Long Rod 302?

[busterrm]

I watch another forum, and the question came up about building a SBC 302, using a longer rod than stock. Several are convinced that 6.25 in rod would be good, also 6 in and 5.94 were mentioned. I did some easy math and suggested 5.85 in rod with a 327 piston. There was no mention of it being a street engine or a racing engine. Through the years, I have known many engine builders and most of them have told me that anything longer than 5.85 rod(in a small CID engine) is a waste unless it's going to be a all out race engine. Each stated that the longer dwell time of the longer rods would necessitate the use of more radical cam with a overlap of 70 or more degrees. In addition to the more radical cam you would need larger port heads to supply the flow of the more radical cam. I got a ration of shit from everybody about my suggestion. I was thinking of a street engine and the ability to buy off the shelf parts for the build. The budget wasn't mentioned either, so I thought a set of hyper pistons and a set of rods from Ohio Crankshafts would be good with the price at about $590. I just don't understand I was just offering opinion and another option. GEES!!!! I realize the piston would be heavier, but Mahle makes a set of pistons without skirts that is lighter and are forged, cost would be a few hundred dollars more. Just scratching my head! Is my thinking wrong on this guys? With the other options either machining of the pistons, decking the block, or having special pistons made would be needed.

 

[Grumpy]

Smokey YUNICK, did a great deal of research on this on G.M.s DIME, and the advantages of the longer rod length IS a proven factor but the other components MUST match to take full advantage of the longer dwel time as the other sources mentioned, if you don,t use a cam with enough duration, an exhaust designed to effectivekly scavenge the cylinders in the intended rpm & intended power band and use an intake runner length and port cross sectional area that maximized the cylinder scavenging you LOSE most of the available volumetric efficiency in that power band & rpm range and thats generally less than about 2500 rpm wide.
Ive built several 302 and 327 engines with 6" connecting rods, in the past, that ran very well once you used about 12:1 compression, and solid lifter flat tappet cams similar to the crane 110921

both engines used ported dual plane intakes and 750 cfm holley carbs you can play with the camquest, or DESK TOP dyno software and find youll have zero issues exceeding 500 hp with a similar combo provided really good cylinder heads and matched components are used
http://www.camquest.com/
DD2000

http://garage.grumpysperformance.com/index.php?threads/virtual-dyno-software.2301/#post-53646


I discussed some of that late in this thread and its links
what youll rapidly come to realize is that an all out max effort engine will require about a 4500 feet per minute piston speed , a connecting rod as close to 1.8:1 length to stroke and about 13:1 compression using higher octane race fuel and a solid lifter roller valve train in most cases, this obviously requires a matching drive train gearing and while you might make far better than average power per cubic inch in the 1.5 or greater horse power per cubic inch range you also build an engine thats not ideal as a daily driver or for decent fuel economy
http://garage.grumpysperformance.co...lap-on-factory-headers.3155/page-2#post-66722

 

[Loves302Chevy]

If I were to build another 302, I would use 6.2-6.3" long connecting rods just for the reason of having
a much lighter piston. No matter which way you go, 302 pistons are expensive. The original configuration
uses 5.7" rods and the pistons have a 1.800" compression height. Because of the short 3.00" stroke, this
engine is a high rpm revver. So I would want a light piston to reduce the reciprocating weight. I'm not going
to calculate the difference in force, but I know it is HUGE. My SOLID DOME .020" over forged 12.5:1 TRW
L2210AF pistons with .193" machined off the dome to turn it into the L2209AF 11:1 pistons weigh ???
(can't find the exact weight right now), but the HOLLOW dome Speed Pro version weighs 632 grams.
My Balanced Bob Weight = 1838.6 grams using Eagle 5.7” SIR with ARP Waveloc bolts (good for 500-550
HP@7000 rpm) - 541 g total, 399 big, 142 small - made as a PINK rod replacement.
I think I could reverse calculate the piston weight, knowing the weights of the rest of the combo .

