I just picked up a 91Z coupe with 18K original miles. it is a 305 TPI. The car is 100% original, down to the speakers. I am looking to add a little more HP, if possible, while still keeping original components. I am looking for "bolt on" applications that could easily be removed if needed. Any suggestions?


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Full exhaust. In order to keep the original exhaust together you will need to drop the passenger side rear axle to pull the cat back, intermediate pipe, and muffler out in one piece. Stealth Ram intake is a bolt on, you'll be deleting the EGR valve but you can save it if you think you'll go back to TPI some time. You might be able to get a little bit out of a new chip burn with those mods and bump your timing up a hair. Can't really do the free mods as those mostly involve cutting stuff up.

 

Nitrous, heads and cam.

 

If he does heads a cam, he might as well just remove all limits on upgrades. He's trying to keep it relatively simple in the event he decides to swap back to stock components. +1 on nitrous though

 

I was thinking about exhaust and possibly an upgraded TPI unit from SLP. It wold keep the stock look and according to the specs, could add up to 20 HP


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bump for other suggestions


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Porting the stock intake, opening up your airboxes, and throwing 150 shot will give you much more power and keep it driving and sounding like stock!

 

Not trying to be a 'Purest' here but I have to ask the following:

1. Does it have the original tires?
2. Original battery?
3. Original windshield wipers?

If you answered No to any of the above it is NO longer 100% original so Mod away!

Seriously, hit with some NOS = Best 'Bang' for the buck and can be easily removed.

 

Personally, I'd put a new motor in and stuff the 305 into a corner somewhere so that you can sell it with the car if you ever decide to let the car go. Modding a 305 can certainly improve power, but a 305 with a few bolt-ons is going to provide a minor improvement at best, and in my opinion, isn't worth the cost of the parts. A nice stock looking 350 or 383 will provide a huge improvement in the "fun to drive" factor.

 

Gears, Full exhaust- Dyno dons, 3" catback, open up the intake, Check condition of injectors. If there original IMO there probably shot. Fresh injectors, plugs, wires, etc will make a huge difference in performance if the old ones are worn. Do all that stuff, focusing on worn parts first like injectors. And the car will feel great. And sound great with a good exhaust system. The gears will give you a nice kick too. All those things can also be added over to a larger engine if you wanted down the road. After the list above, focus on suspension. New shocks, struts and spings. Especially if you still have the old stock stuff will make you car handle like it should. Add subframe connectors to that, and youre Thirdgen will impress the hell outta ya.

 

As long as the 350 is 87+ and not a truck engine... sure. You know this, but I hate seeing people dropping their LB9's for smog era carb 350's and making 50 hp less.

 

Remember guys. The OP said he wants to keep the originality of the car. And with those miles, I dont blame him. Subtle, tasteful bolt on's would work best IMHO.

 

[quote=Stauf;5591007]I just picked up a 91Z coupe with 18K original miles. it is a 305 TPI. The car is 100% original, down to the speakers. I am looking to add a little more HP, if possible, while still keeping original components. I am looking for "bolt on" applications that could easily be removed if needed. Any suggestions?

I have been doing the same thing to my 1984 H.O. Z-28 (14,500 orig. miles). So far I have shaved off over a second off my Qt. mile time (13.72 @ 98. MPH) and gained 6 mph with bolt ons. I have replaced the complete exhaust with Dyno Don headers, test pipe, Hooker cat back, 4:27 gears, 2800 stall converter, under drive crank pulley and weld wheels with drag radials. I have saved every nut and bolt just in case I want to return it to factory original. The car drives great and I enjoy it much more with this set up. Engine is completely untouched and car still looks original with exception of wheels. Good luck and enjoy your car!!!

Frank

 

I am even more confused now. I see the NOS option as a possibility, as it can easily be removed. The exhaust, is a no brainer. Changing out the injectors, is a good idea. Do I keep the same lb injectors? or do I increase. I want to stay away from playing with the engine. That's what my 350 91 vert is for. Posted from Thirdgen.org App for Android

 

Playing with minor bolt ons will get you no noticeably power increase whatsoever. Just put an exhaust on it that you think sounds good and call it a day. If you want to mod it, mod it, if you want to keep it original, keep it original. These are diametrically opposed ideas.

 

I'll agree with this. If we were talking about an LS engine car that would be a different story, but making reasonable power out of a factory TPI car is not going to be possible without making big sacrifices to both drivability and originality.

 

I think he just wants some more power and some more go. He's not asking what heads to put on his new stroker motor. Bolt ons, gears and tuning. Will bring him to L98 territory.

 

This is perfect to see what common bolt ons equate to power wise.
https://www.thirdgen.org/forums/afte...s-any-one.html

 

I am probably the wrong person to ask, as I can't even bring myself to take the original exhaust off my IROC

With that said, an original 18,000 mile 22 year old car deserves to be left original. Don't mess with it. Guys are right...the few bolt-on type things you can do without wrecking the original flavor of the car will make a minimal change in performance.

Do an exhaust, some subframe connectors to keep the chassis tight, and detail it to a tee. Drive as needed

 

^ Def agree with that. Sometimes I wish I would have kept my (42K mile) car original. Got her with 7500 miles in 1996. O well, Gonna have to buy another one for that now

 

If you can find all the parts, do a complete SLP 50hp kit
(runners, headers (dyno Dons headers maybe), cat back),
K&N filters,
9" TQ converter, (rebuild trans if auto see http://www.700r4l60e.com/ )
port plenum
port SLP runners
port the base or aftermarket base ported
port the heads better valves and springs (or ported aluminum vette heads painted black)
bump compression
Cheater cam that sounds stock but better specs, roller rockers
Aluminum drive shaft
maybe a mid 3.00 rear gear.
Should be fairly easy to build 350hp.

