My dad's car: Stock 305 TBI bottom end with 210k miles. With the TBI setup, it
made a best of 158 HP and 220 TQ. The only mods were a stock 85 IROC exhaust.
Now with a stock TPI on it, and an airfoil in the stock TB, it made 175 HP, and
290 TQ. Considering a 305 TPI in this combination is rated by GM at 205 HP and
285 TQ, apparently the torque is underrated for a 305, big time. Figuring 15%
loss, you get 205 HP and 330 TQ as dynoed.

My car: Previously, with the engine I raced in 1999, with iron heads, a 198/210
cam, 1.65 rockers on the intake, 1.5 on the exhaust, and a stock TPI intake with
airfoil, it made 210 HP and 335 TQ. Now, the same engine, but with ported iron heads, a 201/207 LT1 cam, 1.65 rockers on intake and exhaust, and a ported TPI intake with 52mm TB and airfoil, it makes 250 HP and 335 TQ. Thats 285 HP and 385 TQ, with 15% loss again.


------------------
West Coast GM Shootout 2001!
1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

 

What I want to know, is what would that car have made with a carb on it. My guess is a little more HP than the TPI, at a higher RPM, and a little less torque. Sound right?

 

Cool deal, thanks for posting that. I should have my TPI setup soon and hopefully will be able to install it in the next couple of months. Is your dad gonna do any sort of write up on the swap, and/or would he be able to answer questions about it? I've gone over the tech article but of course have tons of Q's. I would like to have all of my ducks in a row before I start the swap to insure that it goes smoothly.

 

We cant swap to a carb because CA wont allow it. But yah, it would be nice.

My dad is writing up the tech article now on how to swap while using your TBI harness. I dont know when he will be finished tho, as he is very busy with regular work. If you have specific questions, you can email him at delcruzen@hotmail.com . If you just want to ask "whats the best way to do it?", dont bother.

 

Did the heads remain the same?

 

Well uhh was that with the stock TBI setup? With the spacer removed and ridges shaved down and dual snorkel intake the HP should be 10-15HP higher.

 

Everything remained the same. We just removed the TBI intake, put the TPI intake on it, and swapped some pins in the TBI harness to work with the 7730 speed density TPI computer. Nothing was ported, changed, altered, or anything between the TBI dyno and the TPI dyno, except gas and oil. Both the TBI and the TPI use stock PROMs in the computer. Both were ran with factory timing, 0º for the TBI and 6º for the TPI.

Both TBI and TPI intakes were bone stock with no mods, and K&N air filters. The TPI throttle body has an airfoil, which is negligible.

Any other questions?

 

did'nt you have to change the fuel pump?

 

No more questions from me, but great post Kevin. GOOd info.

 

Nice gains... really shows how well the tuned intake works. Are you going to post the dyno graphs?

 

not bad at all.. in fact im shocked that you made that much HP and torque with the peanut cam and swirl port heads.

------------------
91 Trans Am WS6
Bright White
5.0 TPI auto
Flowmaster 3" 2 chamber catback
Trans Go shiftkit
2000 stall converter

Built on Wednesday

 

You don't have to change the fuel pump when switching from tbi to tpi because G.M. used the same pump in both systems. The tbi unit has a built in pressure regulator to drop the
fuel pressure.

 

Whoops, yes we changed the fuel pump too.

Russ, I've never heard that. The pump that came out of my dad's RS was a 15 PSI unit.

Oh, and MrJ, yes this one has a peanut cam.

[This message has been edited by Kevin91Z (edited January 25, 2001).]

 

Did you ever do a dyno pull with the TBI set-up at higher timing than 0* ?? When I changed from 0* to 6*, which is what I run now, I picked up almost 2 tenths at the track and the car ran totally different. I'm not saying that the TPI wouldn't have made more power if they had been equal, but the TBI dyno pull would have been much closer.

------------------
82 Z28 350, Ported #882 Heads, Performer RPM cam and intake, hedman headers,650 Demon carb,
Trans: Turbo 350 w/ 4000 stall -- Rearend 7.5 w/ Richmond 4.10's, Auburn Minispool
Best ET: 12.52@107.2
Future plans: Dart headed, Roller cammed 383 in early '01


89 RS, L03 305, Hypertech Chip,cat delete, Dynomax exhaust,K&N open element Filter,160 stat, MSD coil --Trans:700R4 Corvette Servo -- Rearend: 7.5 GM 3.42 w/ posi-lock
New Best ET: 14.91 @92.9
Bassett Racing
Mid Atlantic F Body -82 Z28 Page

 

No, as I said in the other post, the point was to dyno a "stock" TBI engine and a "stock" TPI engine to see the difference. We didnt change things around or play with settings to get more HP out of the TBI engine, because it wasnt going to stay TBI.

