The Ford Barn

40cpe · 03-24-2015, 12:15 PM

What critical flaw would a magnetic particle test show if a pressure test and visual inspection on a clean block are good?

Scott H in Wheaton · 03-24-2015, 12:52 PM

I'd hate to have it all assembled and installed, just to get it up to operating temperature and find out a crack that would hold pressure when cold (and not show up) got bigger when warm.
Kinda like buying insurance, some folks buy a whole lot more than others.

rotorwrench · 03-24-2015, 12:54 PM

Magnetic partical inspection or Magnaflux will show up cracks in areas that are easily visible such as the decks, valve pockets, main bearing webs, & pan rails. They won't show up cracks that are through to the exhaust tunnels or other places that are very hard to look at. A pressure test will tell you if it's holding its mud or not. Soapy water can be sprayed around about anywhere to find easy to see cracks and might even help in some parts of the exhaust tunnels that you can see down into if it bubbles up well.

The areas where water doen't flow need magnaflux.

supereal · 03-24-2015, 04:49 PM

We Magnaflux and pressure test all blocks before rebuilding because most of them have a crack somewhere. That is why the rebuilders include Barr's Leaks or other compound with a fresh engine to insure that small and hidden cracks are sealed.

40cpe · 03-24-2015, 05:03 PM

Super, what has been your experience finding critical cracks with magna flux that a visual and pressure didn't/wouldn't find?

Fordestes · 03-24-2015, 08:56 PM

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Magnaflux, hydrostatic pressure test and even look up superman and have
him use his exray vision if possible, I have pressure tested and a visual inspection has shown cracks where waterglass was used to seal on some engines, cracks in the main webs don't show up in a hydrostaic pressure test,I have scrapped several blocks that passed pressure but not mag.due to main web cracks.

Kahuna · 03-24-2015, 09:41 PM

Because of the expense involved in building a nice reliable engine, I feel it is also advisable to have the block sonic tested. This additional step will give the machinist a real idea re the ability to bore the block to a particular size.
JMO
Jim

03-24-2015, 12:15 PM	#1
40cpe Senior Member Join Date: May 2010 Location: Star, MS Posts: 4,025	Is MAG test necessary with pressure and visual? What critical flaw would a magnetic particle test show if a pressure test and visual inspection on a clean block are good?

03-24-2015, 12:52 PM	#2
Scott H in Wheaton Senior Member Join Date: Dec 2012 Location: Wheaton, IL near Chicago Posts: 861	Re: Is MAG test necessary with pressure and visual? I'd hate to have it all assembled and installed, just to get it up to operating temperature and find out a crack that would hold pressure when cold (and not show up) got bigger when warm. Kinda like buying insurance, some folks buy a whole lot more than others.

03-24-2015, 12:54 PM	#3
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,467	Re: Is MAG test necessary with pressure and visual? Magnetic partical inspection or Magnaflux will show up cracks in areas that are easily visible such as the decks, valve pockets, main bearing webs, & pan rails. They won't show up cracks that are through to the exhaust tunnels or other places that are very hard to look at. A pressure test will tell you if it's holding its mud or not. Soapy water can be sprayed around about anywhere to find easy to see cracks and might even help in some parts of the exhaust tunnels that you can see down into if it bubbles up well. The areas where water doen't flow need magnaflux.

03-24-2015, 04:49 PM	#4
supereal Senior Member Join Date: Jul 2014 Location: Iowa Posts: 1,634	Re: Is MAG test necessary with pressure and visual? We Magnaflux and pressure test all blocks before rebuilding because most of them have a crack somewhere. That is why the rebuilders include Barr's Leaks or other compound with a fresh engine to insure that small and hidden cracks are sealed.

03-24-2015, 05:03 PM	#5
40cpe Senior Member Join Date: May 2010 Location: Star, MS Posts: 4,025	Re: Is MAG test necessary with pressure and visual? Super, what has been your experience finding critical cracks with magna flux that a visual and pressure didn't/wouldn't find?

03-24-2015, 08:56 PM	#6
Fordestes Senior Member Join Date: May 2010 Posts: 887	Re: Is MAG test necessary with pressure and visual? Sponsored Links (Register now to hide all advertisements) Magnaflux, hydrostatic pressure test and even look up superman and have him use his exray vision if possible, I have pressure tested and a visual inspection has shown cracks where waterglass was used to seal on some engines, cracks in the main webs don't show up in a hydrostaic pressure test,I have scrapped several blocks that passed pressure but not mag.due to main web cracks.

03-24-2015, 09:41 PM	#7
Kahuna Senior Member Join Date: May 2010 Location: NorCal Posts: 2,617	Re: Is MAG test necessary with pressure and visual? Because of the expense involved in building a nice reliable engine, I feel it is also advisable to have the block sonic tested. This additional step will give the machinist a real idea re the ability to bore the block to a particular size. JMO Jim