I have a 1989 IROC with a 305TPI and a 5 speed. I was wondering how much horsepower I would be at with the mods I have done so far and what should I do next to get some nice gains? I was thinking a ZZ-9 cam and some world S/R heads or maybee redoing the tpi system by porting it out and getting some new runners. Please tell me how much horse you think i'm around and the performance mods you have done to your 305 that gave you big gains.
List of mods:

KN filters
Modified MAF
Modified Airbox
Adj. pressure regulater
Underdrive pulleys
Hooker cat-back system
Hi-Flow cat
Edelbrock T.E.S headers

 

I'd say .... with what you got ....you are probably running around 14.6 in the 1/4 ....and maybe around 225-230 hp to the wheels . I say this because I know a guy with almost the exact setup ...... nut his is a 1990 ....and he pulled the number I listed to you.


.....with that cam ..... you are gonig to need a set of 3.73's .....
that is going to be your biggest seat of the pants feal . Port that plenum ..... so that TPI will breath a little higher into the rpm's . Are you dead set on the TPI .... or would you mind a Stealth Ram ...... it is your best bet . Those heads you mentioned ..... are one of your few options .....for the 305 . I too was gongi to do up my 305 ..... I bought all the stuff ....intake ...runners ....cam ..... gears .... then the 305 blew ..... so I had a L98 rebuilt for me instead .


Good luck ....I hope this helped

 

Yeah, I have also thought of changing the gears. Right now it has 3.08's. What would be better to get the 3.73's or something like a 3.42? My dad's 69 camaro has 3.73's in it and they seem to be a good all around gear even with the 4 speed tranny he's got.

 

Forgot to mention that I want to stick with the TPI because it seems to be a cheaper rought to go and the TPIS flow reports and dyno's show that it will make more than enough flow and horsepower for my application. For that set up I was thinking of a TPIS big mouth base, siameesed runners, and a ported plenum.

 

ok if you have 308's then go with 3.42's..that will be all you need.
big mouth base, big runners is the way to go...dont siamses them though..you dont have the cubes to get it going..

that zz-9 may be a little big, try there SP-L98 cam....that will be good for low low 13's, providing the heads are up to the task and your willing to drive it very hard...youd trap in the neighborhood of 107..if your brave enough to launch it HARD you could run a hi 12

ive always said "you wont run the time if your afraid to break it"


my G92 LB9 ran a 14.12 with a K&N, flowmaster, the EGR walls ground down and me driving it without fear of breaking it...(i did flatten out all the clutching teeth on my 2nd gear though lol)...it was the stock shifter also...

 

when I got my cam ( lil ZZ4 ) they recomended 3.73 for the 5 speed ....and 3.42 for auto .

 

the next thing u should do is do a lot of research...

 

Thanks for the info guys, The next thing I will probably do now is get a new set of gears then I have to decide if I want to get a new cam or redo the tpi system. Just curious but you say I shouldn't run siameesed runners because the small cubes of my motor wont be able to handle it?

 

I didn't know that was limited to cars above 350 ci


..... I thought it was just about makeing a LTR set up breath above 4800 ish ........

 

yeah its generally more beneficial to not have siamesed runners on a 305...because the idea of that is the same as a tunnel ram intake (obviously not to the same extent) it makes the plenum larger and therefore the runners shorter...the 305 would benefit more from longest runners possible (to a point)

 

GM High Tech siamesed the plenum with the SLP runners and saw a minamal gain. Not worth it if you ask me.

 

I have a similar setup to what you want. I have big mouth base, tpis runners, ported plenum, ported sr 305's, 3.73 edelbrock tes, dynomax catback. s10 tourque converter, trans go shift kit. Right now the car has the stock cam back in it b/c it had the hot cam and it was way too much for the 305. The car ran a 13.76 @100.35 mph with the above mods and stock cam. I am in the process of installing a zz9 cam and will post results when I get them. I talked with tpis about the sp-l98 and they said that since it was originally designed as a cheater race cam that the zz9 would be a better choice for a street driven car. They also said that with the sp-l98 I would need a 2800-3000 stall and with the zz9 you can get away with just a 3.73 gear

 

3.73's are to much for an auto tpi car...you will be faster with 3.23's...3.42's AT MOST