Another BFN Rebuild

My guess is he's had the picture all loaded up on photobucket ready to link since monday morning.. and that he has a while before he has to look over his shoulder for another bfn.. .

JoeinNY wrote: About time Dave, Tims been waiting all week for someone to ask that question

Someone else sort of quasi kind of asked that question earlier this week. I was going to provide what I believe was the answer based on a conversation Tim and I had at WL, but decided it was his place, not mine, to provide. Still true.

TRBenj wrote: ~40 gallons of water later, the boat seems to ride a bit higher in the water and has picked up a few mph.

What does that make your top speed now? 65ish?

A few more updates and lessons learned as we enter spring of 2013...

1. The cavitation noted above was actually transmission slippage. A fresh rebuild this spring solved it, as well as the terribly dirty neutral shown in the video.

2. On/off nature of the secondaries is now resolved as well. As discussed here, we swapped to a different secondary diaphragm housing (with a pressed in brass insert) and went 2 steps heavier on the spring (white to purple) and we can hold any speed we want.

3. As Ive said a few times when people consider foamless stringer rebuilds, any drain point is also an intrusion point! Found a battery box mostly full of water this spring, so we emptied it. 10 minutes later, its full again. Strange, considering the boat was on the trailer... in the garage. Turns out that the (now drain-less) battery box was the low point every time the boat was stored on the trailer and lift (boat sits a bit nose-low) and thus, a good portion of the water that made its way into the boat drained to the battery box rather than the bilge. The bulkhead on the front face of the batt box (shown below) that was originally meant to be a drain point *just in case* any water made its way under the floor, did just the opposite and let water in instead. Apparently the o-ring seal doesnt quite work as advertised. ~40 gallons of water later, the boat seems to ride a bit higher in the water and has picked up a few mph. So, not all bad news.



For now, we'll just be more careful to keep the nose higher when the boat is stored... but on future rebuilds, a few things would help prevent this from happening. Installing a battery box drain is one of them. Moving the drain access point to another (higher) location is another.

Tim, Awesome project ....That motor hits like a muscle car! (A sound we all love) You did an awesome job....as explained through the thread the research, design and selection of engine components is as much work as the build if not more and it is nice to see it come together as planned. Very encouraging!

Slap a 1.23 to that bizzzoat and then you can run standard rotation parts

Tim, I'd be interested in what you figure out. I have long term plans for the 67 BB that I have. We are looking at a build that will put out similar HP numbers to your 454. I thought that Mastercraft put out a 14x18 RH prop for the powerslot but I was mistaken. We have one of those lying around and they are LH.

The current setup on my 67 is actually LH. With the scarcity of the BB in those days its possible that Correct Craft put out a few LH rotation boats. I might be inclined to leave it LH. I was going to convert but sounds like it could be a bad idea? I think my prop on the 67 is a 13x16 but I haven't looked at it in a while.

We added ~5/8" of glass to the inside of the hull in that area in case we want to notch the keel. But I'm not overly eager to tear the boat back apart just yet. There aren't really any rh 1" shaft props any bigger in diam than 13" in the sizes we're looking at, anyways.

15x12, that's crazy. That's a tiny prop for 450hp, even for a 1:1. I'm guessing that's a v-drive with some kind of reduction to boot?

The more blade surface, the better, when it comes to avoiding cavitation (so I would think) so yes, a larger diameter prop might help some. An increase in pitch seems to be more effective though- the 12.5x15.25 612 cavitates less than the 13x14 and 13x13 wheels.

No room to run a 14" prop though... the original 13x15 Federal was within 1/2" of the hull and left a lot of gel and rudder port damage. The 13" diam Acmes offer a bit more since their blades are raked back a good bit- but still less than 1". Starting somewhere around '81, CC notched the keel aft of the strut (by ~5/8") to allow the use of the 14" props. Most 454 BFN's made after that point came with 14x14's.

Tim,

Enlighten me...wouldn't a 14" diam. prop get a better dig for the cavitation issue?

nice sound!

wow that a dirty neutral!

