The Stovebolt Site Forums The Shop Area Engine Shop Straight 6 Guys are gonna hate me, but...

Sorry guys, I have a V8 question: I've heard from several sources, one of whom is an automechanic, that the chevy 305/307 V8s were junk from day one. Anybody have any knowledge or opinion on that? Since some yahoo has dropped a rebuilt 305 V8 in my C60, I'd like to know if I can expect it to blow up any time soon, especially under the stress of yankin a 7 ton school bus around.

The 305 and the 307's are two different engines. The 307 I have heard a lot of bad press on but have no real experience with it. The 305 is a smog engine from the 70's and 80's. It's a low compression, low horsepower engine that was usually run in light duty trucks and cars. Niether one is a high torque engine that you need for your big rig. A big block is probably the easiest upgrade since you are aready running a V-8, but a large cube inline will also install with some easy modifications and pull a bus around pretty well.
You'll hear a lot of different opinions but run the 305 while you find your replacement,
Good luck,
Scott

Personally I think most small block Chevrolets are pretty poor. About the only exception would be the 4 bolt main 350. 4 bolt mains aren't that big of a deal, but the block is made of better material. It will have 010 stamped on the side, and they will last fairly well compared to the softer blocks that are more common. I agree that if you could find a big block you would be better off. They are a pretty good engine, much better than the small block.

howdy! the main problems with the 305 are the low nickle content of the block, (lousy casting), and the famous small block chevy soft camshaft. thousands of chevy cams had to be replaced.

they saved a few bucks, but it's hurt them in the long run!

bring yer 4 bolt 350 on! gotta 69 "z" 302 in the garage! well, for now anyway. maybe got it sold this week.

Yeah, big block was my thought. I hate to ditch a brand new rebuild, 305 or not, but maybe I'll find a home for it on ebay. I'm thinking a junkyard 366 or 427 tall block from a slighly newer truck since it will probably mount the same way or adapt easily, and will work with the Spicer 5-speed behind it. Straight sixes are fun, but I want a little bit of giddy-up, and a V8 sound.

In defense of the 307...

I had a 68 chevelle with a 307 and it had 280,000 miles on it and ran great! Sold that car to my neighbor 3 years ago and he just sold it to some kid. The 307 is a good engine for daily driving. Don't hot rod it and don't expect high performance. Leave it stock and it will give you many miles of service.

I also had a 69 c-10 that had a 307 and it went 235,000 miles and I pulled it because she was burning oil, but still ran great. I have plans to rebuild it and put it in my current daily driver 69 c-10(250) when the 250 goes someday about 15-20 years from now. If you plan to v-8 a truck because you're going to be pulling trailers and such I would recommend a big block (396-454). It always puzzles me how some guys say they are going to pull their 6 in favor of a 350 "because they want to tow" or "want more horsepower", in my opinion why choose a 350 for that when you can have a big block?
Just my $0.02
Dano

Just my opinion, but 305s aren't the world's greatest motor by a long shot. They're not the worst, either. But they're sure not suited for making a lotta power. Small bore, limited combustion chamber and valve size, etc., etc.

If you've got a big ol truck that you want to move around, I'd think a big block (454 is probably the most common) would be the best way to go. It has just what you need: torque.

But what do I know? I'm just the bass player.

Sawby, I wouldn't worry about the 305 blowing up, I don't think they have enough power to do that! As far as 307's go, I had a '68 307 that I bored .125" and put large journal 327 rods and pistons, and a 327, 325horse cam in and dropped it in an '81 Monte Carlo. Edelbrock carb. and intake, NICE motor! Ran great. I'd go big block, stick 4 chrome pipes out of each wheelwell, and flame it! Who says school ain't cool? If Xram reads this I think he'll agree He might tell ya to put a Duramax diesel in it Sorry "53Moneypit" for the "underage reply" to an "underage question". :p

Have you considered a 401 jimmy V-6? Now that's a bus motor!

Boo

It's amazing how Pakrat knows what I'm thinking! Hard to beat 600 lb-ft of low-end grunt.

thanks for the anecdotes and info. I think this 305 has got to, but I'll run it until I can find a suitable big block. I've got my heart set on a 366. I like the big GMC V6s but I think they're probably too hard to find in the suburbs of a metropolitan area - I dont have too many fields from whence to poach old iron:). My guess is that the 366 would be the historically correct for a big block in this vehicle, and its meant for truck applications so I would bet it's pretty tough. Pakrat you're right about 53moneypit's post, that's what got me self-conscious about my somewhat late, V8 powered monstrosity in this world of elegant six cylinder vehicles.

