Given the specs on 2 cams are exactly the same except for the LSA, why does some with the larger LSA push the operational RPM range up and some go down? For example, I was looking at the Howards cam page and they offer several roller cams with the same specs except for the LSA's. Here are some examples of what I mean:

Max Torque .525 .532 258 268 226 234 108 .000 .000 110325-08 98212
Hydraulic Roller Tappet 2000-5400 Choppy idle, Street performance usage. 2500+ stall.
Max Torque .525 .532 258 268 226 234 110 .000 .000 110325 98212
Hydraulic Roller Tappet 2200-5600 Rough idle, Street/Strip performance. Strong mid-range. 2500+ stall.

Max Torque .510 .533 288 294 232 236 110 .000 .000 110255-10 98212
Hydraulic Roller Tappet 2200-5800 Rough idle, Street/Strip performance. Great low to mid-range torque and power.
Max Torque .510 .533 288 294 232 236 112 .000 .000 110255 98212
Hydraulic Roller Tappet 2000-5600 Fair idle, performance usage. Great mid-range torque and horsepower.

Max Torque .533 .548 294 302 234 242 110 .000 .000 110265-10 98212
Hydraulic Roller Tappet 2400-5800 Rough idle, Hot Street and Bracket Racing. 10.0:1-up CR advised. 2800+ stall
Max Torque .533 .548 294 302 234 242 112 .000 .000 110265 98212
Hydraulic Roller Tappet 2400-6000 Lopey idle, Hot Street and Bracket Racing. 10.0:1-up CR advised.

I am thinking about changing the cam to one with a little more top end. Right now the Comp 270H is ok, but I got it when I had the PG and a stock stall converter. Now the TKO gives me a little more flexibility on the low end. I don't have to worry as much about the launch RPM being as low or the engine bogging due to the low stall speed. I was thinking of going with a roller with an RPM range somewhere around 2000/2500-6000 or so. Maybe the Comp 280HR which gives me the same duration(224/224 @.050") as I have now, but ups the lift to 525/525 or the Comp 286HR which gives me 230/230 @.050" with 560/560 lift. What do you guys think? Thank in advance.

I am running one of Udharold's billet grinds after a Comp cast roller going bad. Upon Harold's recommendation he suggested I use his 231/236 @.050, 112 LSA w/ .550 lift in my 10.3 motor. Got the best of idle here and motor still pulls strong where I need it. I cruise my car many miles and get about 23 mpg with the TKO. Even has AC. Another reason I chose Harold's cam is because it has the cast iron Everwear dist gear.

Don, a link for Harold?

Don, a link for Harold?

This is all I have on Harold at the moment, I have some invoices at home if needed. Pdq I think has more info. Harold hangs out at the Chevelle site.

Call UDHarold here

(662) 562-4933

Thanks! It's time to shop for that solid roller.

I am running one of Udharold's billet grinds after a Comp cast roller going bad. Upon Harold's recommendation he suggested I use his 231/236 @.050, 112 LSA w/ .550 lift in my 10.3 motor. Got the best of idle here and motor still pulls strong where I need it. I cruise my car many miles and get about 23 mpg with the TKO. Even has AC. Another reason I chose Harold's cam is because it has the cast iron Everwear dist gear.

Don, all the reading I have been doing lately has said that it is time to get away from the dual pattern type cams. With the flow rates of todays great heads, the days of dual pattern cams are all but gone. What do you think about this? Why did he suggest the 112LSA? Was it for idle quality? Also, I see you state you get 23mpg with the TKO. What rear do you have? I have 4.10's and so far the best I can get from mine is around 250 miles per tank. Some of this is around town and some one the open road. Is there something I am missing here or do you run a higher rear? Thanks.

There is alot that plays into fuel economy. You cant just take it as he has the same cam with a TKO so you will get similar perfromance and economy.

As for those cams those companies must be on something. The tighter the LSA the rougher the idle and will result in more low end torque because of increased overlap area which helps to better fill the cylinder at lower rpms.

112 is usually a good LSA gives you a good idle sound and will be a good all around power band. I usually go for the 110 LSA sounds better and a little more torque. Really depends on what you want high end or low end. It really has no affect on the area under the curve it just shifts the curve around a point.

