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TORQUE CURVES

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readt fer motor, then test n tune jacks...started monday
Katrina 05
operation airboat 09
he said he wasn't stuck
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C

COLD

Well-known member
I was thinking you guys know what kind of torque curve your engines are produceing. I would like to get an Idea as to my best choice as far as weight of engine to highest flattest torque curve. 383 SBC is a good choice for my budget because I could probably afford some nice heads and roller rockers where if I went big block it would be closer to stock. Not as much cool stuff.
 
From another thread, a 383 w/GM tuned port injection, roller rockers, and with Corvette cast exhaust manifolds (Ceramacoted) and solid SS pipes to keep it quiet. Not too expensive, smooth, quiet and reliable. Whaddaya think?

Ken
 
A 383 SBC is hands down the best all around car motor for an airboat. Build a 383 with a hydraulic roller cam on a 108 center line, run aluminum heads most all of them are good now but stay away from AFR’s and keep the compression around 10.5 to 1. Run an air gap intake and 1.6 ratio roller rockers. It's easy as falling out of a tree to make 475 to 500HP with this combo and run on pump gas.
 
Thunder - Real ignorance on my part, so could you answer these questions.

Do the 383 aluminum heads have the same issues as the 350 zz4 do?

Are there good after market aluminum heads that you would you on a zz4?

Thanks - Pat
 
What surprises me is they can get over 400 foot lbs. at 2500-5000 RPM at 901/1 CR. an engine built like that would do the trick, Fuel Injection would be icing on the cake. We seem to get better conditions every year for carb icing. I'll have to research tricks on setting it up> Thanks for teaching me so much!~
 
The ZZ4 heads are weak in places. once they are run hot they typically will fail. There have been several posts on here about them. Carbs make more horsepower than F.I.
 
Me being the dumb redneck I am, I prefer not to have my engine controlled by a throttle position switch, map sensor, ECU and fuel injectors. One dip in the pound and your looking at thousands of dollars in repairs. With a carb there is nothing that can happen that would prevent me from making it back in. Plus carbs make more power anyway.
 
Why would you want to stay away from AFR heads? They are about the best flowing head on the market and inspired GM's LT-1 and Vortec chamber designs :?
 
It would be much simpler to run a carb. A good portion of my career was specializing in fuel and electrical. Rebuilt hundreds of 4bbl's and still do tons of electrical so wiring a FI would just be a matter of getting a wiring diagram, (we have Mitchell on demand at work). Just don't know if the computer is smart enough to know you have a longer stroke, higher compression, different cam etc. and if not, how to change it. Havent really been keeping up with the hot rod market, been running european improts for commuters latley, (audi, saab turbo, couple of bmw's). Roller cam would be nice!
 
If you have ever installed AFR's on a conventional small block you would understand. Their geometry sucks 90% of the people I know that have ran them or the times I had too use them because somebody requested them I spent more time compensating for poor geometry then I did building the rest of the motor. Also AFR’s posted flow number are bogus so is everyone else’s but theirs are more exaggerated than most. If you talk to most air boaters that run AFR’s you will find the only way they keep from breaking studs is by running a stock style ball rocker. A roller rocker will bind due to the sorry geometry of the conventional AFR. Seen this problem at least 10 times and I had too fix it for several more people. Also 3 or 4 other heads out flow and out perform the AFR stuff without any goofy valve train geometry issues.
 
Dadgummit you mean I can't believe what I read ... what is this country coming to ? manufacturers posting bogus numbers ?? say it aint so moe. That make smy head go bump in the night. next thing you will probably hear is that prop manufacturers don't actually thrust test their props before making claims of 33 1/3 percent more thrust or significantly more thrust geez.
 
Heck, when I saw "torque Curves", I thought there would be some nudie pics. :wink: Cntry, is it all a lie ? Is there no truth? :shock:
 
Thunder, you and Cntry are right about the HP .... but I'll play the "gas mieage game" with you. My bet is on TPFI. A dunk in the pond, and both of us are gettin' towed. Thousands of dollars in replacement costs for the injection? Junk yards are full of them .... I bought a used computer for an Olds for $25 and tax.

The thing is, one of these days they're gonna be comin after boats for emissions too. I'm already tryin to start thinkin that way.

BF
 
Good point BF. Youl fell better about how much less impact your making to your surroundings with a set of catylytic converters ot the back of your boat. Actually they also have a muffeling effect>
 
bF LOL I can't think that big. I hope I don't ever see the day they come after us for exhaust emissions as well as sound. But if they do I will probably cut the 12" cherrybomb types out and put in catalytic converters of course that will mean no more of that wonderful smell of 110 octane racin fuel in the air. I don't need to run it but it sure does make some great cologne. The aircraft industry will help us fight that one becuase I believe they still use a little lead in that fuel.

As for the mileage well maybe but I bet there is plenty of debate on that one. I don't have enough knowledge to enter that arena and will leave it to others to settle on. If I need more gas so far I just buy more and leave it in my truck and go back and get it or put it in a jug and put it in the boat. I quit drinkin mostly so I got room for at least one or two five gallon jugs where the beer used to ride. My new motor weighs about 150lbs less than my other one so how many gallons of gas is that 20 or 25 maybe.
 
Most of the stuff I work on is old and carburated, dont know how many electronic ignition conversions ive done. I know how to operate a manual choke just fine but the people that use my stuff have never seen one until they got to the airport. I think the nice thing about fuel injection is most paramaters compensated for. Not very often you smell that rich , unburnt fuel smell. So the computer is smarter than a drilled orifice and progressive bleed tubes in the carb to figure a/f ratio. It's like aircraft engines for cooling, Take off climbs full rich on those Marvel Schlebers. Like I mentioned carb icing was a big problem with us, they stuffed a governor between carb and intaake and even on 50 degree F mornings the carbs would turn into snowballs. I built a plate for under the carb for coolant to flow through. worked out to be a workplace air quality issue fix for the bag smashers.
 
Dontcha reckon at 1400 a pair, they would notice their heads were breaking studs?

Could it be that the broken studs are due to excessive spring pressures or cheaply manufactured rocker arms with slots that were too short?

What kind of modifications were necessary to correct this "goofy geometry"
 
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