Why not 400 ci???

[CDMA]

This storker and destroker talk got me wondering. Why don't people just do a 406 opposed to a 383. I know the blocks are harder to find but you can find them and in reality they cost only a few more $$$ to build then a nice 383.

What I am really getting at is there really any problems with the 400 block. You hear from time to time about cooling problems or head gasket sealing problems and I was wondering how many of you have actually had any experience or in depth knowledge of these blocks and how they work in and out of a marine environment.

Basically cost aside would you rather have a stroker 350 or a 406. Assume internals are the same. Aka Eagle or scat type rotating assembly with 5.7 rods and aftermarket iron heads.

Chris

[Voodoocanoe]

I'd go with a 6" rod 383, The 400's are a good engine also but they are a siamese block with steam holes between the cylinders and have a limited overbore capacity, cast cranks only and the early 70-72 had 4 bolt main caps where the later ones had 4 bolt blocks but 2 bolt caps on them and were externally balanced also just about every 400 that I have disassembled had cracked cylinder heads mostly due to the fact they were lightweight castings but you can put any small block heads on a 400 by simply using a 400 head gasket for a template to drill the steam holes in non 400 heads.

[CDMA]

Lee,

I have sent you a couple e mails last week about the pictures you sent me. Did you get them?

I have heard what you say about the 400 but if it is an all new rotating assembly and new cylinder heads two of the main problems go out the window. Basically lets say I was looking to build a stroker motor and I had these two options:

383 - Scat internals, 6 inch rods, dart heads
406 - Scat internals, 6 inch rods, dart heads

For the same price why not go to the 400?

This is of course hypothet wink wink ical

[AVickers]

As long as you NEVER want to bore over .030", the 400 block is killer -- even w/ a stock Chevy bottom end. Just be sure to get a really good set of pistons and heads. Because of the Siamese cylinders, it's a lot stiffer than a 4" block... (Just be absolutely sure to use the correct balancer and flywheel!)

As for two- vs. four-bolt mains, use studs. They really add strength over bolts. You could also use a girdle. Or, if you were really serious, you could get four-bolt main caps and have the block drilled, tapped and then line bored (the bolts could even be "splayed"). All-in-all, studs would add the most strengh for the least $$$$.

(Four-bolt mains are really a high-rev/high-load solution for "crankshaft whip" induced by high performance automotive or truck loads -- stiff drivelines, dumping the clutch, banging gears up and down, etc. Given the types of loads seen in outdrive/marine applications, the only thing close is when a prop leaves the water at WOT. The difference here is that by the time it reenters the wet stuff, the rev limiter has kicked in and this softens the hit. As for really high Rs, we typically don't use anywhere near the potential revs available in SBC engines with our wet exhausts and outdrives -- the CanAm engine I referred to in another discussion made 450 HP at 7300 RPM and 375 ft/lbs of torque between 5300 and 5800 Rs.)

Our rigs never see this kind of stress.

[Formula Jr]

Most of this conversation is about 10,000 feet over my head; but, if I'm reading between the lines correctly, say you that a four bolt main isn't really useful in a marine application?

[RickSE]

I run a SBC 400 in my drag car. The stories about 400's easially overheating is crap. I know since I drove this car on the street for three years in Phoenix. The weak point of the 400 is the factory 400 rod. The rod bolts on the big end were shortened in order to clear the cam. Therefor the stock 400 rods have a lot less meat in the big ends and are not desirable for big H.P. The easiest solution is to use 350 rods, then check and grind the rod bolts as needed for cam clearance. I used stock 350 rods with ARP bolts and did not have any clearance problems in my motor.

My 400 makes 425-450 H.P. with a lot of non-exotic parts. I built the motor 15 years ago and it still runs strong. Last September the car ran 12.30 @ 1300' elevation, in 105 degree heat, with the motor turning 6500 RPM's.

The motor was built as follows in 1986:
Factory 400 2-bolt main block, last production run for 400, motor never made it into a car/truck.
Factory Cast Crank.
350 Rods.
TRW Forged Pistons, 11.5:1 with 64cc heads.
GM Bowtie Angle Plug Heads, straight out of the box, no port work.
Edelbrock Victor-Jr Bowtie Intake, port matched to heads.
Holley 4150 750cfm Carb.
Comp Hyd. Cam, 292 Duration, 501 Lift.
Rhoades Lifters.
Mallory Unilite Distributor, 12 deg initial adv., 38 deg total.

I love 400's and would never waste a 400 crank to build a 383. Several months ago I posted a really god write up on building a sleeper 400, 509 H.P. from a flat-topped, cast crank motor. If anyone is interested I will re-post the article.

[BigGrizzly]

What Rick says is correct. Chris as you know, anything can happen. I dropped a very expensive valve in my engine, for no reason. This is the first broken valve in one of my motors in over 25 years. If you overheat an engine anything can happen. According to Robin Vivian a GM engineer, the 400 was a truck block and had a limited existence because of the 454. In an earlier post I mentioned the 377 Scorpion engine. The point wasn't the destroke but the engine durability. The fact is Merc is building a 400 stroke with a 350 type block. with 5.7" rods. This combo has been run for over 20 years. Mods had to be made to the 350 blocks for clearance reasons. The 400 aren’t used because on the open market the 350 is most readily available. When I lived in Jersey the 400 marineized engine was commonplace in Garvys

Randy

[CDMA]

Scott,

I agree with what you said about those engines not being suitable for marine use but all things being equal if you speced a 400 as a marine motor wouldn't it put out more power then a comparable 383 just by virture of the cubic inches?

