Author Topic: Stiffer SOHC camshafts?  (Read 3026 times)

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machoneman

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Stiffer SOHC camshafts?
« on: April 12, 2013, 08:56:00 AM »
http://www.enginebuildermag.com/Item/89943/pro_stock_engine_technology.aspx?MostRead=1

This topic has been around for awhile (larger diameter cores) but I wonder if the high spring pressure, high lift/duration SOHC's you run Jay might benefit from a stiffer core? IIRC, the top builders check the amount of twist from the front lobes to the rears with new cams and then after they have been run for awhile.  Could Bill Conley's machine handle a spinning camshaft in a fixtured head to see if twist  is an issue or not?   
Bob Maag

jayb

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Re: Stiffer SOHC camshafts?
« Reply #1 on: April 12, 2013, 10:48:06 AM »
That is a great article, thanks for posting.  I'm not sure if twist is an issue for the SOHC or not.  One thing that argues for the latter is that each cam is only running 8 valves, not all 16 like a normal V8 would be.  Also, compared to the spring pressures they're running in Pro Stock, even the pressures I'm running on Comp's biggest cam and the heavy Manley valve are way down the scale (600 open vs. 1000 open for the Pro stock engines).  Nevertheless, I'm sure there's still some gains to be made with a stiffer core.

I don't know if Bill's machine can look at relative valve motion or not, but I think he is probably restricted to one cylinder at a time for measurements.  Maybe he will chime in here...
Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC

   

WConley

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Re: Stiffer SOHC camshafts?
« Reply #2 on: April 14, 2013, 11:43:45 AM »
Interesting topic!  Actually I can run more than one cylinder (though doing all four with stiff springs would be a big stretch).  The two end cylinders set up with targets on the cam lobes would give us an idea of torsional stiffness.

Funny this topic popped up.  I have just pulled the machine out of mothballs and am getting it all set up.  I'll be taking it to Robert Pond's next weekend for a thrash of his SOHC cylinder head.

Once I'm done with that, I'd like to think about this torsional issue.  You have piqued my curiosity :-) 

- Bill
A careful study of failure will yield the ingredients for success.

jayb

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Re: Stiffer SOHC camshafts?
« Reply #3 on: April 14, 2013, 01:32:18 PM »
Bill, I think it is fortuitous that you have dug the machine out of mothballs.  When you get done at Robert's, if you have time I'd like to send that test SOHC head back, with a new cam profile I'm trying out.  It is a custom grind, similar to the biggest Comp lobe, but with a little more duration and lift.  You'd be welcome to use that head/cam to look at the torsional stiffness, and it would probably be worst case because for this cam the base circle of the lobe has to be reduced somewhat for the added lift.  What do you think?
Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC

   

WConley

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Re: Stiffer SOHC camshafts?
« Reply #4 on: April 14, 2013, 07:51:32 PM »
Sounds like a good plan.  I'll definitely want to talk to you about the best way to instrument for measuring torsional vibration.  It seems a setup similar to what you used for your chain stretch measurement would be good.

- Bill
A careful study of failure will yield the ingredients for success.