 

[busterrm]

I agree with everything you guys are saying! This guy sent his phone number and we talked Sunday for about 1 1/2 hours. It got me to thinking, so I called my machinist at home, he's a friend and said to call if I had a question. I told him the about the situation, and said that some of the better off the shelf pistons he has milled the skirts off of them to decrease the bob weight when they are balancing for shorter stroke engines. He said, that most of the time he can get pretty close to weight of a longer rod with a light piston for not much in labor. He said it only cost a few hours of labor. He also suggested as I did that with that engine a Dart SHP block would be a good investment. This engine isn't going to be a high rpm engine, even though it would be capable, he said it would not go past 6300, and that it would probably not go past 5500 on a regular basis. So I suggested a set of 185 cc heads, mild roller cam and Perf RPM or Airgap intake with 600 cfm carb. Its a street car that he wants to be fun to drive with the standard 4 speed tranny and 3.73 rear gear. Oh, btw its a 68 camaro, and it has 26.5 diameter tires also.

 

[Grumpy]

BUSTERRN ,I read that post over several times, and I'm still shaking my head !
heres why!
theres a damn good reason you seldom see guys building the 301/302 sbc engines any more and why the 383 sbc is far more popular!
now don,t think for an instant that Im suggesting you can,t build a powerful 302 but look at the facts carefully before you waste money
first basic math,
any first gen SBC based engine you build, on anything near a budget,that will limit your parts selection to reasonably priced common components, will be doing very good to produce 1.5 horse power per cubic inch
302 x 1.5=453 hp
383 x 1.5+574 HP
NEXT
piston speeds should be limited to about 4300 FPM if you expect reasonable DURABILITY in a street performance engine
302 x 4300 FPM=8600 rpm
383 x 4300 FPM=6880 rpm
next
a 185 cc head will have about a 2 sq inch cross sectional area
and, you previously stated your looking at use of a hydraulic lifter cam that
will max out as to valve train control near 6300 rpm


lets do a bit of math
just a bit of info on intake gaskets sizes to match port cross sectional areas

Calculating the valve curtain area
The following equation mathematically defines the available flow area for any given valve diameter and lift value:
Area = valve diameter x 0.98 x 3.14 x valve lift
Where 3.14 = pi (π)
For a typical 2.02-inch intake valve at .500-inch lift, it calculates as follows:
Area = 2.02 x 0.98 x 3.14 x 0.500 = 3.107 square inches
SO lets do a bit of math
a cylinder head with a 2.02' intake valve and a cam with a .450 lift at the valve with a 1.5:1 rocker will in theory produce a valve curtain area of 2.79 sq inches, swapping to a 1.6:1 ratio increases the lift to .480 lift 2.98 sq inches, increasing the available port flow potential at least in theory by about 6%, but keep in mind the port can only flow at full valve lift for the limited time the valve remains at full lift and if the narrowest section of the port cross sectional areas less that the valve curtain area that not the valve restricts flow
THUS the most you can reasonably expect is a 6% flow increase , from the rocker ratio upgrade but reality and the fact that the valve is opening and closing perhaps 57 times a second at peak rpms, and the port may be more restrictive that the valve curtain area, on many small block combos suggests the results will be lower

viewtopic.php?f=52&t=148&p=34936&hilit=calculate+port+stall#p34936

heres a chart FROM THE BOOK,HOW TO BUILD BIG-INCH CHEVY SMALL BLOCKS with some common cross sectional port sizes
(measured at the smallest part of the ports)
...........................sq inches........port cc
edelbrock performer rpm ....1.43.............170
vortec......................1.66.............170
tfs195......................1.93.............195
afr 180.....................1.93.............180
afr 195.....................1.98.............195
afr 210.....................2.05.............210
dart pro 200................2.06.............200
dart pro 215................2.14.............215
brodix track 1 .............2.30.............221
dart pro 1 230..............2.40.............230
edelbrock 23 high port .....2.53.............238
edelbrock 18 deg............2.71.............266
tfs 18 deg..................2.80.............250

USE THE CALCULATORS
http://www.rbracing-rsr.com/runnertorquecalc.html
http://www.wallaceracing.com/chokepoint.php
http://www.wallaceracing.com/header_length.php

