I've got a young friend who purchased himself a Chevy truck with a 305. I told him it's a dog. I told him to just get a 350. He's hell bent on making the 305 better.
how do we do it on a high schoolers budget? (FYI- I know NOTHING about old "muscle car" engines)
Edit: I think he would be happy with about 300 to 350 hp.
Start with this: https://www.hotrod.com/articles/engine-masters-ep-13-asks-much-nos-305-take-305-take-nos/
Then when the engine scatters itself, go get a 350 to start over with.
Edit: getting an old 305 to 300-350 HP is unlikely to be cheap or easy. If it is pre-Vortec, a set of Vortec heads, a cam, intake manifold, headers, and an appropriately sized carb can get you part way there.
The run of the mill 305/307 engines are mostly dogged by low compression, low flowing heads, and a bunch of bad emission devices imo. You might look into a good set of mid '80s higher performance Camero/Firebird/Monte Carlo heads and intake/carb. Otherwise, I'd suggest that your friend just drive it like mid powered truck.
In reply to Vajingo :
It can be done, but not on a high school budget. A good intake, cam, long headers... you can improve it, but 300 isn't happening without better heads, which will need small valves because small bore, and those small valves will still be somewhat shrouded. I think(?) you can put vortec heads on a 305 for a much better port and a bump in compression, but I'm not sure you'd see the gains available from a larger bore engine.
For a truck, on a high school budget, if he's just wanting to blast the throttle from a stop, I'd stop looking at the engine after installing decent mufflers. I'd instead throw some aggressive gears at the rear end and do sway bars and lowering (or cut, since high school budget) springs.
If you replace everything but the block, keep the displacement the same, you can make a pretty stout 305.
The bore on the 305 is too small to do anything performance, especially on a high schoolers budget. Put a set of cherry bombs on it and at least be loud I guess?
In reply to barefootskater (Shaun) :
Shaun is 100% correct on the engine. You can make a nice useable bump in hp/tq by doubt the things suggested, but the gain will not be a lot.
The gear swap,while fun, if driven for fun, is going to do terrible things to the gas mileage... could actually help mileage, driven like a little old lady; but I doubt y’all would!
Cheapest answer is turbo.
Back when my trans am had the factory 305 in it I messed with it a hair. LT1 cam ($25 off ebay), Holley Stealth Ram, random flowtech longtube headers and some tuning put it at I think it was ~240ish wheel hp through a t56. Getting into head swap territory just doesn't make any financial sense unless you get the heads for free.
If the truck is TBI, Google will give him plenty of paths to go down to increase flow. If carb'd then there are a lot more options. All the typical bolt-ons work and many would transfer over should he put a 350 in down the road. Gears and a shift kit for the (presumed) automatic will make it feel a lot more lively and responsive. Trick Flow has 305 specific heads available, look to be around $1300 for a pair. Put a mild cam in and it should be a competent motor.
I know people have always ragged on the 305 and it isn't necessarily optimal, but use what you've got. When it blows up, re-evaluate things. It's like if you've got a classic 289 Mustang, you don't just throw the 289 away to drop in a 302 for no reason. Sure the 302 is better, but plenty of people have made lots of power and had lots of fun with 289's.
I've had some time lately to think through a 305 build for a possible project in the future that I hope to get into. Think GM G-body's and how many got 305's as to why, and also it needs to be cheap. Here's what I would like to try and pull together, again on the cheap;
This probably isn't a 300hp engine due to the L98's being an okay truck head and the sub 9:1 compression ratio that they + a stock 305 come in at. But it might be close and I would imagine it comes in around 300lbft of torque. None of it is exotic and should be findable at the junk yard, swap meets, etc.
I also agree with barefootskater that a set of gears and a DIY cat-back exhaust is probably going to be "more fun for the money" than a top-end engine upgrade. Honestly just about any 305 that hasn't been rebuilt yet could probably use a rebuild later and these parts could be stockpiled for that eventuality (or added to a different block with a bigger bore like a 350's).
Thanks folks. I'm dropping the link to him now so he can read this.
I'd put an exhaust on it because V8 rumble and start scrounging 350 parts.
Ebay turbo kit .
Headers and short bullet mufflers. Nothing makes a dog V-8 sound faster than that.
Last time I tried to do anything 'beastly' with a 305, it ended up looking like this:
'Course, that was almost 40 years ago... 
