I have got an old stock exhaust manifold and played around with porting it out. OMG was there alot of metal in the way inside the ports! I never imagined there would be that much slop/weld slag/and burrs inside there. Has anyone else ported these out? and if so did you see any gains significantly from this? i ask because i sanded on the insides of the ports for over an hour with sanding toosierolls and want to know if its a waist of time or worth it. i know headers would be better but i dont really have $500 dollars laying around.... if i did i would buy another fiero instead thanks

Most of the guys say clearing out that area is good for an extra 10hp.

quote Originally posted by kellisor20: Most of the guys say clearing out that area is good for an extra 10hp.

WOW really! 10 HP, i wouldnt have thought that much. well with the amount i grinded out of there i should get at least 75HP gains

Haha yeah I have no idea what the guys at Pontiac were doing, when they decided it was fine like that. I mean seriously thats around twice the opening after you grind it out.

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86 2.8 gt

I remember seeing an article that showed 4 hp gain on average across multiple runs testing on a dyno. I don't remember seeing anything saying 10hp.

quote Originally posted by JazzMan: I remember seeing an article that showed 4 hp gain on average across multiple runs testing on a dyno. I don't remember seeing anything saying 10hp.

I remember 1fst2m6 testing it and got 8-9 hp and the bigger throttle body was a 4hp gain... Someone needs to test the Y-pipe restriction removal but that should be good for a few more hp ontop of the 9...

On June 5 1995 Lee Brown posted actual dynamometer results on racer@wasatch.com
I'll paraphrase what he wrote, to put it in context without the drawwings.

What to change:-
By porting the exhaust manifolds, Power was increased by eight horsepower at 5000/5500 RPM

Blueprinting the engine, Power was increased by three horsepower

Open exhaust, Power was increased by six horsepower at 4500/5500 RPM

High lift cam (opening and closing same as stock) Power was increased by fourteen horsepower at 5000 RPM

What not to change:-

Cam Timming, no improvement

Intake air system, we were surprised to find that removing the intake air cleaner and inlet system resulted in no improvement, Quote" the Pontiac engineers did a good job on these parts, because they work well even though they look to be restrictive"

Computer Chips: the leaner one resulted in a burnt piston during actual race conditions. the enrichment ones reulted in no power improvement but did cause the car to run out of fuel early (prior to a scheduled pit stop)

quote Originally posted by Tinkrr: On June 5 1995 Lee Brown posted actual dynamometer results on racer@wasatch.com I'll paraphrase what he wrote, to put it in context without the drawwings. What to change:- By porting the exhaust manifolds, Power was increased by eight horsepower at 5000/5500 RPM Blueprinting the engine, Power was increased by three horsepower Open exhaust, Power was increased by six horsepower at 4500/5500 RPM High lift cam (opening and closing same as stock) Power was increased by fourteen horsepower at 5000 RPM What not to change:- Cam Timming, no improvement Intake air system, we were surprised to find that removing the intake air cleaner and inlet system resulted in no improvement, Quote" the Pontiac engineers did a good job on these parts, because they work well even though they look to be restrictive" Computer Chips: the leaner one resulted in a burnt piston during actual race conditions. the enrichment ones reulted in no power improvement but did cause the car to run out of fuel early (prior to a scheduled pit stop)

good information!!! thanks!

..Tinkrr is correct this was a famous dyno test quoted on this forum for years
there have been suppose Dyno test that a ported manifold yelded only 2 horse power ,,Having eyeballed a few Exhaust manifolds,it is an easy 6 horse power ..if you smooth it out properly remove weld & smooth it and properly port the flange, that drops into the 2 rear ports you should realize 7 to 8 horse power,,The flanges are like dams interfering with flow,various test done in the 90.s & the above mention test show 8 horsepower gain..I was very precise doing mine and smoothed out the inner flaws that are hard to reach
Porting the DAM in the Y pipe will give another 1 to 2 horse power,,I have seen as high as 3 ,it depends on how much protrudes into the pipe ..
using a performance cat or using a straight pipe to replace factory cat is worth 1/4 to 1 HP TOPs
a Glasspack hurts performance ,but is recommended for the duke because the sound going thru the gears is heavenly orgasmic
Installing a dyno max super turbo in place of the stock muffler is worth 3 horse power
some people say other mufflers outperform the Dyno max,, the dyno test by HOT ROD,Carcraft & other magazines show the Dyno max to be a top performer and its cheap $48 to $60...

