They look great but, the clearance around the plugs looks the same.

         Will this be enlarged to give the plug socket more room or is this the

         pre-production set? Can't wait to see flow results and dyno run....

                                                  Bill

       Not so, the heads will have a TON of deck material, you'll be able to mill them quite extensively. They are already going to be delivered with a smaller than G head combustion chamber, which will raise the static CR over any iron head. Also, as Charlie mentioned, Aluminum heads can be a half point higher at least and have the same octane requirement as iron. John has revised the chamber and relocated the plug, both of which are designed to lower the octane requirement over the iron version. I'll bet these heads will run 9 or 9 1/2 to one on 87 octane. Hows that? 

          I'm guessing, but I'd want to be down around a true 9:1 with a blower.

 Many of the modern engines run 9 or 10 to one with 87 or 89 octane, chamber design has improved a bunch since the early 50's. My 11 to one Triumph MC runs fine on 89 octane, and it's carbureted, no computer.

       The front brake does fool you. I fell for it. I had a 500mx, that I installed a Clews 608 kit and Jerry Branch cylinder head on. Also ran a 36 mm Mikuni, it was farly quick(!) for it's time.

    Buddy of mine timed me at 90 mph, on knobbies, on asphalt. I figured that was about enough!

Alan, Here's a shot of my T'Bird Sport (2003) at an antique M/C show in Ohio. They've changed a lot since the 60's. This is a 3 cyl, water cooled 900cc, with 6 speeds. There's a Sprint directly behind it, same motor, hard bags and fairing. The Yello bike in the back is an earlier Sport. Straight back, against the silver van is a new Bonneville. The Bonnies are still twins although they're completely new OHC, 4 valve, 890 cc enginges.

Here is the only motorcycle I have left its a '70 SL100, I had one when I was a kid and rebuilt it in my parents garage one winter. When I went away to school I sold it to buy a set of tires for My MG. This one I bought from a guy for $300 in 1983 it's been bored out to 122cc, WOW

     Probably not, we are a bit off the subject of Y-blocks here. I do notice Tim has a Triumph Herald and an MGB-GT, neither of which will have Y's in them either.

I think a Y-Block would crush the front suspention on the little Herald, I know it would shred the diff.

I tried to send you a PM about the Herald but it said your box was full.  My wife loves it, I don't mind maintaining it, and it is the only one around so we get more attention in that thing than any other car we have. They don't have to be perfect to be fun and interesting.

I read that the heads would have 14 mm plugs, maybe it is intended to use the ones with a 5/8 hex, which would use a smaller socket.  Don't worry, John will have it covered.  Wish I had my mag, it isn't here yet.  Maybe the postmaster is reading it.

John in Selma, IN

John

If the engine is completely computer controlled it should be able to run boost with the higher compression, right?

Computer control when done properly can potentially net you an additional point in compression over a distributor and carburetor initiated tuneup.  But the learning curve can be expensive as far as mapping an optimum or even safe curve when starting with too many unknowns.  Unfortunately in many instances you don’t know where the edge is until you’ve gone over it as evidenced by the amount of 4.6 Ford mod motor stuff I get in the shop as a result of over the edge mapping.  And much of this originates from running the compression ratio on the high or ragged side when turbocharging or supercharging.  I’m still an advocate of lower compression ratios in conjuction with higher boost pressures instead of higher compression ratios and lower boost pressures.

As far as machining the combustion chambers larger, I’ll pose this to John as he’s the one that will know this.  With a CNC program, the whole of the combustion chamber could possibly be machined which can potentially net a significant increase in combustion chamber cc’s without going very deep into the material.