Nathan Plemons

Well I wouldn't rule it out completely but I still don't really know that that would be all of it. I've seen graphs before where cars flat roast the tires on the dyno and it just results in a power drop. I've also seen higher HP cars dyno'd on a dynojet without such issues.

Don't get me wrong, I'm not trying to say that there is something wrong with your setup. I just know from experience that it may well be a bigger problem than just slipping tires. I would certainly look at the fuel possibility. If your fuel pump can't keep up that would really rob you of power. Do you have a fuel pressure gauge, if not get one and tape it to the windshield and then watch it at WOT. It should peg and then stay there, it's possible that it's falling off.

I was supposed to help tune a blower car that would probably make less power than yours honestly even if everything was working right. It only ended up making 250 HP, his stock fuel pump wouldn't push it past about 4000 RPM's. He CLAIMS that he had the Walbro unit already but I've gotta call a major on that one. That car had so many other issues it's amazing it would move at all.

vetteman9368

its pretty hard to spin the tires on the dyon if the car is strapped down even close to right. We dyno'd my best friend's 800 RWHP 91 mustang yesterday and it didn't even think of spinning the tires, and thats with over 1000 ft-lb of tourqe

red L98

i think your getting some tire spin , make sure they strap it down and lower the tire press. my car did the same thing and i picked up lots power after fixing it .

if thats not the problem i would just take the car and run it down the track and see how she do. dyno numbers dont mean **** .

Caboboy

Because of the erratic spikes in the graph..........almost like a high RPM miss when a plug wire arcs, or fuel starvation. The fact he likes the car's SOTP feel, makes me wonder, 'cause I think he'd feel a high RPM tuning/fuel problem when it fell on it's face. The graph could very well be a combo of the two.......
I'm still thinking cam though as far as the curve is concerned. If it was installed straight up and had 4* ground into it, that would explain everything (except the spikey graph of course). I don't know why these guys automatically grind them advanced........ I mean that's fine with a smaller CID motor, but a big inch motor want's the torque a little further up to broaden the HP curve once it's spinning. Erson sent me a reduced base 219 clone advertised as a true 219, but when I got it, the cam card showed that damn advance. My application was a 420 CID Superram, so the last thing I needed was more down low

eguyett1985

Yeah, I do have a fuel pressure gauge but like my friend from Whipple said that only tells you if the pressure can keep up not the volume and remember a smaller fuel line will inhereintly have more pressure but less volume.

tjwong

On my dyno ripples like what I see on your curve is usually caused by noise in my tach pick up. If it were a fuel problem I normally see the curve dropping off prematurely. Having a pressure gauge on the engine during the tests will show the problem easily if its a fuel pressure issue. I had a members brothers car on the dyne a few nights ago. Seeing the AFR at 14.5+ while in PE mode no matter how much fuel I threw at it indicated a fuel starvation problem. A gauge proved the theory out, the first thing I removed and checked was the fuel filter. Cutting it apart showed that the filter was full of mud, after all it was only 18 years old! I guess it served its life well........

eguyett1985

I'll check the fuel filter (AC Delco) although it was replaced when I changed the fuel pump when I put the car together 400 miles ago..maybe it should be checked. What should the dyno operator do differently to stop noise in the tach pickup?..does this happen with HEI's also?

ol,RJ

everyone makes some good points.
at first look I thought cam timing was too far advanced.
BUT if you look at the chart with the "run time" vs HP/TQ it shows a total time of 6.8 seconds from start to 5800rpm.
I just re-watched some video'd dyno runs and all of them took close to 10 seconds to wind out.
based on that I'd say you have a slippage problem, but I doubt its the tires spinning on the dyno (unless you heard squeeling/saw tire smoke). I'd say the automatic trannie is not up to your new found power.
that might explain the spikes in the graph as well.
RJ

zelement

Your cam has more duration than the 219 but the lift numbers are way too low. Are those numbers with 1.5s or 1.6s? Do you have 1.5s or 1.6s?

Also, are you using the full "superram" intake or just the base with large tube runners. Your torque and hp curve looks more like a TPI setup rather than superram. A full superram will peak a little later than what you posted. What kind of numbers did you expect?

eguyett1985

I'm using 1.5 rockers...I have the full Superram Intake system not the TPI style components. I was hoping for 370-410 RWHP

chriswtx

I have the walbro 340 255lph pump and stock fuel lines. We had plenty of fuel while doing my tune. By 7000 my 26lb injectors were able to flow enough fuel for a 11.5 to 1 air/fuel ratio and 440rwhp...I would look else where for problems...

bjankuski

Something is holding you back but I do not have enough information to tell you what it is. I am also running a 406 and I have 10.0 to one compression, superram, 52mm throttle body, ZZ-409 cam and my combination pulls 420 RWTQ at 2800 RPM and 353 RWHP at 5500 RPM. Why does your power drop off so fast? I do not believe your fuel lines are a problem. I am running the stock lines and my pressure holds steady at my set point of 42PSI with a high volume pump. I would look at your valve springs to make sure you not experiencing valve float.

eguyett1985

I'm sure it's not valve float..I'm using brand new Comp 1.450 springs with 300# open pressure...but something is holding it back for sure.

REDC4CORVETTE

This might help a little http://www.centuryperformance.com/fuel.asp.

chriswtx

All that info is for a carburated set up. It is different for a fuel injected car. Ski-dwn-it is also still using the stock fuel lines with his 434 and has no fuel problems running 600+HP. The stock fuel lines can easily support 600+HP. Replace the fuel filter for good measure and start looking else where for the problem...

Your cams lift numbers and duration is small for the size heads your are running and the extra cubes you have(Great for a 350 but not a bigger motor). But mainly the lift. You need a lift closer to .580 or .600 for those heads and a duration around 236 or 240. You would probably pick up 40HP or more with a bigger cam. The one you are running does not match the flow capabilities of your heads....

Nathan Plemons

Correct, BUT, if your injectors are draining that fuel line faster than it can be replaced you'll have a pressure drop. If your pressure stays constant than you've got enough volume.

chriswtx

"Stock HEI", how many miles on your stock HEI and what plugs and wires are you running. Most of the bigger spikes are at the higher rpm range where you would not get tire slippage on the drums. For the spikes I would look at your ignition system and for the HP and Torque levels I would look at the cam you are using. I think they are two seaperate problems...

eguyett1985

I just rebuilt the distributor with a new AC Delco shaft kit and bearing while the car was apart. The plugs are the Champion number that Dart recommends and the Wires are MSD 8.5's w/Pro Shield

eguyett1985

There's good schematics on Aeromotive's site for EFI applications.