the best exhaust system for the Fiero V6 is ported stock exhaust manifold,with a stock ported Y pipe hooked up to a Borla cat back system,,but a used Borla system is $400.oo..The top V6 performer is the truelo header $600,00.
the Fiero store headers $595.oo but coated ,worth the money,tho horsepower is similar to ported stock manifolds.
west coast fiero also has some headers..
a little work on the exhaust system will produce 12 to 15 horse power a bunch for the 2.8 V6
no modifications will work well unless the restrictive exhaust system is improved
The improvement from these modifications changed the power band and my car pulls strong untill it would blow ,before it ran out of breath at around 5000 rpm.
port manifolds 6 to 8 HP
precision port of ex manifolds 8 to10 HP
port Y pipe,depends on blockage 1 to 3 hp
Mount performance muffler correctly 2 to 5 HP
the beauty of the ported upgraded exhaust system is the smoother power & pulling to max RPM way beyond the redline
even if you only realize 9 to 10 HP from exhaust modification,the engine will run cooler ,get better MPG & have more power ..
...The downside is exhaust manifold bolts and studs break you could have as many as 3 broken bolts,,& from experience at least one will be a real bear to get out,,It can be a real pain to remove the Y pipe also.No performance modification will yeld the quality gains ,not a cam, not a crank, not even headporting ,my fave
..I have 60 years as a gear head and have been a professional mechanic and at one time work for a Motorcycle racing shop,,I don.t know crap about Fiero,s but I know the above is as accurate as I can be??

[This message has been edited by uhlanstan (edited 02-22-2011).]

very well said my good man

If you are going to port them, do them properly!

Bolt them to a spare head and weld the flange to the pipe:


When you port the exhaust, make sure that you "port" match the intake - or at least port match to the exhaust gasket:

Your a little last to the game but good review... Many have ported and there is gain as said.
You have done the porting of the logs. (exhaust)

There is also the Y pipe as mentioned.

[This message has been edited by Dodgerunner (edited 02-22-2011).]

quote Originally posted by Dodgerunner: Your a little last to the game but good review... Many have ported and there is gain as said. You have done the porting of the logs. (exhaust) There is also the Y pipe as mentioned.

you have to cut the Y pipe in half to port it?

on the Y pipe, yes you have to cut it right about wherre the 2 pipes become 1. I went through all that (manifolds AND Y pipe) & brought the Y pipe down to the exhaust shop to weld it back together. would I bother again,? manifolds absolutely, Y pipe,Not a chance !

quote Originally posted by Lou6t4gto: on the Y pipe, yes you have to cut it right about wherre the 2 pipes become 1. I went through all that (manifolds AND Y pipe) & brought the Y pipe down to the exhaust shop to weld it back together. would I bother again,? manifolds absolutely, Y pipe,Not a chance !

my thoughts exactly

I brought my Y pipe to a machine shop and they cut it, grinded it and rewelded it for $75...then I sold it for $125 a couple years later...
Worth it? YES!
:-)

Ofcourse I had switched to Trueleo headers with 1 3/16" primaries and a full 2.5" exhaust by then...

Here's a hint on the Y porting. When you cut it open, cut it in a V pattern instead of straight across. This allows it to go back together in the correct orientation. Even being out 2-3 degrees on re-assembly can be a bear.

Arn

quote Originally posted by uhlanstan: The best exhaust system for the Fiero V6 is ported stock exhaust manifold,with a stock ported Y pipe hooked up to a Borla cat back system,,but a used Borla system is $400.oo..The top V6 performer is the truelo header $600,00. the Fiero store headers $595.oo but coated ,worth the money,tho horsepower is similar to ported stock manifolds.

The Fireo Store's Sprint headers still use a small dia Y pipe and the headers have sharp bends, - not equal lenght- still I would suspect they will flow a lot beter than a ported stock intake. One of our customer's reported a 30HP gain on the dyno with ours (trueleo) the Sprint's should get maybe 15 - 20HP? To my knowledge, West Coast Fieros no longer sells their FOCA headers.

Bottom line, any improvement to the stock fiero headers/Y pipes is worth doing, the stock system setup is real P.O.S. You can find better designs on cars form the 1920s and I'm not kidding. Cheepest way to go, port the stock headers and gut the cat! Still a bottleneck but you should notice the change. LOL, you'll hear it thats for sure.

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trueleo.com
RSpiderII@aol.com

WHAT ARNS85GT SAID
THE FIERO STORE HEADERS ARE SUPERIOR ABOVE 5000RPM
AROUND TOWN NOT MUCH DIFFERENCE BETWEEN A GOOD PORTED MANIFOLD & FIERO STORE MANIFOLD ,,I COVET COATED MANIFOLD
IS THE Y PIPE WORTH DOING ??DA, YEA,,YES ,YES,,IT IS NOT JUST HORSEPOWER THAT EFFECTS PERFORMANCE ,we have been spoiled by the vast array of performance part ,unfortunately the 2.8 V6 has few power parts available..
look at the blockage,,it is worth doing ,,the restriction will hurt performance
not one of the ported manifolds shown is properly done
to realize maximun gains you must make ports equal & round ,,floooooowing into the ports as well as possible, you make a template so each port is equal do it right?? the difference between 6 to 8 horsepower & 8 to 10
The truelo header is the best value for peak performance best by dyno test,far superior to any thing else available ..
a salute to truelo for his efforts