Guidelines to building a 302

[HarrisonTX]

You are right, but what I think he is saying is a 383 has a bigger push. More power trumps more friction.

 

I would think the piston friction will be small compared to the energy that must be pumped into the heavier rotating mass.

 

And when in gear, the engine that revs the fastest is the the one in the car that accelerates the fastest. Once again, power rules. In that case the 383 will almost certainly win.

 

Well, i never said the 302 would make more power than the 383, im not denying that. I am strictly standing up for the rev speed. Mario didnt say anything about making power, he just was talkin about a buzzin motor, so thats what i was talkin about.

 

Heres some more to chew on 280z

 

What do you know about piston speed?

A 383's piston will be traveling alot faster than a 302's at 7,000 rpm. The faster the piston is going, the more stress that will be on the rotating assembly when it has to go from haulin ass, to completely stopped at TDC, or BDC. The faster the piston is going, the more stress that will be on the rotating assembly.

 

Nascar motors run honda size crank journals. 1.8. Why?

bearing speed.

a 383 will have a large journal crank, which will have a a higher bearing speed than my small journal 302.

a large journal crank will have more friction on the crank which will also contribute to slower revs.

the 383's crank also weighs more, which will make it rev slower.

 

A 383 will need more cam than a 302 because it has to flow more air for any given rpm. That being said if your talking stress on valve train than the 383 for any given rpm would have more stress if it has a bigger cam.

A bigger cam, more spring presser to prevent valve float, this would cause more friction and there for make the 383 rev slower.

[grumpyvette]

for those guys that think high rpms are the way too go....,think about this, in a correctly clearanced and ballanced lower assembly,

piston speeds should almost always be UNDER 4000fpm with correctly reworked stock type parts , or 4500FPM with all forged aftermarket race quality parts, if you expect the lower assembly to live a decent life span, thats,

between 8000-9000rpm on a 302 and 6400-7200 rpm with a 383 so as you should see, its far more likely the valve train is the weak link that determines the RED LINE

since the cars engine speed is usually restricted to the rate of accelleration of the car due too the engine being locked into driving the drive train,the larger engine has a slight advantage in accelleration with equal rear gears but in the real world youll run 3.73:1-4.33:1 rear gears with a 383 and 4.56:1-5.13:1 with a 302, making the crank accelleration rates similar, or higher with the 302.

personally Ive never seen any advantage to spinning a smaller stroke engine to higher rpms, to make power, the stress on the valve train and lower assembly tends to cause more parts failures, its a whole lot easier to control valves at 6000rpm than at 8000rpm, and it gets darn expensive when pistons kiss valves, keep the engine operating well within its safe/ low stress speed,limits and it will last far longer, at 8000rpm the valves open and close in each cylinder 67 TIMES A SECOND, your approching absurd enertial loads and valve train control problems well under that at 6400 rpm where the valves open and close at 53 times a second

[woldson]

Sorry Mario, I confused you with mopar, my freind has a ton of connections in this town. He is also the one that build that 351 winser @ 805 hp at the wheel, i wanted to hook you guys up. P.S. Spalding's in our town gets brand new cars from gm that gets dismantled here. They love playing with them before dimantal. I.e. corvettes and others!

[wheelman]

http://www.hotrodders.com/forum/chevy-302-help-4624.html

Another way to build one.

 

With an LT4 3in crank (large journal) and 5.94" rods, then you can choose the compression ratio with the heads using a 4" bore block. I'm going to see if I can find one of these locally.

 

The stock LS1 redline is 6.2k rpm but I've heard with upgrade valve springs and retainers you can spin them close to 7k rpm.

 

Woldson, I'm in Tucson AZ, but if you still need me to call you I will

Mario

 

You are wrong in calling this crank an LT4 3" unit.

The engine this crank comes from is an L99. Externally it looks identical to an LT1 but has a 3" stroke and a 3.75" bore which makes it a 265.

The crank is not forged and the rods are powdered metal, not exactly the strongest combination. It is externally balanced and set up for a 1 peice rear main seal so has to be used with a later block.

 

I thought real hard about using one of these cranks with my LT1 block to build a 302 but after reading Grumpy's posts addressing the real differences between the larger and smaller displacement engines I changed my mind.

Currently my engine is a 350ci LT1 (stock bottom end) with an LT4 hotcam and heavier valve springs. I set my rev limiter at 6300 and ran the engine on a dyno, power peaked right at 5800rpm but only dropped slightly all the way to 6300. I've since lowered the rev limiter to 6000rpm for safety's sake.

