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-   -   13.08mm Canyon guides (http://forums.pelicanparts.com/911-engine-rebuilding-forum/1021695-13-08mm-canyon-guides.html)

Jonny042 02-21-2019 06:45 PM

13.08mm Canyon guides
 
I ordered canyon guides before I removed my old ones thinking they would fit fine. As it turns out all my guide bores are in good shape (not enlarged) and the interference fit with the new canyon guides would be in the range of .0032-.0035". Probably just on the tight side of what the bentley manual says, which is already more interference fit that what Wayne's book says at .060mm (.0024")

Is that asking for trouble or should I definitely machine the guides down .001"?

Seems strange to me that Canyon sells these as standard guides, why don't they make them 13.06 to match the factory guide size?

Thanks in advance! Jon

Jonny042 02-22-2019 04:49 AM

So in the middle of the night I realized it would be a heck of a lot easier to just buy 13.06mm guides than try to machine the 13.08mm ones, but looks like that's the only size:

http://forums.pelicanparts.com/uploa...1550843015.jpg

Not that it's that difficult to machine a bit off the OD of the guides, it's just one more thing to build a fixture for, etc.

Of course the other option is to make the hole bigger - I have made zero attempt to clean out the guide bores (yet) and wonder if a few passes with a brush hone would be not only a good idea (seems wise to have nice clean metal for contact to my nice clean guides) but also bring the interference fit down to a more comfortable spec.

Has anyone honed their guide bores with a flex-hone to dial in the interference rather than machine the OD of the guide down?

Perhaps it's a matter of it's easier to mess up a guide and buy a new one than mess up a cylinder head and buy a new one...... have I answered my own question yet?

PS - looks like the guides coming out are about 13.06... go figure.

cgarr 02-22-2019 08:52 AM

Try a stock guide, not a 1st replacement should come in around 13.06 or .5141

Jonny042 02-22-2019 12:25 PM

OK, felling like a bit of a dummy..... although I have to say the Pelican website could use a bit of a tune-up. They list the standard guide as .514" and the first oversize (which I bought) as 13.08mm.

Stupid me for not doing the math. I laid awake half the night wondering how I was going take a .0005 cut with a lathe that I'm pretty sure has a mind of it's own at least 2 or 3 times that dimension :)

Thanks, Craig, for the wake-up call!

PS - any advice for cleanup of the guide bores in the head and recommendation for a common lube for install? WD40? Or should I order some mutton tallow? will bacon grease do? gaucamole?

Trackrash 02-22-2019 02:57 PM

Well, FWIW, I ordered standard guides, since my guide bores were in spec. Luckily I ordered a couple extra.

Turned out that half the guides I received were over size by a couple of thou. Long story short, I had to machine several of them down to the correct fit. Some guys will machine every guide to a perfect fit.

If you have a lathe, it is really no big deal to machine them down.

BTW, the original Porsche manuals say to use tallow for the install lube. Sun makes a valve guide lube, which is tallow based. I cooked up some bacon and used the grease, which is basically tallow.

If you read the Carrera manual, it says to use talcum. :D

Jonny042 02-23-2019 05:13 AM

I ordered standard guides last night - I'll measure all the 1st oversize ones and see if there's much variance, maybe keep a few (or all) to machine down if required.

I also ordered a dial bore gauge that will fit in the bore holes (.4--.7 range) - no huge rush on this and I'd feel better about my ability to measure the bore diameter with that over the telescoping gauge and the split ball thing I've tried so far. I don't find I'm getting very repeatable results and I'd feel better being able to slip the bore gauge up and down the bore and read the interference directly over the entire bore.

My concern withe machining the OD of the guide is if I somehow chucked the guide and the runout on the lathe is, say, .0003, I'm already going to be fighting tolerances. It occurred to me I could chuck some bar stock in the lathe and machine it to a slight taper but leave it chucked in position to "grab" one end, and use the live center to support the other end.

Not to mention it's not my lathe and I don't even know if it's set up to cut a parallel OD or if i'd end up with taper, etc. so I'd have to check all that and tune it up if required. Come to think of it I don't even know if the live center is actually centered to the chuck. I bought a test indicator though and have been slowly teaching myself about machining. Most of what I've been making so far have been lower tolerance stuff like drifts to remove the guides etc.

Probably a moot discussion though assuming the new guides are the right size.

Trackrash - a couple thou different? That's a massive size difference, maybe some first oversize guides got mixed in the standard bin?

Trackrash 02-23-2019 06:51 AM

It's been a while. But, like a fool, I just assumed what I was sent was standard and in spec. What happened was the third guide I went to install would NOT go in. Took me a while to figure it out, but several were over size. I don't remember exactly, but IIRC they weren't the first over size, as that would be .008" over. It just seemed to me at the time that the manufacturing tolerances or CC was not good.

Jonny042 02-23-2019 02:38 PM

I played around a bit more tonight and measured the 13 guides I bought. They all landed right around .5152-.5154, and were straight/parallel and round within a tenth so I expect the standard size will be perfect. Bores are measuring in at .5119-.5122 so I might be able to juggle them around a bit and put the biggest guides in the biggest holes but that's splitting hairs anyway.

Thanks for the advice everyone!

Neil Harvey 02-23-2019 03:36 PM

Quote:

Originally Posted by Jonny042 (Post 10366756)
I played around a bit more tonight and measured the 13 guides I bought. They all landed right around .5152-.5154, and were straight/parallel and round within a tenth so I expect the standard size will be perfect. Bores are measuring in at .5119-.5122 so I might be able to juggle them around a bit and put the biggest guides in the biggest holes but that's splitting hairs anyway.

Thanks for the advice everyone!

Danger , Danger, Will Robinson.

Jonny042 02-23-2019 04:07 PM

Quote:

Originally Posted by Neil Harvey (Post 10366798)
Danger , Danger, Will Robinson.

Maybe I wasn't clear. Not putting those guides in those bores. That's the whole reason for the thread. Just checking the Canyon guides for accuracy. They are nice parts. But I ordered the wrong ones. The smaller, std, 13.06mm/.514" ones should be a good fit and give me interference around .0015"-.0020". They are on the way.

Unless you are getting at something else, in which case I don't have a clue?

Trackrash 02-23-2019 05:27 PM

BTW, to answer you original question. I would use sand paper with the guide chucked in the lathe to remove .001".

Jonny042 03-18-2019 01:20 PM

Follow up
 
Just to follow up and close out this thread - I ordered the standard 13.06mm guides and measured them all and they are within a tenth of eachother. They'll give me interference press fit of about .0023-.0024" (.058-.060mm).

The tiny bore gauge is the cat's meow for measuring guide bores!

http://forums.pelicanparts.com/uploa...1552943600.jpg
http://forums.pelicanparts.com/uploa...1552943600.jpg
http://forums.pelicanparts.com/uploa...1552943600.jpg


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