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Building a better than stock 305

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Old 02-18-2014, 02:25 PM   #1
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Car: 1985 Pontiac Trans Am'
Engine: 305 LB9 V8
Transmission: 700R4
Axle/Gears: 3.23 9bolt BW

Building a better than stock 305

Hey everyone!

Its that time in my project where I am going to do the engine.
I have a 1985 Trans Am with the 305 TPI LB9, it has around 90,000 miles and burns a bit of oil. Probably needs to be re-ringed...
I am going to keep the 305 as I am not looking for a drag strip car or a racecar. I just want to drive this around town during the summer here and there.
Basically, I am looking to just rebuild the engine to make it "newer". I want to do a rebuild that is better than stock however. I know I might need to get it machined a bit.

So what are your thoughts on how to accomplish this? I have been told by some people that to squeeze a bit more performance out of the 305, i should buy new heads, a slightly more aggressive cam, exhaust and maybe some underdrive pulleys. I already have bought a magnaflow catback exhaust and some SLP ceramic coated 3" headers (Bought used from my friend for a great price).

So what should I buy to do this? Master rebuild kit? Whats a better cam to pop in there? Heads? Should I touch my low end at all? I need help!!
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Old 02-18-2014, 02:37 PM   #2
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Re: Building a better than stock 305

I'd strip it down and have rotating assembly checked out. Block probably needs an overbore so need budget replacement pistons. Hopefully you can reuse rods and crank.

Have shop check dimensions on block, resurface deck, and just get the right replacement bearings which give proper clearances.
Have heads cleaned, resurfaced and valvejobbed. Or find set of L30-L31 vortecs and do same thing to them. Add screw in studs, seals and fresh springs. Convert to retrofit hyd roller, something like a 212/218 or 218/224 cam on a 110-112 lsa.
Gotta upgrade runners to the tpi with some big tubes, maybe port base alittle.

Should add 30-40 hp easily and really drive well. Probably have a peanut cam in it as it is. Proper valvejob intake work and cam plus tune will wake it up alot

Regarding tune change over to 86-89 maf and 165 ecm. Or 730 speed density. Learn to burn chips. Has to be done with cam work
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Old 02-19-2014, 06:08 AM   #3
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Re: Building a better than stock 305

I noticed you mentioned underdrive pulley..... IMO a waste of money. You can do a search on the debate about those things, but generally speaking, they're not worth it. I know, i wasted the money on one lol.
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Old 02-19-2014, 07:27 AM   #4
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Re: Building a better than stock 305

Best money you can possibly spend on a 305, is a 4" bore block for it. If you are doing ANYTHING that involves touching the short block, touch some other short block instead; exact same $$$, FAR more results.

Spend the same, get more. What's not to like?

Spend the same, get less. Surely you're not some kind of "alternate winner" or something?

If you're NOT touching the short block, then everything else like heads and cam and exhaust is fair game; just, do it carefully so that when you DO have to touch the short block, you can transfer it over to your new one. I.e. no 305-specific heads and such as that.
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Old 02-19-2014, 08:36 AM   #5
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Engine: 421 Little M block
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Axle/Gears: 9" 4.30s, Wilwood discs, 28X10.5-15


Re: Building a better than stock 305

IF the stock 305 engine is tired and you want a "fresh one" a 350 will cost the same (possibly less) AND give better results.

Sell the 305 for scrap but keep the TPI system, distributor, pulley brackets, accessories, etc.

Buy a GM crate motor 350, bolt on the TPI system, pulley brackets, accessories etc. (re-use all the parts that bolted on to the 305)

re-flash the PROM for the 350

done.

Don't waste time / money with under-drive pulleys.

there is nothing special about the smog era 305. get over the sentimental attachment and illusion that you have the motor so it's "free" and will cost less to rebuild this is flat out BS. By the time you pay for all the machine work to make a 90,000 mile block, rotating assembly, and heads "new" you can just buy all new parts that will perform better?
besides you will have install all new bearing, seals, gaskets, also.

A new crate engine will have all this done already and satisfy your intended use. If you wanted to race I would have the engine "hand made" by a builder for the purpose.

Last edited by FRMULA88; 02-19-2014 at 08:43 AM.
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Old 02-19-2014, 09:03 AM   #6
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Re: Building a better than stock 305

If the 305 just needs bearings hone and rering its gonna be cheaper. Time you find a 350 block and have it checked and machined you are in several hundred bucks and you now need new pistons for 4" bore plus new heads, as its a waste to run 305 heads.

Find out the bore condition on the 305 before doing anything. If it needs bored out and budget pistons it may make sense to spend more on a 350 block. All depends on what you find and how much money you have. Theres a big difference in power and torque between the L98 and Lb9's as seen in countless 1/4 mile results and they both used same cam at times. Cubes and big bore help
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Old 02-19-2014, 12:28 PM   #7
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Re: Building a better than stock 305

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Old 02-19-2014, 11:32 PM   #8
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Join Date: Nov 2012
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Car: 1985 Pontiac Trans Am'
Engine: 305 LB9 V8
Transmission: 700R4
Axle/Gears: 3.23 9bolt BW

Re: Building a better than stock 305

Quote:
Originally Posted by FRMULA88 View Post
IF the stock 305 engine is tired and you want a "fresh one" a 350 will cost the same (possibly less) AND give better results.

Sell the 305 for scrap but keep the TPI system, distributor, pulley brackets, accessories, etc.

Buy a GM crate motor 350, bolt on the TPI system, pulley brackets, accessories etc. (re-use all the parts that bolted on to the 305)

re-flash the PROM for the 350

done.

Don't waste time / money with under-drive pulleys.

there is nothing special about the smog era 305. get over the sentimental attachment and illusion that you have the motor so it's "free" and will cost less to rebuild this is flat out BS. By the time you pay for all the machine work to make a 90,000 mile block, rotating assembly, and heads "new" you can just buy all new parts that will perform better?
besides you will have install all new bearing, seals, gaskets, also.

A new crate engine will have all this done already and satisfy your intended use. If you wanted to race I would have the engine "hand made" by a builder for the purpose.
So it just so happens a friend of mine just got a 350 machined and ready to go....has everything to go with it. Wants a cheaper price than a new crate....guess I may do that
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Old 02-20-2014, 08:46 AM   #9
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Axle/Gears: 9" 4.30s, Wilwood discs, 28X10.5-15


Re: Building a better than stock 305

well there you go... just make sure all the parts are there.. and within "specs" you don't want any surprises..

IF you guys value the friendship they he won't be offended if you want to have the block etc. inspected before you commit.

Nothing ruins a friendship faster than a "bad deal" on a car or other expensive parts..
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Old 02-17-2017, 10:46 AM   #10
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Join Date: Nov 2012
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Car: 1985 Pontiac Trans Am'
Engine: 305 LB9 V8
Transmission: 700R4
Axle/Gears: 3.23 9bolt BW

Re: Building a better than stock 305

Quote:
Originally Posted by FRMULA88 View Post
well there you go... just make sure all the parts are there.. and within "specs" you don't want any surprises..

IF you guys value the friendship they he won't be offended if you want to have the block etc. inspected before you commit.

Nothing ruins a friendship faster than a "bad deal" on a car or other expensive parts..
All it ended up needing was two cylinders re-bored because they were "slightly" off. Bought it and built it!
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