The dual pattern cams are being phased out. Yet I do not see them being phased out on gen I or II motors. They are still needed on these motors not on Gen III + the head geometries and flow coefficients are better which results in not needing a dual patter cam. The Gen I/II's still do in my opinion unless you have SB2.2 or some how get gen III heads on the bore. Also Gen III+ still use dual pattern cams for boosted applications.

I think the 230/230 cam would be good but you didn't tell me your heads.... I would like for something more like 230/234 somewhere around there. After all if you move the EVC angle out you can increase overlap (Decreasing LSA) and still maintain the same overall duration from EVO to IVC allowing similar flow characterisitics and help push out the air with an early opening to assit in blow down. Regardless still think dual pattern is important with the 1 2 1 exhaust geometry.

The heads will be AFR 195cc comp. 2.08 intake/1.60 exhaust. The articles I have read seemed to be pointing at the Gen 1/2 engines, but this is with an aftermarket head, much like the AFR or Brodix. Stock heads like the Vortec do indeed need the dual pattern cam, but the flow capabilities of the AFR and Brodix do not. The extra help needed by a stock head on the exhaust side is required by an aftermarket head so the use of a dual pattern cam is not required as well. At least this is what the cam and head builders are saying. I do not present myself as knowing the in depths of head design or cam design so I cannot say one way or the other.

As far as MPG, I agree with there being additional info needed to make a 100% exact comparrison, but there should be a way to make a educated guess as to the comparrison by cam, tire diameter, rear gearing, intake/carb or EFI and tranny setup. If I remember correctly, Don runs TBI on his motor. That may be why he is seeing such a dramatic increase in MPG compared to my setup.

I always thought that overlap actually DECREASED low end grunt due to the lowered cylinder pressures? I do know that overlap is one of the causes for the rumpety rump of an engine, but the more overlap, the less cylinder pressures, thus the less low end grunt you get.

While that makes sense, it's actually the opposite.

This is my experience with LSA, given the Lobe Profiles are similar: The wider the angle Lowers and Broadens the Torque Curve within the RPM Range, slight loss of Hp on the Top End - Suitable with Manual Transmissions with Taller Gears, for Marine use, Road Racing and HWY Performance. The narrower the angle will move the Torque Curve more to the Top End of the RPM Range and gives slightly more Hp - Suitable for say; Circle Track (keeping the RPM up coming out of corners) and Drag Racing with Hi-Stall Converters and Lower Gears.

Personally I'm not into the Street or Drag Race but love that back Winding Road with lots of Hills that go nowhere. I like a Cam Profile promoting DCR on the intake with higher lift and longer duration on the Exhaust with a 112 LSA. I don't think you could do better then Harold's 502A1LUN (278/290 244/255 @ .050" .630"/.630" 112 LSA which would be Great for 10.2:1 .019 Gasket & .044" Quench 460BBC running a M21 and 3.08's - perhaps .636" lift on the exhaust = HINT ;o). He has an optional Exhaust Profile for this cam at 278/285 244/250 @ .050" .630"/.630" 112 LSA (This Exhaust Profile may promote detonation under load and suited to say a 9.5 static) The Comp Cam 933-16 are about perfect for say 049 or 781 Heads hitting 200/500 lbs right on fitting the Spring Pocket and installed at the stock 1.88"

For a HFT I liked the Comp Cams XM278H-12 with a 9 to 10 static (278/293, 234/244 - .564"/.566" 112 LSA - Man that cam sounds mean at Idle)

Don, all the reading I have been doing lately has said that it is time to get away from the dual pattern type cams. With the flow rates of todays great heads, the days of dual pattern cams are all but gone. What do you think about this? Why did he suggest the 112LSA? Was it for idle quality? Also, I see you state you get 23mpg with the TKO. What rear do you have? I have 4.10's and so far the best I can get from mine is around 250 miles per tank. Some of this is around town and some one the open road. Is there something I am missing here or do you run a higher rear? Thanks.

Who am I to argue with Harold Brookshire, I went to him for answers and he unloaded the truck. He being a cam designer , grinder, end user and providing many satisfied customers.
I told him what I was running with Comp,XR282HR(that went flat on the fuel pump lobe) , he indicated it was good but he could do better with his design and with his approach on opening and closing ramp speeds. He told me my motor would idle better with the 112 LSA and have a broader range using the AFR 195 S/E heads. I gave my gearing info and that was it.