The 305's and 307's are both downsized versions of bigger engines. The 307 had a 283 bore, with a 327 stroke, trying to gain the advantage of the long stroke crankshaft without the gas-hogging cubic inches of the 327. fast-forward a few years, and match up a 265 bore with a 350 stroke, and call it a 305! Same concept, long-stroke torque, and fewer cubes to feed. As long as the gear ratio is right, the 305 will pull a lot of load, just don't expect it to happen quickly. Make sure the rebuild included a new camshaft, and also be sure the EGR valve has the correct volume restrictor bushing in the stem. The reason for 305 camshafts failing was an overheating condition around the #4 cylinder pushrods caused by too much heat through the EGR passage. It caused oil to coke, and build up around the pushrods. The resulting load on the cam lobes caused flattening of the lobe, usually on the #4 exhaust valve. If it wasn't done already, installing flattop pistons in the 305 will make it a pretty respectable load-pulling engine, along with a Comp Cams RV camshaft.
Jerry

darn, that's like the best post i've ever seen. you must have a degree in 305s, i've heard of the soft cam but I never heard a detailed reason for it. honestly I dont even know if this thing has an egr setup. really, i'm not 100% sure that it's a 305, the old codger who sold it to me might be remembering wrong. he swears to it though, so I until I find a casting number I can only go on his word

I agree! I've had a 305 and a 307 in cars in the past and never new what the difference was.

Good info, Hotrod. I plan on putting a 305 in my '64. I don't plan on hauling anything, just want something that has decent power. I plan on a mild cam to give it some sound, some flattops, and a decent intake & carb. I don't want a hotrod, I just want something with enough power to get out of its own way.

Besides, the 305 is free.

The SBC isn't bad, when used properly. I'm building a 4-bolt main 400 for my '77 Corvette. My family has never had a major engine problem with anything from the SBC/4.3 V6 engine family.

IMO, the worst engine in GM (and maybe all manufacturers) history is the early-'80s 2.8 V6. What a POS... :mad:

I'm gonna have to disagree with 2.8 V6 assessment...the early 80s ones might have been troublesome, but my parents had a buick century wagon with that motor from 87 and it ran reliably for 125,000 miles, even on my dad's biannual oil-change schedule. The early ones were carburated, maybe the ironed out the kinks by the time the fuel-injected ones rolled out. Until I read this post I honestly thought SBCs were considered great engines, with the exception of the 305. you always hear that old "you can't kill a 350" yarn, and my dad's 170k mile Roadmaster 4-bolt 350 doesnt burn a drop of oil.

Hey Sawby4President,
If you are thinking of a 366 I'd say go for it. I've ran many grain trucks with them and they'll really go to beat the band if you've got a good set of gears.
Does this bus have a two speed rear end?? Then you'd have it made!
If you've got your heart set on a 366 I'd use it. It's all about having something you enjoy.

Thanks, guys!
I just happened to be attending some trade school instructors' seminars sponsored by General Motors when the flat-cam problems started happening on 305's, and they were the subject of some pretty detailed discussions between some of us instructors, and some GM field trainers. Interestingly enough, GM came out with a policy about that time that denied warranty coverage to any engine that had been run on 10W-40 oil. When I started questioning the policy, they explained that certain polymers in 10-40 oil were causing the oil to break down in high-heat conditions. When I asked if any specific brands of oil were involved, I couldn't get a straight answer. In one-on-one conversations with a few field reps, the letters Q and S came up pretty frequently! GM couldn't specify a specific brand, but they could prohibit all brands of 10W-40. Draw your own conclusions!

In a lot of cases of cam wear, I've found rock-hard deposits of burned oil built up around the EGR passage area of the passenger's side cylinder head, to the point the pushrods were locked up by the coked oil. I believe an excessive volume of exhaust gas flowing through the EGR valve was the cause of the problem! Since EGR also cools the combustion temperature and fights detonation, don't disable it entirely, but restrict the flow a little with the correct restrictor bushing in a replacement valve assembly.
Jerry

Hi can anyone tell from what year, to what year they built the 366 engine in chevy and GMC type 5 ton trucks.?
I do not know much about them and I am having a hard time getting information on them since they were not used in one ton trucks.

Did they ever make the blocks for a 366 engine cheap and low quality in Mexico, like they did with the 350 four bolt main engine starting in 1978.?

There an odd engine I never heard much about them untill now, I thought I would ask about them since some people on this clip have been talking about wanting to use them, thanks.

I don't know the answer. But unless you are going to work your truck hard I don't think there is much reason to look for a truck version big block.

Why look for an unusual version of a motor most people would never be able to tell from the common verions? 454's are common and probably cheaper to work on that any other big block.

