Loose guide

[Bevel bob]

My head was "race" ported by a previous owner and the inlet guide having lost its boss has come loose (again) . An oversize guide will only be a temporary fix so something better is needed. I will probably have it welded and machined out to take a bigger guide, but wondered if a boss could be built up with resin around the guide to fix and give it more support, too much of a bodge?.

[CanuckDuc]

This issue is typically due to the guide hole no longer being round and straight from poor previous guide installation procedures. As long as there is some material section left, a boring head/mill can cut a fresh hole that coupled with an oversized correctly tight new guide corrects this. Not a backyard fix, but that is often the cause.

[Bevel bob]

you may be right that a really tight accurate fit may provide an adequate solution, However it would depend on how much port roof is there and that is the question, how much is enough?. We have no way of knowing how tight the orriginal guide was when the porting was done, may be it was tight ,certainly the guide hole would not have been belled out before the porting and removal of the boss. There is also plenty of "wisdom" that porting leaves the guide with poor support. I was hoping that I could avoid "expert" attention and using a high temp 2 pack resin filler "stick" the guide back in and build up a boss around the std bronze guide which is a good fit to the valve. I know that these resins are used to shape inlet ports on some motors and that the Ducati is a cool running motor. Perhaps no one has tried it on a single Duc. The cam I'm using has low lift and long duration so may be less stressfull to the valve action.

[Jordan]

I don't know if resin would work, but what if it became dislodged?
Maybe the debris would go safely through the valve seats.

[CaptonZap]

I don't know if resin would work, but what if it became dislodged?
Maybe the debris would go safely through the valve seats.

Here are some thoughts on that subject.
Epoxy resins get soft when heated. The type governs that temperature, but usually around 350 deg F things start loosing their grip.
This application is an inlet tract, so anything in the air stream is going to be bathed in a cooled flow of vaporized gas.
The head is going to be conducting heat to the interface of the added epoxy and the head, so that will be the place that the epoxy is subjected to the hottest temperature. Thus the first place that break down will occur. Most heads operate below 450 F, and the inlet tract surface temps would be one of the coolest places on the head due to the cooling effect of the charge. So maybe the temperature would be around 350F at that point.????
If a threaded stud or two was screwed into the space that the epoxy is to occupy, the stud/s would provide a mechanical support to the filler, and since they would be in the cooling stream, they would restrain the filler piece, even if the bond between the head and the filler was degraded by heat.
Now, getting the studs in there might be a trick, unless you are a dentist, or have access to his tools.
But where there is a will, there is a way.
What happens after shut down, and heat soak gets to the filler, is another question. How many times can epoxy be heated to softening and cooled before some deleterious effect renders the epoxy unusable?
I say go for it, and keeps us updated on the outcome.

That's it from the peanut gallery, CZ

[Bevel bob]

Still in the stripdown stage,I used some locktite to stop steel bushings turning in ally housings and it worked a bit too well making it difficult to strip. I will get my engineer buddy to look it over ,he may have a better plan. The loose inlet guide is the only thing that needs attention ,pretty fair considering its had 7/8 years regular use by me including 3 x 10 days riding round the IOM and 36 laps belting round the Jurby track.It was a clanking ,grinding wreck when I got it.Just new bearings and carefull assembly.I think its earned a proper job.

[Jordan]

Sometimes heat has to be continuously applied to overcome the Loctite bond, during removal.
An electric hot air gun can be used.

[CaptonZap]

Very few of the anerobic adhesives, (Loctite et al) maintain strength above 300 degF or so. Which will not harm aluminum cases. Put the case in an oven set at 350 or 400. Let it soak for half an hour. With some thick gloves, remove it, and you should have no problem taking the sleeve out. The Loctite should be about like cold honey, not runny, but soft.
Some Loctite has an operating range higher than that, but it is not an ordinary run of the mill off the shelf item, and you will have had to shop around to find it And if you did, you will have, or should have, noticed a high temperature label on the package.
http://www.criticaltool.com/loctite-272 ... readlocker
Good luck, and let us know what worked.

CZ

[Bevel bob]

The adhesive I was considering for the guide has an operating range up to 500f.

[Eldert]

the highest temp epoxy i have seen is Manley miracle seal epoxy 40180 .

i use it al the time on my cilinderheads when i break thru the fins when porting a cilinderhead .

it can withstand temps of 1350 degrees fahrenheid .

Eldert