thinking about building a 283,305,or 307 this may be


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thinking about building a 283,305,or 307 this may help


A totally stock 305-307 SBC as you know is rather pathetic in both head flow and cam timing as most were designed as fuel economy combos, and most have restrictive exhaust. that doesn,t mean the engines hopeless ,if you think back, there were some rather impressive (at the time) corvette engines in 283 displacement in the past, Im only pointing out that you need to think thru your choices carefully, Ive normally seen better results when both the intake and cam are upgraded, a common combo of well matched parts for a 305-307 sbc is
the combo of intake and cam alone, is usually worth about 30-35 hp, which is a darn nice gain, the intake alone is probably worth 10-15hp, but its going to be worth more as the cam and heads are upgraded to flow more also, because its not nearly as restrictive as the stock intake.
the heads plus intake and cam should easily be worth 50-60hp minimum. but before you go throwing cash into a 305-307 you might just want to save up and build a 383-406 SBC that has more potential.
read this

these links and sub links should help ... ne_blocks/ ... ewall.html

most guys with the smaller SBC engines that want more performance are working on very limited budgets and thats understandable , but power is hugely dependent on moving a decent quantity of fuel/air mix efficiently thru your engine and your cam, timing compression ratio head flow rates and intake and exhaust flow is just as important with the smaller engine sizes , you can expect to make about 1-1.2 horsepower PER CUBIC INCH OF DISPLACEMENT in a properly designed engine a bit of math should show you why a 350-383-406 has a great deal more performance potential than a 283-307 sbc, and the smaller engine bore sizes restricts effective head flow rates, the chevy vortec heads, and the trickflow 175cc heads with their smaller combustion chambers and ports designed for the smaller displacements are almost a perfect match to the 283-307 displacement engines flow characteristics, if you read thru the site youll find a great deal of support info on how to select components
EXAMPLE pay attention to the bore stroke ratios, a 307 with its greater bore and shorter stroke , and slightly ;larger displacement and less valve shrouding should ALWAYS show a slight advantage in performance over a 305 as a basic engine

Chevy V8 bore & stroke chart

Post by RebStew on Fri 08 Feb 2008, 3:28 pm

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



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"
496 = 4.250" x 4.37" (2001 Vortec 8100, 8.1 liter)
502 = 4.466" x 4.00"
572T = 4.560" x 4.375" (2003 "ZZ572" crate motors)
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Re: if your thinking about building a 283,305,or 307 this may he

Ok so you want a high rpm screamer, thinking about building,a 302 like the old Z28 engines?
well technology has advanced and theres better current options if your really interested
heres a mid priced effective combo

Ok time to get back to reality! a 305,307,283 and similar smaller than 4" bore SBC engines can and do limit the cylinder heads and valve sizes you can use do too mechanical clearance issues with the valves potentially hitting the engines cylinder bore walls, with larger valve sizes in many applications,

if your serious about building a high rpm screaming sbc I can,t think of anything Ive built or seen built that sounds better or pulls harder than a PROPERLY BUILT 377 , thats a 400 block with a 350 crank, it will spin at 7000rpm quite happily with a decent solid lifter valve train and the extra cubes more than compensates for the slight rpm advantage of the smaller 302.
a properly assembled 377 will easily exceed 500 flywheel hp and have noticeably more torque than a similarly built 302, and before you ask it should be rather obvious that the engine built like that requires a proper quench and some bowl & chamber work and un-shrouded valves and its very unlikey to run on high test without some octane booster

youll want a manual transmission and a 4.11-4.56 rear gear

heres a combo thats KNOWN to work, but it requires race octane 105 gas
because its a 13:1 compression sbc race combo



Cylinder Heads, IK 200, Aluminum, Assembled, 64cc Chamber, 200cc Intake Runner, Chevy, 327, 350, 400, Pair

the heads you select will be rather critical here so don,t scrimp, youll need decent roller rockers AND a matching rocker stud girdle,


block (dart 4.125" bore)
Engine Block, Cast Iron, 4-Bolt Mains, 4.125 in. Diameter Bore, 2-Piece Rear Main Seal, Chevy,Small Block
crower cool face solids

Part Number: 00351
CROWER Chevrolet Mechanical Flat Tappet Camshaft

Chevrolet - 262, 267, 283, 302, 305, 307, 327, 350 & 400
Performance level 5 - Compu-Pro - Most popular NASCAR and Sportsman grind. Great high torque and mid-range power.
INT/EXH - Dur @ .050” Lift: 254°/262° RR: 1.5/1.5 Gross Lift: .525”/.546” LSA: 105° RPM: 3000 to 7000 Redline: 7500

pistons 6.0" rod 377 pistons have a compression height of 1.260
youll want custom pistons with a forged dome too get to 13:1 compression
if you use the pistons below you can build a 10.4:1 street version, the loss in compression will cost you 40 hp or a bit more

