insaneclown

Everyone says all ZZ4 heads are is Aluminum L98 heads. But the ZZ4 has angled plugs so how can that be? I didn't think the L98 had angled plugs, does it? How are these heads different?

joking511

iTrader: (5)

The zz4 heads are the Aluminum heads that came on the corvette L98 only . You can buy them from Gm . But you would be better of buying some trickflow or some other aftermarket heads .

ProStreetZ28

iTrader: (2)

The ZZ4 heads have 58cc combustion chambers, which helps. The way they were explained to me is that they are identical to the LT-1 heads except for the cooling passages. You can get the LT-1 heads to flow pretty good 265 CFM with stock valves. Better with more port work and 2.00/1.56 valves. I have my ZZ4 heads at the machine shop to see what it would take to put 2.02/1.60 valves in them. The guy that used to do the LT-1 heads for me when I had my shop used to get like 285 CFM out of them with larger valves. If you found a killer deal a set I'd grab them, but if you're just going to buy a pair of heads I'd go with aftermarket. I got a sweet deal on mine, I only paid $200 for them with all fresh valve work. One of the nice things about them is the lightweight springs, retainers and valves. Also if you add guide plates you can run standard rocker arms, I don't trust self aligning rocker 6500-6800 RPM.

joking511

iTrader: (5)

I had a set of zz4 heads . I sold them becouse the intake runners are small 163cc I dont think youll ever see those kind of cfm #s . The head shop here in town also told me thw biggest valve you could use is 2" (Thay come with 1.94" intake 1.50 exhaust . These heads do make some power thou . The zz4 has around 350 but I dont think they could make much more than 400 .

ProStreetZ28

iTrader: (2)

He advised me I'd have to change the seats to run 2.02 valves, so at that point I'll stick with the 2.00/1.56 valves. We'll have to see how much they flow when I'm done, but I'll know for sure in a couple of weeks. After they're flowed I'll post the numbers.

91Z28

See, now I'm confused. In your head porting thread, I asked you about the capability of ZZ4 heads. Everyone tells me, ZZ4 heads are the Vette L98 aluminum heads. Then you told me they are identical to LT1 heads, and you obviously know what your stuff. I am very confused.

91Z28

Maybe the answer is: LT1 heads were very similar to L98 heads with the exception of cooling passages. This would be strange though, because so many people swear that the LT1/4 heads are great, and L98 heads are poop.

ProStreetZ28

iTrader: (2)

What I meant by the same as the LT1 head is that the port design and combustion chamber design is the same. If you layout the ports from a regular L98 head they slightly different then the ZZ4 head. The Corvette Aluminum heads are the exact same castings as the ZZ4 heads the only difference is the valves in the ZZ4 are lightweight valves and they have the same springs as the LT4 hot cam and lightweight retainers, this is what I was told by one of the GM guys that was on Power Tour hanging out with us.

DeltaT

iTrader: (5)

From Sallee-Chevrolet:

SBC Corvette Aluminum Cylinder Head Assembly (This is also the ZZ4 350 HO Cylinder Head).
This aluminum cylinder head assembly for small-block Chevrolet V8s is ideal for street rods, fresh-water power boats, and high-performance applications. GM Performance Parts’ aluminum cylinder head assembly combines the benefits of light weight, advanced design, and an affordable price. This complete head assembly includes valves, chrome silicon heavy-duty valve springs, retainers, 3/8” screw-in rocker studs-everything an enthusiast wants in a high-performance cylinder head package!

GM Performance Parts aluminum cylinder head assemblies are based on brand new Corvette light alloy castings (P/N 10088113). The Corvette cylinder head’s advanced design features include D-shaped exhaust ports that enhance the flow of burned gases, high-velocity intake runners that provide crisp throttle response, and centrally located spark plugs that improve combustion efficiency. Valve seat inserts for 1.94” diameter intake valves and 1.50” exhausts are installed in the 58cc combustion chambers. Raised rocker cover rails with machined sealing surfaces virtually eliminate rocker cover gasket oil leaks.

