mr.amazing999

i am in iraq right now and i want to get my build all set to go when i get home next month... i have a a 92 firebird with a 305 auto ... i want to rebuild the top end and my end goal is atleast 250hp i have been think about going boring it 30 over and it seems geting my old heads machined instead of buying new ones is the way im going to go with them but is it worth spending the 900 pluss on new heads? any idea or prior build infor would help alot i realy just dont know where to start

RED86Z28

Are you TBI or TPI?
I would go for aftermarket heads. Your goal of 250 hp is kinda low. You should shoot for atleast 300.

Atilla the Fun

Vortec heads should get you 350 horses, while 081s should get you 300.

Doom86

First thing you need to do is replace the exhaust from the heads to the tailpipe with parts for a 350TPI.

The best bang for the buck right now AFAIK is hooker 2055 headers, matching Y-pipe and 3" magnaflow stainless exhaust. I got my magnaflow and cat from Bandit exhaust for less then the exhaust alone from Jeg's. Go to the website and make them a offer, low ball them badly, it works.

250hp is easy. You could just have bigger budget performance valves installed in the heads and they would build that power (if it's TPI, if it's TBI I don't know) with the right cam. The heads could do it in stock trim with the right supporting mods, the bigger valves will make it easier though.

Regardless of what 305 you have it's going to need a good tune to run right so keep that in mind.

mr.amazing999

the 250 hp was a typo im shooting for 350 and its a tbi i have a 80's series flowmaster muffler with 2.5 piping from the prior owner... i have around 3000 for the build im also looking into geting some 26lb fuel injectors and a new 58mm throtle body max hp is not my main goal i want a solid stout engine that will last

five7kid

iTrader: (14)

Hmmm, 305 & TBI.

Step #1 - Heads. Very good heads. Don't skimp on heads.

Step #1 - Exhaust. You'll need to replace all of it.

Then, larger TB/injectors/fuel pump, cam, tuning. Additional tuning. Then some more tuning.

Finally, prepare yourself for not achieving your 350 HP goal. Might get it if you calculate gross flywheel HP. But, not very likely at all using any other measure.

Boring the cylinders should only be done if there is excessive wear. Most likely there is not.

You can use your stock heads to hold the garage walk-through door open while you're working on the car.

Doom86

This build is all about the heads then if you want that power. You start with good heads then build everything else to support them.

What heads you want depends on what you want to do with them. If you want to spend hours porting them there's more options then if you just want to get a pair and bolt them down.

If you are serious and want to do it right and don't want to spend hours porting get good aftermarket heads, the market is not really there for 305's so go with; http://www.summitracing.com/parts/TFS-30300003/

Those heads are machined for larger spring and support .600 lift. Which you will be needing to meet your goals, and for the cam I'm suggesting.

For a cam use; http://www.summitracing.com/parts/CCA-08-466-8/

That is the comp cams XFI268.

Being a theory guy I worked this up on DD2k for you. You'll be needing a good dual plane intake, Performer RPM or equivalent. You will need the exhaust I previously suggested at least. Also the fueling system will need upgraded, bigger TB, injectors, fuel pump, regulator, and TB adapter to whatever intake you pick.

Then once you've done all that you need to tune, tune, tune. I've never tuned a TBI my self but from what I read RBobs EBL is the way to go; there is several reasons to go this way and its not just ease of use.

It's not going to be dead accurate but attached is what the motor simulator comes up with.