I'm in the mist of building a 383 four bolt main. I am going to use cast heads with 2.02/1.60. A flat tappet w/214/224 @ .50 and .472/.496 with 1.6 rockers (mild cam to keep torque down low rpm's). I have 3.42s in back. I will have 1 3/4 headers with high flo exhaust. Everything else TPI is stock. SHOULD I USE THIS SETUP OR GO TO A CARB. SETUP? Will I be able to pass emissions with a carb setup. I believe this cam will be too small for a carb, is that correct? Any opinion is appreciated, or where to get the info I seek. I know a few of you did this swap. I'm not that far into the rebuild so switching to a carb is no big deal. I don't want to spend all this time and money on a tpi 383 set-up if it is just going to choke out the cubes. Also is keeping the tpi setup and burning my own prom, the way to go? or carb, please respond.

PS. Its an 85, and gonna be a street car, I want much low and mid-range torque. Also is 700r4 with stock converter and transgo.

 

1st, if they open the hood before you can pass emissions, the typical carb swap probably isn't going to cut it.

2nd, TPI on a 383 is going to require major modifications just to the TPI itself - ported base & plenum at a minimum, larger/shorter runners, larger TB, larger injectors, adjustable fuel press reg. But, that's the least of your problems. The '85 TPI was arguably the worst effort they made, and mod support isn't very good out there. Upgrade to a later MAF or SD system highly advised.

The other possiblity is to convert it over to a CC carb system. That was offered in '85, and would be emissions-legal if all of the required equipment was installed. '85-'87 factory carb'd donor car highly recommended. L69 air cleaner, emissions-legal headers, high-flow cat & cat-back absolute musts for air support, emissions-legality.

 

i am doing a 383 as well and i plan on staying TPI for a while... later i may go superram... but for now i am just gonna heavily modify an aftermarket base... runners, and ported pleneum!!!

 

That cam with a stock TPI is at the limit. A stock TPI on a 383 will max out at about 4500 rpm. That cam will make peak power around 5000 rpm. Minimum is to open up air cleaner which will make a big difference from 4000-4500 rpm. To get to 5000, you need work on the whole TPI system. If you are all street, and really want torque, it can be done. You may even be able to go down on the cam, but only a few degrees. When I ran Desktop Dyno using a 210-218 cam versus a 218-224 cam, the smaller cam made 30 ft lbs more torque at 2000, but only 10 ft lbs less at 4500. With your 3.42 gear, you may want to use 5000 or more rpm. In that case, open up the Tpi and use the 214-218 cam, or go up 4-6 degrees to the 218-224. Pushing up to 5000 or more, you would need to weigh the cost of a modified TPI, or a carb and how you will deal with the emissions. I chose the stock TPI and build my engine accordingly just so I could pass emissions, and not have to spend the big bucks modifing the TPI.

As a note, my 406 shifting at 4500 runs 10 mph faster that my wifes 350 shifting at 5500 over a given distance. So you don't always need the high rpm to win a race.