Whitey

I have the oppertunity to by a pair of 400 sbcs. Would these make good marine engines? They would need to be reworked. Thanks Dwight

rws

iTrader: (3)

I have been running these for years. Use a 5.7" rod with a J&E SRP Reverse dome piston. A stock crank will work with a hydraulic flat tappet cam.5000 or so rpm max on a stock crank ,Balanced rotating decision, 200cc intake runner Dart Pro 1 cylinder heads are what I have on my Boat.

Rob

olysan

I built one a few years ago (with a lot of help from this board), and love it. I'm running the vortec heads, and an edelbrock "Performer RPM" intake, with the Comp Cams Extreme Marine 262 cam. Makes a nice combo. I'm also using 5.7" rods.

robyw1

Well it will make a better marine engine than a racecar engine because in this environment it can be properly cooled. In a car they were known for cooling problems unless money was spent for a sufficient radiator. However let me share some of the problems I had with a couple of mine. First off in a marine configuration I would keep the RPMs fewer than 5200. I ran up past 6500 in mine and broke 2 cranks. You see finding steel cranks for this engine was very hard and expensive. Another very important parts of this engine were the rods. The stock rods in the SB-400 were weak and too short. If you were to stick with these rods in a sustained high RPM engine then it would surely kick one out the pan, and if it did last it would force the piston to rock too much wearing it and the cylinder bore out. You would definitely need 5.7” rods and that would involve purchasing pistons with a higher wrist pin location. The fact that it had to have a higher wrist pin in it self made for a weaker piston. Also because of the siamesed bores you really shouldn’t go beyond .030 oversize. Whatever high performance heads you purchased would have to have the ”steam holes” drilled into them. Another issue was that good main caps were hard to find. Modifying a SBC 400 was always much more expensive than a 350 because all of the OEM components were weak. There was never really a high performance 400 built from the factory. They came on at a time when smog concerns were just beginning and it was intended mainly as a torque motor to run with the lower fuel grades. I have to say with the ones I owned in my old Monza that I don’t like them. It took way too much dough to get them to run fast and hold together. I would say buy it if the stock bore size were intact and it were 4-bolt mains. Be sure to check for excessive taper in the bores as they were known for this wear. Unless you just have to have a small block and are prepared for some high $$$ modifications, I would just look for a 454 or 502

Just my 2 cents worth.

Roby

Dennis Moore

Excellent marine engines if you don't get carried away with mods. I have built a few 383 and 400 marine engines with the 400 rods and they worked fine. Use good rod bolts though.
I wouldn't worry about the rod to stroke ratio at all. The more I learn about engines the more I am convinced that the length of the rods doesn't matter much. I have heard many good engine builders say that they used to believe it was really important. Now, most of them think it is a waste of time to build an engine with the "so called" best ratios. Many believe that the rod simply connects the crank to the piston and nothing else!
One thing is for sure, those big main bearing journals are nice! Use the two bolt main bearing blocks, they are a little beefier.
Don't use the heads that are the lightweight castings (most 400 heads are lightweight castings). Make sure the block decks and the heads are flat and use good head gaskets. Have fun!
Sincerely
Dennis Moore

olysan

FYI - I didn't see any difference in $$$ for parts for my 406 vs 350 parts. I did pay extra to get the vortecs drilled for the steam holes, (and make sure you get the felpro marine head gasket with the steam holes), but it was only $25.

Shah Mat

I think that the 400 is an awesome small block and can be cost effective up to 400hp. As many have already said, it's going past that point is when it gets expensive. My dad took a 400 out of a wagon with 66k on it and bolted on dart heads, a hyd cam, single plane intake, and a Holley 750 and stuck it along with a turbo 400 and a 11" converter in his CJ7. Want to talk about a wild ride!!!!! We took it to an 1/8 mile track and it ripped off a 7.97 ET on 33" all terrain tires! The only reason he chose a single plane intake is to stop it from boiling the tires! Got to love the torque of a 400. That Jeep was so much fun next to Corvettes and such at stop lights.

I think they are an excellent choice for a marine application as long as you don't go wild.

Offshore Addiction

400 will only work in freshwater applications!the steamports will plug up w/saltwater applications......

robyw1

Very good point. i forgot all about that

Roby

Iggy

Couldn't the steam holes be opend up to a larger size?