383 Combination

I'm looking for that winning combination of parts to build a SB Chevy 383 Stroker with @450 HP. Any ideas on crank, cam, pistons, heads, intake, carb, etc. (all the goodies) The engine is going into an 84 Camaro.
Thanks


Register now (free) or login to remove ads

http://www.cnc-motorsports.com/prod...7000&CtgID=9036 - bottom end.

I was just going through lists of heads from different manufacturers this afternoon and found a set of heads from Racing Head Service that look promising for a street motor. I just ran a DynoSim on a 355 a little while ago with these heads that can be seen on the wiki at "DynoSim combinations".

Let's use these same heads to build a 383 and see what happens. They're called Pro Torquer Vortec and are drilled for either conventional or Vortec intake manifolds. Intake runners are 170cc's, chambers are 64cc's. Now, I don't know how real the flow numbers are from RHS, but if they're anywhere close to what's published, these will make some dandy street heads. Here are the flow figures they claim for these heads...
.100 77 74
.200 155 140
.300 220 168
.400 263 172
.500 270 174
Now, if these look bogus to you, don't carp to me. I'm just passing on information that they publish. In my opinion, even if they only flow 90% of that, they are a damned fine set of cast iron heads.

Let's start off with a Scat cast steel 3.750" crank and Scat I-beam capscrew 5.7" rods. We'll hang Keith Black hypereutectic part #KB135 pistons on the rods. These 18cc D-cup units will make 9.7:1 static compression ratio with the 64cc heads. We'll use a short cam to make tons of torque and coordinate the intake closing point of 39 degrees ABDC with the 9.7:1 static compression ratio to generate a 8.38:1 dynamic compression ratio that will support pump gas, particularly if you use a tight 0.035" to 0.045" squish. It might even run on 87 octane swill. I might even be tempted to tighten the squish to 0.030" and see if I could get away with runnin' 87.

I know I sound like a broken record with the rest of the build, but this stuff works every time. RPM intake, 750 carb, 1 3/4" long tube, equal length headers.

Here's the cam we're gonna use. We're gonna install it straight up (not advanced, not retarded) and we're gonna use 1.6 rockers on both intake and exhaust. New lift will be 0.484" on both valves.
http://www.compcams.com/Cam_Specs/C...px?csid=73&sb=0
RPM HP TQ
2000 158 414
2500 200 421
3000 258 451
3500 321 481
4000 378 496
4500 429 500
5000 468 492
5500 482 460
6000 464 406

I'll just say that if those heads even flow 90% of what they advertise, it would surprise me, sounds like more of the same old same old as if it were the pro comp deal all over again.

I began paying some attention to this several years ago when I began studying dyno pulls and noting the components used to reach certain power levels.

You're absolutely correct, the norm has been 1 5/8" primaries for years and years. But I began seeing 1 3/4" and even 1 7/8" primaries on small blocks. I thought back to my youth and remembered that we used to use 1 5/8" headers on the early 265's. Then we went to 283's and used 1 5/8". Then to 302's and used 1 5/8". Then to 327's and used 1 5/8". Then to 350's and used 1 5/8". Then we went to 400's and used 1 5/8". Does anyone see anything wrong with this picture?

A 400CFM carb might have been all that a 265 could use, but you certainly wouldn't build a 406 today and bolt a 400 on it and expect it to make power. Why would you expect to use the same volume pipe on this 406 that you did on the 265 and expect it to make good power.

A 30-30 Duntov cam made good power in a 265 in 1956, but I don't think anyone in his right mind would expect to use that cam in a 406 today to make good power.

These small block Chevies have grown in size from 265 to 400 and we're still using the same volume of pipe to carry away the exhaust gases. The motors are half again as big as they originally were, but here we are, still using the same volume pipe. Does anyone see anything wrong with this picture?

