ok so i know a lot of people think its stupid to rebuild the 305 but in a few months i have a feeling im going to need to make this decision. i have a few questions. if i put a diffrent crank in it a cam and new heads. how big of a diffrence would i see in power?

 

I would belive you would get a some of a change i changed just the heads and put some small tube headers on my trans am 305 and got a 50 - 60 horse gain on the dyno but engines are never the same as another

 

It depends which heads you put on, and whether the cam matches.

Putting only a different crank in without changing anything else won't net you anything, because you won't be able to change the stroke without changing the rods and/or pistons. Even still, changing the stroke is ill-advised and a waste of money unless you're changing the bore as well.

 

well i was thinking of a .30 bore. i just wanna know a rough estimate on the numbers i would be pushing with this setup. if i leave the stock crank and bore it .30 with new heads and a cam and intake?

 

An overbore doesn't count, it only increases the displacement by less than 2%. "Changing the bore" means tossing out the 305 and building a 350.

Otherwise, it still depends on what heads and cam you use.

 

To get most out of 305 (as have been mentioned before) the biggest contributors to performance increase are:
heads
camshaft and CR bump (new pistons)
exhaust
and have custom tune to support additional fueling required by this combination

+other
//RF

 

does anyone in here kno if the chevy double hump heads would be good on a 305 and if they would bolt to the tbi intake.? im not worrried about the no ac deal.

 

Double hump heads are 40 year old technology that probably won't mount your accessories without a lot of changes. There are more recent heads which are more suitable.

 

i kno they are old but iv herd some guys swear by them plus i can pick up a set for 100 that have been gone through and are pretty much brand new. any suggestion for heads that fit the tbi intake?

 

There are not many direct replacement heads around.
http://www.summitracing.com/parts/TFS-30300005/
http://www.summitracing.com/parts/WRL-042750-1/
or 081 TPI heads.

 

This, TFS Super 23 305 head will be infinitely superior.

 

Really, the 305 is a waste of time if you're looking for any sort of reasonable increase in power. You'll be much, much happier, if you just go pull a 350 from a salvage yard, and rebuild that.

Most salvage yards have a "half price day", usually in the middle of the week. So if you go pull an engine on half price day, you can usually get one for less than the cost of those heads you're looking at.

Rebuild it now, and when you're ready, you can do the swap in a weekend, and not have any extra downtime on your ride. The power increase of a stock 350 is going to be significant, over whatever you do to your 305. If you spend a little extra, and do a few upgrades to that 350 while you're at it, it's only going to get that much better.

 

i am trying to keep the tbi also i wanna be able to say that all i have is a 305 and be able to keep up with some of the newer camaros and rustangs/ i dont want to get beat by a honda either lol

 

Given all factors are equal, and relative to the displacement of the engine where appropriate, a 350 is 15% better than a 305. Everything but the pistons and the size of the combustion chambers are the same.

Also, you can buy a brand new 350 short block from GM for around $1500 or cheaper. Admittedly it's not filled with any forged components, but it's ready to rock and roll and can handle 400 hp.

 

It's more than just the 15% displacement difference in the end. The 350 gets better air flow through the valves with the larger bore.

 

If you pull the injectors from the 350 along with it, you can keep everything else stock. Find a fuel map for the 350, and you can usually find somebody willing to burn you a chip for free, with the map you provide.

Or you can pull the ECM, or chip, along with the engine and injectors, and be ready to rock.

No matter what you do to a 305, you're not going to hang with a new Camaro, with TBI. It's just not going to happen.

If you're looking for performance, go with the 350. They breath better, more displacement, and generally are just a better engine for anything other than fuel economy.

If you're looking for economy, keep the 305.

You'll sink a lot of money into a 305, trying to make what a 350 puts out bone stock, and you'll STILL get beat by most cars on the road (including a lot of Hondas).

I was once where you are now. I was convinced I could build a 305 to be just as strong as a 350. My reasoning was the same - bragging rights.

"I'm such an amazing engine builder, that I could do what millions of dollars of engineering could not. I've defied the laws of physics, and did it all on a budget of $300."

It's not gonna happen, man.

If you want more power, either go to the 350, or look at some sort of a port injection setup.

You'll be much happier in the long run.

 

This isn't actually true. The 305 has bigger valves per cubic inch than a 350. You can talk about shrouding all you want, but a 350 would need 2.11/1.72 valves to match the area per cubic inch of just 1.84/1.5 valves on a 305.

