Pure Stock Drag Racing tips & tricks

[YENKO DEUCE REGISTRY]

Wow! Now that's some analysis, special thanks [img]/ubbthreads/images/graemlins/smile.gif[/img]

I guess the LCA and LSA can be the same at 106. Not sure on the idle or the vaccuum problem though, the car has good brakes even with repeated stops at quick intervals. I don't normally check vaccuum, but I did with mine because I was using it to set the mixture screws (?). I had a steady 18+ inches of vaccuum, and idle is a little high but relatively smooth.

As for being a dog on the low end, I can't really tell because this is the only deuce I have driven - and quite frankly is the fastest car I have ever owned. So, I don't know that I can compare it to anything else. I think the low end is pretty good, but then again it doesn't take much to blow the whitewalls off!

I did assemble the engine myself, basically because I wanted to do everything that I possibly could. I installed the cam per the mfg instructions, ie; straight up. I had read that the Comp cams have 5 degrees of advance 'ground in'? It didn't mean much to me at the time, all I was checking for was PTVC - which turned out fine at well over 100 thous./in. Might I have missed something during the installation?

Thanks in advance for any and all feedback, the possibility of me putting in the 182 is increasing.

[Salvatore]

Marlin, The valve adjustment determines some low end power and different vacuum. It also can be a smoother or rougher idle with different settings. You are probably getting yourself a little confused with all these numbers. This is why I asked you a week or so ago if you had any vacuum. Cam duration determines vacuum. It depends on how long the cam stays open. You are so close to Pete. He is expecting to see you and your car.Just go over or call and ask him. Good luck! Sam

[YENKO DEUCE REGISTRY]

Rob;
I've been thinking about this, but not totally sure what 'tight' means. Are you referring to the timing of when both valves are open being to little, thereby increasing cylinder pressure?

[Chevy454]

M:

Lobe Seperation Angle is simply a measurement of the angle, formed from the centerlines of the intake lobe and the exhaust lobe, measured in degrees of cam rotation. [FYI, LCA is measured in degrees of crankshaft rotation.]

Just imagine 2 imaginary lines, one extending from the centerline of the intake lobe, the other extending from the centerline of the exhaust lobe. The amount of camshaft rotation (in degrees) that it takes for the centerlines to pass the same specified point is the LSA.



So, a "tight" angle, or smaller LSA (normally 100-112) will have MORE valve overlap, meaning a lopey idle, poor vacuum quality, and the torque peak will move up the rpm range...think "top end" cam. Likewise, a "wider" LSA (112-120) will have less overlap, thus trapping more of the charge in the cylinder at low engine speeds, and will provide a better vacuum signal, and have a tame "lope" to it's idle...think "low or mid range" cam.

But, as Sam eluded to above, their are a few other "variables" provided by the cam that can influence how a cam reacts.

[YENKO DEUCE REGISTRY]

Rob;
That's the answer I was looking for! Thanks.
I'm starting to think about trying the car at the track this year with this cam, and sticking a 182 cam over the winter and then run it again next spring.

I was trying to get more low end, off idle power and driveability with the cam change not upper RPM power. With the original manifolds, smog stuff and orig. exhaust with resonators - this engine will have trouble even reaching the upper RPM's!!

Oh well, it's not irreversable [img]/ubbthreads/images/graemlins/smile.gif[/img]

[JLerum]

Even though you have an LSA of 106 degree (very tight) you can still off set it by advancing the cam. You are closing the intake valve very early if you still have good vacuum. Also,.........Your ramp speeds on the cam are probably very slow on the opening side as to some what defuse some of the duration. The lift also has a lot to do with duration as the smaller the lobes with the same angles of ramp the smaller overlap.


JIM [img]/ubbthreads/images/graemlins/flag.gif[/img]

[YENKO DEUCE REGISTRY]

Thanks Jim for the additional explanation, I have to think about what you typed for a little bit. I'll probably have some more questions down the road!

I learned something else the other night, don't pick on a Toyota Supra Twin Turbo! Pretty quick little car in it's stock form, has two more gears compared to the Yenko, would have left me in the dust past 4th [img]/ubbthreads/images/graemlins/smile.gif[/img]

[Salvatore]

Marlin, Going to Pottstown tomorrow nite? Big Rod Run and show in town. May be taking Coopers 440-6pack super bee. (Lift off hood car) Should be fun. (215)723-1600 [img]/ubbthreads/images/graemlins/[/img] [img]/ubbthreads/images/graemlins/biggthumpup.gif[/img] Sam

[JLerum]

Marlin,

The new cars go fast in a different way that's for sure. With all the over drives they can build a motor a little more differently "smaller cubes" so it can efficently work in a smaller power band using gearing to take care of the weaknesses. The stuff sure does last a long time and fly using the modern fuel systems.

JIM [img]/ubbthreads/images/graemlins/burnout.gif[/img]

I guess what I'm saying in the above thread is that overlap is as big of a component as duration for a rough idle. Ramp speeds will help determine overlap. Sorry for the confussion.

[YENKO DEUCE REGISTRY]

Hey Pete;
I was there! So was 'SYCIWISH' and some guys from the Nova board, show was very good and the weather was perfect. I don't remember seeing the 6pak car though (?)

What's Dennis' situation? I've been wondering, send me a PM with an update [img]/ubbthreads/images/graemlins/smile.gif[/img]