Connecting Rods, 4340, I-Beam, 12-Point, Cap Screw, 6.000 in. Length, Chevy, Small Block, Set of 8

Crankshaft, 2-Piece Seal, Internal Balance, Forged 4340 Steel, 3.480 in. Stroke, Chevy, 350, Each

long tube 1 3/4" tube headers that fit your application

a decent 7-8 qt baffled oil pan, that fits your application



IVE BUILT OVER 100 plus SBC ENGINES FOR THE MUSCLE CAR CROWD AND A FEW CIRCLE TRACK GUYS OVER THE YEARS,if your goal is the least expensive engine that produces good hp the 350 or possibly a 383 is a very viable starting point as a 302 will cost more to build in most cases, yes you can build a nice responsive 302 sbc, and Im sorry you think Im trying more to dissuade him than give useful advice, Im really only using experience to suggest a route that in the long run will be less expensive,.... if you do this stuff long see trends.. you find that if you build a small displacement combo, the guys always come back, after consistently seeing the tail lights of their competition, asking what they can do, and the answer is always the same, you basically can throw a ton of money at any project or increase the displacement, because its simple physics
youll make about 1.2-1.3 hp and ft lbs of torque per cubic inch of displacement, using basically stock style components

302=377 hp
377=471 hp

just some info
theres two basic bore sizes,in the more common SBC engines, the 350 block with its 4"-4.060 bore and the 400 block with its 4.125-4.185 bore
many people build 355s by just boring the 350 .030 oversize with higher compression pistons,and are happy with that, the guys wanting more horsepower and torque build 383s by adding a 3.75" stroke crank, or a 396- 401 with a 3.875 crank and new higher compression pistons, you can make very good horsepower from that engine block and bore size. now if you upgrade to a 400 style block with its larger bore you could build a 377,you could reuse the 350s rods and crank, with bearing spacers in the 400 block with bigger pistons.
But I don,t build many 377s anymore for one very simple reason,
please follow the logic
people build 383s to get the most potential power from that bore size and the 350 block they already have in their corvette for the least cost,for the best resulting power. but a 400 block with its bigger bore is not effectively getting its full potential with a 350 crank to build a 377 you need a 350 crank with a 3.48 stroke and a 400 block bored .030 over sized (4.155 bore x 3.48 stroke x 8= 377.48 displacement)
if you already have the 4.155 bore block and you install a 3.75 stroke crank youll have a 406.77 displacement, if you install a 3.875 stroke crank thats a 420 displacement....... and considering youll make about 1.2-1.4 horsepower per cubic inch of displacement with identical parts and that the combination of the longer stroke and 29-43 EXTRA cubic inches of displacement provide a noticable increase in torque and horsepower, (similar peak horsepower but 30 to 60 ft lbs of TQ more is comon) and that the higher average rpm levels in the 377 tends to get into valve float much more easily... I find its just comon sence to build a 406-420 engine not a 377

570 HP
AFR 210cc Competition Package
750 Carburator
MSD Distributor @ 36° Timing
Lunati Hyd. Roller Cams 242°-252°
.560-.572 lift 112 Lobe Centers
1 7/8" Hedman Headers

500 HP
AFR Street 190 Cyl. Heads
Holley 0-4779 750 cfm
MSD Distributor 36° Timing
Comp Cams 12-433-8 Hyd Roller Cam
1 3/4" Headers

most of you will not exceed 450-470hp in your engines, so keep in mind that rods and rod bolts fail far more often then cranks, Id put the money you save buying a good cast crank into a set of (H) style rods with 7/16" rod bolts, a cast crank with good rods and rod bolts that's been balanced and clearanced correctly should have ZERO PROBLEMS at your power level

one piece of advice thou, its almost always best to buy the crank as part of a matched set of parts in a ROTATING ASSEMBLY KIT and get a FLUID DAMPER harmonic balancer and if possible have the INTERNALLY BALANCE STYLE KIT, as it has FAR LESS stress at high RPMS
heres some places to look
(stroker kits)

and also remember the cylinderheads, cam, and compression ratio must match your intended hp goals
(800) 444-7373
(I buy more kits from these guys , ask for LARRY ext 106) simply because they CUSTOM ASSEMBLE EVERY KIT PART BY PART so you get EXACTLY WHAT YOU ASK FOR,NOW THAT OF COURSE REQUIRES YOU TO THINK THRU YOUR PART LIST AND ASK FOR THE CORRECT MATCHING PARTS (heres what I comonly ask for in a 383 kit) be very specific as to the brand and part number of parts included in the kit if its important to you!they will try to save you money with cheap parts if you don,t get specific in your parts list! ITS YOUR FAULT NOT THEIRS IF YOU DON,T GET THE CORRECT PARTS ORDERED

