355HP. 405ft.lbs torque. offered in jegs for $3395. seems like an upgrade from my 305HO. so here's my question: is this a friendly engine for a daily driver, and what sort of problems should i expect to have after the swap? i've got a 700r4 tranny with less than 1000 miles on it. i've put on about 400 and i havent really abused it any. any thoughts? again, i'm wanting to do some mods to get more power, but deffinatley need the gas mileage. i've also been considering upgrading the 305. i've read here many a time to just dump the 305 and get a 350. has anybody used a ZZ4 in a ThirdGen, and how was the mileage? any help is appreciated. thanks.

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1984 Z-28, 305HO 4bbl, t-tops, K&N, Flowmaster 80 Series with 3" tips. Planning a massive modfest. It's gonna be one gangsta of a street demon.

 

WHY the hell are so concerned about gas mileage ? If you're shopping for engines based on gas mileage why not get a V6 or keep your 305 ?? More power almost always means MORE gas consumed !

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1991 Z28 5.7 TPI

ZZ4 heads, ZZ4 cam, Harland Sharp roller rockers, Accel base, SLP siamesed runners, 52MM SLP Throttle Body, Hooker Headers, Flowmaster catback, MSD6A ignition, Home made ramair system, aluminum driveshaft, WC 5-speed etc

 

LS1's have a lot of power and have pretty nice gas mileage. Of course, LS1's are too rich for my blood. Might I remind you that an LS1 is a 350. I'm asking what kind of mileage the ZZ4 gets. So if you don't have anything constructive to say, don't bother replying to this topic. I AM aware that more power=losing mileage. No need to get into a twist about it, umkay? Some people claim that their 350s aren't too hard on the gas, and those are the one's I'm wanting to talk to.

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1984 Z-28, 305HO 4bbl, t-tops, K&N, Flowmaster 80 Series with 3" tips. Planning a massive modfest. It's gonna be one gangsta of a street demon.

 

sort of. Part of that equation depends on how the engine is built and the restrictiveness of it's parts as well as it's wear and state of tune. Bigger engines as a rule of thumb use more air to make power and therefore need increases in fuel to match, but since there are so many factors out there, it's anyone's guess. I'm sure there are plenty of 350 and 400 TPI guys logging excellent mileage because they consider these things as their engines are being built. Some of these things are A/F ratio (should be 14.7:1), quench clearances, ignition systems, fuel injector flow rates, gear selection, and engine drag, just to name a few.

BTW: a typical LS1 as in the 5.7L LS1 is a 346, not a 350 like most people think. Just my $.02.

[This message has been edited by dhirocz (edited November 06, 2001).]

 

Spend an extra grand and get the 350 HO Conversion Kit. It'll have everything you need to make the swap, the factory warranty, and the stickers to prove it's legal (if that's worth anything to you).

If you don't get the kit, the problems you will encounter are EGR valve (no crossover passage in the ZZ4 heads), exhaust (aftermarket headers et al will do fine, though), computer (should be able to get a chip from Jet or someone similar).

You'll have to burn premium afterwards. That will change the mileage question to a cost question.

The only person I know who did the ZZ3/4 went TPI with Bigmouth, runners, TB, extrude hone, dual cats, custom chip, etc., etc., etc. His driving mixes in 1320 runs, so "mileage" never comes up...

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4 (restalled TC). Ported World 305 heads, Crane PowerMax cam. ZZ4 intake, oil pump, pan & baffle. Accel HEI SuperCoil & module. Hooker 2055 headers, 3" Catco cat & 3" catback w/dual-opposite Flowmaster. 2.93 limited slip, Spohn SFCs. AMSOIL syn lubes bumper-to-bumper. Daily year-round driver. Best ET, speed TBD...
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Holley 750VS w/4150 conversion, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 700 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).

 

I'm getting 18-20 mpg with my setup. I've been burning my own proms for a couple of weeks now, and I'm confident I could make it better. Frankly, I'm concentrating on performance at this point.

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'87 Formula WS6 - ZZ4 Crate TPI, Scroggin-Dickey ported heads, LT4 hot cam, 1.6RR, Accel runners, Accel base, ported plenum, Edelbrock 58mm TB, Crane Fireball ignition, SLP cold air, SLP 1 5/8 headers, !cat, Summit exhaust cutout, Walbro 255, Koni yellows, Hotchkis panhard & LCA's, 9 bolt w/3.27's.