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TPI or not?

7K views 60 replies 13 participants last post by  OneMoreTime 
#1 ·
Ok guys. The 350 in my Model A is getting pretty tired. One of the guys in our club has a 305 TPI engine that he replaced with an LS-1 that he will sell reasonable. I'm not going drag racing and dont care about 4-500 horsepower. All I'm looking for is decent power, reliability and decent fuel mileage. Do I put in the TPI or another carburated 350? Why?
 
#2 ·
Why fool with something that has stood your test of time. A carbed 350 is just fine and as reliable as a rock. Does it have that fancy EFI, no, but it has a lot less wires and computers to go South at the worst possible time.

Also, winter comes every ear and a rebuild on your existing engine can work well too if you have a decent machine shop locally
 
#3 ·
I agree completely with everything except the wiring/computer issues. EFI is way more reliable than a carb ever thought to be (IMHO:thumbup:). But IC is correct, having a quality rebuild done by yourself or a local machine shop, or buying a crate, is a better than OK option. And just as cost effective as installing the TPI setup you're talking about.

305 and tpi suck. It would be two bad things you will eventualy end up hating.

The ls is the way to go for sure your buddy is very happy im sure. The 6.0 out of the escalade is awesome stock no need to do a damn thing to it. Also the little 4.8 is cheap and runs good im told.

Carb over tpi anyday. They need major work as time gpes on and make almost not power. At some point its frustrating to work on the slow solution. Is it free? Maybe but i would go carb all the way. Most tpi guys are pulling them these days for carb manifold and fast efi or just the carb.
Disagree. TPI's don't suck. TPI's make phenonemal low end torque, even in the 305, and if driveability is a concern, then it'll slap the poop out of any carb setup. And even though it is an ECM driven setup, it is about the most basic multiport setup out there. It is not a ton of wires on the engine and all can be contained within 2 strips of 1/2" loom from the rear of the intake to the front of the intake. Getting the stock ECM running is more of a chore than anything else. Would an LS be better? Damn straight, but get ready for the do re mi to start building.
If you goals are straight line go, which you mentioned they aren't, then a 6.0 LQ9 is definitely the way to go. If mileage and driveability are your main concern and you want EFI, then grab the 305 TPI and chuck it in there. If budget is a concern, then buy a crate and spend your money on pretty dress up stuff to keep shiny.

Best of luck - Jim

p.s. - I'll never, I think, build another motor to be driven on the street with a carb again, unless it's a Nailhead. SBC says 'EFI needed' to me.
 
#4 ·
If it has the TPI on it I would go with that.. My truck runs much better with the injection than it ever did with a carb and that is on a utility truck just for hauling stuff and not to impress anyone at the car show. that is until they need something hauled or moved.. :pimp:

Sam
 
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#5 · (Edited)
The l98 is one great engine combo for low rpm engine. But its still a turd. And needs constant attention.

Then fix it. If it needs rewiring, which is shocking for 25-30 year old wiring harness, then fix it. It's basic wiring skills. Buy a solder gun and solder for $50 at Lowes and get to it:D

I dont mind carb tuning once its done right its good to go. Efi always needs a new sensor or injectors or something. Now mine has 300k on the car but everything has been changed several times before i got the car. 30k worth of repair reciepts to keep this thing running with tpi. And a lot of other stuff that is not tpi related but it had its share. Cant see spending 30k on carb parts.

WHAAAAAAAAT! 30G's. I can't buy that unless I'm a bar fly and drunk.:):)

The LS is worth the effort it takes to run the efi that is why i recommend it. Nobody hates the efi ls setups onces its built. They also get better milage than the tpi for the power output. Tpi 305 is thrifty. Until you got to buy parts.
Agree with the LS, it's just that there is quite a money difference between putting in a stock TBI or TPI vs the LS. And if you're 305 is running out of go at 4K then it's broke. The stock TPI will run great to 'til between 4800-5000 rpm's with a 350 and definitley all of that with a 305. I'd say your's is broke - again - fix it.

Remember how the OP started this thread. He wants reliabiluty with no concern of drag striptimes. IMO, he won't find anything that will perform better than the stock TPI below 3K (which is where alot of people spend the bulk of their time for cruisin' cars.)