I do understand this topics about dual and single pattern cams but he gave me what he recommended.

After 2008 power tour, I did a tear down, rechecked all including the old orginal Comp retro rollers. I inspected his Everwear cam dist gear against my GM style gear as well as the roller tip fuel pump push rod. All was perfect.
His grind was the 231/236 x 112 LSA with .550 lift. He also agreed with me about running 155# spring pressure on this hyd cam. He mentioned that most people dont adhere to this rule as hyd roller lifters full of oil, can get heavy at engine speeds above 6500.
The addition of the premium larger, taller valve springs that Mike Lewis Racing recommended with my new heads, fell right into the package.

I could instantly tell the differance between the two cams on pulls from stop.

23 mpg, 3.73 gear with TKO OD. I can't complain. Lots of crusing behind me and much more in front.

Forgot to mention, JimM got a cam just like this. He is happy.

You need dual pattern man on your AFRs. Call tony he will say the same thing. While they flow better they are still the same basic architecture that limits the GEN I/II heads. I have 210 AFR's on my 383 running a 248/252 duration at .05 and 286/292 advertised duration with a 110 LSA and just over .600 lift. AFR even said this would be a great choice for the head flow characteristics. I am running a single plane intake too.

Tighter LSA equals more torque..... PERIOD. ITs not the other way around.
http://www.compcams.com/Technical/FAQ/LSAproperties.asp
Comp Cams tells you how it is right there.

It takes more overlap to extract residuals that cause dilution and a loss of power at lower rpms. Thus the tighter angle results in higher VE because of the reduced residual (burned mass) present in the cylinder during the power stroke. While this will hurt economy because residuals at part load = BSFC because of reduced pumping loss for cylinder filling it will result in a torque increase.

Wow! I love this site,,,

Tighter LSA equals more torque..... PERIOD. ITs not the other way around.

I agree more torque but within a narrower range approaching the top end of the RPM Curve - Ideal for a Hi-Winding SBC with Low Gears and an Automatic at the Strip or say a manual on Circle Track where you want that torque at Hi-Revs approaching and exiting the Same Corner - something like running the 1/8 mile over and over again. LSA choice depends what your game is and where you want the torque to come on ;o) A wider LSA also promotes Exhaust Scavenging. Scavenging permits the engine to maintain a rev position while you make up your mind which gear to select and the Manual will slide slowly into a gear. You have more clutch time at higher revs suited for Road Racing where you need to CONTROL power to the Asphalt when carving or drifting through corners with various radius's and every straight is a different length.

I ran an Sigerson SFT 296/302, 258/264 @ .050” - .563”/.563” 108 LSA in my 11:1 327, M20 to 373's. Man that would pull hard on the top end and didn't seem to top out but with 308's, it was a Dog. With 308's that combo would likely prefer the old 30-30 cam with a 114 LSA. The tighter the LSA you need Hi-Ratio Gears for the torque to be effective but the power band is narrower unless you can stretch the RPM Range with a strong engine that will rev beyond 7500rpm.

We are all looking for that Winning Combination for the application or we would not be in the Sport. I wonder if they will ever design a Variable Reed Valved 4 Stroke - LOL

Haha you never know there are so many ridiculous concepts I have seen. I even saw a block that had hinges in it for variable compression ratio. Have also seen hydraulic pistons to vary compression ratio. Seen dual pattern lobes that can actuate to different lift and timing events. Crazy stuff. If you think of it someone probably tried it.

Side note: You are increasing scavenging at low speeds with tighter LSA thats why the torque increase, although Z15 is right. Scavenging is largely dependent on speed and duration overlap.

Scavenging is largely dependent on speed and duration overlap.

Thats were the the longer duration and higher lift comes in on the exhaust valve. Wider the LSA the flatter the Torque Curve. I've a fetish about holding the revs up, slipping into a lower gear and letting the clutch without stretching the rods or blowing the clutch. You should try that with a heavy SR BBC that tends to go straight and fights the corners. A blip-in 108 LSA doesn't help the situation. I'm still a Northern Ontario Kid at 62 with endless miles a winding Hard Top that go nowhere and gas stations are few and far apart - LOL