5 replies to this topic

[mgfreak79]

Hi, so close to getting her back on the road again just need very fine tuning now!!

i have a 998 cc with a cooper head, high lift rockers and a extractor exhaust fitted i have a aaa su needle in my 1" 1/5 carb

having read in david visards book he suggests that i need a e3 needle with a blue spring. however having looked on the mini sport site the e3 needle is a fixed needle as oppose to a spring type needle which mine is

what spring do i need mine is the spring needle atm can you change it by just replacing the needle and ditching the spring and plastic collor??

it drives well atm its alittle flat in third and fouth at about 50 hence my reason for changing and the cooper head and rockers i assume i need a richer needle

helpp!!

many thanks Pete

[bmcecosse]

Which 'Cooper' head is it ? Did you have it skimmed to get the compression ratio right ? The problem could also be the 'high lift rockers'. But an AAA needle should be fine - just set it up correctly.

[jaydee]

E3 with blue spring is for twin Hs2 isnt it?
And by the way AAA is richer than E3, i'd try AAM needle and Red spring with your spec, blue spring will probably be too light, leaning off mixture, but you can even try either to test which one goes better.

Edited by jaydee, 20 January 2010 - 10:54 AM.

[mgfreak79]

Thankyou for the replys

Its a cooper 12g295 head the rockers i have is equivelent to going up a cam size from standard.

From what i can gather the aaa is a needle with a spring where as the e3 is a fixed type.

I did not have the head skimmed just wet and dry to make it relatively clean.




my next problem and bigger one is the timing, from what i can gather it should be running at around 8 deg tdc. When i set the timing to this it miss fires, however when i turn the distributor clockwise to about 20 deg before tdc it runs well but it's just flat in third and fourth at around 50 onwards.

Somebody said this can be down to low compression, so the timing very retarded


does anyone have any ideas, as i do not really want to take the head off again to skim it


thatnkyou very much. im amazed at how friendly and knowledgable people are on this forum.

[jaydee]

If you're not sure about CR, best thing you can do is take cylinder head off and measure chamber size using some parafin, it should about 25cc to work fine on a standard 998cc lump.

Edited by jaydee, 20 January 2010 - 06:05 PM.

[bmcecosse]

If you didn't have the head skimmed (and it wasn't skimmed before) - then the CR will be very low and performance will suffer. You may be able to check the head thickness without taking it off - there should be a little ledge that overhangs the block slightly. Standard head is 2.750" thick - if yours is any less - then that's what has been skimmed off. It should ideally have 60 thou off if using flat-top pistons - and 80/100 thou off if using dished pistons . BUT - do check if it's safe to go to 100 - otherwise stop at 80 - which is always safe!!
AAA is the needle to use - although I hate the high lift rockers!