Readjusting carbs

[fallingoffalot]

So after some fairly poor mpg and a new 4:1 JK exhaust, I got the carbs checked on a rolling road. They found the carbs to be set up OK he richened up the idle mixture a little on the left as he found cylinder 3 to be quite lean, which he said was common and did some other minor adjustments.

He also recommend getting some velocity tubes as this will flatten out the dip in the power.

The drive home felt more responsive and it pulled away better. I filled up again earlier after about 120 fairly fast motorway miles and found I'd got 21mpg. Better, I'm putting the 16.2 I got down to driving enthusiastically round the Cotswolds!

Not sure if vids can be embedded on here - here's a link you YouTube...
...
[youtube]https://youtu.be/D21JAqqsrhs[/youtube]

 

[Bluesnailman]

Interesting, where did you get this done, and any recommendations about finding someone that knows these old engines?

 

[mike202]

Says JPR Tuning in Yate on the printout. [emoji3]


Sent from my iPhone using Tapatalk Pro

 

[67panel]

No 3 has retarded ign timing built into dist to make it run cooler if I remember correctly.

 

[sparkywig]

Interesting, where did you get this done, and any recommendations about finding someone that knows these old engines?

I use JPR Tuning as well. John really knows his stuff.
Depends where you live, he's just North of Bristol so probably too far for you.

 

[sparkywig]

No 3 has retarded ign timing built into dist to make it run cooler if I remember correctly.

That's only relevant if you're running a stock distributor.

 

[67panel]

Yes just saying why no3 needs to run richer as a rule . Its a cooling thing !!!!

 

[K@rlos]

Velocity stacks or trumpets whatever you call them make a noticeable difference as they condition the air flow entering the carbs. Not really an issue for a mild engine like yours but really high end race car tuners will go through multiple trumpets with various different shapes and profiles in order to optimise an engines power band squeeze every last little bit of Hp and rpm out of it.

 

[fallingoffalot]

Velocity stacks or trumpets whatever you call them make a noticeable difference as they condition the air flow entering the carbs. Not really an issue for a mild engine like yours but really high end race car tuners will go through multiple trumpets with various different shapes and profiles in order to optimise an engines power band squeeze every last little bit of Hp and rpm out of it.

I definitely notice a difference since fitting them, the engine pulls from lower down and accelerates more uniformly through the rev-range. I'm going back to JPR when I get a chance to see the actual difference they make. Before fitting them I used to change up to 4th at about 40mph, below this it would feel like it was labouring (I have a 'freeway flyer' box, so taller 3rd/4th) now I can easily change up to 4th at 30mph and it pulls normally.

 

[K@rlos]

Velocity stacks or trumpets whatever you call them make a noticeable difference as they condition the air flow entering the carbs. Not really an issue for a mild engine like yours but really high end race car tuners will go through multiple trumpets with various different shapes and profiles in order to optimise an engines power band squeeze every last little bit of Hp and rpm out of it.

I definitely notice a difference since fitting them, the engine pulls from lower down and accelerates more uniformly through the rev-range. I'm going back to JPR when I get a chance to see the actual difference they make. Before fitting them I used to change up to 4th at about 40mph, below this it would feel like it was labouring (I have a 'freeway flyer' box, so taller 3rd/4th) now I can easily change up to 4th at 30mph and it pulls normally.

The air flow is being directed straight down the carb, rather than scavenging the air and it slowing it down when making the 90 degree turn down into the carb. Air speed and port velocity is critical for torque, the torque has clearly increased if you’re noticing more ooomph like that.