I betcha he can find a 350 shortblock and some used decent heads for not a bunch more money than trying to jam a bunch of air through tiny valves into a tiny bore. Anything he does to make the 305 quicker involves heads off, anyway.
I might still have a set of 307 heads somewhere that would bump the compression some, and are thick enough to lose another 30 thou off the surface.
Not really a lot of 307's hanging around the junkyards anymore, I bet.
I agree that 300 hp from a low or even mid level modified 305/307 is really pushing it with any budget, let alone a high schooler budget.
Wife and I have a '67 Buick 2 dr Buick Skylark with an older SBC/Saginaw 4 spd conversion (it was originally a V6 with a 3 on the tree). The block checks out to be 307 out of a '72 C10 truck. The heads, intake and QJ carb are mid '80s Camaro/Firebird stuff. We were told by the PO that the engine was bored out... How much it was bored out is anyone's guess. My worthless estimate is that it's producing maybe 225 or so HP. Anyway, this long and heavy car looks good (to us anyway) while having plenty of power for the cruiser/rat rod that it is. But it is not in any way shape or form a muscle car.
Do headers and dual exhaust with glass packs. It won't hardly make any more power, but it will be way louder, and to a high school kid that's the same thing.
Javelin (Forum Supporter) said:The bore on the 305 is too small to do anything performance, especially on a high schoolers budget. Put a set of cherry bombs on it and at least be loud I guess?
Vortec heads.
If it already has them... decent cam, decent exhaust, good 'nuff?
LT1 heads WILL clear a 305's bore. They fit a 4.3 V8, which is basically a 305 with a 3" stroke. But it is a TON of work to make LT1 heads work on a small block, so the easy button is Vortec heads, which are more-or-less LT1 ports in a SBC casting.
Appleseed said:Headers and short bullet mufflers. Nothing makes a dog V-8 sound faster than that.
IMO it makes them sound really slow. Lots of noise for no actual output, like a Diesel.
*dodges and ducks*
FMB42 said:I agree that 300 hp from a low or even mid level modified 305/307 is really pushing it with any budget, let alone a high schooler budget.
A 307 is just a stroker 283, and there is plenty of fun to be had with those. Chevy never made a high performance 307, though, because by the time they started shoving 327 cranks in 283 blocks, they were focused on 302s and 350s, so the 307 was always a budget/economy engine, and GM's attitude was "eh, if you want better, buy something else"
A 305 has an even smaller bore than a 307, and a much longer stroke. So it's more constrained as far as valve area and shrouding is concerned.
$700 is in a high schooler's budget, right?
I wonder how much a LT1 swap would be. Those things cheap
You didn't tell us what the truck was. Carb vs TBI vs Vortec makes a difference.
In any case, just start with deeper rear gears (I hope it's 2wd). To keep it reasonable on the highway I'd go with 3.42's if no OD, and 4.10's if it has OD. One step deeper if 4wd with stockish tires. Shift kit if automatic, "corvette servo" if 700R4, and adjustable vacuum modulator on any non-computerized trans to raise part throttle shift points. With 4.10's and a 700R4, 1st gear should feel pretty darn good even before you mess with the engine.
Others have covered nearly all the engine stuff, which can be summarized as "all the usual small block chevy stuff". Start with exhaust. If going with headers, get the smallest primary tubes you can find (in reality, you'll end up with 1 5/8, which is too big for a 305, but nobody wants to hear that, so nobody makes them). 3" single exhaust will be plenty, 2" is big enough for duals, and he can add bigger tips to avoid embarrassment if necessary. Most people like milder cams than they think they do, so keep intake duration no greater than 210 degrees @ .050 lift, especially with the awful pre-Vortec heads. If it's a carbed engine, a quadrajet will work best, but they're the hardest to set up . If it's a TBI engine, go to thirdgen.org and read and read and read - all the answers are there. Vortec engines have limited intake options but much better heads
Pete. (l33t FS) said:Appleseed said:Headers and short bullet mufflers. Nothing makes a dog V-8 sound faster than that.
IMO it makes them sound really slow. Lots of noise for no actual output, like a Diesel.
*dodges and ducks*
It's a kid. He doesn't know what fast is yet. Sounding rowdy sounds fast.
If we're talking actually fast spray it. Nitrous it till it tops. It's a 305. It won't be missed.
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