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Slow coronet #3087948
10/20/22 10:03 PM
10/20/22 10:03 PM
Joined: Jul 2011
Posts: 758
wine country
8
8urvette Offline OP
super stock
8urvette  Offline OP
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wine country
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!

Re: Slow coronet [Re: 8urvette] #3087960
10/21/22 12:43 AM
10/21/22 12:43 AM
Joined: Aug 2003
Posts: 40,823
Bend,OR USA
C
Cab_Burge Offline
I Win
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Bend,OR USA
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 wrench Keep notes up
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 scope
Review your previous changes on testing, sometimes you have to go the wrong way to learn that it was the wrong way shock shruggy
What year Coronet and racing weight with driver, if you know it?

Last edited by Cab_Burge; 10/21/22 12:45 AM.

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Slow coronet [Re: Cab_Burge] #3087988
10/21/22 05:59 AM
10/21/22 05:59 AM
Joined: Jan 2003
Posts: 5,626
Hot Rod Ridge
FastmOp Offline
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FastmOp  Offline
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Hot Rod Ridge
Make sure it goes wfo

Re: Slow coronet [Re: FastmOp] #3087996
10/21/22 07:22 AM
10/21/22 07:22 AM
Joined: Jan 2003
Posts: 6,979
Warren, MI
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Jerry Offline
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Jerry  Offline
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Warren, MI
what the weight of the car? is the converter flashing up to its stall speed? how did you launch the car?


Superior Design Concepts
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Troy MI 48083
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Re: Slow coronet [Re: Jerry] #3088016
10/21/22 09:18 AM
10/21/22 09:18 AM
Joined: Mar 2006
Posts: 9,243
MI, usa
dvw Offline
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MI, usa
Regardless of the ET 89 mph is weak. Full throttle opening, improper timing curve, fuel mixture, or a really bad converter.
Doug

Re: Slow coronet [Re: dvw] #3088030
10/21/22 10:13 AM
10/21/22 10:13 AM
Joined: Jan 2003
Posts: 7,202
Minnesota
Hemi_Joel Offline
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Minnesota
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.

Last edited by Hemi_Joel; 10/21/22 10:19 AM.

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Re: Slow coronet [Re: Hemi_Joel] #3088037
10/21/22 10:53 AM
10/21/22 10:53 AM
Joined: Jan 2003
Posts: 4,117
Milford, OH
markz528 Offline
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markz528  Offline
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Milford, OH
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.


67 Coronet 500 9.610 @ 139.20 mph
67 Coronet 500 (street car) 13.300 @ 101.75 mph
69 GTX (clone) - build in progress......
Re: Slow coronet [Re: markz528] #3088044
10/21/22 11:26 AM
10/21/22 11:26 AM
Joined: Jan 2003
Posts: 3,840
Richmond, Indiana
19swinger70 Offline
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19swinger70  Offline
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Richmond, Indiana
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)


1970 340 swinger. sublime
1967 barracuda fastback BB
55 Plymouth Project
Re: Slow coronet [Re: 19swinger70] #3088047
10/21/22 11:42 AM
10/21/22 11:42 AM
Joined: Oct 2005
Posts: 156
Anchorage, Alaska
metallicareload Offline
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Anchorage, Alaska
Originally Posted by 19swinger70
Is the Sniper system controlling iagree 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)



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


440, 4-Speed, 3.54
1968, when Dinosaurs ruled the Earth
Re: Slow coronet [Re: metallicareload] #3088058
10/21/22 12:09 PM
10/21/22 12:09 PM
Joined: Jan 2003
Posts: 3,840
Richmond, Indiana
19swinger70 Offline
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Richmond, Indiana
Originally Posted by metallicareload
Originally Posted by 19swinger70
Is the Sniper system controlling iagree 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)



iagree 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!


1970 340 swinger. sublime
1967 barracuda fastback BB
55 Plymouth Project
Re: Slow coronet [Re: 19swinger70] #3088065
10/21/22 12:26 PM
10/21/22 12:26 PM
Joined: Aug 2011
Posts: 2,672
Pattison Texas
csk Offline
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Pattison Texas
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


1968 Charger COLD A/C Hilborn EFI
512ci 9.7 compression, Stealth heads, 4.10 gear A518 ODtrans 4100lb,10.93 full street car trim
2020 T/A 392

Re: Slow coronet [Re: 19swinger70] #3088066
10/21/22 12:30 PM
10/21/22 12:30 PM
Joined: Jun 2006
Posts: 5,121
CT
GTX MATT Offline
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CT
Fuel supply & fuel level, what did you change between the dyno and the track?


Now I need to pin those needles, got to feel that heat
Hear my motor screamin while I'm tearin up the street
Re: Slow coronet [Re: 8urvette] #3088068
10/21/22 12:43 PM
10/21/22 12:43 PM
Joined: May 2019
Posts: 539
Lake Villa Il
INTMD8 Offline
mopar
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mopar

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Lake Villa Il
Restrictive exhaust?

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


69 Charger. 438ci Gen2 hemi. Flex fuel. Holley HP efi. 595rwhp 475rwtq.
Re: Slow coronet [Re: INTMD8] #3088078
10/21/22 01:11 PM
10/21/22 01:11 PM
Joined: Sep 2003
Posts: 17,225
north of coder
moparx Offline
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Posts: 17,225
north of coder
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.
beer

Re: Slow coronet [Re: Hemi_Joel] #3088118
10/21/22 03:31 PM
10/21/22 03:31 PM
Joined: Jan 2003
Posts: 7,812
Plymouth, MI
Blusmbl Offline
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Posts: 7,812
Plymouth, MI
Originally Posted by Hemi_Joel
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.


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.


'18 Ford Raptor, random motorcycles, 1968 Plymouth Fury III - 11.37 @ 118
Re: Slow coronet [Re: moparx] #3088119
10/21/22 03:34 PM
10/21/22 03:34 PM
Joined: Jan 2003
Posts: 14,171
So. Burlington, Vt.
F
fast68plymouth Offline
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Posts: 14,171
So. Burlington, Vt.
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.


68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
Re: Slow coronet [Re: fast68plymouth] #3088120
10/21/22 03:49 PM
10/21/22 03:49 PM
Joined: Jan 2003
Posts: 2,094
central texas
K
krautrock Offline
top fuel
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top fuel
K

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Posts: 2,094
central texas
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.

Re: Slow coronet [Re: krautrock] #3088141
10/21/22 06:04 PM
10/21/22 06:04 PM
Joined: Jun 2008
Posts: 3,844
usa
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lewtot184 Offline
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usa
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.

Re: Slow coronet [Re: lewtot184] #3088146
10/21/22 06:15 PM
10/21/22 06:15 PM
Joined: Mar 2006
Posts: 9,243
MI, usa
dvw Offline
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dvw  Offline
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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

Last edited by dvw; 10/21/22 06:15 PM.
Re: Slow coronet [Re: dvw] #3088278
10/22/22 10:23 AM
10/22/22 10:23 AM
Joined: Jul 2011
Posts: 758
wine country
8
8urvette Offline OP
super stock
8urvette  Offline OP
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wine country
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.

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