Let's talk LSA

[frnkeore]

I'm put this in the Non FE section but, I'm also very interested in how people are tuning the FE with it.

I know a little about it but, not near as much as I would like. I would love to have feed back, if available, of dyno tests, changing only the LSA of the cam, in both high and lower rpm cams.

Some things that I know about are:
1. Lower performance cams have wider angles, usually 114 - 110. Higher performance cams 112 - 102.
2. I understand that wider spacing, Get you more vacuum and torque at the lower end, giving better behavior on the street but, with increased duration, where does it detract from the top end and what does it do in the middle?
3. Closer spacing gives more overlap but, generally more HP at the top of the torque, HP curve and I believe maximizes the average torque, between the max torque and max HP rpm but, really kills any hope of low end response.

What are your thoughts and experiences about LSA and how to use this tuning feature? Does it effect the the FE in different ways? I note that a lot of cam makers, use a little wider LSA on their FE cams.

[blykins]

It’s all application specific and isn’t as generalized as what you think.

One of my pulling truck engines uses a 119 LSA, makes 1200 hp at 8500 and 810 lbft of torque.

I use wider LSAs on my FE hydraulic rollers because aggressive lobes cost hp with heavier valvetrain.  Less aggressive lobes have more overlap and we have to control it.

[frnkeore]

Is the 1200 HP engine, naturally aspired?

Can you explain to us, what effect the LSA has on a aggressive. Lobe shape? It spread the spring load over wider range by a few deg, is that it?

I realize that you need to build, as much as possible to your end result and not fight against the cam but, build to it. The cam is the heart of the engine.

If the 1200 HP engine, is naturally aspired, I'd very entered in the difference in the torque curve if, a 104 LSA where exchanged for the 119.

[chilly460]

I think LSA is considered a more major influencer in cam design because people are accustomed to looking at shelf cams.  Shelf cams are fairly uniform so, in that case, the changes to LSA can have a fairly distinct change in the character of the cam.  You end up with generic trends such as LSA being tighter on “racier” designs as a universal rule

That said, when you get a custom cam, the LSA is more a byproduct of plotting the lobes, not a driver of where the timing events are placed if that makes sense

For an FE which has the heavy valvetrain, you have a less aggressive lobe with longer seat events to have gentler action, it’s going to have more overlap.  If you need power brakes or better idle or don’t want to overscavenge the intake if it has a good port, you’d put a relatively wide lsa on the cam. 

Just guessing, but seeing the rpm peaks on that pulling motor, guessing it’s got a ton of duration, to a point that overlap was getting so large it was beneficial to widen the lsa to decrease overlap. 

LSA really comes into play when you need more or less scavenging effect IMO, otherwise it’s more a result of other calculations not a driver of those calculations

[blykins]

Is the 1200 HP engine, naturally aspired?

Can you explain to us, what effect the LSA has on a aggressive. Lobe shape? It spread the spring load over wider range by a few deg, is that it?

I realize that you need to build, as much as possible to your end result and not fight against the cam but, build to it. The cam is the heart of the engine.

If the 1200 HP engine, is naturally aspired, I'd very entered in the difference in the torque curve if, a 104 LSA where exchanged for the 119.

The 1200 hp engine is naturally aspirated.   It's a max-effort 556ci engine. 

Chris hit on a lot of it, I use LSA to simply control overlap.   

A customer with a 380 cube Cleveland came to me asking for a camshaft as he thought he had maxed out his combination and was looking for improvements.   He was running a custom Crower solid roller, that was spec'd by Crower.   I kept his durations the same, lift the same, but actually decreased the overlap and the car picked up almost a tenth in the 1/8th.   Overlap can make/break vacuum but it can also make/break hp.  If you're holding both valves open together for too long, all your power is going out the exhaust.

I like when guys think outside the box when it comes to camshafts.   My biggest pet peeve is when guys look through cam catalogs, read the notes below, and think that those notes apply to every single engine, every single head/intake combination, etc.  My second biggest pet peeve is all the "universal" cams out there.  If you look through some of the catalogs, the same exact camshaft (advertised duration, .050" duration, LSA/ICL) is available for every engine family, from SBC to BBF.  Universal works, but it's by no means optimal. 

If you look at a lot of high rpm, large cubic inch competition engines, you will see LSA's from 118-124, and that's for the reason we've been discussing. 

[My427stang]

I am with Brent completely.  LSA is only a design/machining term to determine overlap based on a lobe pair.

