I've been diving into the complexities of dynamic compression ratios and I was wondering what some of you guys who have been around this green earth longer than I have know about the threshold for cylinder pressures. Since this forum, and my interests, revolve around the FE, lets base this knowledge off of FE pistons, including the SOHC, for N/A and FI. I'm looking at how much the DCP increases with the DCR and the increases aren't huge. I'm seeing 8.18:1 with 165.7 psi and 8.50:1 with 171.94 psi in a a 427 example (4.238" bore, 3.784" stroke and 11.067:1 SCR), at sea level with 0 boost. Please correct me if I'm wrong, but what makes the fuel mixture detonate is too high of a DCP and cylinder temp. I would think if you were around a detonation threshold at say 170 psi, you could decrease the lambda a little bit to give it just enough cooling from the fuel to offset it. This is all based on theory however, so I figured it's time to ask the wise men around here. On a related note, is it correct to set boost to 0 for a N/A engine? Thanks in advance

I was thinking about the oiling system for the SOHC and how the oil is pumped through the rocker shafts. Are the ends of the rocker shafts open or closed? I would figure that there would be a benefit to capping off the ends of the rocker shafts with machine set screws in order to allow oil pressure to build up in the shafts if they aren't. By having the rocker shafts open on the ends, excess oil just runs out the sides. Thoughts?

Does anyone have more information on this spacer clip? Any design information?

Several years ago I got my hands on a copy of this issue (I collect a lot of 60's area mags on the SOHC and the Cobra) and I'm getting around to sharing the scans I took of it so many years ago. Enjoy. Open the image in a new tab to see it full size.

I've been doing a bunch of calculations, for fun, and after a particular DCR I figured it is worth talking about with this awesome lot. I've been looking at the DCR for the original SOHC crate engines and I'm not sure if I believe the rather high DCR I've found. It would explain the decent performance of the crate engines but I'm not sure if they are accurate as such a high DCR could lead to trouble. Below are all the factors I used to compute the dynamic compression ratio.

Bore: 4.232"
Stroke: 3.784'
Rod Length: 6.489"
Static Compression Ratio: 12.01:1
Intake Closing Angle ABDC: 57

   The ICA value comes from the following cam specs and calculation.

   Factory Cams Profile
   Lift:  Intake - 0.433"  Exhaust - 0.433"
   Duration (seat to seat):  Intake - 258  Exhaust - 258
   Lobe Separation Angle - 108

   ICA = (Intake Duration / 2) + LSA + total advance (ground in advance + timing advance) - 180
   ICA = 129 + 108 + 0+0 -180 = 57

Altitude: 0 feet, sea level
Boost Pressure: 0 PSI

Plugging these values into this calculator: http://www.wallaceracing.com/dynamic-cr.php  Gave me a DCR of 10.08:1 with a dynamic cylinder pressure of 213.82 PSI. I know this is largely effected by the static CR and the ICA. If you're running high compression, you almost have to run an aggressive cam to bleed off some pressure. But the cam used is rather mild, resulting in a low ICA. So I wanted to check with all of you if this made sense. Below are my two sources for the specs.

http://www.racedyne.com/Racedyne_Inc./427_SOHC_Cams.html
http://www.carmemories.com/ford-engine-specifications/ford-427-428-429-specs/427-motor.html

I would also really like my sources to be confirmed or be corrected on the specs. I care a lot about historical accuracy.

I realized last night that I am sitting on a bunch of research on the SOHC, including intake manifolds. Some of these have been found on eBay over the past 5+ years and as such, are no longer visible. I can't remember finding anywhere online where someone could find out information specifically about the SOHC intake manifolds. If the intake was a Ford part, I tried to get the part number whenever possible. Some of these intakes though are very, very rare. More pictures can be found in the link below.

https://plus.google.com/photos/108907720764484306437/albums/6146185049650914321

Single Carb Intakes

The first one is a single carb, dual plane with p/n C6AE-9424-J, which is identical to C6AE-9425-J as far as I can tell.




Below is C6AE-9425-J




The last single carb intake I know of is C6AE-9425-I. I have only confirmed the existence of this intake on 1 cammer, found in a Starline. I got the p/n from an eBay listing, I believe I spoke to the seller about it.




Dual Carb Intakes

I only know of one factory dual carb intake, C6AE-9425-L. Robert Pond makes a repro of this.