383 power estimates

[lisiecki1]

I know some of you guys have quite a bit more experience than i do with engine building, so I was wondering what you would estimate my 383 will be putting out.

Here's the build:

.030 over 383

10.7:1 compression (dome tops with valve reliefs)

84cc heads with 2.04/1.96 valves (if i remember correctly) ported and polished

standard stroke

double roller timing chain

crane solid lift cam 304/304 .556 lift 108centerline (if i remember correctly - the card is at the house)

1.5:1 aluminum roller rockers

edelbrock tm7 intake (looks similar to torkerII)

currently edelbrock 750 carb with manual secondaries and electric choke and 1" phenolic spacer, but i'm sure i'll have to go bigger (850-900?)

mopar performance electronic distributor with either orange box or msd6al (already have the orange box)

accel shorty spark plugs (to clear headers)

headers are 1-7/8 to 3-1/2 collector block hugger style

desktop dyno (which estimated dads 426 pretty damn close) came up with a peak HP of 496 and over 500 torque with the 750 carb, through full exhaust

also, i want to run full 3" exhaust with x pipe, would 2-1/2 be better?

[Rolling_Thunder]

my dyno program that is usually within spitting distance says 507hp @ 7000rpm and  443tq @ 5000rpm   

[lisiecki1]

thank you rolling thunder....would you mind checking it with 850/900 cfm carb and see what happens with the numbers?

[firefighter3931]

I really don't place a lot of value in simulator programs....most are based on the SB Chevy model. Without knowing what the cylinder heads flow...it's a shot in the dark at best when trying to predict power output. 


The cam specs are ambiguos at best....what's the duration @ .050 valve lift ? Split pattern grind ? Installed centerline ?


This looks more like a race build and will require a loose converter and deep gears to work properly on the street. I doubt it will be happy on pump gas either and if you have power brakes it will not make enough vacuum to run the booster. You will definately need an HP style carb with 4 corner idle and an agressive fuel curve if you hope to have a chance tuning this engine to function well on the street.



Ron

[lisiecki1]

I really don't place a lot of value in simulator programs....most are based on the SB Chevy model. Without knowing what the cylinder heads flow...it's a shot in the dark at best when trying to predict power output. 


The cam specs are ambiguos at best....what's the duration @ .050 valve lift ? Split pattern grind ? Installed centerline ?


This looks more like a race build and will require a loose converter and deep gears to work properly on the street. I doubt it will be happy on pump gas either and if you have power brakes it will not make enough vacuum to run the booster. You will definately need an HP style carb with 4 corner idle and an agressive fuel curve if you hope to have a chance tuning this engine to function well on the street.



Ron

Thanks Ron,

I know its radical for the street, but 90% of it was there when I bought the engine, so I'm just running with it.  It came with a split duration 312/322 cam originally, but I opted to put one of dad's cams in it instead (i believe it's a factory '69 HEMI grind, if that helps) I'll post the full cam specs when I get home and pull the cam card.  I'm also planning on running an electric vacuum booster for the brakes.  Currently I'm leaning towards a 3000 stall, although PTC told me that I should run a 26/2800 with what I've got so far.

Randy

[oldschool]

 really don't place a lot of value in simulator programs....most are based on the SB Chevy model. Without knowing what the cylinder heads flow...it's a shot in the dark at best when trying to predict power output. 

  could not have said it better

[lisiecki1]

okay, here's the actual cam specs......

it's a competition cam

intake lift .557

exhaust lift .541

duration at a tappet lift of .020 intake 304 exhaust 304

valve timing @ .020 intake open 44 btdc    close 80 abdc

                         exhaust open 80 bbdc    close 44 atdc

duration at .050  intake 266 exhaust 266

lobe lift              intake .356" exhaust .356"

cam lobe center separation 108 deg.

install cam at 108 deg. atdc

[firefighter3931]

That's an awefully big cam for a street type build 383. The 304*@.020 is the "advertised" duration number.....that cam will have similar idle quality to the MP 509 hydraulic grind....which is very "dirty" even in a 440 cube build. It would be quite a chore to get it to idle in a 383 !

The 266@.050 defines the powerband....in a 383 cube build it will be narrow. Torque peak will be 5000+ rpm and horsepower in the 7000+ range. The shortblock would need to have some high end parts and balancing to let it rev to the power peak and still live. 

To make this work it would need a 5000+ stall and 4.56 gears. Not exactly a street friendly combination. Honestly, that cam is better suited to a race 440 or street/strip 500 stroker. 


I don't know what your plans are for this car but this is not a cam i would consider for the typical street/strip 383-440. Maybe if you were planning on a 500in stroker it could work but even then you would want to match up the stall speed and gearing for best performance. 




Ron

[Rolling_Thunder]

I usually dont put too much faith in dyno programs either but this one I've had actual dyno results and they are all pretty close (within 5% usually) so - I would consider it a good guess....     headflow would help for sure though

And that cam is indeed HUGE for a 383

[lisiecki1]

thank you all for your help and information!

it seems inevitable that i'll have to change the cam at some point, so with my current engine specs what grind would ya'll recommend?

also, if i put in a hydraulic cam next time around, will i be able continue use of my adjustable roller rockers, or are we talking about a complete valvetrain swap?

randy

[firefighter3931]

Randy, a few things need to be cleared up before a cam recommendation ;

(1) what rear end gear are you wanting to run with this car
(2) will it be seeing lots of hwy use
(3) street/strip or mostly cruiser type build

it seems inevitable that i'll have to change the cam at some point, so with my current engine specs what grind would ya'll recommend?

The answer to that question will largely depend on your responses to the questions listed above 

also, if i put in a hydraulic cam next time around, will i be able continue use of my adjustable roller rockers, or are we talking about a complete valvetrain swap?

If you switch to a hydraulic cam you would need different pushrods but the adjustable rockers can be reused.....no problem.


* has the static compression ratio been verified ? 10.4:1 with iron heads can be a problem if you plan to run this engine on pump gas.



Ron

[lisiecki1]

Randy, a few things need to be cleared up before a cam recommendation ;

(1) what rear end gear are you wanting to run with this car
(2) will it be seeing lots of hwy use
(3) street/strip or mostly cruiser type build

it seems inevitable that i'll have to change the cam at some point, so with my current engine specs what grind would ya'll recommend?

The answer to that question will largely depend on your responses to the questions listed above 

also, if i put in a hydraulic cam next time around, will i be able continue use of my adjustable roller rockers, or are we talking about a complete valvetrain swap?

If you switch to a hydraulic cam you would need different pushrods but the adjustable rockers can be reused.....no problem.


* has the static compression ratio been verified ? 10.4:1 with iron heads can be a problem if you plan to run this engine on pump gas.



Ron

The rear end is 3.23

i may go to a 3.55 or 3.91 when i can afford a GV unit

i am planning on a little highway use, but no cross country stuff

it will see a little strip duty...but mostly i'll be cruising

I figured the compression myself a number of years ago with the assistance of a Federal Mogul Compression Ration Worksheet, and no, it hasn't been verified by anyone.

[firefighter3931]

If it were mine i'd be pulling the heads and doing some investigative work. If the compression ratio is too high you should make adjustments before putting this car on the street. A little detective work will go a long way towards building a reliable and enjoyable engine combination. Most guys prefer to run pump gas on the street so doing your homework will pay dividends in the long run. 



Ron