Valve guide replacement question

[Belgian1979]

I went to an engine rebuilder in my area to ask for a quote to replace the guides in my Dart pro 1 heads.

He suggested getting presized guides, which in his opinion would be faster to finish. His reasoning is that the guides when pressing them into the head tighten up a bit and then get honed to size. Is this a correct assumption. I want the clearances to be absolutely perfect.

[Keith Morganstein]

I went to an engine rebuilder in my area to ask for a quote to replace the guides in my Dart pro 1 heads.

He suggested getting presized guides, which in his opinion would be faster to finish. His reasoning is that the guides when pressing them into the head tighten up a bit and then get honed to size. Is this a correct assumption. I want the clearances to be absolutely perfect.

The only way to have them "perfect" is to install guides that are a little small on the id and then hone and or ream/hone to size. Anything else is just trying to get lucky. Often good enough for stock stuff, but not exact.

What method will the builder use to finish the guides? What equipment? How will it be measured? Much of this relies on skill and experience. It's easy to make a mess out it. If the person replacing the guides doesn't have the tools or skills, they would prefer pre-sized guides.

The valve job will have to be redone once guides are replaced.

[modok]

I've never any separate listing for "pre-sized guides" from the main stream suppliers.
Sometimes they do attempt to have them sized to require minimal reaming, and if they don't leave enough that sucks. and sometimes they leave a LOT, which is annoying as well, sure.
I wanted to point out is... that it is rather unusual to have a choice. The general procedures for how to size a valve guide are well established.

Tell him to join grow up and get a one pass diamond hone.

[mag2555]

Unless your planing on having a valve job done and possibly taking the chance of loosing a lot of meat out of the seats for future valve jobs to be done I would have liners installed, not complete guides!

If you want things dead on then how are your current valves, are they worn more then .0005" anywhere on the highly loaded areas of the stem?

[Keith Morganstein]

Tell him to join grow up and get a one pass diamond hone.

Im not the OP's machinist and am all grown up, but still use the Honall, guide mic and pin gauges. I've had about enough of that tedious routine though and have been looking seriously at diamond one pass honing.

[Belgian1979]

For clarities sake : are all replacement guides to be hone to size ?

[Keith Morganstein]

For clarities sake : are all replacement guides to be hone to size ?

No not all,
OEM replacement guides (for removable or "knock-out" guides) are supposed to be on size.
Aftermarket conversion guides are supposed to be on size, sometimes you have a choice of size.
Most solid bronze performance guides are undersized ID, and have to be sized.

[TMSJoe]

[He suggested getting presized guides]

I'm guessing what he was getting at is honing guides is not very fun. The more to hone the less quick it goes. Pre-sized will need to be honed most likely anyway due to the press fit and will just be less misery for him. Kind of like file to fit rings on a NO2 engine.

[modok]

For clarities sake : are all replacement guides to be hone to size ?

90%, in the rebuilding business.
there are some exceptions, most of the exceptions are industrial or antiques.
In NEW heads you might get away with pre-sized guides, in some cases. BUT, a bronze guide that projects out of the head for a distance, that's impossible. The area with press-fit around it will ALWAYS be smaller after you press it into the hole.

Besides honing and one pass hones, they can also be reamed with a carbide reamer.
A HHS reamer can work but in a good hard bronze it will be dull so quickly that's it's near useless.