Originally Posted by parksr5
So, got my engine in the car and took it to the track today for its first shake down runs. It's slow and I really don't know why.

The engine made 460HP on the engine dyno. The car is 3667 with me in it. Today, it ran a best of 12.99. Plugging that into Wallace Racing Calculators, that's 330hp to the crank, so; it's running like it's down 130hp.
.

With milder iterations of this engine, I've run as fast as 12.25 and have never run as slow as I did today, with lesser power.

The car isn't doing anything noticeably bad or wrong though. It's not missing, it's not laying over, it's not making noises, It's launching okay, not as good as it has in the past but, maybe off by .10 in the 60ft. The fuel pressure is right below 6lbs (Edelbrock Thunder 800), the air fuel ratio might be a touch lean for max power (low 13's). I checked the throttle, and the carb barrels are opening all the way when I have the pedal pushed all the way to the floor. I'm just kind of like, why did it slow down that much?

Again, if it was doing something noticeable, okay but, it's just not really doing anything bad, it's just slow.

My first thought, take it to the chassis dyno, like 20 minutes from me, see what it's putting down to the tires, monitor fuel pressure to see if it might be dropping at any point, and see if we can find any smoking guns. One would assume that it's an issue with something other than the engine itself, since it was made the power it did on the engine dyno.

What else should I be looking for? Just never had an issue like this.


I used to bracket race a 66 dart with a 3602bbl engine with nothing but a thermoquad and manifold swapped on it, I got it very consistent and it was an over achiever combo, low geared 904 and 2.94 gears, finnaly decided to get a bigger cam XE268 and matching springs and stuff and it slowed down a ton 60ft, MPH and ET all were way down even though it actually pulled way harder and way higher RPM, eventually I put in 3.92 gears and it became way faster and way less consistent. Just because you are running slower does not mean the engine is not making more power, it could just be that you are not using it all. With that big of a cam and low compression you are going to have a very soft bottom end and you probably will not catch your old combo till you make matching changes to the rest of the combo. And for the people who say MPH is HP.... that is only true if your car is close to set up right, try running your car launching in 3rd instead of 1st and see how much slower your MPH is at the end of the track. Also the engine wanting to turn higher RPM because of the bigger cam means the manifolds are going to be a much bigger restriction than they were on the lower RPM combo.

I am not causing global warming, I am just trying to hold off a impending Ice Age!