cam selection / use questions

[Invectivus]

while over-simplistic, its said the cam is the heart of the engine, and it certainly does dictate (along with engine volume) what lifter/porting/exhaust/carburation mods you make to support it. I'm prepping again to build my first engine, and I want to verify my needs as it were. It's my 67 mustang, 4cyl t5, and I love coming off the light hard (that's what makes getting groceries fun), so I'm assuming I want a low range cam in the 110* range as I don't know how much I'd like a real choppy idle of a 108* (has anyone used one?) but I'm not sure how low my rpm range should be really. It's hard to gauge off a 'if you like this kind of driving get this' scale.

One of the things in the CI tech section shows for highway driving and passing, the 112* is a better choice. Will a t5's increased gearing variables mitigate a lower duration cam? Or will the lower first gear (depending on rear/tire combo) make up for a lack of lower range torque in my 112* cam? I know a classic pony isn't made for high speed driving, but sometimes you need a little bit. I currently have:
264/274-112* Hydraulic Dual Pattern Cam (http://classicinlines.com/proddetail.as ... 264-HDP-12)
which looks like a good toodling around cam, but it's hard to guess how much of a loss of fun at a light there really is. It will have a ds2, so that should help the oomph at all ranges.

so I guess getting around to what I'm asking isn't so much a 'what cam' thing, but rather what range given my drive train accoutrements and predilections. Increasing carb and cleaning up flashing isn't an issue, but I don't think porting (above bubba pocket porting maybe) is in the cards.

I'm also assuming that the 112* would like the 302 springs and one piece retainers, but a low range built not as much? Not that it would be detrimental, just not as valuable with less rpms and less valve float? Don't want to waste resources that are at least trouble to find.

 

[wsa111]

What are you planning to use for carburation?? Compression??
If you don't do a direct mount carb on the intake that cam is not recommended. Need more info.
Great idea to put all the cards on the table before you do the build.
Then the distributor needs to have the correct curve as a final selection of the above.

 

[80broncoman]

So tell us what do you want differently out of the engine with it having the
264/274 cam in it?

 

[Invectivus]

sorry, I am planning on a direct 2bbl modification(at least a progressive, maybe an autolite). I'm virtually always less than 1000ft elevation, 90* or lower without extremes of humidity. I plan on running pump gas, while increasing compression to the low 9's, so I'll need to be wary of my static and dynamic compression ratios (the math of which has been eluding me).

Both block and head milling are on the table. The block is a C6 200 60 over, a C9 larger flat top head, and if they fit, cast rods. As my first engine build, I'm using throw away parts and such in case I screw something up. I still need to measure my piston dish and current deck height on my builder block.

one of the 'cam selection' aspects is CR and misfire prevention, and while there are plenty of programs that take your SCR Specs and cam specs and show you your DCR, I never found one that walked back from desired DCR through cam to get an SCR target to machine for. The rule of thumb as I understand it is 9.2 CR needs 92 octane pump gas, 8.7 needs 87 octane, etc, but I can't tell if that's static or dynamic, and dynamic is always lower and RPMs change cylinder pressures differently depending on intake and exhaust characteristics. Which is why I lost my way a year ago, planning gives me a headache. Part of me gets frustrated and figures in shooting for 9.2 SCR, leaving power on the table and seeing how things work. It's just a lot of money to spend not to try and do it right.

the cam I have specs out as a 'mid to high range street cam for a 2V converted head' which sounds reasonable, but the tech section shows a 112* sacrificing low end torque for high end performance and passing power, while the 108* gets lots of low end grunt without the higher rpm performance. I recognize this is the playing field without variable valve lift and timing. However, the simplified description of the cam performance profile doesn't really give a drive train standard. That's why I asked (poorly) in a t5 car, would the low first gear make up for my 112* cam and give me similar off the light fun as a 108* 3 speed stick, or would the OD and more granular upper gears make up for me getting a 108* cam without optimal high end characteristics?

if anyone can advise me to a resource for planning, I'd get it. My small block performance book is a little light on the planning and engineering concepts.

 

[JackFish]

I think having the standard transmission will really help make your setup versatile.
I run the 264/274/112 and yes it has lots of passing power and not to peppy on the bottom end.
It really comes on above 3000rpm.
Advancing the cam is recommended to bring the rpm range down a bit.
But if I had a standard tranny I would probably look at the 110 or 108 lobe centers.

 

[ray6966]

any recent news on your project? did you install the 264/274-112* Hydraulic Dual Pattern Cam in the car?