Let's talk LSA

[plovett]

It is certainly application specific and Brent it going to kick my ass, BUT for MOST street/strip FE's in the 390-482 inch range a tighter lobe separation angle is going to get you more average power and better ET's.  And again it depends on the cam duration, but in general a 106-108 LSA is good for 90% of pump gas street/strip FE combinations if you are not looking for a smooth idle and good mpg.

JMO,

paulie

[blykins]

Why would I kick your butt?

I don’t necessarily disagree with you, but I think 90% is stretching it.

Remember, LSA just changes overlap.  There are other ways of changing overlap.

[plovett]

Why would I kick your butt?

I don’t necessarily disagree with you, but I think 90% is stretching it.

Remember, LSA just changes overlap.  There are other ways of changing overlap.

Because I am over generalizing.  I did say, "in general" though. 

[plovett]

Why would I kick your butt?

I don’t necessarily disagree with you, but I think 90% is stretching it.

Remember, LSA just changes overlap.  There are other ways of changing overlap.

I understand.  You are an engine builder and have seen many more varied combinations than I have.  Mine have just been my own.  Mine have varied from maybe 450 hp to 550 hp  in street combinations.   All around 428 inches.  So a narrow range.  I understand a 560 cid engine making 1000 hp might need a different LSA.  And that LSA is more a result than cause.

Anyhoo, just acknowledging that my statement is not applicable to everything.  Maybe not even 90%.  But in general, most street/strip FE's like a little tigher LSA than most catalog cams have.  IMO. 

[frnkeore]

Hmm, not exactly was I was looking for but, maybe it confirms that FE and or large V8's need a wider LSA than <400 CI? Any thoughts on that?

While I did mention vacuum, it was in passing and not really a consideration, regarding max average HP, in the upper HP range. For street engines, you can increase HP and keep vac, by adding CI. I'm not interested in "streetable" engines, just high output ones, 6000 rpm and up.

There has been no comment at all, regarding the SB engine, either in C or W form. I would have thought that there would have been many builds on that platform and why I put this in the Non-FE section.

Although I'm a "old school" guy, even at 75 yrs old, I've never lost the desire to learn and share info and my personal reason for this thread is that I'm putting together a 307 CI engine on a C80E block, with a internally balanced, forged crank. It will have a ~270-6 @ .050, roller cam, with ~6 deg more on the exhaust. Flat top 10.2 c/r pistons. Probably a Howard cam, with std rate lift. Howard have been very accommodating to me, in the past. I will try 2 sets of heads. Old school, 53.5cc HP 289's with 1.94 x 1.6 valves, then a set of alum 2.05 x 1.6 (as I remember 195 cc intake) heads that I bought 12 yrs ago. I bought those 63cc heads, to build a 351W so, I'll bring them down to maybe 53cc for this. I don't like pop up pistons.

I know I can get good HP numbers with 106 lsa but, I'm wanting to try 104. In any case, I'll install 2 cams with the same timing but different LSA. I'm hoping to get it on a local dyno this Spring.

I don't want to get to side tracked but, has anyone tried sinking the intake, to redirect some of the incoming a/f mixture, away from the exhaust?

Joe, if your reading this, do you have any thoughts on LC or intake valve sinking?

[frnkeore]

Why would I kick your butt?

I don’t necessarily disagree with you, but I think 90% is stretching it.

Remember, LSA just changes overlap.  There are other ways of changing overlap.

This and Brent's response is starting to confuse me. I suggest tighter LC and get push back and then some else suggests, it will do what I think it will do and there's agreement??? 

[My427stang]

Why would I kick your butt?

I don’t necessarily disagree with you, but I think 90% is stretching it.

Remember, LSA just changes overlap.  There are other ways of changing overlap.

This and Brent's response is starting to confuse me. I suggest tighter LC and get push back and then some else suggests, it will do what I think it will do and there's agreement??? 

LSA is just an angular measurement from the center of one lobe to another....it means nothing without the specific lobes, and even then, the information you are looking for is degrees of overlap, not LSA as a value

The better the head and supporting airflow pieces in and out, the less overlap you need.  With your planned iron heads, pick the ballpark RPM range and lean toward tighter.  104 might be much depending on use, a degree or two won't blow you away in the difference, but your combo should like tighter 

[Joe-JDC]

Yes, I have been watching the replies, and since you are building a 307 cubic inch engine instead of a FE, I will add my thoughts.  On my 303 Y engine, my camshaft was 233/240* @ .050", 106 LSA, installed at 99.75*.  The engine is 10.4:1 compression, and the lobe lift is .375" for 1.6 rocker ratio, with .009" hot lash.  My engine makes 390.8 tq @ 5400, 453.7 hp @ 6800, pulling to 7200 rpm.  I firmly believe that your camshaft selection of 270* is much too high if at .050" lift figure for 307 cubic inches.  My advertised duration is 284/292*.  Last year's EMC 375 Y block was higher compression at 13.0:1, and the camshaft was designed to peak at 6200 rpm since the crankshaft was a 4.000" stroke.  The camshaft was 254/260* @ .050, 104 LSA, installed at 101*, and made 561 tq @ 3800, 595 hp @ 6200, pulling to 6800 rpm.  Both engines could make more ultimate horsepower with a slightly different camshaft profile, but the average torque and average horsepower was highest with the camshafts installed advanced.  On the 289 SBF that placed second this year at EMC, the camshaft was a hydraulic roller with solid roller lifters with 242* duration on the intake, and it peaked at 6800 rpm, pulling to 7200 rpm for the dyno test.  Smaller engines do not need wide LSAs to make power, but they do to idle well, and produce vacuum for power brakes, etc.  We have dyno tested the same camshafts with LSA of 110, 111, 112, 113, 114*, and the horsepower climbed each time until the 114*, which lost 20 hp.  That engine made 560 hp, pulls the front wheels on the car, and the owner is extremely happy that it is not so hard to drive on the street with the 114* LSA.    Each engine family has its own sensitivity to LSA, ICL, ECL, and it takes dyno testing, or track testing to determine what actually works, not a catalog number.  My dynamic compression ratio with the 303 Y is 8.21, which will run on pump gas 93 octane quite well.  Joe-JDC

[blykins]

Hmm, not exactly was I was looking for but, maybe it confirms that FE and or large V8's need a wider LSA than <400 CI? Any thoughts on that?