 

All this to say that building a motor for high revs does not require a short stroke, but a very good valve train and high quality lower end parts.

If you want a 302 to be different, go for it, I really like the idea.

I would still like to build a 302 LT1 but probably won't, there are other issues with this build than are encountered with older parts. If I put a little more money into my LT1 valve train I can spin the engine to 6500rpm without problems (other than the stock EFI won't reliably control it at that level).

 

Wheelman

[grumpyvette]

I thought you guys might enjoy reading these two posts on a similar subject post on a differant site

 

MY ORRIGINAL POST

 

I get asked why the 301/302-327-331 sbc engine, is just not seen as comonly any more, the basic reason is the 283-327 they were built from is no longer as comon as the current 350 basic core engine the 383-396-401 gets built from, as the 350 sbc is far more comon.

just some info guys....theres a GOOD REASON why the 302 is less than popular compared to a 383-401 stroker built from a 350 basic block.

THERES NO way a 302 with its 3" stroke and the higher stress on the valve train that rpms over 7000rpm that the 302 sees will match the results and dependability a 383-396-401 stroker combo with its 3.75"-3.875" stroke and under 6500rpm valve train stress will produce

lets say a 302 can produce 1.25-1.4 hp per cubic inch, you can do the same with a 396 sbc

your looking at say 410 hp for the 302 and a similar 396 sbc costing almost the same will produce 535 hp with the same hp per cubic inch WITH LOWER VALVE TRAIN STRESS, its a FACT your far more likely to have valve train problems at over 6500rpm than under that rpm

theres also a much faster ramp up on the torque curve with the larger displacement.

we USED to build 301-327-331 sbc when the cylinder heads flow limited the effective displacement that could effectively be fed, those days are long gone, with the current aftermarket heads.

 

example

 

http://airflowresearch.com/articles/article031/A-P1.htm

 

http://www.chevytalk.org/fusionbb/showtopic.php?tid/131229/

 

http://www.bracketmasters.com/small_block_stroker_383_cu.htm

 

http://airflowresearch.com/articles/article014/A14-P1.htm

 

http://airflowresearch.com/articles/article016/A16-P1.htm

 

btw USING A HYDROLIC LIFTER VALVE TRAIN in a 302-331 SBC thats built for MAX HP,is about as useful as snow shoes on a snake

 

ID also point out the differances in bearing sizes and the difficulty in building good compression with flat top pistons with the shorter stroke combos

 

http://www.mortec.com/journal.htm

 

http://www.mortec.com/borstrok.htm

 

 

in a correctly clearanced and ballanced lower assembly,

piston speeds should almost always be UNDER 4000fpm with correctly reworked stock type parts , or 4500FPM with all forged aftermarket race quality parts, if you expect the lower assembly to live a decent life span, thats,

between 8000-9000rpm on a 302 and 6400-7200 rpm with a 383 so as you should see, its far more likely the valve train is the weak link that determines the RED LINE

since the cars engine speed is usually restricted to the rate of accelleration of the car due too the engine being locked into driving the drive train,the larger engine has a slight advantage in accelleration wioth equal rear gears but in the real world youll run 3.73:1-4.33:1 rear gears with a 383 and 4.56:1-5.13:1 with a 302, making the crank accelleration rates similar.

personally Ive never seen any advantage to spinning a smaller stroke engine to higher rpms, to make power, the stress on the valve train and lower assembly tends to cause more parts failures, its a whole lot easier to control valves at 6000rpm than at 8000rpm, and it gets darn expensive when pistons kiss valves.

at 8000rpm the valves open and close in each cylinder 67 TIMES A SECOND, your approching absurd enertial loads and control problems well under that at 6400 rpm where the valves open and close at 53 times a second

 

http://purplesagetradingpost.com/sumner/techinfo/350%20chevy%20engine.html

 

heres some info for the guys wanting a stroker/carb combo

 

here are the specs: of a well built 383

 

4-bolt 350 block bored .60 over

eagle 3.75" crank

eagle 6" h-beam rods

wiseco forged flattops with total seal rings--12.5:1 comp.

custom ground comp solid roller

251/260 duration @.50

640/653 lift with the 1.6 roller rockers

109 LSA and 106 ICL

huge brodix single plane--(main reason for "low" tq??)

