option would be to modify an SU carb, and get rid of all of the fuel stuff, using it as just an air valve.