I have a 1991 Z28 5.0 TPI Auto with horrible 2:73 gears. Car is in amazing condition all original with 38K miles and has been recently gone thru and tuned up by me. The problem is it's so slow. Granted I have a 2016 Z06 to have a great time with but I need to wake this car up a bit. I would like to maybe gain an additional 100 horsepower conservatively. I do not want a 350 block. I do not want Vortec heads. I would like to keep the stock TPI. I do not want to remove the engine from the car. I do not want to get a stroker kit. I think my budget is around $5K in parts since I will be doing all the labor except for the gears installed which is about $1,000 from a local shop.

What heads and cam with supporting valvetrain items would you recommend?

Would I need to upgrade the injectors? Southbay?

I also plan on adding Yukon 3:42 gears with a small stall?

How do I get the Prom reprogrammed? I believe this is a speed density car.

I will also add headers going into my stock Dynomax exhaust. I plan on keeping all stock emissions.

Anything else I am missing?

The goal is to be stock looking adding a bump in horsepower. Nothing too radical on the cam.

Will the transmission handle the additional horsepower?

Please let me know your thoughts. I will do all the work myself except for the gears.

Thank You

 

To gain that 100 hp, you'd have to do all the stuff you say you won't do.

But whatever you decide, good luck.

 

So, what would heads cam headers and tuning get me?

 

Not enough. A stroker kit is probably out of the budget but a freshened up L31 core, budget aluminum heads, mild cam, little port work on the base and plenum with some high flow runners would be good. You'll probably need 24lb/hr injectors on a setup like that.

Of course, economical, conservative, and reliable would be stock so your expectations are all over the place. Start with a spreadsheet and plan your build out to the last detail.

 

Disappointment.

 

With his other car being a 2016 Z06 Corvette no matter what he does to a LTR SBC TPI engine it's going to be disappointment compared to that.

I think he might be happy if he could get it to a level that it would at least out run his old lady's minivan. This is a realistic expectation.

 

How did you know my old lady drove a minivan?

 

100hp gain on that 305TPI, $5K budget and not going deep into the motor doesn't match up. I do agree with not going deep into that motor and you can get closer to your $5K budget, make very real and noticeable performance improvements and not pull a valve cover or intake manifold.



Gears first. Best bang for the buck on that car. 3.42 posi is a good choice.

Exhaust next. That motor has the larger camshaft from 350TPI, but is choked with the single 2.25" exhaust system. Remove the entire exhaust system from the manifolds to the tailpipe and replace with a quality set of headers, dual converters and 3" cat back. You said you already have a Dynomax exhaust. If that Dynomax has a 3" intermediate pipe, then that's good, but most of the Dynomax crossflow mufflers I have seen neck down to 2.5" where the intermediate pipe goes into the muffler and the internal tubes in the muffler are only 2.5". OK to run that for now, but consider replacing with a true 3" muffler setup at some point. This exhaust setup will net you somewhere in the 30-40hp range.

There are also the other small fee mods such as removing the air intake silencers, bypass throttle body coolant, bump base ignition timing.

Just doing these things will wake this car up and make it a whole lot more fun to drive.

 

I don't kiss and tell. LoL

 

lol that was good

 

This is the way

 

I hate to be the bearer of bad news, butt...

You're not the first person to want to go down this road. Believe it or don't. There's probably HUNDREDS of disappointment stories on this site from people doing exactly what you say you want to do; inappropriate cams, heads that lower the compression, $$$$ gimmicks that didn't do diddly butt instead failed and left their car sitting by the side of the road somewhere, and all the rest. All of it is going faster only by way of weight reduction centered at the owner's wallet.

Keep your money in your pocket. Let the car be. It Is What It Is, and will never be anything else, given the ground rules you're setting yourself.

I think 30 - 40 HP is the absolute upper limit you can expect NO MATTER WHAT you do to that car as long as the 305 and the TPI are in it. (short of boost or nitrous of course)

The transmission will be fine, to the extent it is now, and that it's not wore out. Fiddling with the motor won't change that as long as it's still the 305 TPI. In fact, choose the wrong cam, and you could be making life EEEEEZYER on the transmission, by reducing the engine's torque.

Gears and exhaust will help it. Leave the motor alone. Don't touch it. Keep your money in your pocket.

 

The 305 probably limits you on cam size, since larger engines can get away with more cam w/o the negative effects of a rough idle. Nor would you want a much larger cam since the TPI would choke it off anyway. Which then also limits you on heads, which then begs the question of why do heads at all in that case, since the stock heads would be able to keep up with the cam size you're limited to as well as the TPI.