The main reason you can't make as much power with a 305 is you don't have the wide selection of cylinder heads available. The 305 always has been a kinda black sheep of the performance small blocks. Low flow heads for good port velocity and small cams.

 

We can talk about the REASONS that the 305 is limited in the power department, until we're blue in the face.

Ultimately, though the end result is the same. 305 just isn't much of a power plant for putting up decent numbers. Even if you bolt on a good set of performance heads off a 350, the numbers still just aren't there.

 

Exactly, 15% displacement advantage isn't much for say a 1.6L Honda, but on a 5.0L V8 (which isn't exactly small to begin with) it's a pretty large difference.

 

It might have bigger valves per cubic inch, but not every inch of those valves provides as much useful flow because of the shrouding.

Here's a picture borrowed from another thread showing how close the valves are to the cylinder wall in a 305, although these valves are 1.94/1.50:



Now imagine that on a 350, you've got an extra 0.132" of room on each valve.

 

TFS actually flowed their heads on the both a 3.766 and 4.000 bore and they ended up about the same. The only real difference was the peak exhaust flow which was 5% better on the 4".

So with good heads the 305 isn't bad for a 305. But it won't make 350 power without spinning a lot more RPMs, and the small block doesn't like RPMs. So you need upgraded rods, which means you should rebuild in which case you're better off with a 350.

 

For 250+rwhp I would go 350 or 383.

This is good for a stock 350, for a performance 305 or 350 it will take alot more changes then copy and paste the fueling maps.

I agree the 350 is a better plant. Just swapping EFI is not going to make the power.

 

I wasn't saying that a copy and paste of stock maps would be his best option. But a 350 with TBI and bone stock maps is a great place to start. There is a HUGE community dedicated to tuning these things though, and there's a wide variety of maps out there, that cover many changes that he might make to his engine as well. Odds are, however he decides to build a 350, (in the words of Verizon) "There's a map for that".

I agree that JUST swapping to EFI isn't going to make a HUGE amount of power (although it WILL help).

I'm saying that what he's looking for just isn't there. He wants to keep TBI, keep his 305, AND be able to hang with new Camaros (400, and 426 horsepower (depending on the transmission) BONE STOCK!). Even the V-6 models are pushing 300 horses, outta the box.

It's sure as hell not going to happen from a 305 (unless he just wants to hang with the V6), and it's gonna be a stretch from a 350, unless he does a serious bit of building on a 350, and adds MPFI.

The first step, is to get some displacement, and then build on it from there... That was my point.

 

Yes, its called DIY.

In fact he is being a little too vague concerning his goals. If his goal is 300rwhp it would be ridiculous to slap an aftermarket EFI port injection, even if it was on a 350.

 

http://www.popularhotrodding.com/eng...cks/index.html

 

ok iv been thinking. and iv decided to trash the 305 idea. thank you guys for that. another question would swapping a tpi 350 be complicated? oh and im not worried about my tranny. i had to replace that a few months ago and had my mechanic rebuild it. according to him its " bulletproof" he guarented me that i wont be able to break it within 5 years. the only reason i dont want to go carbed is iv been getting a million diffrent answers as to weather its legal or not where i live.

 

Sure, they put heads and a cam on a 305. Spend the same money on a 350 and see what happens.

There's nothing wrong with upgrading a 305, but if you have to rebuild it and replace the rotating assembly, and performance is your goal, then it's more cost-effective to build a 350. Likewise, if you have to replace the rotating assembly on a 350 and you want performance, you're better off building a 383.

 

1) It's illegal to equip a car that was originally EFI with a carb and 2) why on earth would you want to?

 

easier to tune to me. i dont like dealing with all these computers and stuff and i just like responseive ness of my truck which is a carb....i dont like having a truck that is faster than my camaro.

 

What sort of engine is in your truck? Are you saying that a carbed 305 is "faster" than your TBI 305?"

When you say "Faster" are you talking about holeshot?

Trucks almost ALWAYS have a good deal more torque than cars, which is what gets you off the line.

Put a cam in your car, and you can get more torque, if that's what you're looking for...

 

well i kno its like comparing apples to oragnes but my truck is a 77 f100 with a bored and stroked 400m it will be my camaro from a roll or a dig. what kind of cam would be good for my tbi 305. becasue torque really is all i care about.

 

I'll be honest, I usually defer to more knowledgable people than myself, when selecting a cam...

