I hate to say this but with a ZZ4 cam rev kit 1-3/4 headers cut out and custom tune on a dyno it put 256hp@5400 and 269lbs@4700 which was about a 100 less then i thought it was going to do. Air fuel is about 12.9 to 13.2 the whole time. Also at 5800 rpm horsepower dramatically decreases. I was also getting 7* of retard from the knock sensor. My tuner made it less sensitive and lowered it to 4* he thought it was false knock. He also told me he thinks that the dramatic drop in power is due to my valves not seating properly and actually bouncing, then the lifters pump up to correct the bouncing and prevent the valves from closing all the way. Please help I dont know whats wrong.

ps before with zz4 crate untuned with stealth ram i was running 8.7 at 83mph which would put me at about the same power level now with afr heads and tuned. im stumped

as soon as i get my scanner working i'll post the graph

 

what is you compression ratio? are you sure it is false knock? sounds like some of the electronics are messed up.
JP

 

9 to 1 compression my timing was at 10* he changed it to 6* and it had no effect on the knock sensor he was also running conservitive timing it the prom.

 

What is conservative?

 

i think it was 28 not sure though I really wanted to get some opinions because im going back tommorow to pay him and im starting to question the tune

 

Could be mechanical.

Can you hear the motor ping?

What does the KS report? Where does it pick up counts?

Fasle maybe? Valvetrain, converter, header rubbing?

 

I cant or the tuner cant hear any actual noise coming from the engine sorry i dont know as much detail as u ask i wasnt the one tuning it or even there while it was being tuned. But how much can 4* hurt performance ? My tuner said it wouldnt make much difference. I would think 4* is a ton

 

The HSR likes a lot of timing advance. If your ECM is set at a low advance rate & is pulling out timing, that would explain alot.

 

Seems like your tuner just wants to get paid. 4* is alot if things are conservative from the start.

He should be able to give you all the info you want about what the KS is reporting.

I would get things on the up and up before I put out the money for the chip.

How big is the cam you are running? Pretty small right?

I imagine with the small cam you should be closer to at least 280rwhp.

 

its the zz4 longblock with zz4 cam. and ya i was really suprised by the low power out put im going there right now.

 

Who is tuning it?

how much they charging?

 

stock compression on a zz4 is like 10:1 if im thinking correctly. If the afr's have bigger cc chambers which i assume they do based on what u said your compression currently is, that loss of 1 comp point could cause the loss of power over expected.

and the drop of power at 5800 is expected with the cams duration. On top of that even an ls1 gets valve float above 6k.

 

which chamber head did you get? the 74cc or 68cc?

the ZZ4 starts off with 10:1 with 58cc heads.

68cc = 9.1:1
74cc = 8.5:1

there can be some major power loss in this area alone. i run the ZZ4 cam myself. you're not going to get past 5500 in power. that's all it was designed for. now granted this is with ported L98 heads.

here's some of my graphs with the cam and different intakes. including the HSR.

SLP/Edelbrock RED line
HSR BLUE line
http://www.fl-thirdgen.org/mrr23/tpihsrcompare.jpg

and you can post your car and engine specs over at www.stealthram.com and i'll get it put on the HSR CARS section. and register on the message board.

 

Did your tuner log any data? Is he burning chips right there?
List all the specs on your motor. Not enough info to go on yet.

 

Ok first of all i have 68 cc chambers which would drop my compresion from 10 to 9 i used the dyno 2000 compression calculater. Now about the knock 2* is in at 4600 4* by 5200 and back to 2* by 5600 total timing is 29 with 6 base timing so thats 35 now minus 4 thats 31 way to low. The tune is done and i have my car back air fuel is all good and he said its a mechanical problem i have confidence he knows what he's doing. Also right before the the drop in power (225 hp@5800 to 155@6000 same drop in torque too) there is a lean spike for about 300rpm where it jumps to 13.5 then back to 12.8 he thinks that a valve is bouncing causing fresh air to get in the chamber and also maybe responsible for the knock.

zz4 long block and cam w/ 1.6 magnum roller rockers
AFR 195 heads 68 cc chamber
1-3/4 shorty headers w/ cut out
all new ignition but still stock only plug wires different
24lb svo injecters
stealth ram stock throttle body
and custom tune on dyno

 

also i forgot he had a early 80's corvette there that had the zz4 deluxe pakage put it straight in he's car didnt touch a bolt that made 215 hp@5300 and 240 lbs of torque @3600 so maybe its just the dyno i think its a mustang dyno he said its the best dyno on the market

 

friend of mine with a crate ZZ4 motor. 770 vacuum secondary demon carb and 1 5/8 headers on a dynojet. granted this is a carb set up. but gives you an idea of what it will put out.

