anyone know what the min safe clearence would be between the ex valve and cylnder bore.... I don't have much.... I haven't figuered it out yet but I know it's less than .030"..... I'm guessing about .010".... it's pretty close

 

Wow, I thought they had more than that with the 1.65" exhaust valves.

A few questions:

How are you measuring it?
What's your measured cylinder bore diameter?
What heads are you using?

 

I haven't installed the pistons... so I set a head on the block.... I removed a ex spring and opened the valve with my hand.... I took a paper clip .037" and it wouldn't fit between the valve and cylnder..... The middle cylnders have more clearence than the end cylnders....

std. bore

c4aeg

 

My 11:1 390, I put the 1.65 exhaust valves in it - the machinist who did most of the work checked all the clearances for me, and if I recall correctly, he basically said something to the effect of "If it wasn't bored .030, it'd be pretty close". The big thing he was worried about was the flow potential, with the valve being that close to the cylinder wall...

Not that that helps you much

Come to thing of it, he might have notched the cylinder slightly to help it...

Wait for others here with more info to help more than I can...

 

I was curious so that's why I decided to have a look..... I've noticed the valve doesn't come in perfectly parralel to the bore.... so the farther you open the valve the closer it gets to the wall..... It looks like at about .750" lift the valve hits the cylnder.....I have a dial indicator at work....I'm trying to think up a way to measure lift now with a digital mic I have....

 

Egad. I wasn't aware they were that close. If it were MY engine, I would leave at least .030". Steve's book says they'll work without notches, but breathing will be improved if it is done.

Anyway, I'd have the cylinder bores notched.

 

Well I'll have to get that book.....Does it give specs on the notches.....?

 

Unfortunately no, it doesn't. I'd consult a trusted machinist (one who knows Fords).

 

Well, if it helps any, I know the Edelbrocks moved the valve over .060" to clear the bore on a 390. But, I think they come with a 1.66" valve and can accomodate the even larger 427 size valves (1.73" ??).

 

The Ford Muscle Parts books say the 1.66 valve will clear without notching the 390 standard bore block.

 

zsir take a look at this site. www.chuckbrandt.com click on engine buildup. Chuck used a 352 block bored to std 4.05 and notched the cyl. Shows a pic and some details that might help you. G.

 

I would take a small rubber band and put down low on the valve stem to give it some resistance...Of course you do know what you cam lift at the valve right? and then set your valve to that depth with the back side of the calipers from the top of the valve guide to the tip of the valve....and take your measurements at the bore then...

I dont know about the standard bore, But i am running a .030" over bore with 2.090" and 1.660" valves and a .576" lift cam without clearance problems..

Russ

 

Hi,

I have tried something like that allowing .040 for gasket thickness....I'm going to get my feeler guages from work....but it looks like about .010-.015" clearence....I just need to accuratley mark this depth so I can remove the head and see how far down in the bore this depth is....it has to be above the first ring land.....using that demension and the head gasket for refrence it wouldn't be that hard to grind or file a small relief....

 

wow, that's it exactly....thanks

 

check this out form www.chuckbrandt.com


http://www.chuckbrandt.com/f100xl.htm <---- not that is cool !!!!