89IROCZZ4

I find it kind of diffacult to see that Edelbrock's package on a zz4 will hit about 410 hp when the zz5 (zz4 w/fastburn heads) hit 385 hp. What is the deal? Does anyone have any specs on these two types of heads? What should I be looking for in terms of numbers?

Jester

I've already given you my vote..edelcrocks suck.

I'm moving this to the Aftermarket Product board.

CraZ-28

If you are referring to the package that Edelbrock is selling, there is a little bit more to it than just heads. It's got a bigger cam(I think), and it's also got aluminum roller rockers. I don't think the GM motor had either. I don't have the spec in front of me but there may be other differences also.

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'91 Z-28 5.7, SLP 1 3/4 headers, 4 inch Mufflex/Flowmaster cat back, gutted cats, Edelbrock intake, 8.5mm Jacob wires, MSD Blaster coil, S&W subframe setup, Jacob Pro Street Ignition, complete Kenwood system.

iroc5speed

that is correct, edelbrock put on a cam and roller rockers. when GM did that with the fast burn heads, they called the zz430, which is obviously more than 410

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'86 IROC 5-speed
305 LG4
edelbrock performer rpm intake
edelbrock 600 cfm carb
msd pro billet hei distributer
'95 3.23 rearend
hotchkis rear suspension
PST front polygraphite suspension

FlashGTA

I have not seen any true flow data including info on flow, swirl and tumble on the E-Tec's. So I would have to believe the GM's are the better head until proven otherwise.

[This message has been edited by FlashGTA (edited August 30, 2001).]

slowV8berlinetta

according to car craft, the e-tec 200s flow exellent, but when they compared the 170 and 200 e-tecs on a 350, the 170s did better than the 200s both hp and tq. The cam and compression weren't that big, but unless you've got a 510+ cam and 9.5+ compression, i would take the small port etecs before either of the larger offerings.

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'84 Berlinetta, LG4, 700R-4, starwars interior, no major mods yet

88IROCs

E-Tec 170cc: tested with 1.94 int/ 1.5 exh by CHP

Lift.........int ...........exh
0.050........32 ...........22 cfm
0.100........63 ...........48
0.200.......126 ..........104
0.300.......177 ..........138
0.400.......215 ..........169
0.500.......240 ..........180
0.600.......240 ..........190

Ask and you shall receive,...

FlashGTA

None of which actually looks at charge motion which is where the Fast Burn's excel. I would like to see a test on the same engine E-Tec vs. Fast-Burn. I know edelbrock claims more power on the same engine but I just don't believe it until a third party proves it.

88IROCs

Totally agree with you FLASH. A flowbench only tells you how much the ports flow past a static valve at a fixed opening. Problem 1 is that the valve is constantly moving and the size of the opening is constantly changing, both of which will affect airflow past the valve. Problem 2 is that the max recorded airflow usually exceeds the what the cylinder can take in by a very wide margin. For instance, in the data above max airflow is 240 cfm: multiply that by 8 cylinders and you get almost 1900 cfm. On a 350 cid SBC, you would need about 400% VE to utilize all that air. So how does the gross airflow affect what the engine actually requires. And why does one head that has less gross airflow make more power than another head with more gross airflow.

And how do you measure mixture motion accurately when the chamber type, valve type, piston type, quench area, shrouding and other factors change the quality(and quantity?) of the motion.

Like you said, the dyno is the ultimate arbiter. Flowbench numbers are a convenient, though not necessarily useful, comparison.

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"The reasonable man adapts himself to the world.
The unreasonable one persists in trying to adapt the world to himself.
Therefore all progress depends on the unreasonable man"
--George Bernard Shaw.