PhoenixFirebird

iTrader: (2)

Like many others that run TPI, I'm throwing some go-fast parts at it. It gives a feeling of accomplishment to run a fast TPI. It's a bit more challenging then just throwing a carb on a motor and calling it done. By all means, it would be easier to go that route, but I personally like being one of the few guys at the track not running carb. I also love the look of the LTR setup. Who doesn't?

Anyway, after throwing a ported Edelbrock Hi-Flo intake on my 305 along with some ported SLP runners, I have to say the results were unpleasantly unexpected. For a few weeks now, I've been combing over every inch of the car seeing what I didn't put back on right, or adjusting the tune for more fuel. Everything is normal, other than the sluggishness of the motor. Naturally I was worried my parts were bad, a pretty big worry considering I bought them off the classifieds on here, and I can't just "send them back." This had me stumped until last night, when a fellow racer threw some ideas at me. He suggested my cam and heads could be the limiting factor, and not any fueling or spark issue. This leads me to the main point of the discussion.

Reports of aftermarket intakes and bigger runners report fairly small HP gains for their cost, but they really help shift the powerband up into a decent RPM range, so TPI doesn't fall on it's face after 4700 or whatever until it shifts. I noticed more pull at higher RPMs before shifting, but my bottom end seemed to be non-existent. After shifting, it's a dog until about 4000. Before installing the intake, I was 2.1x 60'. Now I'm 2.2x-2.3x. 1/4 ETs down to 15.8x, compared to 15.1x-15.2x with stock LTR setup. Could the ported aftermarket parts flow TOO much air? Definitely a possibility.

Rob also runs a 305, although he has a slightly better cam being a manual from the factory. My "peanut cam" isn't helping anything, I'm sure.

It seems as if the aftermarket TPI selection is based on bigger motors - 350, 383, and rightly so. 305s aren't exactly very popular in the racing world. From what I've read, L98 guys gain from aftermarket TPI right out of the box, and of course with porting too. It seems that a 305 needs an all around package to really gain with an aftermarket intake/runners, especially ones that have been ported heavily as mine have. Even with an open filter CAI, ported TPI components, and leading out to a set of Hooker Super Comps, it's not getting the work done. Is finishing up the combination with reworking the heads the answer, or is the 305 just not capable of breathing that much?

So let me ask all of you, how has your experience with aftermarket TPI parts been? This should be interesting to see, as I haven't heard too many guys with 305s sticking on go-fast TPI parts. Or maybe my parts got screwed up by whoever ported them, and this is just post count Let's hope not, I'm interested to see how everyone else's small motors react to these parts.

yaj15

iTrader: (3)

Yes TPI was designed for the 305. In the early 80's when TPI was being developed GM was considering not producing the 350 anymore due to new fuel economy and emissions requirements that the govenment had mandated.

GM wanted a way to give a smaller size engine (the 305) the torque of an earlier (late 1970's) carbed 350 while still meeting the CAFE fuel economy standards and tougher emissions regulations.

GM found that the 350 could still continue to be produced while meeting the new govenment standards after completion of a testing program. The problem is that GM didn't want to spend the money to update or change the TPI system for the 350, an engine that is 45 cubic inches larger than the 305. So since the 305 and the 350 were technically still a part of the Gen 1 small block engine family GM didn't want to do a lot of testing and spend a lot of money to get the TPI 350's going and delay turning a profit.

This is part of the reason that most stock LB9's generally pull well to 5,000rpm and the L98's start running out of steam around 4,500rpm. If designed properly GM should have given a better breathing TPI system to the L98 style engines because the TPI system was orginally designed for a 305 engine with 45 less cubic inches, and thus a lower air intake requirement.

Having said that, as I and many others will tell you, there are numerous ways to open up the stock TPI system and really boost the performance. With a modified TPI system that operational range can usually be extened to 5,500rpm - 6,000rpm. There are members on here who have stock style long tube runner TPI systems that still pull up higher in the rpm range. These systems also still exhibit the main characteristic of TPI with respect to excellent low - midrange torque and horsepower that TPI systems are known for.

