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Search found 277 matches

by 4sfed
Fri Dec 06, 2019 8:13 pm
Forum: Engine Tech
Topic: 3D Printing - Cool Assembly Tools?
Replies: 39
Views: 2784

Re: 3D Printing - Cool Assembly Tools?

The carbs have a rubber bushed support rod, but the typical soft mounts between carbs and manifold aren't needed.

BTW, I printed a couple ring squaring tools today. Thanks to whoever suggested that ... great idea.
by 4sfed
Fri Dec 06, 2019 2:13 am
Forum: Engine Tech
Topic: 3D Printing - Cool Assembly Tools?
Replies: 39
Views: 2784

Re: 3D Printing - Cool Assembly Tools?

here's a view of the model of the ring squaring tool I had came up with, for a reference I tried to attach the .STL but says that filetype is not allowed here this puts the ring about 3/4" down the bore. You're going to have a difficult time printing that design in one piece with FDM because of the...
by 4sfed
Sun Dec 01, 2019 3:29 pm
Forum: Engine Tech
Topic: Weld or putty
Replies: 12
Views: 602

Re: Weld or putty

The problem with epoxy is its coefficient of expansion. If that's your choice of repair method, I'd recommend looking for for one that is aluminum filled to match expansion rates as closely as possible.
by 4sfed
Sun Dec 01, 2019 1:17 am
Forum: Engine Tech
Topic: Weld or putty
Replies: 12
Views: 602

Re: Weld or putty

This is an excellent candidate for a weld repair. Clean the surface all the way to the bottom of the flaw with a cabide burr, weld (100% penetration), finish the weld within 0.010 then peen the weld with a round nose punch. Unless it's peened, a weld will have a residual tensile stess ... which coul...
by 4sfed
Sat Sep 07, 2019 9:48 pm
Forum: Engine Tech
Topic: Freezing tri metal bearings with Liquid Nitrogen
Replies: 24
Views: 1068

Re: Freezing tri metal bearings with Liquid Nitrogen

Ok, good luck! :D if the press fit is on the high end of sanity, might do you good to use a lube such as..... standard silver anti-sieze, or coating the parts in soot, are the best lubes i know of for steel in aluminum press fits. I've had good luck with cutting oil for aluminum. I prevents aluminu...
by 4sfed
Fri Sep 06, 2019 11:58 pm
Forum: Engine Tech
Topic: Freezing tri metal bearings with Liquid Nitrogen
Replies: 24
Views: 1068

Re: Freezing tri metal bearings with Liquid Nitrogen

Case is nicely chamfered as are the bearings, I have a delrin driver, nothing to hold them together though A chamfer is not good enough. Break the sharp edges of the chamfers with some 320 grit wet-or-dry paper ... 0.005 in radius is enough ... and you won't have any shaving of the aluminum case.
by 4sfed
Thu May 23, 2019 4:19 pm
Forum: Engine Tech
Topic: Ring direction for obsolete engine?
Replies: 19
Views: 1838

Re: Ring direction for obsolete engine?

The contract edge always goes to the bottom. Put a set on a piston and slide it up and down a couple times. Pull it out and look at the face of the rings. You should be able to tell which edge is touching the bore.
by 4sfed
Thu May 16, 2019 3:42 pm
Forum: Engine Tech
Topic: Thread engagement
Replies: 32
Views: 1589

Re: Thread engagement

Walter R. Malik wrote:
Thu May 16, 2019 9:17 am
It make little sense to use a bolt or stud which takes more torque to stretch it, than the metal it is going into will handle.
True, but cost is the only downside to using the higher grade fastener. The modulus is the same so the stretch will be the same at a given torque.
by 4sfed
Mon May 13, 2019 3:41 am
Forum: Engine Tech
Topic: Damaged Spark Plug
Replies: 23
Views: 1429

Re: Damaged Spark Plug

Never would have imagined that cause, but it makes perfect sense now! I suppose the larger OD of the Helicoil left such a thin wall between it and the (oversize?) valve seat recess that it cracked and blew through.. PS: What's holding the valve open? The distance from plug to valve seat was already...
by 4sfed
Sun May 12, 2019 9:53 pm
Forum: Engine Tech
Topic: Damaged Spark Plug
Replies: 23
Views: 1429

Re: Damaged Spark Plug

Roundybout wrote:
Sun May 12, 2019 7:30 pm
Does that plug hole have the threads repaired with an insert?
Yes, a Helicoil. Not particularly well done.
by 4sfed
Sun May 12, 2019 4:08 pm
Forum: Engine Tech
Topic: Damaged Spark Plug
Replies: 23
Views: 1429

Re: Damaged Spark Plug

Finished the weekend with no other issues. Cranking compression was down on that cylinder (80 psi vs 220) but never got worse. The replacement plug started showing the same type of damage after one 30 minute session. After removing the head, the cause was pretty obvious ...
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by 4sfed
Sat May 04, 2019 2:47 am
Forum: Engine Tech
Topic: Damaged Spark Plug
Replies: 23
Views: 1429

Re: Damaged Spark Plug

The bottom 3 threads are burned ... 1/2 normal height. At the location of the damage, it's burned to the root.
by 4sfed
Fri May 03, 2019 7:10 pm
Forum: Engine Tech
Topic: Damaged Spark Plug
Replies: 23
Views: 1429

Re: Damaged Spark Plug

Looking through a borescope, there's no damage to the piston to indicate mechanical damage. I can't see the valve seat, but the damage is right next to the exhaust valve, which shows no signs of distress.

We've installed a new plug and will run it tomorrow ... checking after each session.
by 4sfed
Wed May 01, 2019 10:44 pm
Forum: Engine Tech
Topic: Damaged Spark Plug
Replies: 23
Views: 1429

Re: Damaged Spark Plug

It's the correct plug for the engine ... I've built dozens of these. I haven't seen the engine myself, only photos from the client. I'm guessing it was loose, possibly arcing to the head? He said it unscrewed easily, that he didn't notice the damage until they were all out. The engine is in a vintag...
by 4sfed
Wed May 01, 2019 9:58 pm
Forum: Engine Tech
Topic: Damaged Spark Plug
Replies: 23
Views: 1429

Damaged Spark Plug

This plug was removed from a good running vintage sports car after 3 race weekends. The other three are normal. Any idea what could cause this type of damage?
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