The Stovebolt Site Forums The Shop Area The HiPo Shop 305 or 350

I have a 305 that came with the new 56 project. It is supposed to be a good engine, but has a flat spot on the cam that is causing a miss. Also was smoking a bit. According to the Previous owner, this engine has 70K since new out of an 84 C-10. PO gave me a set of good heads. I'm planning on building the truck as my everyday driver. I'm an old fart now -- truck and I are the same age, and am not looking for a hotrod. I have a buddy that says I can have a 350 for a core if I want. I checked with an engine rebuilder in Tyler and can get either a 305 or a 350 longblock with warranty for about $600. I'm leaning towards going the longblock route. By the time I get ahold of a cam, gasket set, bearings, rings, etc. and then send the heads out, I'll probably be into the 305 I have for that much or more. Plus I would not have any warranty. So my questions are, should I first go with the longblock already set up to go? Then, should I stick with the 305, or upgrade to the 350? Opinions? Reasons?

350, no question about it. If you are bucks down toss a cam in the 305 & it'll go a few more miles. Brian

I,d go for the 350. The 305,s are sluggish. Take a hard look at the 350 core. If it doesn,t need boreing or crank turned & you can do a minor o-haul yourself you can buy an o-haul kit for about $250 & have the heads done at a machine shop. Other then that I would go for a new Goodwrench engine like has been discussed on some other posts.

My vote: 350. It will outperform the 305 by quite a bit, and if they cost the same, there's no reason not to. You might get a little better fuel efficiency out of the 305, but at a disproportionate loss of power.

350- just the commonness of that engine will save you so much trouble in the future...Parts can be had so easily, information is readily available..etc...

buy the long block install and enjoy...doc

I'd go 350. 305's were dogs. I have heard that 305's don't really save gas. I don't remember what the reasoning was, but they weren't supposed to run as efficiently as the 350. I had a 307 that weighed in on that being correct. 307 got me about 14mpg and the replacement 327 got around 17 with the same components bolted back up...anyway, 350, more power and gas consumption will be about the same if not better in my opinion.

Do you plan to have a/c on your ride? If you do, and I see you are from Shreveport, don't even consider a 350. A 56 radiator will cool a 350 if in good shape and no a/c but not with it. Since you've said performance is not a factor the 305 will run 30 degrees cooler and allow a/c with no cooling system upgrade expenses. The 305 will cruise the speed limit effortlessly, get a tad better mileage, and idle all day in 100 degree weather with the a/c on. It will take 3 or 4 more seconds to get from zero to sixty in case you have something very critical to do with those 3 or 4 seconds.

Sorry coilover I have got to dissagree if the cooling system isn't up to cooling a mild 350 it isn't going to cool a 305. The differance between the two is the bore. I would go with the 350. Sounds to me like you are looking at a rebuild either way. Don't get me wrong the 305 is a good torquie little motor better than the shorter stroke 307. Building any of the SB Chevys in a like mannor will cost about the same. IMO and many others for that mater there is no replacement for displacement.

No Replacement for displacement is the proper rule of thumb, and I also see a very negligable cooling difference between the two.

Guys, I have got to agree to disagree. Building street rods is what I do for a living and being in the Dallas area I have received an education in temp control whether intended or not. We have found that in certain cars, like 39 & 40 Fords for example, where air flow is restricted it takes effort and expense to cool a 350 while a 305 will do OK. We have pulled 350's (one of my all time favorite engines) and put a 305 in the same exact circumstance and cured the heating problem. This is not a recomendation for anyone that's the least bit performance conscience. Since both pistons in the two engines travel the same distance, 3.48", the only friction difference is the larger area of the 350 bore which is probably neglible. The big difference I think is the cylinder wall where the thicker 305 carries more heat out the exhaust while the thinner 350 transfers more into the water jacket. Our latest go around was with a 39 tudor that had a stock bore 350, desert cooler radiator, Brassworks extra flow waterpump, and several fan setups, all with correct schrouding and grill opening to radiator baffles in place. It did fine in town but would slowly creep up at highway speeds. After being pulled from the 39 this 350 was put into a 71 Custom 10 pickup and it ran right on the T-stat setting and the 305 did the same in the 39. This is not just theory, I can give names and telephone numbers of customers that have gone through this experience.

