OFF TOPIC QUESTION

[captainluigi]

Anyone on this board have hands on experience with GM 7.4 lt.? More commonly known as BBC,s or just 454's. Got a problem in one of two that I thought there might be an ''old school gear head'' here that might be able to help me think my way through this.Just breaching out., Lemme know.

[qship96]

Just fond memories of riding in a 73 Vette with a 454 bigblock and sidepipes

[goody90q45]

I thought it was going to be a fishing question.

[carfrk666]

well what is it that u wanna know?

[maxnix]

Porcupine head truck engines!

Don't rev worth oatmeal, but torque and fuel consumption are prodigous.

[captainluigi]

And it is torque that gets the work done. Correct on both counts. 35 GPH WFO and on full step @27knts. Found my info at a Big Butt Truck forum then confirmed by local knowledge. Counter rotating motos do have big whiney cam & crank timing gears that hammer with wear.

thanx!

[oldmako]

As far as boat motors, I believe that they have truck cams in them as opposed to regular car cams. They are designed to give more TQ, which is pretty much what a boat needs. My 23' center console 351 has a truck cam and then some. It pulls like a mother up to about 3000 but after that it's mostly noise. I get about 30kts at 4200 (WOT) but I typically run it all day at 2800-3000. This equates to about 23 kts and 8-10 gph depending on sea state and load.

454s are good motors but very thirsty. If you can keep the secondaries closed while on plane they're fine. They're also very expensive, so if you can get a lead on a good used one then jump. If it's FWC it will last a LONG time. Mine has over 1500 hours and 10 years on it. I expect to get another 5 at least. IOW, I will not replace it until it requires me to do so.

New oil every 50 and aerosol lube ALL over it. Salt water is a *****!

[Q45tech]

Other than higher friction from big bore diameters [ring area] all engines consume ~~ the same amount of fuel per HP created - same with TORQUE.

The reason Asia and EU have long had annual displacement taxes to discourage the potential for excessive fuel consumption especially at idle.

If idle and cruise are held near 14.7 AF then displacement is a PURE reflection of MPG and variable with RPM.

The problem is IMEP and internal friction VARIES with rpm.

The optium point from an efficiency stand point is 500 cc per cylinder, thus 3.0 liters for a V6/I6 and 4.0 liters for a V8..................anything larger trades efficiency.However as many engineers have learned you can stretch this to 575cc or 4.6 liters for a V8 and only lose 1-2%.

Things like VVT and roller rockers [low friction valve train] and variable displacement plenums can cover up some or most of efficiency lost at a price.

[captainluigi]

You are spot on as to the thirsty part. However I don't find parts to be at all big $. Problem I had was that the counter rotating (strbrd) moto uses gear on gear for timing. At a appx. 1000 hrs. they started to hammer. Sounded like destruction was about to take place. actually more noise than problem once I tore it down.

Had a 351W in a 26'Searay and found it a lil' underpowered w/tanks,weights,beer,ice etc. aboard.

I've heard of Irvette boats. I think they were built in central Fl. Not sure. So many boats, so lil' time.

Still they are cheaper than women. But you know the phrase. If it floats, flys, or f****, RENT IT. However I am a full time live aboard now so renting is not an option.

And the Gummint pays me to fly in roto crraft.

Good hearing from ya.

[captainluigi]

Dennis, would you please explain paragraphs 3 & 4. No comprenda amigo.

[oldmako]

Had a 351W in a 26'Searay and found it a lil' underpowered w/tanks,weights,beer,ice etc. aboard.__________________Yep. Mine is only 23 but it's a bit underpowered when full. Can't imagine pushing a 26 Searay with a 351.

I've heard of Irvette boats. I think they were built in central Fl. Not sure. So many boats, so lil' time._________________Little Mountain SC. Bought out by Pleasurecraft Marine and then shut down eventually. Too bad it's a great fishing rig. Straight inboard.

Still they are cheaper than women. But you know the phrase. If it floats, flys, or f****, RENT IT. __________________

Number one I bought used and do all my own wrenching so that helps.Number two, well I get paid to fly so that's taken care of.Number three, well that's another story but so far she's been worth it.

[captainluigi]

Congrats, all I can say for myself is two out of three ain't bad.

[MinisterofDOOM]

Does the boat motor have stupid low compression like the car/truck motors did? Or was it able to use better pistons thanks to EPA-exemption?

[captainluigi]

All forged internals w/4 bolt mains The comp ratio varies on the earlier carb motos between 8.5 to 8.7.

These large cruising sedans (relatively at 38') often set for months while the fuel even with a stabilizer is turning into some other chemical. I try to keep mine w/no more than 50 or 60 gal. I use a lot of 99.9% IPA & Redline + Stabil. And the fact that they time @ 8* BTDC it works out OK.

I'll then run in close, refuel to 400 gal. total then cross the stream. Bahama fuel is big $.

Considered re-powering w/ the 8.2 diesels as they are plug & play other than running a return fuel line. $ for $ no sense. Almost the exact same fuel burn & MUCH more expensive to repair.

B.O.A.T. = Break Out Another Thousand