 

If you don't have a scanner to scan in the dyno graphs, can you type in a sort of chart with the HP and TQ numbers at rpm points for both motors.

Just wanted to be 100% clear on something. Did the TPI setup get run on the stock TBI swirl port heads or a set of stock TPI heads?

 

Know what? Now that I think about it I'm not sure LOL!

But the heads were the same both tests, I know that.

[This message has been edited by madmax (edited January 26, 2001).]

 

All we did was change the intake manifold. The heads, cam, block, pistons, rods, transmission, etc etc, were untouched. A stock TPI intake was used, untouched, and unported. The only mod to the TPI unit was an airfoil, and I really doubt that changed anything.

Edit: I dont have the dyno charts in front of me, my dad does. I'll see him tonight so I can type them up this weekend.


[This message has been edited by Kevin91Z (edited January 26, 2001).]

 

I think you may have messed up the tq conversion. I came up with 205hp/340 ft/lb For the TPI setup. Thats 185hp and 258ft/lbs crank for the TBI car. Divide rear wheel numbers by .85 to get crank numbers and multiply crank by .85 to get rear wheel.

So what this dyno test is telling us is difference between the stock TPI hp and tq numbers and the numbers your dad obtained are in the heads... That Stock TBI heads are worth 30ft/lb more torque than stock TPI heads???

Did the dyno operator correct both runs to standard?

 

He said the heads were not changed, meaning the TBI swirl port heads are on the car now, with the TPI manifold.

That means the TBI and TPI heads flow the same and dont make any difference in HP if the test results are correct, its all in the intake manifold and exhaust.

 

I multiplied by 115% to get the crank numbers. Its just an estimate and not to be used as actual numbers.

No the runs were not corrected.

I dont know whether TPI and TBI heads are the same.

 

TBI and TPI heads ARE technically the same, both swirl ports. However, GM did have alot of left over non swirl port heads that got used (I'd guess on both). thats why you hear rumors that TPI got better ones...some guys tear down thier motors to find non swirl port heads and assume all other TPI's are the same, but thats not the case. Besides, it really doesn't make much difference IMHO.

------------------
"American made baby. 100% American iron. The muscle among the masses. My hero. Yep, you can take your ergonomically designed, space age, computer controlled, 4 door, cup holding map lighted split double wishbone split fold down retractable cargo covered moon roof piece of transportation and keep it. For I have felt the thunder. And I know the difference!"
JSP Motorsports
ICON Motorsports

[This message has been edited by Jester (edited January 26, 2001).]

 

Jester, that's the first time that I've heard that both motors use the same heads. So you are saying we have 305 TPI guys here who have pulled swirl port heads off their TPI cars? Good info.

The point I'm making is something looks odd in the tests... The TBI motor made about the expected amount of power and torque... the TPI motor made the expected power but the torque was off the scale.

Everything was as expected except that TPI torque gain of 80 ft/lbs. Typically a 300 ci motor will pick up 20-30 ft/lbs with a tuned intake over a non tuned intake... that is backed up by GM's advertised numbers. A 70 ft/lb increase is... well... hard to buy. Kind of like expecting 15 hp from a K&N.

That tpi intake is a lot of good things but its not magic.

Kevin I know its petty but if you are saying you have a 15% loss in the drivetrain... it means you are correcting from crank power... you subtract 15% or multiply by .85... to get back to the original crank number you have to multiply by the reciprocal or 1/.85 which is the same as to say divide by .85. If you do it this way it will keep your estimates as accurate as possible and make it possible to convert back and forth without error.

