If you took a stock L98 350 and added the following to it:

Stock Heads:
multi-angle valve job
new springs
2.02/1.60 valves
port match intake ports to manifold intake runners
roller rockers w/ 7/16 screw in rocker studs
TPIS ZZ9 camshaft
Adjustable fuel pressure regulator
MAF (screens removed)
TPIS Airfoil
Hooker 2055 headers w/ Y-pipe
Random Technologies catalytic converter
SLP catback

What would be the estimated horsepower? 1989 IROC was rated as stock 230@4400...

 

with stock unported TPI intake maybe 270 certainly no more than 300 at the flywheel. all you are really doing is a cam, rockers, and exhaust.

 

Wow!

I was hoping somewhere around 300 hp. I was doing some research on the ZZ9 cam and it was supposed to give an extra 40 hp w/ new valves. The L98 has some good bottom end torque but 230 hp??? I been seriously considering an engine swap.

http://www.gmpartsdepot.com/store/pr...Category_ID=63

 

Besides forced induction, what upgrades will put the L98 up over 300 hp. The only thing that must stay is the TPI system. I don't mind replacing the intake manifold and runners but I'm trying to keep as much of the original parts as possible...

 

Yah you cam make that power with a 350 pretty easy. you just need more than stock heads, a cam, and exhaust. you need high flow runners and base, use the cam you listed, use the exhaust, and get a better set of aftermarket, or GM Vortec heads. you could also step up to a stealth ram or a mini ram intake for better high rpm breathing.

 

Better heads... I was looking at the AFR 195cc heads. They are available in straight or L98 angle plug versions. Which would be the best or is there a performance difference?

Revised:

AFR 195cc cylinder heads*
TPIS Big Mouth Manifold*
TPIS Large Tube Runners*
TPIS ZZ9 camshaft
Adjustable fuel pressure regulator
MAF (screens removed)
TPIS Airfoil
Hooker 2055 headers w/ Y-pipe
Random Technologies catalytic converter
SLP catback

How much hp???

 

You should be able to get into the range of around 350 horsepower and 400 ft/lb of torque. Maybe more, maybe less, who knows. You will need some serious PROM tuning after all that to make the most of it. Some fail to realize what can be found by hooking up the computer

 

Wanted to mention two things:

If you are going to use TPI, even if it consists of aftermarket parts, AFRs are overkill. Spend your money somewhere else unless you want to be able to upgrade to another manifold later.

If you are going to spend all that money on aftermarket TPI parts, you'll get much more bang for the buck if you sell your current tpi stuff, and pick up a stealth ram. Now you can use those AFRs, and a nice cam. Pick a cam around 218-224 or so, and you'll be hovering around 400 hp at the flywheel.

I know I said two things, but I want to sneak another one in hear. I don't know the specs on the ZZ9, but last time I was in the market for a cam, I looked at the TPIS cams, and they are way overpriced. They are nothing special. I would look else where unless money isn't a problem.

 

I know the TPI system is a bottleneck, but I really love the looks of a TPI engine. I want to keep the engine looking as stock as I can, but increase the horsepower. 230 hp in 1989 was great, but today they make Neons with that much horsepower.

One of the reasons I was looking at TPIS was that they have a lot of knowledge tuning these engines. And yes they are higher priced...

TPiS: $375.00
Competition Cams: $245.00
Crane: $269.00

Good looking Competition Cams:
Advertised Duration: 276/281
@ .050: 224/230
Lift w/ 1.5 rocker: .503/.510
LSA: 112

 

TPI is not as bad as people say. LS1 engines make killer power with the long runners. TPI is still the best looking intake ever made. The best bet for stock looking is the TPIS parts. Just the commoner will never notice the large tube runners or big mouth manifold, or the ported plenum. All the other aftermarket runners stick out like a sore thumb, except the accel ones which I think look like stock also(but they are also way too expensive). I disagree about the AFR's being overkill. They are said to be worth lots of power gain on a stock engine. With the mods you are planning they would be even better. IMO they are well worth the money. This debate is just like everything else, everyone has their own opinion. There are lots of guys on this site making huge power with them. Do a search and you might be surprised what you will find.

 

I totally agree, puts a smile on my face every time the hood goes up. I love those runners...

I really like the AFRs. The only bad thing I've ever heard about them is price. I've never heard anything negative about performance or quality....

 

Try doing a search for AFRs and valve springs then.

Since it seems that you are planning on staying with TPI, I wouldn't recommend that 224/230 cam you listed. Its too big. You are going to throw away some bottom end, without picking up anything up top. You'll be better off with something smaller.

I have the LT4 Hotcam in my car. 218, 228 @.050. Its too big for me as well. The cam peaks around 5600 rpm. The engine falls on its face at around 4600-4800 rpm. So what happens between 4800 to 5600, nothing really. Having this big a cam actually hurts since it gave up some bottom end.

