Thanks for checking out this thread, I'm looking for advice ,proven in the field ,for some modifications to my twin 7.4 330's,the blocks are 1988's with 200 hrs on them , pulling the blocks to do internals is not an option at this point , i'm looking for some hp gains without major surgery, I know that exhaust ,carbs, intakes,and ignition ,are the key factors, just wanted to know if anybody has done this route before ,and what components they used ,and were they happy with the results ,or if not what would you do differently next time. Winter is knocking and the boat is on the side of the house waiting for some T.L.C. thanks

In the 1960's Chevy built the 396 cubic inch 325 and 350 horsepower engines with large oval port heads and small closed combustion chambers. The major problem with modifying a 330 is that the compression is too low (8.0:1) with the flat top pistons. Installing the 396 heads on the 330 will increase your compression (9.0:1) without changing the pistons. The closed chamber heads will flow very well to about .500 inches of valve lift.
Install the heads, an Edelbrock Performer RPM 2-O Q-Jet intake manifold, Gil exhaust manifolds and retain the stock carb and ignition system.
If you can change the cam (with the engine in the boat) use an Edelbrock Torker Plus camshaft, lifters and valve springs.
This combo will be good for 400 horsepower (with the camshaft).
Sincerely
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE

small blowers with low boost. cheap and dirty way to make power. The low compression ratio is actually better for a blower engine. Grante dteh cast internals aren;t but you want to up your HP anyway. I asked about doign this (prior to having my new engine biult) and dustin whipple responded, he said that 330s repond well to low boost and are ok setups as long as you don't go overboard.

you coudl rolly pickup a pair of used prochargers chepa. Actually there was pair of 174 blower for liek 2k for eth pair. Then you need carbs. Overalll you coudl do it pretty cheap. You need to make sure that your carbsa re setup correctly though.

Puder, thanks for the advice,you too Dennis ,guess in my first post i left out the assumption of superchargers which i have been considering,basiclly because of the best hp gains ,downside being you cood blow the blocks up ,but hey what the hell their already 14 years old anyway!! If I decide to use blowers what other components would i need to purchase to complete the job,ie,carbs exhaust,ect. any input would be helpful since i'm new to the supercharging school, thanks ,Crossbow

Dennis is that assumming peanut port heads or large oval heads? My problem is that I have a Gen6 and a Mark4 engine. Makes it hard to match the two. The Gen6 always has about 400rpm on the older Mark4 The mark 4 I know has Large oval heads.

Jon

All oval port heads were large until about 1985 or so (marine engines). Peanut port heads were never made in the sixties. The early heads would, of course, be Mark IV heads that wouldn't work on a Gen V or Gen VI engine. An even better head for the new blocks is the large oval port heads found on the 1997 and newer L-29 Vortech 454 engines. They also have smaller combustion chambers for an increase in compression with flat top pistons.
Sincerely
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE

you coudl kill your block with the other mods too....

toss arod and its pretty much over either way. As for buying stuff for the blower setup. You have a couple option. You might be able to get away with your current carbs if theya re big enough. I think procahrgers are your best bet if your trying to keep all the origonal stuff. YOu will need to make some changes to the setup of the carbs anyway you go. I forgot to mention that the pair of 174s was either in the classifieds (formal) or the thread based classifieds. But youcoudl geta decent deal on them. BUT have the carbs tuned by somebody decent.