Call me crazy, pump gas 383 build
 

I am clearly a glutton for punishment and bought another boat with a frozen engine block. This time a Malibu 23LSV


This one properly froze......
https://cimg5.ibsrv.net/gimg/www.off...95c3f7876f.jpg


Given the boats size and use I am putting together a 383 with the following specs

• GM 880 4 bolt main roller block
• Eagle Cast 3.75" stroke crank (internal balance)
• Eagle I-beam w/ARP bolts
• Heads Choices
  • Vortec Iron 64cc chamber - 170cc int -
  • AFR Enforcer Aluminum 64cc chambers - 195cc int - 76cc ext
  • Skip White NKB aluminum heads 64cc chambers - 200cc int - 76cc ext
• Icon forged pistons IC735.030 - 18.6cc dish
• comp 1.6 steel roller rockers
• zero deck w/felpro .039 marine gaskets

Pistons mirror the vortec style chambers for proper quench @ .039"
https://cimg7.ibsrv.net/gimg/www.off...0576f67314.jpg



Will net 9:6:1 Static Compression

Dynamic would be

• 8.62:1 with a 206/212 @0.50 109 lsa cam
• 8.49:1 with a 212/218 @0.50 109 lsa Cam

Crazy expecting this to run fine on 91? or possibly even 89 in a pinch?

Open to cam suggestions, priority is torque and efficiency in the 1500-4500 rpm range to get the boat on plane for wakeboarding.
Reusing the Indmar 350 monsoon FI intake and long runner style wet manifolds. MEFI 5b tuned for a 383.


OE Indmar 383 hammerhead Specs
GM Forged 3.8" stroke crank
4.00" bore 18cc full dish hypereutectic Pistons
GM Fastburn Aluminum Heads 62cc chambers - 210cc int - 78cc
GM Performance 12370846 Cam 222/230 @.500" 112 LSA

9.7:1 Static Compression 8.18:1 Dynamic - 89 Octane per Manual

The aluminum heads will definitely help. Years ago, I had a 260 Mercruiser with the 76cc non vortec GM heads. I installed new GM Vortec iron heads (they had 64cc chambers if I remember correctly). I believe I calculated around 9.25:1 static compression, and I also installed a Comp 212 / 218 @ 0.050 flat tappet cam. I ran it on 89 octane with around 30* timing for at least 5 years and sold it and it is still running well. I used 93 octane the first time or two out and it had 32* timing then. No issues, so I then ran 89 octane with 32* timing and no issues. After about 2 years I pulled the timing back to 30* just in case I would get stuck and have to use 87 octane but that never happened and I left it at 30*.

My current boat is running a 350 mag i built (96 carb setup)
speed pro hypertunetic pistons (so so quench design @.038)
Original 64cc 14096217 heads
9.6:1 Static, 8.79:1 dynamic with the factory 196/206 @.50 109lsa ram jet roller cam

It's been flawless on 91 and 89.

This is my first 383 build so looking for experience. Seems like most people are building them for high compression (10-11+)

RPayne,

Why the cast crank? What's the difference in cost to go forged? Just curious...

Thanks. Brad.

I wasn't sure if forged was necessary for my goals, I believe all Merc/Indmar 350/383 cranks were cast. Looks like Eagle's 4130 Forged Crank is only $300 or so more so that's an option.Scatt & Eagle's 4340 Forged are $700 + more which seems overkill and starts to add up.



The cheapest Eagle/Scatt 383 kits put a 383 build at $6-700 more than a 350 so it seemed like a no brainer. I looked at KIT-13054L030 first but it is meant for external balance & I don't like the D shaped dish KB135 pistons for a vortec head.
https://cimg8.ibsrv.net/gimg/www.off...57274e7c9d.jpg


it's already evolving looking at forged pistons but the goal is still budget oriented built with moderate power on the left side of the curve. At some point if the cost climes too much 383 it won't make sense for my application.

RPayne,

Fair enough. As I said, I was just curious. I am in the final stages of a 496 rebuild, and I was very pleased to find my engine was built from Merc with the Kellogg "Purple Unicorn" forged crank instead of the cast GM crank, even though I am well below the ~750 HP rated limit of the cast crank. Peace of mind. For me, at least. I certainly understand the scope and budget creep thing, though. It can easily sneak up on you.

Thanks. Brad.

I'm with you on there being value in the peace of mind. Huge plus that you have the forged crank in that 496. The incremental cost to get into a better piston design and move from hyper to a mid range forged seems well worth it, bumping up to a low/mid grade forged crank is probably worth it as well.

I did not find many accounts of cast crank failures, mostly antidotal fear/quality assumptions. There was a member on here who has a Scat 9000 total crank failure running I believe 10.5:1 compression - that was a bit concerning.

With the small block at a level that's workable in your wake boat, you're not going to push the limits of the cast crank so you're probably good there. If there isn't much of a cost difference, then go forged, but I wouldn't be too concerned about it.

I would not run a 200 cc head on the 383 in this application.. you're not going to spin the RPM needed to take advantage of the 200 cc ports. I would step down to a 190 or 195. Trick Flow's Super 23 195 is a great cylinder head for what you're trying to do. You could even run the 175 cc heads and do really well. Remember, you're not making power at 6500 rpm so a big cylinder head isn't needed.

I built a 385 using the Trick Flow heads mentioned (195s), Comp XR 282 hydraulic roller, Performer RPM Air Gap w/ 750 Pro Systems Holley, and a 9.5:1 Eagle/SRP bottom end that ran in the mid 70s in a 22-foot boat. This was not an expensive build, made a lot of torque (that'll you'll need pushing the wake boat), and was really fast. We even ran a poker run with it when the Bullet was down an engine and it held its own.

And if you really wanted to do it on a budget - you can't go wrong with the Vortec head. It may be a little outdated at this point, but they still work. Aftermarket versions are better and cheap.

I was a bit concerned that 200cc heads would give ups some low range torque. I hoped to reuse the original vortecs, however 3 out of the 4 between the original and junkyard core motors were cracked. Out of the 10 vortecs I have pulled over the years only one has not been cracked..... less than confidence inspiring. A fresh vortec looks to be around 400 and another 150 to refresh the good head. The NKB's have good reviews and are hard to beat at $870 a set but I wish they were 180 or 185cc. I also like the idea of aluminum for a little more detonation buffer.

Recommendations on Aluminum 64cc - 180/185cc heads (vortec manifold pattern) that are a bit more budget than the trick flow? Everything seems to be large volume, 12 bolt intake, or more $ than makes sense.

From what I remember on the gm vortec heads to go over .480 lift you either needed to have something machined or buy different springs (comp beehive maybe?).

Just something to look into if you are going to go for more lift. It’s been 15 years though so I could be wrong or things could have changed.