But it really depends on what you're looking for. Some cams would require extensive tuning, and others don't. It really depends on where you're willing to go with it. I usually just look at a few different brands, and then give the makers a call, they know their cams better than anybody else, usually, and IMHO are the best people to talk about their cams with. I get a few different opinions from a couple of mfg, and then search the web for people who've used the cam, and see what they think of it.

But honestly, I'd recommend just saving the money on the cam for the 305, and put the money toward your 350 build.

Start working on the 350 build now, get it ready to drop in, and then go for it. This way you can spend the money at your own pace, and you won't have to take your car off the road for an indefinite amount of time...

 

If your looking for power in a naturally aspirated application, just dump the 305 and build yourself a 350, because your only going to want more and more, and the 350 will be able to deliver. If boosting the engine is an option for you, then stick with the 305, as they are less prone to detonation, and will easily make the power that your looking for....

 

is the 305 capable of 300ft/lbs with out a ton of money?

 

To the rear whees? Yes, but symmetry will always be the key though....

 

 

what symetry? hp and ft/lbs im confused or are u talking about a posi trac rear end lol. im confused.

 

Come on you guys , symmetry is harmonizing the selected parts. You don't want to build a 305 the same way you would a 350. A 1.94" intake is more than enough to feed a 3.736" bore, and from there, its all about selecting the proper camshaft in relation w/the cylinder heads you will be running (I'm referring to static and dynamic compression levels). The velocity (speed) of the air is the key, so you do not want to over port the intake tract. This, provided that your fueling and tune is on the money....

 

I don't think that word means what you think it means, but I get your point.

EDIT: I think what you meant was synergy.

 

Of course it does, and I was not trying to embellish it from strictly a mechanical perspective, I was relating to more of a harmonious balance of matched parts. Much like the phrase "making sweet music together" when it comes to having sex, however music has nothing to do with having sex in the first place lol. It was being used as a depiction, Saabster....

Symmetry implies either a quantitative equality of parts (the perfect symmetry of pairs of matched columns) or a unified system of subordinate parts....

http://dictionary.reference.com/browse/symmetry

 

hey if you want to rebuild a 305 to make some decent power more power to ya! I like different. I am actually in the same boat I was given a 305 and now I am going to build it just to build it. I have a lot of extra parts so I wont be "buying" things but I have a buddy pushing 335HP out of a 305 he built using misc parts. I am looking for the similar result 300HP.

 

This is a great hydraulic roller camshaft for a 305, especially if you have an automatic transmission.
http://www.lingenfelter.com/mm5/merc...egory_Code=C30

 

I am talking from experience, the money you dump in will be just about the same if you were to get a 350 block and dump the money into that ... I rebuilt my engine in 2004, although I don't completely regret it, I could have purchased a 350 crate motor, or perhaps even picked an engine up from the wreck yard and built it to my satisfaction... right now I would have rather have gone with a 350 than overhaul my 305... I think you may regret it afterward, do it right the first time and if you are a bit hesitant because of a budget, then save up more, that was one of my prime concerns, going over budget... well I ended up spending about 3500 dollars included bolt-ons to increase power...

 

A proper rebuild is never cheap. Hence why I recommend a GMPP 350 shortblock. It's built by machines on an assembly line, thus it is cheap. Or you can buy a whole L31 Vortec crate engine for $2200. Or if you really want to stick with a 305 (you're crazy/different/silly/have emissions reasons) you can get a L30 305 Vortec crate engine for $2200 as well.

 

EMISSIONS!!~!!!!!!~! AHHHHHHHHHHH.... that was one of my reasons...

 

I love the comments "do it the right way" I mean the guy wants to do it let him do it, who says its the wrong or right way. I mean a 300+ hp 305 is pretty BA in my opinion and if he can do it cheap let him. My buddy did one with only $500 into the WHOLE thing, granted like me he had a lot of SBC parts lying around he wasnt using. The rest he bought used...

 

Well I'm curious what's wrong that's going to necessitate a rebuild.

 

nothing as of right now not major anyway. i can tell it jsut more slugish and its starting to smoke a tad on start up. so i figure its time to start planning on what to do.

 

I'm finding myself in the same position. The 5.0 has 130K on it so I'm thinking I should start planning ahead. Found a guy with a 350 taking up space in his garage, supposed to be rebuilt a couple of years ago and never run. Always kept indoors. Complete oil pan to carb. Going over to check out the numbers and condition tomorrow. Says he has all the receipts to show work done. What should I be looking for?

 

Smoke on startup is a sign that it just needs new valve stem seals.