It's all about valve timing and the effect you want, bills you need to pay.  I have been spreading centers lately on these 461s on purpose.  I do this to keep overlap in check to keep vacuum up and part throttle behavior for the restomod power brake builds.  A quiet hydraulic roller also has a bunch of advertised duration compared to a flat tappet, so you can see the two CJs I did were at 114, however, a smaller cam in my EFI 461, I narrowed to 112, because the lobe let me, and it actually has less overlap, not only for the vacuum, but in that case to leave the exhaust clean for the EFI O2 sensor.

I have a 462 tunnel wedge build coming in, no power brakes, good gear, that one will likely have a bit more overlap as I don't have to be bound by idle vacuum as much.  I expect the curves to be steeper and higher, more peaky if you will, because at some range, the exhaust will be pulling harder on the intake than it would with less overlap

Chilly is spot on with the need for overlap.  I think a rule of thumb though can be, the better the head, intake and exhaust combo, the less overlap you need. The problem is, defining "better", it's not bigger, and not even peak flow alone, it's efficiency and matching the rest of the build

[cjshaker]

My biggest pet peeve is when guys look through cam catalogs, read the notes below, and think that those notes apply to every single engine, every single head/intake combination, etc.  My second biggest pet peeve is all the "universal" cams out there.  If you look through some of the catalogs, the same exact camshaft (advertised duration, .050" duration, LSA/ICL) is available for every engine family, from SBC to BBF.  Universal works, but it's by no means optimal. 

A byproduct from the days when custom cams weren't an easy option like they are today. Remember, there used to be 3 choices in the days of flatheads, hence the term 3/4 or "full race" cam. Things sure have changed.

[BattlestarGalactic]

Remember the old 1980's Summit catalogs where the options for cam were "if you want the baddest sounding hot rod"?  No where did it say "most power".

[frnkeore]

I hadn't intended this be only about FE's, that's why I put it in this section but, I'm happy to have FE info.

Brent, could you give the rpm of the 810 ft lb of torque and explain this a little more?

"I use wider LSAs on my FE hydraulic rollers because aggressive lobes cost hp with heavier valvetrain."

The only difference that I can see, between the FE and say a Yates or SB2 engine, is the length of the push rods but, there valve stems are longer than most FE's. Now a days there is really no reason for the valve train, to be any heavier than a NASCAR engine.

For street engines, because of the length of the valves and expense to replace them, I can see people keeping the 3/8 valve stems but, for anything else, 5/16 or 7mm valve stems would be more desirable.

I was also hoping to get input on SBF, both W&C. I'm not a canted valve guy but, with that type valve angle, the flow is not as direct from the intake to the exhaust. That being one of the big advantages of the hemi and 4 valve, pent roof designs.

The race engines that I ran, where of the latter design and we ran 102 lsa on those, at 8500 - 10,000 rpm.

The last I new, the canted valve, NASCAR engines were running 106 lsa at 9,000+ rpm but, 106 lsa has been standard for more than 40 years in both, Ford and Chev wedge & canted engines. One cam maker, John DeLong, promoted 108 lsa for short track engines, over the 106 lsa, that was univeral. Presumably for a little more torque, exiting corners. I sponsored a  a car that used his cams. He was one of the great, early cam grinder and made a gear drive, that I liked, too. 

Increased vacuum is not what I submitted this thread about. What I'm interested in, is how to pick up torque, using lsa, between the max torque and max HP in the top 2000-2500 rpm range, whether that be 6,000 or 10,000 rpm, as that is where it counts, in race engines.

[blykins]

Cup engines probably used some 106 lobe centers, but they used everything in between depending on the track they were on, and how the engines were set up.  That’s kinda what I’m getting at, is there are no real generalizations that you can make, because each component changes the need for something else.

FE valves are heavy.  Factory valves are 3/8” diameter and are long in comparison to SBF, SBC, even some Cleveland and BBC applications.  In addition, on adjustable rocker arms, you have a lot of weight hanging off the back of the rocker arm, where most rockers on other applications are stud mounted and the adjuster is on the fulcrum.

On hydraulic rollers, the more aggressive the lobe, the quicker you lose control of the valvetrain.  The quicker lobes are also noisier.  Without running unrealistic amounts of spring pressure, it’s more efficient and beneficial to use a less aggressive lobe.  Running a lazier lobe increases the advertised duration which increases overlap, which necessitates a LSA change.

Clevelands are a whole different animal and are similar to Tunnel Port FEs where you have a humongous intake port and need more overlap to scavenge it.  Cleveland cams are a little more trickier to spec.

Without asking a specific question about a specific combination, you’re likely just gonna get generalized answers. 

