Help me make a 305 “beastly”.

Richard Holdener did a bunch of low to mid budget testing on 305s.

Appleseed said:

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.

This is absolutely true. I've tried to convince him several times that my 180hp NC is quick. He's new blood. He can only see the YouTube Heroes that crank out a 1,200hp dyno pass
*ONE TIME*

and then live on in infamy from it. 

Glasspacks.

Every kid needs a car that's loud enough to set off car alarms and/or wake the dead.  At least while they are young enough to enjoy/appreciate it.

The rest isn't going to matter.

And loud pipes give the illusion of power.

Show him this post so you're not the one who looks like a jerk.  Brutal honesty from a life-long hot rodder with a bit of hyperbole thrown in.

305s are limited by their small bore.  There is no way to make a 305 breathe like a 350 or other larger-bore small block.  They are also primarily lightweight castings that were never designed to handle any decent power, they were used during the smog/malaise era to try and appease the V8-loving public while consuming as little fuel as possible.

Here are some recipes for making 300 hp:

Take a 305 out of the car.  Remove the intake and heads.  Port the heads until you are afraid of hitting water, then port them some more.  Have spare heads on standby ($200) for when you do hit water so you can try porting again.  Do a 5-angle valve job because you can't really go with bigger valves without shrouding and killing flow.  ($300).   There is no way of getting enough meat milled off the heads to get compression up past about 8.4:1, so another option is to purchase 305-specific performance heads that no one will buy down the road if he ever sells them ($1200).  Cam and lifters ($250) intake ($200), headers ($300), valve springs, retainers, rockers ($400), higher stall converter ($300), rear gears ($500), gaskets ($200)

Or, alternate recipe... buy junkyard Vortec 350 longblock ($400), add a marine vortec carb intake from a boat salvage yard ($50), mild cam ($175), re-jet the Qjet ($30) and re-use all of the other stuff from the 305.

The whole idea of modding a 305 because "it's what I have" is complete horse dung.  If you want to spend thousands of dollars to make a 305 seem fast, be prepared to A) lose to someone who spent $200 on their 350, B) never be able to recoup your costs when you sell, C) have a potentially less-streetable vehicle because of the higher torque peak, and D) have a less-reliable motor when the mains decide they've had enough and eject the crank through the oil pan.

The 305 might be 87% the displacement of a 350, but is doesn't even come close to 87% of the performance potential.  Building a 305 (to this hot rodder) is the equivalent of thinking stickers and a plywood wing gives you horsepower.  Any time I see someone modding a 305 to make more power, I have to wonder how bad they are at math.  You can easily spend multiple thousands of dollars getting a 305 to 300 hp, or you can spend under a grand and have 350 hp from a 350 with more torque and a viable, sale-able vehicle that will likely pay for itself when you sell the vehicle later.

There.  I said it.

A 305 shares the SBC architecture, but that's where the similarity ends.  Tiny bores, terrible breathing, weak blocks, and zero street cred.  In fact, the 305 invented negative street cred, and it scores negative eleventy.

bigbrainonbrad said:

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.

Negative, ghost rider.

Comparing 289/302 to 305/350 is not a real-world comparison.  The 305 (dear god... ESPECIALLY the TBI 305) is a non-starter.  The 289/302 is at least an apples to apples comparison of displacement.  He can start porting those swirl-port heads, but they are the single worst-flowing head that chevy ever put on an SBC, period.  265 heads from the 50s flow better than 305 swirl ports.

Stick with the "it's a dog" approach, because it seriously is.

Honestly... you mentioned three specific things:  1) high school budget 2) 300-350 hp and 3) TBI 305.

Pick two.  The engine represents the absolute worst starting point.  High School budget and 300 hp?  Easy with a 350.  300 hp and a TBI 305? Not happening on a high school budget.  High School budget and TBI 305?  Not going to get 300 hp.