 

Well..actually I've never personally seen a TPI car that didn't have the same swirl port heads...out of the 3 or 4 I've torn into. All the people I've talked to directly all say the same thing...but like I said there are rumors of people finding non swirl port heads. Kind of a bigfoot story if ya ask me

------------------
"American made baby. 100% American iron. The muscle among the masses. My hero. Yep, you can take your ergonomically designed, space age, computer controlled, 4 door, cup holding map lighted split double wishbone split fold down retractable cargo covered moon roof piece of transportation and keep it. For I have felt the thunder. And I know the difference!"
JSP Motorsports
ICON Motorsports

 

Well the dyno don't lie. Besides, it's not that the TPI is magic..it's that the TBI sucks so bad...but thats just my opinion

------------------
"American made baby. 100% American iron. The muscle among the masses. My hero. Yep, you can take your ergonomically designed, space age, computer controlled, 4 door, cup holding map lighted split double wishbone split fold down retractable cargo covered moon roof piece of transportation and keep it. For I have felt the thunder. And I know the difference!"
JSP Motorsports
ICON Motorsports

 

the tpi heads ARE different
the perimeter bolt tpi motors had #416's the center bolts used 081s and as we know the lo3s have 187s

Im not sure this was a totally variable free comparison, i heard the rear end ratio was changed too, i cant help but wonder what that would do to the torque reading on an inertia dyno (if it did anything at all)
something to consider

 

there is no doubt that the stock TBI does not make power.

...need to see the dyno graph to see what rpm the tpi setup is doing its thing.

You're right that dynos don't lie but they are a scientific measuring device and like all scientific processes there are variables in test conditions that must be considered when analyzing results. For example, the dyno numbers were not corrected to standard temp/humidity/barometer... this has to be done in order to compare tests from different days. The adjustments might be insignificant but then again, they could account for 10-20 hp.

 

I think you guys are picking at straws... lemme tell you a little story:

Don L came over after they finished the swap. He said the car was much quicker, IIRC he said something about the way it got squirrely shifting from first to second, unlike how it was with the TBI. This is coming from a guy who has been racing for years and owns a, what is it Kevin, an 8 or 9 second Camaro? I hadnt seen any dyno results at that point, but listening to how much of a difference he said it made, and knowing who he was, made me think that the results were gonna be like what you see above.

 

When I asked about different mods, I wanted to know, for my own knowledge, how different mods affected HP on the TBI engine.
Now, about the timing, you said "Stock meaning as they came from the factory" but actually, this is not a truly accurate or fair comparison, due to the fact that this is still a L03,with LB9 timing and a TPI unit installed. 6* timing is factory on a LB9, meaning that the engine would have different heads, different exhaust, and on most engines a different cam (I know,some TPI cars have the peanut cam). This engine was designed from the factory to be this way because this was the so called High-Performance version of the 305, the TBI engine was 0* due to a highly restictive exhaust, poor cam, poor flowing heads and the fact that the base engine, or base V8 in our case, needs to be able to run on 87 octane (try running 87 octane with the timing you have now, and you'll see what I mean). Putting better exhaust on a L03(which has been done to yours) and advancing the timing to 6* makes a very noticable difference.So in inclusion, the only REAL way to have tested the TPI unit against the TBI unit would have been to have a TBI engine with stock EVERYTHING e.g exhaust, air filter, gears, and timing, and then bolted on a TPI unit and left EVERYTHING else alone, or Vise Versa, put a TBI on a TPI engine with the same controls -- no changing timing, no air-foil, no K&N's -- that would have been the ONLY way to have an unbiased, totally equal comparison, or with no S-L-A-N-T, as you said. The reason I'm pointing this out, is to inform people who may not know that if both of your dyno pulls would have been done with the same timing and gears, the difference would NOT have been as much. The TPI would have probably still made a little more HP, and it would have definetly made more TQ, I've never doubted that, but it wouldn't have been as much. If someone read this and went out a paid a considerable amout of $$$ for a TPI unit, and they were already running 6* timing, and had an open-element air filter, gears, exhaust, etc. on their TBI car, I think they would be very disappointed, especially if they were racing the car on the clock at a track, because a guy just driving a car on the street would feel a difference in TQ and the car would be a lot more fun to drive, but I just don't think the numbers would be what he expected on the clock, plus he would have an induction system that would cost much more $$$ to upgrade than what he had before. Now once again, I'm not saying this to discredit, or to discount your research in any way, please don't think that, I'm only saying that if someone bolts on a TPI, and they've already changed timing, gears, exhaust, etc. and expects get 17HP and 70ft lbs (especially that much TQ), he's going to be very disappointed. JMHO

------------------
82 Z28 350, Ported #882 Heads, Performer RPM cam and intake, hedman headers,650 Demon carb,
Trans: Turbo 350 w/ 4000 stall -- Rearend 7.5 w/ Richmond 4.10's, Auburn Minispool
Best ET: 12.52@107.2
Future plans: Dart headed, Roller cammed 383 in early '01


