Fast355

iTrader: (2)

Well my engine is in and it is now time for tuning.

ANYONE that has a similarly modified 305 bin file for a car ECM is welcome to chime in. I have experience with the 747 but not the car ecm. I am converting to the car ecm simply because it seems like it is somewhat better than the 747.

The engine runs well on stock tune but needs more fuel up top.

Here are the specs:
1983 G20 305 block bored .040" for 312 CID, Flattop pistons w/4 valve reliefs, balanced rotating assembly, forged crank, X-rods, 081 TPI heads, stock replacement 1983 305 HO camshaft, flowtech long tube headers, duals, stock 350 Van TBI and TBI intake, 14 psi fuel pressure, 305 injectors, 4* timing advance. Backed to a 700r4 w/ 2,000 stall and 3.08 gears (reason the cam is so mild).

Any guesses on power?

ShiftyCapone

iTrader: (7)

I would say 200 to 210. Maybe a few more.

Fast355

iTrader: (2)

My guess was about 220-230 at the crank, but I just wanted a second opinon. It is basically like a 1985 TPI 305 but has 081s instead of 416s and is minus the TPI. It does have the headers though with a free flowing exhaust and a free flowing G-series air cleaner and snorkel.

ShiftyCapone

iTrader: (7)

I'd buy that. I would say that is a safe guess. Should be a fun ride.

Fast355

iTrader: (2)

Plugged the numbers into desktop dyno at school and got the following. I know DD2000 tends to give a little more HP than an engine really has but here are the numbers. 210-230 is a realistic guess depending upon the tune.

RPM-------HP---------TQ
2000-----128--------336
2500-----160--------337
3000-----192--------337
3500-----221--------331
4000-----237--------311
4500-----238--------278
5000-----225--------236
5500-----203--------194

One day it will get ported pro-topline vortecs and a little hotter cam, but that is in the distant future. It will always be TBI though.

Fast355

iTrader: (2)

I am getting 15 mpg city, 21 highway and 18 combined

Fast355

iTrader: (2)

This engine combo is making me pull my hair. It runs great at part throttle and gets good mileage, but @ WOT it is cutting out real bad. I am trying to find out where I am going wrong. I nailed the 355 calibration pretty easily but this 305 calibration is driving me crazy. It runs about 5x better with 350 injectors and the 350 prom. So good in fact I am tempted to just leave it and tweak off the 350 ECM.

I take it nobody has a modified 305 bin for the 8746 or the 7747 so that I can compare it against the one I am working with?

BMmonteSS

I had similiar problems when I first started tuning WOT on my 355. Ended up I was running the injectors static. Felt like I was hitting a brick wall up top. I got my PW to spit out the aldl and sure enough I was maxing out at the exact RPM I was getting the stutter/miss.

Do a search under my name, it was a while back.

Fast355

iTrader: (2)

Thanks BMmonteSS. I was thinking that I was just running out of injector. The 305 ones wouldn't cut it at even 17 psi. The 350 ones seem marginal even at 13 psi. I guess I am making more power out of this combo than I thought.

BMmonteSS

You can just crank up the fuel and reduce your VE's and see if the stutter moves up in the power band, if it does then your on the right track, if not then it could be something else.

Your 312 might not being needing any more fuel than the 350, it's probably just needing the fuel at a higher RPM which gets you in trouble with running out of PW.

https://www.thirdgen.org/techbb2/sho...ghlight=static

here's a link to that thread I was talking about. Rbob tells how to get your PW to come out your aldl in the prom ID slot. This could save you alot of time. I've been meaning to throw that particular bin back in and see what happens on the WB when the injectors go static. I know the engine acted like some one just yanked 6 plug wires.

Fast355

iTrader: (2)

Thing is still ticking me off. I was running 350 injectors at 17 psi and still it bogs lean on tip-in when in closed loop. My narrow and wide band O2 sensors go dead lean, the engine falls on its face, and sometimes even backfires. I have played with the BPWC, fuel pressure, timing (table), and VE tables yet still nothing.

RednGold86Z

iTrader: (1)

Have you tuned Acceleration Enrichment yet?

Are you watching fuel pressure during the problem? Should stay rock solid on a TBI setup (no vacuum reference).

Fast355

iTrader: (2)

Found out what was causing it. Strange that it was causing a bad lean stumble but the distributer clamp bolt had loosened and the timing was at 3* ATDC. I reset the timing back to the 6* I started with and it is running much better now.