OP - what's you're budget and abilities? Like mentioned previously, if you're not a wiring guy, I'd go with a crate and the carb, but if you want a challenge that'll pay off in the end, then go with the friend's TPI.

HCompton - absolutely no sarcasm or put down intended. I just love the multiport setups for efficiency and tuneability and I'd rather see them promoted as viable options rather VooDoo.
 
#6 ·
Ignore the TPI bashers. I've never figured out why there's always a few on this forum who go out of their way to bash them. I've owned a lot of cars in the past 45 years and my 62 Vette (see avitar) with L-98 and 6 speed ZF is one of the most enjoyable ones to drive yet (yes including my LS1-6 speed 59 BelAir). TPI is simple to wire, 25+ mpg and rock solid dependable. the torque is enjoyable and makes a double overdrive effortless as well. the fact that it's such an easy swap with any gen 1 SBC is a plus also.
a 350 version would be nice, but if the 305 is a solid engine that's ready to go DO IT. you won't be sorry.

Russ
 

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#7 ·
Honestly, if you're going to be like hcompton, then don't do it. Otherwise, go for it.

There is zero reason to have problems with a TPI unless you do something stupid to it or just hate the thing. Otherwise it's a nice, simple, reliable setup that will get decent MPG and performance. It's also one of the coolest looking intakes that GM ever made. All that said, it's only major disadvantage is the multipiece intake, a plenum, 2 sets of runners and a base, all that bolt together with the fuel system and various goodies under the plenum. I've never seen one leak, but if you want to change something you do have to unbolt the intake in parts to work on it.

FWIW, this is my current project at the track last fall, this is a stock, 120 some thousand mile (the valve guides/seals are worn out so it's blowing some smoke), 87 LB9 (305 TPI) with nothing done to the engine besides headers and exhaust (I've dissasembled that engine this spring and confirmed it's all stock inside, a little worn out). I did have the coil wire popping off that day (you can hear it missing in the burnout box and won't rev), but it still ran a 13.622@99.89 in a 3580# car:
https://youtu.be/4oHsc2_YNMQ

That's really not too bad for a high mile engine that averages in the mid 20mpg range.

The thing to note about TPI setups, everyone says they're a low end setup, they're not, the runners are tuned for a solid midrange (the 305's make power from about 3500-5500rpm, the 350 from about 3200-4800rpm). GM stuck TBI setups in the trucks that needed low end the same years as it used TPI in the corvette/camaro/firebird. If you want one to run reasonably fast with an auto you'll want to stick a 2800-3600rpm stall converter behind it (if it was mine I'd use a _good_ 3400-3600, but if you're not going to spend money on a quality converter than a stall that high will hurt around town drivability with a cheap converter, mine is a 5 speed, and I launch it much higher than that)
 
#8 ·
Thanks for all the input. I'm not against carburetors I just think polished TPI units are nice looking. The car is nothing but a cruiser and doesn't see 3500 rpm unless I decide to beat on it a little which isn't very often. The thing cruises down the highway turning 1900 rpm at 70 mph all day. I thought about an LS but don't think it would look very nice, exposed as it is, in my Model A. One consideration is that if momma decides she wants to take it to the store the thing needs to start and run reliably without tinkering with it. Seems the comments are pretty much 50/50 with mostly the performance guys against the TPI. Im not afraid of the installation or wiring as I've been around this stuff all my life. I'm pretty sure that by the time I get the TPI installed and running I could have bought a brand new crate for the same money, maybe less. I just wanted some other opinions as to what other guys thought. Thanks to all for your input.
 
#14 ·
Thanks for all the input. I'm not against carburetors I just think polished TPI units are nice looking. The car is nothing but a cruiser and doesn't see 3500 rpm unless I decide to beat on it a little which isn't very often. The thing cruises down the highway turning 1900 rpm at 70 mph all day. I thought about an LS but don't think it would look very nice, exposed as it is, in my Model A.
The stock TPI with the runners polished (and the finish on them is close, it's not much work like polishing cast aluminum pieces) with the plenum painted, matching valve covers... is one of the best looking combinations out there.

