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Chevy 305 & 307 Question

HDWRENCH

HDWRENCH

Member
Well, with skyrocketing gas prices, the 350 is out for me. I am now thinking of installing either a 305 or 307 small block in my T. While searching the net today, I found it somewhat difficult to find pistons for the 305 that were reasonably priced. And I couldn't find anything for the 307. Anybody know where I can get a decent set of cast pistons for either of these engines? I'd like to find something in the 8.5 to 9.0 compression ratio if possible.
 
Where ever you're looking for parts, they are doing you afavor by not listing 307 stuff. These engines were plagued with problems such as bad cams, core shifts, and others. The 305 is a much better choice all around.

Ron
 
Yeah, and the 305 is much easier to find . Not sure if I will get one from a junkyard or try and find a cheap beater and pull the motor and trans.
 
The question is, will a 305 get THAT much better gas milage than a 350? I think all things being equal, the 350 should be just as good, and maybe even better. The reason is, you could run a slightly higher gear ratio and the 350 torque will just loaf along, whereas the 305 will have to work a little harder.

I am getting 20 mpg + in my T with a 350. I run a 30 inch tall tire, and 3:00 gears. Going down the road at 60 my foot is just resting on the gas pedal, not really pushing down much at all. I can see my carb right in front of me, and it is just off idle at those speeds.

Plus, 350 stuff is available all over the place, cheap. This isn't to say the 305 isn't a great engine, it is, but if you haven't bought it yet, just something to consider.


Don
 
I agree with Don, 100%. The difference in fuel mileage is going to be pretty negligible, if it even exists.

If you're buying a second-hand 305, ask the seller how you will be compensated, should the heads be cracked (since they likely are).

The 307 was much maligned, but it was a small-bore block (3.875" bore) with large main bores, using the large journal 327 crankshaft (3.250" stroke). That actually was a fairly popular drag combination, using the early, small journal 327 crank in a 283 block. A lot of early C/ED's used that combination. The problem you would have would be finding a block that hadn't already been bored too far, after all these years.

I know there are a lot of people using 305's, but you are going to be better prepared figuring in the cost of a set of replacement heads, as nearly all the 305 heads we've ever seen have been cracked.
 
I don't know about the 307, but the difference in mileage between a 305 and a 350 would be little at best. Besides, driving habits would have to be considered.

Now, the 305 ain't as cool sounding rolling out of your mouth and they have been known for small exhaust and intake ports, but consider this.... just how fast are you trying to go? Are you goin to be racing it or displaying speed a lot? Then, I'd say, 350. Lot's of god, cheap tricks for bumping one up. If you want a nice, still kinda quick, easy to maintain AND replace (if you had too) engine, then the 305 could be what you want. I was going to go with a 350 out of a Vette, that a salvage guy was holding for me. He wanted $650 for it. He called and told me he had a couple 305's I might want to look at and they were only $400 each. Mine runs great. Moves my car plenty quick and is STOCK. Heck, I'm even running the stock Quadrajet carb! Why? Because it works. I haven't even rebuilt it yet!

So, you got some fuel for thought. Good luck. Oh, another thing.... if you get the 305, just SAY it's a 350. Chances are, no one will know the difference, anyway!:D What are they gooing to do, write down the casting numbers and check them out!? Please.:lol: There's a whole lot of guys TELLING how much fancy speed stuff they have in their engine and are running stock or near stock gear!;):D Can anyone tell if an engine has a certain brand/type pistons from the outside? I kinda doubt it.
 
maby think along the lines of a 700r4 with a lock up t/q and a 350 you will get good fuel milage with this combo
 
i have to agree with Don on this one .i experianced this when i built my last 305 for a chevy truck i had. it ended up way under powered and drank gas like an alchoholic drinks wine.lol i said right then i would never build another 305.i like you wanted better gas milage and ended up with a truck i was happy to get rid of.
 
v8danh said:
i have to agree with Don on this one .i experianced this when i built my last 305 for a chevy truck i had. it ended up way under powered and drank gas like an alchoholic drinks wine.lol i said right then i would never build another 305.i like you wanted better gas milage and ended up with a truck i was happy to get rid of.
Click to expand...

What carb and intake were you running?
 
For the 305, I was going to use an Edelbrock RPM Air Gap manifold with a 600 Holley. Maybe even try one of my 390's off of the TunnelRam. My 350 was in another car I had, and is built more for the 1/4 mile. I bought a complete 8" rear from Total with the chassis, and it has a 2.79:1 gear in it now. I was going to change that out for 3:55's.
 
