After looking through some catalogs, it looks to me like the ZZ4 and L98 aren't too different, except for the cam and the aluminum heads as opposed to the cast iron. While I realize that the ZZ4 heads will increase power from the higher compression, is there any other difference between these motors in terms of power-output aside from the cam? If there isn't, wouldn't I get about the same power from just installing the cam and matching valvesprings?
Has anyone ever used a L98 with a ZZ4 valvetrain, or a ZZ4 crate engine on their TPI Iroc with Mass Air? How/what did it run?
Thanks

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1980 Camaro, '88 Police 350 engine, Headers, full exhaust, completely redone, my baby!
1988 Iroc-Z L98, MSD 6a, Accel coil, K+N's, Airfoil, Coolant Bypass, Flowmaster, Gears, Late model Bose, I like the 80 better

 

The difference is mainly in the rotating assembly and the block. The ZZ4 has a nodular iron crank, powdered metal rods (2nd generation), and hypereutectic pistons at about 10:1 compression with 58cc heads. The ZZ4 also has a 4-bolt main.

The L98 has "lesser" components and a 2-bolt block. To answer your question, you can effectively build the same power with your L98, but just know that the bottom end is a bit "weaker" than the ZZ4. Not that that would ever come into play with street racing.

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'92 RS, ZZ4 10:1 350, Edelbrock 6085 heads, Crane 208/214* 467/482" 112* cam, GM/LT4 1.6 roller rockers, Edelbrock Hi-Flow TPI base, runners & 52mm TB, SLP/Jet-Hot 1-5/8" headers, Catco 3" cat, Flowmaster 3" catback, Hughes 2500 stall converter, stock 700R4, 1LE driveshaft, Auburn Pro posi w/3.42, 17x9" SS rims w/BFG tires, Medium Quasar Blue w/white SS stripes, 48,000 miles....

 

The ZZ4 aluminum heads are better than the L98 iron heads, but you will definitely see a nice increase with the ZZ4 cam and upgraded valvesprings. Its a great cam for TPI.

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1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.23 @ 107.62 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

 

The ZZ4 has forged steel crankshaft. And there is a real life 100hp difference in the L98 and ZZ4.

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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,and just about every other bolt on that there is. Just got a ZEX nitrous kit!

 

You will have to either buy new front springs or cut your old ones down when you save all that weight off the front end with the aluminum heads Then pulling the iron exhaust manifolds for heads helped even more. My car used to sit very high in the front end until I cut one turn out of each front spring. Went from 4 fingers between the tire and wheel to two fingers. These were the stock RS springs by the way.

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Rob P
89RSconvtZZ4TPI
Edelbrock Hi-Flow Intake
SLP Dual Cold Air Intake
1 5/8" Headers
Semi-Siamesed Runners
MSD6AL/AdjFPR/IROC frnt@rear swaybar/wonderbar/steeringbox/alum drvshaft/ Alston SFC/3:23posi disc rear/MAC LCA/H.Adams Panhard Rod/KYB struts/ shocks/
92Z28convt5spd
71Impala convt 402BB
BETTER DRIVING THRU SUPERIOR HORSEPOWER!

 

I don't think that the ZZ4 has a forged steel crank. My GM Perfomance parts book says that the ZZ engines have nodular iron cranks. BUT, I was just on Pace Parts site and their description of the ZZ4 does state a forged steel crank. Who is correct??

SDPC says forged steel crank also....my mistake, but now I'm thrilled that I too have a forged steel crank!!

[This message has been edited by Scott C (edited May 22, 2001).]

 

You only have a forged crank if you ordered the shortblock. The longblock engines come with nodular, unless you special order it.

 

What kind of idle should I expect if I go with the ZZ4 Cam, and most likely headers at the same time. Also, what kind of performance increase should I expect?

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1980 Camaro, '88 Police 350 engine, Headers, full exhaust, completely redone, my baby!
1988 Iroc-Z L98, MSD 6a, Accel coil, K+N's, Airfoil, Coolant Bypass, Flowmaster, Gears, Late model Bose, I like the 80 better

 

The ZZ4 cam doesn't idle very rough, though there is a hint of lope at low idle. With ZZ4 heads/cam, Accel base/runners, SLP headers and 1.6 rockers I am hoping to see 100 rwhp gain. We will see if it gets me into the 12's.

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87 Formula 350 13.94@96.67
98 Z28 1LE 13.15@107.59
1LE Owners Association

 

hey 91-ZZ4-Z28 does that mean that the zz-4 makes 400 hp when instaled?? I figure that i am pretty close to 300 hp at the crank now with the stock internals and heads. The zz-4 probly makes another 25 to 30 hp more than an l98. The zz-4 short block is stout. it can probly handle a 200 shot of juice.


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90 IROC l98
last season best corected 13.62 @102
mods
full exhaust, AFPR, pulley, jet stage 1 chip, billet servo, 52mm throttle body, slp runners and some 1.6 RR's and a few other little things.
243 RWHP and 342 RWTQ with hot engine and 90 octain fuel

 

All ZZ4 motors built in the last year short or long block have Crankshaft 12556307 Forged steel. A stock L98 makes about 245hp at the crank and a stock ZZ4 makes about 345hp with a well ported hi flow intake with a stock tpi it only makes about 320hp. That hp is deseptive though because it makes a crap load of torque.

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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,and just about every other bolt on that there is. Just got a ZEX nitrous kit!

 

91-ZZ4-Z28 wrote:
A stock L98 makes about 245hp at the crank and a stock ZZ4 makes about 345hp with a well ported hi flow intake with a stock tpi it only makes about 320hp. That hp is deseptive though because it makes a crap load of torque.

You're not kidding! You should hear the comments I get from some of my passengers when I put my foot down on when taking off from a light. Holy s**t is one of the more common ones I hear as their neck gets snapped back into the headrest...


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http://www.havemann.com/lee/firebird.html
1989 Firebird Formula, WS6 Package
ZZ4 Crate engine, Accel 24 pound injectors, Accel Superram intake, Accel Large tube runners
SLP 58 mm throttlebody, Edelbrock TES headers, SLP 3" SS exhaust, Random Tech 3" hi flow cat
700R4 trans w/ vette 2/4 shift servo, worked valve body, kevlar band, 2200 rpm stall converter
Borg Warner 9 bolt rear (full poly mounts) Hotchiss panhard rod, Lakewood LCA's, Spohn subframe connectors, self modified chip.

 

I'd be careful with the juice. Maybe 100 or 125hp shot, as they're equipped with the hyperglass pistons.