577" SOHC

[jayb]

A big tip of the hat to Bill Conley, for the following test results.  I sent Bill an SOHC cylinder head with one of my new cams installed, to see how it looked on his spintron machine.  Bill's machine, which he built by himself, can spin the cams up to high engine speeds and video the results in slow motion.  So, you can see exactly what the valvetrain is doing at high speeds, and determine if it is solid for performance use. 

The head I sent to Bill is set up with the same valves and springs as what I wanted to use on this engine, and I want to run it 7500 RPM.  So far Bill has found that the valvetrain is stable at 7000 RPM, but not at 8000.  He also has noticed the onset of smoke from the rocker adjuster tip to valve tip interface is sooner with this cam than it was with the previous set of cams (which Bill also tested).

http://youtu.be/Di4_aBUssnA

The smoke is not really a big concern for me because the amount of time that the engine will spend at these high speeds is very limited in a drag application.  But the valvetrain instability at 8000 RPM is a problem; my old cams were stable with this spring/valve setup at 8000 RPM.  So the reduced base circle of this cam definitely has hurt RPM performance.  I may need to look at increasing the spring rate or seat pressure to compensate...

[machoneman]

Bill's machine is a great thing to have! I would not have thought that a reduced base circle would limit rpm. Kudos to Bill for dynamic engine testing with admittedly a very low volume engine design now 48+ years old!

Hey Jay! Are you going to do a special 50th anniversary birthday party for the SOHC in 2015?

 
LOL!

[rcodecj]

A big tip of the hat to Bill Conley, for the following test results.  I sent Bill an SOHC cylinder head with one of my new cams installed, to see how it looked on his spintron machine.  Bill's machine, which he built by himself, can spin the cams up to high engine speeds and video the results in slow motion.  So, you can see exactly what the valvetrain is doing at high speeds, and determine if it is solid for performance use. 

The head I sent to Bill is set up with the same valves and springs as what I wanted to use on this engine, and I want to run it 7500 RPM.  So far Bill has found that the valvetrain is stable at 7000 RPM, but not at 8000.  He also has noticed the onset of smoke from the rocker adjuster tip to valve tip interface is sooner with this cam than it was with the previous set of cams (which Bill also tested).

http://youtu.be/Di4_aBUssnA

The smoke is not really a big concern for me because the amount of time that the engine will spend at these high speeds is very limited in a drag application.  But the valvetrain instability at 8000 RPM is a problem; my old cams were stable with this spring/valve setup at 8000 RPM.  So the reduced base circle of this cam definitely has hurt RPM performance.  I may need to look at increasing the spring rate or seat pressure to compensate...

At what rpm did you have smoke with the previous cams and what rpm did you spin it to?

[WConley]

At what rpm did you have smoke with the previous cams and what rpm did you spin it to?

With the standard base circle and maximum lifts around 0.700", I saw the oil start to smoke around 7,500 - 8,000 rpm.

With this setup, smoke started around 6,000 rpm.  This is due to the increased adjuster scrubbing from the higher lift.

Given the obvious heating going on, I didn't dare exceed Jay's requested test rpm of 8,000.  In previous tests running sustained in oil smoking conditions, I have repeatedly burned up the adjuster and valve stem, to the point of shooting the broken valve at high velocity out the side of the machine ;-)    For this test I only kept it at these speeds for a few seconds.


Note that this oil smoking problem only occurs with the elephant foot adjustable rocker.  Non-adjustable rockers have a curved shoe surface that keeps feeding fresh oil to the interface.  I've also run a double roller rocker that Barry R. developed.  With these setups I have exceeded 11,000 rpm with no heating or smoking issues.

[fe66comet]

Holy crap 11000 that is  like modified motorcycle rpm, a  big block v8 must sound crazy spinning that fast.....Jon

[WConley]

Holy crap 11000 that is  like modified motorcycle rpm, a  big block v8 must sound crazy spinning that fast.....Jon

A while back Jay sent me some HONKIN' valve springs to test.  10,000 rpm with with so much pressure over the nose can contribute to bad things:

http://www.youtube.com/watch?v=MXrQw8cXEiI

Note that this is with the double roller rocker.  No smoke at the valve stem tip!

[cdmbill2]

So assuming the roller tip rockers aren't usable for this application (you'll tell us why I hope) what about using the equivilent of valvespring oilers for that rocker to valve tip location. The over spray would cool the spring in any event. As that appeared to be a front cylinder I wouldn't think torsional flex would cause the instabilty; is a different lobe profile in order?

I now know what a dropped Ti intake does, and its not pretty, so more frequent spring replacement and valvespring oilers are on my Drag Week 2014 short list. The cylinder wall damage has forced me to 598" which I'll need to stay within shouting distance of your rides Jay. I'm going on the Fox body diet for 2014 to try and keep up.

[jayb]

Bill, I have to admit I'm disappointed to hear that you will be going Fox.  Makes perfect sense, of course, but the 60s and early 70s cars are the ones I prefer, despite their disadvantages.  I have always admired the prom queen's ride...

On the rocker arm thing, the issue with the SOHC is that a roller tip rocker will require lash caps of varying thicknesses to lash the valves.  This is fine if you are close to stock geometry, but with the variations in the SOHC cams that I have (including my new one with the reduced base circle), the thickness of lash caps can get excessive.  Besides, I don't have any of the roller tip rockers, and they run $2K per set 

I have run the adjustable rockers since I started with the SOHC, and have never had an issue up to this point.  I think this is because the engine spends such limited time at high RPM; only a few seconds here and there on the drag strip.  Nevertheless your idea of oilers for the valve tips has a lot of merit, and I will consider adding something like that to this build...

[Barry_R]

Its not all that hard - just a pain in the checkbook and the calendar to set up.

You first need to spend a small fortune on rockers - not much more than the normal ones from T&D - but still....

Then you mock up the cam and use a pair of "normal" valves to determine the length you really need.

Then you get valves made with a shorter OAL or tip length to accommodate a .080 lash cap - making sure they are at least a few thou too long to allow some adjustment.

Then you adjust each valve by trimming the stem and/or lash cap to hit your cold target during assembly - it only takes forever.

It works really well until somebody gets the wrong cam and negates all of the effort....not that that has ever happened...

[cdmbill2]

Jay, the Fox deal was my last choice, but as you better than anybody know the somewhat arbitrary rules regarding front suspension modifications leave us Ford guys at a susbstantial disadvantage to the GM and more specifically Chevy, Nova, Camaro with their bolt on front clips. My theory is kill the class for one year and get parity for our traditional muscle car platforms after all the chevy guy whinning subsides. I'm dying to do a 66-67 Fairlane or a 65-66 fastback Mustang.

Then its time for parity in the Gasser and Hot Rod classes. One of yours or Barry's SOHC's in a stretched nose 65 fastback would be ideal in my view.

[machoneman]

Hey, now we're talking business!   

http://www.autoweek.com/article/20100520/collector/100529971

http://www.dearbornflashback.com/66afxlog.asp

[cdmbill2]

Exactly, especially the "Batcar" approach with a steel unibody as the starting point.

[turbohunter]

Man, you guys are really getting me horny to fill this.


Sorry don't mean to hijack or anything.
Just having to much fun.

[jayb]

Looks like a perfect spot for cammer to me...

[turbohunter]

Oh you are evil