201.6rwhp on Hitachi SUs

[neuby]

Hi all,

 

I hope I've posted this in the correct location.  While not Skyline specific this is L series motor specific and I thought it worth sharing.  My long term home built and home tuned L28 stroker put down 201.6rwhp on the standard 48mm Hitachi SUs from a '71 240Z.  

 

The set up could probably make a bit more power if time was spent further ironing out the needles and playing with the programmable ignition.  It's not crazy power but I think it shows that the old Hitachi's in combination with everything else can be underrated.

 

 

[neuby]

 

[neuby]

A bit more about the build.

 

[GTSBoy]

Nice.

I don't think anyone who knows what's what would ever argue that carbies don't make power. It's not as though it's difficult to get the mixtures right at peak power. Getting the mixtures right everywhere is the challenge, along with all the other niceties like idle, accel pumps, etc.

Carbs + programmable ignition is no bad thing at all.

[blk180]

That’s some decent power for sure, Do SU’s have idle and main jets or just one set? 
 

my stoker with triples is sitting around the 290rwhp on 98 but am having some tuning issues with getting the rest out of it. 

[neuby]

SU have a single needle of various taper. Only one part per carb.

 

I had run 45DCOE152s with 36mm chokes maybe ten years ago. Felt faster than the Hitachi SUs but I couldn’t tune out a lean patch And stutter (20:1 AFR) between the idle and main circuit. I was getting to the point really strange combinations of idle, main, emulsion tube and air correctors that started to impact the rest of the Tune.

Edited May 31, 2020 by neuby

[mickey]

Hello all, sorry to bring up the dead thread.

I've been considering an engine swap or what to do with the L20A with dual SU's in my hako, any idea if it's worth getting the L20A optimised with the SU's and what sort of power it can muster, or should I just L28 it or the like?

[GTSBoy]

What do you mean by "optimised"? Are you talking about just getting the carbies set up and tuned nicely, or are you talking about a high comp rebuild with porting and a cam?

The thing to remember is that the L20 is a very small NA 6 cylinder that can't muster a lot of torque. if you work it, you will be able to make a nice bit of extra power, but it will all be up high in the rev range and there will be even less torque down low (because of fat cam lower gas velocities through bigger ports). If you want to make a screamer, then yeah, work it, put a good set of pipes on it, tune it up, etc. But if you want to make a nice street engine then more capacity will always be the first option.

If your question is just about choosing between just tuning the carbies up or going for a bigger motor (which is not a very sensible question) then...... it will clearly cost a lot less to get the carbies done, and the result will be much nicer, but not in any way comparable to an upsized engine.