355ci vs 383ci

[NormRinker]

Re: 355ci vs 383ci

Maybe I missed something (I went back and read this thread again) What kind of a boat are you putting this engine in?

It's a Bravo III too you said?

Yes to a BIII. Check out the number 35 post on this thread for the boat specs.

 

[NormRinker]

Re: 355ci vs 383ci

I recently went thru this over the winter. 383 vs 355? My 21' Challenger is very light 2600lbs and did not need the added torque as much as a heavier boat. I am also overpowering the Alpha 1 even though it has HD upper gears. I went the 355 route as I allready had the pistons and rods in the shop.

Eagle 4340 3.480" crank, forged I beams and TRW L2304 forged pistons, rotating assembly balanced very well. 1980-85 4 bolt block align honed, decked .020", bored .030" Melling M55A HO oil pump, Moroso 7qt oil pan w windge tray.

Edelbrock Performer RPM intake
AFR 190cc aluminum heads 74cc 10.0-1 SCR, .039 quench, 2.02I, 1.60E, Flow 261cfm @ .500 with strong midlift flow numbers
Morel Retrofit Roller lifters
224/230 .537/.511 112LSA 110ICL roller cam
Crane 1.6 roller rockers on I, Lunati 1.52 rollers on E
Holley 4150 750CFM carb
Smith Bros .083" wall 1 piece pushrods
Glenwood Marine HP aluminum manifolds w FastGlass 4" stainless smooth long risers that are 16" long. Almost a dry system as water hits the exhaust 3" before it leaves the tips. No Reversion

Engine Made 426hp @ 431tq on the dyno with dyno headers. With the marine exhaust I figure it will make around 400hp. Runs like a dream and very powerful and torquey. Idles 775-800rpm N and 675-700rpm in gear idle. Pulls hard to 5500rpms.

A 350 block needs clearanced as mentioned near the pan rail for the added 3.750" stroke. Does not effect the integrity of the block or cylinder wall in the least. A 6" rod is better than a stock 5.7" rod as the piston stays longer at TDC and resists side loading the cylinder wall. Use the longest rod possible is always the best approach. 383 spec pistons will be needed.
Have the block bored, align honed, decked and clearanced.

As to a 383 running hotter than a 355 I do not buy into this. I've never seen it and i've been around both types.

To do a 383 right your going to be going aways over $3K.

Here are a few pics of the 355

VERY NICE! It is a beautiful engine for sure! That's a pretty serious engine right there. How many running hours will you be happy to get out of it? May I please also ask how much money the dyno test set you back for?

 

[Bondo]

Re: 355ci vs 383ci

To build serious HP,+ Torque,..... There's No replacement for Displacement.......

Usually true, but not always. How about the Formula cars with their little liter engines churning out some very serious numbers? Cubic inches are always good for naturally aspirated applications, but smaller can be as good some times.

I'm Still putting together a 383,.....With a set of Vortec heads at a tight quench,... a Cam in the 214 to 218 range,....Compression ratio around 9.5 to 10:1....With a 4bbl. carb,.......
I'm expecting near or over 300hp.......At Less than 5000rpms......

That's nice you're building a 383. It should make for a good motor. What block, rotating kit, etc. did you go with? I have been reading about the possible locations on water jackets around the oil pan rails area. I should find an old block to hack up and see for myself. Anyway, I've been reading about "Quench". How do you know what Quench it is?

Your example of Formula Cars is Apples,+ Oranges,.......
Those little motors need to Spin Mega RPMs to devolop those kind of HP #s,......
To build HP,+ Torque,.... Down Low in the RPMs,.. aka, Below 5000RPMs,.....
Displacement IS the Key........
Naturally, Or Blown......

My motor is going together with a nodular iron aftermarket Crank,.... PM Chevy 5.7 Rods, Hyper-Pistons(D-Dished to keep the Comp. ratio under 10:1, yet keep the Quench area flat), Vortec Iron heads casting # 906 if I remember right,...
It's all going into a 1968 327 Block,......Which is known as a Large Journal 327,.... Which is the Exact Same Block as the Original 350s.....

The Quench is calculated with the Headgasket Thickness,+ the Block is Decked to bring the pistons Up in the holes to give a Total Clearence of .040.......

 

[SuperNova]

Re: 355ci vs 383ci

SuperNova, 7/16" studs come standard on all AFR SBC heads. I've yet to have a problem. As to the 383 oil temp issue i'm not doubting it, but have never heard it mentioned. I have a few buddies that upgraded from 350's to 383's and 406's and they never mentioned them running hotter oil temp. Maybe due to the use of oil coolers to keep the temp 190-200*.

