big block versus small block

« **on:** November 10, 2013, 10:05:10 AM »

So, last season I was talking to a dude about this subject, I was (and am) thinking of a dart 502 w/ hemi heads for my float and he was trying to talk me into a small block with a twin turbo set up, what are thoughts on the comparison of the two approaches? His argument was the weight to hp ratio, and well mine is, lots of fscking horsepower argument, and it's maybe a bit less costly. What are the scjb team thoughts?

« **Reply #1 on:** November 10, 2013, 10:52:44 AM »

Quote from: bjaming on November 10, 2013, 10:05:10 AM

So, last season I was talking to a dude about this subject, I was (and am) thinking of a dart 502 w/ hemi heads for my float and he was trying to talk me into a small block with a twin turbo set up, what are thoughts on the comparison of the two approaches? His argument was the weight to hp ratio, and well mine is, lots of fscking horsepower argument, and it's maybe a bit less costly. What are the scjb team thoughts?

i wouldn't do a turbo set up unless its a race only deal. its a lot of work keeping the tune up on one of those set ups. If i were you ben i would do a big cubic inch pump gas deal. 540 or bigger, good set of heads and 10.5 to one. easy 800 to 900 hp.

« **Reply #2 on:** November 10, 2013, 01:53:58 PM »

I was always taught that there is no substitute for cubic inches. You have to run a smaller motor on the ragged edge to compete with a milder built big cube motor.

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« **Reply #3 on:** November 10, 2013, 02:12:05 PM »

Quote from: bjaming on November 10, 2013, 10:05:10 AM

So, last season I was talking to a dude about this subject, I was (and am) thinking of a dart 502 w/ hemi heads for my float and he was trying to talk me into a small block with a twin turbo set up, what are thoughts on the comparison of the two approaches? His argument was the weight to hp ratio, and well mine is, lots of fscking horsepower argument, and it's maybe a bit less costly. What are the scjb team thoughts?

While I would agree with the HP too weight ratio argument, he is forgetting one very basic and elementary argument. Turbos do not make the butt load of torque that is required for a jet pump application... Make it a Vee drive, then we have a discussion.

Put the 500" naturally aspirated big block against the turbo screamer and it will be a one sided race. The turbo deal needs to turn a whole bunch of low torque rpm to really shine in the HP game. Unfortunately with the load a pump can sustain, it will never see the full potential.

If we were talking variable torque, the turbo deal would be a monster..... IMHO you are safer with big cubic inches and lower crankshaft speeds...

I doubt this will be challenged.... SocalPSD....

GT

« **Reply #4 on:** November 10, 2013, 03:33:21 PM »

Quote from: GT Jets on November 10, 2013, 02:12:05 PM

The turbo deal needs to turn a whole bunch of low torque rpm to really shine in the HP game.

IMHO you are safer with big cubic inches and lower crankshaft speeds...

I doubt this will be challenged.... SocalPSD....

GT

How much "LOW end torque"?

The pump needs 170 lb/ft @ 3K rpm, 225 @ 4K, and 450 @ 5K. This is with an 'A' Impeller (this is achievable with N/A SBC power)

Is 6k 'Low end'? Well you'll need 700 lb/ft to spin it that fast ( 'lower crank speeds'

)
A 'AA' is even more... 765l b/ft+ @ 6K

Perfect match for a small inch twin turbo set-up.

Thats all I got.

Dan'l

« **Reply #5 on:** November 10, 2013, 03:36:48 PM »

I always wondered how a dura max diesel would work in a boat. Not really in a small jet more like a 27' tunnel or something like that. I know they make a shitload of torque.

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« **Reply #6 on:** November 10, 2013, 03:48:35 PM »

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Quote from: GT Jets on November 10, 2013, 02:12:05 PM

While I would agree with the HP too weight ratio argument, he is forgetting one very basic and elementary argument. Turbos do not make the butt load of torque that is required for a jet pump application... Make it a Vee drive, then we have a discussion.

Put the 500" naturally aspirated big block against the turbo screamer and it will be a one sided race. The turbo deal needs to turn a whole bunch of low torque rpm to really shine in the HP game. Unfortunately with the load a pump can sustain, it will never see the full potential.

If we were talking variable torque, the turbo deal would be a monster..... IMHO you are safer with big cubic inches and lower crankshaft speeds...

I doubt this will be challenged.... SocalPSD....

GT

Ill i have to say is Bob frys HighNoon is all over the turbo game. 5.98 with MAYBE 12lbs of boost and the motor is under 500 cubic inches.
The turbo thing works ben. I just think youll be more happy with big cubic inch.

