small block vs. big block

Jeremy · Post by **Jeremy** » Oct 30th, '09, 17:12

What can somebody expect the numbers to look like between the 454's vs 350's? I'm talking about cruise, WOT, and fuel. I know there are several variables, I'm just looking to gather as much info as I can. So far, it sounds like the 454's are going to be .8 or .9mpg and the 350's are gonna be around 1.2 to 1.4mpg. But what about cruise and WOT?

coolair · Post by **coolair** » Oct 30th, '09, 17:32

Jeremy,
I dont have your answers, but i was just wondering the same thing, and if you look a couple manufactures of new engines have a 6.2l small block which i think puts out similar HP#s as a 454 like 320 or 330 I think a 454 is like 340. So what do the rest of yall think about that enging option??

wmachovina · Post by **wmachovina** » Oct 30th, '09, 17:34

having had a 28 w small blocks for 12 yers and now a 31 with big blocks it seems to me the real factor is torque. Horsepower give you top speed( my 31 tops at 32 kts-probably 60 gph) at 2800 the boat runs 19kts+/-. so when you use a small block 350hp it still has less torque than a big block and That is real world performance. I think a small block while it may provide better fuel numbers, when it gets sloppy and you are in the chop it wont have the guts(torque). Torque is why I just bought a pair of cummins, top speed is for guys in speedos and gold chains, thats not what a 31 is about

Capt. DQ · Post by **Capt. DQ** » Oct 30th, '09, 18:31

Don't even thing think about small blocks in a B31. Your foolin yourself about GPH when sea conditions and wind and weight and rpm cruise speed all are factors, but you need the big blocks to bring that deep V hull up out of the water.

If you have 1:5.1 gears and proped around 18" dia wheels and get your pitch right, flow scans could show your engines better than you think. Forget numbers on a factory sheet because that does not matter till you put it to the test.

I've had 454's before in my B31 for 16yrs which is a 67 model with full marlin tower and my flow scans showed my Crusader engines @ 9.2 gph @ 3k rpm per engine, cruising at 20-21 kts. I now have Cummins 6bta-250hp diesels and I'm super happy with my combo now.

Just my 2 bits worth,

R,
DQ

Jeremy · Post by **Jeremy** » Oct 30th, '09, 19:30

Yes the torque is what counts...small block or big block, it's all about the low and midrange. But, it's not hard to build a 350/300hp. You also save a lil bit on the weight. Anybody running small blocks that can post some fuel numbers? Whats the best fuel numbers you guys are seeing with your big blocks?

Harry Babb · Post by **Harry Babb** » Oct 30th, '09, 22:00

I can tell you this
Small Block = a lot of fuel
Big Block = an enourmous quantity of fuel

Go diesel and throttle back

Harry

White Bear · Post by **White Bear** » Oct 31st, '09, 07:36

There is no substitute for cubic inches.

Carl · Post by **Carl** » Oct 31st, '09, 08:32

I inquired about this some time back...here is the link.

Not sure if I would go that route, but seemed to work okay.

Edit--
A quick re-read and I have to edit myself, they seemed to work very well, high reving Vortec 320hp 350's. Good performance numbers and said didn't lose steam in seas...
--

Carl

http://www.bertram31.com/newbb/viewtopi ... a5ac73988d

Jeremy · Post by **Jeremy** » Oct 31st, '09, 09:23

Good stuff there SIM. After reading that, it look like one of the better options if diesels are out of your price range. I don't see an issue with longevity out of a 350. There's not a small block out there that's more proven than a Chevy 350.

Rocky · Post by **Rocky** » Nov 4th, '09, 09:17

Jeremy, just my two cents, but there is another option of a smallblock with that torque of a 454. Either a stroker 350, still a proven engine,or like the one powering my truck, the LQ4 which is the 6.0L. It has the torque to pull my B31 on a trailer without the revving for horsepower.
(marinized of course with fresh water cooling). I thought I had read Merc had put the 6.2L out on that other thread, which is the LQ4 stroked even more. Just a thought , so you don't have to have 16 buckets go up and down al the time.
Rocky.

coolair · Post by **coolair** » Nov 10th, '09, 23:00

Here is a site that has the specs on the gm marine engines, you can also go to www.gmpowertrain.com i think
but sure seems like a 6.0 or 6.2 or the crazy 6.2l blown engine has plenty of torque and HP, but I dont know,
i think someone said there is no replacement for cubic inches.

http://www.marinepowerusa.com/

John F. · Post by **John F.** » Nov 11th, '09, 07:14

I don't know how this would play out in real life in a B31, but from the torque curves the 496 puts out about 125 lbs. more torque at 3000 rpms than the 6.0 or 6.2.

JeremyD · Post by **JeremyD** » Nov 11th, '09, 10:41

http://www.gm.com/experience/technology ... Marine.pdf

coolair · Post by **coolair** » Nov 11th, '09, 10:55

Ya, but they still put out like almost 400ft/lbs which i think is more than the older 454s right?

JeremyD · Post by **JeremyD** » Nov 12th, '09, 13:18

The LS3 does. and makes the torque pretty low down.