The bottom threads on the rocker studs always are 7/16", but the upper threads on SBC is usually 3/8". If you opted for the 7/16" studs(would also require rockers designed for 7/16" studs) then kudos for you and you shouldn't have a problem. We found the oil temp issue only during early phase testing when I was coming up with 383 combinations and it is really not a big issue or anything but they do run a little warmer. And don't ever try to run any light oils like 5w30 or lighter, they won't hold up. You'll spin a bearing within 15 minutes of hitting operating temp. But listen guys I have been doing this for a long time and have made many mistakes and have many failed experiments and many successes. I don't talk about things I don't have direct experience with. I won't ever quote from something I read in a book, or saw somewhere, or "happened to a buddy of mine", or heard on another forum. if I haven't "been there, done that" I won't even post.
When it comes to engines, I specialize in SBC, although I am a master Dodge, Jeep,Chrysler and Volvo tech by trade. I have done a couple of Fords, but not near enough to talk intelligently about them.
SBC on the other hand, I've literally done hundreds, and none stock. I've done all the power adders including nitrous, I've done fuel mileage maximizing experiments as well as all out HP, I even did a motor that needed no cooling system. I've played with alcohol and nitro. It all used to be cars and trucks, but marine engines are more challenging, so now I do those. And the retarded thing is I do them for free. You pay for the parts, and I get them at my cost(jobber) with no markup. But you have to build it my way. And no, I'm not taking any new jobs on right now. But the things I could tell you that go against all "common knowledge" would fill a book. The problem with going against what "everybody knows" is everybody is against you. It's like swimming against a very strong current. But I'm not here to change anybody's thinking.
--
Stan

 

[gwaidman]

Re: 355ci vs 383ci

Go with the 355, with the dough you save (vs building a 383), get the rotating assembly properly balanced and then put some gas in the tank so you can run that baby at WOT! SBC are very capable of 300hp with stock heads, mild cam grinds and the such. Choose your components wisely to build power in the RPM range thats required and you will have a dead reliable, pump gas motor that will suit your needs and run a long, long time. Just my 2cents! Good luck with whatever build you choose.

 

[Silvertip]

Re: 355ci vs 383ci

To build serious HP,+ Torque,..... There's No replacement for Displacement.......

Usually true, but not always. How about the Formula cars with their little liter engines churning out some very serious numbers? Cubic inches are always good for naturally aspirated applications, but smaller can be as good some times.
--------------------------------------------------------------------------
Formula 1 engines run at 15000+ RPM and are heavily boosted. However, in a boat you would need to be towed to about 80 MPH before that engine made enough usable power to get on plane. Those cars are also lighter than a jumbo bag of potato chips. A little off-topic but I too feel there is no substitute for cubic inches when it comes to boats.

 

[John_S]

Re: 355ci vs 383ci

At this point, probably just a pocket book decision.

 

[NormRinker]

Re: 355ci vs 383ci

Your example of Formula Cars is Apples,+ Oranges,.......
Those little motors need to Spin Mega RPMs to devolop those kind of HP #s,......
To build HP,+ Torque,.... Down Low in the RPMs,.. aka, Below 5000RPMs,.....
Displacement IS the Key........
Naturally, Or Blown......

Displacement is the key. I guess you would have to be right about that one. I was using the wrong example and logic behind it. I was trying to make the point that even the smaller 350ci powerplant can still make some torque if I don't go the stroker way. Just the right parts and pieces would have to be choosen. Not to say that the 383ci won't make more torque with the same combination. I wonder how much more TQ a 383 will make over a 355 on the same combo?

My motor is going together with a nodular iron aftermarket Crank,.... PM Chevy 5.7 Rods, Hyper-Pistons(D-Dished to keep the Comp. ratio under 10:1, yet keep the Quench area flat), Vortec Iron heads casting # 906 if I remember right,...
It's all going into a 1968 327 Block,......Which is known as a Large Journal 327,.... Which is the Exact Same Block as the Original 350s.....

D-Dished pistons to keep it at 10:1 or under. Interesting. Why not the stock 4 valve relief design pistons? Did you have the block decked significantly and the heads milled decreasing the available cylinder's measurement? I was browsing through the pistons to look at mostly the stock design. Is the D-Dish going to help with the Quench also?

The Quench is calculated with the Headgasket Thickness,+ the Block is Decked to bring the pistons Up in the holes to give a Total Clearence of .040.......

Do you know the stock MerCruiser head gasket thickness? I bought a brand new overhaul set from MerCruiser off Ebay last week at a good price. I don't have the gaskets here yet to break out my new dial caliper and start measuring stuff. Is Quench the distance between piston's top and the flat bottom area of the cylinder head combustion chamber?

Thanks!

