I'm looking at two motors with almost the exact same components, save for the bigger crank. Given the same cam in the two, how much of a power difference would we feasibly be talking about. I'm on the fence about which motor to go with right now.

The setups are both with Eagle ESP 4340 Forged Crank and H-Beam rods, and Diamond Ultra-Lite dished pistons, 11.0 compression ratio. I'd be going custom cam, which I KNOW would come into play here due to the difference in engine size.

Basically, I'm just curious on how much of a difference there would be with the same cam, and thoughts of how much difference "could" be seen with a custom cam for each motor.

Any takers??

 

Well, I say with the same cam the powerband on the 383 would be lower than the 355, but power would still be somewhat larger on the 383 regardless of peak hp rpms, even though lift #s will still be the same the 383 will still suck more air. You could have a high winding 355 and a street 383 or a street 355 and a starved 383...

As for custom cams, if the cam lift #s are proportional to engine displacement (as in cam lift for 383 is equal to cam lift for 355 multiplied by the ratio- 383/355) the powerband rpms should be fairly close to equal but I would say the 383 would start pulling a lot higher numbers on top.

 

That's what I was thinking too, unless the stock ported LT1 castings would choke the 383 off.

Still curious as to a number though.

 

(im assuming the lt1 is a 350 motor) why would anyone wanna go from a 350 to a 355? sounds like lots of money and work for nothing
Edit:: i have no idea what it costs to upgrade by the benifits seem to small to spend maybe $500 to gain 5 inches of cubic displacement. thats like a 2% power gain... and that of hp is probably near 10-20 horsepower... seems somewhat worthless, but definatly off subject

 

Budget. I'm on a tight one, and a 355 is more ecinomical. Granted it's only about an $800 difference, but that could be all the difference in the world.

Back to the TOPIC, anyone have any guesstimates at numbers differences.

 

Yeah, the stock castings will most likely choke it off, but a big beefy cam with some good lift #s would compensate some. Don't really have any good #s to toss at you, though.

BTW, a 355 is more of a freshen up job on the shortblock. Basically you can install all the aftermarket valvetrain parts you need with ease and put in new bearings to make sure your engine is ready for more power. All you'll need extra is some new pistons... A 383 is more expensive because to really do it right you're gonna need new internals and some ported heads, new valvetrain to make it work right. A 355 might not sound worth it when hauling out the engine, but it's much cheaper than a 383 setup, so those without fat wallets can't always do 383.

 

Some of the HP will depend on what compression ratio you're wanting to run...

 

I was debating the same thing and stayed with the 355. There are alot of 383's out there that are turds, plain and simple. Why? Because people don't put big enough cams/heads/TB's on them. a 383 needs so much more air than a 350 does. Unless you are going to get a set of really good flowing heads and a cam to match, IMO i'd stick with the 355. Also, the 383 needs to be internally balanced, for the best/cheapest balance job, some have to modify their oil pans. Yes you are going to get more tourqe from the 383, but not the hp. I personally think that the 355 that I am building would walk a 383 with the same parts because they are better suited for the 355. However if I would have stepped up everything else AND went with the 383, thats a different story. Cubic inches alone isn't going to make power.

Just my .02

Jason

 

Dont understand why you need to ask this question? If you dont have the cam, and you are going custom....why do you need to know the power difference?

Just tell the cam grinder when you know 355 or 383, no sense spending 300+ on a cam that you dont know what its going into.

 

I reread the original post again, I skip over stuff to fast when I want to reply fast . The deciding factor is going to be what type heads you are going to put on it and what they flow.

 

The heads are stock ported early castings flowing 272/210@.550. Going to get them completely flowed.

The reason I was asking was because if I can pick up 20-40 HP by going to the 383 custom cam setup instead of the 355 custom cam setup, then I'd probably do that.

 

Oh..i see, you made it sound like you would use the same cam on either CI engine no matter what.

If you are getting custom for both no matter what, you just have to decide whether the $600 is worth the much extra torque, and maybe 20hp depending on how well the cam works with the heads and bottom.

One other thing...more importantly than the flow numbers...who ported them? If no one we would know, are they a reputable race head porter that knows how to port heads?

 

Well brother trust me when I say this as I have just went through that. It's way more than an 800 buck diff. Excluding the machine work itself on the block, your still looking at injectors, programming, head work and all the other lil things to accomodate the stroker. It winded up costing me way more than I figured. But I don't regret it all .....YET anyway.

 

Ok, the heads were done by Joe Prince, and just ask around. The guy knows his stuff when it comes to heads. He's got 12SCNDZ moving at a 12.0@114 or something like that, with a CC305. His heads put out the best flow numbers I've seen so far, mid lift numbers especially. I have no doubts about my heads.

As for the motors, there's going to be NO extraneous expenses needed other than the shortblock. I already have SVO 30# injectors which will work fine with tuning. The entire top and front of the motor is all brand new as of last summer, with less than 1000 miles on everything, so it's all getting swapped over. The ONLY thing that I need to get moving is a new shortblock, oil pump and drive, and pan if I go 383. Having priced it out, I'm looking at $2800 for the 355, or $3400 + pan for the 383. I just can't figure out if the 383 is really worth it in the larger scope of things. I need to talk to whoever is going to do my cam and get some thoughts from them I guess.

 

Who says you NEED a new pan? Plenty of people use a stock pan on 383s. Just with some banging and stuff.