I got back late last night after a hole day on the Engine Dyno with a friends ZZ4.We made 35 pulls starting with the setup that was on it when it was in the car.It made 344HP. Next we changed the timming to 36 Deg. from 34 Deg. and it went to 361 HP.We messed with the timming some but never made more HP's. Next we Installed 1.6RR from Jeg's and made a pull of 379HP.
We changed the Jets in the BG street Demon 650 to 83 secondary and 71 Prim.and went to 385HP,431 Torqe !!! That was the best we could get with timming and jets.Not bad for a $230.00 upgrade(Roller Rockers) and a Crate Engine.this should make around 300HP at the rear wheels of his 81 Z28 with a 700R4 Trans. I have Pictures and a video here on this site under Dyno!!!

 

CHP did a test with the ZZ4 and with a hotcam+1.6rr it made 395hp. A lot of vendors sell them that way since the ZZ4 valvetrain has all of the hotcam kit components save for the cam and rockers.

 

would be interesting to see the numbers with a larger CFM carb...750 BG or so..
G

 

Yea ^^,a 750 wouldve prob. been another 10-15 HP. Those are nice # for that little dough!

 

I've one of those ZZ4's with the H.O.T. cam/roller rocker kit in my 80Z. I've only run it twice, but managed a few very high 12's with 2.0 6' times. With some slicks I'm sure it would go much better.

 

Your right they are great numbers for only a little money.As for the carb BG says that the 650 Street Demon(same flow as a Holley HP 750) is the best.We tried a Fatter Jet than what BG said and it lost power,we also leaned it up from what BG said and lost power.We are going to the track this summer and see wo has the Faster car!!! I'll keep you posted with VIDEO!
Anyone that builds or buys a engine should dyno it!!! It's worth the money!!! You know How and what to do to make the most Power!

 

So the motor made 18hp with the 1.6RR's. Very good info.

 

Interesting,I didnt know Demons were "hooked up" like that.

 

does the ZZ4 have standard non-roller 1.5 rockers??

can't recall.

wondering if the gains were just from the roller bearings or from added lift as well.

GOOD info...thanks


oh...and what were the RPMs that the hp/torque peaked at??

 

1.5 stamped steel rockers. So the added lift and roller bearings are both a help. Some people cried foul when ZZ4s started being sold with a hotcam and 1.6rr installed rated at 395hp. But when you figure increased duration, roller bearings, increased lift, and hopefully a mechanical secondary carb it seems possible to me. I figured going from 1.5 to 1.6 with the ZZ4 cam would bring the exhaust springs awfully close to coil bind though.

 

That's good info. I've heard from a couple people running the ZZ4 motor that they have actually gotten more power out of it than GM advertises. Looks like you got a smidge more than advertised even before swapping in the higher ratio rockers. The stock ZZ4 cam is pretty mild with only 208* duration on the intake (but a much larger 221* on the exhaust). I can definitely see how a swap to higher ratio rockers would add more to the bottom line, especially on the intake side. I can also see how the LT-4 Hotcam with it's larger 218/228* duration would work well with that motor.

 

The HP was at 5322 RPM and the torque was at 3223 RPM. We made more HP with a 1 INCH spacer under the carb but lost 10 Lb of Torque and it came in later about 4300RPM.

 

This thread makes me want to put 1.6rr on my ZZ4. My only concern is coil bind on the exhaust side. Max lift for the stock springs is .525, and 1.6s should produce about .540" lift at the exhaust valve. Has your friend checked for this yet?