internally balanced crank (cast or forged)(depends on hp level, 450hp or below go cast, forged is to some extent wasted money)
MATCHING (H) style rods, set up for floating pins and main bearings that fit your block(350 size mains)(400 size mains)
(H) style 5.7 or 6" rods
with 7/16" bolts
forged pistons for floating pins(MUST MATCH RODS and be .030-.060 oversize) with matching light weight pins and locks and be the correct cpr
matching rings
quality balance
race quality flexplate
ARP oil pump drive shaft
have assembly balanced either by them or locally
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Re: if your thinking about building a 283,305,or 307 this ma

why would anyone even bother to try to have a low compression sbc 305 sound like the old muscle cars, you might get it to sound similar with a new exhaust and a cam designed to give a lopey idle but the sound is about all youll get for the expense,
why not build a 10:1 compression 383 with a few decent components and actually produce some useable horsepower & torque easily doubling what the average 305 produces to match that sound?
really it doesn,t take that much, just some research, time, collect some parts and assemble them and swap engines some weekend, you might be amazed at what can be accomplished if your willing to persistently and regularly put $100-$150 into a long term project and hit some swap meets, do some research, etc.

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Re: if your thinking about building a 283,305,or 307 this ma

I've got a late 70s 305 marine longblock. It was rated at 225 hp stock. Here are the factory cam specs:


Two of the valves on the stock heads have rusted to the point where they would need to be rebuilt. The rest of the shortblock is good as is.

This engine was factory recommended top rpm at about 4400-4500 rpm for marine use.

I do have a pair of 187 heads off a '90 tbi 305, would these work for my application (of course I'd need the right intake) or should I look for a pair of 601s or 416s? I will be running a carb.

Would any of these heads allow my max rpms to be closer to say around 5,200 or 5,300 rpm? I'm just looking for a decent street cruising engine in a 3800 lb vehicle, certainly no drag racing or anything like that. Trying to keep costs down and use what I have in stock if possible.

read the links and sub links, theres a ton of related info.
obviously doing some detailed research into your personal combo and calling the cam manufacturer of your choice will help.
a cam with about 225 dur at .050 lift a 3000rpm stall converter and a 3.73:1 rear gear , 1.6:1 roller rockers the heads and cam linked too, and some decent tuning helps.

theres a HUGE bunch of related and useful data in the links so don,t just skim over them

viewtopic.php?f=50&t=9400 ... shaft.html

viewtopic.php?f=50&t=6624&p=20986&hilit=thinking+building#p20986 ... /overview/ ... /overview/

since your not looking to make extreme changes, Id just swap to a bit more agreasive cam and new lifters and valve springs and have the machine shop do some port and bowl clean-up on the stock heads, Id also find a used edelbrock or wieand high rise intake
those change should get you where your looking to be

if you want fairly in-expensive parts

read these links ... il&p=23759

add new lifters and new valve springs and this cam will easily allow 5500rpm in a 305

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yes you'll ALWAYS NEED to verify clearances carefully when assembling any engine and no, you can,t assume everything will fit just because its part of a component list thats suppose to fit correctly, simply because manufacturing is an imprecise process and mistake do get made occasionally!
what seems to be over-looked in many engine builds is simply the fact you'll almost always DEEPLY regret jumping into the engine build with both feet and waving your check book as you sink ever deeper into piles of parts receipts and machine shop bills, rather than stepping back with a legal pad, and a calculator and listing in minute detail exactly what you want to accomplish, and taking the time and effort too list and check out in detail what each machine shop procedure costs, why its required and how much each components costs, what your options are and how each component will add too or benefit the completed combo (or in some cases cause you time and grief)
stepping back and thinking things through in detail and listing the cost and potential problems and finding the solutions BEFORE you dive into the process may be a lot less fun, but in the long term its sure to cost less and result in a far better finished project!
always, if you deal with any machine shop, assume your dealing with a guy who really doesn,t give a crap,
and print out in fine detail , what you want done ,,EXACTLY....with specific dimensions and a diagram,
with ALL those dimensions printed boldly , try hard to get both a firm delivery date and a agreed upon total price
IN WRITING WITH HIS SIGNATURE, and several pictures of the parts and him holding the parts and a receipt
that the parts listed individually, to be worked on are in what ever condition they were in, TAKE LOTS OF PICTURES
this will be a minor P.I.T.A. but it will save you a whole lot of misunderstandings and arguments
never deal with any shop that says things like,
"come back next week I should get too it by then"
or "stuff like that generally costs about$300-$400, but I won,t know until I get into the project"
or won,t give a firm delivery date, price or sign a
receipt, or agree to a firm price... youll see why if you ignore this advice in spades
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