inj housing porting without headers - ZR-1 Net Registry Forums

mike100 · 02-18-2011

Is there anything to be gained by induction improvements while retaining the factory exhaust manifolds?

The logical mod progression is to do the chip/exhaust, headers/ intake porting, followed by head/cam/ displacement increases. I can't do that as easily in CA- not because of getting caught, but because of switching parts back every two years.

I have a B&B catback, but I'm looking to tone that down as well if I can find a set of factory pipes to purchase/modify. May just have a custom 2.5" with a resonator made if it can be done cheaper than a Corsa... I feel that some more midrange punch could be gained by ditching the 3" x-pipe drone special this car has.

somewhat related: I actually don't know if my prom cal is stock either, but it revs to 7400 (indicated) and the skip-shift is not functional.

LGAFF · 02-18-2011

Yes, I did porting for a car and it gained 25rwhp, with stock manifolds

sammy · 02-18-2011

you can pop the prom out easy enough and see if its got a aftermarket tuner tag on it .you might have a tuner prom .you are right about the exhaust 3in loses low end unless you have a fully ported motor with headers . i have a ton of extra exhaust systems flowmaster cat back, corsa cat back, borla mufflers only, a 90 stk exhaust and a 91 stk exhaust pm me if you might be interested in anything above . rick hipsher ported his top end inj and plenum ,i believe he made 20+ rwhp with stk exhaust and no dyno tuning . maybe some of the calif. guys with headers will chime in on how they keep them .

sammy · 02-18-2011

when i was in ca i live in inyo county, the only county in ca that doesnt have to do smog testing .

GOLDCYLON · 02-18-2011

Yes porting will improve performance. Next logical progression is long tube headers. It a no brainer while you are there already mod and does not affect the car to detract visually in any other way. It is an unseen mod with the exception of increased performance.

mike100 · 02-18-2011

Quote:

Originally Posted by sammy

you can pop the prom out easy enough and see if its got a aftermarket tuner tag on it .you might have a tuner prom .you are right about the exhaust 3in loses low end unless you have a fully ported motor with headers . i have a ton of extra exhaust systems flowmaster cat back, corsa cat back, borla mufflers only, a 90 stk exhaust and a 91 stk exhaust pm me if you might be interested in anything above . rick hipsher ported his top end inj and plenum ,i believe he made 20+ rwhp with stk exhaust and no dyno tuning . maybe some of the calif. guys with headers will chime in on how they keep them .

factory tag (the second calibration listed for '91- I forget the exact one, but it has an 'X' in it). I definitely want to talk about pipes. I understand the early resonator is restrictive though. From my previous experience with C4 resonance, only the stock muffler and somewhat with a generic turbo muff, are going to have minimal drone.

mike100 · 02-18-2011

Quote:

Originally Posted by GOLDCYLON

Yes porting will improve performance. Next logical progression is long tube headers. It a no brainer while you are there already mod and does not affect the car to detract visually in any other way. It is an unseen mod with the exception of increased performance.

If I have to get back into it for anything else, I want to be prepared to do what I want, budget depending. It sounds like a vicious cycle- may as well do wires, but then you should get new coils too, and if you got injectors, may as well pull the housings off to get them worked- hehe...It's not too hard to remove the plenum.

I'd be happy with late model LT5 power with a smart combination of things plus the chip.

Locobob · 02-18-2011

Here is a 91 I did a mild port on, before and after. No headers, no tune, just cat back.

Aurora40 · 02-18-2011

Does the skip-shift light still come on? If so, it's probably unplugged vs a chip. Tach is hard to say, because so many are not accurate.

And yes, porting with stock manifolds is worth it. I did headers last. Headers have the most downsides in terms of a louder, rattlier car, and of course it's harder to pass a smog test.

GOLDCYLON · 02-18-2011

Quote:

Originally Posted by Aurora40

I did headers last. Headers have the most downsides in terms of a louder, rattlier car, and of course it's harder to pass a smog test.

100% correct even with Hi-Flow cats.

02-18-2011	#1
mike100 Join Date: Feb 2011 Location: San Marcos CA Posts: 1,802	inj housing porting without headers Is there anything to be gained by induction improvements while retaining the factory exhaust manifolds? The logical mod progression is to do the chip/exhaust, headers/ intake porting, followed by head/cam/ displacement increases. I can't do that as easily in CA- not because of getting caught, but because of switching parts back every two years. I have a B&B catback, but I'm looking to tone that down as well if I can find a set of factory pipes to purchase/modify. May just have a custom 2.5" with a resonator made if it can be done cheaper than a Corsa... I feel that some more midrange punch could be gained by ditching the 3" x-pipe drone special this car has. somewhat related: I actually don't know if my prom cal is stock either, but it revs to 7400 (indicated) and the skip-shift is not functional.