750 dominator carb worked over, not sure of cfm (another

reason for "low" torque?)

dart pro 1 215cc heads ported with 2.05/1.60 valves

hooker super comp 1 3/4" headers

NOS plate system

full msd ignition and 10.4mm taylor wires

electric water pump, electric fuel pump, and electric fan

 

the motor also has stud girdles and a rev kit and i went with all forged internals so i can "spray" the poo-poo out of it.

522hp/498tq

 

 

 

heres a well built SBC 406

· Block, 509, +30, Zero deck, Blanked water passages, Clearanced oil ways, Lifter valley vents, ARP main & head studs, Durabond cam & Clevite 77 main bearings.

· Crank, Scat 4340 forged steel, 3.75”, internal balance, Pioneer SFI balancer + ARP bolt.

· Rods, Comp. Products 6.00” H beam bronze bushed + ARP bolts Clevite 77 bearings.

· Pistons, SRP #4032 flat top, 5cc relief, Speed Pro plasma moly file fit rings.

· Complete rotating assembly balanced. Including - Flywheel, Clutch, Balancer & Crank pulley.

· Heads, AFR 210 Race Ready, 76cc, 2.080/1.600 valves, drilled for steam. FelPro #1014 gasket.

· Cam, Comp. Cams ‘Magnum’ #12-450-8 (286HR) Hydraulic roller.

230/230 @ .050, .377 lift 110 LSA 106 ICL.

· Pushrods, Howards Cams heavy wall 5/16” 7.4” long.

· Rockers, Pro Magnum roller, 1.6, 7/16” stud.

· Lifters, Pro Magnum hydraulic roller. AFR Hydr-Rev kit.

· Comp Cams Springs #950 + #740 retainers installed at 1.875”

· AFR rev kit, AFR stud girdle.

· Lube, Melling M99HVS pump, Canton 7qt 5 trap pan with inbuilt windage and scraper, Cooler, Accumulator, oil stat, remote filter.

· Holley 800cfm #4780C, 1” spacer, Victor Jr single plane.

· Static CR 10.32, Dynamic CR 7.9.

· Quench 0.0415” (Gasket .039” + .0025” down hole).

· MSD Pro Billet Street Dizzy, MSD 6AL, MSD Blaster 2 coil, MSD 8,5mm leads.

 

RPM BHP Torque

3800 367.3 507.7

3900 384.0 517.1

4000 395.1 518.8

4100 407.9 522.5

4200 418.9 523.8

4300 429.4 524.5

4400 439.6 524.7

4500 449.6 524.7

4600 462.1 527.6

4700 467.4 522.3

4800 476.6 521.5

4900 485.4 520.3

5000 489.2 513.9

5100 498.5 513.4

5200 496.0 501.0

5300 506.1 501.5

5400 508.4 494.5

5500 508.7 485.8

5600 505.6 474.2

5700 505.8 466.0

5800 505.8 458.0

5900 494.6 440.3

6000 491.9 430.6

 

"grumpy: Sorry pal...but your theories don't seem to fit in real life. Might I refer you to this website:

 

http://www.z28camaro.com/oldrel.html

 

And here's some data for you to chew on:

 

TECHNICAL DATA

VIN number 124378N411100

Build Date 04A (first week of April)

Color Corvette Bronze

Interior Code 712, black standard

Car Shipper Shipped on April 11, 1968 to Ammon R. Smith Auto Company, York, PA

Engine Data Cubic Inches, 302

Cylinder heads #3917291, completely stock, no porting allowed!

Stock rocker arms & valve springs

Intake 302 aluminum intake, casting #3917610

Carburetor Holley, #4053, 780 CFM 4bbl

Camshaft Crane, .480 inches lift, 272 degrees duration, valve lash, .016-.016

Pistons GM 302, .030" oversize

Horsepower 456 @7700rpm

Rear Tires 9" x 30.0" Hoosier's

Rear axle & ratio 12-bolt, 5.57 Richmond Pro Gears

Clutch 10 inch, three finger from Advance Clutch Technology

Shift Points 8200 RPM

BEST ET 10.80 @122.30mph

 

