Slow coronet
#3087948
10/20/22 11:03 PM
10/20/22 11:03 PM
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Joined: Jul 2011
Posts: 781 wine country
8urvette
OP
super stock
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OP
super stock
Joined: Jul 2011
Posts: 781
wine country
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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!
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Re: Slow coronet
[Re: 8urvette]
#3087960
10/21/22 01:43 AM
10/21/22 01:43 AM
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Joined: Aug 2003
Posts: 43,163 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,163
Bend,OR USA
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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?
Last edited by Cab_Burge; 10/21/22 01:45 AM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Slow coronet
[Re: dvw]
#3088030
10/21/22 11:13 AM
10/21/22 11:13 AM
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Joined: Jan 2003
Posts: 7,489 Minnesota
Hemi_Joel
master
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master
Joined: Jan 2003
Posts: 7,489
Minnesota
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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 11:19 AM.
[img]http://i.imgur.com/boeexFms.jpg[/img]31 Plymouth Coupe, 392 Hemi, T56 magnum RS23J71 RS27J77 RP23J71 RO23J71 WM21J8A I don't regret the things I've done. I only regret the things I didn't do. "Wise men talk because they have something to say; fools because they have to say something. ~ Plato"
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Re: Slow coronet
[Re: Hemi_Joel]
#3088037
10/21/22 11:53 AM
10/21/22 11:53 AM
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Joined: Jan 2003
Posts: 4,270 Morrow, OH
markz528
master
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master
Joined: Jan 2003
Posts: 4,270
Morrow, OH
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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) 14.82 @ 94 mph 69 GTX (clone) - build in progress......
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Re: Slow coronet
[Re: markz528]
#3088044
10/21/22 12:26 PM
10/21/22 12:26 PM
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Joined: Jan 2003
Posts: 3,921 Richmond, Indiana
19swinger70
master
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master
Joined: Jan 2003
Posts: 3,921
Richmond, Indiana
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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
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Re: Slow coronet
[Re: 19swinger70]
#3088047
10/21/22 12:42 PM
10/21/22 12:42 PM
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Joined: Oct 2005
Posts: 270 Anchorage, Alaska
metallicareload
enthusiast
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enthusiast
Joined: Oct 2005
Posts: 270
Anchorage, Alaska
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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
440, 4-Speed, 3.54 1968, when Dinosaurs ruled the Earth
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Re: Slow coronet
[Re: metallicareload]
#3088058
10/21/22 01:09 PM
10/21/22 01:09 PM
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Joined: Jan 2003
Posts: 3,921 Richmond, Indiana
19swinger70
master
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master
Joined: Jan 2003
Posts: 3,921
Richmond, Indiana
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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!
1970 340 swinger. sublime 1967 barracuda fastback BB 55 Plymouth Project
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Re: Slow coronet
[Re: 19swinger70]
#3088065
10/21/22 01:26 PM
10/21/22 01:26 PM
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Joined: Aug 2011
Posts: 2,857 Pattison Texas
CSK
master
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master
Joined: Aug 2011
Posts: 2,857
Pattison Texas
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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 Stock 11.79 @ 114.5
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Re: Slow coronet
[Re: 19swinger70]
#3088066
10/21/22 01:30 PM
10/21/22 01:30 PM
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Joined: Jun 2006
Posts: 5,161 CT
GTX MATT
master
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master
Joined: Jun 2006
Posts: 5,161
CT
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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
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Re: Slow coronet
[Re: 8urvette]
#3088068
10/21/22 01:43 PM
10/21/22 01:43 PM
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Joined: May 2019
Posts: 712 Lake Villa Il
INTMD8
super stock
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super stock
Joined: May 2019
Posts: 712
Lake Villa Il
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Restrictive exhaust?
What shift rpm and can you post the chassis dyno sheet?
69 Charger. 438ci Gen2 hemi. Flex fuel. Holley HP efi. 650rwhp @7250 510rwtq @5700
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Re: Slow coronet
[Re: Hemi_Joel]
#3088118
10/21/22 04:31 PM
10/21/22 04:31 PM
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Joined: Jan 2003
Posts: 8,165 Plymouth, MI
Blusmbl
master
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master
Joined: Jan 2003
Posts: 8,165
Plymouth, MI
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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
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Re: Slow coronet
[Re: moparx]
#3088119
10/21/22 04:34 PM
10/21/22 04:34 PM
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Joined: Jan 2003
Posts: 14,496 So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 14,496
So. Burlington, Vt.
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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
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Re: Slow coronet
[Re: lewtot184]
#3088146
10/21/22 07:15 PM
10/21/22 07:15 PM
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Joined: Mar 2006
Posts: 9,835 MI, usa
dvw
master
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master
Joined: Mar 2006
Posts: 9,835
MI, usa
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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 07:15 PM.
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