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Personaly I'm all for a dual pattern cam especially in a small block Ford. You can get more exhaust lift than intake lift and it helps to prevent reversion. I think if you want more of a rumble sound and a bit more top end then the 110 would be better, but the 112 for me anyway seems to be more streetable. It seems that every time that I would use a streght up cam that it would run better with a stick and the dual pattern was better with an automatic, I've been wrong before though, But this is from my experience since 1971.......Bob
 

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Discussion Starter #3
Thanks Bob. You could be right about the auto vs stick. I notice almost all 5.0 roller cams have 112 Ls. I dont know if thats because of EFI or what.
 

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Almost all 5.0 roller cams have 112 seperation angle because that makes those small 225 dur at .050" lift cams emissions leagal and another benefit is the blowers like those the wide seperation but the reason the cams are 112-114 are for emissions reason. 50 state legal cams. If somebody chooses a cam that small, that means they will driving it on the street so they put the 112-114 LSAs for that reason. I have personally had very good results with single pattern cams with my automatics.
 

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All this talk about LSA'a has got me curious. I've never thought about it before, but in a street driven car, would a shorter LSA get poorer MPG than a cam with similar lift and duration but an LSA that is much larger? Say a 108* cam vs. a 112* cam?
 

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Discussion Starter #6
I would think a 112Ls would due that it has a little more vacuum at low rpms.
 

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Here's my 25 cents. Single pattern camshafts usually produce more low and mid range power due to NOT having extra exhaust duration that intrudes into the power stroke.
This leaves the cylinder pressures higher, for a slighlty longer period of time and makes better torque & HP for real daily driver street cars. The lobe seperation is a valuable tuning tool if used correctly. Reducing this angle cuts valve overlap and does reduce reversion and hence the bad idle characteristics. However, reducing duration will have the similar effect. Most enthuiasts overcam everything, so the manufacturers purposely make off the shelf cams with wider seperations, not so much for emissions, but for great flexability. Even a poor choice cam will work somewhat. Widening the LSA will produce more top end power and a broader power curve. This broader power curve and better idle is just a safe guard. (I have conversed at length with the engineers at Comp Cams, Isky Cams, Crane Cams etc. for about 15 years now. We use alot of custom grinds) Likewise, tightening the seperation angle will open the intake valve earlier in the intake stroke and allow better cylinder filling. It also closes the intake valve early in the compression cycle and results in more low end power. There are also lots of other cam charateristcs than duration and LSA that greatly effect the engines output. How fast does the valve actually open? Remember the valve is the biggest restriction in the air stream, so the sooner you can get it open in relation to TDC, the more cylinder filling you'll get and hence more HP.. This is why higher ration roller rockers works well. It's not the tad bit of extra lift that makes the power. (if it is, then you didn't do your homework to find out what lift your heads really require to begin with!) Why add more lift than you need? This only requires higher valve sping pressures and you loose power to parasidic loses.. Guessing has no place in performance engine building. SOme guys believe that guessing and speculation are common engine building tools. NOT! You either no the facts, or never finish first. But don't take my word for any of it. Call the cam manufacturers and ask them for yourself.. ON the topic of Motorsport cams.
They are antiquated profiles! Yes they will help make HP, but there are MUCH better eductated choices to make. The CC's extreme energy profile (#324-8)is a better choice. The Motorsport cams put the extra intake duration on the closing side anyway, so even with the CC's being only 270 duration, it will give the same opening advantage but with much higher valve acceleration. And the extra 6 degrees on the exhaust duration won't overlap into the power stroke enought to hurt low speed performance. Optimal lobe seperations for a 300 inch engine seems to be 110. We find reducing the LSA by 2 degrees every 50 cubic inches works really well. 110 for a 302, 108 for a 351W, 106 for say a 408 windsor stroker. This is assuming a similar head, like the Trick Flows are used on all of them. As the head gest better, you can reduce the LSA and still match the top end HP, but also make better low and mid torque. Once you get your 289 build, have it dynoed.. You'll find that the desk top dyno program isn't even close! I'd love to see a 289 make almost 390 ft lbs! That would be a good figure for a 351W.. Using the MEP formula (mean effective pressures) is a much closer way to predict HP. If the 289 is in a non emission application, I would build it to rev like a mother and let RPM make the power! Remember that an engine is just a thermodynaic air pump. The more air and fuel you move through it, the more power it will make. That's why a normally apsirated 300 inch engine can make the same hp that a 400" can.
You just have to rev the 300" engine 33% higher to match the pumping characteristics of sais 400 incher.. Good luck..
 

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Discussion Starter #8
Thanks Adamsperf.
Ok, Comp cams recommended 218-224 110Ls. Crane cams recommended 224-232 112Ls. I like the higher reving of the Crane but am I getting to the point of low vacuum and rough idle? My car is a street driver but weekend racer.Currently I have 10in vac in park @ 1000rpm and 5.5 in vac in drive @ 750rpm. with the non roller cam I have now {Lunati 228-235 110Ls and 9.3 comp. Crane fast bleed lifters} ratio. I have to run a vac can for the power brakes and have a hard time jetting at idle and light throttle with a on board o2 annalizer. The part throttle will not clean up because of the low vacuum signal at idle in gear I have to jet richer and when the engine speed picks up so does the vacuum and fuel flow to create a rich part throttle that smaller primarys won't fix.
So anyway, do you think the Crane larger cam is going to have similar problem?
{ C4 w/2700 stall }
 
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