67 SN Resto/Mod rev. 2

I would be careful not to call anything a "fiberglass pan" as it will only add confusion- the late 60's Mustangs had removable fiberglass floor pans that were primarily cosmetic- they sat on top of a traditional glass over foam floor construction.

Most of the other boats from the mid-late 60's through the early 70's that I am familiar with had fiberglass over foam floors, and then vinyl wrapped plywood floors over that (the late 60's Mustangs with the fiberglass floor pans being the exception). The layer of glass over the foam was relatively thin, I dont think it was intended to provide a lot of strength. The wood or fiberglass "cosmetic" floor that laid on top of it provided the necessary impact resistance. So, it would seem that the floors in these boats werent really structural. Which makes sense, since the non-foamed versions of the same boats didnt have their floors tied to the walls.

By the mid-late 70's CC made improvements to the floor design... they ditched the vinyl wrapped ply "cosmetic" floor and instead beefed up the glass layup over the foam. They also eliminated the remaining exposed foam under the gas tank. These floors were pretty well tied to the walls, and I havent seen major evidence that doing so creates enough of a stress riser to promote significant gel/glass damage due to impact. CC did keep the wood portion of the floor (between the motorbox and battery box) away from the hull walls though, so Bruce's advice to keep a gap between the ply and the wall is probably not a bad idea. I would still tie the floor to the walls with glass though, as otherwise there will be a pretty big water intrusion point, and it will also be difficult to hide that gap (cosmetic eye sore) on a boat that doesnt have side panels (which SN's did not).

Hollywood is nuts the gap is important, and the joint between the wood and hull can’t be tapered and controlled like that of the fiberglass, and the fiberglass layer will buckle in the event of collision (even minor) where the wood will not, after a very small amount of compression it becomes the rigid structure. If you put an abrupt rigid support in the middle of a flexible section and send it out into waves it will fail, the more abrupt/rigid and the more flexible the worse the failure will be.   

But he is right on about the cross pieces just being there to hold down the floor and mount the seats that is what they are there for.. , it is always important to know the primary function of the part of the boat you are working on. The hull is there to keep the water out. The stringers are there primarily to transfer the thrust of the engine to the hull. The floor is there to hold you up and to attach things too. Making them do anything they don’t need to do is generally a bad idea. (A floor in a foamed boat is also there to keep water out of the foam).

It should be pretty easy to see by now there is more than one way to skin this cat.   What I would do and recommend for this boat is certainly not what I would do/have done with a newer boat with a carpeted floor.   The early fiberglass boats were very similar in construction to wood boats, it’s somewhat analogous a body on frame construction vs unibody construction on cars. With these boats the transition between earlier and later construction is not clearly defined, between that and the different uses and budget people have for their boats means there is not one right, or even one best way to do these things. I hesitate sometimes to get to far into it on the interwebs because you can never get enough detail out there to cover every situation, and occasionally I have to cringe when I see somebody applying a technique that I have posted to a situation where it is either wrong or simply overkill.. the best advice is if you have any question why or what you might consider doing in a particular situation ask specifically about it. Then read the millions of conflicting answers you get, consider the source and then do it however you want. in general in you repair something exactly as it was originally designed you are safe, any modification from that and you probably should have a pretty good idea of why you are making that modification and what you are trying to achieve with it. Its the difference between being a contractor and an architect, or a mechanic and an engineer.

Some things generally always hold true, don’t rigidly bed something to a surface that you expect to move. Other than the stringers I don’t recommend bedding anything securely on one of these boats, whether it is dangerous or not it simply isn’t needed. If these were fast boats with hulls built with weight in mind the stringers wouldn’t get bedded you would want foam between the hull and the stringers.   

What transitions you do have should be tapered When I run a bulk head or a vertical floor support to replace foam I usually leave an air gap, and tab them to the hull with 3 thin overlapping pieces of fiberglass tape.   Filling in the gap between a floor and the vertical portion of the hull I is better done with a few more layers than that, but the smoother the transition the less likely you are to have problems

If you are going to let something move then let it move.. if you aren’t then make the whole thing rigid. Rigid bulk heads widely spaced , perpendicular to the direction of travel is the worst case loading. More, lighter weight supports connecting all the structure together is better.. a good bonding structural foam is probably best case structurally … except for the whole water absorbing thing.

I have a couple earlier non foamed boats to redo, my plan for them is to put coosa stringers, and then to run cpes coated wood floor supports across the top of them, then put down the vinyl covered cpes infused plywood floor.   The wood being preferred to coosa in those cases because it holds screws down better, and as long as it isn’t actually fiberglassed in it will provide more than enough life and if it doesn’t will be easy enough to change out.   But again, more than a few ways to skin that cat.

C-bass i have 2 almost brand new looking after Market 318 manifolds if you do have to go this route.....they're here in Cincinnati...i could meet you in Batesville to help with drive time....i'd be willing to go $175 for both. I can send pictures(see my email). I'll also give you my gas tank out of a 1968 mustang, it's in a little bit better shape but will still need to be restored, but the neck is still 100%...

send me an email if you want pictures....i pretty much have a complete parts 318 engine i'm slowly taking apart, so if you need anything else me know....email me.... petercraft@gmail.com


Thanks

mine are both squared off....also tank is yours if you want to pay shipping check out the fore sale section of the forum. i can mail ya it for a good price with my work's UPS discount.

btw if you do happen to toss a manifold, i'd love one of the bolt on end plates for my 273, it's being held together by glue right now.

The driver and observers buckets would have been exactly the same, originally. The observer seat was intended to be reversible (face forwards or backwards) though facing it forwards on a SN was probably not common (and silly IMHO). CC used the same seats on many models. You can see a pic of them in the SN in the 68 brochure. It looks like you made the observer seat wider?

I'm not sure you needed to add the difference in the height of the intakes to the motorbox (1.5-2" of extra clearance is the norm) but you just bought yourself some breathing room. Depending on your goals for that 340, you may want to reconsider the Performer. It's not very highly regarded, and since the intake you choose will require mods for the cooling system, I'm assuming you'll want to get that choice nailed the first time. What heads will you be running?

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:

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.

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.

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, 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!

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.

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

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.

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.

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.