I'm also seeing a lot of nods toward the vortec heads.

Things to know about "vortec" heads:

- when old school folks talk about vortec heads, we are referring to heads from the 5.7L from 96 to 98 that have casting numbers ending with 906 or 062. 
- The vortec name was used on everything from V6s to LS engines.  The magical unicorn ports in what we refer to as vortec heads only happened in those two 350 head castings. 
- The vortec heads for the 305 were basically TPI 305 ports and are nowhere near the flow.
- Putting 906 or 062 heads on a TBI 305 will drop the compression into the 7s.  Putting 305 Vortec heads on his TBI 305 will cause him to spend lots of money on the intake side for very little gain.

Hence why the 305 is the ugly child in the SBC family.

SkinnyG (Forum Supporter) said:

Glasspacks.

Every kid needs a car that's loud enough to set off car alarms and/or wake the dead.  At least while they are young enough to enjoy/appreciate it.

The rest isn't going to matter.

And loud pipes give the illusion of power.

Best friend from high school had a Z71 with Purple Hornies.  He loved that damned truck.  I did too.

My very strong recommendation is to do mods that stay with the truck, but aside from changing the oil or spark plugs, I would never spend a dime on a 305.  Sorry for sounding like an asshat, but it would be wasted money.  As soon as you spend $250 on a 305, it's basically cheaper (and gets more power) if you just buy a 350 longblock.  This is even more true with the TBI.  The ECM uses a PROM chip which means every tuning change requires multiple chips to be "burned" to work with the new components.  They are highly sensitive to changes.  It's not like you can just swap a cam and plug it into a laptop.  You have to find someone who knows these tunes like the back of their hand and since no one mods a TBI 305 and hasn't since 1995, your options for finding someone who can do it are likely zero.

Exhaust.  Start with exhaust and a chrome air cleaner cover.  Create a diversion.  Make it sound cool.

In reply to Curtis73 (Forum Supporter) :

Curtis, for a guy who has admitted liking the Chevy 350 diesel, you seem to have more than the usual amount of 305 hate. You're a mystery my friend. 

Just use the standard SBC stuff.

Hang as much Edeltorque gak off of it as possible.

Add some crappy headers and a set of flowmasters.

Bolt on a carburetor that is far too big.

Tell everyone it's a "Corvette engine".

Don't forget the bowtie floormats and a "heartbeat" pinstripe.

Welcome to Chevy ownership.

I'm allowed my opinion, I owned a Firebird with the only SBC worse than a 305. The 267.

barefootskater (Shaun) said:

In reply to Curtis73 (Forum Supporter) :

Curtis, for a guy who has admitted liking the Chevy 350 diesel, you seem to have more than the usual amount of 305 hate. You're a mystery my friend. 

I said what I said 

But seriously... I like the Olds 350 diesel because it is just head studs away from being a totally competent motor.  You can't fix the 305's tiny bores.

(and honestly, my 305 hate posts were an attempt to jump-start Vajingo's young friend into legit hot rodding by steering him away from the 305 so he can still afford college)

Where is your buddy located? I'll bet we could find a Craigslist/Faceballs 350 deal for him on the cheap.

In reply to ShawnG :

I also had that teeny-tiny 267 in a '80 Malibu Sport Wagon (same paint scheme as the pace car) Some one at GM said to the bean counters "Hey, the public thought we were helping them save gas by taking the same stroke as a 350, and giving it a smaller bore for a 305 (as pointed out it shrouds decent valves) so lets use that same stroke and give it an even SMALLER bore. They will really think they are saving gas!"

Truth be told, stock, it had about the same power as the Buick 231 (called 3.8 in' 85) in a 4 dr G body I had.

Going into it knowing I would not see big gains, I did a aluminum intake, well tuned q-jet and proper curved HEI, hedars and exhaust, and was quite happy with it. Never was expecting any 300 HP out of it, but it was a nice "crisp" running engine.

