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Old 12-07-2012, 10:56 AM
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Yes, another 383 SBC thread!

Hi all-

I'll do a little intro post in a bit, but I've been searching the forum and haven't come across the answer to my specific questions. I've been very impressed with the knowledge I've found so far, so I'm hoping we can put our heads together and get some answers. Let's say my experience level is decent with small blocks as I've built them successfully in the distant past (warm 355 in a 1965 Chevelle bracket racer, stock 400 sb in a 1969 Blazer, 350 in a 1971 Monte Carlo, etc.).

My issue is that I have a bigger cabin cruiser boat that when all loaded with fuel, anchors/chain rode/other gear, spares, tools, fishing gear and 5 150# people scales out at 7640. So, a slow heavy boat. It has a volvo-penta 280 outdrive on it and had a the AQ255 motor (that's a basic stocker 350 from 1977). I've always felt this motor was severely underpowered for this application but ran it because it was reliable and that's what it came with when I bought it last year. It took forever to creep up on plane in decent weather and light wind chop, but if you try and get up on plane in anything over a 1-2 foot wind wave it just couldn't do it. I was thinking about going 454 marine engine (280 outdrive can handle the torque) but this 355 gave up the ghost earlier than I planned. I do have an Edelbrock performer intake, Edelbrock 1409 650 CFM Marine carb and a Mallory marine points distributor.

So, thinking that the quickest/cheapest route was a local rebuilder that does marine long blocks, I ordered one up and started yanking out my old one. Delay after delay (ever tried pulling an SBC out of a 27' boat on a trailer in your driveway before??) brought me to the end of boating season and a chance to re-think this before I put the boat back on the moorage for next season.

What I have from the machinist is a basic build - a .060 over 010 block with rebuilder pistons and stock "low rpm marine cam" (hydraulic flat tappet and no cam card came with engine). Stock 1.94/1.50 76cc (882 or 993 castings, can't recall now). Due to the outdrive, I have to use a 153T flywheel to bolt the drive adapter to.

What I'd like to know is how would some of you guru's go about getting the most torque out of this motor in the 2800-3300 RPM range? Looking for fuel efficiency as well (110 gallon gas tank just ruins my day at the fuel dock). I'm thinking just taking the block and swapping in an internally-balanced 383 kit. Interally balanced because I could re-use my stock flywheel and I have an nice 8" balancer for the 350 already. What kit/brand would you go with for that? Is the 64cc Vortec head conversion in my future? Worried about static compression ratio, as I need to keep it under 9.5/1 or my already-expensive fuel goes up in price. No need for lift to go over the .450 range due to the use here, so no need to mod heads for that. This motor will never see the high side of 4000 rpm, and with the prop I have it will need to cruise right at 3000 for hours on end. Idle MUST be smooth and as low as possible (600 RPM max) to handle shifting the outdrive in and out of gear without damaging it and moving around in tight spaces. Everybody else's boat around my moorage space is a lot nicer than mine and I don't want to be swapping gelcoat with them because an engine stumbles shifting in and out of gear in a tight spot!

I think that's about it. Hope to have some of you guys jump in and throw suggestions out on how to do this right the first (ok, second) time. Cams, bottom end kits, heads, intake (if I go Vortec), etc.

Hans

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Old 12-07-2012, 12:25 PM
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Well the problem here is that your current motor may do the job and the old motor may have been lame to begin with. 7k pounds is not that heavy.

I would not touch the 350 unless you are sure the cam is not right. You can buy a cam that will produce at 3000 rpms and always do the same with good idle and some performance above 3500. But if you raise compression, cubes or rpm then you will be burning more gas for sure.

Do ypu have electric automatic plane, trim adjustment thingy... Best to make sure that system is working properly. If its not you will have a hard time to get on plane. Sorry dont know much about boats.

Ask your rebuilder for the camspec he has them laying around somewhere. Probably uses the same cam in everything. Then compare to what was shipped in the boat new. You may already be over cammed or right on the money. If you get what i am saying. Boat may have come with very small cam From the factory and there might be a much bigger one installed in the new long block.
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Old 12-07-2012, 12:28 PM
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As for pulling the motor you need a chain hoist a tall tree and a fat friend. Lol

Put ear plugs on all the kids so they wont take any motivational words to school with them.