To clarify my earlier comments, let me say again, I feel the 305 is a very very good engine. We had tons of them in some of the boats we sold when I was in the marine business, and they were close in performance to the 350. Only a couple of miles per hour difference.

I also agree that the quadrajet is a very overlooked carb. Those small primaries are great for gas milage and seem to fit the profile of a 305 fine (even a 350 for that matter)

The only point I was trying to make was that if he didn't already have the engine it might be easier to find a 350, and if it needs rebuilt you can get parts all over the place at super cheap prices. I hadn't built a small block Chevy since the 70's, mostly playing with Fords and Olds engines since then, but I was pleasantly surprised how inexpensively I could put a 350 Chevy together when I did my T.

I also agree with the overdrive transmission being a great addition. My daily driver has an AOD Ford tranny, and as a test one day I drove it in 3rd gear and the dash monitor showed 18 mpg. When I shifted into 4th it got 25 to 27. Big difference.

If gas prices keep going up I am gonna start looking for a moped. :eek:

Don
 
i was using the factory aluminum intake with a stock q jet 4 bbl.this engine was stock rebuild flat top pistons factory roller cam and center bolt heads.i thought it would run good but it didn't .it ran smooth but the 350 would have been better more power and i am sure it couldn't have used more gas than the 305.as a matter of fact the next engine i buil.was for a drag car 86 fire bird it was a 350 flat top 40 over stock 882 heads and a 268 h cam weiand intake and a 750 edelbrock carb and it ran in the high 12's and got better gas milage on the street than the 305 did.lol that is the engine i am using in my t bucket lol.Dan
 
I'm running a 350 in my T as well. I don't know what kind of mileage I'm getting though, never thought to check. It seems to pretty good though. However the next engine will be a 1962 283. I got a good deal on it, free. :D
 
I've used 3 305's so far,late '70's and early '80's models and no problems so far.

Bruce...I like the way you think. I stumbled onto a deal on 4 SBC a while back. An old friend was moving and wanted to know if I would be interested in a couple of engines he wanted to get rid of. Short end of story is, I now have 2 283's and 2 327's. Gave him $100 and he helped haul them home.

Quick tip...If you're rebuilding an engine and need some machine work done, check with the vocational schools in your area. For $35 and parts I can get all the machining done.

Ron
 
Youngster said:
I've used 3 305's so far,late '70's and early '80's models and no problems so far.

Bruce...I like the way you think. I stumbled onto a deal on 4 SBC a while back. An old friend was moving and wanted to know if I would be interested in a couple of engines he wanted to get rid of. Short end of story is, I now have 2 283's and 2 327's. Gave him $100 and he helped haul them home.

Quick tip...If you're rebuilding an engine and need some machine work done, check with the vocational schools in your area. For $35 and parts I can get all the machining done.

Ron
Click to expand...

Thanks Ron I'll have to check on the Voc. schools. I'm in the part collecting stage for the engine. But with 2.02 camel humps and dual quads the mileage won't be very good, but it will look cool. :cool:
 
VegasBruce said:
Thanks Ron I'll have to check on the Voc. schools. I'm in the part collecting stage for the engine. But with 2.02 camel humps and dual quads the mileage won't be very good, but it will look cool. :cool:
Click to expand...

Cool will ALWAYS cancel out mileage. I dare say that while the current price of gas is outrageous, it will just make folks plan things more. Something we should have been doing all along. When I'm at work, I plan out any stops for stuff I may need to pick up on the way home. Think about all the unneccessary, back and forth trips you take during the week or week end. That crap adds up. I'm truly lucky that a lot of the places I frequent are close to my home. Including work, which is only 7 miles away, but even then, I think before I hop in my car and take off.

Hot rodding is a hobby/sport/leisure activity. It's good for the mind and body to get away from the day to day with a great hobby. Now, we just have to plan the breaks a little better, that's all.

Be concerned, but don't panic. Don't ever let them see you sweat.:mad: GRRR! EYE OF THE TIGER BABY! BRING IT ON OIL BARONS!:mad::lol:
 
Well, my '27 used a built 302 Ford with two fours and 3:70 rear gears, and got about 25 on the highway. That was with straight carb linkage too, not progressive. People would say all the time, "bet that drinks the gas!" but it didn't for some unknown reason. Plugs were always whitish.

Don
 
donsrods said:
Well, my '27 used a built 302 Ford with two fours and 3:70 rear gears, and got about 25 on the highway. That was with straight carb linkage too, not progressive. People would say all the time, "bet that drinks the gas!" but it didn't for some unknown reason. Plugs were always whitish.

Don
Click to expand...

Vehicle weight, or lack of, most likely. That is a VERY important part of the equation. That and proper tuning, of course.
 
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