BTW, the Chebby crowd attitude you are describing is seen SO often! There were more "corvette engined" cars at my H.S. than corvettes ever made!

Curtis73 (Forum Supporter) said:

 ... it is just head studs away from being a totally competent motor.  .

A good description for my current maligned 6.0 Ferd diesel! Ok, that and an oil cooler mod...

Curtis73 (Forum Supporter) said:

I'm also seeing a lot of nods toward the vortec heads.

Things to know about "vortec" heads:

- when old school folks talk about vortec heads, we are referring to heads from the 5.7L from 96 to 98 that have casting numbers ending with 906 or 062. 
- The vortec name was used on everything from V6s to LS engines.  The magical unicorn ports in what we refer to as vortec heads only happened in those two 350 head castings. 
- The vortec heads for the 305 were basically TPI 305 ports and are nowhere near the flow.
- Putting 906 or 062 heads on a TBI 305 will drop the compression into the 7s.  Putting 305 Vortec heads on his TBI 305 will cause him to spend lots of money on the intake side for very little gain.

Hence why the 305 is the ugly child in the SBC family.

Don't the good heads fit a 305?   That's the ones I'd go for.

Interestingly, didn't Chevy truck engines get the Vortec name BECAUSE of those early swirl port heads?  I know some engine builders like them for truck engines because they claim excellent moderate-load economy with them... which is kind of why Chevy did what they did.

03Panther said:

In reply to ShawnG :

I also had that teeny-tiny 267 in a '80 Malibu Sport Wagon (same paint scheme as the pace car) Some one at GM said to the bean counters "Hey, the public thought we were helping them save gas by taking the same stroke as a 350, and giving it a smaller bore for a 305 (as pointed out it shrouds decent valves) so lets use that same stroke and give it an even SMALLER bore. They will really think they are saving gas!"

I had this exact car in High school. What a turd of an engine. My dad and I were going to yank it out and install a supercharged 350 in it until I wrecked it and bent the frame. Even back then we knew the 267 and 305 were economy engines not worth putting any money into for mods. this was 1988-89.  Off topic but also the speed limiter was about 87 to 90 mph, stupid limit!

I agree with the "if you can't make if fast, make it loud" school of high school truck modification. Just make it sound cool. Put in a good stereo that you can hear above the exhaust. That should run him out of money right there. 

Let me just say I agree.

If said kid is in love with this as a forever truck, do all the things to it.  Carb, cam, all the parts, then replace with a good engine when it blows.  If not a forever truck leave it alone and make it sound cool.

Side note, does this all apply to the 305 in my boat?  1998 two barrel Mercruiser, when I want more power just swap to a 5.7 and hope the drive holds.  Or sell it and get a better boat?

akylekoz said:

 

Side note, does this all apply to the 305 in my boat?  1998 two barrel Mercruiser, when I want more power just swap to a 5.7 and hope the drive holds.  Or sell it and get a better boat?

Yes. One of those. Pick one. 

For anyone interested, this $112 cam kit from Summit (hydro flat tappet lifters, not rollers) should be a decent improvement over stock and have a noticeable but not extreme idle;

CHEVROLET Summit Racing SUM-K1103 Summit Racing® Classic Cam and Lifter Kits | Summit Racing

For another $35 here's a double roller timing chain set from Comp; COMP Cams 2100 COMP Cams Magnum Double Row Timing Sets | Summit Racing

I saw someone say a timing set for a 305 would cost $250 and I figured an example of something different might be interesting.  Juice roller cam kits are a whole different situation and cost over $450 from what I'm seeing this morning so that's something to be aware of as well. 