I been turning wrenches for better than 20 yrs, & I have never seen a 305 run 30* cooler than a 350. I am sure they run a little cooler as there is more metal around the cylinders, but in the 39 Tudor case, if the engine ran fine in another vehicle the problem is radiator sizing. Yes, you need more radiator surface area for more cubes. Just because the radiator is thicker(more rows) doesn't mean it will cool as well as a larger surface area radiator. Brian

I vote for the 305 .If the cam has a flat spot causing the miss, you need to check it out first.Identify which cylinder,check the valve train,replace the cam,if you have to. Don't even pull the heads unless something big shows up. If it only has 70k miles,it should still be like new.Maybe your miss is ignition. I was faced with the same problem as you for my project.After checking costs of rebuilders, a G.M. 290 horse crate motor was the best buy on a fresh motor.Has about 3 yrs. warrenty insead of about 6 months from most rebuilders around here.A long block for $600 sounds to cheap to have much machining put into it.Maybe a honing, cheap rings, and bearings, a cheap cam and lifters, but nice rattlecan paint on the outside.The G.M. crate mtor is closer to $2000.00. That was more than I wanted to spend at this time.I ended up buying a Chev Impala with a 305 with air that ran like a top for $225.00.Drove it around the farm for a couple of weeks to check it out, then pulled both motor and trans, put into my project.Has a small block chevy.305---350 I don't care.If it worked in an Impala with air, it should have enough power to let me cruise around in a 39 Chevy.

TooMany:

Thanks for the post! Great info. Still thinkin'.

Appreciate all the comments, guys!

I'll throw my 2 cents in too. Out of all the small blocks, the 350 tends to be the cheapest by a few dollars because more kits are sold for them. I would stay away from a parts store remanufactured long block. I have seen these engines bored as much as .080 over and they will grind down valve stems and install liners in the guides in order to not use new valves, crankshafts are built up and reground too. The rebuilders will do anything they can to use the cores that are turned in to them. The new engines from GM are an good option, but if you have a good local machine shop and the core 350 is ok this would be a good route to take. With the right radiator the 350 should run fine. In my experence (10 yrs automotive machinist) I haven't seen 305s with thick cylnder walls, they use a diffrent core in the water jacket when the block is cast, the nomal thickness is roughly the same as a 350. The diffrence in temp mentioned above is probally due to the 350 making more power. Power = Heat. Just my 2 cents.

Sean

I had one more thought, once an engine has had a cam lobe failure all of the metal from the lobe has rained down on crank and rods mixing with the oil turning into a laping fluid. You can't count on the filer catching it because it only filters about 10% of the oil. Internal engine wear is accelerated. When using a flat tappet cam you should run 15/40 oil all the time and use an additave such as GM's EOS for cam break in. The other grades of oil have had a lot of the zinc and phospherous removed due to emmissions requirements for newer cars. Sorry to be so long winded but this stuff is important to know for all old vehicle fans because the oils just don't have what it takes to protect our older engines.

I put a 305 in my '49. It wasn't half the engine the old 283 was. Drove it about a month and then put another 283 back in.

Go with the 350 and have peace of mind with the warranty. Make sure your temp guage works. If and only if it overheats, add a core to your radiator. 305's are okay with a manual transmission behind them but the 350 will do a better job.

YA CANT BEAT A GOOD OL 350 , they run forever if maintained the right way , an can even stand a little xtra heat .....i have had so many over the yrs ....an actually i cant ***** bought any of em ...they are what they are ...the Chevy 350 small block IMO is the best motor ever made for longevity and performance an you can tinker to your hearts content without facin a Divorce over cost an parts , ya can find along side of the road in folks back yards to get ya home ...LOL

Tore into the 305 this morning. Cylinders mic out real good. Very minimal wear. Crank likewise. I'm thinking that since I plan to do this truck as a running driving work in progress, I may just go ahead with the 305, get the 350 core from my buddy and build it up. Down the road I'll switch the 305 for the 350. From what I can see the bottom end of the 305 is excellent. New cam and lifters, then I'll check the heads, maybe put new valve seals on, throw it together and get everything running. What ya think?

I'm with Pablos on this one... pop in a 283 or 327... they are much cooler than a dimadozen 305 or 350.

Personally I like the 350, it gives more power with about the same gas mileage as the 305. If it was me though I would get it running with the 305 and later build the 350 as finances or time permits.

Good plan if the 305 is in good shape use it. Do a nice mild build on your 350 as time and money permit. Have your cake and eat it too. I don't know where that saying came from it's kinda dumb huh?

Good move Clint, sounds like you have a handle on the situation, ya gotta stick with what your wallet says, though a lot of us here will help you spend your money. I am going with a old reliable 250-6 now, but when I get some more dough I want to find out if a 454 will fit in my '63 LOL

Truckstein,
I think the 250 is a very good choice. Had one in my last '49 with a TH350 and Camaro rear end. Not real great on take off, but I could cruise the freeway at 70 with no problem.