Sealing Valve guide bores

I'd still be very interested to know if new, properly seated guides resolve the issue. Please post the result.

BC

Stillreel said:

I'd still be very interested to know if new, properly seated guides resolve the issue. Please post the result.

BC

Click to expand...

Will do, though it'll be a few weeks at a guess.

Machine finnish is rubbish...guess these where cheap ?

pommie john said:

Well, I've found why oil drips down the left intake guide.

What a dreadful bit of bodging. It had some loctite under the flange too.

Click to expand...

also beware when you buy new valve guides that the OD of the guide does not taper i had this happen a few years ago the guides went in tight but leaked when i took them back out there was only a witness mark of contact at the bottom of the guides, i took them back to the shop and searched through their stock with a micrometer until i found 4 that were parallel ,,,,,,,,,,,,,,,baz

I was about to ask.
Did they actually heat the head with a torch with the rocker arms & spindles in place?
But then I read!

Because they chilled the guides in LN2 @ -320 deg F +- WTF?

How did they get the old guides out without heating the head to + 300 deg f or so

even at LN2's _320 deg F the dimensions of the guides is so small that they could never shrink enough to slide right in or out without heating the whole head first.
Just apply the coefficient of expansion to bronze 3/4 in in dia.

Just a Note here, Total seal piston rings recommends seals on all 4 guides when using their rings.
I have seals on all 4 of my valves and have not had a problem. but you need to make sure the guides are machined properly and the seals fit tight and do not interfere with the valve spring assembly.
Getting the proper seals is very important or they can go up & down with the valve and pump oil down the guide.
you should look for cracks in the Alum.around the valve guides!

The witness of ally smearing on the guide suggests the hole is'nt round? nore a proper interferance fit.

john robert bould said:

Machine finnish is rubbish...guess these where cheap ?

pommie john said:

Well, I've found why oil drips down the left intake guide.

What a dreadful bit of bodging. It had some loctite under the flange too.

Click to expand...

Click to expand...

Bruce MacGregor said:

I was about to ask.
Did they actually heat the head with a torch with the rocker arms & spindles in place?
But then I read!

Because they chilled the guides in LN2 @ -320 deg F +- WTF?

How did they get the old guides out without heating the head to + 300 deg f or so

even at LN2's _320 deg F the dimensions of the guides is so small that they could never shrink enough to slide right in or out without heating the whole head first.
Just apply the coefficient of expansion to bronze 3/4 in in dia.

Click to expand...

I make that 0.0029" contraction on a 3/4" bronze diameter,if your starting temperature is 68 F (20C).Your interference fit would be about 0.0015" and not much more.

Heating the head to remove guides is BS.You'd be lucky to reduce the interference by 0.0004" if you increased the head temperature by 100 C.It's also more likely to gall at the higher temperature,as you're punching the guide out.

It's better to drill the guts out of the guide (but not near the top) to reduce the wall thickness down to about 0.030".The guide will then be nowhere near as tight.Soda blast ALL the carbon off the guide inside the port.Then put a punch in from the port side,and punch against the step left from drilling.You're stretching the guide and reducing it's diameter momentarily with each hammer blow on the punch.

Thanks for all the replies. It definitely needs the guides bores machines out for larger guides, so I've entrusted it to a guy who comes recommended ( the last lot came recommended too but I'm hoping this one's a bit better).
He does drag bikes and a lot of race stuff and he sounded like he knew what he's doing when I spoke to him on the phone.

I ordered a set of +10 guides and they've arrived, but on inspection they are too long in the part that's under the valve. The boss is too long and looks like it will hit the spring retainers on full lift.
It's a simple job to turn them down a bit, but just one more hassle.

Thank god theres some people on this forum with common, i have drilled guides for years, ...but dont try it unless you have the experance and skills, AND GRIND THE DRILL WITH NEGITIVE _ZERO RAKE! other wise it will grab!

X-file said:

Bruce MacGregor said:

I was about to ask.
Did they actually heat the head with a torch with the rocker arms & spindles in place?
But then I read!

Because they chilled the guides in LN2 @ -320 deg F +- WTF?

How did they get the old guides out without heating the head to + 300 deg f or so

even at LN2's _320 deg F the dimensions of the guides is so small that they could never shrink enough to slide right in or out without heating the whole head first.
Just apply the coefficient of expansion to bronze 3/4 in in dia.

Click to expand...

I make that 0.0029" contraction on a 3/4" bronze diameter,if your starting temperature is 68 F (20C).Your interference fit would be about 0.0015" and not much more.

Heating the head to remove guides is BS.You'd be lucky to reduce the interference by 0.0004" if you increased the head temperature by 100 C.It's also more likely to gall at the higher temperature,as you're punching the guide out.

It's better to drill the guts out of the guide (but not near the top) to reduce the wall thickness down to about 0.030".The guide will then be nowhere near as tight.Soda blast ALL the carbon off the guide inside the port.Then put a punch in from the port side,and punch against the step left from drilling.You're stretching the guide and reducing it's diameter momentarily with each hammer blow on the punch.

Click to expand...

What direction is the "smear" of aluminum? That is, can you tell whether it occurred on the installation, or on the removal?

Not that it matters much at this point.

Has anyone used loc tite or similar to deal with this problem?

xbacksideslider said:

What direction is the "smear" of aluminum? That is, can you tell whether it occurred on the installation, or on the removal?

Not that it matters much at this point.

Has anyone used loc tite or similar to deal with this problem?

Click to expand...

It happened on the way in... I could see it down the inlet port before I stripped the engine.

With Al on guide implies it became its own boring tool not expected interference fit. Its takes some time for the head Al to actually expand to the guide bore dept from heating so if in too much a rush might as well saved the gas.