monday i took my cylinder head to the local NAPA machine shop to check for cracks and warpage. on wednesday the "head man" agreed to magnaflux the head while i waited.

he lightly ran a wire brush over the inside of the head on the combustion chamber, sprayed a thin spray of some kind on the chamber, put what appeared to be an electromagnet on each cylinder top in turn, and immediately pronounced the head good.

is this right? the whole procedure took about a minute!

i'm impressed with the speed and ease of this process. maybe i should open a shop, "Discount Magnaflux" and make a fortune charging cut rates for a minute of work!

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'84 2m4 se, a work in progress http://www.mtsu.edu/~mkr2c/fiero.htm

Yep. That's about it. He was spraying a mist of fine iron filings over the head. He then attaches the magnet and magnetizes the area he sprayed. This will cause the little iron bits to aling with the north and south poles of the magnetic field. If there is a crack, the little guys will stand at attention along the edges of the crack. That makes hairline cracks very easy to see.

Of course, this only works on ferrous metals (metals that contain iron) like cast iron and steel. For non-ferrous materials (aluminum, magnesium, titanium, brass, etc.) they use a dye-penatrant method. They spray a flourescent dye on the part and shine a black light on it. The dye will concentrate in any cracks and glow when the light hits it.

Pretty cool stuff.

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cool!

on monday he said he's never heard of combustion gases escaping into coolant, and acted like no-one ever pressure tested a head. yesterday after magnafluxing (is that a word?) he agreed to pressure test it, then if it passes he'll check for warpage and if appropriate mill it. he said he'll be done friday, so i'm hoping for results on saturday.

i want to get this car on the road before we invade iraq and gas prices drop again.

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'84 2m4 se, a work in progress http://www.mtsu.edu/~mkr2c/fiero.htm

Like tesmith66 said, thats the correct way to magnaflux a cylinder head.

Having said that, I question his ability to diagnose if it was cracked or not.

The heads on our 2.5L Fiero's are more common to cracking the heads than what a quad 4 blows a head gasket, or a Mitsu engine throwing a timing belt!
Thats how bad they are.

Did he remove the valves and magnaflux the area inside the intake and exhaust passages? That is where these heads crack, right around the cavity where the valve's pass through the cylinder head in those ports.

Magnafluxing the combustion chamber will not find these cracks.

good luck

napa is fairly good hi-priced but they do know whatup and can get quality rare parts too
I use them as a last resort

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Question wonder and be wierd
are you kind?

I also Question NAPA's ability to do anything. Better to put your faith in the machinist himself cause NAPA will hire any flunky.

Those 2.5 heads can crack in many places. Along with what Jelly has mentioned those heads can crack on top too. Like in between the vavle springs next to the middle exhaust ports. Least I had a head like that. It was a major reason I went to the v8.

Fair Warning Beware of NAPA!!!
It has been my experience with them that they will cause you to spend more than you should due to thier inadequate machinist.
I have stopped funding for thier education.

I have complete faith in NAPA as a parts supplier because that's what they are.

I wouldn't trust 1 thing they did machine shop wise unless they actually HAVE a REAL machine shop. There are a few nationwide that actually have a real machine shop, but I'm betting I can count them on both hands.

Alot of NAPA stores send their machine work OUT to a NAPA FACTORY MACHINE SHOP that prob services 100 or more stores. My experience with these is that they are quite good and quite expensive. Use a local machine shop you know!

Phil

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87 FIERO GT 2.8 5spd
0-60 in 6.8 seconds!

As with any parts store, including GM, you can find people that are good and bad. I buy a lot of parts from NAPA and have always had good results. If I need a head checked for cracks I go to a machine shop........Paul

nope, he didnt check under (above) the valves.
looks like you folks are telling me if he doesnt find the crack i have reason to believe is there, i need to try another machine shop. i must admit, so far im not impressed with the quality of their work.

[This message has been edited by lurker (edited 02-27-2003).]

Yep... stood and watched the head for my 87 done... It was fun!... All 3 minutes of it.

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BlueGT

i dont like napa for machine work either.

i was in the head shop of ARI for 18 months. i posted this responce to a different tread so some of it may not apply to you.

(sorry, i'm to lazy to edit it)
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I’m kinda worried about your #4 it’s way off base.
What do you mean by exploded radiator?

If you have a combustion chamber leak it may not appear until the engine is hot so a compression test is not always a good sign.

Does your temp gauge ever show that it is overheating?

I want more testing before you pull off the head.

Cylinder walls can crack too to let hot gases in the cooling system, 2.5 heads crack a lot more often on the top where the valve springs are than in the combustion chamber.

If you are going to get that deep in to it and take it to a shop these are my suggestions.
Tear the head down completely, Even take out the temp sending units. Don’t bother cleaning it cause the machine shop will charge you for it anyway.

You will need a valve spring compressor for this, if you don’t own one most auto part chain stores have a tool rental program.

After you have the valve springs off make sure the valves slide out of the guide easily. If they hang up, stop. The tip of the valve where the rocker arm hit has spread out a bit. Use a fine file to clean up the very edge of the tip so it will slide out easily. Wiggle the valve head from side to side, you will have some play on an engine with miles on it but it should be very slight. If it can really rock back and forth then the guides are worn and may need knirled and reamed or completely replaced. (if you are really anal you can keep track of which valves fit in to which cylinder by doing this one at a time and marking them, but most markers will rub off easily if any oil get on them take a box and punch 8 holes in the top to slide the valve in upside down)
Take the valves over to the bench grinder with a wire wheel and clean all the carbon and varnish off of them. the top sides will really be a pain but they will come clean. And one more thing, KEEP YOUR FINGERS OUT OF THE SPINNING WHEEL.

Take head and box of valves to machine shop.
Have them first crack test it, then suck test it, then surface it.

While it’s at the machine shop and after it passed the crack testing procedure of your choice (see lower half of my post). Have them “suck” test it. if it suck tests ok, then you would be wasting your time laping in the valves. It will actually suck test a lower score after you lap in the valves. But if you really must do it use a water based valve grinding compound rather than a grease based, it’s easier to work with and a lot easier to clean up afterwards.

If it’s passed tests this far, then have them surface the head. Most shops will charge you to straight edge a head, and then not give you any credit for testing it when they charge you again to surface it. just surface it and be done with it.

While you’re putting it all back together, If your guides have marginal wear, you can put umbrella seals on the intake valves in addition to the o-rings to help cut down on oil usage.

TESTING FOR CRACKS.

Pressure testing and magnafluxing both have their places, die penetrant tests aren’t much help unless the surface is smooth.

Magnaflux (the one used by a magnetic field, ferrous power not the namebrand die penetrant) is the most positive test for an iron part unless the crack is in a place like inside a intake or exhaust runner or inside a bolt hole.

Pressure testing is where they bolt rubber backed metal plates that are cut out in the shape your gaskets, thermostat housing and any other fittings that may go on the head where a water passage is. So now the water passage is sealed from the outside world. One of the metal plates has a quick connect on it for an air hose and the coolant passages of the head are pressurized with air and the whole setup is lowered in to a tank of water to watch for bubbles.
The problem with pressure testing is you cant run past 30 to 45 psi because the air bubbles start to leak past the rubber on the metal plates. So the tank looks like a hot tub and you cant see if bubbles are developing along a crack.

Die penetrants are for aluminum and home owners.
Clean the area to be tested thoroughly. Spray the penetrating fluid on it and let set a moment. Then spray with cleaner to wash away extra penetrant. Spray with developer and any penetrant that soaked in to a crack will appear, they make many different colors to match your car’s paint scheme