You can always let the air out of the tires if you need a few inches.
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Old 12-07-2012, 12:30 PM
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This is what I would do,and I will speak in generalities for now. Based on a 383,,,:
Dart cast iron 2.02 heads,small roller hydraulic cam,9:1 CR,street master intake,first generation,(performer is ok) 750 cfm marine carb,forged crank,good rods,forged pistons,the engine would get a precision balance,would also upgrade to a marine MSD ignition.
I would wire in an idle stop solenoid with an over ride switch.
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Old 12-07-2012, 12:56 PM
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Hans-we have used a OEM cam and what was nicknamed "the 383 cam" in a crate 350.Smooth idle,adds sufficient torque in the rpm range your asking for,still can use your valve springs.Here is the spec's:

431/451
288/308 Duration@.050 tappet lift
196/206 max lift 1.5.1 rocker ratio
centerline 109

Part#14097395

Summit still sells it.
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Old 12-07-2012, 02:29 PM
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hcompton-

My motor may have been pretty wheezy when I got it, don't know. I did get it out by building a big gantry and used a chainfall. Had to take the oil pan off to get that last inch of clearance to get it over the gunnel after taking the wheels off the trailer. You are 100% that the earplugs should have been distributed before I got started on that one... all the neighborhood kids are prepped for the Navy now. I'll swing by the builder tonight to see if he has a cam card laying around. Not hopeful, however - you should see this guy's place - you basically walk between the cylinder boring machine and a parts washer to get to the "front" counter. I might try and sneak a pic and post it up here later... I could spend hours looking at his stack of cores - he's an open modified circle track racer and hoards cool old motors and parts.
I've got functional electric over hydraulic trim tabs, and to get the boat up on plane takes some finicky adjusments in smooth water but even they won't get the job done in waves. I've really got no problem with dropping this motor in as-is, but I do NOT want to have to take it out again if I'm disappointed with the performance. I figure if I have to put in another $1500 to get what I think I want, I'd rather do that now instead of do it later. Right now, I could sell the crank, rods, pistons, rings (and heads, if I go Vortec) as "newly remanufactured" and recoup some of my money. Crank that engine over, though, and everything loses half it's value.

Vinnie -
You'd really go with the Dart 200's, steel crank and forged pistons on a motor that won't see anything over 4000 rpm??? I'm truly limited to this by the outdrive. Had some stern warnings from a guy who knows that over 4K does not make the upper gearboxes happy on those old Volvo 280's. Not going roller cam on this one, that's for certain - I'd just get a whole '96 or so Vortec truck engine if I was going that route. Mallory dist has no issues - spark is bright, blue and jumps a big gap if I want it to. Points are in good shape and considering I can be up to 20 miles out of port while Halibut fishing, I really like the simplicity of points if something goes wrong. It sounds like a cool buildup for a street machine or a truck that might see 6000+ rpm, but your list of parts is pretty pricey for a seriously low RPM motor, isn't it?

Gary-
Holy cow - 288*/308* at .050"?? I'm thinking your numbers got jumbled a little, no?
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Old 12-07-2012, 02:44 PM
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no.I would use the 180 cc darts, a roller cam for fuel economy and torque.the egine would peak before 5,000 rpm.
The cam would be arount .480/.480 lift with duration around 216 @ 050 intake and 210@050 exhaust.
use points if you want, The reason I said dart 180s,the castings are meaty and flow well...more for reliability,same with balance and forged pistons,run the engine at 3500 all day
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Old 12-07-2012, 02:46 PM
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Copy that, makes sense-
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Old 12-07-2012, 02:53 PM
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also,did you understand why I said to put an idle stop solenoid in the system with a bypass switch?
BTW,that 383 with mild cam would make 380 hp and as much as 300 plus at 3,000, torque over 400 by a ways. The leg would be a weak spot if you abused the power.
its better to have power you dont need than not enough

ask your circle track guy about a budget 366?
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Old 12-07-2012, 03:35 PM
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Actually, I missed that idle stop thing.

Those volvo 280's can take some torque - they regularly put them behind 454's. If I made an honest 400# and eased into it I shouldn't have too much of an issue. They just don't like too much RPM, as I understand it.

The only 366 I'm aware of is a tall deck truck motor - don't think he has any of those laying around for his race car!
What combo are you thinking of that makes 366"?
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Old 12-07-2012, 03:41 PM
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Gary, looked up the cam you're talking about. Looks great, but I'm not thinking I want to go roller on this for $$ purposes - unless the performance I'm looking for needs it. Are there any flat tappet hydraulic cams that have similar performance that you know of?
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Old 12-07-2012, 05:47 PM
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3,66 small block is a poor mans stroker.With a gen 1 small block you need a standard 350 crank and offset grind the crank throws 60 thou, while turning them down to small journal size. any time you can add stroke to low RPM engines you can keep them efficient. to get a hydraulic flat tappet cam to work almost as well you will probably need 22o degrees at 50 on the intake side and 214-212 exhaust,your lift will likely be 430-440.
110931-11 CL110931-11 267 267 213 213 .450 .450 111 107 Hyd. Hyd.
1100-5200 Strong low & mid-range torque & horsepower.
this is a howards flat tappet as an example
I would wand a little less duration on the exhaust side or a little more on the intake side.
these are just rough numbers to fine tune as you get closer to final decision of the other parts
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