articfriends

iTrader: (1)

Chris,ive used both heads and wasn't aware of a better chamber design between the two castings,its identical as far as ive seen. I agree with robyw1,especially keeping in mind this guy is going to use a cam that peaks at 5200(on a 350) and will probably peak at 4800-5000 on this larger motor (especially with stock exhaust).keep in mind He's not trying to turn 6000 rpm's either and says he cruises at 3500 for the most part too,Smitty

cstraub69@comcast

Smitty,
Sorry, I was think S/R torquers. . .chambers are the same. I still feel with what I have seen and dyno'd that the 200's will be just fine on 383 CID even with the low rpm. The smaller head will take more cam to make power over the curve. Use the larger head, shorter cam duration, moderate lift, and you will build velocity.

Chris

Formula78

I'll provide some limited input here. I have nearly the identical setup.

383 Eagle crank, 6" scat h-beam rods and SRP dish pistons. 9.0:1 cr w/ a 72cc head. I am running the XM-270-HR cam (0.495int 0.503exh, 218 lsa). Perfromer RPM intake, with 180cc World Products Sportsman II heads. Center rise manifolds, 4" risers and through-hull exhaust) I can only provide limited feedback as to how it ran because it only did that for 2 hours before it came apart.

I never had a great hole shot because the carb (Holley 650 vac seconadaries) was directly out of the box and NOT tuned at all. Mid-range was like a rocket! The 20' Formula it was in would easily flirt with 65 with 2 people, a full cooler, and a full tank of fuel.

I am extremely happy with the Sportsman II's. If I remember correctly I paid $257/ ea from Summit Racing with free shipping.

traviss

I run the 210 cc AFR's on my 383. A little pricey but worth it. Spin it 6000-6200 rpm on a ......alpha drive No problems yet

Liberator21

This is great guys!
So the debate rages between 180 and 200cc heads.
If you need any more info about the engine let me know.
I've got time, I won't be doing this till the off season.
Like I asked before, What about going to 1.6 rockers with the head change?

rmbuilder

Formula 78
If you have Sportman II heads they have 200cc intake runners, they do not make a 180.
The intake port dimension is 2.050" x 1.240"
Bob

pullmytrigger

arctic and 69 - whats the most hours you have seen on a marine 383?or 400 based engine?

articfriends

iTrader: (1)

Twin 29,i don't have any personnel experience with a 383 or 400 in a boat but i have built both for street and strip motors,mud boggers & circle track. They will last just as long as any other small block,just a few things you don't want to do that i'm going to list (you might already know these but i'll throw them ought there for you or anyone else that it may help).
1. Never use the stock 400 rods (they are too short which gives you a less than ideal rod to crank angle, causing high stress over 5500 rpm's)
2.Don't jump thru hoops to find a stock 4 bolt 400 block(they only made them in 1970 anyways),the 2nd set of main cap bolts weaken the main bearing webbing,(you can actually see where the bolts protrude thru casting),if your building stock 400 block arp studs on a 2 bolt block are fine or splayed caps if your going to buzz it to the moon(or aftermarket block)
3. DO NOT bore stock 400 block past 40 thous MAX,Cylinders are already too thin,can crack easily, run too hot and you get crappy ring seal due to cylinder distortion.
4.Eagle makes a ok 3.75 stroke crank with 350 chevy main journal diameter for guys who want to build 383 without searching for hard to find 400 crank + the associated work on the mains to get it to fit.
5. Always drill the steam riser holes in your heads if running a stock 400 block,you should clean the riser holes in the block with a drill bit that just fits to prevent debris or corrosion from plugging them in a marine application.
6. You will be balancing any stroker combination you build anyways,you should have it zero balanced so you can reuse your original 350 flywheel (if replacing a 350). If you choose to use the external off-balance a 400 crank has built into it you will have to find a 400 only flywheel (harder and more exspensive to find).
Most you guys out there know all this anyways but i posted it for some of the guys who might not to help them avoid unforseen problems,Smitty

pullmytrigger

Arctic- do you prefer one over the other (383 or 400) I would be super happy with 400hp

what about a 350?

I have a pair of stock 350s in my boat and will hop them up one day

pullmytrigger

this boat...........