I have a 89 TA with a 305 TBI. It only has 85K miles on it. It is all original and never been altered even right down to the stock exhaust! I bought this car because of the amazing condition and the fact that it is bone stock and the 60 year old woman that owned it for the last 20 years never beat on it. I really like the fact that its original and want to keep (at least) the look of it being original. Id like a bit more power so I was thinking of putting a stock 350 TBI in it out of a truck. I happened to find an 89 truck with the same mileage (85K) and thought it would be pretty cool to have the same year and mileage donor engine as the car its going in. From what info I've found I can get a 50HP gain keeping the replacement engine stock. I want to keep this low budget and these donor engines are pretty cheap. Thoughts?

 

You will gain very little HP keeping the engine stock with factory exhaust. The civilian caprice 350 was only 180 hp when choked with the same manifolds and similar exhaust. Truck L05s came in two flavors, 8.75:1 and 190 hp and 9.3:1 making 200-210. Trucks had a much less restrictive exhaust with better flowing manifolds and a 3" Y-pipes. The air intake system was also much less restrictive, with larger ducting and a taller filter. That being said a L05 350 makes about 40-50 ft/lbs more torque than the L03 does.

 

I did not know that. I guess I was always looking at G-van figures, and thought they were all 210 horse.

 

The 8-lug G-vans had the same 190 hp 8.75:1 350 in them too. GM built a HD 4.3 TBI as well and slapped a turbo on them in the Typhoon/Syclone.

 

My car was much like yours when I bought it ... right down to the 89,000 miles.

Here are a few pieces of advice based on my experiences.

1. Don't swap out the 305 until you have to. It's running fine, go ahead and get your use out of it. While you do, you can work on #2.

2. Before you make any engine mods, learn how to tune it. If you're going to keep the TBI (which I recommend), you are going to have to learn how to work with the ECM. Even if you take my advice, and keep the 305 for now, you will not see the full benefit of doing headers, exhaust, ignition, intake, etc unless you are able to optomize the tune for those changes. It seems daunting at first, but there are plenty of real smart people on here who will help you. You will be surprised to learn that you can get quite a bit more out of the stock configuration simply through tuning. Spend some time with the stickies up top.

My recommendation would be to get Embedded Lockers and start learning how to tune.

3. Make no internal mods to the 305. While I think you should definitely go along with the 305 until it's worn out, I don't believe it makes any sense to do cam and head swaps to one; certainly not pistons, stroking, etc. The 305's small bore means there's only so much you can get out of it. Meanwhile, you can get a brand new GM L31 350 long block, with Vortec heads for under 2 grand. When you're ready, get one, pull the heads and spend 200 bucks at a machine shop having the heads upgraded for cams of over .480 lift, slide in a nice cam, and you're ready to go.

Others will probably disagree with me, but I think money put into an L03 shortblock is wasted. Instead, use the L03 as a solid, dependable mule while you learn about your car.

Good luck!

 

 

#4 Go to a 3.42 posi as your first mod. Best bang for the buck you can do. It will feel like a completely different car, and it was worth a full second in the 1/4 mile on mine.

 

Thanks everyone for taking the time to post. I appreciate all the info!

 

Personally I would look for a 3.27 or 3.45 geared 9-bolt rear. Stronger than the 7.5" and likely has a factory limited slip.

 

The problem with the 9 bolt is availability of parts. I had one I was going to put in my car. We tore it down, the cones were marginal, and I went looking for new ones.

I don't remember how much they were, but it was HIGH. Every part I looked for was expensive as hell, and most had to be shipped from Australia, so the shipping made them even more expensive. I sold the rearend after talking to a local guy who does nothing but differentials who said if my 10 bolt ever broke, he could blueprint me one for a fraction of the cost of building a 9 bolt.

According to him, 90% of the cure is a good differential cover with stabilizer bolts.

http://www.jegs.com/i/Proform/778/66667/10002/-1

Ideally, I'd like a 9" with 355 gears, but as long as my 10 bolt keeps working as well as it has for the past 10 years, I'll stick with it.

EDIT: I see http://www.9bolt.com is up and running again, so maybe that changes things a bit. When I had my 9 bolt, they were out of business.

 

theres a lot of cons to the 305tbi. biggest con is they DON'T breathe. intake, heads, tiny cam, and exhaust all are restrictive. But the Bore and stroke really aren't that bad. Example-
305 3.736 bore x 3.48 stroke
4.8LS 3.78 bore x 3.27stroke
5.3LS 3.78 bore x 3.622 stroke
Ford 4.6 mod motor 3.5 x 3.5
Yes, i know a 305 won't run like an LS, I was just using this as an example.

It really depends how much power your looking for.

You got to make the 305 breathe! Heads, cam, and exhaust will go a long way. Nobody will shoot you for putting some headers on it. The stock intake and tbi will be restrictive. you can upgrade but it won't be stock. You'll want to upgrade the fuel pump and probably get an adjustable fuel pressure regulator. And like the others said, you'll have to learn to tune it all. When i was researching modding my LO3, i was interested in an EBL for tuning. With all that being said, you'd be further ahead doing all that to a 350 and nobody would ever know the difference unless they looked up the block casting #. Theres lots of info on modding the LO3. FYI, I decided to go LS. I couldn't justify the cost of modding the 305, the cost of building a 350 put me in crate motor price range (those come with a warranty, no brainer) and for that price i could go LS.