« **Reply #7 on:** November 10, 2013, 04:01:00 PM »

Quote from: GT Jets on November 10, 2013, 02:12:05 PM

If we were talking variable torque, the turbo deal would be a monster..... IMHO you are safer with big cubic inches and lower crankshaft speeds...

I doubt this will be challenged.... SocalPSD....

GT

Ahh my friend I do believe the thing your forgetting is..........VGT, variable geometry turbo. With alittle tuning my old 6.0 powerstroke made full boost at 1600 rpms with little to no load and I could of dropped it to an even lower rpm. Some tuning and bam. Virtually no lag and the benefit of adjustable boost without swapping pullys like a supercharger or impellers and housings like regular turbos.

BOOM! That's right. I did it.

Although the arguement I really don't care for forced induction. I'm more of a n/a guy.

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« **Reply #8 on:** November 10, 2013, 04:29:54 PM »

Grandpa always burned in my head." Son, there is no replacement for displacement"...!!

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« **Reply #9 on:** November 10, 2013, 04:49:16 PM »

Quote from: SoCalPSD on November 10, 2013, 04:01:00 PM

Ahh my friend I do believe the thing your forgetting is..........VGT, variable geometry turbo. With alittle tuning my old 6.0 powerstroke made full boost at 1600 rpms with little to no load and I could of dropped it to an even lower rpm. Some tuning and bam. Virtually no lag and the benefit of adjustable boost without swapping pullys like a supercharger or impellers and housings like regular turbos.

BOOM! That's right. I did it.

Although the arguement I really don't care for forced induction. I'm more of a n/a guy.

Sent from my iPhone using SoCalJetBoats

Why do you need 525 lb/ft of torque at 1600 r's, when the pump only needs 48 lb/ft (@1600)

a 283 runnin' on 7 cyls would do that...

You need 525 lb/ft at ~5250 r's ('A' impeller) well beyond that sic-point-oh-oh rpm range, like twice

Dan'l

Dan'l

« **Reply #10 on:** November 10, 2013, 05:02:19 PM »

Quote from: mash on it on November 10, 2013, 03:33:21 PM

How much "LOW end torque"?

The pump needs 170 lb/ft @ 3K rpm, 225 @ 4K, and 450 @ 5K. This is with an 'A' Impeller (this is achievable with N/A SBC power)

Is 6k 'Low end'? Well you'll need 700 lb/ft to spin it that fast ( 'lower crank speeds' )
A 'AA' is even more... 765l b/ft+ @ 6K

Perfect match for a small inch twin turbo set-up.

Thats all I got.

Dan'l

I am very familiar with pump curves, it is what I do for a living...

I think you misread some stuff. This has nothing to do with "low end torque". What I said has to do with variable torque vs. constant torque. The torque curve on a pump (really does not matter what kind of pump as long as it is centrifugal) is a straight line until the point of cavitation. Meaning that the pump will consume every bit of HP you can throw at it until it starts to "slip". Slipping (cavitating) is wasted work. If you have a turbo motor (regardless of cubes) you need to give up quite a bit of "rubber to the road" to gain the required RPM to make the turbos really work.

The big block makes more use of the air it pull in because of the shear amount of cubic inches it can move, (at a much higher efficiency BTW). This keeps the torque curve not necessarily straight, but way more straight than a smaller engine at higher RPM. Especially when speaking hair driers...

Not saying turbo charging a small block is not awesome, I was merely noting to the OP that the big block, naturally aspirated and all is the top dog in this instance. The small block will never get there. IMHO you end up having to throw away a bunch of hard work to get the system to get to peak power. Similar to lower gears in a car, you gear a small block car much differently than a big block car, not saying this is a good comparison, but I think it is somewhat valid.

Give me a 500 inch hemi headed rat and I will make mouse soup every time....

GT

Quote from: GT Jets on November 10, 2013, 02:12:05 PM

While I would agree with the HP too weight ratio argument, he is forgetting one very basic and elementary argument. Turbos do not make the butt load of torque that is required for a jet pump application... Make it a Vee drive, then we have a discussion.

Put the 500" naturally aspirated big block against the turbo screamer and it will be a one sided race. The turbo deal needs to turn a whole bunch of low torque rpm to really shine in the HP game. Unfortunately with the load a pump can sustain, it will never see the full potential.

If we were talking variable torque, the turbo deal would be a monster..... IMHO you are safer with big cubic inches and lower crankshaft speeds...

I doubt this will be challenged.... SocalPSD....

GT

« **Reply #11 on:** November 10, 2013, 05:04:23 PM »

Quote from: SoCalPSD on November 10, 2013, 04:01:00 PM

Ahh my friend I do believe the thing your forgetting is..........VGT, variable geometry turbo. With alittle tuning my old 6.0 powerstroke made full boost at 1600 rpms with little to no load and I could of dropped it to an even lower rpm. Some tuning and bam. Virtually no lag and the benefit of adjustable boost without swapping pullys like a supercharger or impellers and housings like regular turbos.

