billybird

well i heard that the tpi is more restrictive on a 350 than(wich makes sense..since you feeding more cubes)...than on a 305 ci motor

i also heard that doing slp intake runners and such dont do much for a stock 305 even with headers

so my question is does the TPI on a stock 305ci motor(with headers) flow good enuff CFM

billybird

anybody?

five7kid

iTrader: (14)

It isn't so much the flow capability (although it is limited), it's the long runners that tune the engine to lower RPMs, like 4500 max. Shorter runners will help even a 305 with other changes like headers and cam.

Batass

Its not the worst part of the motor anyway. I think I'd concentrate on the heads first.

five7kid

iTrader: (14)

I wouldn't say that. Heads after TPI upgrades, exhaust upgrades, and cam upgrades.

Even then, you're only talking about port clean-up and perhaps 1.94" intake valves.

Batass

I thought those heads were really bad. Arent they swirl port? Or was that only tbi?

billybird

305 tpi heads are better than tbi heads(i think swirl ports)

but im asking this b/c i want to run 3.73 gears on a 305ci motor (since the tpi feeds the 305 better)

i get alot of ppl with 305 tpi say they run out steam at 5000 stock

five7kid

iTrader: (14)

TPI = 081 (or 416 in '85 & '86) heads, the "good stuff".

TBI = the dreaded "swirl ports".

Unless you do major mods to the TPI system, 3.73 gears will slow you down. Because power starts dropping at 4500 RPMs.

billybird

ill just manually shift at 4500 lol

Batass

Youre gonna have to shift pretty quick out of first gear.

Is it really 4500 for the 305? I know the 350s were 4500 but since the 305 is smaller, shouldnt peak hp be higher in the rpms? Especially with some bolt ons?

RED86Z28

The cam also factors in to the lower rpm power.

five7kid

iTrader: (14)

The factory put together a good butt-dyno combination. The cams used made great low-RPM torque in combination with the TPI system, which to the typical showroom test drive candidate translates to "powerful".

The runner length is what limits the TPI itself to 4500 RPMs, and that didn't change between 305 and 350.

Shifting manually isn't the issue. The transmission shift points were chosen as part of the butt-dyno package. If you do the 1/4 mile, you'll run out of RPMs with 3.73's before you run out of track.

billybird

so i should really get a HSR or bbk intake for 3.73?



can the stock TB be used on the HSR?

Batass

Yep you probably will run out of rpms since your car wont shift into fourth under WOT. 3.42 would probably be better, unless you swap the intake.

An HSR might be a little big for a 305. I dont think the tpi is all that bad on the 305, I would do other things first. The superram would probably be a good candidate, its a mix between the tpi and stealth ram.