67 SN Resto/Mod rev. 2

Time to get back to work on the 67. I apologize that I haven't done very well at documenting each step, but I have been making progress.

The first step this winter was to finish getting the floor installed. I debated the different options with the floor, but ultimately decided to permanently install the floor and glass the floor to the hull sides. The lateral supports and the floor have a minimum 1/8" gap between the side of the hull.

I bedded the lateral supports with thickened epoxy.



The floor (5/8" ply) was test fit with the engine/trans installed, then pre-drilled for countersunk screws. All floor panels were soaked in CPES and have a layer of 4oz cloth on the bottom. I installed the floor using biax on the stringers and lateral supports. I screwed the panels down until the epoxy cured overnight, then removed the screws and back-filled the holes with epoxy.




The floor was then glassed to the hull sides using 2" tape, 4" tape, then a layer of cloth from the primary stringer to 3-4" up the hull sides.

Here you can see the gap between the floor and hull under the 2" tape.


Laying out the cloth.


All glassed down. I have been fairing the bilge as well in-between glassing the floor.




I was happy with the result of the floor. It isn't as flat as a pool table but I think it looks good and it's super solid.

After the floor was down I moved on to the part of the project I have been dreading. This hull has a ton of cracks in the gel, and I was never going to be happy with just wetsanding/buffing. So I decided to re-gel the whole hull. I have never done anything like this before so I don't know what to expect, but regardless, I have started grinding off all the old gel so I'm on my way.

I separated this portion of the garage with plastic and got to work on grinding. I started with a DA and 24 grit and got nowhere. Then I tried an inline with 36 grit and also got nowhere fast. This gel is hard, and it's thick. I used my angle grinder with a 60 grit flap disk but this was too hard to control and be smooth and I ended up gouging a few spots so I quit with that. Ultimately I ended up using a sanding disk adapter for my 4-1/2" angle grinder with 36 grit. I'm pretty happy with this method as it's a good balance of speed/control. To anyone contemplating doing this to a boat, this is a nasty job that is going to take quite a while. I'm wearing a Tyvek suit, respirator and lab goggles but the amount of dust is incredible.




So far I ground the transom, 90% of the top deck, and about 1/3 of the port side. I hope to be finished with the hull sides by this weekend. I will then flip the hull and start on the bottom. Anyone have any tricks on sanding the gel from the tight inside corners around the raised lip on the bow?

No more than 5500 and yes a propshaft upgrade is going to have to be done.Maybe not for this season but definitely been thinking about it.Picked up World tall deck block 4.6 bore and 4.25 crank that makes 565 was thinking 598 but that roller cam I have been saving just won't support that many cubes.I sold the Edelbrock heads now thinking Brodix BB-2's have to find that happy medium between velocity and volume

oldcuda wrote: Think keeping small port ovals would be a big Boo-Boo.I am a major torque junkie but the engine will have to breath a little better to get into rpm range you need for all around performance.I am planning a lot of prop for mine but 565ci,10.4 comp,with a lot more cam think it can handle it.

I dont recall the details of your engine build, but the sheer number of cubic inches you'll have on tap would make me think you might approaching prop limitations if youre staying with a 1" shaft and trying to keep the revs down... or are you going to 1-1/8"? Our BFN will pull some props made for 1.23 boats (15+" pitch) north of 5500... How fast you planning to spin yours?

Sorry Craig, Im afraid we've gone off on a tangent here!

Mark, yes, the part I disagree about is how a ski boat will respond to hp/torque and where those peaks best benefit performance... most people think that low end torque is what gets these tractors moving quickest but I have not seen that to be true. Im not seeing those hp numbers out of the mods youve described, but Ive only built one BBC so Im hardly the authority. If it runs into the mid 50's like the 425hp HO 454's of the mid 80's then that'll prove me wrong! To get it moving that fast at such a low RPM will require a pretty huge prop... such a wheel may not exist for a 1" shaft. It should be faster than stock though, and that should have you in the 50mph range anyways. Thats definitely faster than I care to fall, but I can think of a few uses for extra power- pulling a huge line of footers or barefoot racing come to mind.

I agree that static CR doesnt tell the whole story... but since we know that exact cam does just fine on pump gas in a 340 with a static CR approaching 11:1, cant we say with pretty good certainty that he'll be safe with a static CR of 10.1:1? The only additional variable would be if he were to install it off center, right? Otherwise Im missing something.

It'll be interesting to see how your boat runs. A few of your assumptions are contrary to what we've found to be true when building a fast ski boat. I think that cam is a bit warmer than you think- did you measure your stocker? 50-51mph may not be out of the question. Clearly these tractors dont have the same speed potential as a purpose built outboard, but the BFN's in particular seem to respond pretty well to power... well, at least they dont behave too badly when pushed well beyond their factory ability. 92 may be out of the question, but I dont think 70 is.

mark c wrote: Don't rely on just your static compression ratios when trying to figure out if the engine will run on pump gas or not. You will also need to figure the Dynamic compression ratio as well, especially with the smaller duration cams that these marine engines run. Theres not much valve overlap to bleed off excessive compression in these cams. As I was working thru my big block for the BFN, I started with +30cc domes on the pistons I wanted, which calced out at just about 10.4 to 1 static compression with all the other parts going into the engine. But when I ran the DCR on the parts the compression came in at about 9.25:1. You need to keep the DCR between 7.5 and 8.5:1 if you want to run pump gas without detonation. As a result I was forced to go with 22cc domes with a 9.4:1 static and an 8.3 dynamic, and my cam has 15 degrees more duration than yours does. The most critical spec is where the intake valve closes on the compression stroke, the closer to BDC the higher the DCR will be, so each cam will bring a unique number to the design. Mine is 47deg ABDC as a reference, yours is around 43deg ABC. You can't directly compare a BBc to a SBF but you can calc yours out yourself at the link below. http://members.uia.net/pkelley2/DynamicCR.html I might have been able to keep the +30cc domes with the cooler running engine but it would be right on the edge so for once in my life I'm going a little conservative on the compression ratio in an engine build. It will be at least 2 full points higher than the stock compression on the 454 was, so it should be a lot better without giving me to many hassles with detonation, or idle quality.