BOOM! That's right. I did it.

Although the arguement I really don't care for forced induction. I'm more of a n/a guy.

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Touche'

However, the variably vane turbo deal would be a virtual nightmare on a twin turbo deal the op was talking about, not impossible, but you might as well just convert it to burn cold hard cash...

« **Reply #12 on:** November 10, 2013, 05:09:16 PM »

Quote from: jyeager on November 10, 2013, 03:48:35 PM

(Attachment Link)
Ill i have to say is Bob frys HighNoon is all over the turbo game. 5.98 with MAYBE 12lbs of boost and the motor is under 500 cubic inches.
The turbo thing works ben. I just think youll be more happy with big cubic inch.

You forgot to mention the 7,100 RPM trap rpm....

And not too far under 500"either.

GT

« **Reply #13 on:** November 10, 2013, 05:23:29 PM »

Quote from: mash on it on November 10, 2013, 03:33:21 PM

How much "LOW end torque"?

The pump needs 170 lb/ft @ 3K rpm, 225 @ 4K, and 450 @ 5K. This is with an 'A' Impeller (this is achievable with N/A SBC power)

Is 6k 'Low end'? Well you'll need 700 lb/ft to spin it that fast ( 'lower crank speeds' )
A 'AA' is even more... 765l b/ft+ @ 6K

Perfect match for a small inch twin turbo set-up.

Thats all I got.

Dan'l

Also, just adding that a big block anything turning around 6K RPM should be built to sustain a meager 800 ft./lbs. Not real easy to do, but totally doable.

« **Reply #14 on:** November 10, 2013, 05:41:19 PM »

I'd go turbo anything.
The old banks twin turbo set ups were very reliable.

-beerjet-

« **Reply #15 on:** November 10, 2013, 05:51:49 PM »

Quote from: beerjet on November 10, 2013, 05:41:19 PM

I'd go turbo anything.
The old banks twin turbo set ups were very reliable.

-beerjet-

No argument from me.....

By they way, I did some math on High Noon. So do you really think that his twin hair drier deal makes well over 1,000 ft/lbs of torque? or do you think maybe the pump is cavitating like a MOFO?

Figure it out for yourself...

7,100 RPM on a AA impeller, Like I said before, leaving a little something something on the table when the RPM gets to those levels. Not saying it is not stupid fast, but if it were a family type boat in recreational trim, the performance would be lack luster at best.

GT

« **Reply #16 on:** November 10, 2013, 06:00:41 PM »

Quote from: GT Jets on November 10, 2013, 05:51:49 PM

No argument from me.....

7,100 RPM on a AA impeller, Like I said before, leaving a little something something on the table when the RPM gets to those levels. Not saying it is not stupid fast, but if it were a family type boat in recreational trim, the performance would be lack luster at best.

GT

And this would be different in a 500 inch N/A deal, How??? I'd like to know...

Dan'l

« **Reply #17 on:** November 10, 2013, 06:09:10 PM »

Quote from: GT Jets on November 10, 2013, 05:51:49 PM

No argument from me.....

By they way, I did some math on High Noon. So do you really think that his twin hair drier deal makes well over 1,000 ft/lbs of torque? or do you think maybe the pump is cavitating like a MOFO?

Figure it out for yourself...

7,100 RPM on a AA impeller, Like I said before, leaving a little something something on the table when the RPM gets to those levels. Not saying it is not stupid fast, but if it were a family type boat in recreational trim, the performance would be lack luster at best.

GT

I have seen the dyno numbers and know what that motor and boat are capable. lets just say a doubleA impeller is not in that boat. Bob and i ran our boats up river after world finals to clean that nasty crap water out of the motors. It runs just fine cruising and gets up and goes as soon as he stabs on it.
I agree though, a normal river boat/pump would leave a lot on the table. Its a cool race set up. I still say More cubic inch. Hell thats what iam doing this winter with the race boat motor.

« **Reply #18 on:** November 10, 2013, 06:22:22 PM »

Quote from: mash on it on November 10, 2013, 06:00:41 PM

And this would be different in a 500 inch N/A deal, How??? I'd like to know...

Dan'l

Well,

I guess you would have to say that without the advantage of gear reduction, the higher RPM causes the cavitation in the ump and you are making huge amounts a HP but simply not putting all of it to the water. Similar to a slipping clutch.

I guess you could compare it to a funny car slipping the tires for 3/4 of the track, it would still be stupid fast, but it left the race winning edge on the table.

If you could make the same power with a large cube motor at a lower RPM, you could load the pump harder and the theoretical output out of the nozzle should be increased. If the output of the nozzle is increased, it can generate more top speed and the overall system will be more efficient (not fuel economy wise, but HP to water volume moved).

