Depressing Dyno results. Need advise

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I think the only cars to have a 3/8 fuel line to the tank were 440+6 and 426 Hemi cars, everything else is fine with the smaller line.
 
C130 Chief said:
Before you start throwing expensive pieces at the car, do some detective work and find out where your problem really lies. You can do most of this yourself with a few basic tools and a couple test drives. Don't give that dyno shop any more of your cash.

Tools: Get a timing light, a vacuum gauge and possibly a fuel pressure gauge. You should be able to get all 3 for under $100, and you'll need these to do any sort of tuning. Oh, and a stopwatch.

Fuel delivery: Replace all rubber lines, especially anything on the suction side of the pump. Pull the pickup out of the tank make sure the sock isn't clogged with crap. A decent mechanical fuel pump will do fine, a cheap Pep-Boys special won't. Go electric if you want. 5/16" line should be OK, but the factory used 3/8" on 440 cars. If the line itself is in good shape, it's probably not your problem.

Test drive: Set the timing to something sane like 10 BTDC and leave it there for now. Make sure the FLOAT LEVELS are SET CORRECTLY on the carb! Splice the fuel pressure gauge in the line between the pump and carb. Where the fuel filter was is a good place. You want a long enough piece of line on the gauge so you can tape it to the windshield and watch it while driving. Start the engine and note the pressure. Now drive around nice and easy. Pressure steady, no leaks? Find a nice quiet country road and floor it in 2nd or 3rd until it breaks up. How's the pressure, does it drop off? You'll see a little drop, but if it goes below 3 PSI, you have a fuel delivery issue. If it stays around 5 PSI look to valve float.

Valve springs: When you say stealth heads, you mean 440 Source aluminum heads right? Not sure what springs they ship these with, but they should be fine with that "mild" cam. In fact an OEM 440 spring should do OK. How does that "custom" cam base circle compare to stock? Lifter preload?

Cam: Bear in mind that a stock 440 cam had about the same .050 duration, and similar lift. Therefore you can expect similar power/RPM with the cam you have now, but less low RPM torque, and a rougher idle. That said, 350 HP, 5000 RPM at the wheels would seem more reasonable. Who knows what the numbers that dyno shop would show. 14 seconds on a country road quarter mile would be ballpark.
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I'll do this this weekend and report back. This is exactly what I needed. Very good info. Very helpful.
 
1970Duster said:
If you have stock springs in the heads that could be your problem. More then likely the springs are old, worn out or just don't have enough rate to open and close the valves like they should. Get a set of springs that match the requirements of that cam
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I forgot that I had actually bought the 440 source stealth heads pre assembled. I couldn't remember ordering springs so I assumed I had just reused the stock parts. My bad. So I do have brand new springs.
 
I don't think fuel delivery is a problem. It's a "magazine tech idea" that 5/16 is too small for anything but a mild small block. Ialso think the cam might be a little od, but iot's fine and can do what you want. However, you do have some issues. You have to know what the timing curve is before you can start jetting. Your dyno guys should have started with this. IMO, trying to sell you stuff because the dyno says it's going lean when it pops without documenting the timing curve is an amature mistake. The stock distributor has a slow and high ignition curve. You need a faster, less total curve for the engine you have. This is not a "replace with new" deal. Any distributor you get needs to be properly curved for your car. And I dont buy into the "except FBO" BS. Again, this should be item one when the car's on the roller. Timing, then fuel curve, then tweaking for final pulls. Then the "you need..."
 
again.have you checked if you fully open the carb at full throtle? its probably the most comon reason for underperforming engines in the world. and fits the symptoms described.

im with moper on this,dont replace anything until you know have checked all the basics.
 
duster340 said:
again.have you checked if you fully open the carb at full throtle? its probably the most comon reason for underperforming engines in the world. and fits the symptoms described.

im with moper on this,dont replace anything until you know have checked all the basics.
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I'm pretty sure it is set right but it wont hurt to double check. I'll take a look tomorrow.
 
sbh126 said:
I'm pretty sure it is set right but it wont hurt to double check. I'll take a look tomorrow.
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its a very easy misstake to miss it and realy anoying when its finaly figured out after troubleshoting the whole car:cry:
 
duster340 said:
its a very easy misstake to miss it and realy anoying when its finaly figured out after troubleshoting the whole car:cry:
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I here that. Picked up a second and a half in the 1/4 after I adjusted my cable so I got full throttle](*,)
 
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