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Old 10-03-2013, 11:55 AM   #1
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Car: 1985 Pontiac Trans Am'
Engine: 305 LB9 V8
Transmission: 700R4
Axle/Gears: 3.23 9bolt BW

305 Rebuild/Build

Hey guys/gals,

I recently acquired a 1985 Trans Am, and it in in great condition compared to an 87 I had bought a couple years ago with fist sized holes in the floor . It has 92,000 original miles. Which yes, I know is still low.

It has the 305 TPI LB9 in it and I am looking to keep this car with its original engine, cause to me it is a great piece of American History and I want to keep it that way. I know everyone is going to tell me "Boat anchor the 305" or "Build a 350", but I'm not looking for a 400+HP engine.

I want to rebuild/build up the 305 a little for better street performance. My goal with this car is to have a good looking head turner with better performance than the stock 305 makes under the hood. But just enough to boost it to the 250-300hp range. I'm not planning on racing it on the drag strip much at all. I have never rebuilt an engine however but my dad who has before is helping me with this project. My hopes is to gain experience rebuilding this engine and throw some bolt ons to it, later on down the road to be able to build a 350 to throw in another high performance restoration

So my overall question to all you wise and knowledgeable Third Gen owners out there is;

What is a good build for the 305 to turn it into a decent performing V8?
Heads? Internals? Cam? Intake? I know the TPI is a restrictive engine. I just want a generally all around GOOD build.
I have been doing research and am just looking for options
I have a good amount of money to throw into the engine over the next couple years as it will be an ongoing build so.

So can you help me out guys?

Last edited by eaglesfan534; 10-03-2013 at 12:34 PM.
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Old 10-03-2013, 12:27 PM   #2
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Re: 305 Rebuild/Build

Just a FYI lb9 is tpi
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Old 10-03-2013, 12:35 PM   #3
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Car: 1985 Pontiac Trans Am'
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Re: 305 Rebuild/Build

Quote:
Originally Posted by Tuned Performance View Post
Just a FYI lb9 is tpi
I just changed it lol. I wasn't thinking right when I typed it up. The B slipped in there instead of the P
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Old 10-03-2013, 06:52 PM   #4
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Car: '91 Camaro RS
Engine: Carb'd 383
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Re: 305 Rebuild/Build

Start with headers and some differential gears. You'll see more gain per dollar than you will with engine building. If you're dead set on rebuilding the engine completely, then I would leave the rotating assembly alone, get a decent cam and lifters (this isn't a roller block, correct?) and there aren't too many choices for heads with a 305. I think edelbrock makes some, but again, its a lot of money with not a huge gain. Maybe get your heads ported and polished and get the valvetrain done. Then do some porting on your TPI parts and get a good tune to match. Either way, headers (shorties or longtube) and some differential work should be done first or at the same time.
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Old 10-03-2013, 07:36 PM   #5
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Car: 1985 Pontiac Trans Am'
Engine: 305 LB9 V8
Transmission: 700R4
Axle/Gears: 3.23 9bolt BW

Re: 305 Rebuild/Build

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Originally Posted by NagleMac View Post
Start with headers and some differential gears. You'll see more gain per dollar than you will with engine building. If you're dead set on rebuilding the engine completely, then I would leave the rotating assembly alone, get a decent cam and lifters (this isn't a roller block, correct?) and there aren't too many choices for heads with a 305. I think edelbrock makes some, but again, its a lot of money with not a huge gain. Maybe get your heads ported and polished and get the valvetrain done. Then do some porting on your TPI parts and get a good tune to match. Either way, headers (shorties or longtube) and some differential work should be done first or at the same time.
Well do you have any specific cams and lifters in mind? Like I am looking for specifics to piece together a build.
It is not a roller block, starts up and runs fine, but needs valve seals as most of them do around that age..

My friend is giving me a set of SLP 1 3/4' Stainless ceramic coated headers complete with y pipe. Also since I live in a non emissions state, I was going to get rid of all the EGR junk under the hood so I could use a Holly Stealth Ram intake. With those two things in mind, would my stock headers still be okay?