COMMON SBC INTAKE PORTS
felpro # 1204=Port Size: 1.23" x 1.99"=2.448 sq inches

felpro # 1205=Port Size: 1.28" x 2.09"=2.67 sq inches

felpro # 1206=Port Size: 1.34" x 2.21"=2.96 sq inches

felpro # 1207=Port Size: 1.38" x 2.28"=3.146 sq inches

felpro # 1209=Port Size: 1.38" x 2.38"=3.28 sq inches

felpro # 1255 VORTEC=Port Size: 1.08" x 2.16"-2.33 sq inches

felpro # 1263=Port Size: 1.31" x 2.02"=2.65 sq inches

felpro # 1266=Port Size: 1.34" x 2.21"=2.96 sq inches

felpro # 1284 LT1=Port Size: 1.25 x 2.04''=2.55 sq inches

felpro # 1289 FASTBURN=Port Size: 1.30" x 2.31" 3.00 sq inches
Chevy V8 bore & stroke chart

Chevy V8 Crankshaft Journal Sizes

Here's a list of Chevy V-8 crankshaft journal sizes. All journal sizes are given in "STANDARD" sizes. Your crankshaft may have been cut down in size previously by a machine shop. Make sure your crank will work in the block you have. Blocks were made for each crank main journal size. If you are putting a "small" or "medium" journal smallblock crank into a "medium" or "large" journal smallblock block you will need crank bearing "spacers" or use special "thick" bearings available from aftermarket suppliers.

Chevy Smallblock V8 Crankshaft Journal Sizes


Gen.I, "Small Journal"
265...Mains-2.30"-Rods-2.00"
283...Mains-2.30"-Rods-2.00"
302...Mains-2.30"-Rods-2.00"
327...Mains-2.30"-Rods-2.00"



Gen.I, "Medium Journal", includes "Vortec" 305 and 350 thru '98
262...Mains-2.45"-Rods-2.10"
267...Mains-2.45"-Rods-2.10"
302...Mains-2.45"-Rods-2.10"
305...Mains-2.45"-Rods-2.10"
307...Mains-2.45"-Rods-2.10"
327...Mains-2.45"-Rods-2.10"
350...Mains-2.45"-Rods-2.10"



Gen.I, "Large Journal"
400...Mains-2.65"-rods-2.10"



Non-production Gen.I combination, using Gen.I 400 crank in Gen.I 350 block
383...400 crank, Mains cut to 2.45"-Rods-2.10"



Non-production Gen.I combination, using Gen.I 350 crank in Gen.I 400 block
377..."Spacer" or "thick" main bearings with 350 crank-Rods-2.10"



Gen.II, "Medium Journal", includes "L-99" 265, "LT-1" 350, "LT-4" 350
265...Mains-2.45"-rods-2.10"
305...Mains-2.45"-Rods-2.10"
350...Mains-2.45"-Rods-2.10"



Non-production Gen.II combination, using Gen.II 265 "L-99" crank in Gen.II 350 block
302...Mains-2.45"-Rods-2.10"



Gen.III, includes '97-2005 "LS-1" Corvette, Firebird, Camaro
345...Mains-2.558"-Rods-2.10"



Corvette "ZR-1", DOHC, "LT-5"
350...Mains-2.76"-Rods-2.10"


