paddy351

just wondering what is a good afr, no to lean- for a worked 351 clevo

xdclevo

12.6 would be good.

TruBlu351

........at full power

14.7:1 when cruising. But I'm at full power 90% of the time anyway

Are you running an AFR meter or just getting it onto the dyno?

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XE Falcon
393 Tremec TKO 9"

paddy351

i have had it on a dyno and it was around 11.3 11.6 it runs a 750dp with 71s and 80s, My engine builder said that was rich but safe .It made 194kw at wheels and 594nm. We don't have drag strip in Adelaide so the car cruises alot. Will i make much power by going to 12-13 afr and will a hot summers day cause it to lean out to much.

TruBlu351

Same power as my old 351

Yeah, it's safe.....it would make a few more HP.....hard to say as it's different for each setup. I don't think you'd feel it much in the seat of your pants though.

WRT hot days, the air is less dense (expands and is thinner), so if it will actually go more rich. A cold night has thicker, denser air, so this is where an engine could lean out. This is why engines make crap power on hot days.

Hot temp, smaller jets. Cold temp, bigger jets

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XE Falcon
393 Tremec TKO 9"

paddy351

thanks trueblue for explaining that, what 1/4 times did your old setup run

TruBlu351

It did 13.8 with street tyres. With 4.11's and the manual it would light up off the line with 2.2 granny 60 footers. It would run out of revs about 4 seconds from the line....only going to 5000 with stock valve gear

If I'd had slicks and maybe 3.8 gears, I think it would have dropped half a second or so. So it had potential for a low 13.

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XE Falcon
393 Tremec TKO 9"

xdclevo

My last 351 had 75 and 83 jets and was 13.5:1 afr with about 240 rwkw.
And with same carby and 77/85 jets in my new 408 stroker, and it has 12.9 afr with 300+ rwkw.
I think you would pick up power going to 12.6 or 12.8:1 afr and still be really safe. (at WOT of corse)

paddy351

thanks xdclevo, my motor makes good torque at 594nm and my engine builder said thats what counts in big car, it just the hp thats a bit low for a solid 2v engine.

cjperformance

11.3/11.6 is safe for avoiding detonation but will shorten bore/ piston ring life. mid 12's are safe and you will make more power/torque. torque is important (it tells you what your engine can do) the power hp/kw mainly tells you how quickly your engine can apply the torque. lean it off a bit at a time, constantly checking plugs( after full power runs) and fiddling with advance curve.you will gain some performance by doing this. it all depends on engine combo. the same carb/jet combo will provide different fuel mixtures on different engine combos( manifolds, cam and exhaust have the main effect on the carb) always make one small change at a time and record what you do for future reference. cheers

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Craig Johnston.
Ford, Performance & Vintage engine specialist.
email- cjperformance@lizzy.com.au