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cam choice 347 Windsor
Hi Fellow Engine Builder Technocrats,
Well the new Ford Motor Sport 347 short block has arrived. AFR CNC machined 185 heads are ordered with spring upgrade and roller rockers.:JEKYLHYDE :JEKYLHYDE Time to select the cam:rolleyes: :rolleyes: This motor has individual 44mm throttle bodies, 36 lb injectors controlled by M48 MoTeC. Compression will be about 10.5, pistons are fly cut to suit inline valves of the AFR heads. Running 5 speed, diff ratio 3.93, so engine will need to rev. The throttle bodies really smoothed out the old E303 cam. Looking for rough idle, good mid range torque and top end power. This cobra is driven hard on track days, very little road use these days. Was looking at a stage two cam, 224 / 232 at 50 thou, but think I could go a step bigger to make the most of the airflow from the throttle bodies and heads. Looking to make 420 + HP without excessive revs, below 6500 rpm. Anyone got a perfect cam for this combination?:confused: :confused: SNAKEN |
Hello Peter
As it happens I'm starting on my own 347 build, although mine will probably be a somewhat lower budget affair. Were I in your shoes I'd be tempted to look a the XFI CompCams for strokers - here is a link to the catalog: http://www.compcams.com/technical/Ca.../72-75_230.pdf Comp also are very nice about posting copies of articles by various magazines so you can read about other builds. viz... http://www.compcams.com/Community/Ar...?ID=1155060690 As you know - you almost never find articles about buildups using individual throttle bodies, however since that arrangement provides you with more (not less) flexibility in terms of range compared to the usual 4bbl you should be able to 'walk it in' to your desired outcome. This article has the approximate results and is one I'm using as a sort of template. http://www.compcams.com/Community/Ar...p?ID=846696448 I also have to say I like your thought processes - have blown an oil control ring - must build stroker :LOL: Good luck with the build LoBelly |
More info please
HI Snaken,
Are you running a roller cam with solid lifters? 420HP is that at the wheels?? Just love the stroked small block ford. Phil |
I would make the duration a little higher. A 224 duration isn't really much and I think it would make the peak too low for your desires.
In order to really do this job right, you need to compare the dynamic compression ratios of different cams that fit your needs. The static compression ratio really doesn't mean much. If you pick a cam with too much duration, your DCR will be low, and you'll actually lose power. Too little duration and your DCR will be higher than necessarily, which may compromise the use of pump gas. Email me offline and I'll go through some engine sims and recommend some cams for you and your needs. You want a roller cam, right? |
224 sounds pretty mild to me Peter.
224/228 is a popular mild cam for the LS1. I know it's an LS1 but the theory should be similar (an LS1 is 346 cubes). I decided to go for something with a bit more duration and lift. The cam going in mine measures 239/242, .649"/.609" on 111 degree lobe centers. I'm running 3.93 rear gears and the guys that supplied the cam think this combination should work well. It'll be a bit of an animal but should still be streetable. Those 8TB manifolds really smooth out a big cam as you don't have the disruption caused by the other inlets. Cheers |
Snaken
Have a talk to Chris McDonald at McDonald Brothers racing in Thomastown. He can be contacted on..................... 03 9 465 0000. He has a lot of experience with engine building and should be able to either make a suggestion or refer you to his contact at Crowe Cams who is a wizard at selecting the right cam - particularly if it is one of his cams..:3DSMILE: Chris built that 1000HP engine at the recent Summer Nats. The carby motor..%/ |
Thanks for the hints guys. Unfortunately work has got in the way this week.
Currently my preferred cam is a Lunati hydraulic roller advertised duration 290/300 .544 /.560 lift, 112 lobe sep angle. Having trouble comming to terms with the difference between advertised and @ 0.50 duration. Some cams have similar advertised and greatly different @0.50 Anyone know why? Confused Snaken |
The advertised duration is the duration that the valve is open from seat to seat (or around .005-.006" off of it). The duration at .050" is the duration from .050" off the seat back to .050" off the seat.
