I have an 85 iroc with stock 305 mat system. I'm putting in a 383 with the stock tpi setup
2.02/1.60 cast heads
Ligenfelter,actually comp-cams makes them, flat tappet cam:
214/224 @.050, .472/.496 w/1.6 ratio rockers
3.42 rear with 700r4
I believe its about 9.5:1 CR
I am still building the motor so I will have time to get a computer if needed. So will I be able to use the stock ecm and maf setup.

PS. I will be using stock 305 injectors @ 19lbs. pushed to the halt. Thanks for your opinions.

 

well...short answer...yes it'll work

However...with those mods you need to run at least 350 injesctors. Also you'll need to get a prom for a 350 for the ECM. With a 305 prom and 305 injectors you'll be running the engine very lean and will have lots of problems.

 

Thanks for the info, but could you explain to me why I will be running lean with 305 injectors. I've read that 305 injectors can flow enough for up to about 375hp. I don't know if this is true or not, but I may find out. Also, what will swithcing to a 350 prom do, I thought there was not much difference. This is wht I ask, cause I don't know. I'm mostly concerned as to why you said it would run lean. Thanks

 

You have almost 80 cube's more than the computer thinks you do, and with the bigger cam, and heads you will be flowing a lot more air than you would be with the stock 305. Because of that the 305 prom and injectors probobly won't be able to add enough fuel to keep the proper A/F ratio. Those parts were designed to feed a stock 305...not a hi perf 383. The 350 prom, on the other hand, thinks it's fueling a 350...still 33 cube's smaller than what you have but a lot better then 78.

 

Thanks for elaborating on this for me, it clears things up a bit for me. Do you know which year proms i should use, or should I switch the whole ecm with an 86-89 year ecm.

 

You can use the computer that you already have....just get a prom from a 350 tpi.

 

Thanks for your help.

 

ah, if life was simple. lets see, an 870 ecm, hmmm, 350 tpi chip, you must mean corvette of the same year. im thinkin no, that wont work so good unless the f body engine mgmt harness is massaged a bit to match the vettes, something with sensor grounds, the oil temp, search around here, i remember someone trying that chip swap and it didnt work out too good. the vette cal. is just different enough to not function properly in a f-body. you do not want a 350 chip anyhow. actually the 305 chip is set up to issue a larger injector pulse width for any given load\rpm point than the 350 chip is set up for. if you were to put a 5.7 chip in the camaro somehow, you would actually lean it out across the board. just do the math on the injectors and you will see the percentages between engine displacement and injector fuel flow rates are way different from 5.0 to 5.7 thats why i think that also in the tpi vette there was also a fuel pressure reduction when compared to the camaro. so stick with a 305 chip and up the fuel pressure and as long as the cam aint too large, you will be safe. this i know from years of owning my car. in 1987 i built 400 for it. pretty much became joke material with my buddies, 400 sbc back then was considered humorous at best for h.p. duty but it worked real well with the tpi setup and n2o prolly too much grunt on the bottom end to hook properly but spinning tires never overworked the flimso-body, safer than hooking up. the chip you ask? an original stage 2 (oooh, ahhhh,wow) hypertech pt#11522. that setup remained in place from 6/87 (still got the dated hypertech reciept along with the chip) till about 2000 and never gave me any headaches. thats with 19 lb injectors.
:rockon: :hail:

 

Thanks a lot Grease Ape. Finally someone who knows what the hell their talking about. The pulse width for the 305 Injectors is a longer duration and also on the 1985 tpi ecm, I'm pretty sure that the ignition curve is pretty good, don't quote me on that. Anyway thanks for the info. To all you out there that think something just won't work because you read it won't, try it first instead of posting something that you do not have first hand knowledge at. Remember in elementary school when you went around the room and wispered something in the kid behind you's ear, did the saying ever come out correct when it came back around the room?
DON'T BELIEVE ANYTHING YOU HEAR AND ONLY HALF OF WHAT YOU SEE.

 

I have been running a 350 chip from a corvette in my 85 iroc 357 with no problems so far. Runs like a rape ape and decent mileage too. Mods in my sig. It is still the 870 ecm.

 

Just adding my $ .02
The problem you may have (if you don't make a custom burned chip) will be the open loop when cold starting and other issues.
The base pulse width "may" not provide enough fuel for good idle quality. Some drivability issues may arise.
If the fuel pressure is bumped up, then you may get around this.
Once in closed loop, the ecm will compensate for the weak VE tables to keep you running ok.
The big kicker here is that if the ECM throws a major error and goes into "limp" mode, the resistor pack within the memcal will provide better service if from a 350. The 305 may leave you calling for a tow.
My 22# injectors running at 50 psi (equate to 26#) do not like to run on the 350 chips limp mode as it is now. It runs but I hope I never need to use it.
Just my opinion.
JP