89 RS, L03 305, Hypertech Chip,cat delete, Dynomax exhaust,K&N open element Filter,160 stat, MSD coil --Trans:700R4 Corvette Servo -- Rearend: 7.5 GM 3.42 w/ posi-lock
New Best ET: 14.91 @92.9
Bassett Racing
Mid Atlantic F Body -82 Z28 Page

 

175 * 115%= 201.25
290 * 115%= 333.5

175/.85= 205
290/.85= 341

don't know, but really splitting hairs here. correct me if i am wrong here, if the transmission was in a 1:1 ratio the torque numbers should be reliable to convert to an estimated engine torque accurately.

 

Hey Kevin91Z, tell ur dad if he could run some times. Im dyin to know what it would do. I gotta 89 TBI 305 and probably get my TPI set from the junk yard.

 

ohh yeaha and i got 160k miles.

 

I did some research on the cam thing. The only peanut cammed TPI motor was the 1987 305 automatic. All other 305 TPI roller motors shared the same cam as the 350's of the same model year. I have GM part numbers at request.

[This message has been edited by Dan W (edited January 27, 2001).]

 

I dont think we'll run the car in this configuration, but who knows right now.

I wont be able to get the dyno graphs scanned until I get to work on Monday.

 

Dan W '86 TPI's had the peanut cam too. We used to have one.

Pablo, changing the rear end gears will not affect the RWHP. See my post under this same thread in the TBI forum.

 

Nope..wrong. The peanut cam was used in ALOT of 305TPI motors. IIRC, all the 87-89 auto cars, all the 90-92 auto cars, and all the 90-92 manual tranny cars without the G92 option.



------------------
"American made baby. 100% American iron. The muscle among the masses. My hero. Yep, you can take your ergonomically designed, space age, computer controlled, 4 door, cup holding map lighted split double wishbone split fold down retractable cargo covered moon roof piece of transportation and keep it. For I have felt the thunder. And I know the difference!"
JSP Motorsports
ICON Motorsports

 

Jester, it looks like our references differ mine states that from '87 up the only TPI motor to get the peanut cam was the '87 305 auto. Maybe the reference I used is wrong.

Tom, I stated roller motors... this means '87 up.

 

Careful Jester, wait till MrJ sees your post. He and a couple other people are convinced that the 90-92 LB9 cars all got the L98 cam, regardless of transmission. They have a few references but I am not convinced until a 90-92 LB9 single cat engine has its cam checked.

I'm surprised that these two posts got the attention they did! It really sparked some discussion.

 

The cam thing is easily verified. We only have to to find a guy at the GM parts counter who is willing to find 25 part numbers for us. I've already got a few and can post them tomorrow.

 

As for the cam thing im very curious myself. My car should be a peanut cam case, but it will pull past 5k in 2nd gear (hey whaddya want with 2.73s), not screaming, but far from falling on it's face. I don't think a peanut cam would be up to that.
I plan on checking my valve lift with a dial indicator at some point in the future. That will settle it once and for all (at least for my car...lol)
...ed

------------------
Ed Maher - Moderator @ The Carb Board
92 Z28 Convertible - Quasar blue / Tan top
LB9 4L60 GU2 G80 - stock, soon to be sleeper

- Definitely prototypes, high powered mutants of some kind. Too weird to live, too cool to die

 

Ok folks, my scanner really sucks, but here are the graphs:
http://24.1.139.249/images/dyno/

TBI1 shows max power of 158.1 HP and 226.5 TQ.
TBI2 shows 156.9 HP and 225.7 TQ. These were back to back runs on the same dyno, in June 2000.

The TPI dyno has both runs on top of each other, made on Jan 24th. Run 1 was 175.2 HP and 290.8 TQ. Run 2 is 174.7 HP and 285.7 TQ. I dont know why there is a 5 TQ loss on the second run.

 

The Technical database has the cam part numbers listed for the different cams and the engines they came in.

I have had a 85, a 86, and a 87, all 305 TPI autos. I've also driven a 89 and a 91 which are supposed to also be peanut cammed. Everything that was supposed to have a peanut cam, had the lower rpm redline tach, w/ the 85 getting the higher one. My 85 (202/206 cam) was noticeably more powerful and had a better rpm range, you can feel the peanut cammed cars lay down especially when I compared back to back w/ my 85/87. The 89 and 91 didn't feel noticeably different from my 86 and 87, although those were not back to back and thusly are even more subjective.

