Engine tune-up data

[Sam_C]

The 240 is running a bit doggy at the moment, so I have decided that a tune-up is in order. However, it is quite difficult to find UK-specific data on 't Interweb so I might need a bit of help please gents.

So it's a 73 240, round top SU's and as far as I know standard everything else. I THINK that the following settings should be correct -

Points gap 18 thou
Plugs 31 - 35 thou
Timing 34 btdc @ 3,000 RPM dynamic Static ????
Mixture nuts set initially to two full turns down from being fully screwed up

Does that all sound right?

Cheers Sam

 

[jonbills]

That's about right for timing & plug gap. I don't remember the points gap or the mixture settings.

 

[richiep]

Point gap according to Haynes manual is 18-22 thou.

 

[SacCyclone]

Remember to check that the main fuel jets on those SU's are closing all the way after the choke has been set. The engine will run rough if they are sticking (very rich)

To check, simply make sure that the chokes are off... then press up on the bottom of each SU carb on the main jet. Make sure they are not sticking. If you are able to push up and move the mains, then you have a slight problem.

 

[Mr.F]

Carbs balanced for air flow of course...?
Check needles installed properly - often see them pushed fully home in seat - needle collar should be level with bottom of the piston, not bottom of the groove, so a little edge of collar is visible. You can stick a finger in and feel for this without dismantling.

 

[Sam_C]

Thank you gents, some interesting and useful extra info there.
Out of interest, is there a engine tuning guide anywhere on the site? I had a look around but couldn't find anything.

 

[jonbills]

I think this thread is it.

 

[Sam_C]

I think this thread is it.

Not a lot to show for 46 years of experience then!
Hopefully we can pad it out a bit between us. How about this...why is the points gap a range and not a single value?

 

[Sam_C]

And here's a photo to demonstrate Mike's point about needle height

 

[Mr.F]

That doesn't look like our UK pistons which have a machined groove across the bottom...?

 

[Sam_C]

That's correct Mike, I think they are MG fitment. I posted the pic as I thought it demonstrated your point about leaving a little needle collar sticking out level with the piston face. Unless I got the wrong end of the stick of course?? ( happens a lot, ask my missus)

 

[Jimbo]

And here's a photo to demonstrate Mike's point about needle height

thats a brittish su carb with floating needles instead of fixed and the reason i had to find alternate needes to sm because they wont work in this style of carb.
good idea thought as it means the needles wont bind against the jets

 

[Mr.F]

I'll try to find a pic or diagram to illustrate the 240Z variant.

 

[Sam_C]

I'll try to find a pic or diagram to illustrate the 240Z variant.

Cheers Mike. I did think that was an MG unit, but it seems it was from a Mini, the bevelled edge being one of David Vizard's mods.