Not that I see why people keep bringing it up, but the LS engines are just ugly, and there isn't really much that fixes it till you get into the big $$$ aftermarket intakes and mess with relocating the coils. I can't imagine anyone actually wanting on in a 'rod.

One consideration is that if momma decides she wants to take it to the store the thing needs to start and run reliably without tinkering with it. Seems the comments are pretty much 50/50 with mostly the performance guys against the TPI.
99% of mommas like TPI better than a carb
;-)

and I'm a performance guy that knows my way around both, and in most cases I'll choose TPI (and in almost ALL cases I'll choose some flavor of injection) over a carb.

Beware of the factory oem harness its probably long since past its prime. A total rewire if it hasent been done would be in order.
You know, Ive owned a few 80's/90's GM vehicles (2 TPI's) and worked on a lot, and I've never seen one with a messed up harness/problems with the plugs unless _someone_ messed them up. Similar vintage ford stuff can be a disaster.

If your happy with the 190 hp to the wheels then its probably the option for you.
A nice 300 ftlbs is totally possible. But once you try to get some more power everything will be in your way and need to be replaced. So stock tpi or carb nothing makes the tpi work for performance.
factory ratings were up to 230hp (and that 230 would have been more like 300-350hp in the 60's). The differences were different cams and exhaust (there were other differences by year but they shouldn't affect power output). As long as it's not a "peanut cam" variant (there were some with auto transmissions in the later years that came with a dinky cam, if it's one of those I would recommend swapping the cam _no matter what_), adding headers, a good exhaust and intake/filter assembly will put that solidly in the 275-300hp range with ~350lb/ft torque. Lots of those cars as rods are pretty light, in the mid to high 2xxx# range, that's enough power to run a 12.0@114mph in the 1/4.

With a carefully chosen combination, the STOCK TPI parts flow enough to support 400hp (it's not as easy to do as just picking a random "3/4 race cam"... but they will do it), and that's a high 10@125 in the same car. Yea, you don't see it often but it can be done.

. As mentioned, flat cams till '87. then roller cams of various sizes in various years...
Roller in '87

they also switched from MAF to MAP EFI about '90... the TPI acts like it was designed more for a 305" than a 350"... HP peaks around 4500-5000 RPMs on a 305", but peaks about 4000-4500 on a 350"...
you'll get your fastest runs shifting a 350 at 4800-5000rpm, 305 from 5200-5500rpm (I have both in the driveway right now, and I run _everything_ at the dragstrip)

While the TPI 350" wasn't a revver, it did effortlessly push 'Vettes and F-bodies to 145-150 MPH... prolly about 5 MPH slower for the 305" version as HP wasn't much lower, just less lower RPMs torque...
When I was younger and stupider I got pulled over at 148mph in a very lightly modified 305 in a trans am, The cop actually showed me the reading on the radar gun in case I didn't believe him...
 
#9 ·
the box stock 305 tpi in my WS6 ran great. I added the corvette/ZZ4 aluminum heads and had someone delete the EGR code in the computer. Truthfully I dont notice much difference by seat of the pants power wise. It sounds a little different, and you can definitely notice the difference handling wise with 40LB off the nose.

I love the looks of the TPI and daily driver aspects of it. If your buddies 305 is a roller cam motor, you could certainly stab a cam in there if you really wanted to; but theres no point.

If he has a stand alone harness, you might be lucky and get out of it for a few bucks. You'll probably need a new fuel pump and you'll want to make sure you can clear the firewall in your rod. The corvette got an aluminum distributor cover, the F bodies got a grey plastic one. If you did want to try your hand at polishing, you'll want to find a corvette one and polish that to match.

Get a list of everything your buddy is willing to throw in for the swap AND what programming and things hes done. Also, is it a roller cam or flat tappet block (roller cam started in '87) We can help you get a clearer picture. There are several guys who fly the TPI flag here and we can certainly point you where you need to go.

My ex drove the WS6 daily in the summer; so if Momma is driving it, its a thought.

If you're going to go carb crate motor; the 2bolt vortec 350 long block is great. Its right around $2000 and you need a used vortec carb intake, a distributor and a fuel pump along with the front dress and carb.

