Lazy off the line

bnsfmachinist · 04-11-2016, 03:21 AM

Finally got my 351c running in a '69 Mustang. And it's quite lazy off the line! Looking for some advice, things to look at consider.

The numbers just aren't adding up to me...

Took it to a local chassis Dyno this past Friday to get jetting/timing all figured out. After a few jet changes we managed to put 350hp to the ground (un-corrected). So figure near the 500hp range at flywheel?

Engine runs great, pulls strong all the way down the track, awesomely crisp throttle response.

Got to a test and tune on Saturday, best pass was 12.68@107 with a 1.90 60ft time...I had thought I would be somewhere in the upper 11's at least. Am I losing something through the drive train here?

Engine info:

351c std bore/stroke
Quick fuel race q 950an
Edelbrock Torker single plane intake (ported)
Flat tops, 10.5:1 compression
Iron heads, heavily ported by AFR
Cam is solid flat tappet .630 lift, 250 @ .050, 106 lobe cl (2* retarded)
4000rpm converter

Car weighs 3200lbs with me in the seat.
Foot braking to 2800rpm on launch, shift at 6500
10psi in the slicks
C6 trans prepped for the application (original gear ratios)
3.91:1 rear end gears
Rear suspension is all calvert (bars, springs, shocks)
Front suspension is Calvert 90/10's and all opentracker products (roller upper and lower control arms, spring perches, delrin strut bushings)
Moog six cyl springs.

This is a relatively mild combo. I knew the 3.91's were going to be holding me back and New Gears are right around the corner anyway. but have seen similar combos with similar gears go into the upper 11's...

I have video of the car launching, no wheel spin, front end comes up instantly and looks like it's on the verge of pulling the tires off the track. Car launches straight and true...my only thought was, it does have a posi diff. Could the clutches be slipping in the diff from the hit?

Am I mistaken? Is that the ET/ 60ft time I should expect with 3.91's?

Thoughts, suggestions, pointers and questions are welcome.

(Yes! Lower gears and a spool coming soon!)

04-11-2016, 03:21 AM	#1
bnsfmachinist Junior Member Join Date: Feb 2014 Posts: 15 Likes: 0 Liked 0 Times in 0 Posts	Lazy off the line Finally got my 351c running in a '69 Mustang. And it's quite lazy off the line! Looking for some advice, things to look at consider. The numbers just aren't adding up to me... Took it to a local chassis Dyno this past Friday to get jetting/timing all figured out. After a few jet changes we managed to put 350hp to the ground (un-corrected). So figure near the 500hp range at flywheel? Engine runs great, pulls strong all the way down the track, awesomely crisp throttle response. Got to a test and tune on Saturday, best pass was 12.68@107 with a 1.90 60ft time...I had thought I would be somewhere in the upper 11's at least. Am I losing something through the drive train here? Engine info: 351c std bore/stroke Quick fuel race q 950an Edelbrock Torker single plane intake (ported) Flat tops, 10.5:1 compression Iron heads, heavily ported by AFR Cam is solid flat tappet .630 lift, 250 @ .050, 106 lobe cl (2* retarded) 4000rpm converter Car weighs 3200lbs with me in the seat. Foot braking to 2800rpm on launch, shift at 6500 10psi in the slicks C6 trans prepped for the application (original gear ratios) 3.91:1 rear end gears Rear suspension is all calvert (bars, springs, shocks) Front suspension is Calvert 90/10's and all opentracker products (roller upper and lower control arms, spring perches, delrin strut bushings) Moog six cyl springs. This is a relatively mild combo. I knew the 3.91's were going to be holding me back and New Gears are right around the corner anyway. but have seen similar combos with similar gears go into the upper 11's... I have video of the car launching, no wheel spin, front end comes up instantly and looks like it's on the verge of pulling the tires off the track. Car launches straight and true...my only thought was, it does have a posi diff. Could the clutches be slipping in the diff from the hit? Am I mistaken? Is that the ET/ 60ft time I should expect with 3.91's? Thoughts, suggestions, pointers and questions are welcome. (Yes! Lower gears and a spool coming soon!) Last edited by bnsfmachinist; 04-11-2016 at 03:25 AM. Reason: Words