LSA Question

[BSB67]

Isky Test of 106, 108, 110 LSA cams. Notice the 106 lost 3 hp at peak rpm.....but was up nearly 24 ft/lbs in the mid range

Thanks for posting,

I don't think this table is great evidence that tighter LSAs will makes more power or accelerate the car more quickly. This is because the testing was not done fairly. This is not uncommon. It is hard, time consuming, and costly to do so. This will generally not happen in an article for a magazine. Also, they usually over simplify for the largest audiance interest. The details they often leave out can be important.

First, take any motor and increase the cranking pressure and it will make more power. To be a fair test, the compression ratio for the 110 LSA cam should have been increased to match the 180 psi.

Second, the average hp under the shift-to-shift recovery rpm is the most meaningful. In the table, we don't know what the lower rpm is for the average through 7000 rpm. It could be well below the shift recovery rpm. The hp below the shift recovery rpm will favor the smaller LSA cam and will increase the avgerage, but will not representative of WOT operating range.

Finally, calculating the average hp to only peak hp rpm will always favor the smaller LSA cam. Hp above the peak hp will generally favor the larger LSA cam. We need to see the hp data to at least 7600 rpm, maybe 8000 and determine the best average for the shift/shift recovery rpm range for each cam LSA.

I don't know what the results would be if these items were addressed in the testing, but the average hp would certainly be much closer between the the three LSAs.

 

[gtxrt]

It is pretty much a fact that a tighter LSA makes more power and torque. not sure about 7600-8000 rpm but for a street driven car will never see more than 6500 rpms most likely 5500 would be most common. there is a compromise. a tighter LSA will produce a rougher and less vacuum at idle. with power brakes you need to be more careful. Comp cams sells more camshafts then anyone. all their cams are grind on a 110 LSA for a nice compromise for street driving and power. I always ran 109 LSA on my Buick nail heads because of the small valve heads. can't go wrong with a 110 LSA and if power is more important then idle quality then a 108 LSA would be good.

 

[BSB67]

I didn’t pick the motor or article for the example.

If you care about performance you would not shift at 6500 rpm a motor that makes peak power at 7000 rpm.

 

[gtxrt]

I didn’t pick the motor or article for the example.

If you care about performance you would not shift at 6500 rpm a motor that makes peak power at 7000 rpm.

yes that is one example but there is a lot of research and articles about tight LSA it is almost common knowledge that is the way to go. like I said I don't know about race cars and over 7000 rpms.

 

[dvw]

You won't see many if any 106-108 LCA in the range cams we run. Intake [email protected]"
Doug

 

[gtxrt]

You won't see many if any 106-108 LCA in the range cams we run. Intake [email protected]"
Doug

is that a misprint 106-108 LCA ?

 

[Gunner1]

I agree. A [email protected] with a 106 would have a tremendous amount of overlap. It would blow too much charge right out the exhaust valve on overlap. Don’t forget my main premise for the thread was a low compression, under 10.5 440 with heads flowing approximately 270 at .500 lift. That seems to be a safe assumption for a street mopar. The norm seems to all peak at about 5500 to 6000 max. Torque peaks near 3000. I just think that if I can build one more motor that would be a fun one. And Doug don’t forget that people like you who build and successfully race these cars are on the cutting edge of cam development. Not only that but you freely share your knowledge with us. So while the grinders May have more book learning the racers have a huge amount of practical experience. I’ve learned lots from reading your posts.

 

[gtxrt]

You won't see many if any 106-108 LCA in the range cams we run. Intake [email protected]"
Doug

they were talking LSA lobe separation angle your saying LCA lobe center angle or also called lobe center line.

 

[Curiousyellow71]

I agree. A [email protected] with a 106 would have a tremendous amount of overlap. It would blow too much charge right out the exhaust valve on overlap. Don’t forget my main premise for the thread was a low compression, under 10.5 440 with heads flowing approximately 270 at .500 lift. That seems to be a safe assumption for a street mopar. The norm seems to all peak at about 5500 to 6000 max. Torque peaks near 3000. I just think that if I can build one more motor that would be a fun one. And Doug don’t forget that people like you who build and successfully race these cars are on the cutting edge of cam development. Not only that but you freely share your knowledge with us. So while the grinders May have more book learning the racers have a huge amount of practical experience. I’ve learned lots from reading your posts.

Why stop at .5 lift? Most mopars heads I know of that flow 270-280 at .5 will still make good cfm at .6 or higher.
We just took one of our cars on a cruise. It was 240 miles for the trip and we are running .640 lift. Modern valve springs have come a long way since the days when over .500 lift was race only. Cam designs have also improved and we have a lot of options to pick from.

 

[dvw]

they were talking LSA lobe separation angle your saying LCA lobe center angle or also called lobe center line.