At the same time with the lower overall RPM (say <6000) the pump will stay hooked up longer and have a better overall performance.

Many of you guys confuse a quick drag jet with a used for fun river boat. I guarantee that a large number of the tricks used by the purpose built drag boat simply will not work satisfactorily in a pleasure boat, or weekend warrior.

As an example, add 1000 pounds to High Noon and drive it again....

I am not dissing the drag boat guys at all, but I will say that let me build my boat to what I have stated and lets race for 10 miles with two people, a 60 qt. ice chest full of beer and 10 gallons of fuel and we'll see who gets there first.

Back in the mid 90's, we did a whole lot of research and testing on what actually worked and what did not. Two things stood out over all the others, One. Once the revs exceeded about 5,800 RPM the performance started to fade away and Two. The more weight you could either remove or relocate in the boat, the better the thing drove and the more speed was realized.

Everything else faded in comparison to those two things. Including HP, impeller cut, nozzle type, loaders, carburetion and ignition systems, these would make only small percentages of difference as long as the system was pretty close to start with. It seemed that in most cases the add ons were to treat a symptom, not necessarily make more speed by themselves.

I have built four small block powered jets. Also built one with a 181 cubic inch Iron Duke, not saying it can't be done, saying that the OP's question has really only one answer.

GT

« **Reply #19 on:** November 10, 2013, 06:25:52 PM »

Quote from: jyeager on November 10, 2013, 06:09:10 PM

I have seen the dyno numbers and know what that motor and boat are capable. lets just say a doubleA impeller is not in that boat. Bob and i ran our boats up river after world finals to clean that nasty crap water out of the motors. It runs just fine cruising and gets up and goes as soon as he stabs on it.
I agree though, a normal river boat/pump would leave a lot on the table. Its a cool race set up. I still say More cubic inch. Hell thats what iam doing this winter with the race boat motor.

That boat has an AA, that came straight from Bob Fry's mouth... It is a Mike Declark AA impeller detailed by Greg Shoemaker. Not my first rodeo my man...

GT

« **Reply #20 on:** November 10, 2013, 06:30:08 PM »

Quote from: GT Jets on November 10, 2013, 06:25:52 PM

That boat has an AA, that came straight from Bob Fry's mouth... It is a Mike Declark AA impeller detailed by Greg Shoemaker. Not my first rodeo my man...

GT

Then Fry likes to run his mouth a bit more that i though.

he told me it was a 9.5 AAA. The DeClark and Shoemaker part i know is true.

« **Reply #21 on:** November 10, 2013, 06:32:37 PM »

Quote from: jyeager on November 10, 2013, 06:30:08 PM

Then Fry likes to run his mouth a bit more that i though.
he told me it was a 9.5 AAA. The DeClark and Shoemaker part i know is true.

C'mon, that never happens.....

« **Reply #22 on:** November 10, 2013, 07:54:37 PM »

Quote from: GT Jets on November 10, 2013, 06:25:52 PM

That boat has an AA, that came straight from Bob Fry's mouth... It is a Mike Declark AA impeller detailed by Greg Shoemaker. Not my first rodeo my man...

GT

I thought we were talking turbo motors not horse crap?

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« **Reply #23 on:** November 10, 2013, 09:26:17 PM »

Quote from: SoCalPSD on November 10, 2013, 07:54:37 PM

I thought we were talking turbo motors not horse crap?

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Whhhaaaaa?

« **Reply #24 on:** November 22, 2013, 10:52:55 PM »

Reading back on this thread and I am reminded of something my grandad told me once... Never forgot it.

"Do you want to gain more MPH, or build something that spins really fast and makes music women hate?"

That guy was awesome... Miss you pops....

I guess what I was trying to say in earlier posts, and came off sounding like a tool is;

Big bore longer stroke engines have proven themselves over an over covering nearly 5 decades. In that time there have been very few jet boats that "blow the mind" that have a mouse motor. There have been some hard running small blocks, but the money required to build them makes it impractical. It does have cool points, but as far as what is "better", I guess that opinion will need to be in eye of the beholder.

Forgive the attitude... Been working like a dog and living on about four hours of sleep every night.

Feeling better now..

Quote from: beerjet on November 10, 2013, 05:41:19 PM

I'd go turbo anything.
The old banks twin turbo set ups were very reliable.

-beerjet-

Those were sweet setups, but just for the sake of argument, they only did big blocks....

I had a customer with a Gale Banks original package set up and it ran pretty respectable. By no means a rocket ship. but turn key it was. If memory serves it had well over 1,000 hours on it and lived in the water at Discovery Bay (The Delta)...

GT

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