STraenkle · Post by **STraenkle** » Nov 12th, '09, 15:02

Well, like most other things you will get a ton of opinions, the only one that counts is yours after digesting all the facts and pseudo facts. In the end it takes X amount of fuel to turn the wheels no matter what engine is attached. The difference mainly comes in with fuel injection versus carb. A MPI will give better use of the fuel or BSFC (Brake specific Fuel Consumption) or the amount of power per pound of fuel used. So a well tuned and calibrated engine will give approximately the same as another regardless of size of the engine. However, producing more power per cubic inch means more heat, expansion, and wear than a larger engine. A larger piston Diameter gives a power of 2 greater surface area to dissipate heat. Yes the larger connecting rods and surface area subtract from the power, but a larger engine just isnâ€™t working as hard. I put the 496 HO in my boat mainly because of the deal I got on them, but at 25 knots I am at 30% of throttle and getting 1.2 MPG. At full throttle or 5000 RPM (Not prop right and a story that has been covered) I am at 60% throttle and going 35 Knots.

The Chevy 350 is the BEST V-8 (IMHO) ever made, but it will be working very hard to push a 31 especially if it is producing the same torque. Get a fuel injected V-8 or even better go diesel 4 cyl if you have the money.

lobsta1 · Post by **lobsta1** » Nov 12th, '09, 20:20

I believe Jeremy is asking about these engines for a B28, not a B31.
Al

Hyena Love · Post by **Hyena Love** » Nov 13th, '09, 19:22

Can you get a big block in a B28 without major issues? I don't know.

For a gaser B28, stroked 350 (383?) with carbs and decent ignition. Trade the incremental loss of mpg for the increase in simplicity and ability to work on them yourself.

Jeremy · Post by **Jeremy** » Nov 13th, '09, 20:28

lobsta1 wrote:I believe Jeremy is asking about these engines for a B28, not a B31.
Al

I'm talking about a B31. Yes, I agree that the big block isn't stressed as much as the small block when trying to get big hp numbers. But, I don't think 330hp is asking for that much out of a 350 small block, IMHO.

coolair · Post by **coolair** » Nov 13th, '09, 23:36

Ya but again, its not the HP is the torque, I was talking to a mechanic the other day bout putting even one of the new 6.2s in a 31 and I quote " they just don't have enough balls" His boss putt some hopped up big blocks in a 40 chris craft and it does 40mph, said they have like 500 and something ftlbs

mike ohlstein · Post by **mike ohlstein** » Nov 14th, '09, 00:03

By the time you blow up the small blocks and replace them with big blocks, you could have installed used diesels.

Beat the rush. Do it right the first time.

Carl · Post by **Carl** » Nov 14th, '09, 08:34

I do not think small block 350's would be my first choice, nor would I be looking to purchase Scots 496 HO engines.

However, if I was looking for new power and a "deal" fell my way, I think I would install either setup without too much hesitation.

My reason... the big block 440's & 454's are trying and tested in the 31. No guessing about it. Using something different opens the door to a higher degree of chance.

Pushing 320HP out of a 350...it's not what I would consider over taxing the motor if built right.

mike ohlstein · Post by **mike ohlstein** » Nov 14th, '09, 09:12

sim wrote:Pushing 320HP out of a 350...it's not what I would consider over taxing the motor if built right.

Of course it isn't. I push 600 HP out of my 444 cid diesel.

The difference is that my F250 isn't towing a 6000 pound trailer up hill 100% of the time......

Jeremy · Post by **Jeremy** » Nov 14th, '09, 17:14

mike ohlstein wrote: Of course it isn't. I push 600 HP out of my 444 cid diesel.

The difference is that my F250 isn't towing a 6000 pound trailer up hill 100% of the time......

Mike...600hp out of a 7.3 Ford??? Whatcha got done to that thing? Those are some really, really big numbers for a 7.3.

Rocky · Post by **Rocky** » Nov 14th, '09, 22:46

Coolair, not to ruffle any feathers, but comparitively speaking between say, my 454's in my 31 now (1970's), and the LS3 6.2small block MPI, the numbers do not lie. The torque is there, and low. Granted the old 454's are low compression and big low stress motors able to push the 31, I don't think very efficiently. LOTS of partially unburned fuel. The 6.2 will not under any circumstances waste fuel. Calibrated with precision, you can get away with less displacement, and thats coming from me, the king of the phrase "no substitute for cubic inches"!!! Now, put that fuel injection on a current, high compression 454, that's a no comparison the other way to the 6.2. Agreed?
Rocky.

mike ohlstein · Post by **mike ohlstein** » Nov 14th, '09, 23:13

Jeremy wrote: Mike...600hp out of a 7.3 Ford??? Whatcha got done to that thing? Those are some really, really big numbers for a 7.3.

Big injectors, twin high pressure oil pumps (that no longer deadhead), big turbo, big fuel lines with an in-line pump, a little chicainery to fool the computer into thinking that it never sees more than 18 pounds of boost, etc. Makes 537HP at the rear wheels. 6000 lbs and it runs 14's.