Dyno Results 268.5hp 315.1tq

http://www.fl-thirdgen.org/mizfitcreations.html

 

Sounds to me like you need to get a dyno on a dyno jet to compare it with the common numbers everyone throws around and with what you were expecting... If it put down 40 more rwhp than a stock ZZ4 on the same dyno I'd think you're doing pretty good, but good *** those are crappy numbers for doing any comparison online or anything...

 

the 6* base timing should be accounted for in the timing tables meaning that if you didn't mess with the stock setting for intial timing on the chip and your spark table says 29*, then you only have 29* + WOT timing advance (I think it's ~4* for most of the rpm range).

Sounds like it's mostly just that dyno gives low numbers, go see what the track says.

 

What kind of petrol did you have in the tank (octane, age, supplier, etc.)?

As mentioned above, the timing tables show actual spark as seen by the engine and not the advance if it is the stock ECM (730 if your car is a 91 as your screenname eludes) but if you haven't factored in the WOT advance maybe that is pretty high and you are actually running too much advance.

IMO, there is no reason it should be knocking like that - given the information you have provided - and I would get to the bottom of it regardless of what your tuner says....

 

Could be an ecm failure, the same thing happened to me when i swapped engines. Try another one and see what happens.
JP

 

Ya know, that 9:1 compression is not exactly helping things either........

 

you have a stick or auto? clutch could be slipping slightly

also it may not be just one thing it can be a lot of small things and togehter you are loosing hp. timing, fuel pressure, equipment, tuner, dyno, EXPECTATIONS

 

Quench? Dynamic compression ratio?

 

i have an auto; the ecm is fine since its been over a year since i did the engine swap; 9 to 1 compression is because this will be super charged in the future also the reason i wanted to keep the cam on the smaller side but i think its a little too small; as far as the numbers i put down i thinks its just the dyno, if i made 40 more horse than a zz4 on the same dyno it should put me in the 400 hp range which is what i expected. before with just the stock zz4 and stealth ram and all the other necessary things i was running 8.7 @ 82 mph 2.0X 60's in the 1/8th mile for a 3500lb car thats gotta be around 330hp so i pretty much think its impossible to have an untuned (305 chip) zz4 stealth ram add AFR 195 heads and have it tuned on a dyno and gain nothing. So hopfully the track will prove the dyno wrong. I still need to address the knocking though have any of u heard about valves bouncing like my tuner said the were ? and i gotta get this darn scanner working

 

finally got the scanner to work at the end there is still on the gas even though it looks like we got off it

 

you are losing a lot of high rpm power b/c of the cam, get one better suited to the HSR. The ZZ4 cam is good for TPI but not enough for the HSR.
JP

 

You got any buddies with a 98-02 z28 or firebird. you could do a quick run from 40mph to 70mph and that would tell you a lot. If you hang that dyno is registering low. Although that cam is small it is near the size of the ls1 cam, just not as much lift. But those AFR heads should outflow the ls1s at low lift so you should be in LS1 power range.

 

I dont know what an ls1 lift is but i have 1.6 rockers so i have 5.06 in and 5.40 ex and as for doing a roll with an ls1 before i swapped heads with my untuned zz4 stealth ram i never lossed to any not even close now of course i think most where close to stock but i did race an 01 SS a # of times and consistently beat him by a car length or more.

the thing i'm concered about is how my power goes straight down whether my cam is big enough or not it still should gradually go down not just stop all together

 

Different setup but have you ever seen a dyno of a stock TPI. Its tanks right at 5000rpm.

 

We have a mustang dyno, and I happen to be working on a ZZ4 as I type. It puts 230 Hp to the wheels (both carbed and with a 6 barrel fuel injection system, currently working on a 8 barrel, then 12) through a TH350 and 4.10 ish gears. Mustangs are always going to read lower than a dynojet (you can multiply the output a little to match it), but that isn't really important. What is important is the A/F, and Knock (and an engine that'll hold together). The ZZ4 is spec'ed out to have 10 degrees initial at 800 RPM, 32 degrees total at 4000 RPM with no vacuum advance. With less compression, more is likely tolerable.

