Upgrade small blocks...
08-20-2008 | 09:39 AM
#21
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From: Spicewood, Texas USA
I've built quite a few packages like you are looking for. You already have most of the parts you need. Build them into 383's, do some port work on the vortec heads and install larger valves, and the correct roller cam. You should have the older style 4 bbl intakes with a throttle body, which is pretty decent so you can stay with that. I have reprogramed the MEFI3 computers and been able to make 400 HP with this package in complete trim, tested with wet marine exhaust. I would highly recommend tuning it on the dyno or in the boat with an A/F meter.
Last edited by bobl; 08-20-2008 at 09:43 AM.
08-20-2008 | 10:17 AM
#22
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I would like to get as much power out of my 1999 350magMPI's as possible w/o losing reliability....So where to begin:
I have a valvetrain problem with the port engine so I will have to pull that head for starters....
BTW...It's a 99 Active Thunder 28' w/400hrs on the motors & Bravo drives....Already added new Stainless Marine exhaust systems...got 150-200 more rpms...
Currently spinning 4-blade 14-1/2" x 26" Hydromotives @ 4800rpm's I see 72mph...To get to 80mph I figure I need 400hp each motor.
1. Can this be done (efficiently$$) w/o supercharging? reliability?
2. If I go through the top ends completely & decide to add the Prochargers, what to expect? Reliabilty?
3. Why would the manufacturer say that the hull is not intended for over 80mph? Liability issue? or is it
a handling issue? My Switzer went 81mph w/200hp Merc & not that I recommend it, I felt fairly comfortable (after the learning curve; ie. throttle through the chine-walk @65). This AT hull is exceptionally built; deep, strong, straight lines...why limit it to 80?
4.What can I expect to spend on a sb top end "freshen -up"?
5. Should I consider new cams? New aluminum heads?
I know many will say that the small blocks won't produce enough torque; but I don't want to put BB's in a 28'AT; plus I like the fuel efficiency of these motors....It is such a nice set-up as is; if I can't do any upgrades I'll just fix the valve problem and freshen up both motors and leave stock.
Thanks in advance for ideas...
I have a valvetrain problem with the port engine so I will have to pull that head for starters....
BTW...It's a 99 Active Thunder 28' w/400hrs on the motors & Bravo drives....Already added new Stainless Marine exhaust systems...got 150-200 more rpms...
Currently spinning 4-blade 14-1/2" x 26" Hydromotives @ 4800rpm's I see 72mph...To get to 80mph I figure I need 400hp each motor.
1. Can this be done (efficiently$$) w/o supercharging? reliability?
2. If I go through the top ends completely & decide to add the Prochargers, what to expect? Reliabilty?
3. Why would the manufacturer say that the hull is not intended for over 80mph? Liability issue? or is it
a handling issue? My Switzer went 81mph w/200hp Merc & not that I recommend it, I felt fairly comfortable (after the learning curve; ie. throttle through the chine-walk @65). This AT hull is exceptionally built; deep, strong, straight lines...why limit it to 80?
4.What can I expect to spend on a sb top end "freshen -up"?
5. Should I consider new cams? New aluminum heads?
I know many will say that the small blocks won't produce enough torque; but I don't want to put BB's in a 28'AT; plus I like the fuel efficiency of these motors....It is such a nice set-up as is; if I can't do any upgrades I'll just fix the valve problem and freshen up both motors and leave stock.
Thanks in advance for ideas...
IF you really want a BIG project - and it will be a real project. If your going to pull motors then - go for the lower end rebuild with the 383 kit as many have mentioned. Buy a good pair of heads with bigger valves already in them (AFR/brodix) and re cam with a roller ground something like an Engle EP20/22. Tune it on a dyno with an AF meter (also previously recommended) or risk doing it again in 30 hours.
This will get you to 400+hp and you WILL hammer the gimbles they will no longer be "bullet proof" after that - I've gone through 3 of them in 10 seasons, and since yours are already high hour put that money aside right now........
Going BB at this stage means 8K in exhausts alone.
Really dude- just fix it and go boating.
Uncle Dave
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08-20-2008 | 05:01 PM
#23
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From: Raleigh,NC & 1000 Islands,NY
[QUOTE=Uncle Dave;2658296]Recommendation from someone whos been there many times with a SB powered boat-- Fix the broken parts and enjoy it.
