[TOP 452]

What happens
to shift points and power band when going to tighter LSA? Thanks

[TOP 452]

What happens
to shift points and power band when going to tighter LSA? Thanks

[DiamondJim]

I tighter LSA will "Squeeze" the hp cuve and it will show peak hp at a slightly lower rpm. Area under the curve will be less but peak hp will be more. Hope this makes sense. -JimT

[Ken French]

Diamond Jim,
You are accurate with the exception of lowering the HP peak. It all depends on the cam placement: i.e. centerline. Ken

[TOP 452]

Cam is 104lsa and installed at 102

[DiamondJim]

Ken, I said that with a tighter LSA peak hp will occur at a lower rpm. Also keeping all other parameters the same, tightening the LSA will make more hp in a narrower band. itnop, post more info, 104 is really tight. Is this race only motor? -Jim

[TOP 452]

Diamound Jim Yes it is a race only motor. 65 GTO WT3160 462ci Elde heads flow 330cfm at .700 Car has run 9.510 at 138.90mph at 1700da.1.33 60ft times.Victor with 1095 dominator 2"header.Best 60ft 130.4.Going up to ttrack tommorow hoping for some good air.

[Ken French]

Hey itnop,
try retarding that cam to around 108, I'll bet you'll fly. Ken

[TOP 452]

Ken French
Thanks for the advise. Why do you think retarding the cam to 108 will help ? Did you use to go to NE Dragway? I rember a blue GP afew years back.

[Ken French]

itnop,
with a tight lobe spread like that, retarded around 4 degrees, will create an INTENSE power peak. The converter, if you have a good 8'', will flash beyond 5500rpm. This will render all the torque gained, at the installed 102 centerline, useless. Lay it back to get that available H.P. PS: yes, I still own the same GP, only it is now a tube chassis. It will be done for the spring time. Thanks: Ken

[Shaun]

Tightening the LSA advances the Intake and retards the Exhaust. That increases overlap. It also increases the cylinder pressure in the motor's power band. It will rob the power band from the bottom and the top and squeeze into the mid range. Yes it does make the power band peaky. It also kills Intake valve to piston clearance. You have to consider rod to stroke ratio's when deciding on LSA's. The better the rod ratio is, the bigger the motor will interpret everything from the Carb to the Hedders to be. This includes the Cam. The longer rod will also make a wider power band as well as take spike out of the mid range with any given cam. This is helpful info for cars with narrow tire rules. IT will reduce CFM demand (2BBL/stock Exh manifold Guy's: tight LSA's are NOT the answer) and so many more things that I wont wast your time with here. Rod ratio's and LSA's is where you can really make a motor a lazy accelerating DOG if you don't consider that when deciding on LSA's. Generally, if you lengthen rods, step off on the seat timing a bit and tighten the LSa just a bit if your goal is to keep the same general characteristics that you had before you stuffed a longer rod into the motor. You can also step off of the seat timing considerably if you widen the LSA significantly. You also create more piston dwell with longer rods, so if you really made a big rod to stroke ratio change, you should consider slowing down the peak acceleration rate of the cam so the motor can keep up with it. Especially if it has a big intake runner.

[Shaun]

Another thought is: A cam that you are retarding to gain top end power, you can pretty well bet (in most cases) when you do this, and the motor picks up on top, you either don't have enough cam in the first place, the wrong LSA for your power range in that the cam has too narrow of a band (or too much ring gear) or the motor is simply running out of fuel due to an insufficient fuel supply. I see this in particular very frequently. So, what does the guy do? He retards the cam to compensate by delaying everything. (shifting the power band up) I feel this practice (in most cases) is Band Aiding the situation and is what I refer to as tuning the motor and cam to the fuel system rather then the other way around. You might be surprised about the things you will learn about your fuel delivery from a fuel pressure guage during a WOT run.

