My 305 in my 86 trans am blew something in the engine and I got talking to someone while on break at work about where i could get a 350 rather cheap and he said to just rebuild your 305 while boring it out and adding larger pistons. He also said I should put a supercharger on it. I got to thinking about what he said and i started looking around on the internet about what you could get out of a 305 and I found some interesting things. I was mainly just wanting to know is what your suggestions would be on doing this. I currently have tpi but plan on switching to tbi in the end.

you could stroke the 305, but why? its not worth the money.
If you come across a 350 block, which is easy enough to do, pick it up and build it.

Why on earth would you go from TPI to TBI? you must be slightly more than mildly nuts or a bit confused lol. Though TPI has its faults, it beats out TBI 9 days a week.

dont mess with the 305, it isnt worth it. If you are gonna ditch the TPI, go LT-1 or carb. At least something that will net a gain.

Cost to bore a 305 = $100
Cost of a 350 block = $100

Why would you go with a 305?

You can buy basic 350 rebuild kits for $200-300, and 305s are more expencive

Depends on what you think expensive is. My father and I just finished up rebuilding my 305. We had the heads professionally cleaned and checked out at a local machine shop which cost 300 bucks. After replaceing all the electonic sensors and gaskets and rebuilding it. We have no more then another 200 or so into it. Maybe 300 is you wanna push it, but thats what it'll cost to rebuild a 350. Maybe we just have great prices up here in Massachusetts, but rebuilding my 305 was cheaper then buying and rebuilding a 350. Plus, I don't have an engine stand or anything to yank one engine and put in another. So it was easier. Now I have a decent engine to work with, that'll get me down to college and back without worry. For me, it was best to rebuild the 305. Not necessarily best for anyone else, but price is no different then a 350.

what's the no.1 dumbest thing you can do?


Rebuild a 305 when 350's comes a dime a dozen.

get a 350 an put a supercharger on that.

So I guess I'm dumb. Many people are very closed minded here. And tell me I'm stupid all you want, but I enjoy being different. As to the original poster, you have your options, find a 350 to rebuild, or just dig into you 305. Difference in price will be the price to buy the 350 block, nothing else will be groslly different. Choose whats best for you.

No one is calling you dumb, its just that you said yourself that you spent the same amount to build the 305 as a 350. So you spent the same amount of money, just to go slower. From a performance standpoint that was stupid. But that doesnt mean that you are stupid. I dont consider myself stupid, but I have done some stupid things (ex wife, etc.).

Closed minded indeed, last time I checked I had a 305. With the same amount spent rebuilding/building up a 305 you could put that much more out in a 350, it's common sense, if someone wants to build up a 327 stroker then more power to them. 4 bolt 350's aren't hard to find and are cheap if you look in the right places.

This is my opinion, plain and simple.

327 stroker = 350ci or 383 depending on how much you stroke.

No one is stuipid for doing a 305, are there better options, yeah. You have to do what you have to do with the money you have. We just tend to lean on the performance side.

Edit: unless you meant stroke the 305 to 327

Lets cool it guys. There are a 1000 posts on this site about 305 vs 350 and there's no reason to continue this one. There is no wrong or right, just logic here. Only reason to build a 305 is because you have one, its free, or you want to be different. Being slow for the sake of difference seems to draw some following...still, there are a number of fast 305s around here...Willie, Preston...etc

My question is why on earth would you switch from TPI to TBI?

and 86TWINS, what you are doing isn't considered rebuilding an engine by most people's standards. All you did was a bearing job.

cubic inch displacemant is always your friend...

exactly what I meant.

I understand that I will be slower then a 350, but for now it works. I also don't wanna build up a 350 to yank it for my other plan. But I understand what you are all saying. I did a top end rebuild, not a full rebuild, my bad on wording. Oh well, if I had more money, the things I'd do. :-)

If you want a sleeper, a 305 ain't it. If it goes slow, it's not a sleeper. If it goes fast, nobody will beleive it's only a 305. All small blocks look the same from the outside, so only YOU will know it's actual displacement.

You want a sleeper? Start with a 400 small block. Now THAT'S a sleeper. No blower required. Sleepers don't use power adders unless they're well hidden.

mines a sleeper right now...

all i have to do is point at the 400 and say, its a 305?

oh, and thats not cam lope... its misfiring, i think i burned a plugwire or somthing... yeeea..

Huh, no desire to be slow for the sake of difference, I don’t have one sitting around (the vehicle that I want to build it for has a 350 in it now), but I do expect to find a decent 305 by the time I’m ready for it for free (plenty of people just throw them out or just want them gone).

I guess I’m just a little excentric? Anyone reasonably close to me have a 305 that they want to be rid of?

that’s a little harder to justify, but I could come up with a reason… get the bores bored to 54mm (about the biggest that I’ve ever managed to cut them to successfully), assorted spacers… and you have something that will flow with all but the biggest TPI or “port” throttle bodies out there, bolt to any manifold you feel is best for your engine/car, and cost much less then getting the same airflow out of a TPI. That and the whole thing is brutally simple to work on, more so then a carb or TPI. The only real advantage the TPI has on it is that it’s easier to put more injector in it then the TBI.

heh, well you still meet my requirements with the free aspect lol

...and aren't you really building the 305 because its displacement is better suited to the planned turbo for it??

Since when is having a 305 different? Where are you from in Mass?? Ever go to my site or Nefbody.org? Check em out!!!

