Cool thread! Thanks for asking Rocker!

tunnel ram
 

Mine works great. 565ci. 750hp efi hydraulic roller cam 92 gas. A tad over 90 in my 92 27 fountain. Two miles per gallon.

This is a very interesting thread!
The original question was why aren't more of these set ups used in boats. My take onit is that blower motors are easier to build, make more horsepower (and of course torque, which is KING) at lower RPM's. They also have the benefit of longer life due to lower operating RPM's.
Having said that, there is a TON of power to be had in a proper "tunnel ram" manifold and carb set up. Look at NHRA Pro Stock cars. 500 cubic inches, two carbs, gasoline (120 octane +/-) and 1300 horsepower. Problem is, it makes peak torque at 6300 rpm and peak power at 9500 RPM:eek: :eek:
I don't know anyone that would want that kind of rpm's in their boat!
When running Comp Eliminator, we ran a Sonny Leonard 437 cubic inch motor with carbs, and switched to a Motec EFI system. While we lost 5-10 horsepower on the top end, the torque numbers increased all across the RPM. Bottom line was that the first time out with the car, we ran a full one TENTH of a second under the national record at the time!!!
The point is that with dyno time perfecting runner length (the critical issue in a "tunnel ram") and the benefit of individually adjusting the fuel AND timing PER CYLINDER, you have an incredibly efficient fuel system. The only other problem with boats is the wet exhaust system. It makes it tough to place EGT probes and O2 sensors to get the maximum performance and tunability from the motor. We ran our car on "open loop" a couple of times testing in order for it to automatically adjust the fuel to the perfect level (again per cylinder) within the guidlelines we specified (10% max adjustment), saved the fuel map and ran after that "closed loop" with no other issues. Can't do that in a marine system with no O2 sensors.
Sorry for the long post, but this is cool stuff.:D :D

Here is a 565 cubic inch, 8-71 blown BDS fuel injection system on a Pro Street motor I just sold. It made 900 + hp on pump gas.
It was brutal for torque numbers!

Slick piece that was going in a 1965 GTO, but I ran out of time to mess with it. Still have the car though.;)

Here are some pics of my TR set-up. 900HP NA PUMP GAS.

on dyno at freshen.....

I can't talk about the technical aspects of it, but here is a picture of mine.

I just seen two 750HP Tunnel rams at Tyler Crockett's yesterday. He was just completeing them. They dynoed over 750. They are going in a Nortech Cat.

I watched my engine builder dyno his 3yr old NHRA pro stock motor that was down on power. it made 1280HP @9400. The pulls started at 7500. VERY VERY impressive to say the least. I couldn't believe the fuel that thing consumed compared to mine. Of course 1250 Dominators like fuel esp at those RPM. He had to change valve springs every 2 pulls. On the last pull, power fell off by like 65hp and they thought they lost a couple of valve springs....it was the vacuum pump...65HP from pulling 30 inches of vacuum. Unbelievable. The heads actually had aluminum lines that ran to jackets around the exhaust valve seats...I said what in the hell are those for. "It cools the seats and its worth 7hp". Everything counts to those boys.

By the way, top teams in NHRA are making around 1380HP today.......

That exactly right on the dyno figures, depending on who you talk to, and which dyno they use:rolleyes: :rolleyes: :D .
They are an inpressive piece. The interesting thing is that once you get the valvetrain geometry correct, springs are no longer an issue! We could run all weekend and never change a spring. On a previous motor though, it ate at least one spring every run.
Titanium springs weren't any better. In fact, they would break instead of become weak. Very bad thing at 9500 RPM:eek: