Where do I start searching for more speed?

Took my dad and his coronet to the track last night, first time at the track-


383 .030 over, stealth heads- rebuilt by local machine shop with good valve job. holley sniper EFI, Edelbrock intake and its a 9.5 to 1 compression motor, roller rockers, hydraulic cam- 520 ish lift, forgot duration but its a street cam, matched to a 3400 stall converter 727 amd 8 3/4 with 3.73 gears- gears

cam was bought and matched for the cars weight, engine, gears and converter.

The car on the chassis dyno did like 315 WHP and 350 TQ.

the best it did last night was 15.4 at 89 MPH. was consistent in the 60', 330' etc.... its just slow. Traction was NOT an issue. At 315 WHP it should be mid 13's at the worst. its a full 2 seconds off!?!?!?!?!?!?!?

not quite sure what is happening here!

Check the obvious things first, full throttle, accuracy of TDC on the dampener, try shifting it at different rpm to get the best numbers in the330, 660 and 1000 ft times.
Make a plan on testing different things and follow it, the car will talk to you if you can understand it Keep notes
I make sure that I right all changes on the time slip before doing anything else including transferring that run and changes into the logbooks
Review your previous changes on testing, sometimes you have to go the wrong way to learn that it was the wrong way
What year Coronet and racing weight with driver, if you know it?

Make sure it goes wfo

what the weight of the car? is the converter flashing up to its stall speed? how did you launch the car?

Regardless of the ET 89 mph is weak. Full throttle opening, improper timing curve, fuel mixture, or a really bad converter.
Doug

I think mid 13's is a bit optimistic for that combination. Mid to low 14's is more realistic IMHO. One thing you have to keep in mind is that dyno horsepower horsepower numbers are corrected to 50ﾟF at sea level. Unless you were racing in that kind of density altitude, the car will be slower than the dyno and and the calculator indicate that it will be. Have you had the car on an accurate scale, or are you using an estimate. Sometimes these cars are heavier than we think.

Most untested street cars that I have brought to the drag strip for the 1st time run about a second slower than they are ultimately capable of with with dialing in.

Most of that 1 second gain comes from things that have already been talked about on this thread. Making sure that all the butterflies are opening all the way. Verify the timing mark and the timing. Take the spare and anything heavy out of the trunk. Don't have a full tank of gas. Make sure that you have adequate fuel pressure and fuel delivery through the entire pass.Experiment with launch RPM, shift RPM, tire pressure, different timing, different air fuel ratio. Sometimes it takes different gears or converter to get it where it should be. Also if the car has been street driven a lot, the backsides of the valves could be carboned up hindering flow. If you are running it through the mufflers, try yncorkung it. Does have a big fan on it with no fan clutch? That will slow it down. It's usually a bunch of little things and not one big thing. Are you running headers, or exhaust manifold's? Slicks or street tires?
Good luck, enjoy the process.

What year Coronet? Can you post a time slip?

My daughter's 67 Coronet with an almost stock 383 (has a cam, Holley Street Dominator Intake and Holley 750 DP otherwise stock through the exhaust manifolds and full stock exhaust) went 15.0 @ 91 mph with a 3:55 gear and lousy 60 foot. The car weights just a tad over 4000 lbs with me in it.

Is the Sniper system controlling your timing? If so, check the parameters to make sure it isnt retarding the timing, or not advancing all the way. Also, make sure the throttle blades are opening up all the way. you should be able to see the TPS% opening. Make sure you are getting at least high 80's up to almost 100%.

You could also throw a carb on it as well, and see if the car hits harder at launch.
(I was running Fitech injection all summer, and they were running pretyy good. However, i found that my car launched much harder with carbs instead)

I’m kinda in the same situation, and I can see on the fuel injection I’m only getting about 80% throttle opening

If your throttle cable is tight, you could try to bend your gas pedal a little bit toward you - if you still have the stock gas pedal assembly. I ended up putting in an adjustable Lokar gas pedal and cable, and was able to get the Fitech's throttles opened to 95-100% at WOT. I have a dual quad set up on mine, running 1:1 linkage. For some reason, the geometry of the Mopar gas pedal and the combo of brackets wouldn't let me get the butterflies opened all the way until i used an adjustable pedal.

Anyway, I'm enjoying drag racing my car a lot more now, and I'm running twin 800 cfm AVS2 Edelbrocks. Those things hit a lot harder at launch when compared to the EFI. it didnt matter how much ACCEL pump settings i played with.

Just my 2 cents!

Also a dual plane intake can cause many running problems when under a load, if you have a dual plane intake put at least a 1in open spacer on it & see how it does, OR put a good single plane intake on it

Fuel supply & fuel level, what did you change between the dyno and the track?

Restrictive exhaust?

What shift rpm and can you post the chassis dyno sheet?

i was going to say to check the distributor timing curve, but that has been already mentioned.
if using a factory distributor, look closely at the advance plate and weights to see if there are any burrs or grooves in those pieces that might be restricting their movement.

Look for SAE correction instead of STD correction on any type of dyno sheet, they can usually correct to both. STD isn't realistic, while SAE is more representative of real world conditions.

Car was raced exactly as it came off the chassis dyno?

What were the uncorrected chassis dyno numbers?

What’s the elevation of the track?

I had a tired 361 that someone put in a 69 Charger and used the 69 383 4bbl intake and carb on, along with the ex manifolds.
12” converter, 3.23’s........ went 15.60’s.

Something is far enough off on that combo where it “should” be easy enough to find.

yeah something seems off

my dad rebuilt a 383 in his '69 charger a long time ago. used the cheap MP cast pistons, rebuilt 906 heads, stock valves i'm sure.
small MP cam in dot to dot, 268/272 383 magnum cam i'm pretty sure. facotry 4bbl intake, factory HP manifolds. stock converter and 2.76 gears.
ran a 15.9 at 99mph if i remember correctly.

i agree with something "far off". i think the car was only doing about 230hp at the crank for 89mph. way back in the day i had a 383 4spd road runner ; 3.55 gear. car ran consistent 14.20's/96-98mph with no mods. went consistent 13.20's with a dp4b, 1 3/4 hookers, 228@.050" cam, and 4.10 gear. drove the thing everywhere. only transportation i had.

This combo should easily get into the 13s. My 100% stock 383 Dart GTS convertible ran 14.50s with a 3.23 one wheel peel. Heck I was a kid, timing? What's timing? I didn't know.
Doug

Wow okay lets me try to cover all questions

Yes the car is the same as it was on the chassis dyno.

The chassis Dyno is at sea level and the track is too- the track says they are 13' elevation.

Its a 1965 coronet-



We got 5 runs in that night the best was actually a 15.5 overall most runs were withing 1 MPH of this run

60'- 2.256
330'- 6.431
1/8- 9.913
MPH- 7-.20
1000'-12.944
ET- 15.5
MPH - 86.72

I checked for full throttle and when the pedal is depressed I cannot move the throttle any further. I didn't look at the screen to see if it actually was at or near 100% but physically it certainly was.

I had been working on the tune and cleaning up the fuel map, the self learn works pretty good, but it does not smooth itself. The fuel map had gigantic holes in it, so Id add fuel there to fix the holes. Holley also stops the car from adding more than 50% fuel many spots were maxxed out, so I then added base fuel to it- which would allow the computer to add more if needed.

Timing is 16ish initial and 36* all in.