What kind of differential work should I be doing?
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Old 10-03-2013, 08:56 PM   #6
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Re: 305 Rebuild/Build

Cam is the last thing to choose, you'll need to know the rest of your setup first. DIfferential work depends on what you have already. A posi and 3.23 gears (at least, or 3.42 or 3.73) will make a huge difference. Whats the plan on heads and TPI? Porting the stock heads and changing springs to accept a larger cam (also changing valve seals, etc at the same time) will be a cheap way to get some more power. Then porting the stock TPI would be the next step. Get a set of roller rockers from one of Comp Cams "value" lines, some stock replacement pushrods (dont reuse old ones!), THEN choose a cam.

You can also just buy everything aftermarket, but you'll be $6k (at least) into it and you probably will be disappointed with the results for the money you spent. So your best bet is to get some work done to your major stock components, and things that can't really be made better (rockers, headers, pushrods, cam, things that cant be modified) are things you can go aftermarket with.

Also cam wise, I cant really give you a good recommendation, I have no idea how tuning and cams work together, I'm a carb guy.

Do you plan to start this anytime soon? I'd be interested to see the results. I almost did a build similar to what i suggested, but instead put out the money for my 383.
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Old 10-03-2013, 10:26 PM   #7
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Car: 85 T/A
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: 3.27

Re: 305 Rebuild/Build

I just rebuilt my 85 LB9 and this is what I did. First I had a spun bearing, so I had to tear it completely down. I took the block to my buddies shop ( the machine work cost me $0 because we did it after hours, so I have no idea what this part would actually cost) and we punched it .030 and balanced the rotating assembly with my new hyperutetic pistons. The pistons set .025 in the hole, so I ordered a .015 head gasket for a total of .040 quench. I then decided I wanted a roller cam and settled on a cheap used LT1 cam for $35. I then had to use a thrust button to hold it still since my block was NOT a roller block. Once the bottom end was assembled I went to searching around for a set of retrofit link bar roller lifters, I ended up getting a set on CL for $100. My factory heads were the 416's and while the block was apart I ported the heads and the whole TPI ( took me several months to port all that doing it a couple hours a couple of nights a week). I bought a cheap set of 1.6 rockers from summit for like $70. I had my valve guides replaced and I bought a spring kit from GM that makes them good to like .525 lift. Once I got all this together I put a set of shorty headers and Y on it with a 3" cat back. It performs really well now compared to before. I have a 165 ECM I'm going to swap in here in the not to distant future and then I'm gonna get into learning to data log and tune it. I believe there is a decent amount left to gain with a decent tune.
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Old 10-04-2013, 12:21 AM   #8
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Re: 305 Rebuild/Build

Yup, Chad's build is a perfect example. Reuse what you can, get some work done to the heads and tpi and you'll have great results for cheap. Dyno numbers Chad?
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Old 10-04-2013, 07:13 AM   #9
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Re: 305 Rebuild/Build

I don't have any dyno numbers. There is a guy about 2 1/2 hours away that has a dyno and when I get ready to start learning how to tune I was planning to give him a call and see if I can get what it is now and what it is after the tune.
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Old 10-04-2013, 08:08 AM   #10
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Re: 305 Rebuild/Build

My goal was to get my car back on the road as cheaply as possible and gain a bit of performance too. My long term goal is to learn to tune and do a larger cube stealth ram build. The OP could do pretty much the same thing I did except all the machine work on the block and crank. He would still have some work on the heads, but that shouldn't be all that bad. I didn't keep receipts, but I think I'm into it just under $1000 with the full exhaust.
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Old 10-04-2013, 11:21 AM   #11
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Car: 1988 Formula
Engine: 421 Little M block
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Axle/Gears: 9" 4.30s, Wilwood discs, 28X10.5-15


Re: 305 Rebuild/Build

Honestly: If you want to keep it stock and not plan to race it, just enjoy it for what it is and don't waste money on the engine.

