Ive got my 383 shortblock built with the cam, just gotta get everything balanced. I did a DD2K with the 383, comp XE274H, GMPP vortecs, DP intake, 750 carb and about 10.5:1 CR. It peaks out at just over 400 ft-lbs around 3500, but horsepower doesnt go over 400. It stays right around 390. This is with the stock 1.94/1.5 valves. Ive heard that porting and polishing the intake runners on a carb motor is kinda senseless cuz the rough runners help atomize the fuel and air, but port and polish the hell out of the exhaust. Can anyone ring in on this? I was thinkin about gasket matching the intake and slightly polishing them.

I also saw somewhere (maybe here) that for every 1 cubic ft of air, 1.7 cubic feet comes out, which is my I wanted to polish the hell out of the exhaust. Any pointers to getting over that 400HP mark??

I wanna go with the vortecs cuz Im gettin a hell of a deal on a set with less than 500 miles on em with manifold for 460 bux. So Im stayin away from goin with other heads if at all possible.

 

The amount of power you can make is limited to hhow much air your heads can flow. I have a flow sheet in front of me for a set of stock vortec 062 castings a buddy had tested and I had something to compare with the junk vortecs I got snookered into. In stock uun touched form they flowed 234cfm @28" at .500/.550 lift

Based off the math this would support 482hp

Formula as follows:

HP=.2575xCFM (at 28" of water) x number of cylinders

The cam/heads are the only thing that make power in an engine-or should say are the #1 and #2 factors in determing overall biggest factors that play into the equation. Start looking into a bigger cam or even a soild cam if you want some bigger number, but 400hp should easily be attaintable with a flat tappet hyd grind.

 

was that hp at the crank or the wheels? if it was crank thats real crappy.

 

lol i'm going to be getting atleast 450 horse power out of a plain old 350 vortec c hp. So goodness you better get more then 400 out of a 383 c hp.

 

400 hp should be easy out of a 383. When the vortec 383 crate engine came out about a year ago that is exactly what Chevy High Performance did with it. I would have to find the article but they took a stock crate engine which comes with a small hydraulic roller and vortec heads, 9:1 compression etc...and made 1 change at a time and dynoed each time, they easily surpassed the 400 hp mark with a cam change, intake, headers, rockers, etc.... step by step, it was a pretty good article, I think they stretched it out over several months as mags tend to do. They surpassed 400 hp without touching the cylinder heads.
400 hp with a 350 is easy nowadays with all the cylinder heads out there. A 383 should be cake. Larry.

 

yeah and they also had a smaller cam then i'm running. If you want to hit past 400+ head work is needed.

 

What is your exhaust system from headers to tail pipe including pipe sizes? Allen

 

well, Im runnin a flat tappet cam, so mine might not be as good as the crate 383. But Ill have to find out first hand.

As far as the exhaust, Im still debating on header primary size. I found some hedmanns full length 1 5/8, 3" for pretty cheap. But Im not sure, since Im not spinnin the motor over 6500, if I need to find me some 1 3/4" primaries. Mufflers, either hooker aerochamber or dynomax/magnaflow. Still debatin on that too.

 

The exhaust might be the reason you are not over 400HP. You need a good system. It should be one of the first upgrades. Be sure to use mandrel bent pipe. Allen

 

For those small heads DO NOT go over 1 5/8" primaries, you will lose power. The Heddman LT's will have NO PROBLEM supporting the power you want to make and then some.

 

The thing I noticed about DD2000 is that it doesn't seem to rate a 383 any higher than a 350, given the same parts. I know power is all about the air flow through the motor, but a 383 vortec is going to make big power with a large cam, and 750 carb.

 

The really wierd thing about going from a 350 to a 383 with mild(er) street parts is the fact that you should pick up the 10% increase in torque due to the increase in size, but not necessarily HP due to the peak being at a lower rpm. Total power "under the curve" should increase, which will help out acceleration quite a bit. Essentially you need to "size up" a cam for a 383 over a 350, but usually the same heads and intake will work just fine.

This is not an exact science.....