ZZ4's stock also are rated at 355 HP at 5250 RPM, so I wouldn't expect the heads to raise that RPM much. Cam change would, though.

How is that dyno picking up RPM? If it is just from wheel speed, like ours is currently set up, then, the actual RPMs could be much higher than what's indicated (tire and tranny slippage). If it is an inductive pick-up, though, it will be accurate.

I haven't been going to 6K with the ZZ4 heads. I haven't seen that kind of power drop off either, but valve float would be my first inclination on your graph.

Good Luck,
Jeremy

 

My expereince with Mustang dynos is they read low on HP. There's a car I built the engine for (400ci) that only put 260-270HP to the rollers and went mid-high 12s @ 112+ on street tires. Of course, it nailed 470 ft/lbs @ 2700 with a gradual downward slope, never dropping below 400 ft/lbs until past 5000 RPMs. The dyno operator agreed that the HP readings were low, but that it put down about 50 more HP than a typical stock LS-1 usually did on the same dyno. Take Mustang Dyno HP readings with a grain of salt. Near as I can tell they don't square up with more common DynoJet HP readings very well.

The fast fall-off on the top end is either valve float or you ran out of fuel pressure or your spark is weak. Your dyno operator may be right about the valve float. AFR heads come standard with springs that are designed for a flat tappet cam, unless you ordered the roller spring package. Even though the springs may look large in diameter and have 2 coils they are a head-fake. They still only provide enough spring pressure to deal with a modest flat tappet cam. AFR installs them becuase the larger, low tension dual coils live a long life on the street with a flat tappet cam, not becuase they provide a lot of spring pressure.

If the ZZ4 cam is a roller cam (I don't remember if it is or not) I'd look into upgrading the valve springs. Yes, even with a rev kit. The rev kit is not going to save you from a badly mismatched cam/sping combo.

 

Another thing- that spark retard is killing you. 32* total is pretty conservative. Subtracting 10*, 7* or even 4* from false knock is givng away a lot of power. You're left with only 20-28* total timing once the retard is subtracted out. That's murder on an engine that you know you've dropped compression on quite a bit with the head change, especially.

I would suspect, as your dyno guy did, that you have a "false knock" problem. You've got a LOT of changes to the engine and valve train from stock, it wouldn't surprise me.

To temporarily eliminate/diagnose the false knock all you need to do is run the knock sensor wire through a $.25 Radio Shack resistor (3900 Ohm) and then on to a good ground. This will make the ECM think the knock sensor is still there (so it doesn't throw a code) BUT it will never register knock, obviously. Yes, it's totally safe (as long as there's no REAL knock going on) and it works just like I say it does. I've done it many times myself in similar situations.

 

You also have a mis-matched combo. The cam is ok but not optimal, you have the stock throttle body, and could probably use an msd ignition or other aftermarket ignition.

 

Dude...the stock TB will be OK for a while yet...and as long as his stock ignition is in good condition with a good tuneup...that will be fine too.

The problem lies elsewhere. The springs could well be a possible issue...but the issue with the spark sounds like part of the problem. After all, why should you have knock with only 28 degrees of timing? Not with that low of a compression ratio. Either there is a knock sensor issue or another ignition issue...Matt87GTA was right in that it could be bad quality gas. If possible try to find some 100 octane unleaded to see if that eliminates the problem.

HTH,

 

My money is still on the ECM. A faulty ECM can cause knock. And would have a sudden drop of power at that point. My reccomendation is to go to a junkyard pick up a $20 ecm put your prom in and see if it works. If it doesn't, resell it for the same price here or on ebay and you have just eliminated one possibility.
JP

 

Look into the springs. They look like doubles with dampers but have the pressure of a single with damper. had the same problem, Solid roller on a AFR spring with 120# of seat pressure doesnt work well at ALL.


Also look into the timing at the crank. Just because it says 32* in the computer doesnt mean your actually getting 32* at the crank. Sometimes the distributor slips back some and you can lose a lot of timing like that. doubtfull, but possible.

 

thanks for all the help guys this weekend im gonna redo my valve lash and im hoping that will solve the problem if not maybe ill have to look into buying new springs. with that resister do u fab up a switch or somthing to turn it on or off or do u just leave it off all the time. and where can i get a quality scanner so i can keep tabs on everything happening in my engine. thanks again.