Why did I pick that cam? I don't plan on keeping TPI for ever. I'll eventually move onto a stealthram, or a superram. I'm overcammed now, but I'll save myself a cam swap and the expense of another cam later.

 

Sure there are. Most have a non-TPI intake too.

Ever wonder why AFRs are so popular, and TPI being so popular, why there are so few people running AFRs and TPI together?

Its not a matter of opinions. The AFRs will flow better than the stock castings. They will yield an improvement over the factory heads. Thats not what I am saying though. What I am saying is that they are not neccessary when you have an intake as restrictive as that.

That would be like installing a Ford 9 inch in place of your 10 bolt after doing a cam swap on an otherwise stock L03. Doesn't hurt, but its not necessary.

 

Correct me if I am wrong, but yielding an improvement would make them necessary, stock intake or not, they will make a very noticable improvement. Check out the thread about the TPI shootout. They used Trick Flow heads, but from what I understand the AFR's are better(and yes, cost more)and made 410 HP and 500 ft/lb or torque. Now it is a 383, but still, the 350 should not fall that short. AFR claims 80 horsepower on an otherwise stock 350. Sound like a waste of money now? Don't think so. That is the good thing about TPI. All the power is low in the RPM range so there is no need to scream it to make it go fast. Think about that, add correct cam and headers and you have a little rocket. And the key word you said is MOST guys do not have stock intakes. But there are some that do...

 

I couldn't disagree more. A blower will yield an improvement, but no one is considering it necessary.

80 hp on an otherwise stock 350???? I don't buy that if you are talking about your run of the mill carbed 350. Even less with TPI. Do you honestly believe a 245 hp engine will pick up 80 hp, with everything else the same? Having 325hp with the stock cam?

Agreed. And the significant differences between AFRs and stock castings are at high valve lift points. That implies a cam big enough to have enough lift to take advantage of that. That implies a cam that peaks beyond the TPIs ability to breathe. Thats why I am saying they are overkill. Not a bad choice in heads, I've never said that.

Agreed. I would be surprised if you could find over 5 on this board that have TPI and AFRs. Thats 5 out of how many thousands of users?

I'm not going against AFR, I think they make excellent heads. I plan on picking up a set myself later on down the road when money isn't tight.

 

I think you are missing the point. Yes a blower will yield an improvement. If the person who started this thread wanted to go that route for a power adder(which he stated he doesn't)then he apparently thinks it is necessary. He may want twin turbos as his power adder. May not be deemed necessary by some, but if that is what he wants, then he again thinks it is necessary.

.[/QUOTE] OK, I messed up about AFRs horsepower. They claim up to 80 horsepower with the right combo of parts. My bad, sorry. Are they overkill? By no means. The AFR 180s have most of their peak flow capacity around .400 lift, right where the L98 cam's highest lift is. Yes, they flow a little better up until .600 lift, but that would be a little much cam for a street TPI engine. And I have personally seen quite a few people make close to 300 horsepower with the stock cam(without forced induction). It is not that hard, just takes a lot of bolts ons/free mods and some good chip tuning.

I highly doubt on a site of thousands of people there are 5 with TPI and AFRs. Maybe we should do a poll and find out...

 

92blue/chevy385,

Thanks for the replies, great information. What I'm looking for is a HP increase of about 120. I would like to stick with the TPI system but increase the engine HP to around 350. That would be plenty enough to have some fun with. I love the characteristics of the TPI system, having all that torque down low is a lot of fun.

How's this cam?

Competition Cams:
Advertised Duration: 269/276
@ .050: 218/224
Lift w/ 1.5 rocker: .495/.503
LSA: 112

Good power range 1500 - 5500

 

You are welcome for the help. That cam would be good for a street driver with some aftermarket intake parts. If you did some porting on the plenum and other little intake mods with headers and exhaust you could make the cam real nice. You will be hard pressed to get 120 horsepower with the stock heads. Maybe Vortecs or something better. World Products SR Torquer and Dart Iron Eagles would be good starter heads that would net you close to that power with good intake and exhaust. As far as your stock heads, with all the money you are talking about putting into them you could get a set of Iron Eagles or something like that . You could also get the roller cam upgraded Vortecs for around $800, but then you need a new intake and some funky EGR plumbing. There are lots of options to consider. But for simplicity, the WP or Dart heads would be better. Or the AFR's if you can afford them. 120 horsepower more may be pushing it, but you will come close. The stock intake is what will hurt you. Accel and TPIS make good intake setups that mirror the stock ones except for they work a lot better due to larger runners. Someone who doesn't know TPI and just glances at it will never know(except for the ID plates, unless you leave the stock one on...)

 

I think I'm going to hold off on the engine for now. I'm really considering the GM ZZ383/425 crate engine. That engine with an Accel Super Ram would be awesome...