Help an old guy with some info?

[dfwx22]

I'm old school and long forget what little I knew of BBCs - from an era with the hottest street set up was an L88 and my pride what a 3 duce L68 small port 427. The decades passed.

I bought a tunnel hull jet boat with a very tired high compression iron 468. Decided to just replace it and without a lot of thought bought an aluminum donovan std. deck shortblock setup and a Gale Banks Stage 3 twin turbo setup with intercooler cheap. The donovan is a 475 cid but very oversquare - 4.6 bore but only 3.350 stroke. Should be good for rpms -my goal over a long stroke mega motor. I'm having the pistons replaced to take compression from 14-1 to 7.5-1 so I can run alot of boost.

Now it gets complicated. The short block comes with some super "14 degree" manifold. I don't even know what that means. He said the manifold sells for $1500, comes with the short block. When I asked him to find some heads, he came back with a DART aluminum "14 degree" heads for $6500 but then said there was an off brand set of 14 degree heads he could put together for $3500. Ouch. He also said I could use any heads, but then the manifold wouldn't fit.

Here's my questions (s). What are "14 degree heads?"

I plan a radical appearing motor and with 7.5-1 compression figure I can pull it off. My hope was to put an underdriven not-particularly-great polished single 4 bbl blower on the motor with the twin draw thru turbos blowing into it. The turbo setup as it is now is only good for 8 psi and an underdriven blower added then shouldn't send the boost too high.

So the next question is if I go for the 14 degree heads (and what they cost), would regular B&M, Blower Shop, Weiland etc street blowers match to the heads? If I go with different heads will I have to change out the cam (a roller cam). What heads would you recommend? I want high rpm ability but really don't need all the horsepower I can tweak out. It will already be so radically overpowered for my boat that I don't need maximum head flow abililty at all, particularly with boosting. I'll be adding water/alcohol injection and Nitrous - but the nitrous is more looks. I do want maximum valve train RPMs ability to benefit from the destroker crankshaft and I don't have a bottomless wallet.

What would you suggest I go for in terms of aluminum heads for this setup?
Since my goal is not maximum horsepower but instead maximum rpms and for a std deck street blower to fit the heads, what components am I looking for? Where should my priorities be on head/valve/springs selection?

To clarify a bit, I'm concerned that even if I do dool out $4 or $6K for 14 degree heads, then an inexpensive supercharger would fit and next I have to buy a $2,000 manifold. As for the heads, I don't need flow, I need rpms so small lightweight valves would work better than huge ones, even if the smaller valves are inferior otherwise. What heads, valves, valve springs and rollers would you suggest?

This is not an idle question. My boat is land bound until I get this new motor put together. Thank you for any advise you have.

[ohcbird]

I typed up a bunch of info, then realized I could have stated it much clearer by just saying this:

You are about to put together a combo that will rack your brain trying to get it to run right... so sell the twin turbo kit, and the Donovan, and contact Tom Nelson about doing a proper twin turbo with EFI. Yes, there are many other builders out there, but he's building some really nice stuff right now.

Another note: I used to run alot of tunnel-hulls & would suggest that you have the boat thoroughly checked out, particularly the bottom. If you start throwing power at hull that has sat for a while (and therefore a bad 'hook'), you're setting yourself up for a very bad accident.

[deuce_454]

NOOOO dont sell that thing..... an aluminum donivan block is the ****... im not sure you need a set of 14 deg heads.. (the valve angle is 14 degrees and they flow like a Mo Fo!!!) it sounds like an 900+ Hp engine with a not too radical cam.... naturally aspirated....!

Im not sure what teh banks kit looks like for a BBC... and of ot will work with your heads, my guess is that the heads outflow those logs...if you want turbos i would say that a pair of good "standard" BBC heads was plenty.. somthing like Dart, Profiler or AFR... they will all work better in the lower rpm range and support over 2000 Hp with turbos

why not give Tom Nelson a call and get a turbokit for your application allong with a cam that works with what you want...

intake manifold wise i think i would use a tunelram base with a big water/air intercooler bolted directly to the top...

the below engine is somthing Ray Hall from australia built some years back... and it put somthing like 2000 Hp to the prop in a 19 foot ski race boat....