So given that and your other goals and objectives, I'd probably say ~20-30 hp at most.

I agree with what others have said... gears and probably a ~2000 rpm converter is probably the best bang for the buck.

 

Ok I get it. Don't touch the 305. Just do exhaust and gears.

What 350 motor do you recommend that's complete that would drop right in using factory TPI or aftermarket FI?

Thanks

 

A Chevrolet one. 87-up. Casting number either 683 or 880. With TPI heads (083 casting if iron, 113 if aluminum butt those get into other issues), NOT 193 or other TBI crap, NOT 70s smogger crap, NOT NOT NOT NOT NOT. 083 casting ONLY. Flat-top pistons with 1.56" deck height, NOT 1.54" "rebuilder" crap that lowers the compression. A TPI-specific ROLLER cam; NOT "350 HP 327", NOT yerbasic 929 70s crap copy, NOT NOT NOT NOT NOT; my choice would be either the Comp "302" or "503" grinds. It will need GOOD valve springs; NOT stock, NOT "Z28", NOT NOT NOT NOT NOT. I would strongly recommend better rockers than the stock stamped sheet rubber ones; preferably steel, such as either from Comp or Crower. THen there's abuncha other small parts that would just be boring to go into that much detail at this point.

As you can see, this is a motor you BUILD, not BUY.

TPI itself is the identical same for 305 and 350, in a given year and application. Only difference is, the injectors, the PROM chip, and the knock sensor. 305 injectors from the factory are 19 lb/hr and 350 are 22 lb/hr. Knock sensor is basically a little microphone, "tuned" to the specific frequency that a specific bore size makes, therefore different for the 305 bore (3.736") vs 350 (4.000") plus overbore in each case if necessary which is so tiny it has no material effect. Tuning is accomplished via the PROM chip which contains the tables the ECM uses to look up fuel delivery, spark timing, etc. from; equally obviously, different between the 2 engine sizes.

EVERY SINGLE OTHER PIECE of your 305 will bolt up to such a 350. Your water pump, flex plate, crank damper, etc. etc. etc. etc. all bolt up because the blocks are IDENTICAL IN EVERY WAY externally. Same size, all bolt holes all in the same places, etc. etc. etc.

Nice thing about this is, the 350 will need THE SAME exhaust and gears, down to the last part #, that the 305 will. IOW, that's all stuff you can buy for the 305 and see how weeeeenie it still is, and THEN transfer over to a 350, without having to throw it in the trash. That's unlike heads, cams, pistons, etc. etc. etc., which would need to be specific to the 305, and therefore would be money in the trash when you figure out that the 305 is a dead end. The 350 is bad enough that way about not being competitive with anything modern, after all it's a 1955 (end of WW2) design, butt the 305 is FAR worse, being a CRIPPLED version of that archaic design. World changing at the time; hopelessly obsolete in 2025, 70 years later.

 

Once you get some 3.42's or 3.73's in there, you may decide it's more than enough. The difference you'll see between that and 2.73's will be night and day.

With my Gear Vendors, I can switch back and forth between "effective" final drive ratios that actually mimic 3.42's vs 2.73's. Punching it in 1st gear with and without the GV engaged is the difference between pretty fast and frickin' out of control.

 

A blower.

 

IF it were me, I'd do headers, exhaust, gears, small converter, some free mods like TB coolant bypass, clean up the engine compartment, K&N filters, SLP runners, and maybe a small cam if you want to go into the engine.

Will gain you 50 or so and feel a LOT better

 

What power would this combo make and is that on the stock TPI?

 

With stock TPI, might get close to 300 at the crank.

That's kinda the problem with stock TPI. As long as those 22" runners are on there, you're pretty much stuck with peak torque at 3600 RPM, and a rapidly falling-off curve above that. It's almost not mathematically possible to overcome the limitations that TPI (specifically, the "Tuned" part of it) puts on engine behavior.

 

Kind of what i was thinking. Get all that stuff out of the way except the cam.

 

Thank you. Seems like a lot of money to get about 75 horsepower if I am already freeing up about 25 horsepower with the exhaust.

 

The $/hp gain gets much more the higher you go after taking care of the low hanging fruit.

 

Additionally, (to the runner length) the runner cross section is too small. In THIS INTAKE TEST (which was on a 350) every intake made more HP, TQ, and even "Low end tq" (to me, that's tq off idle; 1000, 1200 ish RPM) than the stock TPI intake made. So that intake is pretty limiting. Slightly less so on a 305, but it's limiting as SOFA has said.