IF you really want a BIG project - and it will be a real project. If your going to pull motors then - go for the lower end rebuild with the 383 kit as many have mentioned. Buy a good pair of heads with bigger valves already in them (AFR/brodix) and re cam with a roller ground something like an Engle EP20/22. Tune it on a dyno with an AF meter (also previously recommended) or risk doing it again in 30 hours.
This will get you to 400+hp and you WILL hammer the gimbles they will no longer be "bullet proof" after that - I've gone through 3 of them in 10 seasons, and since yours are already high hour put that money aside right now........
Going BB at this stage means 8K in exhausts alone.
Really dude- just fix it and go boating.
Very well said...I've come to that conclusion after all the "opinions"! To gain 10mph I would have to spend 5 figures and lose reliability and efficiency...what a waste of time and money....fix-r-up and go boatin' sounds good to me.
BTW, I just had the gimbals rebuilt...that wasn't cheap. I need hydraulic steering; esp. if I add any hp.
IF you really want a BIG project - and it will be a real project. If your going to pull motors then - go for the lower end rebuild with the 383 kit as many have mentioned. Buy a good pair of heads with bigger valves already in them (AFR/brodix) and re cam with a roller ground something like an Engle EP20/22. Tune it on a dyno with an AF meter (also previously recommended) or risk doing it again in 30 hours.
This will get you to 400+hp and you WILL hammer the gimbles they will no longer be "bullet proof" after that - I've gone through 3 of them in 10 seasons, and since yours are already high hour put that money aside right now........
Going BB at this stage means 8K in exhausts alone.
Really dude- just fix it and go boating.
Very well said...I've come to that conclusion after all the "opinions"! To gain 10mph I would have to spend 5 figures and lose reliability and efficiency...what a waste of time and money....fix-r-up and go boatin' sounds good to me.
BTW, I just had the gimbals rebuilt...that wasn't cheap. I need hydraulic steering; esp. if I add any hp.
08-20-2008 | 05:26 PM
#24
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Yeah what a pain huh? I call it the circle jerk of speed.
motors /Hydraulics/drives/props- its an endless circle of spending that you cant get back when you sell. You already made the #1 call onthe exhausts and you can probably get a few MPH playing with prop tuning if you really want.
IF you dont do hydraulics and you can go 80 a cable failure could kill you and your crew without much warning, or stop you from turning quickly enough to get out of trouble so youd have to do that..............
Your rig looks pretty cool to me and cruising at 55-60 with 12-17 left over is pretty respectable for the dollars per hour your spending to do it. Have fun and let us know what you do either way!
Uncle Dave
Laveycraft 2750 Ilmor 710
Laveycraft 20.8 Sebring 406 SB
Fleetwod nitrous toy hauler
Yamaha raptor 700/Kawi KFX 450
Nissan Titan
motors /Hydraulics/drives/props- its an endless circle of spending that you cant get back when you sell. You already made the #1 call onthe exhausts and you can probably get a few MPH playing with prop tuning if you really want.
IF you dont do hydraulics and you can go 80 a cable failure could kill you and your crew without much warning, or stop you from turning quickly enough to get out of trouble so youd have to do that..............
Your rig looks pretty cool to me and cruising at 55-60 with 12-17 left over is pretty respectable for the dollars per hour your spending to do it. Have fun and let us know what you do either way!
Uncle Dave
Laveycraft 2750 Ilmor 710
Laveycraft 20.8 Sebring 406 SB
Fleetwod nitrous toy hauler
Yamaha raptor 700/Kawi KFX 450
Nissan Titan
08-21-2008 | 07:08 PM
#26
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If Uncle Dave would only follow his own advice -he'd be a much happier wealthier guy.
I have a habit of learning "by mistake."
Uncle Dave
Laveycraft 2750 Ilmor 710
Laveycraft 20.8 Sebring 406 SB
Fleetwod nitrous toy hauler
Yamaha raptor 700/Kawi KFX 450
Nissan Titan
I have a habit of learning "by mistake."
Uncle Dave
Laveycraft 2750 Ilmor 710
Laveycraft 20.8 Sebring 406 SB
Fleetwod nitrous toy hauler
Yamaha raptor 700/Kawi KFX 450
Nissan Titan