CID BORE STROKE
262 = 3.671" x 3.10" (Gen. I, 5.7" rod)
265 = 3.750" x 3.00" ('55-'57 Gen.I, 5.7" rod)
265 = 3.750" x 3.00" ('94-'96 Gen.II, 4.3 liter V-8 "L99", 5.94" rod)
267 = 3.500" x 3.48" (Gen.I, 5.7" rod)
283 = 3.875" x 3.00" (Gen.I, 5.7" rod)
293 = 3.779" x 3.27" ('99-later, Gen.III, "LR4" 4.8 Liter Vortec, 6.278" rod)
302 = 4.000" x 3.00" (Gen.I, 5.7" rod)
305 = 3.736" x 3.48" (Gen.I, 5.7" rod)
307 = 3.875" x 3.25" (Gen.I, 5.7" rod)
325 = 3.779" x 3.622" ('99-later, Gen.III, "LM7", "LS4 front wheel drive V-8" 5.3 Liter Vortec, 6.098" rod)
327 = 4.000" x 3.25" (Gen.I, 5.7" rod)
345 = 3.893" x 3.622" ('97-later, Gen.III, "LS1", 6.098" rod)
350 = 4.000" x 3.48" (Gen.I, 5.7" rod)
350 = 4.000" x 3.48" ('96-'01, Gen. I, Vortec, 5.7" rod)
350 = 3.900" x 3.66" ('89-'95, "LT5", in "ZR1" Corvette 32-valve DOHC, 5.74" rod)
364 = 4.000" x 3.622" ('99-later, Gen.III, "LS2", "LQ4" 6.0 Liter Vortec, 6.098" rod)
376 = 4.065" x 3.622" (2007-later, Gen. IV, "L92", Cadillac Escalade, GMC Yukon)
383 = 4.000" x 3.80" ('00, "HT 383", Gen.I truck crate motor, 5.7" rod)
400 = 4.125" x 3.75" (Gen.I, 5.565" rod)
427 = 4.125" x 4.00" (2006 Gen.IV, LS7 SBC, titanium rods)

Two common, non-factory smallblock combinations:

377 = 4.155" x 3.48" (5.7" or 6.00" rod)
400 block and a 350 crank with "spacer" main bearings
383 = 4.030" x 3.75" (5.565" or 5.7" or 6.0" rod)
350 block and a 400 crank, main bearing crank journals
cut to 350 size

ALL production big blocks used a 6.135" length rod.
CHEVY BIG BLOCK V-8 BORE AND STROKE


366T = 3.935" x 3.76"
396 = 4.096" x 3.76"
402 = 4.125" x 3.76"
427 = 4.250" x 3.76"
427T = 4.250" x 3.76"
454 = 4.250" x 4.00"
477= 4.5" bore x 3.76" stroke
496 = 4.250" x 4.37" (2001 Vortec 8100, 8.1 liter)
502 = 4.466" x 4.00"
557T= 4.5 bore 4.375" stroke
572T = 4.560" x 4.375" (2003 "ZZ572" crate motors)

T = Tall Deck

ALL production big blocks used a 6.135" length rod.


the valve curtain area, cam duration and lift controlling that curtain area,or port cross sectional area will pose a restriction to air flow at some point,in the engines rpm band, but you can extend the effective air flow duration and efficiency with carefully timed exhaust scavenging, that helps draw in the intake runner inertia load of air/fuel,charge much more effectively if the peak negative pressure wave is correctly timed
http://www.wallaceracing.com/runnertorquecalc.php

http://www.wallaceracing.com/lpv.php
next (and this is critical)
chevys pink rods,
are less than 50% as strong as the cheaper SCAT forged 4340 rods

http://www.scatcrankshafts.com/rods/chevy-rods/

heres a set of long scat rods that are at least 50% stronger MINIMUM than chevy pink rods at $360 a set
Connecting Rod, Pro Comp, 4340, I-Beam, 12-Point, Cap Screw, 6.125 in. Length, Chevy, Small Block, Set of 8
IF you do some careful shopping you'll find that decent connecting rods are available at semi reasonable prices, I would insist on 7/16" ARP rod bolts and 4340 forged steel, and suggest SCAT, as a lower cost but good value connecting rod source

https://www.summitracing.com/parts/sca-26125716

http://www.jegs.com/i/GM+Performanc...0&cadevice=c&gclid=COWSlpz84c8CFYg6gQodTgoOog
roughly $500 a set PLUS several hundred dollars in MANDATORY machine work