In reply to akylekoz :

Mercruiser EFI with the 305 will result in 260 HP.   I'm not sure what they do internally but as discussed elsewhere marine engines are generally tuned more for torque than horsepower.   My dad has a 2005 Chris Craft Speedster with this engine and switchable exhaust (through hull or through prop).   It makes all the right sounds and will run right up to 5,000 RPM / 55 mph.   The two barrel you have is likely rated at 230 HP and yes the easy button is to find a good Mercruiser 5.7 with a 4 barrel to get to 260 HP.   There are a lot of them around, no need to get into complicated modifications.    As far as the drive, an Alpha is typically OK up to 300 HP as long as the combination isn't in a heavy boat.   (20 -21 footer with 300 HP / Alpha, generally not an issue)   I have a 1988 22 cuddy cabin with the 5.7 / Alpha drive and over 800 hours in fresh water and it's been fine.   The sport boat guys used to put a drive "shower" that sprays water on the upper gear case to keep that part cool and together in the days before Bravo drives.

Sometimes paradigm shifts are hard for a teenager.   Wise teens learn from the mistakes of their elders.   

This one seem like he would rather learn from his own mistakes, and then admit the 350 drop in was really the "easy button" after all. 

This learning experience could potentially turn him into a wise person.

A 5.7 / 350 with an Alpha should live fine.  Marine 350s were typically somewhere in the 260 - 300hp range, depending on Vortec or pre-Vortec and carb vs EFI.  Most of the issues with the Alpha drives were when they tried putting them behind big blocks.  A 340hp 454 requires gentle treatment of the drive to not blow things up...  So after a few years, the big blocks became Bravo drives only. 

I believe we got him into the "305 bad, tree fiddy good" camp now. Thanks fellas

Pete. (l33t FS) said:

Curtis73 (Forum Supporter) said:

I'm also seeing a lot of nods toward the vortec heads.

Things to know about "vortec" heads:

- when old school folks talk about vortec heads, we are referring to heads from the 5.7L from 96 to 98 that have casting numbers ending with 906 or 062. 
- The vortec name was used on everything from V6s to LS engines.  The magical unicorn ports in what we refer to as vortec heads only happened in those two 350 head castings. 
- The vortec heads for the 305 were basically TPI 305 ports and are nowhere near the flow.
- Putting 906 or 062 heads on a TBI 305 will drop the compression into the 7s.  Putting 305 Vortec heads on his TBI 305 will cause him to spend lots of money on the intake side for very little gain.

Hence why the 305 is the ugly child in the SBC family.

Don't the good heads fit a 305?   That's the ones I'd go for.

 

Interestingly, didn't Chevy truck engines get the Vortec name BECAUSE of those early swirl port heads?  I know some engine builders like them for truck engines because they claim excellent moderate-load economy with them... which is kind of why Chevy did what they did.

The good heads do fit a 305, as long as you get the associated intake to fit the different pattern and port location.

The problem is, 350 vortec heads on a 305 are a terrible choice without tons of supporting mods... including a complete teardown and new pistons.  His 305 is currently about 8.5:1.  With the bigger chambers in the vortec 350 heads, he'll be at about 7.6:1.  He will also now have 1.96" intake valves that will be darn close to touching the cylinder walls and the flow will be choked.  The new pistons will also need to be domes which slows flame front speeds... basically, he will be making an assembly that makes less power and torque, needs an even smaller cam, consumes more gas, and would likely need to have the timing locked at 36 degrees BTDC to make it work.  He will effectively take a 4500-rpm wheezer, and add even more wheeze that runs out at 4000 rpm instead.

Many guys have used Vortec 350 heads on something like a 302 to drop compression for forced induction, but in that case, the 302 shares the same bore diameter with the 350.

The honest assertion here is that with a 350, nearly anything you do to it will be an improvement because it's moving in the right direction.  In the 305, anything you do to it might have one benefit with three downsides.  Like the vortec head swap... you get superior flow, but you tank compression and shroud the valves for a net loss.  You can toss a turbo on it, but the tiny ports and swirl vanes will cause constriction, additional heat, and port surge/stall.  The whole point is that if you simply add $500 to your budget to buy a good running 350 longblock of your choice, then you'll find you usually recoup those costs by not having to crutch all the other stuff in a 305 trying to chase hp.