I agree with the gears, exhaust and converter. I agree w/the guy who said headers/exhaust would get you 30-40 hp....that aligns with what I've experienced on F-bod full exhaust swaps. A do think a mild cam would help, and is high bang-for-the-buck, but it's a lot of labor. If you're doing the work for fun/hobby, I think it's worth it.

 

OK so here is where I am at with the build. I do all my own work in the garage, and it is a hobby to me.

Full 3" exhaust from headers back to muffler.
3:42 Yukon thick cut gears since I have the 2 series carrier with a mild stall say in between 2000 - 2400.

Get that stuff out of the way. Then build my 350 with intake or just drop a cam in my 305. If I did drop a cam in, what do you recommend?

 

Cool. Same here. I'm all about the HOBBY, and don't mind the work. The work IS the hobby.


I don't want to recommend a cam; to me, that's a "personal choice".

If you're asking 350 or 305 w/a cam, 350. More tork, more fun!

 

This thread hurts my brain. The title is "Economical Conservative Reliable Build" for a car that is "amazing condition all original with 38k miles".

The OP ALREADY HAS a car that meets the title of his thread. It is the same car sitting in his driveway in amazing condition.
Thankfully his insane goal of wanting it jet powered without the jet engine has been reduced to rubble, but it is now headed down the path that destroys 99% of all Thirdgens, namely the "mods".
Good grief man, you bought a Thirdgen Camaro because it is a cool 1980s car. All this talk about swapping cams, heads, cats, and such will lead you down the path of destruction. Before long you will have ripped out the A/C, all the smog stuff, thrown a carb and some crappy heads on it and turned it into the heap of Thirdgen junk we have all seen in our neighors back yard.
If you want to outrun your wife's inivan just drive the Vette. Drive your Thirdgen and enjoy it for what it is: a cool piece of history. Or, if the bug to modify a car is that strong, go get something already "modded" and fix it right.
I have two Thirdgen Camaros that I drive regularly. One has been slightly modified and one is bone stock. The stock, original one is MUCH more popular everywhere I drive. Even I like that one better, and I'm the one who "modded" the other one (actually, FIXED it from the previous idiots "mods").

 

I kind of agree, but I'm on the other side and bought a rough car cosmetically because I didn't want to mod a nice example. It has turned into a 6+ year long slog because it's really hard to get motivated to work on the car when after all the mechanicals are done it still will look like a **** heap with trashed paint and worn out interior.

 

I'm really sorry this thread has upset you. My goal was to have a stock appearing car with just a little more power that's all. I was just looking for some ideas to make it a little more fun to drive because it's extremely boring to drive. Maybe I should have rewritten the title to how do I gain some power to my 91 Z28. However, I did learn from this thread about what exhaust I have (a very restrictive one) I have also learned that maybe it's best to just leave the pathetic 305 alone and just put some gears, stall, and free up the exhaust or I could do nothing. Either way I do have my 2016 Z06 which is more fun than my Camaro and both your Camaros put together. Anyway, have a good day!

 

Thank you.

 

I really enjoy working on the car. I bought from the original owner who passed away. The car was extremely clean. Just needed to go through everything and replace what was needed because it sat for a very long time. I am very mechanical, so I don't mind doing that work. The interior was a 9.5 and the paint was an 8.5. So, it was a no brainer for me.

 

Don't listen to the haters. I wish I had started with something nicer.

 

It's all good. The car was exceptionally clean. Everything was original down to the tires. I put new BF Goodrich tires on, KYB shocks, changed all rubber brake lines, new pads rotors drums wheel cylinders, hatch and hood struts, complete major tune up with all the sensors, new exhaust from cat back since old one was original and rotted, sway bar end links and bushings, new radiator hoses, new battery, new AC blower thought the original was too slow, new heater core original one was leaking, new belt, and a bunch of other small stuff. Took me a few months working here and there. Also flushed all the fluids with new. I try to use AC Delco where available then I go to Delphi and so on. Last thing to do is change AC compressor since mine is leaking slightly. Its slinging oil on the hood liner. The car shows almost new. I invested about $4,000 which included the $900 tires in parts and God know how many of my labor hours. Did all the work myself except for the drum brakes which my dad helped me with. Also changed intake manifold gaskets since I had a China wall leak. Also did oil pan gasket and front main seal / timing cover gasket. Inside the motor looked new. Rebuilt the distributor since it looked like it was at the bottom of the Atlantic next to the Titanic with all the corrosion. Car is now extremely reliable. I drive it one time per week just really slow and boring. LOL