North American Turbocoupe Organization



Wallered-out valve guide...why?
BradM Offline
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#1
My #3 intake valve guide is toast, trying to figure out why (see video linked below). Head has 122k miles on it. I converted to a roller cam 2k miles ago (Boport 1.9 kit) and didn't notice any valve guide issues during install. I then developed high crankcase pressure; compression and leak-down were good. The other valve guides seem OK but I don't know what's an acceptable movement. Any ideas on why this happened?


https://photos.app.goo.gl/Pqtf23upreBrTheY7
1965 Mercury Comet Caliente; 1968 Mercury Monterey; 1969 F100 Ranger; 1987 Thunderbird Turbo Coupe
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spittinfire Online
Member
#2
Valve Stem To Guide Clearance
Intake 0.0010-0.0027
Exhaust 0.0015-0.0032
Service Clearance Limit 0.0055 Max.

It almost looks like a hardness issue but you would think if that were the case then it would have happened long before now. Or maybe it just reached it limit. Any evidence that the rocker might have been pushing on the valve in an odd way? Was the valve stem OK?

If it were mine I would either have liners put in each guide or have new guides installed. While you're at it have the valves/seats cleaned up and you should be good to go for a while.
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BradM Offline
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#3
Thanks for the specs. The valve stem had some slight scoring but didn't look much different than the others. I do suspect the rocker as this happened after the cam conversion. I sent my head (as a core) to Boport in exchange for a fully ported, bigger valve Stage 3 head with a 2.5 cam. I also sent him my rockers and asked that he inspect them (they came from him with the 1.9 cam kit). All of these roller rockers are used, I don't know of anyone who makes new ones. In the end I get a spare 1.9 cam with 2,000 miles on it and a big head/cam upgrade to my TC...but it wasn't cheap.
1965 Mercury Comet Caliente; 1968 Mercury Monterey; 1969 F100 Ranger; 1987 Thunderbird Turbo Coupe
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BradM Offline
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#4
I'm freshening up my lower end while waiting for the head and came across something really bizarre. All of the bearings are marked standard size (STD) but I found one half of one bearing that is marked 0025 (undersized?). It was on the top half on the front crankshaft journal. I've never seen anything like this before. This engine has never been opened before. BTW, all of the bearings were in great shape.


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1965 Mercury Comet Caliente; 1968 Mercury Monterey; 1969 F100 Ranger; 1987 Thunderbird Turbo Coupe
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spittinfire Online
Member
#5
The Boport heads are not cheap but from what I've seen they're really nice.  I would like to use one of their heads myself but it would blow my budget so I'll be installing valve seats and porting a head myself.  I'm curious to see how much the new head/cam wakes the thing up.   

I've never see a .010"/0.025mm bearing used on one side like that before.  I've seen/done that with .001" under bearings though.  When fitting bearings sometimes we run into a crankshaft that the journals are slightly small so the crank fits on the loose side using standard bearings.  Grab a set of 0.001" unders and it fits too tight but if you use one of each it fits like a glove.  Measuring/hand fitting bearings is time consuming but worth it in the end.   
I would mic all the journals to see if that one isn't undersized. In my mind it would have to be undersized because 0.010" is HUGE and would surely cause the crank to seize if the crank were the correct size.
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BradM Offline
Member
#6
Project Update.

I received my BoPort head (fully ported, stage 2.5 cam). He did a nice job and even called to ask what color I wanted it painted. Here's a few pictures of an intake port before/after and the difference in valve sizes. Going back together this weekend.


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1965 Mercury Comet Caliente; 1968 Mercury Monterey; 1969 F100 Ranger; 1987 Thunderbird Turbo Coupe
Mikey97D likes this post
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spittinfire Online
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#7
Awesome!!

I'm a little jealous, I would love to get one of his heads. As it stands I'll be using one of his 2.1 cams and doing everything else myself.
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