Tons of cruise power, rock solid and dependable; but it looks like every other street rod crate 350 LOL
 
#11 ·
here's where you get more info on the different TPI versions/years and how to best set up each variety. take a look at the ECM pinouts page for your engine and you'll see that it've very easy to modify the oem harness to work for you, which also saves a bunch of money. I'd recommend you get a NEW prom burned for it. several sources do that for a very nominal fee. no tuning required on your part at all, unless you decide to swap cams etc. they are plug and play.
Chevythunder
 
#12 · (Edited)
. As mentioned, flat cams till '87. then roller cams of various sizes in various years... they also switched from MAF to MAP EFI about '90... the TPI acts like it was designed more for a 305" than a 350"... HP peaks around 4500-5000 RPMs on a 305", but peaks about 4000-4500 on a 350"...

. HP on the TPI 305" and 350" was very similar, but the 350" gave mainly a noticeable boost in lower RPMs torque... yet the 305" feels sportier with it's higher RPMs range...

. While the TPI 350" wasn't a revver, it did effortlessly push 'Vettes and F-bodies to 145-150 MPH... prolly about 5 MPH slower for the 305" version as HP wasn't much lower, just less lower RPMs torque... although the TPI 305" may feel as torquey as your carb'd 350", depending on which 350... 1970's design carb'd 350's were very wimpy...

. The power graphs in this article show how TPI HP curves go flat as a pancake at 4500 RPMs and above on larger engines... the stock TPI cams HP peak about 5200 RPMs with a carb'd intake and carb., so, obviously, no reason to go bigger cam with a TPI since you're just giving up low RPMs torque and MPG and the HP curve isn't going above where it is by 4500 RPMs even if rev it to 7,000... because of the 25" long intake tracks... which favor low to mid RPMs torque/MPG...

http://xtremecarzone.com.au/index.php?showtopic=386


(I have an '87 GTA TPI 350" automatic)
.
 
#15 ·
I have a Corvette book with an interview from the guy who developed the TPI.

Chevy Brass dictated the Corvette would get the 305, so the TPI was developed for the 305. Once it was all done the Brass realised they would be stupid to drop the 350 from the Corvette for the 305, so the 350 got TPI optimised for the 305 and the design Engineer was fuming.
 
#18 ·
Most people who don't like a TPI setup are either wanting/needing higher RPM power,or,they simply don't understand TPI,or,EFI probably for that matter,or.....& is true in alotta cases,they only know what they've read on the internet about them,which,for the most part is total BS.
The Vortecs do support more HP than the L98 heads by a lot.Prolly 50 to 75 HP,or,so.Scoggin/Dicky has a Vortec/TPI base that allows the use of Vortecs with TPI.
 
#26 ·
. True... even GM did that... most of the cams they used wanted to HP peak around 5200-5500 RPMs, but the stock TPI blocked anything above 4500 RPMs... and the stock base exhaust system even lowered that... more MPG and torque would prolly have been available with a smaller duration than stock cam...
 
#27 ·
Here's a dyno of my 350 TPI.
This is at the wheels.
You can see how it indeed runs out of breath as the torque and HP do not cross at 5250 RPM's.

The torque is the great thing and it pops nice off the line in my 4500# truck.
It gives 20 MPG (Imperial) and oh so nice to drive.

 

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#35 ·
My TPI is going to become an ornament some time soon.
Sure it looks great, so will get pride of place amongst the shed art and surely will be a great conversation piece, and maybe make it onto a sbc in a pickup or rod, but in my vette aint where its meant to be.
Great for a truck or a rod or cruiser, not in my vette though.
 
#36 ·
I've got the -113 heads on my TPI; its great for what it is in a street car. Would I drop $600 for them like I have seen on eBay? Hell no! But, I got mine off a ZZ4 for great money. It had only been run for 1 cruise season and the owner stripped them off for more performance-oriented heads. One thing about them is the small runner size, so yes they'll run out of steam early, but there are some benefits if you plan the engine accordingly.

However, you can get an OEM 58cc Vortec head that flows similar to the small valve "fuelies" from half a century ago.

If I had a fair amount of play money; a 305 TPI with 58cc Vortecs, ported base and tubular runners would be interesting with a 5spd in a light car; assuming I had the ability to tune it properly. But by then, you're in LS engine territory.
 
