572 bbc reliability

Automotive powered airboat discussion.
SWAMPHUNTER45
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Re: 572 bbc reliability

Postby SWAMPHUNTER45 » Fri Aug 26, 2016 7:11 am

The GM Performance spec is 15 degrees initial and 36 degrees at full advance.

My JYC (junk yard Cadillac) 542 is running a stroke .125 longer with more compression and the same HEI. We don't use a vacuum advance, Mr. Branch sets up a strict mechanical curve and it works excellent on an airboat. As discussed earlier, fuel octane and jetting is very relevant in a long stroke engine. My personal opinion is to jet it slightly rich and run 25% AV gas in fresh 93 pump or get the Sunoco 110 and blend 15% with the race fuel, it makes a difference. My engine temp decreases with an AV gas blend and idle quality improves. My 542 just likes this AV gas blend better than straight pump gas or the Sunoco blend.

Bottom line is the BBC 572 was built for the street rod not an airboat. It will never be a WT, Branch of Felber but if you respect it and break it in with patience you will get several years out of it. Get it hot, run the balls off it or use **** fuel and you will be another sob story.

Wishing you the best with this and keep us in the loop on your project.

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Deano
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Re: 572 bbc reliability

Postby Deano » Fri Aug 26, 2016 9:57 am

rbjscott wrote: . . . I have 550 hours on my boat. Another boat with this [timing] curve has 1100 hours on it. A 572 making 700 hp. also runs this timing curve.
With these kind of non-issue hours, it looks like they must be pretty darn close to where it needs to be.

Still . . . given other things historical, a man could split the difference and upgrade the exhaust valves (as was mentioned more than once) without to much grief if would afford him some extra piece of mind, and help prevent an avoidable heartburn.
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RJC5778
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Re: 572 bbc reliability

Postby RJC5778 » Fri Aug 26, 2016 2:38 pm

inconel exhaust valves would be a great upgrade for piece of mind, as with anything mechanical if you keep care of it and treat it right and learn what it likes it will give you many hours of operation, start dogging it and running cheap gas/oil, it wont last as long and you know where that leads, my understanding is exhaust valves and valvetrain geometry are big factors in the BBC engines lasting. 572 BBC is a good motor, just need to tweek it to live in an airboat/marine application. good luck with the boat, post pics if you can and keep us updated on it.

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Waterthunder
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Re: 572 bbc reliability

Postby Waterthunder » Fri Aug 26, 2016 6:42 pm

Please keep in mind timing is based on 3 key elements. Cylinder pressure (some say compression but that's incorrect) , fuel quality and load. A super technical person will also say flame front travel speed but that is usually very closely tied to the other 3 unless you have some crazy cylinder head with a super fast chamber. So base your timing on a combo that matches ALL OF THESE CIRCUMSTANCES.
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F0zzy2
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Re: 572 bbc reliability

Postby F0zzy2 » Sat Sep 24, 2016 9:30 pm

I second inconel exhaust valves, when I built my 580 I was told that was the weakest link in the GM crate engines. I purposely built my engine and love it. I just broke 108 hours on it last month moose hunting, my boat is big and heavy and I haul a lot of weight on dry ground. I have my timing locked in at 34 degrees no vacuum or mechanical advance. I also agree it takes a lot of carb tuning to get the AFR correct on these big motors, I would recommend AFR gauges in both collectors.
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18X8 Silverdollar- 580 BBC- CH-4 2.67 ratio - 4 84" S Series Blade


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Re: 572 bbc reliability

Postby BWXSTREAM » Wed Feb 15, 2017 10:20 pm

well thanks for all your input guys but i still have a few more questions on the big 572........it is bone stock how do i tell how rich or lean my carb is running should i run a oil cooler what octane gas should i use what should i keep the rpm below for longest life.......i guess what im trying to say is i need to know it all and i need to know it all relatively fast

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Deano
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Re: 572 bbc reliability

Postby Deano » Thu Feb 16, 2017 10:25 am

Sure glad you didn't just buy a plane and are asking how to
fly it before you go looking for Amelia Earhart in the morning. ... :)

Best to install a wideband AFR gauge, which will help you keep from hosting an unplanned bar-b-q.
An oil cooler is generally considered cheap insurance and adds longevity whether literally needed or not.
Running 93 octane is probably the best idea given the number of unknowns.

You haven't shared the gear ratio of your belt drive or what specific prop you are turning, so it
is difficult to make an RPM guesstimate. Generally where longevity is concerned, the slower you
turn it the better, as long as you do not overload it with lack of gear and/or to much pitch.
"The suppression of uncomfortable ideas may be common in religion and politics,
but it is not the path to knowledge; it has no place in the endeavor of science."
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