For gears, I'd go with 3.42. 3.73 would be more aggressive but less fuel friendly. Difference is only about 275rpm at 60mph in OD. Yes the 10 bolt is weak, but you got a ways to go on power before you need to worry about that.

 

I like the stock looking thirdgens with more power under the hood.

As already pointed out the stock LO5 out of a truck will most certainly leave you disappointed, it would better to look in to a 350ci that has at least a roller cam.

 

most of the v6 cars are 3.42 geared.i just swapped one of those in.100 dollar mod.or if you want to use forth gen or corvette wheels get a rear from a 1998-2002 and gain rear discs.

 

Isn't that a open rear end? aka one wheel peel?

 

yes but most camaros aren't posi.i added the posi to it.

 

The Vortec 350 with a LT1 cam has alot of power.

Uphill on ramp in the 1999 C1500 Suburban.

 

5.7L Vortec with LT1 cam.

Probably a nonsensical question, as there are so many variables to making horsepower, but assuming all else is the same (headers, induction, c/r, etc.)...with the L31 at 255HP, and the LT1 introduced at 275HP (IIRC)....where do we think the L31 with LT1 cam hybrid lands HP-wise? If it's in the middle, is it worth the money for 10 horsepower?

I have a friend who had a GMT400 Suburban with L31 and LT1 cam, and he said it made a nice difference. So it's not that I am not a believer in the combo...I'm just not sure where the power boost comes from, so to speak.

 

The LT1 makes more like 300 HP stock its under-rated a good bit in the F-cars. In a Vette it is rated 300 HP. I have seen them make 250-260 RWHP in a STOCK F-car and about the same in a Vette. The Vortec truck engine makes about 190-210 RWHP stock.

Vortec to LT1 cam swap is 30-40 HP above peak, near redline. Probably about 20 HP peak to peak, but raises the peak 4-500 rpm. So power moves from 4,600 to 5,100 and gains about 20 peak to peak. Near the redline at 5,600 its up about 30-40 hp. A stock cam LT1 can make 340-350 HP at the crank.

I had an LT4 cam in my Express and now this GMT400 suburban with the LT1 cam. Both cams make a very nice difference in a stock longblock L31. With headers, exhaust, CAI, oversize throttle body, and tuning they both kicked out some nice power. I pulled a RCSB V8 GMT400 truck on a tandem axle trailer (~6,500 lbs) for 300 miles behind the suburban a few weeks ago. Dropped the shifter into 3rd and stepped on the gas. I found myself running 80 mph with traffic a few times and backed down to 65 and set the cruise. I hit some good long hills and it never even unlocked the torque converter, much less downshifted.

The power boost comes from the fact it has 10* more duration seat to seat and .050", ~.050" more lift, and wider LSA to flatten the curve.

OBDII F/Y-Car LT1

270/276 @ .006, 201/208 @ .050, .446/.459" lift, 117° LSA, 117° ICL

The factory L31 cam (also used in the B-car LT1 and L99)

259/263 @ .006, 191/196 @ .050, .414/.428" lift, 111° LSA, 106° ICL

 

I used the stock vortec heads, hypereutectic pistons,summit flat tappet cam around 218/218 @ 465 lift and it was a screamer. It ran in the 13.7 easy in a GTA I had and I was losing time as much as half a second shearing my street tires with stock gears also. I bet with better springs and the Lt4 cam it would have been a beast. The stock LO5 wouldn't be a big improvement over the LO3 I imagine it would maybe run as good as a stock LB9 if it was tuned right.

 

As good as Vortec heads are, they don't flow as well as the LT1 heads, so you wouldn't make the same power.

I also think the LT1 and the LT4 cams are pretty mild for the flow capabilities of even Stock Vortec heads.

Remember Danger Mouse ..... 440 HP on unported Vortecs.

http://www.superchevy.com/how-to/eng...s/viewall.html

 

You got it backwards boss, the Aluminum LT1 heads do not flow as well as Vortecs. Iron LT1s and Vortecs have the same ports and same flow #s. A stock vortec intake does not flow as well, but they work quite well under 5,500 rpm and under 360 HP. They can also outflow the heads with some quality time with rotary tool, carbide, and sanding rolls.

You actually give up a little dynamic compression ratio with the LT1 and LT4 cam in a vortec engine, but what you sacrifice gives you the ability to run a more agressive timing map. Where a stock vortec tolerates 24-28* on premium fuel, a modified engine can run 30-34* and it can come in much more quickly, even on 87 octane. Case in point the Suburban runs 26* @2,600 rpm, 30* @ 3,600, 32* @ 4,800+ on 87 octane and rarely even tickles to knock sensor on 87.

 

I think the 350 swap is worth it, mine was 9.3:1 (claimed) and had a mild towing cam. I don't think I'm making more than 220-230 HP, but its really really nice. Better mpg, effortless burnouts, and u can still tell ppl its a 305. Hills on the highway are literally unnoticeable.