I don't see an advantage in the 366.

http://www.nastyz28.com/bbcmenu.html

that link is for general Big Block casting numbers and manufacturing dates, and the 366s are spread out throughout it, but it's got some okay info. Seems like they started making the 366 in the mid to late 60s for two-ton truck applications, but I think the end dates on this page are wrong. There were different castings for this motor, but the website suggests the latest production year for any was 1985. I think the engine made into the early 90s and may have even seen fuel injection. Some of the Kodiak and Topkick style trucks I would swear ran that motor if you didnt opt for the dog CAT 3116.

I think I see the advantage of putting a 366 in a one ton - it's nice to have a tough motor that's maybe even overbuilt for the application its in, and the 366 has been around a while, so it may feel more period-correct in older vehicles than say a 454. Chevyvan, They also made a rare 427 ci variant of that same truck "tall block" big block that the 366 is based on. That's actually what I'd like to put in my bus but I doubt I'll find one.

I read on some chevy off-road forums that guys are putting 366s in K5s and pick-ups for a tough, torque-y rock crawler. The 366 apparently wasnt built for speed, but it's known to be tough.

I'm fascinated with this motor too obviously, if anyone finds horsepower and torque figures definitely post them. I read somewhere that the gross ratings were 235 hp and 350 on the torque, which shakes out to maybe 180-190 net horsepower and upper 200s to maybe 300 torque. She's a mule for sure.

I forgot, the 366 is known as a "tall-block" because the deck of the block is something like 4/10s of an inch taller than the standard BBC, and someone correct me if I'm wrong, but i believe it has 4-ring pistons (is that crazy?), and definitely 4-bolt mains. I'll try to dig up the links of the sites I got this info from.

One more thing, hotrod lincoln, what this all about with the 10W-40? I use it in all my cars to keep the high mileage bearings nice and cushioned, but Chevy is saying it was partially to blame for the cam problems? I guess the excessive heat from the EGR is what aggravated this trait in the oil, but that still doesnt give me much confidence.

Anyone can correct me if I'm wrong but actually I think they still put out some version of the 366.
Some newer 3/4ton Chevys come with 6.0Liter engines. That converts to a 366.

You take your liters (6.0) multiply by 61.03 and that will get you close to the actual Cubic Inch Displacement.
Otherwise if you know the Cubic Inches take that number divide by 61.03 and you'll get the Liters.
Most calculations aren't exact but it'll get you really close.

Thanks for the information Sawby4president and others.

I would much prefer to have a 366 over a 350 engine, the 350s are everywhere and a dime a dozen compared to the 366, I did not know they made a 427 version of the 366.
I would think the head and manifolds for the bigblock 366 are not the same as for the smallblock V8s aplication, so the question is are the intake manifolds the same for both big and small block GM meaning the 350 carb will fit on the 366 and 427s intake manifolds.?

I would also still like to find out if they made a cheap low nickel version for the 366 blocks in Mexico,? if anyone knows when they started doing that was it 1978 like the 350 engines.?
From my unverifyed understanding so far from talking to many folks is that the 350 engines were substantially cheapened up and made in Mexico starting in 1978, around the time that the Old Flint MI car and truck plants started to close down for good.

I think you're right about the displacement of the new 6.0 V8 in Ci, but it's coincidental - that engine is based on the latest generation of small blocks I believe (4.8, 5.3, 6.0). The big block is the 8.1, which I have dreams about.

When I first learned about the truck 366 I thought it was a smallblock, assuming that the cut-off for big/small block is somewhere around 400 cubic inches, but apparently there's no rhyme or reason to the big block/small block distinction (Ford's industrial truck big block was only a 330)

whoops, forgot about chevyvans question.

It seems unlikely that they would cheapen the block castings on an industrial motor, since they work so hard, but I dont have any information on that. As you probably saw from the link, there were many different casting #s for the 366, so it's possible that quality varies. I was wrong about the last year figure, the website lists one casting made until 1988. I stand by my conviction that later fuel injected versions were made into the 90s though.

Saw, if you're using a 10-40 oil for cushioning bearings, better rethink that idea. Any multi-weight oil stays the consistency of its minimum weight rating all the time. For instance, a 10W40 is the physical viscosity of a 10 weight regardless of temperature, it just lubricates like a 40 weight when it gets hot. To get any cushioning advantage, the lower rating would have to be increased, like a 20W50, for instance. That one stays the thickness of 20 weight all the time, but lubes like a 50 weight at its maximum temperature rating. Ditto for 85W140 gear lube. BTW, I assume you know the "W" stands for "winter", not "weight" like some people think. The lower viscosity rating is measured with the oil at zero degrees Farinheit, I believe.

