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BBF valve to valve clearance

 
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PACE429
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Joined: 01 Oct 2006
Posts: 5
Location: Havre de Grace, Maryland
322.92 points


1973 Ford Mustang

PostPosted: Sun Dec 21, 2008 4:38 am    Post subject: BBF valve to valve clearance Reply with quote

Hey Guys, I am just putting the finishing touches on my 545 stroker motor. I'm hoping to install the engine in my '73 Mach-1 sometime this winter.

I very recently found a notation on a Ford Racing cam spec sheet for solid roller cam PN M-6250-A514 that advised the cam had enough lift to cause valve to valve iterferance if used with the M-6049-B429 CJ heads. They recommend reducing the intake valve and seat sizes from 2.250" down to 2.200".

Has anyone ever had a problem with this and what can be done short of down sizing the intake valve dia.?

The listed cam spec's: Intake .647" lift 254 dur. @ .050 -107 CL ---- exhaust .647" lift 258 dur. @ .050 -117 CL Any suggestions? I'll contact Ford Tech hotline this week for their input. Thanks , Mike
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clay
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Joined: 24 Nov 2002
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Location: South Carolina
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1972 Chevrolet Nova

PostPosted: Sun Dec 21, 2008 9:43 am    Post subject: Reply with quote

I haven't worked with many canted valve heads, I can see where it could be a problem and I can't see a solution other that making more clearance with a reduced valve size. I don't think juggling installed intake certerline will make a difference and that's about all you could play with, everything else is ground in and not adjustable. Clay
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Big Dave
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PostPosted: Sun Dec 21, 2008 10:22 am    Post subject: Reply with quote

With a BBC (that other canted valve head) you have to physically move the valve in the head to spread the centerlines for clearance.

That usually involves buying a raw casting and cutting your own seats and pressing in your own guides. If the heads are aluminum they can be welded up and moved after the fact, but a raw casting is the cheaper route to take.

Big Dave
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Knarley Darley
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Joined: 22 Apr 2004
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PostPosted: Sun Dec 21, 2008 5:18 pm    Post subject: Reply with quote

I have delt with this before with bb chevys. In my case I was able to see the valves touching through the spark plug hole with a flash light. My cams are much larger though. The other way to check is with no piston and mock up the head and rockers and look up through the bottom of the cylinder. In my case I had 2.375 intakes and luckily the valve job had been done at 2.300 so we jist cut them down, however this makes the edge of the valve to thick so we put them in a lathe and cut the combustion chamber side of the valve thinner which didnt change the hight of the stem in relation to the spring installed hight. Do not cut the seat side of the valve to get your margin back or it will be sitting higher in relation to the spring and your rocker geometry will be off and pushrods will be too long. Also sinking the valve into the port is like giving away free lift.
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PACE429
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Joined: 01 Oct 2006
Posts: 5
Location: Havre de Grace, Maryland
322.92 points


1973 Ford Mustang

PostPosted: Wed Dec 24, 2008 1:22 am    Post subject: Reply with quote

Big Dave wrote:
With a BBC (that other canted valve head) you have to physically move the valve in the head to spread the centerlines for clearance.

That usually involves buying a raw casting and cutting your own seats and pressing in your own guides. If the heads are aluminum they can be welded up and moved after the fact, but a raw casting is the cheaper route to take.

Big Dave
Dave, I think that the new P-51 head design by John Kaase for Ford Racing has relocated the valves to not only correct this condition with high lift cams, but he also greatly improved the flow and HP spec's. I'm not trying to set any speed records with this motor, however I want it to survive my drive style!
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PACE429
Newbie


Joined: 01 Oct 2006
Posts: 5
Location: Havre de Grace, Maryland
322.92 points


1973 Ford Mustang

PostPosted: Wed Dec 24, 2008 1:26 am    Post subject: Reply with quote

Knarley Darley wrote:
I have delt with this before with bb chevys. In my case I was able to see the valves touching through the spark plug hole with a flash light. My cams are much larger though. The other way to check is with no piston and mock up the head and rockers and look up through the bottom of the cylinder. In my case I had 2.375 intakes and luckily the valve job had been done at 2.300 so we jist cut them down, however this makes the edge of the valve to thick so we put them in a lathe and cut the combustion chamber side of the valve thinner which didnt change the hight of the stem in relation to the spring installed hight. Do not cut the seat side of the valve to get your margin back or it will be sitting higher in relation to the spring and your rocker geometry will be off and pushrods will be too long. Also sinking the valve into the port is like giving away free lift.
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Big Dave
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Joined: 04 Dec 2005
Posts: 2644
Location: Tampa Florida
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PostPosted: Wed Dec 24, 2008 10:55 am    Post subject: Reply with quote

PACE429 wrote:
Big Dave wrote:
With a BBC (that other canted valve head) you have to physically move the valve in the head to spread the centerlines for clearance.

That usually involves buying a raw casting and cutting your own seats and pressing in your own guides. If the heads are aluminum they can be welded up and moved after the fact, but a raw casting is the cheaper route to take.

Big Dave
Dave, I think that the new P-51 head design by John Kaase for Ford Racing has relocated the valves to not only correct this condition with high lift cams, but he also greatly improved the flow and HP spec's. I'm not trying to set any speed records with this motor, however I want it to survive my drive style!


The manufacture will specify the largest valve possible for your head (moving the guides to accommodate valve diameter has to also to fit with in the block bore at maximum cam lift). The bigger the bore of your block the bigger the valves can be and the further the guides can be separated (for example Dart Big Chief 18 heads will fit a 4.375" bore, but a 14 head requires a 4.500" bore and the 11 head has to have a 4.600" minimum bore to accommodate the valve offset.
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