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Old 01-26-2010, 10:12 AM
TRBenj TRBenj is offline
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10:1, good good. That means my desktop dyno numbers were based on the right info. From what Ive read on here, the BBC needs some compression to respond to a cam, so while its definitely on the high side, thats not all bad. We ran 93 octane all summer and it wasnt pinging with the new HEI (DUI) distributor. Total timing was right around 36-37 degrees (initial was 12 or so).

Im not a believer in "lead substitute"... I think its a marketing scheme. Im running non-leaded gas on all of my boats, even the old ones (1971) that supposedly require the lead. Im putting the money Im saving on the substitute away to pay for a valve job someday.

Im guessing it has a tiny cam in it too. We didnt gain any top speed with the smaller prop that let it turn up to 5200 (the other one only turned 4900), so it wasnt making any more power higher in the RPM band. The stock 330hp cam would have peaked around 4400-4500 with the peanut ports- maybe a bit higher with the 990's... so a cam making power up to 5500 should hopefully wake this thing up. I cant say that it had any lope at idle- it was pretty smooth, idled down to 600-700 rpm just fine and started very easily. My fingers are crossed that it still has the original cam in it- that would give us a good opportunity for more easy power! Great info on having a machine shop measure the cam... Ill add that to the list of things to do ASAP.

We cant change the length of the exhaust, obviously, but we're eliminating the mufflers and going from 3" hose to 4". Even if we go with some classic aluminum log manifolds, they should flow better than the cast iron pyramids... plus save 50-80 lbs. True headers would be nice and we're keeping our eyes open, but they may not be in the budget.

Youre correct- the Borg Warner 72C is a stout tranny and will handle all the power we can throw at it. It doesnt care how many RPM's we turn either- it would see more strain if we tried to turn a steeper prop... which we're not.

Feel free to clue me on on any speed secrets you know- not all will translate to a direct drive inboard but some may help. We're still using the boat to ski, so prop options are limited- but any info helps! Luckily the hull seems to get up out of the water pretty nice for a ski boat, which is certainly helping us. My other Nautique wont even break 50mph, even with a 350hp 351w pushing it! A few guys I run with have tweaked their hulls to get the bow up more at speed- this involves grinding the "hook" out of the last few feet of the hull... but those were flat bottomed boats. Not sure how that would affect this v-hull. The flat bottomed boats tend to run faster with a bit more weight in the back seat (people, lead, coolers, etc), but this boat didnt respond in the same way. Im still learning!
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