Hi there- so I got my car back today, having swapped the 305 for a 350 engine. It seems to have LOST power in the course of the swap, much to my dismay. Other members are suggesting that it is quite likely the chip, which I'm interested in programming myself, the only problem is that all the 350's referenced here: http://www.osterlen.com/alf/cam-data.htm#ThirdGen
have TPI rather than throttle body. To me that means that there is no program that is optomized to efficently opperate a 350 engine using a throttle body system. If the problem IS in fact the chip- will I have my work cut out for me in splicing tbi information into the 350 program- is this even possible? thanks for any help!!
-Kevin

 

Kevin,

I don't have experience with TBI but there are those here that do. Maybe they will jump in and give some advice. However, I can tell you that I have seen plenty of 350TBI guys running nicely. It may or may NOT be a chip problem ... keep that in mind as you try to discover and tackle your problem.

Tim

------------------
TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

You indeed have a chip "problem" if you are running the 305 chip on the 350. It is calibrated for the smaller motor and generically will pump out less fuel. The ECU will correct some of the problem, but not enough. To help without a PROM change, you will have to up the pressure on your fuel pressure regulaor, which you can find help on this site in Tech Articles, I believe. You'll have to bump the FP up about 30% to compensate for the 14.7% change in displacement. ie, 11psi up to about 14-14.5psi. Also, I would advance the initial timing of the distributor until you see knock counds on a scan tool, then back off a degree or two until they just stop.

This is band-aid work and will help a lot but not totally. if you are NOT running EGR on the motor, you surely need PROM work, BTW. If you are running ALL the OEM TBI stuf, you'll be ok UNLESS your cam/heads/exhaust are ALL hopped-up, even a little. FYI, the timing curve on the OEM TBI chips is VERY anemic and an use a LOT more advance.

 

Let's hope I can get some help here- but like I said, it does run okay, which I find pretty strange if the chip isn't right- strange that it could be the wrong chip, and yet be close enough to run the car fairly normally. How do people with carbs program their chips? I don't think any recent 350's had carbs on them either. What else could be wrong?

 

I'm just going to reiterate whats already been said. First check your base timing, then give it some more fuel pressure to help compensate. You will need a custom chip to fully optimise the combo. Make sure everything from the install got done properly.

Can you give us some more specifics on your combo? What heads, cam and intake are you using?

------------------
1988 T/A,
9" Ford, 3.50 gears, Auburn posi, 700r4 -w- 2100 converter
350 .060 over with forged 1 pc rms crank, and forged TRW pistons, 9.5:1 cr
Factory GM heads Pocket ported, 2.02/1.60 valves, back cut
Lunati roller 219/227, .479/.480, 112 LSA
Holley 700cfm 4bbl on TBI truck 7747 computer and chip by Howell-EFI
Edelbrock Performer EGR intake, Edelbrock TES and 3" cat

 

I was just going to order a blank prom to work with, but in reading Traxion's "Prom Burning Introduction" article, I couldn't figure out just which chip to order since I don't have enough engine info- also, (as I'd mentioned) from what I've seen, a 350 is by nature a TPI, and yet, mine's running TBI. according to the chart, I probably have a ECM type C3 (TBI engine, but the program I want it to run is for a 350 (tpi) engine). I don't know if I have a MAF sensor or speed density in the car. Can someone tell me which chip I should order to start out with? thanks!
-K

 

Kevin, looks like you are a ways behind the power curve but lets see if we cant get you caught up.

First thing I need to know is exactly what vehicle you have. I also need to know specifics about your new motor. Is it a crate motor? Stock replacement? Some sort of performance motor?

 

why could he use a chip from a truck or even a caprice???

 

I would be a good idea IF HE HAS A TRUCK/CAPRICE ecu. I don't know much but know that 90 ish trucks use 1227747 ECU's ad there are LOTS of them around. If you have this EC, download the ASDU bin (350cid truck) or a car 350cid BIN which would have a betterfrom the DIY site and start from there. hen you gotta get the chip burned.

If you have some other ecu, as suggested, get the PROM from a 350 cid version and plug it in.

[This message has been edited by FastBroker (edited March 02, 2001).]

 

There are several million GM Pickups running 350s never mind many fleet applications. First are you using the 305 injectors?.

If the engine is about stock, I'd be looking at the 747 ecm, and stock GM PU injectors and go from there. Lots of bins available for the 350 trucks

 

Use the ASDU (or ASDZ, later/better version) 350cid TBI truck BIN on the DIY site for the 1227747 ECU. It's what I started with and is VERY anemic sparkwise, anyways) but it'll get you MUCH more in the ballpark than you are now. I believe the 305 and 350 trucks used the same injectors but different BPW's in the PROM to make up for the difference, but I surely could be wrong. HAVE FUN

 

The 350 PU used 55#/hr injectors. 305 and I think the 4.3 shared injector sizes. I've never found a 305 with the org/blk coded 55 injectors, and I've looked at alot of them over the years <g>....

 

Thanks, Grumpy.

Maybe you can answer this one for me?: I have heard that the 454 trucks (2" Rochester TBI units) came with either 80 or 90 lb/hr injectors... First, is this true? and second, if so, is there a model/year that I can specify so that I get the 90pph injectors??? Third: Were the 454 truck TBI's set at 11psi, like the 350 trucks OR some other operating pressure, ie, are the 80 and 90pph flow rates specific for 11psi or some other "tested" psi??? I have heard that all the GM TBI injector flow rates were taken at 13psi (not the 11psi operating pressure of say, a 350 truck) and just would like to know. Brain food...


I ask the above because I am going to buy a rebuild unit and want to make sure I get the 90pph injectors, if I can do so. Trying for 400hp with Vortec heads, HOT CAM and the 1.6 rockers from the Hot Cam kit. Lots of PROM burning in my future!!!

Thanks in advance and sorry it's so long. Been bottled up inside!