barracuda

i stopped at my local auto parts store today and bumped into a fellow CTD owner...had an 01' w/ a 4" exhaust and a k&n filter...no other mods EXCEPT...he installed a pyro gauge, he drilled into the manifold at the correct spot but he drilled a hole the size of the probe and dropped it in...it seemed to be tight but could anything happen because of that?? the guy was pretty cool and i told him about our site, i told him i would post and give him a call to let him know....What do ya think??

wannadiesel

The probe could pop out, and a jet of 1300 degree exhaust could bubble the paint on his hood. Actually, if it fits snug cold, it should fit tighter the hotter the manifold gets since the manifold expanding should make the hole smaller and the probe heating up will be bigger. I think over time vibration and erosion from exhaust leakage will make the fit looser and it will pop out someday.

BigBlue

Depending on how much the metal expands, I'd be kinda worried bout crushing the probe. I've had my probe come out before (forgot to tighten it :) and you could tell when it came out. Didn't affect the paint though. Ran it that way for about 20 mins.

Thomas

&quot;the manifold expanding should make the hole smaller&quot;<br><br>I think you will find that the diameter of the hole increases as the manifold expands.

wannadiesel

[quote author=Thomas link=board=7;threadid=16839;start=0#157842 date=1057704376]<br>&quot;the manifold expanding should make the hole smaller&quot;<br><br>I think you will find that the diameter of the hole increases as the manifold expands.<br>[/quote]<br>When metal is heated, it expands in all directions. If you wanted to put a tight fitting gear on a shaft, would you heat the gear? If you did, the fit would be tighter because the metal expands in all directions, making the bore of the gear smaller. I know it's counterintuitive, but it's the way the world works.

Thomas

When a piece of metal is heated, any two points of the metal will become further apart, even if the points happen to be on opposite sides of a hole in the metal. Wheelwrights make use of this fact when fitting iron tires on wagon wheels, heating the tire to increase the diameter of the hole in the iron tire. After the iron tire is in place on the wheel, the tire is rapidly cooled, shrinking the hole in the tire for a tight fit on the wheel.

crabman

Yep, one way to get a bearing or gear onto a shaft is to heat it in oil on the stove, will often allow it slide right on. Dont do it with one of your wifes good pans though...

wannadiesel

OK, I guess I'll have to tell my customers who use liquid nitrogen to shrink 2 foot diameter gears to get them on shafts to stop it, they're violating Gary's laws of physics and wasting a heckuva lot of liquid nitrogen. Believe me, it blew my mind the first time I saw it. The wagon tire analogy doesn't apply here, because of the relative thickness of the metal in the two different planes. Say the thickness of the tire is about 1/4 inch, the &quot;length&quot; of the tire is probably around 150 inches. When the metal expands 1% in all directions with heat, obviously the 1% of 150 inches will have more of an effect on the size of the hole in the middle than the 1% of 1/4 inch. Now when we're talking about a 2 foot diameter gear with an 8 inch diameter bore, the metal still expands in all directions. This makes the 8 inch hole smaller, by 2% if we're going by the expansion given in the wagon tire example. This is also why engines have tighter clearances when warmed up, the bearing bores get smaller and the shafts get bigger. It's hard to wrap your brain around it, but it's the way the world works. As to why the heated bearing or small gear works, see the wagon wheel example. Same thing happening on a smaller scale.

phox_mulder

I really don't want to stick my neck out into this one, but here's my analogy.

Expansion Joint on a concrete freeway.

Joint is basically a space between 2 slabs of concrete.
As the concrete heats up and expands, do the 2 slabs get closer together, or farther apart.

Closer, why, because the joint shrinks.

So, heat makes things shrink.

Right?



phox

hotdram

I interned at General Electric Transportation Systems for a while in school. We made diesel-electric locomotives (way cool to watch the assembly process on these things 8)). When the wheels are pressed on the the axles (this makes a &quot;truck&quot; assembly), the wheels are heated in order to expand the hole in center. The wheel is then slipped over the axle and allowed to cool.
In this case, it depends on the coefficients of thermal expansion (CTE) involved. Two dis-similar metals heated to the same temperature will expand to different dimensions (and in different directions) due to their different CTE's.

rattle_rattle

[quote author=wannadiesel link=board=7;threadid=16839;start=0#157861 date=1057707410]<br>[quote author=Thomas link=board=7;threadid=16839;start=0#157842 date=1057704376]<br>&quot;the manifold expanding should make the hole smaller&quot;<br><br>I think you will find that the diameter of the hole increases as the manifold expands.<br>[/quote]<br>When metal is heated, it expands in all directions. If you wanted to put a tight fitting gear on a shaft, would you heat the gear? If you did, the fit would be tighter because the metal expands in all directions, making the bore of the gear smaller. I know it's counterintuitive, but it's the way the world works.<br>[/quote]<br>I worked in a jet engine plant for several years. We did the oposite of what you just said. We heated the gear and froze the shaft with dry ice.

KATOOM

The heating to expand theory is correct. I can put a bearing on a shaft buy heating the bearing and cooling the shaft. They slip together. As for the wagon wheel trick, which is right...If you drill a small hole in the wagon wheel then heat it up the hole will get smaller but the wheel will get bigger. When you heat an object it enlarges and any hole or crack in it gets smaller. <br>I wouldnt do what he did with the probe. It has to leak at some time. How does he position the probe right in the middle of the manifold and keep it there? If he ever gets an exhaust brake then it will surely pop out from pressure.

AKDSLDOG

Well heres my 2 cents. lol<br><br>At work we use dry ice to &quot;shrink&quot; king pins for the cat graders. And we also &quot;BAKE&quot; the timing gears to expand and fit on the cam.<br><br>Cold shrinks<br>Heat expands<br><br>I have seen some bisare stuff when heated, but, expanding in all direction, even pushing in on a bore? Not saying your wrong but I haven't seen it. Timing gear has a bore to fit the cam shaft, it grows, not shrinks.<br><br>

KATOOM

<br><br>You are contradicting yourself with the last comment. Heating is not like stretching out your t-shirt. Its like adding water to a sponge. Silly simile.