According to the Wikipedia the most HP any factory 305 made was 250hp.  The only factory Chevy V-8's that made less are: 262ci(110Hp), 307ci(200Hp), 265ci(240Hp).  Of all the Chevy V-8's only the 262ci had a smaller bore, ALL others had larger bores, which is important to note because of valve shrouding in air flow with bigger valved heads.

The next closest in Displacement except the 307 is the 302ci and 327ci which made 290Hp and 375Hp respectively in top form. I guess it's worth noting both are 4" bores.  Heck, the lowest Hp a 327 made was 250Hp.  

I think later 305's (90-92) with the TPI and dual cat setup got up to 220-230 HP range.

While at one time I was of the mentality that I'd show everyone that 305's weren't worthless...it turns out everyone is right.  If you look at that build I posted...that was pretty well maxed out.  You cannot increase valve sizes, so cylinder heads WILL limit the power of a 305.  Lack of piston choices limits possibilities of using power adders like turbo's, nitrous, or superchargers.  Or even just high NA power.

And all that work for something that is externally indistinguishable from any other SBC.  Why not just build a 427 or 454 stroker?  It'll look exactly the same to the untrained eye (ie anyone not looking at casting numbers or brand names).  

I also am faced with your dilema,an 84 trans am with 305 power.The only solution that seems fit is a 400 or 455 pontiac-make a real TA out of it  

swinger72:
I also am faced with your dilema,an 84 trans am with 305 power.The only solution that seems fit is a 400 or 455 pontiac-make a real TA out of it

THAT would be cool!  

Hunter T, I understand that you want to keep your car numbers matching but if you want to make power, the 305 is not the way to go.  Pull the motor, put it on an engine stand, and stick it in the corner of your garage.  That way if you decide to return the car to numbers matching, the engine is ready when you are. You say your goal is 300 HP.  That's not hard with a 350. Below as an article from this very website showing you how to rebuild a 350, what to look for when picking one, how to pick a machine shop, what parts to use, and the dyno numbers at the end...

http://www.carcraft.com/howto/116_0301_budget_engine_build/index.html

This is just one example of what you can find when you look.  These guys at Car Craft have done alot of the slog work for us.  It's a good idea to take advantage of their expertise.  I'm not saying that any of these guys don't know what they're talking about, hell I've learned alot about heads, valves, and such just from reading this thread.  It just sounds like you're looking for a simpler solution and the above link has it.  Hope this helps!  

All this debating is fine,however, the qestion remains of whether or not we can coax 300hp out of a 305?...........I believe its possible.Firstly the restrictive ports ,will have a high velocity strong vacuum signal given the displacement.This means that they will respond well to porting,even a home port job although I highly recommend getting it professionally done.Machine shops that use cnc porting are the least expensive............A valve combo of 1.88/1.60 this is ideal for a 305 bore vs stroke combination on a STREET level.........Next compression, HAS TO BE AT LEAST 9.5:1. Either buy the pistons or machine the head/block decks to achieve this..............the cam between 220 to 224deg @.050 with a valve lift around .460" a lobe seperation angle of between 110 to 112deg. ................a 600cfm carbie(prefferably a double pumper) a good dual plane alluminium intake manifold. Like a edelbrock performer rpm or a weiand stealth. a good electronic or dual piont ignition .the biggest bolt on headers(primary pipes)that you can buy off shelf.Either a twin 2" or single 3" freeflow muffler exhaust system. The carb can be as low as 500cfm for better fuel atomisation and throttle response...............yOU MAY also want to simply bolt on larger family heads and use machining to get compression up.........................Pistons I'd go for hypereutectics as they have a tighter piston to bore clearance than forged. However ,regarding pistons there are several manufacturers that can make any spec piston you want,although this is more expensive.....................Blowers/turbo They would definitely make alot more power on a 305! I dont care what the port size! Primarily because ,its FORCED IN AIR AND FUEL.Conventional flow numbers become virtually meaningless when the pressure is above atmosphere. Yes I would Max out the exhaust port and valve for a FORCE FED 305ci, but I'd leave the intake alone on a turbo application, with porting it mildly for a blown application...................Bottom line you could make 300hp with mostly second hand parts and some new ones. Heads,headers,intake manifold,carb and ignition can all be good condition seconds.Given the abundance of faith lacking 305 failures theres probably alot of performance goodies out there in the second hand markets and swap meets. A true car crafter would build the 305.  

