SU carb engine with a L28

[Bruce Palmer]

Why did you feel the need to have the carbs massaged? Had you ever run fast enough to run out of carbs before? Just curious....

[blue 72]

Why did you feel the need to have the carbs massaged? Had you ever run fast enough to run out of carbs before? Just curious....

Because I knew that it couldn't hurt. I didn't want to open up the airflow potential of the cylinder head, have a higher lift and duration cam installed, port match the intake manifolds, run an electronic dizzy, etc... and have an area of the total combination that could potentially be improved but had been left alone (I didn't go crazy on my build, but I wanted a fun car though). I weighed the option of going with triple Webers/Mikunis/Canons vs. overbored SU's and liked the idea of stock appearance and a slightly lesser financial outlay.

I researched many similar setups, pored over much of the Z masters' leavings on the interwebs, and asked my head builder for recommendations. It was the conclusion that I came to for my particular combination of components.

Right now it is a street car with future potential. I haven't had it to a track yet (suspension is next), so in no scenario have I run out of carbs per say. It is still going to take some fine tuning and fiddling before I find the next area that can reasonably be improved upon. I like the car the way it is now though. 7k+ rpm sounds great.

I know ZTherapy has many years of experience building, customizing and generally fiddling with Skinners Union carburetors. I think I've read your opinions on the subject before and I don't want to sidetrack the thread too much, but what have been your observations of airflow potential through SU's with larger engine displacement requirements? Just out of curiosity.

Edited June 9, 2009 by blue 72

[240ZGL]

Hey, thanks for this write up, since I'm getting ready to do the same thing to my 73.

[myfairlady]

Thanks for the info. My engine is just a mild cam and pretty much thats it. Since im not going to be doing any autox or circut racing anymore I dont need to built up the carbs. Thats why I sold my tripple webers. I just want to enjoy the nostalgic feeling of my z now with better gas mileage.

Yes the sound of tripple carbs is pretty impressive but I like the sound of SU's as well.

Cool I have a 73 as well 240zgl

Edited June 10, 2009 by myfairlady

[Bruce Palmer]

Bottom line for this discusion from where we sit: 46mm Hitachis on a 2.8 motor is plenty of carb.... The several examples of 2.8 cars holding hillclimb records around here should point to the "enough carb" capabilities, especially if those looking to make the choice are running street cars. Two-eight motors in the heat of battle will use up more carb than a 2.8 on the street.

[myfairlady]

Well said... Ill keep you guys up to date when I put them on

[Jeff G 78]

I am turning on old, crusty '75 280Z I have into a 24 Hours of LeMons racer and I'm thinking of doing the same swap. The old FI system is likely going to require loads of diagnostic time and work since the car has been sitting for 17 years since it last fired. I have a '72 240 engine with SU's that also hasn't run in decades, but I figure SU's will still be simpler than FI for a LeMons race.

What is the best thing to do for a fuel pump? I'm thinking an electric pump will be easier than making a mechanical pump work with the N42 head. Is there a cheap electric pump that anybody recommends? Years ago, I ran a Holly red on a triple Weber car, but it was obnoxiously loud. Not that it matters for a LeMons car, but I'd rather not listen to it for 24 hours.

[Bruce Palmer]

Can't help ya on a pump pick, but do get yourself a bullet proof set up for controlling pressure out put. SUs wont take more than about 3 1/2 pounds of pressure before the needles and seats will be over powered and held open. At that point you can take the floats out of the float bowls 'cause theyza gonna fill up and runeth over.....

[Jeff G 78]

Thanks Bruce. I assume I want to run a return system?

[myfairlady]

Speaking of fuel pump. I notice I got one in the rear. Since im going back to SU set up do I need the rear electric fuel pump???

[beandip]

Jeff G, do run a return line. I have been running a RX-7 pump for 8 years now , from a '80 RX that was Carbed. Silent and supplies all the volume a triple will need on a stroker and will not over whelm a pair of SUs . At least I haven't found any trouble . There silent also.

Gary

[myfairlady]

Ok guys I got the carbs installed. the exhaust feels if you put your hand near the pipe . Its pushing hard and it gargles. Im trying to tune them but does anyone have any advice what I should do???