Especially if the engine is mechanically sound.

The OEM TPI system was designed for the 305 which is why the power curve is almost on par with the 350 TPI.


I would leave the engine alone.


some other things to upgrade that WILL help and not break the piggy bank:

cat back exhaust system, and upgrade to OEM dual cats.

shorty headers: Edelbrock or SLP and still retain the use of AIR injection system.

rear gears especially if you have 2.73s in there.

Be warned an existing 2.73 gearset means you also have to replace the carrier to use 3 series gears & this gets expensive because you will also have to replace the axles. 3 series carriers will have more splines ( stronger)
so the stock axles will not work with them.

Hypertech Chip to replace the stock PROM in ECM: if you can still get them.

K & N air filter / modify a 4th gen whisper lid to for more cool air.


good luck and enjoy it
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Old 10-04-2013, 11:49 AM   #12
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Re: 305 Rebuild/Build

You can also add to your list:

Aluminum Driveshaft..(Island Empire) The stock steel driveshaft has terrible harmonics at high RPM.. (vibrates)

A new DS will solve that & free up some drivetrain weight.

if you have a 9 bolt rear , do you have rear disc brakes?

you could simply take your stock 85 TPI and make it a 1LE car. sans manual transmission. but a T56 conversion is pretty straight forward.

better front brakes.. better exhaust.. AC delete if you want. the parts are out there.

but that's my opinion.

Last edited by FRMULA88; 10-04-2013 at 11:52 AM.
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Old 10-05-2013, 12:32 AM   #13
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Transmission: T56 6-speed
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Re: 305 Rebuild/Build

AT A MINIMUM I would put a new timing gear set on your list !! The thing is coated in Nylon and apparently real prone to failure.

The stock timing gear in your car will probably be this one:



With any luck it doesn't look like this:




The 85 TPI engine is one of the strongest 305 TPI's I ever owned. (Never owned a Speed Density 305 TPI ) I am in the middle of a completely different 85 TPI rebuild right now (bolted rebuilt heads on yesterday) and I decided to leave the original cam installed. I'll be spending the $$ "saved" on Steel 1.6 full roller rockers instead.

As others have pointed out, there are a LOT of things that will enhance what you have already. Headers and good exhaust are very significant upgrade. So is ANY type of increased air flow before the Plenum (CIA or K&N, Air Foil) Losing some weight is also cheap and easy,.... AC delete, Cruise delete & smog delete (if possible) are common then there's other stuff like an Aluminum driveshaft, or an Aluminum Water pump or fiberglass hood to lighten the load a bit more. A stong Distributor module, Coil, and quality Plugs/Wires also make a differance.

I would even leave the rear end for now...... your ride should have 3.23 POSI and probably rear disk brakes. A rear end gear change is THE biggest "bang-for your $" upgrade for many people, but a 3.23 gear is where you want to be right now.

Sorry bought the hijack; but I've got a question !

Chad85T/A - Since you swapped to a roller cam; Did you also have to change your Distributor gear and retain the coil in cap distributor ?


Back to eaglesfan534 : That 85 Trans Am should have a very limited production suspension under it. Check the Sway bars,.... 25mm Rear and solid 34 in front.




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Old 10-05-2013, 10:45 AM   #14
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Car: 85 T/A
Engine: 305 TPI
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Re: 305 Rebuild/Build

Quote:
Originally Posted by John in RI View Post



Chad85T/A - Since you swapped to a roller cam; Did you also have to change your Distributor gear and retain the coil in cap


yes I did. I believe it was a lunati everwear. I ordered it when I ordered my head gaskets, timing set for the roller cam, and the rocker arms from summit.
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Old 10-06-2013, 03:57 PM   #15
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Car: 1985 Pontiac Trans Am'
Engine: 305 LB9 V8
Transmission: 700R4
Axle/Gears: 3.23 9bolt BW

Re: 305 Rebuild/Build

Thanks guys for all the tips thus far. Yeah it has rear disc brakes, it has the 9 bolt rear end, I'm guessing is the 3.23? I like Formula88 and John in RI's simple ideas to boost it a bit. Keep the ideas coming though I am planning on pulling the engine by November after I strip the rest of the car down. I am going to build it during the winter
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Old 10-06-2013, 11:00 PM   #16
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Re: 305 Rebuild/Build

The rear can't be a 3.23; not if the rear is a 9-bolt.

