I have been getting so much conflicting info lately...

Could you please clarify what would be best to do first and how much the cost would be?

Porting of tb, plenum, runners, base

gears (what size?)

I have an 89 iroc that came with a 305 tpi, auto, 2.73 gears. Since, I have put in a zz4, built tranny w/1850 stall converter, headers, flowmaster, hiflow cat, etc and it currently runs 13.3 @ 106. I have always been told a 3.73 gear will give me a good half second...but I talked to a shop guy and said even with drag radials, it won't give me more than 2/10ths Help guys!

 

I JUST put 3.73's in my car, my advise to you is if you're staying 305 go 3.42's if you go 350+ go 3.73, the 305 just doesn't have the revs for 3.73. Also I've ported the plenum, didn't notice much if anything, i've heard others have lost bottom end. I'd say the base would be the best noticable power3, but wont help without the plenum being done.

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1985 IROC-Z, nuff said :P

 

Since the ZZ4 heads have good airflow I would start with a good cam. ( the ZZ4 cam is on the small side) Go with a grind that will work within the RPM range of the TPI setup. Look for one with duration @.050 lift 211-224 INT. and 215-228 EXT. with the highest lift you can get - LSA from 112-115.

The gears would need to be changed as well. I recommend a set of 3.42s -the 3.73s will only net another 10th, will wear your engine out faster and get poorer gas mileage. (I have a friend that just replaced his 3.42s for a set of 3.73s with slicks and didn't budge off of his 13.6s -He is going back to the 3.42s) Besides, the TPI will make plenty of torque to get you moving anyway.



[This message has been edited by whiteroc (edited June 27, 2001).]

 

Hey,
-I would port the heads (there is a tech article for porting 305 heads) Lets say $12
- port the plenum, get ported SLP runners, and get a ported Accel Manifold (I wouldnt worry about the Throttle body ... YET)$600 Also, Make sure to gasket match EVERYTHING
-Get the 3.42 gears (ALOT better on highway driving and gas mileage, prolly a lot more streetable to with/especially with the 305)$200

While doing this, I would look for a good deal on higher# injectors and read a lot into custom prom burning.... id put a 170 deg thermo $7.34 for my last one, TB coolant bypass $5.00 for 5/8" tubing, derale fan turn on 39.99 at pep boys(turns fans on at 170 instead of 238)
You might also think about getting an Adjustable Fuel pressure guage $50.00 to turn up the pressure at bit if you race it on tracks, then turn it back down.... Just a thought, maybe some aluminum roller rockers for the ZZ4 cam
Well this is plenty long, I Hope i helped,
Matt

 

After looking at ImportsRsloths post I don't know whether you have a 305 or a 350 -The ZZ4s are from what I understand, a crate motor 350 (I assumed that's what you had because of your E.T. and trap speed) If it is a 305 -that's one dang fast 305 car for how little you have done to it.


[This message has been edited by whiteroc (edited June 27, 2001).]

 

I just assumed it was a 305 with a ZZ4 cam... but his sig says it came with a 305 but put in a ZZ4, so im assuming thats the whole 350 crate motor. and that would explain the quarter times

 

lol sorry guys...I have the whole ZZ4 motor in there. You see...this is where I am getting the conflicting info: I was just told that the ZZ4 heads (L98 aluminum heads being the same I believe) flow horribly, but on this board just now, I was told they flow well. And speaking of gears, I have spoken with literally dozens of people all saying I will drop considerably in 1/4 time and that should be the first thing to go. But whoever said this was correct: I do have lots of torque downlow - enough to hit a 4.7 in the 0-60 category and this is with my drag radials not even being able to hook my 2.73's. Thanks so much for the info and help though guys...keep it coming!

 

The heads flow better if they are ported... as cast they are ok, but of course there is much better out there in the way of as cast heads.

If you are having traction problems, I would address those first before opening the hood, the last thing you need is more power when you cant even use it. I'd use a 3.23 or maybe 3.42 gear, and you should do something to help traction like lowering the control arm mount or an aftermarket torque arm setup or something along those lines.

 

yeah - I agree with madmax - If your having troubles hooking with 2.73's than 3.73's will be 5 times worse - probibly will raise your 1/4 times

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91 z28 lb9 5 speed - hooker 1 5/8 headers - high flow cat- full 3 inch exhaust - home made ram air - tpis airfoil - dual chamber flowmaster - Stage 2 Jet Chip and 160 stat - 8 mm Msd plug wires - 55,000 v hypertech coil/rotor/distrib. cap - Mac. White face gauges - lots of sound system crap...

 

I think you will see the most improvment with a new manifold base. There is not mutch room to port the stock base. The Edelbrock and LPE/Accel flow mutch better and have a bunch of room to prot. The TPIS manifold is just the Edelbrock ported for you. The plenum is easy to port out when you have the manifold off but porting the stock runners will not do mutch for you.

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1991 Z28 ZZ4 with LPE superram base, SLP runners, LPE 58mm T-body,Random Technology ramair,TES headers,24#svo injectors,ZEX nitrous,Walbro 255lph f-pump,Accel AFPR,Flowmaster catback,!cats,and mutch more.

 

One more thing the D port L98 heads flow fine but when you start making big power and need more flow the chamber size is a bit small but when I hit that point im going to send mine to LPE after there proting and valve job they flow better that and after market heads.

 

After reading this, I agree that your next mod has to be addressing the traction problem.

Check out this site. http://www.spohn.net/

As far as the heads go, LPE is going to be your most expensive route to getting the porting work done. Find a local machine shop that has a good rep for doing this type of work. It will be done faster and if any problems came up -they're right there. If you had any problems with LPE, you would be looking at some serious down time.

[This message has been edited by whiteroc (edited June 28, 2001).]