Back when TPI was being designed it was just cheaper for GM to just change the injectors on the TPI system (305's got 19 pounds per hour injectors & 350's got 22 pound per hour injectors) and the PROM (with respect to LB9/700r4, LB9/5-speed and 350/700r4 powertrain combinations) rather than design a better breathing intake system for the larger engine.

You have to get rid of that peanut cam to. The LB9's that got the L98 style camshaft have a significant performance advantage over those that don't. There are a wide varitey of cams that can be used however. A stock L98 cam will work with what you have well out of the box. For the mods that you have you may want to consider getting a custom PROM chip so that you can get the most out of your modifications.

Also what rear gears are you running? That could also be part of the lack of performance question to. Many of the 1989 LB9/700r4 cars came with 2.73 gears.

The G92 performance rear gear combinations for 1989 were as follows:

LB9/T-5/3.45 gears with posi

L98/700r4/3.27 gears with posi

In terms of performance most long-tube-runner stock style TPI systems usually run good with rear gear ratios around (3.23 10bolt / 3.27 9bolt) or (3.42 gears 10bolt / 3.45 gears 9bolt). 3.42 or 3.45 rear gears with the 700r4 is the deepest I would go with a stock style TPI system.

The 700r4's first gear ratio is 3.06.

(3.06) * (3.42) = 10.4652 for an overall gear ratio.

A good transmission first gear and rear end gearing combination should be around 10 for good performance.

If your car isn't running at least 3.23 gears that could be a problem too. I'm starting the process of changing my gears from 2.77's to 3.27's. That should wake my car up in terms of performance.

PhoenixFirebird

iTrader: (2)

I'm aware of the factory parts being meant for the 305 rather than the 350. I'm looking at aftermarket though. It's almost as if they pull in too much air in regards to a 305. Where the stock parts may limit a 350, and aftermarket parts will help, I'm thinking they're just overkill for a 305. Especially ported.

I'm not concerned exactly with better performance with regards to this thread, just comparing the effects of stock TPI vs. aftermarket TPI on the 305. But I may aswell add in my setup, although not optimal it's a WIP. I do have custom chip burning equipment, and I've burnt my own chips for a few months now. I have 2.73 gears out back, which will be swapped to 3.42s after this season.

But as I mentioned, not really concerned with my build as far as this thread goes. I'd like to discuss aftermarket TPI vs. factory TPI for the 305. Curious to see the results other LB9 owners have seen with SLP, Edelbrock, AS&M, etc.

Azrael91966669

the best mods for a 305 would be lose the peanut cam and install something better like a lt1 cam i went down the 305 road and would be still playing with one had i not found the zz3 for super cheap

the stock tpi unit for the most part works just fine on a 305
it was designed to make a 305 feel like a 350
just doing mild porting on the plenum and removing the wall behind the throttle body seems to be all you need to do to have all the flow needed for most any 305
i mainly played with timing and fuel pressure to pull more from my 305

i would ignore the tpi for now and work on something like an lt1 cam then add 1.6 roller rockers
then replace the rear gears to something like 3.23 or 3.42

sorry just read the last part about ignoring your build
i have a super ram plenum just begging to go on my zz3 lol
but i really prefer the look of the tpi

to me it seems like the zz3 cam really compliments the tpi
sure it could make more power with a lt1 intake or superram but it still pulls rather well
for basicly being a l98 with a cam swap

ASE doc

As a major proponent of TPI and having built a few, I would say that the biggest power limiting factor in these engine is the cam and cylinder heads. Even the stock runners and base with opening up of the runner CSA, will support 350HP with good heads and cam. If you have lost some performance by installing larger runners and base, it is because you have created a pressure differential where air velocity through the runners is now reduced and the cylinder heads and valve events are not aggressive enough to make use of the increased runner CSA. A better cam should bring immediate improvement, but head porting or a good set of aftermarket heads will really wake up the motor.

