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View Full Version : 1994 TBI Performance upgrades?


sdesmond
10-21-2007, 05:01 PM
Hello all. I have been reading for a while but I don't see much on performance upgrades for the 350 Indmar TBI engine. I noticed somebody talking about an intake manifold but thats about it. Is there anything that I can do to my engine for more HP? Should I just leave it be? This is my first MC and I gets about 44mph. I know making it breathe better will always help but I dont want to waste money on it and it not be worth it. Is it a lost cause? Just forget it? Thanks all.

BrianM
10-21-2007, 06:39 PM
You could probably switch the heads to the newer Vortec heads. Pretty sure that would be a direct bolt on. Don't know if you would need to make any additional changes to the throttle body. When the TBI went to the Vortec heads in '98 hp went from 275 to right around 300 (can't remember the exact number).

dsoby
10-21-2007, 06:46 PM
While 44 mph isn't terribly fast, it really isn't slow for an inboard ski boat. Because of the design of the system, at some point, more horsepower doesn't correspond to more speed.

sdesmond
10-21-2007, 07:04 PM
I understand that more horsepower dosent always mean more speed. I do know that this hull is not limited to the speed that I am achieving. If I had the lt1 I would probably be getting two more mph out of it or so. This is not a big deal to me as I didnt get this boat to go fast. I was just curious and wanted to know if it could be done without alot of trouble. Thanks for everybods help.

andrewtimko
10-21-2007, 07:22 PM
I suggest seeing it in person first. Just my 2 cents.

JimN
10-21-2007, 09:45 PM
Changing the intake on a 5.7L TBI won't really do much- it's already a good one. Make sure the ECM calibration is the most current one, the motor is tuned well, compression/vacuum is good, fuel is clean and pressure is good, base timing is at 10 BTDC, the motor alignment is correct, the packing and strut bearings aren't restricting rotation and the prop is correct for what you're trying to do. The hull being clean and well waxed make a difference, too.

The Vortec heads were only part of the changes to the newer TBI motors- they also changed to roller lifters, which reduced frictional losses. Torque is what turns the prop.

east tx skier
10-21-2007, 09:46 PM
You could probably switch the heads to the newer Vortec heads. Pretty sure that would be a direct bolt on. Don't know if you would need to make any additional changes to the throttle body. When the TBI went to the Vortec heads in '98 hp went from 275 to right around 300 (can't remember the exact number).

308 hp in 98 TBI MX depending which literature you read.