I'm getting mixed opinion's on cam LSA... Im running a 383 w/ ported LT1 heads, pretty much every bolt on possible etc. Im planning on spraying about a 300 shot on it maybe 400 some day but for now 300 will do im wondering what LSA would be best... My current cam im running right now is a 236-242 dur|.556-.576 lift w/1.6|113 LSA im not really sure that I like the 113 LSA and am thinking about going lower... Like 110... I talked to one of the top dogs that are running in the 9's in an LT1 and he's running a big shot as well on a 110 LSA so what do you guy's think?

 

The 110 LSA and going 9's on a big N2O shot doesn't tell us much really. With N2O you are looking at overlap area and placement of the timing events with advance.

Don't run a LSA because someone else who's fast runs it. Doesn't work like that. The overlap are could vary GREATLY from a 230 duration cam to a 280 duration cam.

Bret

 

That's true.... Well what should I do then? Would 110 be good or a bad idea then?

 

Is that 236/242 cam an XE grind? If so you would see a gain in HP with a 110 LSA with that cam, since that cam doesn't rev past 62-6300rpm anyways even with a 112lsa, a 110lsa will acctually let that cam prolly climb to about 6600rpm which is a good idea IMO, I wouldn't rev it past that since it is an XE grind cam (if it is). The 110lsa wouldn't be too bad considering there is only a 6* split between the intake/exhaust, see on a cc306 per say, you don't want a 110 lsa because that cam already revs to the moon & one of the reasons is because its got such a huge split between the intake & exahaust "14* split* That is already got a lot of overlap between the intake & exhaust, as the exhaust is closing, its far from being closed by the time the intake opens as compared to a cam with a 6* split, thats why you can get away with a tighter LSA on a cam with a shorter split

I'm trying to explain it so you can understand here

Plus to add to the differences in cams, you also have the lobe profile to think about, the 236/242 XE is essentially comparable to a 226/232 cam or so when it's duration when opening ".006 lift", so there is some loss in REV's per say.

 

Thanks man,

yes it is an XE cam. im not sure on the RPM range on my cam but yes I don't wanna rev past 7K and don't really care what I rev too before that as long as im making some power

 

You'll make some good power for 6k rpm don't worry

 

Don't know if I agree with all of that.

The amount of split, the advance and the LSA are all determining factors and just putting a generic 110LSA vs 112LSA on there is not really fitting.

XE lobes are more aggressive, true. They can be made to go pretty high RPM without a worry, it's the rest of the valvetrain that's the problem.

The split is part of the overlap and is part of where the overlap triangle occurs around TDC. Linking LSA to the amount of split is not really the best way to go about it. The more split means the more duration on the exhaust and usually more overlap, but 8degs of extra exhaust duration only adds half of that to the overlap. A 4 deg change in LSA makes a direct impact on overlap. Since it's double the number 4 = 8 so in turn the LSA is a much more important function.

Big splits and tight LSA's is not a problem.


All depends on spring pressures and the rest of the valvetrain.

Again. 110LSA is one thing but a 108LSA is really not out of the question too. It all depends on what you want the car to do.

How about we look at it that way first.

What do you have?
What do you want it to do?

I'm not going to go into details, because I get paid to go into details. But a generic you want 110LSA if you want this is not the best way to go.

More overlap that is given to you by the tighter LSA will help in HP production and the earilier ICL will add to DCR which gives you TQ.

That's where this discussion should be heading. Understanding that statement.

Bret