I plan to do a cam install hopefully this upcoming spring. After doing as much research as I could, I found what kind of cam profile will suit my purpose. Please help me design or choose an off the shelf cam that will fit my needs.

I see that on the stock LT1, RWTQ is very flat from about 2000rpm up to 4500 where it falls off quickly. This is bad, since there is far less torque in the upper RPM range, which is where you shift into when your racing. Basically, I want to extend the TQ curve to 5700 rpm and keep the low end relatively unchanged, or possibly better. I’m not concerned with peak HP in the least. I’m more concerned with extending the TQ curve and not loosing too much low end. I want flat torque. Basically, I want good torque from 2500rpm up to 5700rpm. A nice boost in torque down low would be a plus. I don’t want a drop off in torque in the high end.

What are my options, and why?

Thanks,
Dan

P.S., what make the TQ fall off so much at 4500rpm with the stock cam?

 

I don't think there are any off-the-shelf cams that will give you a flat torque curve from 2000-5700rpm. Plus, why do you want a lot of torque up top anyways? You need the torque to get the car moving, so low-end and mid-range torque is important. But once you are moving and you get to 5700rpm, for example, you need horsepower to go faster, and that is probably why they design the cams the way they do. Someone correct me if I am wrong.

 

That's not how your car accelerates. A car accelerates exactly the same as the torque curve, not the HP curve. HP is calculated from TQ. HP=TQ*RPM/5252 SO if you have more TQ, you have more HP. If you had a perfectly flat TQ curve, you can see that the only way you increase HP is to go higher in RPM. After 1st gear, high end TQ is all that matters when you're racing.

I don't want a discussion about HP vs. TQ. I really just want to know if there is a cam out there with flat torque from 2500-5700 rpm, and preferably has more TQ than stock.

Thanks,
Dan

 

The Comp Cams 07-502-8 might work well for you. You might call Combination Motorsports. They seem to know LT1 cams and have good prices.

Rich Krause

 

Thanks Rich. I'll give them a call. I've heard a lot of good things about them. I remember keeping the 502 in mind, from other things I've read about it. I'll search to see if I can learn more about it.

By the way, for bolt-ons, I plan on Long tubes, high flow cats, and exhaust if that changes anything; also a 52mm throttle body if needed.

Thanks,
Dan

 

Your car doesn't necessarily accelerate fasest at the peak torque curve, if it did, L98s would be eating lunch on everyone because they make so much torque. Your car accelerates by power, and power is horsepower. Why do you think Ferraris can run 12.0s w/ only 275 ft-lbs of torque, that's because they make that 275 ft-lbs at the high end, and using that formula, if your rpms are greater than 5252, it'll make more horsepower than torque. What you want is a good combination of high end torque w/ some mid range torque. The low end torque is good, but you will lose low end torque for the sake of the high end torque. What matters is your torque curve at the rpms you race at. If you're racing from 4000-6000 rpm, you want your torque optimized so the equation negates an increasing hp, then a slight fall off, then you shift. Yes, torque does move your car, but torque at 2500 rpm isn't moving your car while you race, the torque your car makes at 4500 rpm and higher is what is moving your car down the track.

So to answer your question....The CC306 makes a lot of power at the big end, not as much at the low end. Good middle torque cams are the CC305, hot cam, XE224/230, etc etc. Those will make good gains, but still keep good low end power.

 

Wanna bet? Your car accelerates purely on torque. HP is only a factor of torque. If you want more HP with the same amount of torque, rev it higher, but it's not going to accelerate any quicker. If the Ferrari's had constant torque from idle to redline, they would accelerate exactly the same all the way to redline(not taking into account wind drag and rolling resistance)

It does in first gear

Everything else you said I agree with. I know that I will probably give up a little low end torque for a flatter torque curve up high. What I want to know is what factors in the design of a cam tend to make the curve flatter rather than peaky. From what I've read, higher lift tends to make the torque curve more peaky. I'm wondering how other factors effect it as well.

Yes, the reason I am looking for a flat torque curve is exactly what you mention. That is why I asked the question. Torque high is where you need it when racing. I believe I said that already. I'm looking for a cam that has relatively flat torque from 2500-5700 rpm and was wondering if it existed.

Thanks,
Dan

 

My turn


Yes, a car does accelerate purely on torque, but the rate of acceleration is due to power output - "horsepower" as people have termed it. If your car accelerates best at the peak torque, then why don't you shift right after your peak torque range? Because power is based on two things - torque AND rpms. If your car decreases torque slower than the rpms, then you will keep building a power output, because the rpm is in the top portion of the formula, above 5252. This also explains why my car accelerates MUCH faster in 3rd gear at 5500 (300 rwtq = 314 rwhp) rpm rather than 4000 rpm (325 rwtq = 248 rwhp), even though the torque is higher at 4000. The power is optimized by the torque and rpm equation. It accelerates faster even though there is a higher wind drag on the car, cause there is a lot more power because of the higher rpms.

