Hey everyone I just put a set of 89 GTA heads on my 350 which originally had 305 heads on them. I have a bunch of bolt-ons from 52mm throttle body ported plenum, SLP runners, edelbrock intake ford 24lb injectors, full exhaust and all that. The difference from 305 head to 350 head doesn't feel that great, so i'm wondering what i should adjust the fuel pressure at. I believe with the vacuum disconnected the pressure is like between 35 and 40. Maybe like 37 and timing is set to 10 degrees. I was wondering whats a good fuel number and even a good timing mark, Thank You

 

You should bump up the fuel pressure to 47 psi to start. Then go up 2 psi until performance suffers then back down 4 psi. Initial timing is dependent on the octane tolerance of your car. I set mine at 8 BTDC with a Hypertech II chip.

 

i wouldnt bump up the pressure, you have bigger injectors so you might need to lower your fp.. you might be overkilling it right now with fuel..
as for timing, advance it until you get knock, then back off...

 

Well, I'm not sure about that.

If stock 350 heads are still being used, then the change to 24# SVO injectors should not have been done. On the Ford system (37psi) they flow 24#/hr, however on the GM system (43psi) they flow 25 to 26#/hr. The stock GM injectors flow 22#/hr at 43psi.

I would recommend that you start at where you are now at 38psi and work up from there. Even at 38psi, you may be rich at WOT. You should get a scanner and check what the O2 sensor is putting out during WOT runs. Try to dial in about 860mV from the O2 sensor by changing the fuel pressure.

I have proven on the chassis dyno and a A/F ratio meter along with my scanner, that at 860mV from the O2 sensor, the engine had a A/F ratio of 13.3 and put out the max Hp.



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'87 L98 TPI IROCZ, AFR190 heads, 3.70 gears, ZZ9 cam, 3000 Art Carr TC, SLP 1 3/4" headers, SLP cat-back, no cat, no AC, no MAF screens, Accel manifold base & SuperRam, 24#/hr SVO injectors, Edelbrock double roller timing chain, MSD ext coil & distributor, trans cooler, 52mm TB with airfoil, TB coolant bypass, AFPR(40psi), K&N filters, Hotchkis lowering springs, my custom chip, Lay Ind. ram air kit, SS Brakes 1LE upgrade 12" rotors dual piston calipers, 265/45R16 Kumho V700 tires.
ET 13.27sec @ 103mph on MT ET Streets
'90 Eagle Talon AWD, no rust thru 9 winters
'99 Camaro SS, red, 6-spd, T-tops, Mcleod clutch, Pro 5.0 shifter, MAF processor, Direct Flow airlid, K&N filter, next mod: 4.10 rear gears
313.7Hp & 320.6ft-lbf, ET 13.55sec @ 105.1mph

 

The increase in pressure allows for better fuel atomization and gets you more power and better economy. If you are running low pressure and get too rich bumping it up then you need a new PROM to allow for a higher fuel pressure.