You could get 250 with above mods and maybe a mild cam

 

Google is your friend

Throwing money at a 305 isn't advised, but if you stick with bolt-ons they'll transfer over to the 350 you'll wind up with eventually.

 

The L69 is already pushing it for a 305. It's got decent pistons, head, cam, intake, carb, exhaust, all from the factory. You're not going to see the same gains that you'd see modding a 140hp LG4.

People don't say to get a 350 because of some prejudice against the 305, it's sound advice based on decades of experience.

 

Not the numbers your probably looking for; you might be better off just leaving it as-is and enjoying what you have. Why molest a good original HO Thirdgen car to try get something that you're probably not going to get - simply because of what you are starting with. The HO is a fairly quick ride, not much to brag about these days,....... but still pretty fun to drive. The second you modify your low-mile HO it's worth less $$ and desirability,... and how much will headers and an intake get Ya' ??? 15--20HP ?? Just not worth it -----> IMO !

Since $$ isn't a problem for you---> just buy a car that already has the potential to build up to the HP you desire.

 

Search member Ja85z28 and read what he did to his.

 

It's tough to get a 305 to breathe enough to produce significant power; the cylinder heads are the limiting factor, and the small bore size doesn't allow larger valves. A cam, headers & exhaust, intake, carb, and ignition system might get you maybe 25-30 horsepower.

What is your issue with replacing the 305 with a 350? If it's $$$, the cost of the above mods to the 305 are close to being enough to cover a Good Wrench crate 350.

 

 

If money is no problem, skip the 350 and go sbc 454

 

 

I said S B C 454.... You said money was not a problem...., right?

 

Modifying a 305 isn't very rewarding. If you want to keep the 305 then I might suggest doing the typical cheap and free mods and leave it at that.

A supercharger would make quite a bit of difference and be reversible back to stock anytime you want.

 

I think you live in Chicago....? There isn't a mountain within a thousand miles

 

 

LS swap + turbo $20,000 500rwhp reliable car

Thats about the only option I see anymore for daily drivers

 

Exhaust and rear axle gearing, best two mods for that machine. Much like the Monte Carlo SS back in the day.

 

I done headers and cam to an LG4 once and it was still a bit slower than my LB9 car I got a few years later to my surprise. If you bother with a 305 you probably wont be happy performance wise. Not saying its not a good engine because they are peppy and run forever, but a 350 is so much better for the $ I would never spend much on a 305.

 

Well, a thousand miles will take you to either ocean, Alaska, Mexico, etc. My geography is lousy but Has to be a mountain in there somewhere.

Couldn't resist.

 

Good thing you weren't a pioneer settler heading west from Chicago because you would have run out of supplies and died somewhere in the grass plains of Montana less than halfway to the West coast.

 

The 305 in my 1980 Vette was still mild and trapped 110 mph in the low 12s on drag radials with a TH350C and 3.07 gear behind it.

It was a flat top piston, .040" over 305. Ported Vortec 305 heads (059 casting) with 1.94/1.60 valves. Crane 272H10 cam with 1.6 rockers. Edelbrock Victor Jr single plane intake manifold. 500 cfm Edelbrock carb. Long tube headers and a pypes 2.5" dual exhaust with magnaflow mufflers. 3,000 rpm lockup converter in the TH350C. It idled 750 rpm with the a/c on and still pulled down 25 mpg highway.

I also had what amounted to a roller cam L69 with bolt ons in my old G20 van. It was a .030" over Vortec 305 block, flat top 1.56 compression height pistons zero decked, F-car LT1 cam, and 53cc 14022601 heads. An Edelbrock Performer RPM intake, tweaked Q-Jet, recurved HEI, 1.6 roller rockers, Thorley Headers and 2.5" exhaust with a X-pipe before the high flow cats and magnaflow mufflers. With a 2,800 stall converter in a 700r4 and 3.73 gears. It ran a 14.8 @ 94 in the big van. It idled 550 in drive with the a/c on and would get better than 20 mpg running 75 mph.
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My brothers old 1980 C10 went into the 13s with the shortblock from the Van. Ported 059s with 1.94/1.60 valves(later those were on the Vette), GM 845 cam, GM dual plane carb intake off a 330 HP 350 HO, Q-Jet, recurved HEI, shorty headers from a 1998 Vortec truck, dual 2.5" exhaust. Using a 3,000 stalled TH350 and 3.08 gears.

 

Stock Bore & Stroke
LB9 = 3.736 x 3.480
2JZ = 3.390 3.390

Stock Valve Sizes
LB9 = 1.85/1.50 (two valve)
2JZ = 1.32/1.14 (four valve)

Simply put, a 1.94" valve is all the valve a naturally aspirated 305 will ever need to make great power (for its' size). If your 305 is boosted like mine, then sure you can try to swing 2.00+ valves in there for more room up top, but it's not really needed. It's more about cylinder head flow and cam characteristics when it comes to a naturally aspirated 305, but again, you won't see as much as you would with a larger engine. Free mods are meaningless in my opinion, if you're not going to pull the heads and get a better cam, then don't even bother.

- Rob

 

Add to that intake manifold, fresh valve springs and 1.6:1 roller rockers to get a little more lift out of the stock cam. Testing even an edelbrock performer manifold over the stock manifold on those cars back in the day showed a 20 hp increase and a measurable 2-3 tenths off the track times.