kaylin4u

I've built a roller 355 with the following specs: 1) 10.2:1 compression 2) Dart Pro 1 (pre 87 aluminum heads) 3) Comp Exteme Energy 274/286 (with my 1.6 roller rockers at .544/.536 lift) with a band of 1800-5800. I'm putting this in a 1991 305 TBI equipped firebird, and wanting to utilize the TBI for this engine. My question is this: Do I need to upgrade the intake to a Holley 300-49 pro injection intake, or a Edlebrock performer TBI intake? Or should I utilize some carb intake with a TBI adapter plate for this? Also, what size injectors have others used in a similar setup like this? Thanks!

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dimented24x7

While a tbi system would work, there are going to be some hurtles to be overcome. The tbi ecm wont work without tuning. It would run terribly if at all. The VE and spark tables and alot of other stuff will be way off for your motor. I think it could be made to run acceptably with tuning but its not a bolt on sort of thing if thats what your thinking. The tbi ecms (and the SD tpi ecms) have no way of knowing what its controlling and it must be told by you what the needs of the motor are.

Also, Ill be honest and say that the tbi ecm isnt the best choice when it comes to performance. With some changes the ecm can be on par with the other ecms but those are usually beyond the scope of the novice tuner.

With that said you may want to run a carb with the ecm controlling the spark to start off with while you familiarize yourself with tuning a computer. Later you can put a tbi on and see what you think of it overall. Thats a healthy combo with a not too efi friendly cam you have and it wouldnt be a bad idea to take it slow and see what changes you have to make.

As for the tbi, get a large 2" tbi and the largest injectors you can find. Youll also need a good fuel pump since youll ultimatly want to run higher pressures or a vacuum referenced fuel pressure regulator so you can have an adiquate fuel supply. Since you may want to run a carb at times get a carb intake and adapter.

EDIT: heres some good info as well as how to use it for spark alone. http://www.diy-efi.org/gmecm/papers/

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dimented24x7

Also make sure to search around and see what itll take to tune with efi. The diy-prom board is a good place to start.

kaylin4u

Well, do the TBI equipped cars have a return line similar to the TPI setup? Can I just a TPI fuel pump instead of the TBI fuel pump or are TBI equipped fbody's different?

Also, I have the programming equipment. So I plan on doing what you said on the ecm. Just wondering if choices were made, would you use the Holley Pro injection intake or the edelbrock performer TBI intake? I plan on boring out to 2" no matter what intake I use and also going to larger injectors.

Benm109

I can't answer all of your questions but, yes TBIs have a return line and yes a TPI pump is a direct swap for a TBI pump.

Also, I'm not sure about the Holley intake, but the Edelbrock intake was a direct swap. Only had to drill and tap one hole and that was it. Everything from the old manifold bolted straight to the Edelbrock with no problems.

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kaylin4u

Where did you drill and what was it for?
I'm wondering if anyone has swapped the TBI fuel pump with a TPI fuel pump and what problems they ran into.
BTW, thanks.

Benm109

I just had to drill and tap a hole for the AC bracket (tubular piece that runs from the middle of the intake to the side of the bracket that holds the AC compressor and smog pump on). The instructions say that you have to modify the line that runs from the intake to the brake booster too, but I didn't have to.

kaylin4u

Okay thanks.

BTW, have you had any experience in doing your own eeprom for 1228746? I've already posted a question in the DIY, just new to the TBI setup thing.

Benm109

Nope. I need to start burning my own chips but I need a laptop first.

EDIT: I responded to your other post. I can answer that question.

BMmonteSS

I suggest skipping the TBI intakes for your combo, and going with a carbed intake. You'll probably have to go with a low profile single plane for your combo. I would stay away from tbi for a while till you get really good with chip tuning. I did the same thing your wanting to do, start with timing add TBI later. Lets just say the timing stuff went quickly and painlessly and actually was a big improvement over a mechanical dissy, but TBI took a long time to get right. I'm running a comp extreme 262-274 .462- .480 and getting a good idle has been a big problem. The big throttle body and big injectors makes for some funky fuel atomization problems.

Your biggest problem is going to be getting enough fuel. I'm only making 300 hp with crappy heads, your going to be making tons more power. I'm running 75 pph injectors at 22 psi which makes them act like 110 pph, and I'm just barely able to feed my motor all the way to 6000 rpm. Actually the injectors going static act like a rev limiter right after 6000, not good. your going to need 90 pph injectors and even more fuel pressure to even get close. And at that level the 2" TB intself gets to be a restriction.

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kaylin4u

I guess the best thing to do, is just get the TPI, TPI wiring, computer, etc. and move them over. I hate having to move all this stuff over, but if TBI has this much trouble, then I'll stick with TPI.

ShiftyCapone

You can stick with TPI but go with an aftermarket intake. The stock TPI will murder the power potential of your combo.

kaylin4u

I thought about going with the lt1 intake modification that's on lt1intake.com.

dimented24x7

You can go to very high pressures with the stock injectors. The listed maximum pressure rating is just over 100 psi. You could feed your combo but youd need to ahve some form of variable fuel pressure like a Vacuum AFPR or FMU and compensation in the code.

As for tpi. Make sure you get one of the later 90+ SD systems, no MAF! Also, youll definatly need another intake like said above. After that, youll have to purchase prom burning equipment and a WB-O2. Itll take some time to learn how to tune it but I think youll like the results.