#38 ·
A bigger throttle body, larger tuned tubes or a conventional open plenum manifold modified for the injectors, some higher flowing injectors, bigger cam, a mild amount of porting in the L98's passages plus a little reprogramming and you can shove a TPI L98 well onto its way to the mid 300 horses and keep the RPMs around 5400 and holding a pretty flat power curve up to about 5700 RPM having a torque peak out a shade under 400 ft pounds at less than 4000 RPM without going backrupt or busting a sweat.

It's a decent enough street motor with the right massaging.

Bogie
 
#39 ·
Gotta be careful your not flogging a dead horse with TPI upgrades. Can only go so far.

For about the price of upgraded runners and throttle body you can go to a good EFI single plain or a plenum manifold like stealth ram or pro flo xt.

As with anything you need to decide what you want. Personally I'm just going with an EFI Single Plane running the TPI computer and be done with it. But I am looking for a 7k redline.
 
#40 ·
Some people can't get rid of the TPI intake manifold. Those people are left with a few options: 1. Move out of Cali, 2. Stop hotrodding 3. Modify the existing runners 4. replace them with tubing or AS&M type runners

There are guys on ThirdGen.org that are really cranking some power out of a TPI system. The proper headers, the proper Y-pipe and better runners and throttlebody are keys; along with learning the ecm programming (which seems very easy).
 
#44 ·
305 = POOP
TPI = POOP

305 + TPI = BIG HEAPING PILE OF ****.

Find a 5.3 complete take out, from a 2 wheel drive truck and be done with it. Guys arguing TPI's are just mad because they have sank so much money into them. I don't care what anyone says, they are junk. I have personally pulled one of these turds out of an 89 IROC and installed a cam only LS1. I can tell you that the guy that owns the car is VERY happy.

You can put a stock LS1 intake on a 5.3 truck motor very cheaply. Install a small cam and have one very strong little motor.

I would rebuild your Carbed 350, find another one, or make it a 383, before using a 305 TPI.



 
#48 ·
Not really, I still like the SBC, hell I just built a 383 and put back in my truck, could have went LS, probably saved some money but the truck was already setup for the SBC.

I spec'd out a carbed 350 for a buddy of mine, to put in his 67 Camaro. Replacing a tired old 327. RHS heads, custom ground cam, single plane, 700R4, Ford 8.8 with 3.73 gears. I helped him tune his carb with my wideband 02 sensor and got the car running damn near as good as a FI car.

The original poster was asking about a TPI swap. If he was going to go through the trouble of wiring in a fuel injected engine, there is no way I would be installing a 30 year old TPI motor, especially if its a 305. Complete LS 5.3 2 wheel drive take outs are getting as low as $800, complete with wiring PCM...etc. The whole thing. Coil on plug, sequential fuel injection, better gaskets...etc, lots of reasons to use them...:cool:

My point is there are lots of options, TPI being at the bottom of the list, LS swap at the top, for simplicity, $$$, reliability and power. Everything else is in between.
 
#52 ·
I never said they werent reliable. Just that the LS is more reliable..:)

I own both. My truck is based off a TBI engine, and I have had distributors go bad, modules go bad, caps crack and corrode, same distributor the TPI uses. They are still good ol motors, for gear heads like me and you they are fine. There is no denying the LS is all around better. Why did GM go through all the trouble?

The LS uses nothing mechanical for ignition timing, and you get a 50K volt coil for each cylinder. If you ever get a chance to build one/take one apart you will see what I am talking about. Not to mention they all have steel 6 bolt main caps! None of the LS heads are bad either, they can all be used to make good power, unlike SBC, you pretty much need to buy a set of aftermarkets.

I am sure your TPI Trans Am is fine the way it is, not trying to dog out your car. I love thirdgen Camaros and Firebirds, I just like them a little more with LS engines in them...LOL:thumbup: The IROC above went from a 305 TPI to a mild camed 5.7 LS1, we put 3.73 gears in the stock 10 bolt. The car is convertible and is so quick it scares me to ride in it with him. I like to have a roof over my head if we end up, upside down in a ditch...:pain:
 
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