i just started looking as im trying to finish my decision on my setup. i plan on pulling all the rpm i can from my lt1 computer, shift points at 7100. this way i can go with a little more gear, or smaller tire (stock wheels) it just what i want

le3 setup
i understand the cam also decides where the power is made but im looking at these dyno sheets and seeing 383 peak about 6200-6400 go about 5-600 rpm more for a shiftpoint and your right at 7k
i cant seem to find many 355 but id assume they peak around 6600-6800
then they wouldent get their full potential shifting less then 7200-7300?

 

If you put the same cam and heads on a 383 v. a 355 you will see ~the same peak hp and torque but at about 500rpm less. However, the midrange and bottom end torque will be greater with the 383. Properly geared, you won't see much difference in performance. But if you run a little less gear (or a slightly taller tire) with the 383 you will go just as fast and probably faster as the higher geared 355 and put less revs on the motor. OTOH, if you can get enough air to feed the extra cubes of the 383, possibly just with a bigger cam depending on the setup, you will make more power and torque everywhere and definitely go faster.

A buddy has a 5.0 Mustang, He had to rebuild his bottom end last year due to breakage and went from a stock stroke to a 347. He left everything else the same due to budgetary concerns. The car did as described above on the dyno - same peak numbers at a bit lower rpm but considerably more midrange torque. He went to a 1" taller tire and gained a consistent ~0.3 seconds in the quarter mile with his quickest ET going down by a full 0.4! Next year we are doing a cam change to take advantage of the displacement and I expect to see even more gains.

So, in general terms I'd say you should go for the 383.

Rich

 

thanks, was hoping you might chime in, you think it would raise the 383 peak power a hundred or 2 if i went 377?

 

Should raise it about the same as a 355. With the bigger bore their might be some gains in unshrouding the valves...but only if that is currently a problem with your heads.

 

95% of the time people are using ported stock castings. They can only flow so much air.

 

I like the 355. I had over 400 rwtq, and it pulls like crazy to the red line (7000 rpm). I know i can rev it out to 7500, but I have to waite untill the F.A.S.T. is hooked up. I am in the process of doing the install now, I should have results in a couple of months. The weather arround me is turning to crap, so it's time to get to work.

I should see peek power by 7,000, and it should not drop off much till 7500. It might be an advantage to turn it a that few hundred more RPM, but we will see.

It's a tough choice, do what is best for the goals of your set up.
Good Luck!

 

I'm going with a forged 396 (6" rods, hard block to the freeze plugs) for a couple reasons, but here's the one I like:

LOW rpm power.

I already have 4.11's in my Moser 12-botl and the 350 finally lost a head gasket (230,000 miles). This is mostly a daily driver with cruising duty. Yeah, I'll take it to the strip, but the heads that are going on it should make ~420rwhp and do so without having to spin to 7000. With a GM 847 cam, we're looking at a totally streetable set up that peaks around 6200 or lower, so I can safely shift at 6500 at the strip, and not have a total dog cruising around (with 4.11 gears I currently cruise around 1900 rpms or so).

Yes I wanted forged, and the drivetrain / suspension is built for the upgrade, but going with a 396 seemed like a no brainer (forged 383 vs. 396 was ~$200 diff, + $50 for the hard block).

What do I have to do besides pay the $250 extra?
not much... stroker notches in the oil pan...
on yeah, and check the combustion chamber cc's (12.6 SCR, 8.65 DCR).

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Just from a durability aspect it seems like a no brainer.

 

lower rpm means less breakage. no replacement for displacment

 

Unless the heads/intake are really choking off the 383 I'd expect to see significantly more peak torque with the bigger engine. Peak torque is very much tied to engine displacement. A 383 will generally wind up with a nice increase in torque across the RPM scale up until the intake, heads and cam start to shut down the party. A 10% increase in torque in the midrange is pretty noticeable in a street car but it looks like you may be building a track car where driveability doesn't matter. This increase in torque and maybe a little bump in peak HP in a high RPM application like you're considering would have to compensate for an increase in frictional losses from moving the ring pack across the bore another .25". I agree that the 383 might live longer and be a little easier on the valvetrain while delivering similar or slightly better track times.

 

My peak torque was at 5000rpm.
I should be able to break 400 RWTQ by 3500 when I fix the lean spot.

http://www.advancedinduction.com/Dyn...355-RPM-AF.jpg

This is better than most 383/396's.

I think Rick Abare has more torque than I do with his 383.

I guess my point is a good 355 will save you the cost of a crank shaft
(usually about a thousand bucks). Lots of guys on this board pinch every last penny.

Price is what you pay, value is what you get.

 

If you can feed enough air for the 383 to rev it will make more power everywhere. It is all up to the heads and camshaft. I would talk to Loyd if he is doing yours heads and cam and see what he can do for you.

 

Pretty good advice for your first post. Obviously not a "new guy" to the car modding world.