I do not see any benefit from siamezing the runners in the TPI base, unless you are using SLP or other siamesed runners. I port the base for maximum CSA and match the runners to the intake ports of the cylinder heads. By pushing the cam duration and lift, along with hi flowing heads and the right engine combination. You can achieve good drivable torque and an engine that screams past 6,000rpm.

Remember, because the 305 is a smaller motor, it wants to make power in a higher RPM range than the 350 or larger motors. Therefore, to make the most of it, you want to increase valve duration as well as lift. The Lt1 cam is a start but remember, there are several "LT1" cams. The smaller grinds aren't so great. The largest of the group is a 215/224 @050 with 470/490 gross lift. This would get you going.

PhoenixFirebird

iTrader: (2)

Now we're getting somewhere

Over the weekend I spoke with one of the guys I race with, who has been racing 30+ years now, and owns a speed shop. He said exactly the same thing. The larger intake and runner ports are killing the velocity of the air, because the cam and heads are most likely the limiting factor now. Bigger isn't always better.

Now, how does this compare to an L98? Naturally the aftermarket parts would go farther just because of the extra cubic inches, but for the sake of discussion, just how much more efficient is an L98 compared to an LB9? It looks like we've established that the TPI components on the 305 already flow enough, and the heads/cam are the limiting factor. What about the 350? Is it pulling enough that instead, the TPI components are limiting the 350 as opposed to the heads/cam? I'm only leaning to this conclusion based on the many reports of instant x hp gains from aftermarket TPI out of the box, and even moreso with porting. This brings us full circle, is the TPI aftermarket based on 350+ motors?

As a side note, I pulled the ported runners and plenum off last night, and stuck the stock parts back on. I left the Edelbrock base on, just because I didn't want to mess with draining the coolant, disconnecting fuel lines, re-setting the timing, yada yada yada, when I'm racing tomorrow. I also figured the geometry of it would act similar to an H or X-pipe in exhaust systems, where it evens out the pressure of the two pipes. Fingers crossed anyway.

I didn't want to talk much about my build in particular just because it's getting pulled this winter anyway, in favor of an L98. No way am I ditching TPI, I love the look! Thanks guys, keep it coming!

fasteddi

iTrader: (2)

I'm not a TPI guy here but I have to add my opinion since your a friend.

Think about this, one good mod may hurt the cars preformance when added to the car alone. But when the car mods are paird up together, that one mod will compliment the next and the next and so on.

Mod parts are only as good as the rest of the things in line or that are related to them. Restriction after restriction such as you cam, heads. Thankfully you already have the exhaust taken care of. And the tuning you can also take care of.

A engine is nothing more then a air pump. Air goes in and then goes out. The amount of cfm your engine can chug along is a good idea of what it will produce. Of course there spark and fueling to go with it to make that happen but you have the ablity with the tuning equiptment. Its complicated but yet its not you know what I mean?

You must prove that the problem wasent a underlying factor or a problem you accidently did when replacing the top end.

Since you've been having so many issues such as your car randomly stalling out and other problems along the line, just put that other stock intake back on the car, then see what it does.

Let us know what she does with the stocker back on it ok?

yaj15

iTrader: (3)

I've seen the mods that you have done to your car Eddi. You know what you are talking about, thats a very fast reliable car that you have and then on top of that it's a V6.

With cars (more specifically now with the newer fuel injected cars) the system of matching compoents for what you are trying to do will usually give you the most satisfaction.

For example take a stock V8 Camaro RS and compare that to a Z28 or IROC.

With the L98 cars you would get a positraction rear with disk brakes and from '87-'89 you could get the stronger 9bolt rear. The base V8 cars got the standard disc/drum setup and no positraction. Some of the Z28's and IROC's even got aluminum drums.

The cooling system is also upgraded compaired to a base V8 car. The exhaust system is also significantly larger. Just ask owners of the V6 Camaros, L03 V8's or LG4 V8's how much the performance improved once they put L98 TPI exhaust parts on or got aftermarket equipment.

