MakoShark72

Are these hp/tq numbers fairly accurate??

ZZ4....355/405.... http://www.sallee-chevrolet.com/Chev...ockV8s/355.cfm
ZZ383....425/449....http://www.crateenginesonly.com/Chev.../ZZ383-425.cfm
ZZ383 w/Air Gap....450/488....http://www.crateenginesonly.com/Chev...ZZ383-425P.cfm

Thanks

MotorHead

The higher the numbers the more motors they sell. Some are honest others are not. I have never seen a ZZ4 put out more that about 265RWHP, what is the 405 all about is that the torque. If so then those numbers look about right

MakoShark72

Second # is torque....

MotorHead

The GM crate motors are generally pretty correct

7T1vette

Well, you can bet that the engine they tested to set that 'spec' was built with all the same part numbers....of course, they were all selected for optimum performance potential and that engine likely had many hours on the dyno to maximize every little bit they could get. Do you see anything in the specs that indicates the numbers were from a "randomly selected unit (or sample of units) from the production line"? In other words, that spec is the absolute maximum you can expect from that configuration of crate engine. The variation you can expect to get with production engines might be in the 10-15% range, IF you take a random unit and optimize its performance. A unit direct from the factory (which likely de-tunes the engines to minimize GM warranty costs) could be 20-25% lower on output as it comes out of the box.

I would certainly yield to folks with real data, but I would be pleasantly surprised to find that 'real' performance is much better than I suspect.

MotorHead

I've seen several ZZ4's on a chassis dyno and they all are in the 265-280RWHP range which is what a 355HP would make, GM has no real reason to fudge the numbers, any other ebay crate motor is however suspect

MakoShark72

How would the factory "de-tune" just a long block, since the zz383, for example, doesnt come with intake, carb, distributor, starter, fuel pump, etc....

Just asking...

Thanks!

Corey_68

Not sure about all of them but I know that the 572's are typically UNDERrated from what I have seen on the dyno.

MakoShark72

I have heard that....

thatcorvetteguy

I have seen the reported numbers on my zz 430. I bought it for a street rod that never happened. I go out to it and turn over by hand evey six months or so,maybe I'll find something to put it in. Maybe sell it to someone that needs 430 Hp and 430 Tq?

Corellian Corvette

I would tend to believe GM's numbers for their crate motors. How close are the motors they put in cars?

This isn't some mom-n-pop making engines. A company like GM has legal obligations to get close.

Plus, have you seen what some of these motors put out with small mods like headers, 1.6 rockers, an intake upgrade and a good carb? I recall seeing an article where they got like another 75 or 100hp out of the engine.

I think the GM crate motors will get you pretty honest numbers

Shark Racer

The ZZ4 and its derivatives are about as good as you can get ... with a warranty.

But real power, you'd be much better off building something. The vortec heads (and the fast burns) are nowhere near as good as the better aftermarket offerings.

TheSkunkWorks

My understanding is that GM has SAE certify their dyno numbers, and as I seriously doubt very many shops have equipment as accurately calibrated/corrected I'd be quite comfortable with their claims. ...and IMCO, unless the equipment on which one has their engine dyno'ed is accurately calibrated/corrected, comparisons aren't necessarily worth a whole lot.

7T1vette

No, you can't "detune" a short-block. But, I thought we were talking about crate "engines". If some folks who have purchased GM crate engines and taken them to a dyno, folks [me included] would like to know what the dyno numbers were "out of the box".

Priya

That would go a long ways to explaining why a GM crate motor is rated at 290 hp compared to my L82's 225 hp and yet the crate motor has lower compressiona and similar lift and duration on the cam. I'm pretty skeptical of the ratings on these crate motors.

Shark Racer

GM definitely has their production car engines certified.

The crate motors, maybe, but not to any SAE standard. They're rated in a variety of *****-nilly manners. Different size headers, some permutation of installed accessories (IE: sometimes they have some, sometimes none).

The ZZ4 is a good motor for someone just getting something on the road who wants a bit of power. I'd say in most cases, it'd be comparable to a mid 90's vette (LT-1). But you could make more power by building custom, for very equivalent costs.

AFR 180/195 heads
roller cam ~218/224
pistons
350 block
low/med rise intake

Well tuned, compression @ 9.5:1 or higher will make at least 270rwhp with an auto. More with manual.