RallySportin'

I have a zz4 engine but it still has the stock tbi intake manifold and tbi. How much do you think this is holding me back from the engines potential, and how much would i gain from going to say a holley tbi intake and 670 tbi?

RallySportin'

Also another question. Do you think i would gain more from changing the intake or doing a full exhaust change? I still have complete stock exhaust on the car.

87Formula4bbl

It's probably holding it back a lot, first question. I'd say you'd gain a lot by going with a bigger TBI unit and better intake. And for the last question, definitely go with the exhaust, with headers.

JokerRS

Opening up the intake restriction won't do much good till you open up the exhaust with headers and 3" cat back exhaust. Do both or its never going to breath right. I'll bet good running LO3s are spanking you right now.

JokerRS

And after openning everthing up your going to need some major chip tunning.
Good luck!

RallySportin'

Well the car now can keep up with or beat my neighbors 86 z28 with a gm 350 HO crate engine. I was thinking before of switching to carb, because it might be more cost effective, but now im leaning more towards sticking with tbi.

IROCaholic

The stock tbi intake and exhaust on that zz4 is probably robbing you of a good 40 hp easily. If I were you I would invest in some headers, a high flow cat, and a 3 inch cat back exhuast. Youll see a huge difference with that. After that go with a good intake like the performer if you need to keep the egr or performer RPM if you dont need it(stay away from that holley tbi manifold ive heard its crap).You can use any carb manifold as long as you buy the tbi adapter that turbo city makes. Then top it off with the holley 670 tbi and you will knock a good amount of time off of your ets. Good Luck.

hot86z-28

yeah, i cant imagine how much more power you will gain with both proper air/fuel flow and exhaust flow. most guys after doing heads, cam swap have to install a bigger fuel system, so you are even ahead of them. i would probably agree with the atleast 40 HP and that's at the wheels would be my guess, your choking the day lights out of that 350, it's hard on a 305 much less the 350. you should get it dyno'd now and then dyno it again after you do intake and exhaust and see how much more power you gain, you will surely feel a SOTP difference and the gain on paper should be a big number too!

RallySportin'

I figured it was robbing me alot. So the exhaust should be the first priority then, and after that worry about intake?

IROCaholic

Yeah the exhaust is definetly going to be your first priority, if you do the intake first your engine is going to be able to take in more air but it wont be able to push it out through the stock exhaust. So if you do the exhaust first you will see bigger gains when you do the intake.

ShiftyCapone

iTrader: (7)

Do you have a high flow fuel pump? I would get that right away before you make the motor breath anymore. You better also get into chip tuning really quick or the car will never run right when you get it opened up. With the stock tune, TBI, intake and exhuast I bet that motor is only making 200hp. I put your power loss way higher than the 40hp most people are saying. This is the order of stuf I would do to prevent damage to your motor and to get the most out of it.

Fuel pump
Chip burning
Full Exhuast and more chip burning
intake manfold with larger TBI unit and inectors

As you soon as you open that motor up you are going to expose every weak link found on these cars all at once. You are better off buying all of the stuff and doing it at once.

Ronny

iTrader: (1)

weiand X cellerator 7547 single plane with adapter plate or Edelbrock TBI manifold and bore to 2.00 inch. i am going with 1st option since i already have the unit mounted and paid for. did Shifty mention chip tuning ??????

ShiftyCapone

iTrader: (7)

I most certainly did

RallySportin'

So if I were to change the exhaust to headers and 3 inch the rest of the way, it would run the same or worse before i did any chip burning?

ShiftyCapone

iTrader: (7)

It will still be way off but you will need the exhaust anyways.

1fast91rs

does anyone have the link to where i can buy a tbi adapter plate so i can use a carb intake?

hot86z-28

http://www.jegs.com/cgi-bin/ncommerc...69&prmenbr=361 i believe this is it, not 100% sure but i think this would work.

ShiftyCapone

iTrader: (7)

A quick search should get you plenty of part numbers. There are many adapters to choose from.

Ronny

iTrader: (1)

howell engineeering 1/2 inch not tapered. . holley 3/4 inch tapered.

gen3z

considering the factory TBI intake does not flow past 4200 rpm i would say that is the biggest restriction.

Z28GEN3

gees that reminds me i need to change my intake, all those mods and ill never feel them i cant figure out why the Edelbrock TBI intake is so much more then a standard carbed intake.

87Formula4bbl

Probably because they are more specific as to what bolts on to them. As in, the TBI unit as opposed to carbs being pretty much standardized on how they mount.