Chris

Despite my wishes realizing I can't even afford stock....ok back to the 22

[AVickers]

My point wasn't that a 302 would be a good boat motor (unless it was an overdrive, crashbox V-drive flatbottom w/ 18k prop Rs...). My point is that SBCs really make a lot of horsepower above 6500 RPM and at these speeds, four-bolt mains are a benefit. At the speeds we typically run boat motors, a two-bolt block will hold up virtually forever... (I'd predict that we've not lost many (or even any) engines due to a lower end failure that didn't also involve oiling problems, dropped valves or water in the cylinders...)

My point is that any well built small block would perform well and that of the group of SBCs out there, a 400 2-bolt engine would be a good and inexpensive choice for a low compression (regular fuel), big volume boat motor that could be built to make maximum torque in the 4500 to 5300 rev range -- especially given that this is the rather "limited" RPM at which we run outdrives.

In terms of reasonableness of costs, the "next step" for a normally aspirated engine would seem to be to go w/ even more cubes and an even longer stroke -- like a 454 big block -- and save the money you'd spend on exotic small block hardware for something else.

Ideal boat under this general rule: Rick R's old 18 w/ the Rat and the Cobra. (A little bottom-heavy, but god, that must have been one hell of a ride!)

[GEOO]

Chris,
I think most 383 were built because people think they are less costly then a 400. This is true if; you have a 350 and just change the crank and short rods. The base 383 is more economical to build; however if you want to build a nice 383 then you end up changing to longer rods and higher wrist pin type pistons. So if you end up changing the whole rotating assembly, then the block is the only extra cost in building a 400.
Remember the old saying " there is no substitution for cubic inches" (aside from forced induction) (I don't think that is the correct saying???). Well anyway that's true.
The 400 will build more usable power then the 383. Just my thoughts.
the extra 23ci must be a good thing.
I do know that by adding 51ci (by adding stroke & bore) to a 383 makes a big differance.
Chris, just think if you added a blower to a 400+ inch motor. You could be making close to 670 ftlbs. eek!

One other thought, maybe Ted and Randy can shine some light on this. I have always been told that marine engines need to have low end torque to get the boat on plan. (I agree) That is true, however 18 and 22 foot boats may only need 100ftlbs to plan off. I ran a 383 with small port heads then with large ported heads. The larger port give less low end power, less intake charge velocity, but added 3-4 mph top end. I didn't really notice any lack in low end power.

When I had my 434 built I put a big cam in, she can build power up to 6500-7000. I prop her for 5800-6000rpm. Max torque is at 4900. It's a big differance. She pulls at 4500 like the old motor jumped at 3000rmps.
My 383 was cammed with max torque at cruise speed 3500-4000. Once you got over 3800 the torque started to fall off. The boat would accelerate slower after 4000rpm's.
I think our small boats like big cams and big heads higher rpm motors.
Is it bad to build a motor that can rev 6500 and prop it to run 5500?? That way it builds the torque higher up in the rpm's?? GEOO

[Forrest]

Chris, I think that it all comes down to is how much money and effort is that extra 23 cubic-inches worth. I'm sure that you can build a 400 that will run just fine in your 18, but so will a 383 for dollars less.

A friend of mine who is a long time race engine builder built both a 400 and a 383 small-block with the same cam, heads, exhaust, etc. The first season the 400 was run in Kim Hermann's X-18 with a Volvo 280T in Norfolk, VA, and it ran quite well. The second season the 400 was removed and the 383 was installed. Kim said that they both ran neck-and-neck on the top end, but for some reason he actually thought that the 383 was a smoother running engine than the 400, and went on to say that he just liked it better than the 400. I'm not sure of the rod length in the 400, but it may have had the stock 5.565" rods. I do know the 383 that he presently runs has 5.7" rods.

As for 6" rods, what are the trade-offs vs. benefits? The longer rod increases piston dwell at TDC which may help to reduce detonation with low-octane fuel, but with a 6-inch rod, the wrist-pin is located in the oil-control ring-land. I'm really not sure if that a good thing or not for engine longevity. Also, off-the-shelf pistons for 6" rods are generally available only with 1/16" ring lands which helps sealing at very high RPMs, where as 5.7" pistons are available everywhere with wider 5/64" ring lands. The wide rings dissipate heat better to the cylinder walls than do the thin rings.

[RickSE]

Actually a 400 with beefed up factory 400 rods would make a nice marine motor, below 5000 RPM's. The key is to install good rod bolts and stress relieve the rods. I may do this one day since I still have my new 400 rods.

Short rods create more torque but put heavy side loads on the piston skirts and cylinder walls. Short rod motors are usually low RPM torque motors.

Long rods create less torque but lower piston and cylinder wall side loads. These motors are usually higer RPM horsepower motors.

[Jabes]

I have a 383 stroker in my '85 22 classic, this engine is incredibly smooth from idle all the way up to top end. I don't know much about the 400, but the 383 runs great! fires up every time with less than one full turn of the engine. If I blew this one up, I would put the same motor right back in.

[BigGrizzly]

As you can see the 400 has been used alot. In the realworld te short rods 5.7 rods will work fine since that is what is in the 383 and it does fine. Would I do it would depend on the boat and which one I have. Either will work if camed correctly. Its the total combination that counts.

Randy