TheSilverBuick:
According to the Wikipedia the most HP any factory 305 made was 250hp.  The only factory Chevy V-8's that made less are: 262ci(110Hp), 307ci(200Hp), 265ci(240Hp).  Of all the Chevy V-8's only the 262ci had a smaller bore, ALL others had larger bores, which is important to note because of valve shrouding in air flow with bigger valved heads.

The next closest in Displacement except the 307 is the 302ci and 327ci which made 290Hp and 375Hp respectively in top form. I guess it's worth noting both are 4" bores.  Heck, the lowest Hp a 327 made was 250Hp.

Hey Buick, sorry to hear that you blew a head gasket, that really sucks. I hope you get it running again. Now back to topic, you forgot the 267 V-8. It has 125 HP @ 3800 RPM, and it is only a 3.5" bore diameter. Also I think the 283's were under 250 HP net with accsessories attached. Also the 302 was actually closer to 360 HP, GM had underrated them when they did the specs.  

Thanks, I had it running three days later because I needed to drive the car the 500 miles back home

I'm no Chevy expert by any means, everything I put was from the Wikipedia, and I don't doubt for a second GM underrated their stronger engines and overrated their weaker ones.

On topic, if you go forced induction you definately don't want hypertenic(sp?) pistons because they tend to break with detonation that can easily occur with force induction and/or high compression.  

powerdreams:
All this debating is fine,however, the qestion remains of whether or not we can coax 300hp out of a 305?...........I believe its possible.Firstly the restrictive ports ,will have a high velocity strong vacuum signal given the displacement.This means that they will respond well to porting,even a home port job although I highly recommend getting it professionally done.Machine shops that use cnc porting are the least expensive............A valve combo of 1.88/1.60 this is ideal for a 305 bore vs stroke combination on a STREET level.........Next compression, HAS TO BE AT LEAST 9.5:1. Either buy the pistons or machine the head/block decks to achieve this..............the cam between 220 to 224deg @.050 with a valve lift around .460" a lobe seperation angle of between 110 to 112deg. ................a 600cfm carbie(prefferably a double pumper) a good dual plane alluminium intake manifold. Like a edelbrock performer rpm or a weiand stealth. a good electronic or dual piont ignition .the biggest bolt on headers(primary pipes)that you can buy off shelf.Either a twin 2" or single 3" freeflow muffler exhaust system. The carb can be as low as 500cfm for better fuel atomisation and throttle response...............yOU MAY also want to simply bolt on larger family heads and use machining to get compression up.........................Pistons I'd go for hypereutectics as they have a tighter piston to bore clearance than forged. However ,regarding pistons there are several manufacturers that can make any spec piston you want,although this is more expensive.....................Blowers/turbo They would definitely make alot more power on a 305! I dont care what the port size! Primarily because ,its FORCED IN AIR AND FUEL.Conventional flow numbers become virtually meaningless when the pressure is above atmosphere. Yes I would Max out the exhaust port and valve for a FORCE FED 305ci, but I'd leave the intake alone on a turbo application, with porting it mildly for a blown application...................Bottom line you could make 300hp with mostly second hand parts and some new ones. Heads,headers,intake manifold,carb and ignition can all be good condition seconds.Given the abundance of faith lacking 305 failures theres probably alot of performance goodies out there in the second hand markets and swap meets. A true car crafter would build the 305.

i totally agree with this post! not all car crafters are in it simply to go all out racing. some people just want something that is either better than stock or something that the big three never made. im all for building on the cheap, even if it means that i can't throw down with an equally built 350. why? b/c i built it, and that feeling alone is worth more than someone's 350 that was ordered out of a catalog. so, back to huntert's topic at hand, if you're capable or willing to learn to do the work, build the engine that will give you the same feeling i just described. good luck, no matter which way you go with your build from here!  