As far as major engine components are concerned, camshafts are realativly inexpensive pieces, but understanding them and what they do is So critical. Perhaps more than any other single internal engine component! I can't say it enough: You get what you pay for. There is so much more then just being loaded with massive advertising Dollars. Sure that will sell cams, but most of the time it is to a guy who likely has nothing to compare to ( it is his first or second Rodeo) nor does he have any real experience. Therefore he thinks he has real power. That guy doesn't know what real power is. Most of the time this Grass Green buyer is relying on some high turn-over rate Tech on the other side of the phone line equipped with a catologue in hand who likely isn't a designer or a builder.

[EnergyFX]

Great info here guys. Thanks

[mikeb]

I just went from a 230/230 .480/.480 @ 110lsa to a 246/253 .516/.525 @ 108lsa. Engine is a mild 455 in a 79 bird; race weight is 3600 with me in it. I regret that I did not have time to degree it (I found the cam gear threads almost stripped in the old cam and had to swap cams in a thrash to make a race - this cam was on hand and in it went).

The interesting thing about this cam is apparently the power band range did move down even with the larger duration numbers. On the old cam I averaged 1.63 60's most of the time. New cam the 60' is exactly the same but 1/8 ET is off by about .1 and 2mph. Old cam was shifted at 5500; new cam works better by shifting at 5000.

I'm intrigued by this cam for some reason. I'm going to switch to a little tighter converter and may try some rhoads lifters and a performer rpm to see what happens.

[johnta1]

MikeB, I would say you're having a problem like Shaun talked about.
With that cam I would think you would make more power and at a higher rpm zone.
Might check your valvesprings,fuel system etc.

itnop, that cam wouldn't be for a Super Stock 455 SD would it?

[mikeb]

Valvesprings are new comp 995's as specified for the cam.

I've tried a few things after installing the cam and the only thing that picked it up was short shifting.

I enjoy a puzzle and now I have one and i'll eventually get to the bottom of this. I agree; this is not what I expected from this cam. Fuel system delivery problem is certainly possible as I have a marginal system in place now and have plans to redo it.

[DiamondJim]

Mike, If you can you really need to degree your new cam. The nearly 20 degrees added duration should have moved power up 1000 rpm(if both cams installed the same). Tightening the LSA from 110 to 108 will bring it back down some but not that much. Rule of thumb is power moves up 500 rpm(roughly) for every 10 degrees duration added. -Jim

[mikeb]

Jim - i'll probably take a look at it this winter and see where it really is. Still, everything i've ever read about advancing or retarding a cam suggests that the torque peak is only moved a few hundred rpm either way so I still think there is something else at work here.

On a dynosim plot the graph for this cam matches exactly the graph for the old cam with more HP & torque and the peaks are at the same rpm. This cam looked really good on paper

[Shaun]

Your old [email protected] cam could be the same sat .050 with 20 degrees less at the seat and 10+ degrees bigger at .200 if you go to a solid.
It would also run from idle to 6000 and have 17" vac. Why are you all buying Hyd cams accept for the ones who don't have adjustable valve trains? There is not a high adjustment issue with solids like everyone thinks. Just use a good lock and know how to make it LOCK, and there won't be but a couple of adjustments a year, but you will have a cam that has nearly double the ramp intensity.

[Shaun]

Sorry, I am getting in a frienzy here. Couldn't ya tell.

The other thing I need to stand on my box and preach about is: Stop comparing cams at just .050. That is like comparing two 5000square foot houses to each other, but only comparing the Powder Room. There is so much more to comparing 2 cams to each other then just looking at the .050 numbers. For starters, you need to look at the .200 numbers and the advertised numbers. Be careful with advertised numbers because they will deceive you because some hyd cams advertise at .006, while others advertise at .0045. The .006 advertised is much bigger at the seat in the motor then on paper. This is even more true when Hyd cams have thick oil in them. The shorter the seat number is and the bigger the .050 and .200 number is, the faster the ramp is, and the more power the motor will have at ALL rpm's. It will have a wide band. Remember that early intake opening from big seat timing cams kills and delays cylinder filling and therefore delays the power band. THis is known as reversion in the intake port, and is the worst enemy of filling the cylinder with a dense charge. A port that starts flow late will never catch up. Why not a solid lifter cam that is 15+ degrees smaller at the seat then the Hyd, but 10-20 bigger at .050 and even bigger still at .200? Does this make sense?