Take a look at the 396 Chevy. Smaller than the 400 small block, but the pipe diameters start.....START.....at 2 inches. This should be a clue to all of us that we're choking our small blocks down because we just haven't taken the time to reason out what we actually need in the way of pipe size. I've done hundreds of DynoSims in the past 6 months and in every...EVERY case, I have seen more power produced with pipe sizes larger than the ones "normally" used by us hot rodders. Not only on small block Chevies, but motors of every make, size and description. And the gain in horsepower and torque has not been only on one end of the rpm scale or the other, but all the way through the range.

I did a little math on this if you'll bear with me. If we use a pipe length of 30" as a standard and figure the volume (cc's)of some different pipe sizes, they look like this....

1 1/2 869 cc's
1 5/8 1019 cc's
1 3/4 1182 cc's
1 7/8 1357 cc's
2...... 1544 cc's
2 1/8 1743 cc's
2 1/4 1955 cc's

Now, let's look at some cylinder volumes....
265 543 cc's
283 580 cc's
302 619 cc's
327 670 cc's
350 717 cc's
383 785 cc's
396 811 cc's (big block)
400 819 cc's
434 889 cc's

Now, if we look at the 265 at 543 cc's and use the 1 5/8 pipe at 1019 cc's, we see that the swept volume of the cylinder times 1.875 = the pipe volume. If we look at the 396 at 811 cc's and use the 2" pipe at 1544 cc's, we see that the swept volume of the cylinder times 1.905 = the pipe volume.

From this, we might deduce that swept volume times somewhere around 1.8 or 1.9 should give you the volume of the pipe you should use to make max power on that motor.

Using a 350 with 717 cc's and multiplying it times 1.80 will give you 1290 cc's. Looking at the pipe chart, we see a 1 3/4 pipe at 1182 and a 1 7/8 pipe at 1357, so if you go conservative and drop down to the lower pipe, you'd be bolting 1 3/4 pipes to your 350.

Using a 383 with 785 cc's and multiplying it times 1.80 will give you 1413 cc's. Looking at the pipe chart, we see that a 1 7/8 pipe is the closest match.

Now, I know most of you will dispatch this exercise as just so much hogwash....and that's fine. But I may have planted a seed in the minds of some.... and that's fine too.

Well, all I can say is that if you do find a set of heads that flow at the figures I posted, the motor would make the power I posted.

Remember, too- there were a lot of 1-1/2" headers used on the 265, 283 and 327.

Nah. Headman Super Comp headers vary between, 1-7/8" and 2-1/8" for headers that fit passenger cars. These are for 396 to 502 ci engines.

If 1-3/4" is just right for a 350, this means a 502 BBC daily driver should have 2-1/2" headers. A 400 SBC would need 2" headers. Sometimes a direct correlation can't be accurately made.

Then there's the sticky wicket involving companies who actually make the heads, engines and engine packages, you know the names. You know what they recommend, and they're not about to hold anything back that'll sell more parts or make more power, just because "that's what that used to do".

If there was more power UNDER THE CURVE, people would be using 1-3/4" headers on their 355's. Fact is, except for the LS-type engines, this has not proven to be the case, except on simulation software.

Alrighty then.

I respect your opinion, and if you feel the bigger headers get you where you want to be, I say do it!

FWIW, I'm planning to use stepped headers on the 383 I have going together. Best of both worlds, if there is such a thing.

When I use stepped headers on the DynoSim, the power goes nuts. I don't even post the results on here because nobody would believe it anyway.

hey guys, I think i got what your looking for, just scroll around, its 350 and 383 builds mixed together and im sure youll find something you like... I DID !! i have used a few of these combos before and they work very well, I really like it cause it gives the heads, cam, intake and exhaust runner sizes and all the good stuff.. check it out. let me know what you think.... http://www.ryanscarpage.50megs.com/combos1.html

I think that has been posted here about fifty times, but thanks just the same. Maybe someone hasn't seen it yet.

Now, if it showed the header size they used...

Go here and click on dyno on the top bar, then click on Chevy...You'll see some different sizes used....
http://www.airflowresearch.com/store/