The shocks, springs, bushings, sway bars, etc. are all also upgraded. Yes you will get gains depending on what mods that you do. You can also lose performance if the parts don't match your current set up to. For example, there would be no need to install a 58mm throttle body on your current setup. The power that you have now isn't high enought to where the stock 48mm throttle body is a restriction.

Just by compairing the RS V8 cars and the Z28 V8 cars you can see where GM tried to up the performance by rounding out and improving the overall package. Not just looking at one area.

You will get good gains from your mods, especially when entire systems are changed from stock such as the intake and exhaust. I agree with the other positing though that stock LB9 peanut cam has to go. Even stepping up to a stock L98 cam will really wake up that LB9. Steeper gears are going to make a big difference in performance to.

Street Lethal

iTrader: (16)

With the stock Tuned Port Injection system, I wouldn't go any larger than 327 cubic inches of displacement. Once you reach 350 cubic inches you would need to siamese the system to help keep the volume of air on par with the engine's demand, unless your running a very small camshaft. If you can't siamese it, but you want to maximize performance, then ditch it and go with something else. Think of every aftermarket TPI system out there installed on a stock 350, the larger they get in diameter, the higher the RPM potential, immediately followed by a leaner air/fuel ratio at lower RPM if you don't touch the tune. This is because velocity and volume are increased. You will always hear how people who install a Holley Stealth Ram cry about losing torque down low, when they reality is, they didn't lose anything, they are just running leaner down low and need to tune for the additional air. The torque not only comes back after you tune it, but RPM potential is also increased substantially, and more RPM means combustion at higher engine speeds, in turn allowing for a lot more cam. The idea is to allow for the engine to "draw" from just the right amount of air that it needs with absolutely no obstruction. Think of this drawing of air being taken from a reservoir of air, too little of a reservoir (small plenum and throttle body) for the displacement and you will choke the engine up top, too large of a reservoir (big plenum and throttle body) for the displacement and you will stumble down low. The engine needs symmetry...

PhoenixFirebird

iTrader: (2)

Well I can't really give an input if there was an underlying problem, as the stock parts came back off. I left the Edelbrock intake on because I'm racing tomorrow, but that turned out to be a mistake. The stock runners come to a V-shaped point in the middle of the lower ports, to where it meets the intake. That part is ported on the Edelbrock intake. Imagine a flat line, that's the top of my intake ports. Then imagine a V where the runners connect. The only thing seperating that triangle and a huge vacuum leak is a gasket. Well turns out, the gasket wasn't enough. Couldn't even keep the car running. So back off with the stock parts, back on with the SLP runners. I could have swapped the intake off tonight, but I wanted to race tomorrow, and with only a few races left in the season it seemed dumb to pull it now, when I'll be doing a complete teardown in the winter. Also, my Torx bolts are about shot. Many have been replaced with allen heads, but I'm running low lol. Waiting until tomorrow after work to start her back up, give the RTV some time to set up. Anyway...

This is exactly what I was looking for in this discussion.

It seems that without a full combination build, aftermarket TPI parts on a 305 are going to set you backwards. Of course, a full combination helps any motor, but how do 350s react to just aftermarket TPI components? Like I said, most of what I've seen is "gain, gain, gain."

fasteddi

iTrader: (2)

Hope it goes well at the track. I still think you should put the stocker back on at one point as you were having some really weird ittermitten problems at one point since you've had the aftermarket top end on the car. It screams vac leaks the way it was idling or your tune was just that far off.

Robs dead on with the input. As depending on the mods you do the fueling is considerbly a huge part of the power gains or loses you will see.

My cam and ported heads/intakes made the car very rich down low and vert lean up top. The car felt faster as it was but once it was tuned properly the gains were much more then just the mods alone. For example my intakes and such caused the car to idle at 12.x when I finally got a WB on it so your eyes would bleed..LOL and up top it was clearly over 14.5+ afrs over 4k rpms=no added HP and way to lean.

Same process happends with exhuast on your car. She may be faster up top then down low. The powerband will shift up since it looses backpressure for the Tq off the line but will gain the HP band up top since it can breath better with higher velosity air flow.

