Shouldn't there be common knowledge about what adjustments to cam profile are normally needed when going from a shorter stroke motor to a longer stroke? If so, I'd use those guidelines to alter a profile of a well performing cam you see for normal 2 litre setups. Or maybe there is a cam already out there that fits into your spec.

Also, a lot of people are mentioning "280" and "272" which is not very descriptive of a cam. What is more important is the effective duration and lift to get an idea of how the cam works.

 

Any thoughts on the FP5 cams. I was thinking of trying those based on comments from guys who run them locally.

Paul

 

The only Cams I would ever run on a 2.3 or a 2.4L would be a high duration and high lift cam!

The two cams that I favor are the GSC S3s and the FP5Rs. I would not do anything smaller. You need the extra air flow for the larger motor. A 2.4 flows 20% more air than a 2.0 so you should be using a 20% larger cam at a minimum.

S3s:
280/238@50 11.7mm lift

FP5Rs:
I - 275/229@50 12mm lift
E - 285/238@50 11.9mm lift

I have still not decided which cam will be going into my LR2.4 that is getting built as we speak but I will be deciding very soon. However, it will only be one of the two I list. Nothing else will go in my motor!

Mikey

 

FWIW, a high lift cam with factory head won't do much aside from place additional stresses on the valvetrain, because flow data shows the factory ports to be unresponsive above ~10.5mm lift. It's good to file this bit of info in the back of one's mind.

If we lengthen the stroke and reduce the R/S ratio (e.g. 2.3 4G63), this causes the piston to create a stronger 'sucking' action at lower engine speeds and the piston moves slower around BDC. These two phenomena tend to mitigate the negative impact of a longer effective duration camshaft on low and midrange rpm performance. Now, this isn't saying one should start looking at the longest duration camshafts available, but longer duration, moderate lift profiles (e.g. JUN 272, BF272, Kelford 280) become more viable street selections, and the impact on spool and such is less than it is with a 2.0.

Also, note that some '272' cams feature longer effective duration than others' 280 cams, so referring to cams as "272s", "280s" is useless.

FYI

 

Ted speaking of that, what are the considerations when deciding on a the ramp rate of a cam? As in your example, a 272 with greater effective duration than a 280 will obviously have a steeper ramp.

 

In choosing these larger duration cams (BF272, JUN 272, Kelford 280) one would expect more idle and drivability issues on the 2.0 but would these characteristics lessen with the 2.3 and 2.4 motors? My goal is to have the optimal cam for my 2.4 but stalling issues and poor idling is what I dont want especially since ill be using the stock ECU and have the car as a DD. Anyone has any info on the JUN 272s on a stroker?.

 

just a quick comparison. Couldnt find an Evo 2.0 runing the Brian Crower 280's but here is a GSX 2.0 (280°/280° 218°/216° .422"/.418" 10.71/10.60 )
http://www.youtube.com/watch?v=kpbA_q6qNQo

and a 2.3 stroker Evo runing the Brian Crower 280's (280°/280° 218°/216° .425"/.408" 10.80/10.36)
http://www.youtube.com/watch?v=cTxZbLxP-Ds

 

The considerations are the quicker ramp rates typically translate into improved spool characteristics and greater flow potential, but the demands on the valvetrain (especially springs) are increased.


Yes, for the reasons of 15-20% increased displacement and reduced R/S ratio. As for the degree of difference, it's hard to quantify that from this vantage point.

 

Ted, I'm building a LR2.4 156mm rod w/ 10:1 pistons. I currently have a Red and will be going to a Black shortly. What do you think would be the best cams for my setup. The head is ported as well. Thanks

Mikey

 

There are several cams that would work well. I might be tempted to try the Kelford 280 set, but that's just me.

 

So ideally - with a stock head on a stroker. Your looking for more duration - rather then more lift..?

 

To clarify what i was saying...you should increase the duration on a well performing cam (Kelford 272) while maintainging a similar acceleration profile.

I wasn't implying that the profile should be the same @ .050" .100" etc. and JUST extend the duration from seat to seat.

 

Where peak power potential is concerned, to distill all the reasoning down to one word, yes.

 

No one tried the Jun 272s? Any input?

 

Thats what was just suggested to me.