I swaped to carb on my l98 and i was looking at the zz4 engine and i seen it had 355hp and 405tq with the only difference in my setup is the zz4 has the vette heads a zz4 cam other then that same setup. I figure the vette heads and zz4 cam at most will gain 50hp at most over stock l98 cam and heads. The stock l98 hp is 230 and tq is 330 so what other difference other then heads and cam makes the zz4 have so much more power. Even with those heads and cam on my car i figure 280hp what about the other 75hp? Does a 4 barrell carb and intake really that much better then tpi? Reason i ask all this is because i swaped to carb looking for more power and everyone i tell that i did this says im crazy and my car will make alot less power but i just cant see how after looking at the zz4.

 

The 355 HP rating was likely based on a dyno configuration with open exhaust or headers and a minimum of accessories. The 230 HP rating for the L98 includes your accessories and production exhaust system. IIRC, GM rated the ZZ4 at 306 HP installed in an Fbody in an old GMPP catalog using the stock exhaust and a computer controlled Quadrajet. So the ZZ4 is stronger than the L98, but not 125 HP stronger. The carb will pump up the peak HP but decrease power below say 4500 RPM compared to TPI. One's not necessarily "better" than the other, just depends what you're looking for.

 

that being said still seems like a carb will have about 25 more hp over tpi?

 

More than 25 HP at peak if I had to guess.

 

These are my rear-wheel dyno-numbers for the zz4. 271rwhp 368rwtq.This is before I added 1.5 roller rockers(worth maybe 2-3rwhp and 2rwtq, not much more). I have seen a few zz4s run 280rwhp but torque is usally down to about 340rwtq because of 1 3/4 headers. A zz4 with a carb will typically make 25-40 rwhp more than a stock tpi setup. 240-250rwhp is common on zz4s with the stock TPI system.You need aftermarkert runners,baseplate,etc, and it still wont pull the numbers a carb will.You need something like a holley stealth ram to pull the dyno numbers.ZZ4's make 306hp with a q-jet and no headers.This seems about right but add headers a a DP and you will get between 345-360hp demending on carb and header size.My brother has a L98 vette and it has several mods and it still won't beat my zz4.He has aftermarket runners,baseplate, throttle body,headers, full exhasut.Not to say that I have not been beaten by a L98 with just bolt-ons but It is not just so simple as a cam swap and vette heads and your going to be able to run the zz4 power numbers.

 

I believe someone else here has said that the ZZ4 heads are an improved casting compared to the L98 heads.

 

ZZ4 heads are the exact same as aluminum L98 Corvette heads, except the ZZ4 heads have the same springs that come in the LT4 HOT cam kit.

My ZZ4 engine with a ported stock TPI intake, AS&M large tube runners, 52mm TB, and SLP 1 3/4" headers with a 3" flowmaster exhaust made 282 RWHP at 4600 rpms and 380 RWTQ at 3600 rpms thru a T5 manual trans.

As Mark89Formula said, the 355 HP rating of the ZZ4 is gross horsepower, which means dyno headers, no exhaust, a water pump only, etc. The L98 f-body engine was rated at 220 HP in 1987 up to 245 HP in 1992. That is net horsepower, and its dynoed the exact same way it would be in the car, with full manifolds and exhaust, all accessories such as a/c, alternator, and air pump. Also, engines are dynoed on the engine stand, and the value is what the engine actually makes, not what the car makes at the rear wheels.

 

ok well i just wanted some proof that for power and power only carb is better for that setup then tpi.

 

"power for power" all you're gaining going to a carb is rpm. You'll lose torque in the mid range swapping over to a carbeurator. If you're trying to justify your swap then gear the car and make your engine wind higher. If you can move the torque peak up then gear it to accomodate that. TPI's work out beautifully with the stock 3.27 gearing (or 3.42). If you go to 3.73 you won't have the revs to support it and you'll blitz right through your power band. So let's give 2 possibilities here. You take a stock car with let's say 2.73 rear gears and a stock stall. The TPI is going to be a way better match for this car than the carb. Take the same car and put in 3.73 gears, and a 2500rpm stall and the carb is going to shine. It's all about the combination, not one setup making more "power" than another. This being said a carb can support more overall power than the TPI because of its design and the flexibility it allows for. However the TPI has its place and in cars set up for it, it's hard to beat.

 

Thats pretty good Kevin, I have not seen anything over 248rwhp with a stock TPI setup but then again you have the runners, and throttle body and run a stick.All the ones I have seen run the stock tpi with the edelbrock headers. Intersting though your peek hp is way lower then mine. Mine is 271rwhp at 5300rpm and peak torque is 368rwtq at 3800rpm. I am suprised your torque was so high with 1 3/4 but you also have the stick, and tpi which boalsters low end torque on the dyno.You say you run 12.8 what is your 60ft and do you have an 1/8 mile time also.Just wondering because I am running a 2.0 60ft with a 8.6 1/8 mile with a stock stall. The one thing that I am sure of is that the L98 castings off of a vette are a little different then the zz4s.I have seen mine brothers off his vette and the combuston chamber looks alot cleaner on the zz4 heads when we took then off my car.Its probalby the same origanal casting but the runners and chambers might be a little fine tuned over the last 10+years.Also is the ported heads and hotcam done afterwards.Intersting to see what a hotcam and a little porting does.Did you run 12.8 with the stock cam and un-ported heads or was that after.

 

60' time is in my sig, (1.923) and my 1/8 mile was 8.25 @ 86 MPH, but that was with the LT4 hot cam and ported TPIS intake and siamesed SLP runners.
My best with the ZZ4 cam and stock ported TPI intake was 13.23 @ 107.19 or so. I dont remember the 60' but I think it was 1.99 or 2.01 or something like that. I dont remember the 1/8 mile either, but it was probably close to yours.
I cant explain why your engine makes hp at a higher rpm, either.

 

ok. i got a 92 camaro rs 305 tbi with 4 speed auto. my question is what would be the best and easiest with the lest mods to swap in the my rs. the zz4 or the L98 and what year engine

thnx

 

now are wanting a zz4 tbi? i have a zz3 and thought about tbi because i have a tbi 92 firebird. tbichip.com dynoed a zz4 tbi at 248hp and 309ft lbs tq with what looks like a factory manifold, 305 injectors, plus a spacer, factory throttlebody, shorty headers and full exhaust. with a few bolt-ons you could hang with tpi and carb zz4 camaros and firebirds