Im putting a formerly tpi 305 in to my 88 firebird with tbi. Am i gonna run in to any problems with the computer.

 

You'll have to switch to TBI ECM (SD specific like 1228746 or similar). Do you have computer part number and BCC code???

//RF

 

Yea the car already has the tbi ecm and all, but i just found out the motor comes with the ecm which has been tuned so im thinking bout switching out the harness and stickin with the TPI.

 

just get a tuned tbi chip... keep your manifold wet.

 

Good idea! Dry flow is the way to go! But I'll be tarred and feathered for posting that in here.

 

 

What you're doing (using a 305 TPI block with a TBI on it) is almost identical to using a 305 TBI block and sticking a TPI/LT1 camshaft in it. The computer will be fine.

 

If you threw the stock, or even better, the edelbrock TBI intake manifold on that TPI motor, you would be doing great. The major stuff that we all want to do (TPI heads, LT1 cam) would almost be done for you. You wouldnt have to deal with the swirlports, or the peanut cam.

You would need to use a TBI computer and harness, which the car already has as you said. If the car was previously TBI, all the sensore ect. should plug in i bet.

You probably would benefit alot from some tuning. Especially since both the heads AND the cam will be better than stock for a TBI motor. I think you probably wouldnt loose too much power over what a LB9 would make maybe a few horses but not alot.

The LO3 is capable of 170hp stock. With an LT1 cam, thats 30 more right there. So lets guess 25 with the TPI cam. Now the heads, thats gotta be another 25 right there. Add in that a good tune will bag you 20-30, plus an exhaust will be more than that, you are up around the 250HP 300TQ range.

Thats just all and educated guess though.

 

Make sure the 305tpi engine doesent have the peanut cam.
If so it would be much quicker to upgrade with the engine out of the car.

Im actually courious how a lt1 cammed lb9 with stock tpi exhaust and intake would performe vs lo3+lt1cam+headers+complete exhaust+intake?

Wich sistem is more appropriate for tuning?

 

slow90firebird sorry but you just wont get those numbers out of those stock parts. 081 heads will not make more power than 187 especially since theyll stock and unported. 187s i think are better due to their better exhaust flow. he will not be gaining anything for the most part from the heads so that 25-30 is gone right there and the cam the 305tpis had small cams and the L98 cams depending which year/tranny it came with. if its the smaller cam again about no gain. BTW are you swapping motors cause ones dead or you think itll net you more power? if you killed a motor id say fine, but if youre doing it for power its not worth it. and also a tune will not get you that much power MAYBE and thats a big maybe if your a pro and youve done it for years everyday in and out but thats a big MAYBE. and yes everything will work together the computer should be fine and such. id say if anything youll lose power from this swap.

and MAF tpi is more forgiving to no tune remember that thomas1976. tbi needs tuning if you sneeze at it wrong. id assume he needs a new motor and not looking for power so this is a whole diff story on making power and tuning.

 

I thought the TPI heads were alot better because they dont have that "swirl" obstrucing the intake? I was actually considering swapping mine for a set of those, because they are cheaper than vortecs. And I cant remember where, but I read somehere the TPI cams specs, and they definately were hotter than the LO3 cam.

Maybe I am wrong, but I thought the LB9 came with 60hp more and 45tq more, in the same size motor as the LO3?

 

I was just considering some reflection, if he has a complete tpi engine I dont really see the point of swapping it to tbi.
Im still courious about lt1cammed tpi lb9 vs lt1cammed tbi lo3 ? (both tuned).

 

thomas i agree with you why change to tbi if you have the better/easier system(IMO). and i think the stock throttle body and intake manifold on the tbi system will choke it enough so the tpi with same exact setup takes the win. the tpi system on a 305 flows enough for what it needs its on a restriction on the 350's.

and slow90firebird dont get those heads. too much money for something thatll do you no good. the swirl doesnt really obstruct flow at low lifts or probably any lift youll be seeing on your motor since its a daily. heres some facts for you 081 heads exhaust flow is 110 compared to the 187s 140. so now the 081's take in 180-190 and 187s 160. but think of it this way you take in all this air but you cant get it all out because the exhaust of the head flows horribly. and LB9's made 20-40hp more than LO3's depending which year/options you choose. but its not the heads. take into consideration the LB9 had a bigger cam slightly if the peanut unless it was the same which i dont remember as the LO3 cam and then they had the L98 cam for the 5 speeds and the 91-92 all suppossedly. now our factory cam specs for the LO3 are .38- and roughly close to that on the exhaust. now the L98 cam is .4-- region so they have more lift and they had more duration too. now on top of this cam matter is the fact of the better induction(IMO). the LB9 with a tpi flows plenty for the 305 and is tuned setup so it makes more torque hence the difference in torque between the motors too. if you want this point proven look up dyno dons thread where he swapped tpi on to a tbi motor same TBI cam, heads, block etc. only put a tpi on it and dynoed it before and after. after he made a little bit more hp and a lot of torque. now since on the intake was changed theres what makes a big difference. and its proven with dyno numbers to back it up. also another member posted before and after times of an LO3 with tpi on top and he gained a full second in the 1/4 and he did the same exact thing swapping tpi on top of an LO3. he went from 16.1 to 15.1 .