02-18-2011	#2
LGAFF Join Date: Mar 2007 Location: Crystal Lake, IL Posts: 7,194	Re: inj housing porting without headers Yes, I did porting for a car and it gained 25rwhp, with stock manifolds __________________ LGAFF 90 #966-150K miles-sold 92 #234-sold 1987 Callaway TT #17 1991 ZR-1 #1359

02-18-2011	#3
sammy Join Date: Jun 2010 Location: back in lone pine Posts: 591	Re: inj housing porting without headers you can pop the prom out easy enough and see if its got a aftermarket tuner tag on it .you might have a tuner prom .you are right about the exhaust 3in loses low end unless you have a fully ported motor with headers . i have a ton of extra exhaust systems flowmaster cat back, corsa cat back, borla mufflers only, a 90 stk exhaust and a 91 stk exhaust pm me if you might be interested in anything above . rick hipsher ported his top end inj and plenum ,i believe he made 20+ rwhp with stk exhaust and no dyno tuning . maybe some of the calif. guys with headers will chime in on how they keep them .

02-18-2011	#4
sammy Join Date: Jun 2010 Location: back in lone pine Posts: 591	Re: inj housing porting without headers when i was in ca i live in inyo county, the only county in ca that doesnt have to do smog testing .

02-18-2011	#5
GOLDCYLON Join Date: May 2007 Location: Peoria, AZ Posts: 9,155	Re: inj housing porting without headers Yes porting will improve performance. Next logical progression is long tube headers. It a no brainer while you are there already mod and does not affect the car to detract visually in any other way. It is an unseen mod with the exception of increased performance. __________________ GOLDCYLON - 91 ZR-1 #2014 GOLDCYLON - 90 ZR-1 #2794, 4L60e (Formerly Schrade's) GOLDCYLON - 11 CTS-V Arizona State Director 91 WHITE/BLACK #2014. 380 P&P&PCed,Ported Heads, Jeal Long tubes, Corsa Exhaust/FIKSE FM-5s /LED TLs, LED Headlights, Front Wilwood 6 piston narrowlite calipers and rear Wilwood caliper street shop mod,CNCed Coolant Pipes,TPI Cvr,Filter cover,Stainless Bolts, DRM/DOM PROM /ZFDOC mod build #102,DRLs,BMAD with stainless Debris Screen,Coplan Air Blaster, Pioneer APP Radio 4,Brey-Krause HB,Sub Bar,Fire extinguisher seat mount,DRM Coilovers,LEDs everywhere,Compass mirror (orange),V1 DIC hidden display, Homelink sun visor, Carbon Fiber top x3 and APSIS Carbon Fiber interior, APSIS CF Steering Wheel/NAPA Leather, Banski trailing arms, Guldstrand front suspension,urethane bushings from Prothane (total suspension) ZFDoc drive shaft safety loop, raptor shift light (orange),AO engineering louver front plate, Console seat cushion, 96CE seats with black custom Sheepskins, ss billet catch can,Viper remote entry/alarm,Cragar Rear Louvers,LED side louver lights, Dewitts Radiator with SPAL fans and a Woods 160 T-Stat 90 RED/BLACK #2794. 4L60e Automatic Stage V by RPM Transmission, TCI Dedicated TCM, OBX Stainless Headers, Corsa Exhaust, SAN Secondaries and Haibeck PROM, Exotic Muscle Coil overs, LED Interior Lights, LED Tail Lights, LED Headlights, 94 Sport seats with black custom Sheepskins , Cragar rear louvers, GS Front calipers, Banski Trailing arms, APSIS Carbon Fiber steering wheel, Front and Rear Baer Eradispeeds, DRLs, Guldstrand front suspension,urethane bushings from Prothane (total suspension), Dewitt's Raditor with Dual SPAL fans and a Haibeck 170 T-Stat 11 RED/GREY CTS-V

02-18-2011	#8
Locobob Join Date: Jan 2004 Location: Portland, OR Posts: 1,057	Re: inj housing porting without headers Here is a 91 I did a mild port on, before and after. No headers, no tune, just cat back. __________________ Robert ZR-1 Net Registry Oregon State Director 91 ZR-1 #431 Black/Black LPE 368

02-18-2011	#9
Aurora40 Join Date: May 2005 Location: Leesburg, VA Posts: 2,713	Re: inj housing porting without headers Does the skip-shift light still come on? If so, it's probably unplugged vs a chip. Tach is hard to say, because so many are not accurate. And yes, porting with stock manifolds is worth it. I did headers last. Headers have the most downsides in terms of a louder, rattlier car, and of course it's harder to pass a smog test. __________________ Bob Saveland Former owner of #2517 [IMG]http://a.random-image.net/aurora40/vette.jpg[/img]

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