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Discussion Starter #1 (Edited)
Hi guys, from Downunder,
as per my previous post i have a 65 FB with a 302, WR Toploader and 3.00:1 9 inch. The motor was rebuilt in 2004 bored 30 thou with an Edelbrock 600 and Cobra style intake manifold and Hooker longtube headers.The engine builder only remembers that the cam had about 0.450 lift!
Compcams recommends the XE256H cam:
A local engine builder acquaintance recommends a single pattern cam as the dual pattern can affect the CR.- Compcam 270H or the 268H .I am a little worried about the 270H as the lift maybe on limit for standard heads.
Googling gives mixed results as to what people prefer.:shrug: There seems to be a small preference to the newer dual pattern cam.
Does anyone have experience with these in a similar specification as mine?

thanks in advance

Roberto
 

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I agree with Comp Cams here. On stock sbf iron heads I always recommend a dual pattern cam. The reason being is the anemic flow of the exhaust port on these iron heads. The added duration on the exhaust side from having the dual pattern aids this. Almost all modern camshafts you see today are dual pattern. Very rarely will you see a single pattern camshaft today and even less frequently will you see a single pattern cam used on a sbf.

Now, to the point that a dual pattern cam will affect the CR. The static compression ratio is what it is. It is a fixed number once you assemble everything. What can change is the cylinder pressure which is affected by the camshaft valve timing events. In general, the bigger a camshaft is (duration) it will bleed off more cylinder pressure due to the valve timing events (overlap). This is why you need to build and engine with more static compression when you plan on running a larger camshaft; to keep cylinder pressures up. Out of those three camshafts the XE256h will make the most cylinder pressure due to its valve timing events. On a 289 or 302 this is usually not a problem due to the fact that it is harder to get the compression ratios up on these engines without using a dome piston or small combustion chambers. It would be useful to know what your static compression ratio is.

If you do have stock 302 heads with pressed in rocker studs I would not recommend the Comp Cams Magnum 270h camshaft. With a lift of .500", the lift is too great and you will most likely end up with rocker studs pushing out of the head. The rule I usually see is somewhere in the range of .480ish" is about the limit of the pressed in studs. The XE256h is bordering on the edge of that. I would say that if you used the proper valve springs for the cam you should be able to run that camshaft with pressed in studs.

IMO, the xtreme energy line of cams is the way to go. They are a modern lobe profile and they make good power for the relative size of the camshaft. The high energy cams are a "ho-hum" line of cams with older, less agressive lobe profiles. The Magnum line of cams can be used successfully given the proper combination but I see no reason to run a cam that large on your setup.
 

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Discussion Starter #3
Thanks Ryan,
for the very informative thread.
You have cleared it up for me.

Roberto
 

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I agree with Comp Cams here. On stock sbf iron heads I always recommend a dual pattern cam. The reason being is the anemic flow of the exhaust port on these iron heads.
There's a very simple cure for this, and it's a fairly easy one-day project, that'll cost only a "valve job" gasket set. Then you don't have to compromise on your cam design. On Ford performance cams, Ford didn't compromise. The smallblock C3OZ-6250-C 289HP cam, the similar hydraulic C9OZ-6250-C, the Cobra LeMans C7FE-6250-A,
were matched profile cams.

Do this, and matched profile cams can be used, and even dual pattern cams can be used to full advantage:

289/302 Cylinder Head Port Matching
 

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Greetings,

Excellent answer, 22GT. Most(99%?) aftermarket cam profiles are designed for the, dare I say it here, small block Chevy, and then simply ground on the Ford cam shaft blanks. Ford didn't do that. Granted, they didn't manufacture their own camshafts, but the engineering was done specifically for their own products.

Another good profile to try on an otherwise stock 289 or 302 is the one used in early 351W. This was later used for marine applications and re-surfaced in the 1982 5.0 Litre GT engine. It nicely addresses the lower flow numbers of the exhaust port. I've been using it in the little engines since the late 70's you can't tell it from a stocker until you give it some "Wellie", then away she goes, almost as good as the C9OZ-C. Much better fuel economy than the C9OZ-C, though. When Ford replaced the Marine/351W camshaft for 1985 in the manual trans models they reverted to a single pattern cam again. Not sure why, because the dual pattern model had worked so well for them.

Don
 
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