I personally think you need that WB 02 sensor on that car and then a proper tune before you tear the car down for the winter. ITs time to get your feet wet in tuning and go with the AFR tuning. You may be amazed at the AFR's that your running right now. That narrowband doesnt cut it no matter what anyone says about them, exspecially in WOT tuning.


As for what others see with a 350 mods=gain gain gain... I still believe you have some issues with the car either be it tuning or a problems with the engine itself. But just adding a intake alone on any car will only help so much. Ive been reading about your tpi and the larger 350 and its looking like your having the same problem as I had with my V6. The heads and the cam is just junk and needs to be modded. You need to pay attention to those areas first because from "what I read" your intake isnt the big restriction and HP killer on your car. Actually your intake will flow quite a bit. So focus on the areas that are first. Cam and heads. Port those heads to the max and the valve guides. Im sure with proper tuning you would be amazed on the increase in power.

When I get back from work Ill link some of the interesting threads Ive found about the 305s and mainly the restrictions. Pros/cons of the intakes.

ASE doc

fasteddi said it right. I forgot to even say that an engine is a system and it was designed at the factory to serve a certain function. By changing part of the system, we may see some gain in performance in a certain area but generally, we lose overall performance. I always approach an engine as a system when designing a power system. This system at least has to begin with heads and cam. Better yet, it should begin with a rock solid bottom end with quality machine work and forged parts, then proceed with top end power building.

You have already invested in good intake parts. Now to see the gains available with those parts, you need to look at the rest of the system. A few people have touched on tuning. With the added flow you will achieve when you put this system together, you will definitely need to revise the fuel map. The spark map will also reveal additional gains by optimizing the full load advance curve.

PhoenixFirebird

iTrader: (2)

Not focusing on my car, I'm wondering why everyone sees gain gain gain on 350s with their aftermarket out of the box. Keywords, not focusing on my car

Again, I want this to be a general discussion, not focused on my build exactly.

But, as far as my car goes, I doubt there's any major underlying issues. Mark, we've already touched on the leaking injector, but like you said, it's not anything major. As far as my system goes, I would be looking at air, fuel, and spark problems. As you know, I added quite a bit of fuel all around, as my car was previously going down the track lean lean lean, and everything pointed to lean. That rules out fueling. I'm seeing rich areas now (through BLMs/INTs and Narrowband, but that's beside the point), so my fueling is closer than before. I can rule out spark, since I wasn't seeing the problem before, and my ignition is almost all brand new since I've owned it. That leaves air, which as a few people have said, is most likely the problem, caused by less velocity. I can't confirm this since my complete stock system isn't back on, but that seems to make the most sense as of now. As far as tuning goes, I'm still a beginner, you know that. I've been burning chips for about 4 months, and I know enough to add/remove fuel, add/remove spark, etc, amongst other things, and as far as the intake goes, that should be all I need to focus on. I'm working on getting that Wideband in, but our welder is being "rented" out. Like you said, maybe we can fix that up this weekend.

Anyway, less about my car

Does anyone have comparisons of stock 350s to aftermarket TPI-only 350s? Comparing to mine it'll be skewed, because my parts are ported, but just interested to see what others have found.

fasteddi

iTrader: (2)

I know its searchable but your TPI was designed for a 305. Thus from what I read the 350 is choked up a little by the TPI intake and many other things to boot.

Just a hair of what a search would say. Sorry to be that guy but there is a ton of info out there on this concept as even me a idiot on V8's can find the stuff. SO if you gain no info on this thread then search buddy. Thats how I yelded the most info on tuning specifically in my case. Also I believe that if you were comparing intakes on 305's only you would yeild better info on your mod. Rather then comparing what a intake would do on a 350.


Quote "The TPI was originally built and sized for the 305 and was used "As is" on the 350 except for the addition of 22 lb injectors for the 350 engine. This was done to save money. The cost of a different part for a 350 could not be justified by the bean counters at GM. The TPI was so superior to the old "crossfire" system on the 350, that the difference in the two systems was startling to say the least. It was hard to say what would have been possible if a higher airflow capacity TPI had been built and used on the 350 HO engines. A lot of our troubles would have been eliminated!"

