More On 383's
 

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....

that's alot of cam you're going to need long risers possibly dry pipes I've been going through reversion issues on my 383s with the same cam I had to extend the risers back another 9 inches

With the hyper pistons make sure you follow the manufacturers recommendations for piston to wall and ring end gap clearances for marine engines . It is especially critical with these pistons .

ok a decent crank and s h i t pistons...better do a better research..you cant tune that 555 pcm so what are you goint to do their?? if i were you i would try and copy the merc 383 engines this way you have acess to a tuned pcm for your application..you will also want to use 6'' rods..

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

Hey Bob ,, where is your shop ? I remember talking ti one person with a prop dyno, shop is I beleive north of Austin. Would that be you ? what are your thoughts on EMI's

What are your thoughts on HP/Tq

Yes that is me. West of Austin.

I've never done any testing on the EMI, but they should be better than stock.

I think you'll be close to 400HP with that intake, but the cam is a little small for a 383. You might run 1.6 rockers and help it out a little .

fixx
 

he must have older engines then because the 2001 and up 5.7 mpi's have the 555 pcm.

That is correct. If he has the ECM555 then they'll have to go to Whipple.

I will pretty much the same set up (carb ) (bob Madara cam) , would I be ok revving up to 5200 rpm?

FWIW, I have two 6.2's [ 2003 engines] with Smart Craft in my boat with over 200hrs. Mercrusier set the rev limiter at 5150. Dustin Whipple could probably raise the ECM555's limit to 5300 and the engine would still be safe.JMO

The numbers on the back of the ECM is 16236999 and according to Marine Power Service its a MEFI-3 (for marine use). Was told it can be reprogramed with no problem. So what do you think ? Am I still ok.

Yep, you're good.

I have seen pictures of your boat, looks really nice, congrats and thank for your input.

fixx
 

is it black and silver with cooling fins or is it all silver..also what do the plugs look like?..

Mrfixall ,, its all black , fins on top , with multi pin plug on both sides ,,, i cant add picture because company comp. i could send to cell phone.

fixx
 

yes its a mefi..you must have pre 2001 engines..

yeah could be ,,, all i know is its a 2001 29ft Scarab twin 5.7's MPI ,,, i bought from original owner with 130/132 hrs on engines,,,,

Re: MEFI 3
 

Mid year production with 2000 production engines, IDK. Your engines can be easily tuned to support your project/

I wonder if you already dynoed your engines, let us know , I will be doing it in about a week.

Hope everything is going well

you will also want to use 6'' rods.. http://www.bdoh.info/7.jpg

process has been slow, learning a lot and lots to learn , i will post the results

well guys its been a loooonnnnnggggg road. with tons of research many many people that i've talked to, i settle with this..... Mike Fredrick at Beaumont Engines in Beaumont,TX. did all the machine work, assemble short blocks, reworked the heads and installed on the short block, in short built long blocks after we discussed many issues out... Bob Lloyd at Full Throttle Marine did the ECM reprogram and dyno pulls.... started as twin (300hp @5000 / don't know torque) 350mpi injection engines ...... Finished with twin (400hp @5600 / 430tq @ 4200) 383mpi injection engines .... took almost a year ....... will post a few pictures shortly

my understanding is that the intake on oem sbc heads flow pretty good on the intake side. the exhaust doesn't. i always ran a 1.5 rocker on the intake and a 1.6 on the exhaust...rm

Have you gotten the boat sorted out? How does it run?

Bob

I would love to know what this cost. I am thinking about doing this very same thing.

LC

hey Bob,,,, not sorted completely ,,, working a lot ,,, ran 73mph @ 5400 on GPS ,,,, had 23p props check and they put a little cup in the blade tips ,,, just slowed it down ,,,, taking them back to change again ,,,, tried 25p, liked the way they run, gained 8mph @4500 but wont run past 4800 ,,,, bought the 25p and will have them worked over ,,,, ,,,,,oh yeah, had one engine tried to crap a piston, got lucky and heard the knock before it came apart, did have to go through complete engine again,, only parts needed were piston, rings, hone cylinders, gaskets,,,,, ,,,,,,,,,,,,
hey looseconnection, im guessing i have about 8000.00 in each engine, keep in mind i did a lot of extra most might not do,,,, long block work was about 3700.00 ,,,, how do i post pics ? do i need to be a paid member

Get a free Photo Bucket account and attach the files...works great.

Here are my 400+ HP/435+ TQ 355 Vortecs running same cam and heads you are with Edelbrock Air Gaps. My Dyno Runs were made with 750 DP's and street headers....made 425 @5600. I am currently running 800 CFM BB QJ's with stock exhaust.

[IMG]http://i705.photobucket.com/albums/w...ps96c2bf38.jpg[/IMG]

I have seen 75 with Bravo I's/23" Mirage at 5400. boat is a 5600# 79 Formula 255 Liberator.

[IMG]http://i705.photobucket.com/albums/w...ps8ffbaf2e.jpg[/IMG]
I am turning both props CW due to a controller limitation...figure I might have 2~3 MPH pick up turning port side CCW.

A BIG plus I have discovered with the High Torque SBC's in this boat is the ability to run 27 MPH at 2000 RPM...on plane!!

Use the Photo Bucket...easy and free.

[IMG]4828.jpg[/IMG]

[IMG]file:///C:/Users/CRISSI~1/AppData/Local/Temp/5209b9fa8d771d4dda2cb486d829fd011_converted-1.jpg[/IMG]

[ATTACH=CONFIG]506892[/ATTACH]

I'm back with before and after pictures of my Scarab and its small blocks that and a couple others rebuilt. Started as Mercrusier 350/300hp MPI ,,, Ending with 383/400hp MPI ,,,,, [ATTACH=CONFIG]506915[/ATTACH][ATTACH=CONFIG]506916[/ATTACH][ATTACH=CONFIG]506917[/ATTACH][ATTACH=CONFIG]506918[/ATTACH][ATTACH=CONFIG]506917[/ATTACH][ATTACH=CONFIG]506919[/ATTACH][ATTACH=CONFIG]506920[/ATTACH][ATTACH=CONFIG]506921[/ATTACH]

I pick up the second long block on a Friday afternoon.This is following Sunday 10;30pm, just finished second engine. I'll be leaving at 4am Monday morning in route to see Bob Lloyd at Full Throttle Marine for reprogram of ECM's MEFI-4[ATTACH=CONFIG]506922[/ATTACH]

Looks like you are getting it done...that was me six moths ago...it pays off...trust me!!

yeah this was actually in May ,,, tons of work , research, , late hours , and redoing

has anyone tried Holley Commander 950 Multipoint Fuel Injection System on 383 small blocks

has anyone tried Holley Commander 950 Multipoint Fuel Injection System on 383 small blocks

Got her on the water yet?

Did you have to modify the fuel rails or change injector size?