More On 383's
01-15-2014 | 06:55 PM
#41
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Joined: Oct 2004
Posts: 8,390
Likes: 7
From: medellin colombia, pablo escobar's lil town
Sitting here reading this thread and learning a lot. I too am going through this tough time with engines. I have a 29ft. Scarab, twin Vortec 5.7's, MPI fuel delivery, advertised at 300HP, 1.5 Bravo 1's, 23p Mirage Plus... One engine shattered an exhaust valve. Did tons of checking, asking, reading, and pretty sure the cause was from a riser gasket leaking.... To fix the problem ..... Going back as 383's .. parts are: Eagle rotating 400 steel crank, forged 5.7" rods., dished hyper .030 over pistons, vortec heads with match port(machineing valve guide down), holley MPI single plane intake (2000-7000), full roller rockers, comp cam XM270HR (int-.495, exh-.503, @.050 int-218 exh-224, int centerline 110, lobe seperation 112, RPM range 1500-5500. Will use stainless marine or emi manifolds. The boat ran 68 on GPS @4900, 100 gals. of fuel 2 people.... dont know what my results will be... I am going to get them dyno , one shop can do prop dyno, the other is engine dyno. I am more concerned with being dialed in right (fuel, timing), but will like to know HP/T ...... I would really like anyones honest input on this.... first engine is about half complete....
Last edited by ratman; 01-15-2014 at 06:57 PM.
01-15-2014 | 06:59 PM
#42
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Joined: Oct 2004
Posts: 8,390
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From: medellin colombia, pablo escobar's lil town
Merc 6.2's use 5.7 rods & hyper pistons. Scorpions do also. Yes, 6.0 rods give a better rod angle and of course forged pistons are better, but for his application this build should work fine. I don't think you're far off on your build, just don't want to spin it to high RPM. No way should that cam cause reversion, even with stock exhaust. If I remember from our conversation, you have a Mefi 3 computer so tuning is not a problem. Just for the record I can dyno the engine in or out of the boat, with full wet exhaust. I also have a riser for the stainless exhaust with an 02 bung. If you opt for the EMIs be sure and get an 02 bung welded in.
Bob Lloyd
Full Throttle Marine
Bob Lloyd
Full Throttle Marine
01-16-2014 | 10:22 AM
#43
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Joined: Oct 2000
Posts: 1,382
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From: Spicewood, Texas USA
01Scarab29, I'm doing a couple more 6.2's very similar to your builds. Finally got them on the dyno and they made 400 HP just like yours. These are using the Edelbrock Victor intake with the stock throttle body adapted to it. As I told you I would, I tested it with a 1000 CFM 4 bbl throttle body. It picked up 15 HP, and torque was higher across the entire pull.
Bob Lloyd
Bob Lloyd
01-16-2014 | 11:00 AM
#44
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Joined: Jun 2012
Posts: 231
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From: Toledo, Oh
I just took my stock 350's, put edelbrock vic jr. intakes on them with trick flow 195cc heads, what an improvement. Also when with Classic Fast EFI system, 4 barrel 1000 cfm throttle body. Never ran them on the dyno, but it took my compression from 9.00:1 to 10.25:1, sound healthier, and run wayyyy cleaner. Nothing like tuning the AFR to exactly what you want with timing.