So, 305 with vortec heads, teardown for new pistons, rings, possible machine work/hone/bore, cam, intake, burning a chip that might be unobtanium... you're looking at multiple thousands of dollars and you still have a wheezy, small bore engine that few people will want to buy and every grease monkey will laugh behind its back.

OR... Drop in 350 vortec longblock for $500 for 280hp in an afternoon, get more torque, have a more desirable package for when he sells, and easy to add a few more degrees of cam and some headers and get 325hp easy.  Ok, it's not really that simple, but almost.

Here is what you need to know about TBI vs Carb vs Vortec intakes.

- carb intakes have 6 bolts per side and all 6 of them go perpendicularly into the heads (45 degrees to the ground.)
- TBI intakes also have 6 bolts per side, but the two center bolts point straight down (90 degrees to the ground/45 degrees to the head)
- Vortec intakes have 4 bolts per side and all of the bolts are straight down.  They got rid of the center bolts entirely and there are just bolts around the intake ports.
- Vortec intakes are also made with 1/4" higher intake runners to match the higher intake ports on Vortec heads.

Mix n Match between Carb and TBI intakes is pretty easy.  The center holes in the intake you can use a die grinder or drill bit to wallow out the holes and then make or buy wedge-shaped washers to adapt one to the other, but a Vortec head really needs a vortec intake.

Here is the big conundrum you face with that specific 305.  The pistons are dished.  Your only hope of increasing compression (a requirement to get anything close to something that works with the cam you'll need) is to either swap pistons or find a smaller-chambered head which I don't think exist.  The heads that are on it are the worst-flowing Chevy head ever produced.  The cam is tiny.  Like 181/189 duration tiny.  The TBI's ECM is a PROM and very sensitive to changes without burning a new chip.  The bores are small, and won't take much of an overbore.  Maybe .020".  The block is a lightweight casting and not overly durable.  The TBI unit flows around 390cfm.  In truth, GM did an amazing job of putting together a well-matched engine.  Everything works together beautifully to make 165 hp.  The downside is, that means nearly everything has to change to get it to be a matched system to make 300 hp.  We are talking about doubling the hp.  It's not like an LS where everything is there just waiting for you; compression, head flow, and a flexible ECM.  With a LS, you stab in a cam and springs, plug in your laptop, and boom... 100 extra hp on a weekend.  With a 305, it will take serious money and parts to double the hp.  With a 350, it's much simpler.  Kinda half way between a 305 and an LS.

The Vortec name started earlier than the swirl ports if I recall.  I know it was used as early as 1985 in trucks and vans, but they didn't have the swirl port until 87.  The Vortec name was also used on dozens of 4, 5, 6, and 8 cylinder engines, some with swirl ports and some without.

This may have been answered, but I didn't see it.... smog requirements?  Opening up the world to different inductions can make this a cheap endeavor.

Back when I was building (jeez... it's probably been 15 years since I built an engine), I did a bunch of really fun truck-type 350s.  Vortec longblock, marine vortec carb intake (because I could get them cheap at the boat junkyard), mild roller cam, tuned Qjet and an HEI.  If I used a stock cam (196/206) I was squarely at 290 hp with headers.  Step up to a Melling 204/214 I was right around 325hp.  9.5:1 compression and 87 octane all day with a nice low rpm torque peak, and it didn't cost much.  I used to get longblocks on flat-rate day at the U-pull for $250.  That's probably more like $500 now.

There IS a factory TBI intake made for Vortec heads I think.  The last year of the TBI in the vans (late 90s) I think they moved forward with vortec heads but kept the TBI, meaning there is a junkyard somewhere with a factory TBI/Vortec.  Might save you from buying an expensive aftermarket intake if he needs to keep TBI.