Cam selection for the 300

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#16

04-04-2012, 12:02 AM

custom1106

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I noticed during some cruising through some cam posts about the isky spring specs being a little too heavy. Ill probably just go with the complete Comp kit and get everything done in one shot.

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#17

04-04-2012, 07:01 AM

BigBlue88

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I was reading up on this yesterday. The Isky 248 has really steep ramps on it to get the valves open asap. A longer cam can use gentler ramps to get the same full open duration, but you get a little more overlap. The stock cam actually has more seat duration than Isky, but I bet the ramp profiles are like comparing a wheelchair ramp to the cliffs of Normandy.

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#18

04-04-2012, 07:03 AM

BigBlue88

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http://fordsix.com/forum/viewtopic.php?f=2&t=66446

https://www.fordsix.com/forum/viewto...=65576&start=0

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#19

04-04-2012, 09:14 AM

custom1106

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Thanks for the links BigBlue...I've studied the first one previously, but the second one brings a lot of great info to the table. Much appreciated!

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#20

04-04-2012, 09:21 AM

BigBlue88

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Iirc, the stock head flows about 170cfm intake, 120cfm exhaust. On a 50ci cylinder, intake flow maxes out around 3500rpm. It will spin faster, but torque starts dropping.

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#21

04-04-2012, 09:40 AM

F-250 restorer

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Quote:

Originally Posted by BigBlue88

Iirc, the stock head flows about 170cfm intake, 120cfm exhaust. On a 50ci cylinder, intake flow maxes out around 3500rpm. It will spin faster, but torque starts dropping.

With a pro porting job, the flow characteristics of the 300 head can be improved quite a bit. I copied this from a write up:

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ontVertAlignInTxbx/> <w:Word11KerningPairs/> <w:CachedColBalance/> </w:Compatibility> <m:mathPr> <m:mathFont m:val="Cambria Math"/> <m:brkBin m:val="before"/> <m:brkBinSub m:val="--"/> <m:smallFrac m:val="off"/> <m:dispDef/> <m:lMargin m:val="0"/> <m:rMargin m:val="0"/> <m:defJc m:val="centerGroup"/> <m:wrapIndent m:val="1440"/> <m:intLim m:val="subSup"/> <m:naryLim m:val="undOvr"/> </m:mathPr></w:WordDocument> </xml><![endif]--><!--[if gte mso 10]> <style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority

9; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;} </style> <![endif]--> This brought the head flow up to 235 cfm from a base flow of 174 cfm on the intake the exhaust was 165 cfm.

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#22

04-04-2012, 09:50 AM

BigBlue88

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I read those threads too. Those flows get you to around 4500rpm, at the expense of low-rpm port velocity. Look at the power band and cruise rpm of the cams that will get you to 4500. What's the intended use case? How much effort are you willing to put in?

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#23

04-04-2012, 01:42 PM

custom1106

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Slow speed trail cruising and some light towing. Nothing really above 3000 rpm. Probably won't go any further than EFI manifolds and a 4 barrel in the future.

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