in effect about half the components youve selected will limit you to under 6300 rpm while your selecting some components to maximize 7000-8000 rpm plus performance, the only real advantage that the 302 engine potentially has is its short 3" stroke and to take full advantage of that the engine will require larger ports, a solid lifter valve train and cam thats designed to operate efficiently in the 5500rpm-8000 rpm power band, that type of cam duration will be MISERABLE to drive in the much more likely rpm band used in street transportation , (commonly 1500rpm-3500rpm)
you really need to step back a bit and either admit that a 383 better meets the limitations of a street performance engines description
OR
consider much better flowing heads,much better connecting rods, a solid lifter valve train, a manual transmission and a rear gear ratio, of at least in the 4.11:1-4.33:1 range to keep the rpm range up where the 302s short stroke has some potential advantages ID certainly suggest researching ALL components being used and carefully matching the intended rpm range power band and potential suitability
http://garage.grumpysperformance.com/index.php?threads/which-dart-shp-4-0-or-4-125.3219/#post-44637

http://garage.grumpysperformance.co...gine-to-match-the-cam-specs.11764/#post-55651

http://garage.grumpysperformance.com/index.php?threads/types-of-crankshaft-steel.204/

http://garage.grumpysperformance.com/index.php?threads/rod-bolts-rpm-vs-stress.341/#post-417

http://garage.grumpysperformance.com/index.php?threads/calculating-ideal-port-size.624/

http://garage.grumpysperformance.com/index.php?threads/bits-of-383-info.38/

http://garage.grumpysperformance.co...lap-on-factory-headers.3155/page-2#post-66722

http://garage.grumpysperformance.com/index.php?threads/types-of-crankshaft-steel.204/

 

[busterrm]

I realize what your saying Grumpy, those guys are convinced that's ticket. The guy that started the thread is wanting it to be close to what the car came with when it was introduced in 68. I made the comment to him about building a bigger engine. I suggested a mild roller cam! Personally I would put 400 in it!

 

[Loves302Chevy]

Don't feel bad busterrm, Grumpy yelled at me about my 302 also. But I do see his points.
Someday, I'm going to put that 302 in something and see what it can do - or not.

 

[busterrm]

I agree with him and I agree with you also. I see a bigger engine being more dependable and able to produce greater numbers than the smaller engine. But, the 302 can produce some great numbers, but you have to spend a great deal of money to get into the rpm range where it will produce said numbers. All forged parts, solid roller cams, rev kits, bigger port heads, etc...... The engine in question I feel will be a good one but its going to be so restricted to run in rpm range it wasn't designed for. Those engines were designed for Trans-Am racing where they spend most of their life above 6500 rpm for long periods of time.

 

[busterrm]

Don't feel bad busterrm, Grumpy yelled at me about my 302 also. But I do see his points.
Someday, I'm going to put that 302 in something and see what it can do - or not.

I would put it in something light with a manual tranny and a big gear in the rear end to get up into the rpm range where its the most powerful.

 

[Loves302Chevy]

This is going to make Grumpy pucker, but here goes anyways. From my notes:

3970010 block 4 bolt mains .020 over
Original (perfect) 302 LJ forged crankshaft STD/STD, nitrided
Eagle 5.7" SIR connecting rods
TRW forged pistons 10.25 SCR
Total Seal TS1 gapless race rings
Fluidamper 7 1/4" SFI Approved Balancer
Pete Jackson "QUIET" Gear Drive
Edelbrock Aluminum 6073 Performer RPM, 2.02/1.6, 185 cc/70cc chambers, gasket matched to Felpro 1205
100% smoothed ports and bowls blended, Severe Duty stainless valves, PSI LS1511ML Beehive springs
CraneCams 99095 machined locks, ARP 7/16" rocker studs
CV .5/16" .080 wall 7.850" one piece hardened chrome moly pushrods
JEGS Premium Gold '50' series .150 offset intake/STD exhaust 7/16" Aluminum full roller 1.6 ratio
CraneCams 11604-1 Quick-Lock Valvetrain Stabilizer
Melling M55HV oil pump with Orange Spring
Victor Reinz Nitroseal #5746 head gaskets 4.100 .026 thick 5.4 cc
Holley Contender Z-28 #300-36 intake manifold, gasket-matched
Edelbrock 1407 manual choke non-emission carb - 750 cfm
Full MSD ignition and distributor, no vacuum advance
Crank Scraper
ARP Head & Main bolts