[dfwx22]

The “Donovan” is a seasoned standard deck aluminum BBC block that came out of a “grudge” dragster and made just over 1,000 horsepower naturally aspired in that form (14.5-1 compression and 14 degree big chief heads and matching intake.) The owner has opted to go to bigger cid therefore requiring a taller block. I do not want a long stroke and preferred a destroker for many reasons. It has a Lunati internally balanced crankshaft and appropriate con-rods. I am having the pistons replaced to reduce the CR to 7-1 to allow high levels of boosting and the option of retarding the ignition for pump gas. I’m in the chemical business and the port tank will have 93 unleaded pump gas and the starboard will have 114 octane racing gas. I will be adding a water/alcohol injector and the setup has water to air intercoolers.

I am new to boats and do not intend to do serious racing. I already have the fastest boat around – meaning the next fastest are hot jet bikes or no hot boats around. The motor in it now is an iron 468 with 12.5-1 compression, a moderate roller cam, headers, and 820 double pumper. I know nothing about tuning a hull or why that is done. I doubt I’ll ever look for the other side of 100 mph and rarely much past 80. So basically the only person I race is myself so to speak and it is about acceleration and not top speed. I asked Berkeley to pick out the best upgrades and those seem obvious other than for them to pick the correct size stainless impeller and water pickup grate.

The water around her (Florida Natural Coast) is very unpredictable due to it being very shallow (on average 2-4 for miles) with slightly deeper channels that the prop boats run in. Those can appear fast around an island within seconds and my Sanger Texas tunnel hull is not suited for waves and wakes. More than a few times at relatively slow speeds I’ve gone bouncing from wake top to wake top and less times had a wake roll across the bow and into my lap (doesn’t really have one).

I appreciate your imput. Losing weight is almost as important to me as gaining power – why the mega bucks to go aluminum on the block. Other weight lowering parts include mini-alternator, mini-starter, alloy brackets, dry cell batteries etc. I have three 4 bolt main bbc motors. An old school L88 worked up in old ways in a semi-modified V 19 footer my wife drives, a 340 hp Mercruiser “crusader” and the 468 cid currently in my boat. Adding a blower, turbos and intercooler adds weight. I hope to offset that by going to an aluminum block and heads and the other weight reduction changes.

Dumping my Donovan block to order a complete turbo motor from someone isn’t a viable idea nor do I want an iron motor even if it put out 2,000 horsepower. I’ve had a Porsche 928 (V-8 model) that had a turbo and TECIII engine management with aftermarket sequential F.I. and it was the fastest street legal car I ever drove, but fuel injection and computers are outside of my learning curve right now. First I need this motor together.

My goal isn’t merely acceleration, but the appearance of speed – the eye candy value. Putting 15-20 psi into a 475 that can turn 8500 rpms is going to make horsepower. More than I can use. But how does it look? Twin turbos blowing into an old school rootes blower will look impressive. That matters to me.

I’ve told the fella (a pro dragster engine builder) to go ahead and put on the air flow 14 degree heads with titanium intake valves. Temporarily I’ll run the old Gale Banks twin turbos (draw thru setup) into the high rise intake matched to those heads. I’m confident the old Rayjay turbos will need swapping out. And then watch for one of those ungodly costly used magnesium blower manifolds that will go with those heads and a rebuildable 1471 magnesium blower. Since I don’t know jack, let the engine builder build the motor how he sees best and then add bolt-ons. After all, its just money.
It sounds like my $20K motor project just became a $30K project and that is budget used/rebuildable parts for much of that. I have an old wet direct port nitrous oxide injection system somewhere (I have lots of old stuff like some old Mercruiser whipple twin screw/intercooler setup and FI intake. (I think they made it out of lead). Sinking $60K after Berkeley gets it’s cut into a ’79 boat seems wacko but for the first time in my life I can afford it and speed on the street is worthless – as in unusable.

The tech stuff (fuel injection and computer engine management) is going to have to wait.

WHAT ARE THE DANGERS OF MY OLD FIBERGLASS TUNNEL HULL in the below 100 mph range? I’ve run it 70ish noticing no bad traits. Flexes notably if I come down off the air hard on a wave/wake. Never knew a boat that didn’t. I know exactly NOTHING about that topic or even where to look.

PS… picked up a second Sanger Texas tunnel hull to put the wife’s hot iron L88 427 in it, probably a 475-500 hp motor. She particularly is concerned of appearance instead of performance so the painting money goes into her’s. Mine already has the $8k paint job, though aged.

Sorry to ramble on. My last actually building motors was in L88s were the hot rat motor and the best I could afford was the small port L68s WAY BACK WHEN. Build my first one in my college apartment around 1973 with a Vette 3 duce setup on it.

Give an old guy a little bit of money, ancient knowledge and a fantasy he's actually pursuing. Sounds dangerous. Steer a wide berth!