[70tp]

In regard to the tunnel port and Cleveland needing more overlap to help scavenge , what is usable in this situation assuming maybe a 6500 power peak?  (106-108cl?).  A lot of “it depends” is in this, I’m sure.  Crane used to always recommend a 114 center on any that I inquired on.   And how narrow can the lobe centers get to where an engine tends to get like a two stroke dirt bike with a abrupt point to where the power hit comes on?  Do breathing limited engines , such as a factory headed small block benefit from narrow lobe centers also?   

[blykins]

In regard to the tunnel port and Cleveland needing more overlap to help scavenge , what is usable in this situation assuming maybe a 6500 power peak?  (106-108cl?).  A lot of “it depends” is in this, I’m sure.  Crane used to always recommend a 114 center on any that I inquired on.   And how narrow can the lobe centers get to where an engine tends to get like a two stroke dirt bike with a abrupt point to where the power hit comes on?  Do breathing limited engines , such as a factory headed small block benefit from narrow lobe centers also?

Yep, it depends on a lot of things.  On the Cleveland and TP, the main variables are the displacement and if the factory intake volumes have been reduced.  Again, vacuum requirements also play a huge role.  If you have power brakes, then the overall picture has to be eyeballed and some concessions may need to be made.  On stock displacement engines with no vacuum worries I have used 104-108 LSA cams quite a bit.

I really can’t stress enough that I’m being extremely vague in my answers because there are so many variables.

Stock style heads, again, can use all sorts of cams.  The cam for my 352 is on a 104.

[CaptCobrajet]

I've been reading this thread along.  Apparently I must be a little slow on camshaft design.  I have never seen a 6000-ish rpm engine (hydraulic roller) that benefits from wide separation and lazy cam lobes.  Individual runners excluded, lazy lobes and wide centers will get you a lazy engine from what I have seen. Beehive and conical springs pretty much eliminate valvetrain weight issues in engines up to 6000 rpm.  The reduction in spring and retainer weight is almost like having a valve that weighs nothing with conventional springs.  Moving mass weight is reduced by more than the weight of the valve.  I go 112 on occasion for power brakes, but big heavy cars and trucks with big tires ain't gonna like anything wider than a 110 in a streetable FE.  I'd say you lose 20 average hp for every 2° past a 108 if .050 duration is 250s or less.  Sometimes I put a 112 on a big street engine to kill some bottom end on purpose, to help with wheel spin.  A by-product is that they will hang on a little longer past peak power also.  Going 108 for the John Force cruise-in rumpity rump deal will beat the ground, and sometimes will be faster, but I discourage that idea because most get tired of the rough idle and the bumping up against a straight shift in the lower gears.

I think spreading the lobes to decrease overlap is the wrong way to go on mild to mid-level street or towing apps.  I think you can make more steam in a usable range by staying tighter and taking duration away, with a head that moves a lot of air at low lifts.  The better head being the key, in my opinion, and also it is VERY important to decide on an operating range, and then choose duration to work there with all things considered.  High revving, big duration, with high flow can benefit from wider separation......much wider than what will work on the street, but every time I have seen that work, there is "excess" flow and big inches involved.  It is hard to go wrong  with a 110 separation in most cases where duration is 220 to 240 @ .050, when brake vacuum is not a consideration.  Everybody has opinions.......and I could fill a phone book with opinions......the ones expressed here about this particular topic are pretty general.  There are always factors that change the requirements.  My comments on this are with a pump gas, fairly well mannered street car or towing/4x4 piece in mind.

[frnkeore]

In regard to the tunnel port and Cleveland needing more overlap to help scavenge , what is usable in this situation assuming maybe a 6500 power peak?  (106-108cl?).  A lot of “it depends” is in this, I’m sure.  Crane used to always recommend a 114 center on any that I inquired on.   And how narrow can the lobe centers get to where an engine tends to get like a two stroke dirt bike with a abrupt point to where the power hit comes on?  Do breathing limited engines , such as a factory headed small block benefit from narrow lobe centers also?

In your case, I'd try a 108 lsa, with 234 deg @ .050. Installed 106 intake but, try 108 or split over lap (straight up) too. I'd also try 104 or, 4 deg advanced, if you have the time and resources. That said, if your still close to 350 CI. If your in the 400 CI range, you might be better served with 236 @ .050 and you can tune with more exhaust duration on the C.

Porting and intake/headers, can be used to tune engine size and streetability also.

[blykins]

Blair, a 112 LSA is wide in comparison to some shelf cams, and a 56 degree hydraulic intensity IS lazy.    An aggressive lobe is similar to some of the Xtreme Energy lobes or Voodoo lobes, with 50-52-53 degrees hydraulic intensity.  Those cams are flat out noisy and require much different valve spring pressures.

Again, LSA is relative and overlap is application specific.  I’ve done lots of towing cams on 106-108-109 because that’s what they need.