rice killer

I just spent months searching for the right third gen. I found and purchased a very clean Blue 1990 IROC-Z 87k miles bone stock. i have always had a love for third gen camaros and this is almost 100% perfect. I want to achieve a very reliable 300-ish rwhp but i have not idea where to start with performance parts. i am considering AFR 195cc heads and a decent comp hydraulic roller cam. any advice for the build is welcome but i am really wanting to keep stock like driveability. i know 300 rwhp should not be hard to make but i am fairly inexperienced with older SBC's. I have worked mostly on LS1,2, and 3's and the power gains are very easily achieved. my main concern with the TPI is tuning.what do i need for tuning the TPI? what are some weak components to consider? thanks in advance for any advice.

camaro1185

iTrader: (2)

Ive been around these TPI motors for a long time. If you want to up the horse power, very first thing should be the exhaust. These cars have very restrictive exhausts! Do hooker 2055s, high flow cat, and a catback. After that, the TPI's on these cars cant provide the motor enough air to make any decent HP, they are great for torque. Here you have 2 options. Grab a dremel and port the crap out of the plenum, get high flow runners, and port those, and get a high flow base and port that (or for less of a headache and cheaper option, just install a HSR). Couple the intake, exhaust with a good tune and your at about 240-250+ RWHP depending on your tune.

After that if you want even more, do a good set of heads/cam, tune it and you can be at mid/high 300's depending on your head/cam choice.

A proven heads/cam combo is the afr 195 heads and comp 268 cam. Thats good for 350-360hp. That will have good street manners and decent power!

1961ba427

iTrader: (26)

^ ^ Solid advice right there. ^ ^

On my old 89 Formula 350 I ran some cheap Summit / TrickFlow shorty headers and they are not nearly as nice as the hookers mentioned above or Heddman's similar design. The latter 2 brands will be easier to bolt in and the tubes are slightly larger. From there back, I had the exhaust shop build a custom Y-pipe using a Flowmaster 2.5" to 3" merge collector. It didn't have the ground clearance that the Hooker or Heddman Y pipe will have, but I believe it flowed a lot better. Magnaflow now make a great (and cheap) Y merge too. I ran this through a Hooker catback with no convertors.

It really woke my car up as well as giving me about 3 MPG's. I went from 23 to 26 mpg on the highway.

I also deleted the smog pump, the EVAP canister, added crank/alternator underdrive pulleys, and a TPIS airfoil.

With those changes alone, I ran consistent 8.80's in the 1/8th mile in Georgia summer heat. The transmission, convertor, rear gears, etc. were all still stock. I needed drag radials (still on stock 16x8 wheels all around) and a 3 ton floor jack in the trunk to hook up. MPH to weight calculations indicated it was at least 260 rwhp at this point.
I planned on my next round of upgrades being either SLP siamesed runners with ported base & plenum or a Holley Stealth Ram, adjustable fuel pressure regulator, mild ZZ4 camshaft (take-outs were going for $125 on Ebay back then) some good valvesprings, and 1.6:1 Comp magnum roller-tipped rockers. All of this would have been on a tight budget with the stealthram being the biggest $$ item.

Unfortunately a tornado chunked an oak limb about 6" in diameter through the windshield like a spear. It went through the dashpad, hit the console, and even badly dented the floorboard. I parked the car and started messing with LT1 stuff after that. I've still kept it and crank it every now and then....hoping to one day swap it into an older car. I'll always be impressed with how that TPI motor ran.

camaro1185

iTrader: (2)

Those calculators are way off. There is no way you made 260 with just a full exhaust. My car BONE stock put down 183hp, gaining 80 HP from headers is impossible on ls1's let alone a SBC.

1961ba427

iTrader: (26)

How much rwhp would you say it takes to move 3450# through the 1/8th mile @ 80 MPH? That weight is with driver and the car had zero suspension mods other than Lakewood LCA's and the Nitto Drag radials. When it was bone stock it ran 74-75 MPH at the same track.