But I think for what you are looking for, those 3 cams I mentioned, and even a Comp XE230/236. I've heard really good things about that cam, good power through out the rev range so I've been told (peaks around 6200 if I remember correctly). There are guys on this board running the same cam (CC305) that I am with LT headers that are running mid 12s at 112+ with bone stock heads. I haven't taken mine to the track yet.

Those dyno numbers i Mentioned in this post were with the shorty headers - Jet Hot LTs are going in as we type (by me, wish me luck)....heh heh heh....

 

You only shift into the next gear when you a) run out of rpm, or b) the torque in the next gear is higher than what you are at in the current gear(this happens quite often when the torque falls off quickly at the end of the RPM range)

That is not true. You will have more acceleration at 4000 rpm. By the way, you don't accelerate faster, you increase speed faster, which is more acceleration.

Yes, I think his member name is 97Bowtie. I've seen the times also, very impressive. He did have a pretty good 60' time if I remember right (1.8 or so) I have been very impressed with the CC305. I also like the CC502 after looking at that dyno curves. Fairly similar to the 305. Right now, it's between the 502 and 305.

Thanks,
Dan

 

:rofl: Now thats funny. Want flat torque? Get a diesel, big block, or small supercharger. You arn't going to be able to maintain a torque curve like what you want just by adding in a cam, period. Better invest in GM's computer controlled valve system.

To still be making close to max torque at 5700 rpm, you'd probably have to get a cam that would spin your motor around 8000 rpm, then if you've got that cam, it wouldn't make ANY power under 3000 rpm.

With my cam install, I didn't gain any torque, I just pushed it up in the power band. My max torque is about 200 rpm away from where my converter flashes at (4000 rpm).

If you don't care about horsepower and just want to be in your torque band, just short shift.

Why does torque fall off? Its in the heads and cam. LT1's more of a truck motor than anything. If the frame and suspension would hold up, it'd tow a boat like no tomarrow. LS1's are a different beast. Combo of a more agressive cam and better flowing heads move the LS1's powerband up. Thats why they make max torque at 3200-3600ish rpm, and our manufacturer stats say we make max torque at 2400.

 

HAH, take it to another extreme, my car still makes more torque at 2500 rpm than 5500 rpm......BUT, there is no way in hell my car is increasing speed faster at 2500 rpm in the same gear as at 5500 rpm...

this argument is getting nowhere....

No one is going to convince the other of anything.

I have enough education in physics to understand the concept of acceleration, please don't tell me what acceleration is. Accelerate faster or more acceleration...whatever. Everyone knows the two can be interchanged when speaking of them.


EDIT :

Oops, you said you didn't want a discussion of HP vs TQ...sorry man got off topic....

CC502 or CC305 sounds good, I don't know much about the CC502...oh I did read the other day on a website (not a posting board) that duration affects the rpm range more than lift. There's a post about some website that talks about it...

 

Obviously you don't. Faster acceleration indicates rate of acceleration, which would be the slope of the torque curve. More acceleration is the level of torque, not the slope of the torque curve. The more acceleration, the faster your car will gain speed. It truly has nothing to do with horsepower. Horsepower is purely a measure of TQ and RPM. There is nothing magical about it. And yes, if you have more TQ at 2500 rpm, then you will have better acceleration, i.e. faster increase in speed, than at 5500 rpm.

Check out this site. He explains the concept better than I can in this post.
http://vettenet.org/torquehp.html


Yeah, I didn't really want to get into a discussion about HP vs. TQ, but here we are.

A lot of people just have the wrong idea about what makes a car faster, or where to shift gears.

Dan

 

crane 210/224

 

Stereomandan is correct. To maximize acceleration, you must maximize torque at the axles over the usable rpm range.

Acceleration follows the torque curve with maximum g-force (rate of acceleration) being achieved at peak torque. Acceleration falls off after that point, but, through gear multiplication, is still greater than it will be in the next gear higher, even at the torque peak. When torque at the axles in the current gear falls below the maximum that could be achieved in the next gear higher, you shift. It's as simple as that.

Example:
An engine* produces 235 lb-ft. of torque at peak (5,000 rpm). Torque then falls off to 140 lb-ft. by the 8,000 rpm redline.

Given a first gear ratio of 3.5:1 with a ring and pinion ratio of 4.10:1, the maximum torque at the axles in first gear is 235 lb-ft. (peak torque) x 3.5 x 4.1 x 0.85 (drivetrain losses), or roughly 2,866 lb-ft.

Given a second gear ratio of 2.0:1, maximum torque at the axles in second gear is 235 lb-ft. x 2.0 x 4.1 x 0.85, or approximately 1,638 lb-ft.

With a little more math, we can see that torque at the axles at redline in first gear (140 lb-ft. x 3.5 x 4.1 x 0.85 = ~1,707 lb-ft) is still higher than the maximum possible in second gear, therefore the car will accelerate quickest by holding first gear all the way to redline before shifting to second.

Ideally, the drop between gear ratios will put the engine at or around its torque peak, maximizing acceleration through all gears.

*A stock 13B-REW twin turbo rotary, just because I had the numbers handy.

 

What Mr. Jim said!

Rich Krause