What is the significance of lobe separation on cam timing? Stock speed density systems use a cam with 114 deg lobe seperation. Will a comparable cam with say a 110 deg lobe seperation perform better in a system which allows this such as mass air? Or will they perform much the same? I'm building a 351w to replace the 302 in my 88 F250 and need to understand a few things like this. Thanks, Tom

 

Any help Anyone?

 

First off, let me say welcome aboard!

Secondly, I'm no cam expert but if you are looking for performance upgrades, you need something with a bigger than stock lift. Changing to a cam with small separation without regards to the lift, will only increase the quickness as to the open/close timing, not a good thing for performance. Call the cam tech line for your manufacturer and talk it out. The Crane guys are very helpful and gan give a recommendation for your build. There is also a nice article somewhere that address this stuff, but I do not have it right now. Hold tight, the experts will chime in.

--Mike

 

With performance cams, the lower the compresson the more lobe spread you will want. A 12 to 1 comp ratio, could use as little as 108 deg. With a 8 to 1 you would want as much as 114 deg.

 

I wasn't aware of this relationship to compression ratio. I have a F250 with a 302. I have purchased a 351W roller block which I am building to replace the 302. I have converted to mass air so that my decisions don't need to be based on speed density. The cams that I am looking at are the comp cams <TABLE cellSpacing=0 cellPadding=2 border=0><TBODY><TR><TD vAlign=top align=left></TD><TD vAlign=top align=left colSpan=2>Ford 351W Xtreme Energy XE250H Cam</TD></TR></TBODY></TABLE>35-230-3 with a lobe seperation of 110 and effective rpm range of 600-4800, and the comp cams<TABLE cellSpacing=0 cellPadding=2 border=0><TBODY><TR><TD vAlign=top align=left></TD><TD vAlign=top align=left colSpan=2>Ford 351W Computer Controlled XE254H Cam</TD></TR></TBODY></TABLE>35-255-5with a lobe seperation of 114 (speed density computer compatable) and an effective rpm range of 1000-5200. The compression ratio will remain as close to stock as possible with the only real changes being the mass air and cam change. Thanks for your help. I really appreciate any and all suggestions. I have been reading this forum for awhile and am thoroughly impressed. I have done searches on cams, just haven't found enough information that I understand. Thanks. Tom

 

Any input on these cams? Tom

 

The 260H is a good place to start, gives more hp and tq than stock and is still pulls down low.
OH - 110-114 lobe sep.for the avg. "work truck"

 

ok...ive talked to comp for like an hour about this.. the 230 has a 50/50 chance of working even with MAF, if it did work it would sound sweet with that nice lope lope sound. but its still a gamble..hell if it works for u lemme know. but most of all they said if i wanted to run that cam id need a custom chip to make it run its best or at all if unlucky

 

Their website states: Very strong torque, excellent mileage,SMOOTH IDLE. How does that get to lopey? So this is basically a carborated cam? What would keep it from working with mass air? I was looking for that low end.Kind of sounds like very, very few of their cams would work even with mass air, which was the whole point of the conversion to mass air. From reading, I was under the impression that speed density was the restricting factor on cams.

 

therefore a 110 will idle rougher and scavange the cylinders better a high rpm whereas the 114 will increase dynamic compression and provide more bottom end torque.

 

Don't pay any attention to the lobe seperation. Would you believe some computer friendly camshafts have 109 lobe seperation? Your intake and heads play a role in which camshaft would work for you, there is more to it than the lobe seperation.

The 35-255-5 should work well in your application, there is a large number of people who've used that in SD engines and became instant promoters...

 

hey...im just goin on what they said cause i had had my heart set on that cam( 35-230). but the lobe sep is all thats wrong with it for efi..like i said tho u have a 50/50 chance for it to work with MAF. if u had a chip burned to run with 110' lobe sep u could get away with even SD.

 

i second going with the 35-255-5. many have used it with much happieness

 

I'm not saying your wrong, I was saying in general don't pay attention the lobe seperation, if comp says it will not work then there is a reason besides lobe seperation, they are taking into consideration things like cam events.

Call comp cams back, you might be suprised at what they say. I have called and been given a different recommendation each time, as a matter of fact all the cam companies have done this.

Its my understanding the XE is a better torque/performance camshaft than the high energy line.


Take a look at crane compucams.

 

Thankyou for all of your input. It always helps to hear some others opinions and outlook on projects. Seems odd that I wouldn't be able to run the 35-230-3 with mass air. I understand that it would be a very big problem with speed density which is the reason that I converted to mass air. I'll probably take the risk since this is the cam which seems likely to give me the low end that I want. Thanks again,Tom