Crower #00350 SOLID Flat Tappet cam
Broad power band, Short oval profile, Heavy car
Advertised Duration 268/274 238/244 @.050
.497/.503 lift (1.5), .530/.537 (1.6), 107 LSA, 57 degrees overlap
rpm range 2000-6000 in a 350/400, redline 7000

Dynamic Compression Ratio Calculator
(Use seat to seat specs for Intake spec for best results)
Number of Cylinders : 8
Bore in Inches : 4.020
Stroke in Inches : 3.000
Rod Length in Inches : 5.700
Static Compression Ratio : 10.25 to 1
Inlet Valve Closes ABDC : 57 º
Boost Pressure in PSI : 0
Target Altitude : 177 (Feet)
Camshaft, Rod Length, Boost and Altitude Correction to Compression
Static compression ratio of 10.25:1.
Effective stroke is 2.46 inches.
Your dynamic compression ratio is 8.55:1
Your dynamic cranking pressure is 173.24 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 8.55 :1
V/P (Volume to Pressure Index) is 130

And here is where Grumpy's ass starts to tighten.

Rhoads #8178X VMAX RACE Variable Duration "hydra-solid" lifters
Rhoads claims safe to 7500 rpm
That's right. HYD lifters on a SOLID lifter camshaft.
Why? This mild solid lifter camshaft only pulled 5" of vacuum with solid lifters. With the new Rhoads VMAX lifters, I was able
to get a 4" increase in vacuum at idle.
1000 rpm idle / 8½" vac, 1050 rpm idle / 9" vac, 1100 rpm idle / 9½" vac with 2 turns out mixture screws and 36 degrees total
timing (locked out), reads 33 degrees at idle.
On the engine test stand, the engine is VERY responsive and effortlessly revs to 8000 which is where I have the rev limiter set to.
This small cam probably should not even get there. With a slow rev, the engine accelerates very quickly once it hits 2400 rpm.

Did I just accomplish my goal of getting a 302 Chevy to have a more streetable bottom end while still keeping the top end???

OK. Let me have it. I have a big jar of Vaseline.

 

[busterrm]

I am saying nothing, I am not digging a hole for someone to toss in my carcass!

 

[busterrm]

Researched all your parts, I see it making about 465 hp @ 6500 and 415 tq @ 5000. 2400 its about 315 tq and keeps rising till it peaks @ 5000. With a manual tranny and some big gears it could be fun. This a DD2000 guesstimation though!

 

[Loves302Chevy]

My DD2000 comes up with 435 HP @ 7000 rpm, 396 TQ @ 5000 rpm.
I have included the zipped DD2000 file.
I did not have my heads flow tested. The flow numbers I used were found on the internet,
but I'm not sure if they are for the older 170 cc versions, or the later 185 cc versions, which I have.
If I change to Victor Jr heads, the compression gets bumped up to 10.6 and I get 479 HP @ 7000
and 418 TQ @ 5000 with a single plane intake and all other parameters the same.

This engine sounds like sweet music at 8000 rpm.

 

[Loves302Chevy]

I ran across this in my notes:
from Air Flow Research 302 test: Initial pulls were made with 35 degrees of total timing but we quickly found out
that the combination of the short stroke and high-dome pistons wanted significantly more ignition timing.
The power climbed with each successive increase in timing until we reached a total of 41 degrees.

Does anyone have any thoughts on this?

 

[busterrm]

I picked up the flow data from edelbrock, I also correct them for 3% more for the portmatch and bowl cleanup. That is where the added hp came from probably. Here's the numbers: Intake .100 = 64.9, .200 = 127.7, 300 = 186.3, .400 = 233.8, .500 = 260.6, .600 =260.6 Exhaust .100 = 52.5, .200 = 96.8, .300 = 131.8, .400 = 150.4, .500 = 161.7, .600 = 167.9. There you have it!