Some cams will be closer than others. The ones that have adv/.050" durations really far apart will show a lobe that will have quicker valve lift acceleration starting at .050". A lot of hydraulic roller cams will have a large advertised duration but a short duration at .050". |
The differences you are seeing between advertised and .050 durations between manufacturers, are the differences in the ramp profile (the steepness of the rise up the cam lobe). If the .050 and advertised numbers are closer together it will have a steep ramp, further apart will be a shallow ramp.
Generally, I would go for the steepest ramp for a given duration and lobe separation. This will generally give you the "best manners" (idle and drivability). One thing to note though: When using steep ramp profiles you must ensure the rest of your valvetrain is up to spec. Steep ramps can be particularly tough on valvesprings. Edit: Looks like blykins beat me to it, except that if the adv/.050 durations are really far apart they will have slower valve lift. In fact cams where the adv/.050 numbers are a long way apart can be real dogs down low and at idle, (not much fun to tune either). EG. 280/290 adv with 240/250 @ .050 has steeper ramps than a 290/300 adv with 240/250 @ .050 |
Plums, in the above scenario with the advertised/.050" durations far apart, wouldn't the valve be slow to get moving from seat to .050" (AND much slower overall across the whole seat to max lift range compared to a close duration cam), but as soon as you approach the .050" mark, it would take off, right? That's where I was referring to a quick acceleration.
I agree that it would be a slower lift overall, but I think once the valve approaches .050" lift, it would accelerate rapidly. |
The closer the numbers are together, the quicker the lobe lift acceleration. The lobe lift from zero to maximum will be more or less linear, otherwise the rest of the valvetrain would cop a hiding.
Hydraulic cams generally have slower ramp profiles (numbers further apart) than solid lifter cams. The hydraulic lifters themselves necessitate these slower ramp rates. |
Ok, thanks.
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Decision
OK I have decided
I am about to buy the following cam Lunati Voodoo hydraulic roller adv duration 290/300 @ 0.50 232 242 LSA 110 Sick of ***** footing around this is a serious cam to make for some serious fun. Should be able t bust lots of others parts with this lots of revs and hopefully HP in the mid 400's. Snaken |
Lots of low end torque
I have a 5.0 1996 block with a 354 stroker kit, 3.47" x 4.03" with 5.4 rods,
EFI, 90 mm mass air, 70mm TB, 36 lb injectors, 255 lph pump, tuned SCT chip, Holley systmax upper and lower plenum, 190cc Pro Comp aluminum heads 2.02 - 1.6, 10.7 - 1 cr. 1.7 roller rockers, 1 5/8" headers, Comp cam 35-518-8 fw XE274HR-12 gross valve lift int .555 ex .565 (with 1.7 .590 int, .600 ex) duration @ .006 tappet lift 274 in ex 282 valve timing @.006 open close int 29 BTDC 65 ABDC ex 77 BBDC 25 ATDC these specs are for cam installed @108 intake center line int ex duration @ .05 224 232 lobe lift .3480 .3540 lobe separation .112 Dwight I'm doing a little research on cams. I think I need larger throttle body and a different cam to move the power up, closer to 6000 rpms. But I must say this motor has "lots" of torque at 1500 rpms. Pulls like a freight train to 5500. I have to shift at 5500 - 5800 rpms. I had to change the way I drive. I can now cruise at 1300-1500 easily in 5th and I do not have to downshift to speed up. Very nice. I'm going to drive it till winter and then decide if I want to change the cam. df 323 rwhp and 375 rwtq http://www.clubcobra.com/photopost/d...m/DSCN0988.JPG |
Snaken..........When you were shopping around for a cam, what did the cam experts say was the maximum duration @.050 for 10.5 comp?
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My Cobra is 90% track used. Carbed 302, GT 40 X 305 heads. Recently I installed a Ford X 303 cam, lift .542, 286 286 duration. The power curve is now strong up to 6200 rpms in 4th gear.
The Ford 347 crate has the "Camzilla" Z cam with Z heads. I've driven a Cobra with one of these engines on the track. WOW! Roger |
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