No, but if I could find one big enough, Id slap it on. I suspect that little 11.5x15 2-blade that we tried on the Tique is better suited to the lighter boats that can get out of the water- but who knows. Since that prop seems to be comparable RPM-wise to the small boat props (12x13 OJ and 12.5x12 Acme 3-blades) due to its smaller diameter and minimal blade surface area, I suspect it will be waaaaay too small on a big block.

I suppose its time for this thread's yearly update... and hopefully the last!

After thinking it over all winter, this spring we decided to go forward with the most reliable (and most expensive, ha) option- custom RH roller cam conversion. The goal was to not tear this engine apart again anytime soon! We worked with Bob Madera at Marine Kinetics (Rochester, NY) on the grind specs and ended up with a wilder cam than before. Due to our engine's high-ish compression ratio, it was decided to go with a longer duration in order to keep cylinder pressures down (and thus avoiding damage causing detonation). Combined with the roller's steeper ramp rates, it allowed the lift to be over .600. Output was projected to be in the ~480hp @ 5600 range.

Of course, in order to use the roller cam, we added tie bar roller lifters. The more aggressive profile required upgraded (Isky) valve springs as well. When measuring our heads to see if our valves would work with the new springs, we discovered that the water ingestion from last year's overheat had left a good amount of corrosion around the valve seats... so off came the heads for a full valve job. Went with +.100 Ferrea valves (SS 6000 series intake, Super Alloy- similar to inconel to withstand higher temps- exhaust) on the rebuild. Custom Manton (Series 4 for guideplate use, 3/8" diam, .120 wall) pushrods rounded out the changes.

We fired it for the first time the Friday of the CT mini reunion and promptly put it in the water. Only a few minor glitches thus far (leaky valve covers, wicked dirty neutral on the tranny, leaky secondary bowl after shut down), but the oil has stayed clean and we havent blown it up yet... so Im declaring victory. Dad and I took our first double barefoot run behind it that first day (Im hoping someone has a picture?)

Pic (thanks Morfoot and Chris) and a quick video (thanks Brian) from that weekend:







(Secondary spring needs to be stiffened up... it was right on the verge with that load in the video, hence the in/out.)

So far, performance has been every bit as good as we had hoped for. We still havent found a prop that we cant cavitate in the midrange. Here's what we've run thus far:

Acme 1598 (13x14 3-blade): 62.8mph @ 5700rpm
Acme 430 (13x13 3-blade): 61.9mph @ 6000rpm
Acme 1868 (12.5x14.25 4-blade): 56.4mph @ 5500rpm
Acme 612 (12.5x15.25 3-blade): 61.7mph @ 5500rpm

So far, I like the 612 the best, as the boat seems to cavitate a little less with it. I expect it to speed up a bit with a full tank of gas and a little weight in back as well (which were the conditions the 1598 and 430 were run under)... I dont see why it wouldnt be the fastest prop of the bunch based on the RPM's its running. The 1868, on the other hand, pushes the nose down HARD in the low 50's, which explains its lower top end numbers. All of the props do this to some extent (as do many of the other faster CC's, like Joe's '83, so I think its partially attributed to the steep strut angle), but this prop does it earlier and harder than the others. It appears to be a different style of prop than the Acmes Im used to seeing (its much flatter, so I may refer to it in the future as a "pancake" prop). This is the stock prop on the Excalibur powered SN 200's, so its stern-lifting abilities may have been a positive on a slalom dedicated tug like that. I may still try the 1442 (13x15 3-blade) and 422 (12.5x15.5 4-blade) on the boat, as it doesnt seem to have any problem pulling the larger wheels out of the hole... its more a battle of being judicious with the throttle to keep the cavitation in check. It will hold ~2800rpm for a split second and then get up to 5k as the boat continues to gain speed. Sort of like a snowmobile... but I think it would be a lot quicker if we could find a prop that hooked up.

Good info Roger- I assume Gen 5 and Gen 6 cams interchange with Mark IV's?

Will be good to finally meet you next month!

Not coming from any direct cam experience mind you, but I would expect that the case hardness is a bit less of an issue with a roller lifter on a steel cam blank than it is with a flat tappet on a cast blank... I never seem to know what is going on with roger these days sounds like a florida sit down is in order.