577" SOHC

[jayb]

The SOHC heads will fit any FE block, but if it is not an original SOHC block you will have to run an external oil line from each head down to the pain for drainage.  No big deal.  Also a 390 block will have to be notched a little for valve clearance, but again that is no big deal.  Lots of people have put SOHC heads on 390 blocks.  The big issue will be fitting it in the car.  The SOHC engine is 31" wide at its widest point.  You will need serious shock tower surgery to fit it in your Comet.  A lot of people convert to a Mustang II front end and cut the shock towers completely out...

[fe66comet]

I already have decided to go 427 or 428 on my next build. I definitely will stay Ford on my front end as the Chevy stuff is way to heavy. Or possibly go with a new front sub frame all together I can go tubular arms that way and avoid a lot of current headaches I am dealing with now. Handling is definitely a priority  there........Jon

[WConley]

You need the full 4.23" bore 427 FE block (factory or aftermarket).  You can go bigger, but any smaller and the valves won't fit.

Cammers ain't cheap!!

[jayb]

Gotta disagree on that one, Bill.  I have a good friend running the SOHC heads on a .040" over 390 block.  The bores had to be seriously notched, but it all fits...

[fe66comet]

I am not a believer in notching cylinder walls, besides affecting the integrity of the deck and wall it also does not help the top ring any either. I have seen too much go wrong there when you start getting crazy. Saw an example of that on a supercharged Ford 460 a couple weeks ago. Walls gave out, Ford racing block trashed......Jon

[WConley]

Color me surprised!!  Are the valves standard size?  Does the cylinder wall even reach the chamber wall on the head?

I have never heard of such a thing.

[jayb]

Valves are 2.25 and 1.90 if I recall correctly.  I'm sure the chamber does not meet the cylinder bore walls.  He is running a 4.25" crank and 6.700" rods, and the biggest concern was notching the bores enough for valve clearance but not so far down into the cylinder that the notch went into where the top ring is at its highest.  I didn't see the engine in short block form, but I'll bet the notch extends down at least 0.200".  Just doing the math, the .040" over 390 bore at 4.09 is 0.140" smaller in diameter than the 427 bore.  That means that from the top the bore would have to be notched 0.070" to clear the valve, and of course the notch gets shallower as you go down the bore, since the valve angle is working for you.

[turbohunter]

Hey Jay
Are there any standards to look for in a block that you would do this to?
Such as a minimum wall thickness.

[jayb]

I don't think so.  The deck of the block casting is at least a half inch thick around the bores, so notching the bores for the SOHC valves should not be an issue in any FE block.  Depending on the piston the top ring may come up to within .300" or so of the deck, which is the real concern, I think.

[turbohunter]

Kinda makes me horny thinkin' about it
I've got a '66 with a mustang II front end and no engine.

[WConley]

Sheesh!  I would have thought you'd need to at least start with a 428. 

Just got back in from the garage - working on a pretty ratty Dove aluminum SOHC head.  Yeah the valves look bigger than stock, but man it's hard to believe that thing could work on a 4.09" bore!

I had success once running a set of 427 Low Riser heads on a .030" over 390.  I had to notch the exhaust side about 1/4" down the bore.  laid it out with modeling clay, and it ran just fine.

- Bill

[jayb]

The valves in that head are actually 2.35", I think.  It is a pretty ratty head, having been the one on my big SOHC when the T&D rocker seized on the shaft and hung the exhaust valve open.  Valve kissed piston, head came off, bounced around in the chamber, etc.  But, its only a Dove head

[fe66comet]

The example I saw in the 460 block was  without heads, just a short block but there was a lot of material missing there and not tapered or canted. Must have been a big .800 solid roller cam or something. Lots of boost too, the pistons had a huge dish. I have a buddy that does race chassis, engines and paint so he gets some not so well thought out engineering thrown his way to fix....Jon

[turbohunter]

460 Jon?
Sorry went back and caught it.
But are the two different blocks the same thickness at the top o' the cylinder?

[fe66comet]

Yes but I only saw half the mess, the part that was beyond repair. I have seen this happen a lot when I worked for Performance Auto Machine back in the 90s, usually with nitrous or turbo where pressure and, heat is high. Of course any wall can  fail if pushed like a case of pop cans left in a hot car at Disney all day LOL. I actually saw that, pretty funny a whole case at once of grape soda inside a mini van ROTFL looked like Barney exploded.