Why? I still have to go and get one, where I could just build up the 350 that’s in it or even the LT1 that is sitting in the garage.

That makes no sense. If that was the case (If I had a specific turbo in mind an in my hands), why wouldn’t I just sell it and use the money to buy something bigger? That would be a lot easier and cheaper then finding and rebuilding a 305.

XjoshX I live in Southern Mass, down in Norton. Im' minutes from Great Woods, if you know where that is. I have been there, but there's not alot of activity, so I visit from time to time and read up on stuff. And having a 305 isn't really all that different, it's just different from a performance stand point.

I suppose you have pointed out the flaws in my thinking, Mark...but why a 305 then and not a 350 that you already have?

The only deficiencies that the 305 really has are airflow and displacement.

Displacement first- look at the 5.0 fords, is that holding them back? How about the mod motor fords? Enough there… displacement is great for power, but for a street car, with today’s gas prices… not necessary.

Air flow. I’ve gotten over 230cfm at .050” with a 1.94” intake out of a set of vortec heads in a 3.75” bore… Unless you’re building an all out race car that’s a lot, more then enough to feed a 305 to 7500rpm (way out of street car range). Let’s say you don’t want to sit and tinker with a grinder, don’t want to pay someone and can’t justify the cost of some AFR’s…. You can cover up many airflow deficiencies with boost.

Past that the smaller bore has some nice advantages with detonation control, timing… When you start talking about boost at torque peaks, pump gas… that adds up to a big advantage. Lastly, ask some of those 305 TBI guys what kind of mpg they’re getting, then find me someone with a 350 coming even close… So if you could realistically build 1000hp with a boosted 305 or 1100hp with a 350, but you’ll never use more then 500 from either on your street/strip car, or 400 in your truck, then why not take advantage of some of the 305’s advantages?

What's gonna happen when there is nothing left in the boneyard but 305 blocks? Somebody's gotta use'm.

thats why theres aftermarket castings.

and by the time theres only 305 blocks, 99% of us will have moved onto LS1 or better motors... hopefully.

That will never happen, most jy's crush watever sits around for more then a few weeks

Displacement isn't what is holding the 305 back. The problem with it is that the bore is smaller than the original 265 Chevy, yet it has the same stroke as a 350. They typically get about the same mileage as a 350, while producing less power. There are plenty of reasons to use a 305, and I'm not trying to discourage anyone from doing what they want, but its not anywhere close to being in the same league with a 5.0 Ford. Thats why the thirdgens weren't the first (heck, even the second) choice of performance enthusiasts when they were new...the Ford guys could get great results with boltons, while the third gen guys had to do an engine swap to keep up.

ford 5.0L (mustangs) would lose to a 350 tpi(iroc-z,trans am).

Ford`s 4.6L mod motors would lose to a LT1 or LS1.alright maybe 4.6 4v motor might "hang"or beat a LT1.

bigger motor=go faster

i went from a 305 to a 350(+.060) ,so now i go faster.If i were to do a swap again id go big block (454 or bigger).



displacement has little to do with gas mileage.the two things that effect gas mileage the most is the vehicles aerodynamics and weight.IF the corvette and e150 van weighed the same which one would get better gas mileage???If corvette 1 weighed 2500 pounds and corvette 2 weighed 3600 pounds which one would get better gas mileage???

Lets say it takes 40 hp to go 60 mph in a camaro.u install a 2.5L 4 banger,you`ll notice your right foot on the gas pedal is close to the floor to achieve 60 mph.now u install a 502 v8 ,your right foot moves the pedal maybe an inch to go 60 mph.It`s the remaining inches to the floor that kill your gas mileage.
lead foot=bad gas mileage

I wouldnt exactly say that. The 302 is a lot more powerful than the Cubic Inch comparable 305.

Oh, this is just plain dumb. For most years the HO or TPI 305 was rated similarly and actually made more power then the same year’s 302. The reason that 3rd gens weren’t the first [cheap] performance choice over the mustang was that Typically, an L69, LB9 or L98 f-body was priced at 1.5-almost 2x what a 5.0 was (especially a stripper LX, and this varied a lot per year), and was typically 2-400lbs heavier (again, especially when compared to a stripper LX, but even when compared to a GT which are commonly in the 3200# range, where a stripper formula or camaro is typically in the 3400# range).

As far as gas mileage goes, yea, it’s basically how much energy does it take to overcome air and road drag + friction, but the bore/chamber geometry of a 305 is actually more efficient at part throttle (where ultimate breathing capacity isn’t an issue) as compared to a 350 (or even a ford 302). If you don’t believe it go poke around the TBI board and see what kind of gas mileage some of them are getting (almost all 305’s, that’s the only real reason why I suggest that you go there). You won’t see anything even close from an L98 or even a mustang (which was more likely to have a 5 speed, much less weight and narrower tires, all things that should help mileage). If you want another perfect example of this look at the spark advance map from a 305 car vs a 350 chip.

If the 5.0 you are talking about is a "heavy" GT hatchback or convertible, and has an AOD, you are correct. A 5.0 LX coupe or hatch with a 5 speed would take anything in its class, short of a turbo Buick. Their HP numbers stock may not have been as high as a comparable F-body, but they had three large advantages...low cost (of the car and the performance parts), light weight, and an engine that responded well to modifications. Most 5.0s were modified from day one, so their stock performance wasn't too relevant anyway.