I think the reasons some people think the 91-92s are hotter cammed is due the the other small changes that added on HP over the years, they did pick up 10-15hp just w/ little additions and tweaks on all the motors. I could buy the 91-92s getting the better cam, but I kinda doubt it. The difference is enough that we'd see better times than we are. The SD system, the lighter pistons, etc that accounted for the added 15hp rating increase coupled w/ actually having the hotter cam would have put these 305s well into the 350 TPI's range (especially the early 350 TPIs), which in my experience they are not...

The only way to be sure is going to be to pull some cams and check. Even what the dealer shows as the part number for what went in may not be correct now.

------------------
Ray87Z
-Vortec headed 350.
86 IROC w/ a cammed 305 TPI.
Formerly Ray86IROC.
www.inter-scape.com/Ray

[This message has been edited by Ray87Z (edited January 30, 2001).]

 

Theres a bunch of threads on the same subject floating around here, but I pulled and spec'd a cam from a 91 LB9 that was not a G92 car, and it did not have the peanut cam. If you want my opinion, I think the earlier years were mix+match (typical GM) and the later ones (TPI's) all had the same cam.

 

its good to see you back, Ray. I was wondering where you'd gone off to.

Just a few details... 305s never got the hypereutectic pistons. The reason why we aren't seeing better times is due to the 2.73s in the auto cars and the 3.08s in the non-G92 5 speed cars. Finally, the performance IS on the level of the early 350 TPI cars... to use mine as an example, I ran a best time of 14.9@93.5MPH, on a crappy 2.3 60 foot, last April. This was before the rebuilt tranny, shiftkit, and converter, by the way.



------------------
91 Trans Am WS6
Bright White
5.0 TPI auto
Flowmaster 3" 2 chamber catback
Trans Go shiftkit
2000 stall converter

Built on Wednesday

 

Yeah, I kinda lost interest in the car boards for awhile for some reason. I'm getting the more performance bug thing again, I need a built 406 or something now, lol. Alas, I have no money...

I didn't realize the 305s didn't get the hyp pistons. Hmm.


------------------
Ray87Z
-Vortec headed 350.
86 IROC w/ a cammed 305 TPI.
Formerly Ray86IROC.
www.inter-scape.com/Ray

 

Correct me if I'm wrong,
but if you're wondering if it's a peanut cam or not....why don't you just look for the 5k redline.

Every G92 I've seen has the 5500, a friends LB8 88 auto Camaro has the 5k redline.

 

It seems to me like the 90-92 TPI cars that have the 5000 redline tach, also have the 120MPH speedometer. It's just the base gauge package, same as the TBI cars... it's probably there for the same reason the TBI exhaust is there too.. because GM is retarded as ****.

 

Or use these part numbers:

1986 305/AT (LB9) - 10088155*;
1987-1989 305/AT (lb9), 1990-1992 305/5sp (LB9) - 10088155 (roller);
1987 305/5sp, 350AT - 14093643;
1987 305/AT (LM1)(SEO/Police Package) - 14093640;
1988, 1989 305/5sp, 350AT - 10066049;
1990-92 305/AT (G92), 350AT - 10111773.

* - 1986 10088155 is a flat tappet grind.

Sorry, I don't have the part number for the 1985, but it is essentially the same grind as the 14093643 used in the '87 L98 and 350/5 speed engines. Contrary to some beliefs, teh LM1 cam was NOT a better profile than the L98, but was a compromise between the "LA" cam (peanut) and the L98 profile.

------------------
Later,
Vader
------------------
"Make Me Bad..."
Adobe Acrobat Reader 4.0
KaleCo Auto Parts

 

It's more like, you got what you paid for. There were a few more engine options in the last ThirdGen years, and if you didn't pay attention you could have accidentally got a good one.... kinda like the guy walking in with a fat checkbook in 1992 wanting to buy a Corvette, saying "What the heck's a 'ZR-1' there, Beuford?"

There were TWO different cams available for 305 - five speeders in 1990-92. If you got the G92 RPO, you got the best cam. Anything else came with the roller "LA" cam and that might explain the speedo difference, too. Incidentally, if you didn't order it with 16" wheels, you also have the 118MPH speed limiter programming, so the 120MPH speedo should be more than enough.

------------------
Later,
Vader
------------------
"Make Me Bad..."
Adobe Acrobat Reader 4.0
KaleCo Auto Parts

 

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