Lazy off the line

[bnsfmachinist]

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!)

[stage1scott]

I'm far from an expert but that 60 ft is terrible for a 3200 lb car. My 4000 lb Buick with 400ish crank hp and 3.90 gears would 60 ft in the 1.60s with drag radials, driven to the track with a 3000 stall converter. others with far more knowledge than me will drop in soon...

Not being an expert either I would say the single plane intake is mismatched to the converter and gear. If more gear doesn't help (which I think it will because of the intake you're running) then the converter also needs loosened up.

Scott

[Keith 944]

I have a similar setup. All caltracs. 3700# mopar 340 +.030 street/strip Ati 8" converter, eldebrock heads, Vic single intake, 850 Holley, headers, full exhaust, 10.20/1 compression 391 sure grip rear m/t et streets runs 11.40-11.60 year round. I think your hp is a little low at 350 12's is prob correct for the hp. The slide rule shows mine around 450 hp @ 3700# to run what I do. With that said the best et gain was in the converter. I have run a spool with 430 gears only made about .10 diff in et. 60 foot 1.56-1.59 with 430. 1.58-1.61 with 391 gears I would play with the Jets and timing, picked up a couple tenths there. Just checked with the slide rule 350 hp at 3200 pound should be 11.60s at around 112 now of course that is at sea level your 60' is bad. Timing,jets, converter, gears, my converter flashes to 5800 shift at 6200 finish at 6100

[bnsfmachinist]

Well thanks guys for chiming in. I knew 3.91's wouldn't be ideal but I also knew 1.90 60' couldn't be right and you guys just confirmed!

So, I'm back at the track this coming weekend. Before I go I'm gonna jet down 2 sizes (Dyno operator said it'd be a good idea as we were still a bit rich when we unhooked the car, I just didn't do it prior to the last run) and throw some more timing at it. Right now I run 13* initial, 33* total all in by 2000. Dyno operator suggested bumping initial up to 18 and seeing how it does. I'll have to take note of flash rpm as well on the launch to see how the converter is acting and play with starting line rpm and where the converter works most effectively.

I just had to confirm my thoughts! Thanks gents, I'll update after the weekend! If anyone else has any other pointers, please chime in!

[Adger Smith]

Why is the cam listed as 2 deg retarded with only 10.5 Comp?
Why such a high leave RPM?
Footbrake lower and hit the converter stall harder.
Might be loosing TQ multiplication of the converter.
I would put a little more timing in it before I re jet 2 lower.

[bnsfmachinist]

I retarded the cam 2* in order to have reasonable Piston to valve clearance.

[Robert Simpson]

I like your build but I have some questions. Have you taken a cranking compression yet? If so what is the psi? If not I suggest you do that, warm it up, remove the plugs, disable the Ing., and block the carb open. Check and see what the cranking comp is. If it is low say 150psi or under the cam is to big. If it is allot higher closer to 200psi then you have other issues. I believe that the cam and the heads are to big. What you are describing the engine does not have enough bottom end. A RPM intake would help some as would the rear gear, also if you could put in a lower gear in the trans that would help also. I am just suggesting this, I am not being critical of your build just trying to help. Let me know. Thanks

Robert

[bnsfmachinist]

I appreciate the suggestion! I'm new to actively participating in this sport and this is my first purpose built drag engine. The car is going together as a bracket car with the hopes to build it into a SS/GT car. I've got a long road ahead of me filled with successes, failures and setbacks! But I'm passionate about the sport, I've grown up in a weekend warrior family and I'm finally at a point in my life to where I'm able to participate!

Anyway back to technical aspects!

I will certainly do a cranking compression test, I'm interested in the points you bring up. I got the heads from my dad who had them ported back in the 80's by AFR, I don't have the flow chart in front of me but I want to say they flow in the neighborhood of 400cfm @ .700 on the intake and 350 on the exhaust? I haven't looked at that chart in a while but I know they're big numbers. So, I figured a big set of heads is going to want a lot of air and fuel, so thus picked out a pretty big solid cam. The rest of the build follows what seems to be a pretty typical 351c mild/moderate build based upon browsing 351c.net and other ford forums.

Again, I'm new into this world of engine building so I more than appreciate advice, pointers and suggestions. I'll get on that compression test when I get an opportunity. I'm a Union Ironworker 40+ hours a week, husband and father of 3 24/7, ain't always easy to get out in the garage these days!

Thanks again guys!

[Hans Olsson]

C6 transmission could be holding your car back some.