8 replies to this topic

[salamiman]

Hi All,

Running a relative new engine.

202 

Hsd 270hp 9 port

35803 crow solid

Triple HS6s with oa7 needes red springs 20w oil

X2 headers, 45 inch tuned length 1 7/8 primaries( I will do another post on this later of the road testing i did for this, interesting results), full exp chamber exhaust.

 

Installed an AFR meter, engine runs real well up to 5000rpm, but runs out of puff a little after this point, the AFR confirmed 11.2-11.5 after 4500rpm at WOT, so too rich.

 

Has the good head & free flowing exhaust made this rich condition at WOT?

 

I had 2 sets of oa7s, so i tuned down the idle section of the needle so i could lift the jet more to lean out WOT.

Initially I was at 12 flats out & went up to 6, Wot only changed to about 11.4-11.8 with 6 flats up.

 

Warren M metioned we should be around 12.5-13 for max power, so I'm way off ATM.

 

Have a set of oa8s as well, tried them without molesting, too lean for anything but WOT(11.8-12.2), might have to butcher/tune them.

 

Is it a needle issue or something else?

 

Any other thoughts appreciated.

Salami.

[warrenm]

 It's been a long time since I used HS6 carbs, I'll see how the memory is, I'll have a look at the notes later.. 

The setup sounds ok, I would use a thinner oil than 20w, ATF works ok.  

Edited by warrenm, Yesterday, 06:30 AM.

[salamiman]

 It's been a long time since I used HS6 carbs, I'll see how the memory is, I'll have a look at the notes later.. 

The setup sounds ok, I would use a thinner oil than 20w, ATF works ok.  

Thanks Warren, was thinking of taking the paper filters off & just using some fly screen, in case theres too much resistance in the filters, making the SUs suck more fuel, but Im also thinking of running 3 x HSRs, which may be easier to set up & be better in the end??

 

Pistons are fully open At WOT, just too much Fuel.

[warrenm]

My notes are a bit short on info, I changed from A07 to SW then KI, so these may help, I haven't found the SU chart to compare the difference yet.

[salamiman]

My notes are a bit short on info, I changed from A07 to SW then KI, so these may help, I haven't found the SU chart to compare the difference yet.

Checked Minty Lamb, looks like oa8 is still the leanest? Strange

[I'm a Red Motor fiend]

Same as Warren, I haven't run HS6's in a real long time.
Agree with running ATF.
You wont get an off the shelf needle that will give the correct AFR's across the rev range - persist with polishing them where required.
Whats your AFR doing at idle and cruise?
The OA7's sound like they're pretty close.
Try pulling the needle down very slightly out of the piston - it wont be an issue. May get your WOT very close, then polish mid and idle if they lean out too much.

[salamiman]

Same as Warren, I haven't run HS6's in a real long time.
Agree with running ATF.
You wont get an off the shelf needle that will give the correct AFR's across the rev range - persist with polishing them where required.
Whats your AFR doing at idle and cruise?
The OA7's sound like they're pretty close.
Try pulling the needle down very slightly out of the piston - it wont be an issue. May get your WOT very close, then polish mid and idle if they lean out too much.

Im With you Red, or lift the main jet up more, dont think ill get right it with the oa7s, but seeing i have a spare set ill basterdise them  some more 1st.

I have already taken about 5 thou from the top 3 stations on the oa7s & gone from 12 to 6 flats to get good idle, midrange good with only .2-.4 of improvement at WOT.(this doesn't seem linear), youd think it would have changed more?

Ill try a run this morn with some fly screen on the carbs to see if they like less restriction? & therfore draw less fuel.

[I'm a Red Motor fiend]

Yeah i generally only pull the needle down out of the piston if I've f*cked up and polished too much off and the jet is up near the bridge and cant be leaned out anymore that way.
Change to ATF before you do anymore testing or polishing.

[salamiman]

Yeah i generally only pull the needle down out of the piston if I've f*cked up and polished too much off and the jet is up near the bridge and cant be leaned out anymore that way.
Change to ATF before you do anymore testing or polishing.

copy that