 

[Grumpy]

now when your through playing with the software dyno and that 302 simulation,
just humor me a second, I want you to add 8 degrees to the intake cam lobe duration,
and change the stroke to 3.75"
, so your building something closer to a 383,
and compare the two power curves.
then tell me again why a 302 is the best option.....
and keep in mind the cylinder heads are far from ideal for the larger displacement,
you could easily gain an additional power boost with 210 cc port heads
just for discussion sake here.....
lets discuss why you factor in piston speeds
Ill point out that the probable strength limitations,
in the 355 block and rotating assembly
(assuming good forged components and ARP main studs are used)
yes as pointed out earlier, both engines below would be pushing well past the limitations imposed by a STOCK, O.E.M. production block
but assuming that the O.E.M block will hold up at least for a hundred 1/4 mile passes,before it comes violently apart at peak rpm, that stress limitation,
will be imposed by both common valve spring limitations and piston speed on the rotating assembly and block,
on a 355 chevy with its 3.48" stroke , (assuming a 4200 fpm max reasonable piston speed)
has a peak rpm near 6700-7200 engine rpm, selecting a cam that peaks below about 6700 rpm-7000 rpm,)
leaves the potential advantage of that shorter stroke the 355 sbc on the table.
this is one reason that the 383 with its longer 3.75" stroke is currently the most popular combo with a 4.30 bore block.
if your going to build a 355, then you may as well take full advantage of the engines potential strong points.
a similar longer stroke 383 would be limited to about 6300 rpm-6700 rpm but the trade off is about 40 ft lbs more torque over most of the potential power band
the formula for hp is
torque x rpm/5252= hp
if both engines make about 1.2 hp per cubic inch
the 383 will peak about 400 rpm lower than the 355 if both are built to maximize the engines potential strong points
just for giggles and to point out
why you maximize a RACE ENGINE potential RPM LIMITS
lets assume the 355 power peak is at about 6800 rpm and,
the similar 383 would be peaking nearer 6400 rpm
if you have 1.2 x 355=426 ft lbs x 6800 rpm /5252=551 hp
if you have 1.2 x 383=460 ft lbs x 6400 rpm /5252=560 hp

 

[busterrm]

Point taken, bout same hp(474) @ 6000, has 470 tq @ 4500. Put my mag 280 roller and it jump 500hp/494tq both same rpm

 

[busterrm]

love302 go ahead with your lil screamer I'll stick with my 400. Put a good set heads on it and dual plane and have 540hp/500tq. No replacement for displacement !

 

[Loves302Chevy]

I picked up the flow data from edelbrock, I also correct them for 3% more for the portmatch and bowl cleanup. That is where the added hp came from probably. Here's the numbers: Intake .100 = 64.9, .200 = 127.7, 300 = 186.3, .400 = 233.8, .500 = 260.6, .600 =260.6 Exhaust .100 = 52.5, .200 = 96.8, .300 = 131.8, .400 = 150.4, .500 = 161.7, .600 = 167.9. There you have it!

Here is the numbers I used:
Intake .200 = 140, .300 = 200, .400 = 238, .500 = 244, .550 = .244, .600 = .244, .600 = .244

Exhaust .200 = 108, .300 = 144, .400 = 163, .500 = 175, .550 = 180, .600 = 183

I like your numbers better.

then tell me again why a 302 is the best option.....

Nobody ever said that a 302 is the best option. It's just different.
My goal was to get a 302 Chevy to have a more streetable bottom end while still keeping the top end.
Don't forget that Ford used their 85-96 302 engines in the fox bodies during that era and they had the same bore and
stroke as the Chevy 302. The Ford had 5.4" rods and the Chevy used 5.7".
They ran pretty well. I hope my Chevy 302 does even better.

 

[GLHS60]

While long rods don't impress me, 302 Chevys do!!!

I had a 1969 Z28 Engine many years ago that I ran in several different cars.

Nothing but fond memories of that little jewel.

Its final spot was a Vega automatic, not sure where it went after that.

I've had a couple of 1969 Z28's that were excellent all around cars.

One I took on a cross country trip, that Engine was always "on the cam"

I find it strange that Chevy guys always go for the cubes, almost like they don't want to get compared to those pesky 302 Fords.

Thanks
Randy