All good info, Mark, but lets not scare the guy. This is basically the only warmed up RH Chrysler small block cam that has been available for the last few years (its now NLA like the rest) so Reid has some good history with it... and I think some of the builds it was used on were approaching 11:1. Craig wont be breaking any new ground, it doesnt sound like.

Not that its here or there, but the stock (static) CR should have been in the low to mid 8's on that 454... Im sure its listed in the manual in the reference section. Did you swap out the heads for larger ovals? Warm up the cam? Buffalo did both with his '88 and had a CR similar to yours in the mid 9's and it runs real strong, ~53 IIRC.

I left the dished pistons in my Ford back in the day because I wanted to run it like I stole it on the cheapest pump 87 I could find. I never dabbled much in the dynamic side of things outside of knowing advancing cam timing tends to build more cylinder pressure. Good for low revving torque producing engines. I have never installed a cam at anything besides a degree verified straight up.

My 67 really detonates on pump gas and higher temps. This phenomenon only happens at or above the 4k rpm mark. Distributor has stock curve and I have only verified timing to 3500 rpms. I assume it is over advancing above 4k rpms.

You're right on the money Alan. I soaked that first board for 24 hrs and then steamed it for 50 minutes (it was 3/4" thick) and it did pretty good, but did show some signs of minor cracking so I think it needs more time to absorb the moisture. I wasn't too concerned, it's just going to be burried under the floor for nobody to see, but I will definitely let the spray rails soak longer. I always envisioned pulling a board out of the steamer and it being soaking wet, but it's pretty dried out.

Guess I'm getting a little ahead of you!! haha.

Tim,

Maybe the piece of white oak I have is a little dry, but it wasn't going to bend to the hull without steaming. I could get the backer to bend but it was approx. 3/8" thinner and was a lot more flexible. The steam bending process is pretty simple, cheap, and effective, so I'll just bend them as close as possible and get this backer mounted. I just need to get it in there to proceed with the rest of the floor.

Craig, I havent attempted to attach the spray rails to my 1st gen yet, but the thought of pre-bending them never crossed my mind. The bend is gradual enough that Im sure a straight piece of lumber would install without a problem. Of course, a little bit of steam bending ahead of time probably cant hurt!

On the backer, I had tossed around a few different ideas but still havent come up with one Im crazy about yet... though most of that stems from wanting to use composites instead of wood (which generally dont hold screws as well). A full length backer would give you complete flexibility on where to put the screws, but if thats not a concern (like say you know you want to use 8" spacing) then you could always piecemeal the backer(s) instead of trying to bend a single one. I think I would be hesitant to bed the backer in if youre using wood... its certainly not necessary from a structural perspective. CPES for sure, and then a minimal amount of glass to keep it in place is probably what I'd recommend.

Just over 10:1... beautiful!

Zach, the specs on that cam are the same as the stock 340 (auto) grind:

Duration @ .50 lift: 209/220
Duration @ .06/Rocker Ratio lift: 279/289
Gross Valve Lift: .429/.444

All Chryslers got 3" exhaust. Im not sure that 350hp is in the cards, but 320-330hp like Marshall's 340 might be- though he was closer to 10.5 or 11:1, IIRC. That boat was a hoot.

Craig are you using one piece of lumber for the spray rails? Your garment steamer will work fine, that's what I used on the Hurricane for all my bending.

I made my spray rails a little differently though and didn't need to steam them at all. Used 1/4" thick strips laid up on the hull for shape and then epoxied them together. You could do the same using a piece of wax paper between the hull and your spray rail stock so you can remove them for shaping. Then cpes, paint and mount permanently.

Obviously I had it easier than you because I could just clamp to the chine but I would think you could use the install fasteners to hold it in place temporarily while laying it up.

9.5:1 will be fine on pump gas... thats actually a little conservative, if anything. I wouldnt hesitate to shoot for 10 to 10.5:1.

I think youre seeing things... its pretty tough to tell the exact width of the driver's seat in that pic as the driver is obscuring the starboard side. The seats are identical in all of the boats that I have encountered with that style of bucket. Here's a pic Pauly Banana posted of his '68 that he purchased new. Im planning to put identical buckets like this in my '67SN.

The Performer RPM is a totally different animal- thats a great choice. So are the J-heads. Whats the story with the short block- will you be rebuilding it from scratch? Piston choice will be key to get your CR where you want it... the J's have pretty big chambers.

Like I said, the original observer bucket would have been identical to the driver's seat (no wider). I'm sure a previous owner had widened yours. It shouldnt have blocked the gauges originally I dont think, but it would have done so rather than having a notch. The observer seat shown in the '70-71 above is also non-original, I believe it would have had the same fiberglass bucket as the driver's. Never seen a notch like that on a factory seat.

From the '68 brochure: