89IrocZ350TPI

Hey guys I thought Id give a review on which BOLT ON parts yeild the best performance gains for the L98 motor. If you want to make a top 5 list as well that would probably help memebers who are looking to improve the performance of their L98.

1. 3.45 Gears- Most L98s came with highway gears such as 2.77's or 3.27's. IMO 3.45's are the best gear for TPI because it keeps the car right in its powerband. I gained .5 just from this gear swap. With the 2.77's I could spin pretty good, but with the 3.45's I can spin the tires off the car if I wanted to lol. The only let down is you will have a decrease in fuel economy but our cars are not exactly made to get good gas milage. Also if you have a 9 bolt the parts will be much harder to come by.

2. Headers- A close contender for the number one spot. TES headers gave me the biggest horsepower gain out of any other mod. If you are going to stick with your TPI setup go with shorty style headers since TPI is not designed for high rpm performance. Expect a gain of 20 horse power, and a much louder car!

3. Cat-Back exhaust system- The stock exhaust on the L98 is crap. A 3.5 inch catback either flowmaster, borla, or mufflex, will add around 15-20 horsepower when installed with a higher flowing cat, along with a much meaner sounding car.

4. Runners- A good set of aftermarket runners should net around 15 horsepower. A few good choices are TPIS,Edelbrock, or SLP. For even better gains you can have them ported as well.

5. Intake manifold- The stock Intake on the l98 is very restrictive. An upgrade to an after market manifold should free up around 20 horses. I actually noticed a deeper sound to my car after I installed an Edelbrock performer.


How does my top 5 look???

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1989 Iroc L98
13.296 at 101
http://www.cardomain.com/ride/2231640

KamikazeIroccy

currently in the process of changing everything mentioned
I would agree with this list!

APACHE JOHN

If you're going with TES headers I wouldn't bother. There's lots better headers for the same money.

WicketMike

ill be saving this. good list for the new GTA i just bought

89IrocZ350TPI

If you guys need any input on other bolt ons my car has pretty much full bolt ons. So I can give you a review.

__________________
1989 Iroc L98
13.296 at 101
http://www.cardomain.com/ride/2231640

Brisk

great list, I think those are great for the top 5 mods list - in any order.

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- Chris -

Check my vBGarage for Mods

billybird

not even for the l98's...this is good for all TPI cars..good list bro

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TPI LB9
10 Bolt Posi
Header's(june14)
TCI Breakaway 2400 stall(july14)
tranny cooler
Hankook
89 Formula WS6

motorheadmike

5. LS1/6
4. LS2
3. LS3
2. LS7
1. LS9

L98 lack of performance problem solved.

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squeeezer

i agree with all but #4
bigger runners only for aftermarket heads
those stock runners will outflow stock heads
i would swap it with a shift kit or stall converter

a mack6

I would also have to agree and I don't even have an L98.

89IrocZ350TPI

Yes you would get better results from an LSX swap. However that will be a bit more expensive. A 2800 stall would also be another great mod. I have seen claims of .1-.3 reduction in ET. Could be #4 or #5. My list is only my opinion, and I still have the stock converter so I cant speak from experience.

__________________
1989 Iroc L98
13.296 at 101
http://www.cardomain.com/ride/2231640

H8U666

This may be a given... but a good tune-up and replace any old sensors would only boost the above mods. To put it into perspective most of the parts on our cars have been in regular duty since Ronald Reagan was president. Just took my original EGR off a week ago and it was atleast 30-40% clogged with carbon build-up.

toxik IROC

hmm

fun Pain

focusing on money...

1. Nitrous Oxide (turbo if you can d.i.y, harder but you won't need #4)
2. Gears (with somesort of posi)
3. 2400 to 3200 lockup stall or a good clutch
4. full length headers (unless slammed, SLPs) cat-back are a must unless you still are running the 20yr old factory stuff...
5. Heads/cam

6>>>because you will need these, after all that (Slicks, D.O.T.'s, or Drag Radials)


but if you do this list there won't be any worry about our LSx buddies...

if they do this I am sure they will be more powerful, but with a whole lot more money...

if you think about this, for a sec.... that is all that is needed on every GM... (except maybe the LS9 mentioned)

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[

Ram Air Firebird Formula 350 1987
Now Powder Coated Holley Stealth,
CC306 Cam (236 int./242 exh.),
Ported/gasket matched Factory heads with studs,
1.43 987's,
no a/c, no smog,
3.5"cutout, American Thunder 2 Stainless catback,
Ostrich repinned 165 to 730...code 59,
PLX Wideband,
HX50W Holset, monster SX pump,
42lb injectors, FMIC, FS BOV [[Tuning in progress]] and I still have my Nitrous back up my 10psi...

Click sig pic for a better view of parts and that state she is in right now. www.myspace.com/rippedtornheart
The firebirds own site = www.geocities.com/rippedtornheart

89IrocZ350TPI

Thats a good list but I wanted to keep it to bolt ons only. Meaning no power adders, or internals.

tom3

I have your top three, but went from the 2:77 gear to a 3:27. And I'd suggest a pair of K&N filters with an airfoil in the throttle body. My next plan is a set of 1.6 rockers to bump the lift up a bit. But those first three mods will really wake up the car. Feels like 100 more horsepower.

89IrocZ350TPI

I also have K&N's and an air foil. They are pretty basic mods that would make the list if it were a top 10.

IrocZ'85

I've been looking into getting headers for my '85 and summit has those TES headers listed for between $400-$500. Is that a bit much or what would be a better alternative company for a little less cost? I wish i had more money

89IrocZ350TPI

IMO Edelbrock and Hooker are the best headers. I hear decent things about Hedmen headers. Just stay about from brands like black jack that are dirt cheap.

__________________
1989 Iroc L98
13.296 at 101
http://www.cardomain.com/ride/2231640

Cambridge205

People like to put the ZZ4 cam in the L98's. I put one in my car but I haven't gone WOT yet because I'm still breaking in the engine. So I'm yet to see what it has given me.

Is a cam swap a bolt on??? cams have no bolts...

I like my hooker headers and my hooker cat back. However I dont like the look of tail pipes on these cars, to bad I cant get my tail pipes off...

The only bad thing I have herd about headmen headers is their y-pipe's are smaller or not made as well as others I forget where I heard that from... maybe its the opposite maybe the headers are not so good but the y-pipe is better... I forget but its something like that.

89IrocZ350TPI

[quote=Cambridge205;3727812]People like to put the ZZ4 cam in the L98's. I put one in my car but I haven't gone WOT yet because I'm still breaking in the engine. So I'm yet to see what it has given me.

Is a cam swap a bolt on??? cams have no bolts...

No its an internal mod. I thought more people were using the ZZ9 cam? Interesting.

__________________
1989 Iroc L98
13.296 at 101
http://www.cardomain.com/ride/2231640

85irocz355tpi

I would add the adjustable fuel pressure regulator. You can get them from tpis for around 50 bux now and its billet alluminum. I just got mine and gonna tune it in on the dyno in about a mont. I'll let you know how much of a difference it makes. Tpis lists up to a 31 HP increase and 54 LB FT on a stock l98. Mine isn't stock so im curious to how much of a difference it will make on mine. Stock pressure varries from 38-42PSI and they recommend bringing it up to 47PSI for the advertised increase. Keep you guys posted.

89IrocZ350TPI

AFPR is NOT going to add 31 horses. Maybe 5-10.

85irocz355tpi

Actually everyone I have ever seen done has netted atleast 15-20 and tpis has been around a long time. I wouldn't think they would lie about it. We'll see. When I go to the dyno I will run a baseline at the stock pressure and go from there. I'll post it here for you guys to see. I guess though that it might not be a peak power increase and be a noticed increase at any rpm. It is possible only to get 10-15 hp peak increase but increase the power in other parts of the power band more.

Cambridge205

The ZZ9 cam is a little bigger but the ZZ4 cam is cheaper if you get it off ebay.

If we wernt just talking about bolt ons I would say cam is 4 because its no good if you just have the stock exhaust on.

Is your 13.3 1/4 mile with the stock cam??

85irocz355tpi

What are the specs on those cams? I put a pbm roller cam in my 355 when I built it. I rather like it. The specs are- 214IN 224EX Duration/ .470IN .490EX. I don't remember off the top of my head what the LSA is but this cam works great in my motor. My tpi 305 would burn the tires from a dead start all day and fall on it's face over 4500rpms. The 355 lost just enough bottom end to get off the line with out sending the tires up in smoke and really comes in around 2000-2500Rpms and pulls pretty good to 5500 on stock tpi intake. I don't know exact HP numbers or Quarter mile times since havn't had it to the drag strip or dyno yet. But it beats LT1's all day long and there isn't a Mustang GT around here that can touch it either. I can run close to an LS1 but havn't actually beat one yet but I"m within a car of them.

89IrocZ350TPI

Yeah stock cam. My setup is listed on my car domain.

PS- If you get 30 hp from that afpr i will be amazed.