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!)

Re: Lazy off the line
 

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...

Re: Lazy off the line
 

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

Re: Lazy off the line
 

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

Re: Lazy off the line
 

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!

Re: Lazy off the line
 

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.

Re: Lazy off the line
 

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

Re: Lazy off the line
 

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

Re: Lazy off the line
 

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!

Re: Lazy off the line
 

C6 transmission could be holding your car back some.

Re: Lazy off the line
 

Hans, I'm sure it is brother. I had read somewhere that a C6 will eat about 60-70hp vs. a C4 at 30-40?

This car was originally an F code 302 with a C4, I sold that pair to drop in the New combo. If I could go back I would have kept the C4 and had it prepped for this application rather than going with the C6....but, I'm not terribly concerned at this point. My aim is to bracket race this car and have some fun and learn along the way. Future SS build will of course, NOT include the C6 :)

Re: Lazy off the line
 

Not enough rear gear. Carb is too big. Cam needs to be advanced not retarded. That is killing the low end. Fix all of that stuff and it will run much better.

Re: Lazy off the line
 

Pressure in the rear tires (10 psi) seems on the low side in my opinion.

Re: Lazy off the line
 

K.I.S.S is the best principal to use in racing, Adger and Keith have great suggestions, I will deviate from KISS and say to Check your converter, could be junk and it's slipping.

Re: Lazy off the line
 

Hi. I also believe the heads are too big, especially for the compression ratio. Not enough lower rpm velocity. Since you are just starting out with the idea to be racing for a long time. Buy your self a data logger system. I use Racepak. Most of these issues will show up in a very runs and can actually save you time, money and frustration. I have never seen anyone who finally bought a data logger regret spending the money.
Dan

Re: Lazy off the line
 

Well, just wrapped up a great weekend at Pacific Raceways up here in WA state. Two separate races sat & sun we went down for both. Basically treated the races as a test and tune to see what we could get out of the car given its current running condition.

Improved ET and 60' a little bit by throwing a bit more timing and jetting down.l (it was a bit fat) Car runs pretty consistent though, it is dial-able (still learning the car of course)

Won in round one on Saturday but lost round two. Bummer was that I was comatose on the line. Worst reaction time I've ever put on a time slip. Lost my composure! (First time going beyond the first round of elim's).

Bigger bummer is that my opponent was so far slower on his dial I only needed to cut a .120 light to have won. Kicked my own butt all night after that one!

Sunday went good, found a good spot on the tree, worst RT was a .090 in three passes. Broke WAY out in the first round. I dialed slower, car picked up.

Fun weekend nonetheless.

You boys offering up advice, I hear ya and gonna put 4.56's under it soon. Gonna try a 750HP and see if that helps, looking at a different manifold as well. But other than that I'll just run as is this season. I'll certainly be digging deeper into the situation this winter, gonna look into a more appropriate cam for sure. Maybe a looser converter.

For now, I'll keep absorbing info from folks like you guys and taking it one step at a time.

Sure is fun though, even in the 12's!

Re: Lazy off the line
 

X2 on everything

Re: Lazy off the line
 

I agree with the above advice. When I read the initial post, I felt the carb was too big, the intake too aligned to high rpm (especially depending on how it was ported), and the rear gears too mild. Yes, the carb and intake may match the ported heads, but the overall result is consistent with a high rpm combination, and is being killed by a low rpm combination elsewhere.

Re: Lazy off the line
 

How much total timing do you have dialed-in....all in by??

Re: Lazy off the line
 

How tall are your rear tires?

3.90s wouldn't be bad if you had 26-27 inch tire i've been mid 1.50s in a 3200lb amx with 4.10s and 28 inch tires with a much milder than your combo 390. that 1.90 sixty foot definitely indicates a issue somewhere.

Re: Lazy off the line
 

Let me know when you find that spot on the tree,lol.



HAMMER

Re: Lazy off the line
 

Exactly.......
putting the cam in 2 retarded is going to guarantee you more retard running.

I remember Joe Sherman always telling everyone that you could run the intake clearance very close just spinning the motor around by hand. If it clears by .010 to .020 it will be fine running because the dynamic loading of the system would increase the clearances and retard the cam. The valve is chasing the piston down the hole too.