TBI 305 Tuning

[TerryD]

I replaced the intake on my Camaro with the Edelbrock Performer TBI piece, rebuilt the throttle body with new injectors, injector pod spacer, JET adjustable fuel pressure regulator, ground off the air horns and installed a NOS GM distributor.

My timing hopping around at idle with the timing connector unhooked is gone, it starts and idles pretty nice now and runs good. I have lost some off-idle power which I've read is a common thing with this intake. I'll eventually regear and put in a more aggressive converter so for now, I'll live with it.

My issue is fueling. I was watching the live stream and looking at my BLMs. They should be around 128 counts for stoichiometric but it is running in the 105-112 range pretty well across the board. No big deal. I've probably got the fuel pressure set too high. So I started lowering the pressure and with it so low the car stumbles and is noticeably down on power, my BLMs are still the same. I turned it back up till the stumble was gone and have been driving it some to let it settle in more.

So now I'm curious if that's a common range for the BLM to be in on a fairly stock 305. That's around 12-15% fueling being pulled by the ECM.

 

[GWeakland620]

Interesting. My buddy just snagged an Edelbrock tbi intake at a swap meet on Saturday, and I snagged this Holley tbi intake too.



I’ll be following along for whatever information comes along.

 

[dyeager535]

So now I'm curious if that's a common range for the BLM to be in on a fairly stock 305. That's around 12-15% fueling being pulled by the ECM.

To get the BLM's back in line you'll need to tune. Then go after timing once fueling gets a little closer to normal.

Fuel pressure adjustment should help, but as you change fuel pressure you may see knock retard start kicking in if timing requirements have been affected. Those 305's were always on the ragged edge of detonation. That's why the 305 started with a knock sensor circuit even while carbureted.

Problem with fuel pressure is that it is a "global" change, and that can/will affect open loop operation where the ECM isn't using the O2 to account for too much or too little fuel.

At this stage I'm not sure if moates.net is still around, but last I checked EBL is. If sticking with the factory system, really the only two DIY options that have existed for the last couple decades I'm aware of. There are or were a few tuners online (you send them your specs, maybe datalog, they send you a custom PROM). One was pretty highly recommended, but I can't recall who that was.

 

[TerryD]

To get the BLM's back in line you'll need to tune. Then go after timing once fueling gets a little closer to normal.

Fuel pressure adjustment should help, but as you change fuel pressure you may see knock retard start kicking in if timing requirements have been affected. Those 305's were always on the ragged edge of detonation. That's why the 305 started with a knock sensor circuit even while carbureted.

Problem with fuel pressure is that it is a "global" change, and that can/will affect open loop operation where the ECM isn't using the O2 to account for too much or too little fuel.

At this stage I'm not sure if moates.net is still around, but last I checked EBL is. If sticking with the factory system, really the only two DIY options that have existed for the last couple decades I'm aware of. There are or were a few tuners online (you send them your specs, maybe datalog, they send you a custom PROM). One was pretty highly recommended, but I can't recall who that was.

Moates is around and EBL is in the process of changing hands after the death of the founder.

I'm going to contact Moates and look into the '427 ECM swap soon. Starting with AIR intact then probably switching to a NON-AIR tune and modern catalytic converter when I do headers and a full exhaust.

 

[dyeager535]

Moates is around and EBL is in the process of changing hands after the death of the founder.

I'm going to contact Moates and look into the '427 ECM swap soon. Starting with AIR intact then probably switching to a NON-AIR tune and modern catalytic converter when I do headers and a full exhaust.

Yeah read that about the EBL situation, that's unfortunate. Hopefully they get back to normal quickly.

I forgot about megasquirt and did I read there is a microsquirt as well? Options are usually good.