now you wanting 081s can be a good decision as long as you port them or have them ported like fbird88's sets which flow vortec head levels if not more. unported theyll be useless for you. you cant desire vortecs and then decide to settle on 081s because the flow is way different, as are the power levels the support. ATM your heads are not what are holding you back from making power. you best bang for the buck would be a cam with a good tune. then on top of that top it off with an aftermarket intake manifold id say a carb one with an adapter since they flow better than the tbi ones. then mod your tb so more air can get into it. those are your biggest restriction but then put into consideration its useless to do all those mods then not know how or be able to tune which will make it a big waste of money. work on your current restrictions instead of whats working perfectly fine ATM. think of it this way your cam is in the high .3-- region and an ls1 cam is roughly .49- region. and look how much more power they make. theyre completely diff animals but to make power you have to have a cam that has enough lift and duration to get you there to start.

 

Many TGOers claim that the 416 heads have ports that are identical to 081... so the airflow for the stock 416 ought to be the same. If so, the 081/416 heads flow approx 190 cfm intake, and 120 cfm exhaust. i.e. fairly good on the intake side (for pre-Vortec factory heads) but very poorly on the exhaust. The 187s flow worse (165-170 cfm) on the intake, but much better on the exhaust (140-145). Is there a clear winner? Not really. The 416/081 flows more easily on the intake (which is good) but it consumes more power on the exhaust stroke because it doesn't flow as well. The avg airflow for each is about the same. And the 187 head is a better fuel burner than either the 081 or the 416, because the swirled mixture burns faster in the chamber, so it needs less ignition advance and hence doesn't consume as much torque during the compressive stroke... so more work gets done after TDC. Is the better combustion enough to tip the scales? I don't know and there hasn't (yet) been careful enough measurements to prove anything.

The numbers you cite are essentially correct. The difference(s) are from the combination of heads/cam/exhaust/tuning in the TPI engine up to 1992, whereas the TBI didn't change at all from 1988+. A better comparison to make is the auto trans TPI engine using the LO3 cam: 190 fwhp. It's still +20 hp over the TBI from the facory. The question is what's most responsible for the power difference (190 v 170). Many would say the heads (swirl v non swirl), or the exhaust, or the TPI v TBI... or all three.

The armchair debate has two added datapoints: both DynoDon and Fast355 have done before/after dyno tests of TBI and TPI. The results are posted elsewhere on TGO, and they are what they are: tests results with no clear winner. The interpretation of the results seems to fall along the usual camps (TPI, TBI).

If I had to choose, I use what I already owned. If I could DIY port either, I'd do it. Both will work, both are low-buck.

edit: TBI v. TPI thread

https://www.thirdgen.org/forums/tbi/...-tpi-dyno.html

and then see the three threads linked within

 

Oh I see what you are saying. TPI gets its power from the tuned intake runners then, not the heads or cam.

 

exactly so dont go out buying 081's thinking theyll give you power because likely i believe that youd actually lose power if anything. especially with the stock tune.

just like kdrolt said except i forgot the exhaust part. but he said it right and knows the tpi peanut cam and the tbi cam are the same. honestly i dont see the 20hp difference coming from a little bit bigger exhaust. so its up to you to decide where you think that difference came from. all you need is common sense and some understanding of math.

 

The 20 HP IS from the upgraded exhaust. The stock L03 system from the head-ports back, well BLOWS. The log manifolds are smaller on the LG4/L03 and have a smaller exit. The head pipes leading to the Y-pipe are smaller. The Y is a terribly restricting design, leading into a restrictively small 2 1/4" catalytic converter (same unit my 2.8 S10 had). The exhaust from the catalytic converter out was just as bad. Crossflow mufflers sap HP as well.

As far as the TPI making a huge difference in power, if both setups are properly tuned, you will see very little difference in actual HP, even with both intakes stock. The TBI setup will make more low-end torque and have a flatter torque curve all the way to redline, increasing HP over the TPI. The TPI makes its power in the mid-range, where the tuned runners help pack the cylinders with additional air/fuel mixture.

Stock 081 heads won't do a thing for you, under 5,000 rpm.

 

ok so explain why his swap which used same exhaust for both systems still gained more power when he went to tpi over tbi?

 

The stock TPI tuning is better than the TBI tuning and the ECM adapts better to small changes.

 

not trying to be an *** to you but that just proves the extra powers in the tune and not the exhaust. ive followed both yours and dyno dons work and you both do amazing things.

 

But here is what you are not understanding, is that if the TBI system is properly dialed in, I have seen 20-30 HP out of DIY chip work on STOCK engines.