started with a stock 86 iroc tpi 5.0 auto, added paxton blower 6psi, re-built eng. .030 over, kieth blk hyp piston, moly ring, world sr torq head, mild edelbrock cam (grind very close to lt1 spec) roller 1.52 rocker. still have 19lb/hour bosch injectors and stock ecm/prom. i think i will need to upgrade injector size and burn custom prom, any suggestion on injector size?? good place to get custom prom?? or are there better options of aftermarket ecm/harness to replace factory ecm/harness??

 

If you are going to do all that, why not upgrade to a 350?

 

You can pick about any larger injector size and tune it to match since you already plan on doing a new prom.

What kinda power do you EXPECT to make, and then you can calculate from that?

(esp hp X .60)/6.4=lb rating.


for anyone else, the .60 is for boosted applications, n/a motors should be .50.

 

the factory tuned port intake was specialy designed for the 305 to achieve 125% volumetric efficiency, blown engines can achieve efficiency aproching 150%. runner size and length was "tuned" for this application, when the tpi 350 engines were made they used the same intake parts, the 350 tpi runs out of air at 4500 rpm due to size of runners, 305 tops out at 5250 rpm.

 

I think I have that book.

....er, anyhow, your best bet is always to go bigger. Certain people have certain goals, limitations, ideas, and they sometimes decide to keep the smaller motor. Keeping it numbers matching for example is one reason. -But as a general rule of thumb, there's no reason NOT to go with a 350. Keep in mind that even though it may rev higher, it doesn't mean it's gonna make more power.

.......but either way, once you throw a blower into the mix, all that fancy volumetric efficiency crap is out the window. The TPI was never designed for use with a blower. Sure, it'll work great, but now the TPI itself isn't a restriction like it is on a stock 350. A little more boost will get all the air in there that you need. ...and the 350 will still make more power!

 

you got my number! certain goals/ideas/limitations. i was more than happy with the street performance i got from stock 5.0 tpi blown. my first idea was 400 small block, or even 409, have heard that they actually run great with stock intake/injectors. had a hard time finding a good clean block, and from there i would have had to deal with cylinder head mods to fit the intake and cooling system problems due to siamesed cylinders. so i stuck with stock block, i know bigger is usually better but the stock package on this car was very well matched as far as power level to traction ratio (if there is such a thing) with mild suspension modifications i am able to achieve very good traction and i felt that more power would just equal more wheel spin. so i spent my money on good quality engine parts for the 305 to maximize its potential. volumetric efficiency improves on any engine that has forced induction. i wont claim to know exactly what it is but it has something to do with the amount of air the engine is capable of taking in. i do know that a normally aspirated factory production engine making over 120% volumetric efficiency in 1985 was a great achievment. and adding forced induction to that engine would improve efficiency even more