I have a 1988 iroc 305 tpi, looking for20 - 30 hp , whats a good way about. it exhaust dual cats/headers ? super chip ECM mod ?, cam ? fuel rails/intake ? , mod the heads , ....all of the above ? and pls no 350 swap advise , jus looking for a pick me up ..Thanks

 

No need for a "350 swap"... just get your 305 a "bore kit".

But even to take advantage of that, you need better exhaust; so I'd suggest starting there. Headers w Y-pipe, cat, & cat-back.

 

OK Thanks ,dual cats/headers a good start , what do you think the gain is 3 - 5 hp ? some say 20 hp ....but i dont think so

 

As long as TPI is on the motor, probably not any 20 HP.

8 - 10 is probably realistic if well-chosen.

But once you figure out that (a) a 305 and (b) TPI has got to go, at least you'll have the basis for moving forward, that you won't have to go back and re-do.

 

Thanks , yes exhaust will always be there , so i will start with that .dont think i need to go 350 ,its a convert,jus looking for a bit more pull ,also i am going to upgrade the tranny ,THANKS

 

if you just want "part time ummmpff" then just install a 100 shot dry nitrous system. Easy to install and easy enough to remove, if you ever want to sell the car.


if you want "all the time umppff" a Procharger or similar set up will really wake up that 305. a lot more $$ than the N20 kit even modest boost of 8 psi will do more than the nickel & dime mods.

Stay away from Turbos $$ all the extra piping, exhaust work, is pia on this chassis.

All the other crap (dual cats, headers, ecm chip etc) are time wasters on a OEM TPI motor what was tuned for optimum performance from the factory.
You will not see really big gains.


If you are willing to open up the motor a cam upgrade will be the best improvement for the $$ and make the biggest difference. but you have to be careful with cam selection.. because TPI is just that the intake ports are tuned to yield best TQ & HP at specific RPM range as dictated by the design of the intake runners..

That being said if you do a cam swap you may have to swap to aftermarket intake runners to increase the RPM range to work with new cam..

It gets to be pretty involved and not for the faint of heart. so
If you want to keep the car as original as possible you may even try lower rear gears just to get better acceleration.. You may have a 2.73 in there... a 3.73 will make a big difference.

 

Thanks for the info, i have 3;73 now , did consider a supercharger /procharger, is this a bolt on mod ,or do i have to continue with other mods such as fuel, cam etc..my budget is 4k ....

 

for your reference:

"The GM TPI system was based upon the flow characteristics of the lowly 305ci engine. These systems were flow-limited on a stock 350, let alone on a modified one. Mathematically (airflow at 28 inches of H2O x 0.257=HP potential), the airflow potential of a stock GM TPI can support approximately 350 horsepower on an optimized engine. If it is important to retain emissions compliance, ACCEL, Edelbrock, Ford Motorsports, or TPI offer high-flowing California Air Resources Board (CARB)-approved intakes that will support larger engine displacement and higher-flowing cylinder heads while keeping the feds happy.

New to the market for non-emissions-controlled applications are fuel-injected, single-plane manifolds from ACCEL and Edelbrock. These units offer runner lengths, flow capabilities, and tuning characteristics similar to their carbureted counterparts. "


"Factory port EFI systems allow OE engineers to drastically lengthen the intake tract to generate copious low-rpm torque, resulting in increased driveability and fuel economy. Most hot rods, though, are designed around horsepower, not torque. With torque defined as the amount of work that can be accomplished, horsepower is how fast that work can be done. Very simply, you need cylinder filling to make torque and rpm for power. Referencing the "Lengths to Various Points in Cylinder Head and Intake System" chart in the text, we can see the drastic runner-length difference between a GM TPI and popular wet-flow intake manifolds. Camshaft profiles that would work well with either a single- or dual-plane intake will not be effective with a long-runner TPI"

Read more: http://www.hotrod.com/techarticles/e...#ixzz2choxnYcT

 

4K may not cover a pro-charger install if you have a shop do it and the tuning, figure at least 8k but it will be done right.

Since you are only looking at max 350 HP with the OEM TPI system boost would be at safe level, I would say not more than 8 psi and you would not need an intercooler. Maybe larger injectors and fuel pump that's about it.


it is a straight forward bolt-on (alternator gets relocated) and pick up 50-100hp depending on how much boost. the nice thing is the power is always there when you want it.. N20 is the poor mans blower... but much less complicated to install.

You could do a small dry system. maybe cost 2-3k for a shop to do it.. a lot less if you do it yourself. But you are constantly refilling the 10# bottle... @ 3.50 - 5$ # = 35 - 50 $ per refill.

The benefits are it's cheaper (initial purchase), easier to install and remove if you sell the car.

At 50$ a refill that is a lot of N20.. so if you saved 3k versus buying a blower that is 60 refills or 600# of N20.

I can tell you from experience a 10# bottle does not last long. 3 passes at the track with a 125 shot when I had my 305 TBI. but it's cheap thrills if you take the time and do it right, it woke up an otherwise stock 305..
best mod for the money.. and when I sold the 305 to build a 383.. I kept the n20 kit for the 383.. just changed the base plate.. sold the kit 2 years for about half the price I paid for it new in 1999, so I got my money's worth.


http://www.nitrousexpress.com/chevro...s-systems.html

 

Hate to say the best mod you can do to a 305 is one you can remove when you decide to sell it
headers, cam, heads, intake are waste of time & $, Throw a 100-125 HP kit and laugh all the way to the bank.. it's the best mod for the money, IMHO.

A blower would be second choice because it cost a lot more, but again a great mod for the money.

Both are easily removed at a later date and easily used on a larger motor if you wish. Not so much if you get 305 specific engine parts.


My goal was to have a big cube small block only because of easy install into this chassis versus a BBC. but that was before I deleted the power brakes, power steering, A/C, etc etc.. so one day maybe just maybe when this latest BIG SBC is worn and tired I may build a BBC but that may not be for 10 years LOL.

Better yet when it comes time to refresh this SBC drop the compression and throw a F-2 pro-charger with intercooler and blow thru carb.