This high-performance cylinder head assembly is used exclusively on High Output 5.7-liter small-block V8 engines. Unlike production Corvette cylinder heads, it is outfitted with special heavy-duty valve springs (see part number 12551483 for technical specifications(JIM: These are the same LT4 springs as the Hot Cam Kit). A pair of aluminum cylinder heads offers a weight savings of approximately 50 pounds over comparable cast iron cylinder heads. (A bare aluminum casting, less valves and springs, weighs 19 pounds, versus 44 pounds for a bare cast iron head). This reduction in total engine weight of 25 pounds each can improve handling, acceleration, and fuel economy.
Part Number ... Description.
12555269 ......... Stamped steel rocker cover.
10229162 ......... Corvette screw-in oil filter cap.
12342056 ......... Chrome screw-in oil cap with GM logo.
12338092 ........ .Valve cover hold-down bolts (8 required).
14094717 ......... Hold-down bolt washers (8 required).
14088793 ......... Hold-down bolt gaskets (8 required).
14088564 ......... Neoprene rocker cover gasket.
12557236 ......... Composition head gasket, .051” thick.
12495499 ......... Head Bolt Kit.
12495490 ......... Rocker Arm Kit.

Technical Notes: This casting does not have intake manifold heat riser or EGR passages. The exhaust port exits are approximately .100” higher than production cast iron heads; exhaust manifolds and aftermarket headers may require modification to maximize airflow. The spark plug holes are angled; check for adequate exhaust manifold or header clearance. Use 3/4” reach gasketed spark plugs with 5/8” hex heads (AC FR5LS), 904, or MR43LTS. In Rapid Fire use #8 plug. Both ends of the head are machined for alternator, power steering, and air conditioning compressor mounts. No pushrod guideplates; use rail type rocker arms P/N 10089648. This aluminum head assembly requires valve covers with central hold-down bolts and extra-long bolts with washers. A composition head gasket with stainless steel fire rings is recommended to prevent galvanic action between the head and a cast iron engine block. This head assembly is the same as P/N 10185087, except valve spring and retainer change.

These heads respond well to modest porting and a good valve job. The ZZ4 will get to an easy 378hp/412trq with just this mod. These heads do not like to ping at all, and they do not like over a 150 shot - that and the hypereutectic pistons. The intake port can get close to 180 in size after porting. The D-port exhaust means you have to check your headers and header gaskets to make sure everything lines up OK and that none of the exhaust ports are blocked in any way with everything attached and tight.
The Felpro Head Gasket with the pre-flattened steel fire ring works great and adds a little compression.

David Vizard talks this head extensively, as well as porting instructions and pictures, in his book "How to Build & Modify Chevrolet Small-Block V-8 Cylinder Heads (Powerpro Series)". Great book!

Jim.

91Z28

Also, LT1 heads have 54cc combustion chambers rather than 58cc like a ZZ4. Maybe that is for LT4, don't remember.

classic gary

hate to resurect an old thread but, how well would these heads work on a 283 (+.060), for the street ? (solid lifter cam, 1X4, Holley, headers), any opinions?

ProStreetZ28

iTrader: (2)

I think you'll find that the bore on a 283 is much too small for these heads.

Irocss85

iTrader: (1)

hey prostreet, you ever get some flow #s?

Ive heard the LT1 heads were the same as the fast burn heads port-wise? never seen any though.

ProStreetZ28

iTrader: (2)

No, I swapped the heads for some fast burn heads and ended up selling the car before I finished it.

Irocss85

iTrader: (1)

damn that was a change in direction. ok.

classic gary

no, 1.94's and 1.50's will fit a 283 no problem, unless the valve guide centerline is spread from a "standard" SBC.
I've had 194/160 fuelie heads on this motor before. bore is 3.935".

ZONES89RS

iTrader: (25)

With the smaller cubes, you will find it likes to rev, i wouldnt be surprised if it got close to 7k pretty good honestly, as long as the castings are cleaned up with a bit of port work.

NemeSS

iTrader: (127)

200$ is what i sold my old set of l98's
should have just kept them

ZONES89RS

iTrader: (25)

Not a bad deal if you did not need them and they still needed a valve job, surface ect.

Kevin91Z

iTrader: (1)

My old set of L98 heads flowed 246 cfm and 206 cfm at .500" lift. They were 173cc intake port size after porting.

They're currently in a friend's 91 Trans Am A4 that recently dynoed 321 RWHP and 377 RWTQ.

The best they did in my car was 318 RWHP and 419 RWTQ, and I have a stick!