 

[NormRinker]

Re: 355ci vs 383ci

Go with the 355, with the dough you save (vs building a 383), get the rotating assembly properly balanced and then put some gas in the tank so you can run that baby at WOT! SBC are very capable of 300hp with stock heads, mild cam grinds and the such. Choose your components wisely to build power in the RPM range thats required and you will have a dead reliable, pump gas motor that will suit your needs and run a long, long time. Just my 2cents! Good luck with whatever build you choose.

It's one of the options I am considering. I would need a slightly hotter camshaft and 4 barrel intake to hit around 300hp which is not too hard to do. I am glad I am dealing with a small block chevy for my boat instead of something that cost more money for parts. It's a much more common powerplant than let's say an older Volvo 4 cylinder engine.

 

[NormRinker]

Re: 355ci vs 383ci

At this point, probably just a pocket book decision.

You said a very good point right there. It is always a pocket book decision. Do I want to spend xx amount of money or xx amount of money. I will probably stay very mild and not go too wild here. I've had to spend a lot of money on many other things too outside of the engine.

I stripped the Bravo III of it's original finish, and I sprayed on some epoxy primer to prime and seal it. As of right now, it is sitting on my homemade wooden stand waiting to get wetsanded for the Imron black to be shot on next. I got new propellors in the 26 pitch size (stock) last year for it, and the fresh paint with all new hardware for it this year. Hardware like the prop nuts, thrust bearings, anodes, etc. I bought the drive seal kits, however it checked out fine with the pressure test. The u joints are greased, so it is basically ready to go when painted.

I also had to buy new (all MerCruiser/Quicksilver stuff) impeller kit, circulating water pump, U joint bellows, shift cable kit, shift cable bellow, exhaust tube, both hydraulic tilt and trim hoses, trim and tilt sensors, all exhaust rubber connectors, exhaust flappers, exhaust gaskets, some clamps, carburetor rebuilt, pullies, belt, second battery and box, dual battery switch, wires, and that's on top of many other stuff I am forgetting too. I may want to buy the Y pipe to transom O-ring seal to be safe rather than to find out later it leak water, and to do that while the engine is already out seeing how easy it is. It could have also been burnt on that overheated run back to the dock like how almost all the parts did that I listed above. Then to cap it all off, now I have the engine deal to shift my attention to.

Thanks

PS: I forgot all the tools I also had to buy to do the job properly. Hinge pin, alignment, tapered water hose insert, shift adjustment, anchor plate, etc. tools..

 

[John_S]

Re: 355ci vs 383ci

Norm,

All I meant was the cost vs value of the performance increase. Only you can say what you are willing to pay for what level of performance. The rest of us, can build you whatever motor you want, spending your $.

If it was me, and the rest of the boat is in excellent shape, and I was going to keep the boat for some time, would lean toward the 383. You have the drive to take the torque, and you won't ask "why didn't I do that", a year down the road. Good luck with your choice.

 

[Ryan00TJ]

Re: 355ci vs 383ci

VERY NICE! It is a beautiful engine for sure! That's a pretty serious engine right there. How many running hours will you be happy to get out of it? May I please also ask how much money the dyno test set you back for?

Thanks. I built it over the winter and had alot of time to make it good looking. I don't feel as if it will be any less reliable than a stock Merc 350. It has much better forged componets and is balanced very well. I am also using a FluidDamper harmonic balancer to help with vibrations. Max RPM has been 5500. My original stock Merc 260hp 5.7L went 850hours when I pulled it. It burned no oil and had great compression on all cyls. It just was not fast enough. I always compression check and leakdown the engine every fall to compare the numbers to when new. This is motor #5 for the Challenger. All but the original have been modded and over 350hp. All have lasted 600+ hours save for one. It was a solid lifter 257/269 cam, AFR heads, Vic Jr setup that saw 6500rpms with a 21p labbed cleaver. The .010" under Forged GM crank let go and cracked in half. Luckily it stayed in place and all it took out was the crank and bearings.

I have a buddy that hooked me up with a good deal for the dyno. $250 plus I got him some trees for his yard. Full price your going to be looking at least $500.

I've been around boats for awhile and I recommend going the 383 route for your boat. The initial added cost will pay off tenfold after it's all said and done. The added torque will be needed for the heavier boat. Small 19-22' boats that are light can get away with the 355's, but for a heavier boat get as much cubic inches as your dollar $ can support. My $.02

SuperNova, Studs are 7/16" as are the rockers. I've had no problems with them and the old solid lifter saw 6500rpms. No stud girdle either.

 

[SuperNova]

Re: 355ci vs 383ci

Good deal Ryan. If you break those you've got something else going on.

I also recommend doing a 383, just not for $3000. If you're going to do it you have to do it right. And that costs a little extra.
--
Stan