Maybe mine made considerably more than 183 at the wheel when it was stock? What year was yours? Mine was a 1989. I know from others that the 88-89 L98's had a slightly better camshaft than the 90+ cars. I believe the MAF vs. Speed Density was good for some power too. When it was still bone stock that car would run dead even with the STOCK LT1 cars in my area and usually outran the ones with 2.73's. The only weight removal ever done was the spare, jack, and the emissions stuff I took off. I never had the valve covers, or any intake part off the car except the TB plate to install the airfoil. LOL My 89 Formula 350 with dual convertors & 3.27:1 gears was rated @ 235 HP stock. I believe it made close to that at the rear wheels stock. For what it's worth it ran the same thing with 142k miles on it as it did when it had 72k miles on it and still stock. That's when I started playing with it more. I have no reason to lie about what mods were done or what it ran. Why would I about a car that even though quick for what it was....is still slow?

Also....some cars are just better off the assembly line than others. A friend had an equally equipped 90 IrocZ (with 80k miles) that wouldn't consistently outrun another friend's '85 Iroc with a 305 TPI....both automatics...both stock. They were like tossing up a coin when they raced. Neither had traction issues and they were almost always dead even the whole run.

I did remember a couple more mods: I descreened the MAF sensor and I windowed the air filter housing and through in a stock replacement K&N filter.

rickybobbyss

tpi is a great motor and a lot of fun .I would not dump too much money into the tpi motor,you can put in a newer 5.3 or 6.0 and make crazy hp#s

CyberGrey Z28

iTrader: (4)

X2

But depends on your budget and goals. I wouldn't invest in a TPI for HP# alone unless you're nostalgic to the TPI.


300+rwhp is going to take after-maket heads, cam,intake set-up(stealth ram, mini-ram, first) plus tuning. That puts you in the hole $4-6k plus you have to find someone that will burn chips.

Or you can swap in a LS with bolt-ons and make similar power for about $3-6k w/room to grow(heads, cam in the future).

PS post some pics of that bad boy.

camaro1185

iTrader: (2)

Im not calling you a lair, and with nitto drag radials (that wasnt mentioned in your fist post) I dont doubt your track numbers at all. I was just simply stating those HP calculators are crap and the only way to see your real RWHP is a dyno. Also, to run those numbers at the track, with your weight, it doesnt need 260.

FWIW, I have used both the online calculators and one of those dyno apps on my phone and both told me I had 230-240's where as I said my car only made 183. That seems low for a l98 from what I have read about on TGO but than again most people have done at least a catback or headers when they post their dyno numbers. As I said, mine was bone stock, the way it left the showroom floor in 1988 with 78K miles on it (except the injectors). It now has a bit more mods but have no idea what it makes since I have not dynoed it yet.

mr.beachcomber

I'll admit that I like the TPI systems although the stock engines don't make much power on the top end. I agree that headers and exhaust should be your first modifications. I favor the smaller tube headers (1 5/8") for stock and mildly modified engines.

If you're looking for excellent torque on the street plus more muscle on the top end, I recommend the cast iron VORTEC heads with an aftermarket VORTEC TPI manifold. Should be less expensive that swapping over to AFR 195cc heads and upgrading the engine intake system.

As for cams, Comp Cams makes some mild cams for the computer-controlled TPI engines that will shift your power bank more towards the top end. Before you buy, talk with them about the specific mods you intend to make so they can help you choose the right cam for your application.

Hope this helps. Enjoy your TPI engine!

Paul Huryk

The real issue is the intake system - GM put that design on the motors to get max MPG through a super flat TQ curve down low. Unfortunately that design will max out power even in modified form at around 5000rpm (usually less). This is going to limit a 350 to around 300 to 325hp with that intake style.

But there were (and still are) some aftermarket replacements that eliminated the RPM and power bottleneck, most notably the TPIS miniram (which GM lifted the design for the LT1).

Yes there is power to be found in exhaust - headers and a properly sized cat back can add another 20 to 25hp, not counting friction reducing items like underdrive pulleys, also the intake tract can be upgraded for some easy HP.