While I did mention vacuum, it was in passing and not really a consideration, regarding max average HP, in the upper HP range. For street engines, you can increase HP and keep vac, by adding CI. I'm not interested in "streetable" engines, just high output ones, 6000 rpm and up.

There has been no comment at all, regarding the SB engine, either in C or W form. I would have thought that there would have been many builds on that platform and why I put this in the Non-FE section.

Although I'm a "old school" guy, even at 75 yrs old, I've never lost the desire to learn and share info and my personal reason for this thread is that I'm putting together a 307 CI engine on a C80E block, with a internally balanced, forged crank. It will have a ~270-6 @ .050, roller cam, with ~6 deg more on the exhaust. Flat top 10.2 c/r pistons. Probably a Howard cam, with std rate lift. Howard have been very accommodating to me, in the past. I will try 2 sets of heads. Old school, 53.5cc HP 289's with 1.94 x 1.6 valves, then a set of alum 2.05 x 1.6 (as I remember 195 cc intake) heads that I bought 12 yrs ago. I bought those 63cc heads, to build a 351W so, I'll bring them down to maybe 53cc for this. I don't like pop up pistons.

I know I can get good HP numbers with 106 lsa but, I'm wanting to try 104. In any case, I'll install 2 cams with the same timing but different LSA. I'm hoping to get it on a local dyno this Spring.

I don't want to get to side tracked but, has anyone tried sinking the intake, to redirect some of the incoming a/f mixture, away from the exhaust?

Joe, if your reading this, do you have any thoughts on LC or intake valve sinking?

I have spoken several times in this thread alone about Cleveland heads.  If you need more specific info, email me, or you can join my Cleveland forum for a discussion.

270 at .050” for a factory head?   Why?  There’s a specific trend with cams and head flow.  You keep adding hp and rpm until you reach a specific point where all you are doing is holding the valve open and nothing else is coming in.  My guess is that you’d make more power with a much smaller cam.  The duration split depends on the amount of overlap and how well the exhaust functions relative to the intake.  A 6 deg split is what you commonly see with shelf cams.

[blykins]

Why would I kick your butt?

I don’t necessarily disagree with you, but I think 90% is stretching it.

Remember, LSA just changes overlap.  There are other ways of changing overlap.

This and Brent's response is starting to confuse me. I suggest tighter LC and get push back and then some else suggests, it will do what I think it will do and there's agreement??? 

I’ll tell you the same thing I’ve said multiple times during this thread:  it depends on a ton of other stuff.  Have I seen torque pick up on certain combinations with a tighter LSA?  Absolutely.  Does it happen every time with every engine?  Nope.

[Joe-JDC]

Never sink the intake valve lower than the exhaust!  Detonation central, cracked exhaust valves, if anything, sink the exhaust lower than the intake seats.  Flows better.  Joe-JDC

[frnkeore]

Thank you, very much Joe, for sharing that.

To be a little more specific, my goal is peak HP at a minimum of 7600 rpm, with 1200 cfm of carb (I may also try a Victor Jr & 850 carb) in a ~1350 lb car. I have a old Formula Car that I will cut off back of the roll bar and add the engine, C4 (if it will take it) and 9" gears, as a unit. It will be a drag racer. That, after the dyno work is done.

Brent, you'll note that I will not use the 289 heads, in the end result but, I will heavily modify the exhaust ports. I have them and will try them, to see how they compare with the 2.05 x 1.6 heads. I don't expect them to get very close to the aluminum heads BUT, they did run at that rpm level, in the 60's and 70's in Trans am, Shelby Cobra's and Can Am. Off the subject but, Gurney ran his 3V Westlake heads at Indy and placed 2nd, one year. I loved what Gurney did with the SBF.

[blykins]

Thank you, very much Joe, for sharing that.

To be a little more specific, my goal is peak HP at a minimum of 7600 rpm, with 1200 cfm of carb (I may also try a Victor Jr & 850 carb) in a ~1350 lb car. I have a old Formula Car that I will cut off back of the roll bar and add the engine, C4 (if it will take it) and 9" gears, as a unit. It will be a drag racer. That, after the dyno work is done.

Brent, you'll note that I will not use the 289 heads, in the end result but, I will heavily modify the exhaust ports. I have them and will try them, to see how they compare with the 2.05 x 1.6 heads. I don't expect them to get very close to the aluminum heads BUT, they did run at that rpm level, in the 60's and 70's in Trans am, Shelby Cobra's and Can Am. Off the subject but, Gurney ran his 3V Westlake heads at Indy and placed 2nd, one year. I loved what Gurney did with the SBF.

A 7500 rpm peak is easy.  Will take a lot less cam than what you’re thinking.

[frnkeore]

Brent, I said a min of 7600 not 7500. So tell me how much duration I need to peak @ 8000 and still pull to at least 8300?

That's where I'm try to go.

Also, the modern day cam catalogs list 10 - 12 more degrees, ex duration. I'd rather close the ex earlier and start building compression then work on ex flow.

[blykins]

Well, then you need a minimum peak of 8000, not 7600.

Tell me what the heads flow.