OK, I'll climb off the soapbox for a while! I believe the 10W40 restriction from GM had more to do with overheated engine components than it did with any actual failure of the oil, but for a few years there in the mid-80's, they sure discouraged customers from using 10-40!
Jerry

haha great, so much for oil theory. thanks for the clarification...I was under the impression, from the explanation i read once, that the oil molecules are a polymer chain that unfolds when hot, and that it actually somehow...becomes the heavier weight. I guess the distinction is between consistency and lubricative properties.

The only problem running a 366 I would forsee is it would probably end up being a real bad GAS BURNER.

I have a 390 big block ford in a truck its a horror show when it comes to excessive fuel consumption, 12MPG.
I also have a dodge 360 engine in another truck and its not much better maybe 15MPG, I use both for business so I don't care but for a personal vehicle I would be not put up with that kind of gas consumption at todays prices.
I would imagine that running a 366 would be the same unless I am wrong about that one,? after all the 366 is a HIGH block engine.

Sawby, if you're going to get rid of your 305, I'll take it gladly,

I could be convinced to part with it...
now i'm wishing I hadn't intentionally started a post to trash the reputation of the 305, since I wouldnt mind selling it...

[img]http://www.towing.com/images/jodi/Tow_Truck_1326s_small.jpg[/img]

There's a '94 wrecker with a 366 (according to the caption)

Hey Sawby,
Thanks...I didn't know if the newer 6.0's were big or small blocks.

Yes the 366's will burn some gas...todays prices are rough but I don't own a vehicle that makes better than 15mpg anyways!
My everyday runner is a 78 K20 and has a 400 smallblock and that gets a lovely 10mpg, but it pulls like crazy!

Regarding oil viscosities and the possible problems with 10W-40 oil, here are a few paragraphs .

10MPG out of a 400, 66chevy thats real real bad, maybe you need to do something to try to double that number, put in a standard overdrive tranny and change your axal to a 350 gear ratio, or try a 4 barrel carb instead of a two barrel or go get a tuneup.

One time a guy who was a plumber told me a story about his work truck he had a 2003 chevy full size van that he used and was getting 12MPG out of the modern fuel injected V-8 engine in it.
So does it pay to buy a newer truck when you hear crazy stuff like that.?
Thats why I like stovebolts

Hi Guys. Very good thread. A lot of knowledgeable people here. I did not know there was a problem with 10W40 oil. I admit I have used it frequently over the years. I have a Dodge 2.2 liter turbo engine with a quarter of a million miles on it, with a long history of using this weight of oil, among others, over the years, and you know it still does not burn any oil at all. Still a good motor. It's in my daughter's Daytona now.

Sawby4president, my friend has a tall deck truck 427 in his garage next door. I do not know if there are any plans for it, but if you want to inquire about purchasing this engine from him, I can probably get you in contact with him.

The 366 is not normally used in muscle cars because there isn't much you can do with them. You can get better power out of small blocks stroked to 383's or the other big blocks. But your idea of putting one of these in your bus has merit. It'll probably run well for you for many years.

The 305 is not normally a high performance motor. It has a small bore and a very long stroke, and the valves are badly shrouded. It makes good torque, but is a low rpm, low horsepower motor. Other than that, it's fine.
You can get them up to about 330 horsepower, but in stock form, they never made much more than about 160 to 205 hp, depending on the year.

The Chevy small block, however, is a very decent-running engine. But unless you have at least 350 cubic inches, it's hard to get enough torque to make a heavy vehicle feel good. I had a wonderful little 327 in my 68 Corvette originally, but it just didn't have enough poop to feel fast, unless I revved the snot out of it and popped the clutch. The lack of torque really frustrated me.

One thing Chevy V8's haven't done that well in is the designed rod/stroke ratio. This has resulted in a problem with connecting rods coming apart in some cases. And many hotrodders only make it worse by stroking the engines, further destroying an already mediocre rod/stroke ratio, such as the 396 small block, and the 454 small block.
There are things you can do, however, to help the strokers live. The main thing is, get the best connecting rods you can afford, and the longest you can fit in there.

Saw4by...Keep that in mind when you build your Vette's 400. I strongly suggest the 6" rods in a good forged H-beam design with ARP bolts. You'll also need to get the best flowing heads you can afford, such as AFR or Brodix. Small blocks don't breathe like the big blocks.
Your Vette will be VERY fast with the 400 in it. Torque IS the best medicine.

My 400 will someday reside in my truck with a blower on top.

I am very interested in this 427 truck engine, but it's gonna be a little while before I have money to buy it or time to get it. I'm in my last semester of college, so I'm gonna be bogged down until the summer months. If he doesnt mind it sitting around for another few months I think I can find a home for it. Thanks for the heads up and all the info.

BTW the first generation of Vortec Chevy truck engines, from 1996 to I guess 1999, included a Vortec 305 that pumped out 230 horsepower. I'd be willing to bet that was the hottest production 305.