 

^Great thread. I have decided to go with exhaust, high end plugs and wires, new injectors ( if needed ), full GM tuneup, and call it a day. As it was already said, this car deserves to stay original for now. I don't think anyone will crucify me for changing the exhaust and ignition. I already have plans to keep the orig exhaust in storage so it can be reinstalled at a later time.



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^ Excellent choice IMO! Gears will also make the car feel ALOT faster.
Full quality exhaust (Borla, Magnaflow, GMMG, etc..) gears, and an Ed Wright tune. Along with the tune parts that you mentioned like injectors. Youre car will run Great, and be a blast to drive on the street.

 

Do the gears, lol throw some 3.42s on it, and get an exhuast and you should be happy with your low mileage camaro. Or throw an ls1 in it and forget what the mileage says lol just kidding, but i would do it...

 

Wow you guys must have missed post #13. I myself back in the day did the same thing to my tpi car. Shaved over a sec in et and gained 6mph. You can still do plenty to a car and not hurt there value, save all the factory parts and you will be fine.
Really grinds my gears when people think you cant improve performance out of anything non ls series. Proper maintenance will shave time and make a car faster

 

I dont know why this reidiculous misconception is going around. Prior to 1997 cars were fast too lol. Just Ignorance I guess.

Anyways,, Back on topic. I think The OP's choice is great. I reccomend Dyno Don, or SLP headers to a 3" Borla cat back.

 

My car is 1 & 3...is that something "amazing"?

 

[quote=FJA1791;5592788] Umm i wouldnt consider that car origonal, nor unmolested now lol. Considering that they are all bolt ons ya you could go back to origonal but why buy a low mile car then upgrade it some, in my opinion you should have just bought any thir gen and upgraded it as rite now you have a low mileage car but it's better then stock like it is so why ever go back lol

 

I just wanted a low mileage 3rd gen so I could avoid any type of restoration. I didn't want to deal with old paint worn out interior or rust. I can easily perform any mechanical repairs and enjoy tinkering. I bought this car to enjoy it and that is exactly what I am doing.

 

Well low mielage doesnt mean it's in good shape lol. You can find a perfect third gen with 125k on the odometer and it look better then a 5k one, it's just about who owned the thing first and maintained it. But if you like it then i guess thats you opinion lol but i would have held out for one that someone wouldnt try selling for more because of the mileage which low mileage 90s and 80s cars shouldnt be worth much more lol.

 

^ Huh? Irrelevant.

 

Ya lol, i guess im way off topic i had to go back and read what we were talking about my bad, but ya i guess if it's stock I would add a better geared rear end like 3.08s or 3.42s or 3.73s if you like to be sideways while driving around town.
Also for an origonal low mileage car i wouldnt mess with it alot like nitrous, yes it will add a **** load of power to it but if it isnt set up rite then that low mileage motor may stay with those low miles forever if you know what i mean lol, throw a cam in it though

 

I tried rereading your post and make sense of it but I just can't... How many examples have you seen where 125k mile car is better then a 5k mile car. Being a 3rd gen of course. I know FJA1791 car. I've yet to see a 14k mi car, in that condition and for the price he got it. Win win across the board. Now I've seen plenty of 100k plus mile cars that you speak of in the 3-5k price range that are years away from that car. Restoration is not cheap. Going with low mi's and mint condition is a better starting point

 

.

 

The only way you can keep 100% originality while adding power is to trade that 305 TPI car for a stock 89-92 L98 TPI car.

Since you're set on changing it but concerned with originality, I'd pick one of these routes:

1. Period correct and reversible bolt-ons - Siamese the TPI, find some SLP parts or equivalents, look at some old Hot Rod magazines from the 80s/90s and see what bolt-on thirdgens were doing back then for basic power upgrades. Don't expect huge horsepower, but do expect to have fun and as long as they are bolt ons, you can reverse it all. Things like siamesed TPIs, headers, shifters, chips, air intakes, suspension components, etc., fall in this category.

2. Stealth mods - this is more internal, but not as reversible. Here, everything looks stock, but the inside is different. A mildly hotter aftermarket cam, port/polish the factory heads, TPI intake/plenum, manifolds, and TB. If you don't have to worry about emissions, get pass-through catalytic converters (ie - look like cats but inside is a straight through pipe), and get an aftermarket muffler that looks like stock with downturn pipes hidden up underneath. Chip, thermostat, upgraded brake lines/pads, shifter, suspension components are all things you can change and nobody would notice. Some of these changes aren't reversible, though.

3. If GM knew what it was doing - This is where you take all the good go-fast parts from your car's year and throw them together. Mate the L98 to a ZF 6-speed from the C4 Corvette. Add 1LE brakes and suspension components. Build a "factory stock" dream car from the 1991 GM parts bin with all the emissions gear, etc. It won't be original, but if you worked at GM and made the decisions, it would have been available...

 

#3 is basically what I did. I've owned my 305 RS for 8 years now, I bought it with 50,000 miles on it. The car is in great condition, and I love the factory look so my project is essentially "highest option" GM for the year. I made a B4C clone with 1LE brakes, so basically a 1991 1/2 B4C.

The motor is a fully built 355.




It looks stock to the untrained eye.

 

The one thing that everyone seemed to miss so far was sending the top end to extrude hone. It's expensive, but it'll get more flow out of the stock top end and nobody will ever know that you did it.