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Super Moderator
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8,488 Posts
Discussion Starter #1 (Edited)
just some info
theres two basic bore sizes, 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 boreing 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 oversized (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
406ci
AFR 210cc Competition Package
10.1
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
383ci
AFR Street 190 Cyl. Heads
9.5
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 thats been ballanced 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 ROTATEING ASSEMBLY KIT and get a FLUIDAMPER harmonic ballancer and if possiable have the INTERNALLY BALLANCED STYLE KIT, as it has FAR LESS stress at high RPMS
heres some places to look

http://www.scatcrankshafts.com/

http://www.flatlanderracing.com
(stroker kits)

http://www.strokerkits.com/383.htm

http://www.midwestmotorsportsinc.com/

http://www.competitionproducts.com/page88.html

http://www.herbertperformance.com/

and also remember the cylinderheads, cam, and compression ratio must match your intended hp goals
 

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Obsessive Customizer
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535 Posts
Yeah, I did a 400 but decided to heck with the computer so I added two 750 carbs for an extra touch. Gas you say? I am currently investing in a gas station to put on my front lawn - any ivestors? LOL
 

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DC Crew
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4,823 Posts
I'd go with the 383, saves me the cost of shipping a 400 block overseas :surprised and that's all the power I want or need.
 

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Super Moderator
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8,488 Posts
Discussion Starter #4 (Edited)
http://www.herbertperformance.com/
Phone
(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 ballanced 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)
(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 ballancer
race quality flexplate
ARP oil pump drive shaft
have assembly ballanced either by them or locally

it might help a great deal if you understand that runner length and cross section area have a great deal to do with where the cylinder fill efficiency works best in the engines rpm range, on a 350-383 engine that runner length measured from plenum to the back of the intake valve distance should be about 10"-12" and the cross sectional area should be about 2.3-2.7 sq inches, but remember the DYNAMIC compression ratio,cam timing,(LSA/OVERLAP)displacement, stroke,rod length and exhaust header design also must match that same peak effective level for the best potential power! making the runners longer or the runners smaller in cross section LOWERS THE TQ PEAK, making them slightly shorter or larger in cross setion tends to RAISE the torque peak RPM

Runner lengths
Stock tpi manifold 8” runners 11.25”, cylinder head 6” total 25.25”
Accel super ram manifold 8” runners 7” cylinder head 6” total 21”
Holley stealth ram manifold 6.26” ” cylinder head 6” total 12.26”
Edelbrock performer RPM runners 6” ” cylinder head 6” total 12”
Edelbrock vic jr , runner length 5.5” ” ” cylinder head 6” total 11.5”



the exhaust primairys should be at least 18" long and not more than about 32" long before entering the collector and 1.625-1.875 in dia. the collector should be about 15"-22" long and about 2.75 in dia.

you might want to play with these calculators

http://www.newcovenant.com/speedcrafter/calculators/runnerarea.htm

http://www.newcovenant.com/speedcrafter/calculators/intake.htm

http://www.newcovenant.com/speedcrafter/calculators/intakecfm.htm

http://www.rbracing-rsr.com/runnertorquecalc.html

http://www.nightrider.com/biketech/calc_exhaustlength.htm

http://www.btinternet.com/~mezporting/exhaust_length.html

http://cochise.uia.net/pkelley2/Overlap.html

http://cochise.uia.net/pkelley2/DynamicCR.html

http://www.engr.colostate.edu/~allan/fluids/page7/PipeLength/pipe.html

try for about 4500rpm-4800 torque peak, a 7.8-8.2 dcr, and

these are the valve timeing overlap ranges that are most likely to work correctly
trucks/good mileage towing 10-35 degs overlap
daily driven low rpm performance 30-55degs overlap hot street performance 50-75 degs overlap oval track racing 70-95degs overlap dragster/comp eliminator engines 90-115 degs overlap
but all engines will need the correct matching dcr for those overlap figures to correctly scavage the cylinders in the rpm ranges that apply to each engines use range

for a 383 street strip engine that will be about a 190cc -210cc head,a tunnel ram or stealth ram intake and about 11.1 CPR and a cam in the [email protected]@.050 intake duration range with about .600 lift and a 108-110 lsa as a good compromise for max hp but a slightly milder 230-240 duration @.050 lift and a slightly wider LSA in the 112-114 range will make the car much easier to drive, increase the torque rpm band significantly and only reduce peak hp slightly
look at this dyno chart, its a 350 with a crower #00471 cam , it makes 530ft lbs of tq and would make 450hp easily if it did not have a restrictive exhaust

 

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Ti each his own. I went with a 389 LT4 for mine. Bored .065 over to unshroud the valves better... I stayed small for higher rpms. 7600 rpm redline. Makes 464 RWHp @ 6900 rpm. It makes 440rwhp + from 6600 all the way to redline (7600). i think that will let me abosulutely SMOKE a low revving bigger cube motor.
just my opinion.
:cheers:
 

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Super Moderator
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8,488 Posts
Discussion Starter #6
FIRST LET ME SAY ,GOOD JOB ON THAT lt4

NOW TO ANSWER YOUR QUESTION, YES YOUR CORRECT THAT lt4 WILL MAKE MORE HP THAN THE average LOW RPM BIG DISPLACEMENT SMALL BLOCK THAT ONLY SPINS UP TO ABOUT 6000RPM,
but, HERES A SMALL BLOCK
BIG DISPLACEMENT ENGINE
THAT WILL NOT NEED TO EVEN HIT 6000RPM TO EASILY KEEP UP WITH AND PASS THAT lt4
http://www.theengineshop.com/content/pg06.pdf

HERES SOME INFO ON A 401 SMALL BLOCK THAT WILL ALSO GIVE THAT HIGH REVING lt4 A GOOD RUN,
http://www.airflowresearch.com/articles/article31/page2.jpg
 

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38 Posts
i just checked those links.... i surrender!! :laughing:


I agree with you about the bigger displacement though. Especially for 1/4 mile machines.

I want my car to be a 140+mph missile... at those speeds i need rpms and high hp.


In the end i think its a sum of all the parts that will decide output almost as much as displacement itself. (think that makes sum sense)

:cheers:
 

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5 Posts
Just a thought, but a mild short block and heads with the proper cam timing can make serious power at only 6.5 to 7 lbs of boost. A this boost levels an intercooler is not necessary, heads don't need a lot of porting or valve spring, the short is ok as is (ARP rod bolts or equivalent are always a good idea) if it has Hypereutectic pistons or better. And the best part is that it dosen't take a lot of RPM to build 1.3 to 1.5 HP per cubic inch. The down side is that a blower systems (Vortec, Powerdyne, ATI, etc) are not cheep and must be done all at once as opposed to a bit at a time (manifold, cam, headers, etc) also premium fuel is a must. A blown motor will give good mileage when not under boost and is as driveable as a stock engine until you lean on it , then the fun begins!
Ian
Remember! The only replacement for displacement is technology!
 
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