My mistake, I meant LSA
Doug

 

[33 IMP]

@dvw ,The obvious question wasn't asked yet Doug. So, what is the typical LSA for a 280° at .050 cam? (I'm betting 114-116).

 

[Dodge Bros]

There are several reasons 400 SBC might like the narrower LSA, and why BB mopars usually are wider LSAs. The SBC usually have quite a bit less port velocity at the same RPMs as the BB Mopar, and the Chevy has a lot shorter intake track than the big block mopar. The lesser rod to stroke ratio is part of the difference also. Compared to the 440, the SBC likes extra scavenging as the power band gets higher, and likes more overlap.

An engine with “good head flow and induction will like the wider spread”, is backwards of how cams usually react in a pump gas street engine. The bigger the CSA of the port, with more head flow, and the shorter the induction track (Chevy) the more the engine will probably respond to more overlap and like a narrower LSA. More head, while keeping the power band the same, needs less cam. The narrow LSA closes the intake sooner and builds more cylinder pressure, raising the port velocity. If you had a 280 cfm port on a 400 SBC, because of all the differences, even with a bigger cam, but still on a 105 LSA, the 440 would probably need a 350 cfm head to act similar to the 280 cfm heads 400 SBC with the Elgin cam. 294/300, 264/[email protected]” would be the equivalent size in a 440 using the same Elgin profile on a 105 LSA. If you took that 256/264 Elgin profile from the SBC and widened the LSA out to 108* on the 440, it would not only make more power in the 440 than the 264/272 105 LSA I mentioned, it would also likely do it with less head flow.

We have a SR that is 280/[email protected], 408 CID, and has a 104 LSA. That one has a lot of overlap!

My favorite pump gas street engines have wider 112 and 114 LSA with less overlap and more compression.

So the cam I’m using as an example here has pretty aggressive ramps. Only 30 degrees of ramp so that means 15 degrees from .020 rocker clearance valve on the seat till valve hits .050. Same for closing. Tight LSA but only 84 degrees of overlap. Don’t get me wrong. I know on a motor with good head flow and induction, a wider spread would be a better choice. On a drag car same thing. I’m just spitballin an idea for a mild parts dual plane 5500 rpm, torque monster Street machine that only sees the track once in a while. I’ve gotta see who does sft 904 lobes and look at their profiles. I really want to Dyno a combo.

 

[Geoff 2]

The Isky catalog has a number of cams 282 @ 050 on 106-108 LSA. So does the Crane catalog..

 

[BSB67]

My favorite pump gas street engines have wider 112 and 114 LSA with less overlap and more compression.

This is where I’m at with my stuff. It’s hard for me to imagine putting in a camshaft with 22 degrees less duration on a tight LSA would make my car faster. But I have not tested it.

 

[gtxrt]

the stock HP 440-383 cam was on a 115 LSA Mopar and really never turns on but just makes a flatter power curve. the HP cams had a lot of duration @.050 for a stock cam it must have needed that to calm down the idle and good vacuum for factory cars. what was the big talk about cam years ago from direct connection to go fast yes the 509 cam on a 108 LSA Mopar knew back then.

 

[gtxrt]

my first 68 GTX was all stock so I remember what that stock cam felt like. I saved my first performance cam card back in 1975 but never saved the 2 other Hughes cams 215-223, 224-230 and the crane 222-234 cam and the purple shaft cams they called them 509, 484, 474,430 and 2 lunati cams. you can see I started saving them again.

 

[Gunner1]

I believe that the vast majority of the guys on this forum have either stock or lightly ported iron heads. A few have stealths and less still Trick Flows or Indy’s. That’s my main thought process. Restricted flow for the given displacement. I’m loving the feedback. Pumping up the midrange is my point of interest.

 

[BSB67]

the stock HP 440-383 cam was on a 115 LSA Mopar and really never turns on but just makes a flatter power curve. the HP cams had a lot of duration @.050 for a stock cam it must have needed that to calm down the idle and good vacuum for factory cars. what was the big talk about cam years ago from direct connection to go fast yes the 509 cam on a 108 LSA Mopar knew back then.

Yep. Perfect cam for the motors of the time. 9.6:1 CR with 906 heads.

 

[gtxrt]

I believe that the vast majority of the guys on this forum have either stock or lightly ported iron heads. A few have stealths and less still Trick Flows or Indy’s. That’s my main thought process. Restricted flow for the given displacement. I’m loving the feedback. Pumping up the midrange is my point of interest.

in your first post you asked why most 440 guys run a wide LSA what is your opinion of a wide LSA is and are you talking street cars or race cars.

 

[dvw]

@dvw ,The obvious question wasn't asked yet Doug. So, what is the typical LSA for a 280° at .050 cam? (I'm betting 114-116).

I've run 2. 111 and 112. While not world beaters. They both made reliable power and are low maintenance on parts. Both a little north of 900hp. You would be amazed at a Pro Stock cam. 118 or more.
Doug