Just have to say it but there is still somthing wrong with your car, you need that WB on here to get a true reading of afr's a NB is worthless in my mind. You havent tuned yet till you get on the AFR's then you'll gain so much knowledge as your be burning many more chips. I've bet I have burnt way over 1000 or more chips in the past 10 months. Rob, eaglemark, and anyone else that has been part of my threads can attest to that..lol And believe me man, I know $59 like the back of my head and the way my car will react to chip mods like clock work. This is only though if the car is in proper shape. If its not then your can throw the tuning out the door as its just a bandade for the true issue.

ASE doc

As far as comparing different build results using only hi flow intake parts is concerned, I have seen only marginal gains where the build did not include improvements to head flow and valve duration, height.

Again fasteddi said just what I was thinking. You need a wideband AFR meter. The narrow band PO2 sensor in your INT/BLM fuel managment system can only see between 14:1-15:1 AFR. Beyond that, it will read either full rich (>.800mv) and try to remove fuel or full lean (<.200mv)and try to add fuel. You can not see 12:1 (which is generally considered about perfect AFR for full power) on a narrow band O2.

Reid Fleming

iTrader: (2)

I think you're overstating the gains on TPI cars that come from aftermarket parts. I see this for two reasons.

1) Most advertisements show huge gains on cars that are 300-350 HP stock TPI vs HSR vs SR, vs MR etc. Well sure, you're going to get a huge boost in power when you do this. But for the average guy who's just changing one of two things on a stock setup, the gains won't be nearly as significant.

2) Even modest pieces on our cars are over advertised for HP gains. 20 HP gain with a Big Mouth intake on a stock 350? 95 HP gain with a MiniRam on a stock 350? I don't think so.

In my case, I went with an Accel intake and a ported SuperRam when my head gaskets needed replacing. I was expecting a nice noticeable gain.....I got a barely perceptible gain from 3000 RPM up. And below that, seem to have lost power to the stock TPI runners. Although I have 22 lb Bosch III injectors, I have to run 57 psi on the fuel pressure to get the car in the BLM 140 range. Otherwise it's too lean.

I have everything opened up as far as air going into the engine. And 3" high flow cat and 3" GMMG exhaust. (I don't have headers). But my car only put down 228 HP on the dyno. (Granted, this was on my original stock fuel injectors 3 weeks before they went out and I was only running 50 psi) But you get the point. I'm not making huge power right out of the box even with the aftermarket stuff on the car.

Those 2.77 gears will hold you back though..... I've run 2.73 and 3.73 gears on LT1's as well as 3.27 and 3.45 on L98's. The 2.73 gears on the LT1 made the car a real drag at slow speeds. It was only at about 70-100 mph that the car felt strong. That area where you wound out 2nd gear.

3.27 or 3.45 gears will work perfectly for TPI. I feel the 3.73 is too short for a TPI engine though. You zip through the torque area too fast and fall into that low HP upper end that our cars are known for.

Azrael91966669

the 95 hp gain is at 6000-6500 where tpi power is down its not add 95 hp all over its more like its now at 280hp where it was down to 185 before thats just the example
the miniram makes a tpi car pull like and lt1 but it needs tuned to work just as the super ram needs tuned aswell
but yes in all honesty the claims are over rated

the reason there is gains with a 350 out of the box is its bigger and suck in more air and push more air out


a tbi 305 makes 170 hp 255 tq
a tbi 350 makes 210 hp 300 tq both useing the same cam and compression

a tpi 305 makes 230 hp 300 tq
a tpi 350 makes 245 hp 345 tq both using the same cam
the reason of the tpis hp being close is the tpi was made for a 305

if tpi worked good on a 350 you should have seen the same hp increase that the tbi engines showed
ie should be around 270 hp and 345 tq but instead of the big hp increase you only see a tq increase form the extra cubic inches
ie thats where the lt1 intakes/ mini rams they are made for a 350 and let the engine breath uptop