Now for a FACTUAL explaination of why the 302 isn't seen any more. It's really quite simple. People who drive cars on the street are more interested in tork than in horsepower and 1/4 mile performance, and they'd rather have creature comforts than put up with a REAL race engine. They want to sense the FEEL of power, rather than actually go fast. A 302 like the one built above would NOT be "fun to drive" for most guys today. You have to bring the RPMs up pretty high to pull away from a stoplight. It's going to require something other than pump gas to run good. Fuel economy will be pretty shitty. It won't run for ♥♥♥♥ with an automatic transmission. And things like air conditioning are out of the question. The 302 Z-28 engine is a RACE ENGINE that was adapted to the street. In stock form it put out closer to 350 horsepower than the 290 it was rated at from the factory. And reaching 400+ horsepower is not all that difficult with this engine. The 302 engines were actually pretty long-lived in both drag racing and Trans Am applications. It was quite normal for drag racers to come off the line at 8000+ RPM and just dump the clutch and power shift all the way through the 1/4 mile at those same high RPMs. And the Trans Am engines, much like the 358 CI NASCAR engines of today, LIVED at 8000+ rpms for HOURS at a time. As you can see, Dave Strickler uses a STOCK valve train and was shifting at 8200 RPM. No weak link there at all. Many guys today think they have to have gold plated roller rockers and all kinds of whiz-bang aftermarket parts to make a SB Chevy run good. I blame the magazine ads and media for that. It simply ISN'T true.

 

Perhaps you should check your theories with real life before propagating myths

 

Dep "

 

my responce

 

"first were talking about street/strip engines here, THAT YOU CAN BUILD USEING THE STOCK BLOCK AND HEAD DESIGN THAT CAME IN THE CAR and not applications where you expect to tear down and inspect or refurbish the engine every few weeks at the most,

Ive built enought engines and seen enought engines raced to know EXACTLY what Im refering too!

and in the combo you put forward there would EASILY be an additional extra 80-100 hp if the engine had been fitted with a 3.75 or 3.875" stroke rotating assembly, and having it run 1000rpm-1500 rpm lower in the rpm range, and of course the correct cam installed with slightly less durration and a tighter LCA.

NO!

Ill stick too FACTs and EXPERIANCE!:thumbsup:

you may feel that spinning an engine 8000rpm is a valid option, but its only a matter of time before that stock valvetrain self destructs, nascar engines are HARDLY a valid comparison,and if theres anything stock about MUSHROOM base lifters and the rest of the valve train comonly used in nascar or similar engines with parts like in a 18 degree cylinder heads HONDA size CRANK JOURNALS or SB2.2 canted valve heads, I can,t think of it!

BTW was & is very comon for TRANS-AM and NASCAR teams to replace/rebuild engines after every race, hardly ideal charicteristics in a performance application where you want to drive a street/strip combo for years at a time with only minor maintinance like plugs and oil changes.

an engine that can live AT 8000RPM for " HOURS AT A TIME" is BOTH A myth, (THEY MAY HIT 8000RPM BUT THEY DON,T average 8000RPM for " HOURS AT A TIME" ) AND AN ENGINE CAMMED TO MAKE POWER AT THAT RPM WOULD HARDLY BE, ideal for a corvette youll be building for street strip use and Im very sure even DAVE Strickler , would not suggest it as a first choice for an engine you occasionaly race, but depend on for at least occasional transportation or short trips, and the ONLY REASON the trans-am guys sellected the 302 displacement was the CLASS RULES LIMITING THEM TO 305 CID/ or 5 LTRS. if that rule was not MANDATORY they would have vastly prefered the 377 displacement SBC like the earlier racing corvettes in the early 1963-5 grandsport cars

 

BTW theres not a single major component in a current NASCAR engine that you can use from your first gen SBC, and the only reason anyone I know uses a stock valve train is rules MANDATING its use or cost factors

 

http://www.howstuffworks.com/question588.htm

 

http://www.usatoday.com/sports/motor/nascar/2007-04-10-chevy-engine_N.htm

 

http://www.pressbox.co.uk/detailed/Business/Team_Chevy_Introduces_New_Racing_Engine_115115.html

 

current NASCAR TECH ENGINE.....$35,000 AND UP

 

It's a 358 ci and is totally unrelated to the previous SB2 derived Chevy NASCAR engine. It has wider bore spacing (4.5 versus 4.4) for better coolant and oil circulation, easier to reach front-mounted distributor; six (rather than five) bolt cylinder heads to improve sealing and reduce distortion; a higher mounted cam lifting shorter and stiffer pushrods; cast-alloy rocker covers that incorporate integral oil galleries; carbon-composite timing cover; symmetrical LS style valves in place of the SB2's mirrored layout."