EFI to carb conversion?

us2 · Post by **us2** » Mon Apr 02, 2012 10:05 am

ZMAD wrote:The panels for sale by that trader are interesting and here in Tauranga too.

Quite rare I would think, and not a bad price for new panels .

The US 280 with round top SUs. It will go very well for street use, and still retain the seventies look.

All depends on the depth of ones pockets, if you want to fit triples.

Pedey · Post by **Pedey** » Mon Apr 02, 2012 11:50 am

I'll give them a miss in that case. I would like to fit some triples but realistically I have no huge need for them and they would most likely end up being more of a hassle than they are worth, I just want the car to drive well, be reliable and have that old school carbed feel. At the moment, I think the EFI system is holding the car back dramatically in terms of power and reliability, that said it does run ok so I'm in no massive hurry. If anyone does happen upon some round tops with manifold etc, I'd be interested.

mike260z · Post by **mike260z** » Mon Apr 02, 2012 12:53 pm

Pedey wrote:I'll give them a miss in that case. I would like to fit some triples but realistically I have no huge need for them and they would most likely end up being more of a hassle than they are worth, I just want the car to drive well, be reliable and have that old school carbed feel. At the moment, I think the EFI system is holding the car back dramatically in terms of power and reliability, that said it does run ok so I'm in no massive hurry. If anyone does happen upon some round tops with manifold etc, I'd be interested.

Well Triples are fine if they are set up right and you get the right person to tune them. They would be fine on the L28 , now your EFI is going to be more reliable than a carb set up - or all cars would still be carbed. So really you just want the carb engine note? The emissions gear on the engine might be choking it up a bit if its still on there. I have triples on my car and i used to daily drive mine on the 35km round trip to work and back five days a week and she ran fine. IMHO if you want to carb it do it right with a nice new set of carbs and a decent tune.

Pedey · Post by **Pedey** » Mon Apr 02, 2012 3:11 pm

It was my understanding that triples tended to need constant tweaking, unlike the SUs which are more of a set and forget type of thing?

- My EFI is certainly not what I would call reliable and I'd much prefer trusting a simple carb over a 37 year old computer.

- Yes, the sound would be nice too, plus it really feels wrong to me that the S30 is injected, but maybe that's just me.

Regardless, yes the triples would be nice and I would probably go in that direction if I could justify the cost/get something cheap enough.

Grunzter · Post by **Grunzter** » Mon Apr 02, 2012 3:16 pm

Fuel injection can also look cool on a L series zed!

http://www.efihardware.com/products/c56 ... -Body-Kits

...you just may need to sell some body parts to pay for it...

nzeder · Post by **nzeder** » Mon Apr 02, 2012 10:57 pm

well I have a set that I could sell, new never had petrol in them, 50/48/45mm Pro race versions

disruptiv · Post by **disruptiv** » Tue Apr 03, 2012 7:07 am

what kind of TB to you have?

ZMAD · Post by **ZMAD** » Tue Apr 03, 2012 8:03 am

2 inch SU's off a Jaguar bolt on and work really well once tuned.

us2 · Post by **us2** » Tue Apr 03, 2012 8:20 am

Do they bolt straight on the 240 manifold Jason?

mike260z · Post by **mike260z** » Tue Apr 03, 2012 8:41 am

I did a quick search and it appears to be a common swap overseas to fit the 2inch Jag SU carbs to S30s. I cant find anything on if the manifold needs to be modded.

ZMAD · Post by **ZMAD** » Wed Apr 04, 2012 8:31 am

No mods to manifold as far as I can tell. May be the manifold was port matched with carb, unsure. I have these with carbon fibre trumpets and piper cross filter. They work bloody well. I'm still doing my tripple Dellorto conversion and if I never get that going well will convert back.

Baker93 · Post by **Baker93** » Wed Apr 04, 2012 11:22 am

I will try and keep this as simple as possible. I may be the only person or one of a very small group who has run every kind of carburetor being discussed here on an L28. Firstly I need to settle a myth. Triple carburetors do not need constant attention and retuning. Quite the opposite! No carburetor on a healthy well set up engine should require constant fiddling unless the atmospheric conditions change dramatically.
Set up is the key here on any carburetor. Good linkages and adjustments along with the carburetor and entire fuel system being in top condition. The extra maintenance required on SU type carburetor is vacuum lines and manifold leaks. These can be the prime causes of erratic operation in cars equipped with SU carburetors.
Linkages on one carburetor easy, two carburetors a bit more difficult three carburetors more difficult again. Imagine doing a V12 with 6 x dual down drafts. By the way this is all the same for a fuel injected car running individual or twin throttle bodies!
Now for the Carburetor types. Others may have different experiences (feel free to voice these) but these are mine. These comments all relate to use on an L28 with comp ratio around 9.5 - 10 to one any other modifications will be noted.

