(Catching up...) OST-085: 7AG Big Valve build w/Cat Cams 262 9.0mm lift cams

[oldeskewltoy]

Boy that title was a mouthful... As is with other "catching up" threads, I'll be posting the entire build in the first post.






This is what arrives....




The head goes through the usual routine - cleaning, and pressure checking the casting, but before any porting takes place all the valve seats are removed....



... and in this case the head waits.... and waits..... and waits.

After nearly a month I ask Mike what's the delay - their source for the big valve valve seats hasn't got any!

Good thing I use two different shops - I ask Ted, and he gets the new seats in 5 days!





After nearly 6 weeks, the head is back in my hands, and the new Cat cams have arrived. First job fit the new cams to the bare head - make sure the spin freely





The chamber side prior to porting - note the added intake side oil drain - another request from my client




Porting finally begins.... cylinder #1




Cyl #1 on the right.... keep your eye on the flaw, and cavity in #4 bowl (far left)




Here is a before and after showing the short side of the intake bowls of #1 and #2 cylinders




As you can plainly see ALL of the casting flaws just disappear....... but do they??? The 2nd gen largeport, and the smallport are common to have poorly aligned/cast heads.


How bad you say... here is an intake bowl still showing the original casting even after moving the bowl wall nearly 3/4 of a milimeter (.030")



It isn't a huge flaw - now, but with a standard valve in there the flaw would have been power robbing!



With the bigger exhaust valves and bowls... a larger exit is required....



....from roughly 29mm-30mm, out to 34mm. Gasket can handle 35mm outlet.


With Porting complete, the head goes back to Loynings where they put the head in their Rottler seat and guide machine to cut a fresh 3 angle into those new seats.





And just prior to final assembly

[Vaptor]

Another Great Head

Do you have any pointers on how best to be add a intake side oil drain, on a Big Port?

[banpei]

Beautiful work as always!
What would you suggest if the flaw would have been bigger? Get another head and hope there isn't a flaw or the flaw is smaller?

[Ivan141]

I would expect a TIG torch is able to reach in there.. you could just fill it up with weld.
Anyway.. nice work, I'm also interested in some pointers on the extra oil drain.

[oldeskewltoy]

working the oil drain is no small feat.... even when installed correctly, they can be fragile.

Adding it starts with courage (about to drill and could possibly ruin the head), and a wide selection of drill bits, along with burrs to get the hole open in the right place. Then the tap is used to further open the hole and add threads.

This was a gif from about 7 years back....



The problem with this one (above) is it can interfere with coolant plumbing at the back of the head. As my work later progresses, I move the fitting for better fitment.



Using essentially the same tools (various drill bits, and burrs) to properly open the hole to accept the 3/8" NPT tap.


briefly speaking to its fragility.... and placement




I offer 3 types of fittings....

[Vaptor]

Thank you for this great post, now I have some pointers to show the machine shop, when I get to this stage (Will get it done before Headwork, just to be sure).