Can't keep rear tires on it.........

coolair · Post by **coolair** » Nov 15th, '09, 01:21

Well Rocky
I agree, which is why i was really thinking a 6.0 or 6.2 would do the job. I was thinking about trying to put some sort of fuel injection on my 460s, just for fun. I mean i love my my chevy with a 6.0 has enough power for me BUT i loved driving a big 1ton dually 4x4 crew cab with the ol 454 noticeably more power, pass anything on the highway but a gas station. Thank god i sold it before fuel was 3 bucks a gallon. and the only thing cooler than a big block is have a pair!!
this months car craft they built up a 6.0, stock heads, a comp cams cam, 850 holly didnt post full dyno results but says it puts out 480hp at 5500rpm and 481 lb-ft and 400 lb-ft was made between 2200-6000 says next month the will show full results with aftermarket heads, supposedly made "ton" more power
BUT
i think i want these
http://www.gmpartsdirect.com/results.cf ... r=19166392

but these r cool too
http://www.gmpartsdirect.com/results.cf ... r=19165058

Rocky · Post by **Rocky** » Nov 15th, '09, 10:34

So , I know they were not chevys, but my father's '68 B31 FBC we had, from the factory (original receipt of purchase 2nd owner) twin Ford427 Cobra side oilers in it. True big blocks in every way, that boat was Very fast to the point we would only hammer down in calm waters, and our neighbor at the time at home would drool every time we took him out fishing because he had a 427Cobra in his garage. BUT, the fuel consumption was absolutely terrible. It would just suck it up no matter what, and they were tuned to the tee. What's funny is all that torque and horsepower the boat would still not get up on a plane with one engine. Heavy boat, but that's a good thing.
Rocky

Carl · Post by **Carl** » Nov 16th, '09, 10:08

coolair wrote:Well Rocky
I agree, which is why i was really thinking a 6.0 or 6.2 would do the job. I was thinking about trying to put some sort of fuel injection on my 460s, just for fun. I mean i love my my chevy with a 6.0 has enough power for me BUT i loved driving a big 1ton dually 4x4 crew cab with the ol 454 noticeably more power, pass anything on the highway but a gas station. Thank god i sold it before fuel was 3 bucks a gallon. and the only thing cooler than a big block is have a pair!!
this months car craft they built up a 6.0, stock heads, a comp cams cam, 850 holly didnt post full dyno results but says it puts out 480hp at 5500rpm and 481 lb-ft and 400 lb-ft was made between 2200-6000 says next month the will show full results with aftermarket heads, supposedly made "ton" more power
BUT
i think i want these
http://www.gmpartsdirect.com/results.cf ... r=19166392

but these r cool too
http://www.gmpartsdirect.com/results.cf ... r=19165058

I think this is where we start getting into high strung motors. Great for the road, but not in a boat. Isn't there a lower hp marinized version more suitable.

coolair · Post by **coolair** » Nov 16th, '09, 14:52

Rocky,
I have 460s in boat, so i would love! a pair of 427s

Sim, you are no fun! :)

Carl · Post by **Carl** » Nov 16th, '09, 16:10

coolair wrote:Rocky,
I have 460s in boat, so i would love! a pair of 427s

Sim, you are no fun! :)

NAh, in a boat I feel the need to get back to the dock.

If I'm going to spend large money for new power I will go diesel.

Freebird · Post by **Freebird** » Nov 17th, '09, 14:32

Jeremy wrote:What can somebody expect the numbers to look like between the 454's vs 350's? I'm talking about cruise, WOT, and fuel. I know there are several variables, I'm just looking to gather as much info as I can. So far, it sounds like the 454's are going to be .8 or .9mpg and the 350's are gonna be around 1.2 to 1.4mpg. But what about cruise and WOT?

Can't help with numbers as they would pertain to a Bert, but I've run/owned 310/330 Sea Ray Sundancers with both the 7.4 and 5.7 in a v-drive configuration. There was very little difference in cruise and WOT between the two, but as you pointed out, there was a big difference in fuel use. There is no doubt I would go with the small blocks in that application, and I searched high and low to find one with small blocks when I was in the market.

coolair · Post by **coolair** » Nov 17th, '09, 18:14

Sim
you have no sense of adventure! :-D
but i do agree, i would never really put those in my boat, unless if was a go fast boat. But for that money i think diesels would be a much better choice.
but for me as of now, i cant justify anything but my big block fords/Chryslers.

Carl · Post by **Carl** » Nov 17th, '09, 18:26

coolair wrote:Sim
you have no sense of adventure! :-D
but i do agree, i would never really put those in my boat, unless if was a go fast boat. But for that money i think diesels would be a much better choice.
but for me as of now, i cant justify anything but my big block fords/Chryslers.

I have had my adventures..although nothing like some here...cough cough Bob L... Now I have young children, so they are my diesels.
I didn't think I was getting old, but as putting big power into my 31 no longer seems as interesting... I realize I must be.

coolair · Post by **coolair** » Nov 17th, '09, 18:30

Ya i hear ya on that. i really dont care about speed, just enjoy getting to go with the family. teach my boy, and girl how to fish, seein the wife in a bikini is fun too!

bertram31.com

small block vs. big block

small block vs. big block

Re: small block vs. big block

Who is online