I got my Offy 400 heads today and we found that the valves just touch the heads. I didn't think that would happen with the .364 lift that the Isky MAX-1 cam has. We don't have to fly cut much but I'm surprised we have to do it at all. What am I missing?
Ray, I'll have to check the thickness but I got them from Red's Headers who carries all the right stuff. What confuses me is the 400 designation on the Offy heads is for the amount of lift they can take and .364 isn't really close to 400 IMHO.
Look for a stamped number on the block-face of the heads. When they've been surfaced, the machinist usually stamps how much he's taken off on the machined side. Wish for no numbers. You may need to run thick gaskets to compensate. As far as I know, the only true way to know [if they're not stamped] is to measure the cc's of the cylinder head combustion chamber...
Rocky, These are brand new heads right from Offy so they shouldn't be milled. I guess I'll call Red and ask him. Certainly 400 Offy heads and a MAX-1 Isky is not an unusual combination.
I had exactley the same problem on my 59a. Offy 400 heads and a max-1 cam. I clayed both heads and one side was ok and the other almost touched! Goes to show that a lot of the blocks either had the valve seats set to different heights (from factory or during a rebuild) or had the decks machined to different heights. I ended up fly cutting one head only. I used copper (composite?) gaskets from Reds.
Shit...Ive got Offy 400 heads too. Running a Litterio L100 cam, which from memory maxes out at 375" lift. Now with 0.015" valve lash and a crushed head gasket of 0.035, you guys reckon Im gonna be ok clearance wise ? Oh and one other thing. The fucking plugs on these BRAND NEW heads are so shrouded, I reckon the plug couldnt fire a lawn mower, let alone a hot Flathead. Guess some chamber relieving is in order. Anyone else see this on the 400's? Rat
yeah, I unshrouded the spark plug area on both heads a little while I was at it. I don't think the problem necessarily lies with the heads. It's more of a problem with different vale seat, valve, and deck heights of the blocks. The .400 lift is probably assuming an ideal short block to Ford specs.
[ QUOTE ] Shit...Ive got Offy 400 heads too. Running a Litterio L100 cam, which from memory maxes out at 375" lift. Now with 0.015" valve lash and a crushed head gasket of 0.035, you guys reckon Im gonna be ok clearance wise ? [/ QUOTE ] Always, ALWAYS check the clearance yourself - too many variable out there compounded by old engines, different rebuilding "techniques" & old "hot rod" work - don't take anybody's word - check it.
what's the best thing to use to check it?...i hear all this about clay,but what kind and where do you get it?
You're right about the 400 SUPPOSED to be 400 lift. On the other boards we went thru this a couple years ago and discovered there's lots of variation from 1 set of heads to the next. Think of the 400 designation as a ballpark figure and CHECK clearance. These are afterall cast aluminum parts.
Check all valves on both sides. Remember flatheads aren't symmetrical--slightly different angles bank to bank.
Flat E Check it yourself. The block could have been decked, heads could have been milled, casting variations, etc. Better safe than sorry. And as the man said, flatheads are different valve angles side to side.
Guys...I ALWAYS check valve to piston and piston to head clearances, as well as other clearances. When the black comes back from the machine shop, Ill mock it up and see what I get. Still, the valves are shrouded a plenty the die grinder/sanding roll's gonna get a workout fer sure Rat
[ QUOTE ] i hear all this about clay,but what kind and where do you get it? [/ QUOTE ] Use regular modeling clay. I roll it into a small cigar shape & place it across the valve & wipe some oil on the top so it won't stick to the head. Put it all back together & turn the engine over by hand a couple times. Pull the heads & you should be able to measure the thickness of the clay.
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