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#1
02-04-2018, 02:31 PM
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Valve height and cam base circle measurements
What is the valve stem height measured from the cam housing rail to the tip of the valve and what is the stock cam base circle measurement
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When you really do something right it's like you didn't do anything at all 1931 Pontiac 5 window coupe OHC6 powered 2015 GMC Yukon SLT |
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#2
02-04-2018, 06:12 PM
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0.850" +/- .010 for the rail height is what I'm told. Unsure of the base circle. I could probably measure one out, as I have a few cams laying about right now.
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__________________________________________ "How I learned to stop worrying and love the OHC Pontiac L6"  The Silver Buick- '77 Skylark coupe w/455, SPX, MegaSquirt 3 & TKO-600 (Drag Week 2011, 2012 & 2015!) 1969 Firebird with a turbo'd Pontiac L6 controlled by a MegaSquirt 3 and backed with a microsquirt controlled 4L60e and 4.56 gears! (Drag Week 2018!) |
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#3
02-04-2018, 07:37 PM
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Okay, I went out and took some measurements. Turns out though the only cams I have at the house have been modified. My stock cams are in a storage unit.
Bearing journal: 2.2210" Core : 1.2200 (this varies, some places higher, some lower. Figured this one was middle'ish) Difference: 0.5005" on the radius, before the cam follower ratio. Now be mindful, none of the stock cams come even close to the bearing journal height. That gives a 0.750" lift if the lobes are welded up. The cam I was measuring had a base lobe circle of 1.5165" and peak of 1.8110" for a radius diffference of 0.2945" or lift at 1.5 ratio of 0.442" which is just a bit higher than stock (0.438") or maybe my measuring accuracy? I checked five lobes. Now be mindful, as the bottom side of the lobe is moved closer to the core either the cam housing has to be shaved or the lash adjuster shimmed up with longer valves (or modifed lash caps) to maintain valvetrain geometry. I measured it a long time ago, but there is also a point where the stock valve retainers contact the valvestem guides. I seem to recall this number being around 0.480", but am not sure. Bearing journal.  Core diameter. I measured it out between several lobes. Rotated the cam around and most had high points in the casting.  Base of this cam's lobe.  Lobe peak of this cam.  Hope this helps and let me know if you do anything with this information  I would like a much larger cam at some point.
__________________
__________________________________________ "How I learned to stop worrying and love the OHC Pontiac L6" The Silver Buick- '77 Skylark coupe w/455, SPX, MegaSquirt 3 & TKO-600 (Drag Week 2011, 2012 & 2015!) 1969 Firebird with a turbo'd Pontiac L6 controlled by a MegaSquirt 3 and backed with a microsquirt controlled 4L60e and 4.56 gears! (Drag Week 2018!) |
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#4
02-06-2018, 11:18 AM
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thanks for the information I thought that was the correct stem height but couldn't find it in my notes. I have a lot of used cams around but was curious what a new original would measure at. I will have to get in touch with jerry and have him resend me information
__________________
When you really do something right it's like you didn't do anything at all 1931 Pontiac 5 window coupe OHC6 powered 2015 GMC Yukon SLT |
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#5
02-07-2018, 05:01 PM
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I got one of Jerry cam blanks and was able to have primatechs stage 2 cam ground with stock base circle but I haven’t been able to verify it yet. I also have a new reground by crane h 320 that has a drastically reduced base
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When you really do something right it's like you didn't do anything at all 1931 Pontiac 5 window coupe OHC6 powered 2015 GMC Yukon SLT |
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