Valve guides - any real difference between intake and exhaust?


#1

I goofed and put the intake valve guides on the exhaust side and visa-versa. No biggie, I can put my air hammer back to work and switch them out. But now I’m wondering if there really is a difference - other than the service manual for my 1999 Honda CRV saying the installed height of the new intake guides should be between 40.765 - 41.235mm and between 42.765-43.235 on the exhaust guides.
So what say you? Is there a real difference?


#2

I guess you would have to measure the diameter of the valve stems and compare to the inside diameter of the guides. I think they are actually different. But then again the memory gets a little foggy.


#3

Yep!

The bore for the exhaust valve guides is different for the intake valve guides.

They’re different because the exhaust valve guides and valve stems are exposed to extreme heat, so they must expand at the proper rate together. Where with intake valves and guides, these see ambient temperature, so thermal expansion isn’t as much of concern.

Tester


#4

You’re going to use an air hammer to remove them and possibly install them???


#5

I think OP means the head bolts will be removed with an air tool.


#6

There are air hammer attachments to remove and install valve guides.


#7

Ok, that makes more sense.


#8

The valve guide bores are the same, the valve stem diameter is thinner on the exhaust valves.


#9

I’m fully aware of valve guide drifts which are used to pound guides in and out of the cylinder heads. I’m against this method although I’m also fully aware of why many may do it; speed.

Due to the litany of issues (cracked head, deformed guide, mushroomed guide, seized valve stem, shattered valve guide, etc, etc, etc) that could pop up by using a BFH I prefer a press and in the case of particularly stubborn guides; drill them out to a thin wall thickness so they fall out.

I’m just not a fan of flogging on an aluminum head, or even a steel one, with the biggest hunk of iron in the box.