Concuer with mercman's assessment.  I know that some of you scoff at Hunter T for wanting to keep his car numbers matching, but to him it's important.  Who knows, one day that car might be worth alot.  Just look at the insane prices older iron is fetching on the auction block, and how that has impacted out hobby in general.  Like I said in another post, I'm watching people price absolute junk into the 9's and the sad part is people are paying what they're asking!  I watched a 71 Challenger (318 car) go for $9,000 recently.  It was an absolute rust heap with no interior and a blown engine!  I just use that as an example as to what Hunter T is wanting to do.  I wish him luck with whatever he decides to do with his ride.  

HillbillySailor:
Concuer with mercman's assessment.  I know that some of you scoff at Hunter T for wanting to keep his car numbers matching, but to him it's important.  Who knows, one day that car might be worth alot.  Just look at the insane prices older iron is fetching on the auction block, and how that has impacted out hobby in general.  Like I said in another post, I'm watching people price absolute junk into the 9's and the sad part is people are paying what they're asking!  I watched a 71 Challenger (318 car) go for $9,000 recently.  It was an absolute rust heap with no interior and a blown engine!  I just use that as an example as to what Hunter T is wanting to do.  I wish him luck with whatever he decides to do with his ride.

I actually fully support him keeping the thing original.  Prices of third gen Camaro's has gone up considerably over the past 5 years.  Used to be the really nice ones listed between 5-6000...but now those are just the ones in good shape...the really nice ones are going north of 8 grand.  

But take a look at those Muscle Cars that are numbers matching...the ones worth the most are the ones that have not been modified.  So IF he wants to keep it numbers matching...he should pull the engine and store it...drop something expendable in there...even if he insists on it being another 305.

But you are correct...its his car and we're just giving opinions on what we would do.  He has final say.  

You have 2 choices 1.Listen to the guys that think they know everything like the ones behind the counter at Advance Auto. 2.Listen to the guys that have tried what you are asking. We run a pro-stock dirt car and are limited to a given CID. We have to stroke that 305 that came in our firebird. We get 335 CID but with the cam, heads and pistons we use we make around 400 horsepower. We wind these motors to 7200rpm and beyond when we get in the front. Don't listen to the dumbies we are in the top 3 in points every year and if we can keep the fans on it we may see the ship trophy in the case. We use a solid cam that has lift and duration numbers that mirror a big block. We use dome pistons with 12:1 compression but you don't need that much on the street. 300 hp isn't a problem just talk to the older guys or go to the dirt track and talk to the street stock or pro stock racers.
Good luck.  

Wow, now just imagine how much more power you could make with less stroke, more bore, and more head flow capability!  

67401rambler:
You have 2 choices 1.Listen to the guys that think they know everything like the ones behind the counter at Advance Auto. 2.Listen to the guys that have tried what you are asking. We run a pro-stock dirt car and are limited to a given CID. We have to stroke that 305 that came in our firebird. We get 335 CID but with the cam, heads and pistons we use we make around 400 horsepower. We wind these motors to 7200rpm and beyond when we get in the front. Don't listen to the dumbies we are in the top 3 in points every year and if we can keep the fans on it we may see the ship trophy in the case. We use a solid cam that has lift and duration numbers that mirror a big block. We use dome pistons with 12:1 compression but you don't need that much on the street. 300 hp isn't a problem just talk to the older guys or go to the dirt track and talk to the street stock or pro stock racers.
Good luck.

So all it took for a 305 to make 400 HP was winding it to 7200 RPM, adding 30 more cubic inches, using a massive solid lifter camshaft, and using a race gas friendly 12:1 compression.  Seems reasonable...  

I'd stick with the build I listed earlier if you want to build one of these boat anchors...367 HP in a REASONABLE package for the street.    

The only suggestion i can make considering my limited abilitys and knowledge on performance is to do what my cousin did, Put 350 heads,Intake, And Cam on your 305 and top it off with an elderbrock 650cfm Carb, it seems to work pretty well for his monte carlo