Flat Top Datsun Hitachi SU style.
I wouldn’t waste my time.

Round Top Datsun Hitachi SU style
Good for road car with very limited modifications and I mean limited! A set of extractors an exhaust and maybe a very mild cam. ( I will expand on this soon )

2 inch SU Carburetor
If my memory serves me correctly they are an HS6 model and were available on Jags, Astons, Rolls, Rovers some tanks, trucks, boats, planes, ships and other biggish 6 cylinder pieces of English engineering works of art !
Work better than the Datsun carburetor but still limited in tuning potential. Will fit on the Datsun manifold obviously with port matching required. Lots of different needles were available (20 yrs ago) to tune the mixture but these were expensive and required a lot of time and patience. Ultimately not worth the hassle. I spent more money messing around with these than my triple carburetors cost!

Triple Carburetors.
The three most common types used on L Series motors Mikuni, Weber and Dellorto. (there are numerous others). I will stick my neck out here and say stick with Mikuni and Weber. That is going to set people off but my suggestion is based purely on the availability of parts, the fact that they are more commonly used and that I have a set of each in service.
The triple carburetor is really the ultimate cost effective induction set up for a Zed if you wish to keep carburetors and plan any modifications to the motor or are performance orientated ( I assume so).
This is most easily proven by answering the following question.
Which carburetor set up is going to give the most even consistent and tunable supply of fuel to each cylinder. Just look at them!
Now as I mentioned earlier Re SU carburetors and cams. Very basically SU carburetors need vacuum to work. Modified cams reduce and can pulse the manifold vacuum/pressure at low RPM. The dash or damper pot of SU style carburetors tends to start to wander up and down causing a lumpy idle.
Despite common belief modified motors especially street motors don’t have to have a lumpy idle. This comes back to set up!

My suggestion.
Street/mild performance use (its still very good) buy a set of 40mm Webers. There are a lot available and relatively cheap. Dual purpose street performance and club race/race car. Get a set of 44 Mikunis or Webers (these can be used on a street car appropriately set up)

What would I do!
Ditch the Carburetors and install triple twin DCOE style throttle bodies c/w programmable injection and ignition.

What ever you decide Good Luck

Anthony

Pedey · Post by **Pedey** » Wed Apr 04, 2012 4:41 pm

Thanks for your help Anthony,

That clears a few things up for me, so it's very much appreciated. Although my knowledge of this particular motor is fairly vague I know it has quite an aggressive cam and head work. I chucked it on the dyno recently to make sure it was running safe, which is was (lean between 2 and 3g, which explains the awkward stutter, but nothing horrible) but it made a grand total of 100hp at the wheels. That doesn't seem so hot to me...

Thanks to everyone for the input

Baker93 · Post by **Baker93** » Wed Apr 04, 2012 5:44 pm

Thats not a lot of horse power ! I would have thought around maybe 140 would be more like it. My wife asked if its an L20 ! Sorry ! She had the same motor in a 280ZX coupe and it made about the 140 mark from memory.
Just as an indication my stock 2.8Ltr motors low comp (9.0 to 1), home ported head, standard valves, mild cam, extractors, exhaust and 2inch SU carbs street driven (my only car at the time) made 151 at wheels.
Same motor different cam (because the carbs allowed it), triple 45mm Webers still street driven made 183 at wheels.
Same motor (10.0 to 1) comp different cam (because i thought bigger is better), triple 50mm Webers (that bigger is better thing again) 216 at wheels.
Same motor again flash head (would cost around $5000 to replicate) bigger cam same everything else. Result = less power 180HP WTF !!
Thats where things went a bit pear shaped !
Current motor is same as one above 3.0Ltr (a Bit Bigger) high comp, standard valves, similar cam, smaller intake manifold, smaller carbs and chokes the usual careful set up. Result 280 at the wheels !
Street driven L28 on triple carbs well set up can make up to 200 RWHP easily.
If you want to know more on this subject feel free to call me 09 410 2929

Cheers Anthony