Not much is documented on the early 9-bolts in the TA cars - not as much as later years anyway. If you still have the RPO sheet ( with all the codes on it ) then check to see what your "Gxx" code is. 'G' will be the first character & the 'xx' will be your second and third 3rd characters in the code.

For example; "GW6" is a 3.27, or "GM3" = 3.45

If you don't have the RPO sticker anymore get the car on the hgihway and leave the 700R4 in 3rd gear till you hit 70MPH and make a note of the tach reading. Your RPM reading @70 in 3rd will tell you the rear gear ratio..... 3270RPM @70MPH in third = 3.27 gears. ( an accurate tach is important ! )

Other ways to find the rear end ratio are to count the driveshaft revolutions per wheel rotation or removing the diff cover and reading the gear count shown on the ring gear.


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Old 10-07-2013, 11:03 AM   #17
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Re: 305 Rebuild/Build

My TA has the GW6 and also has a tag on the rearend housing that is held on by one of the pan bolts that's stamped 3.27.
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Old 10-07-2013, 11:12 AM   #18
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Re: 305 Rebuild/Build

Quote:
Originally Posted by Chad85T/A View Post
My TA has the GW6 and also has a tag on the rearend housing that is held on by one of the pan bolts that's stamped 3.27.
That's great, means the carrier should stay the same.

I think you can get 3.73 gears for the 9 bolts now.

back in the day that was not possible.
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Old 02-17-2017, 09:45 AM   #19
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Join Date: Nov 2012
Location: Brewer, Maine
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Car: 1985 Pontiac Trans Am'
Engine: 305 LB9 V8
Transmission: 700R4
Axle/Gears: 3.23 9bolt BW

Re: 305 Rebuild/Build

Quote:
Originally Posted by John in RI View Post
AT A MINIMUM I would put a new timing gear set on your list !! The thing is coated in Nylon and apparently real prone to failure.

The stock timing gear in your car will probably be this one:



With any luck it doesn't look like this:




The 85 TPI engine is one of the strongest 305 TPI's I ever owned. (Never owned a Speed Density 305 TPI ) I am in the middle of a completely different 85 TPI rebuild right now (bolted rebuilt heads on yesterday) and I decided to leave the original cam installed. I'll be spending the $$ "saved" on Steel 1.6 full roller rockers instead.

As others have pointed out, there are a LOT of things that will enhance what you have already. Headers and good exhaust are very significant upgrade. So is ANY type of increased air flow before the Plenum (CIA or K&N, Air Foil) Losing some weight is also cheap and easy,.... AC delete, Cruise delete & smog delete (if possible) are common then there's other stuff like an Aluminum driveshaft, or an Aluminum Water pump or fiberglass hood to lighten the load a bit more. A stong Distributor module, Coil, and quality Plugs/Wires also make a differance.

I would even leave the rear end for now...... your ride should have 3.23 POSI and probably rear disk brakes. A rear end gear change is THE biggest "bang-for your $" upgrade for many people, but a 3.23 gear is where you want to be right now.

Sorry bought the hijack; but I've got a question !

Chad85T/A - Since you swapped to a roller cam; Did you also have to change your Distributor gear and retain the coil in cap distributor ?


Back to eaglesfan534 : That 85 Trans Am should have a very limited production suspension under it. Check the Sway bars,.... 25mm Rear and solid 34 in front.




Hey Guys, thanks for all the help back a few years ago. It ended up that my 305 was trashed. The guy who I bought it from ran it without an Air Filter, and bad valve seals for over a year, and the inside was TRASHED.

So a buddy sold me a 350 that was fully machined, with a crank and pistons with it for $500 and I went from there!
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