Check machined surfaces
All machine surfaces should still have an original machining pattern. Check for obvious signs of an orbital sander has been used to clean off gasket material or to clean up a corroded water jacket, this can remove too much material and leave gasket sealing surfaces compromised. This is sometimes done to hide bad pitting from water damage.
Look for previous blasting profile. Depending on the media, blasting these areas can leave the surface less than favorable for gasket sealing. Also a concern would be the rounded off machine edges, these edges should be sharp so they get a good bite into the gaskets.
If a sander has been taken to the machine surface there is a good chance that the machined edges will be slightly rounded off. This is sealing ares that cannot bit into the gasket, leaving a small area that can trap dirt and moisture which will eventually destroy the seal.
Pitting, water damage & corrosion
Check all around the water jackets and look for signs of pitting, this is possibly from sealant not compatible with aluminum or incorrect antifreeze. Weakness in this area could cause water leakage in the future. Some cases can be filled with JB Weld to restore the gasket surface.
Check all fittings into the water jackets for signs of previous corrosion and fillers such as JB Weld, not that there is anything wrong with that, but you have to wonder why it was used previously.
Check to see if the thermostat area is still in good condition, corrosion is this area could cause water leaks and big headaches, also weaken the casting and become unstable & prone to breakage around mounting holes.
Denting and gouging from sloppy use of tools during re & re.
This occurs when the incorrect use of the tool is being used and lost of control occurs, something usually goes flying if your lucky your fingers were out of the line of fire, but in most cases the manifold usually gets a small dent that is very noticeable.
Don't confuse dents caused by dropping the manifold or having parts dropped on to it. Being kicked around the shop floor which sometimes makes scratches on the bottom of the plenum. A lot of damage can occur if a manifold or a valve cover is dropped from bench height. Depending on how they land, they could be bent or hairline cracked.
Using anything but what the manufacture suggests could prove to be a nuisance when trying to use a wrench or a socket, often this situation leads to gouges in the runners of the manifold from the tool.
Vibration wear, over tightening depressions & mushrooming
Look at all mounting holes for signs of over tightening(which can also cause warping), using incorrect size or type bolts and washers or using no washers. Some times larger washers are used to cover up and this ends up causing further damage.
Previous refinishing jobs
"It's not pretty it just looks that way!" Typical glass beaded jobs although look all one uniform color, can still have other minor problems, If the profile it too rough, it will be hard to keep clean and stain easily.
Some types of blasting left to an untrained eye can cause damage and unfavorable profiles for painting and other surface coatings. In some cases the media itself can leave behind harmful contaminates which become a problem and usually shows up with-in a few years.
Some times trapped contaminates will bleed out of the casting resulting in possible engine damage. Previously glass beaded parts are always a concern for this reason alone. Rough castings will trap the glass bead and it becomes loose when the engine goes through the hot and cool cycles. Glass beading on the in side of the runners on the manifold runners can also cause damage, there is good possibility of casting flaws inside allowing glass bead to become trapped in the cleaning process and once installed in your engine the particles come out inside the induction system when it gets washed down with fuel.
Powder coated parts make poor cores. Popular finishes like powder coating are great when new, but after a few years can start to deteriorate. If incorrect preparation was performed prior to powder coating. There is a good possibility of the coating flaking off. Watch out for manifolds that have been coated with anything on the bottom or inside areas of the valley, once this surface becomes unstable the material will come off inside the motor, damage to the engine can occur. Unless powder coasting jobs are very old, they can sometimes be very hard to remove and will contribute to the cost of restoring the part.
Painted surfaces can hide all kinds of defects, the use of putty's and filler is common on show cars. Painted parts some times have so much paint you cannot read the casting numbers or the brand name. Sometimes this is done on purpose to hide evidence of damaged or ground off casting numbers. Mounting towers or bosses are cleverly removed for a custom, this type of manifold has limited resale value.
Hidden repairs & cracks
Most hot rodders are clever yet skilled journeymen and actually do such a good job that you never even know there was a problem. So try to have an open mind, taking a chance a on a rare piece being sold as is, well... you will probably find some one who can fix it, so use your judgment on the value of the piece of course. Almost anything can be fixed if you know the right people. So when haggling over the price remember some aluminum welders aren't cheap! Especially the good ones.
One problem is when a previous crack have been improperly repaired, leaving a void of metal to rework the profile or leaving large air bubbles in the weld, in this case the part must be brought back to a good aluminum welder and re welded leaving enough metal to contour a new profile.
Cracks around bolt holes, Look for signs that an inexperienced lad forgot to unfasten one bolt, prying on the manifold to hard will result in either a broke off corner or if your lucky just a crack, Or if your not lucky then it's probably warped! When these manifolds are for sale, the usually are right off the engine with all the accessories in the way of looking at it real good and some times this little crack is cleverly hidden with gobs of silly cone!
Heat cracks on the bottom of the plenum from the exhaust temperatures in the x over. This allows heat to escape into the valley of the engine, this usually results in a large amount of baked black crust on the bottom of the intake making the crack invisible until restoration.
Some modifications are done to lighten up a part, now this can also be tricky, because if you have no prior knowledge of how the part should be to start, you really have no way of predetermining if strength has been compromised and a crack could develop down the road. When parts have been trimmed for the purpose of lightening, they need to be shot peened to relieve any stress.
Previously damaged and incorrectly welded repairs can be a nightmare. Even very skilled welders are at the mercy of the casting. Not all damage can be repaired, but the ones worth saving are also worth doing right.
Casting flaws
Casting flaws...err rr. I hate these, they can be problematic. Pin holes, pin holes, pinholes, did I mention pinholes, plenty of them, hundred and hundreds of them, some filled with particles of the original casting sand trapped beneath the surface. Weak sections that may collapse, common in marine applications where water conditions are always a challenge.
I have been witness to porous casting bad enough to cause vacuum leaks and water right through the surface flaws and others that have oil drawn up right through the plenum from the engine.
No two pieces of cast aluminum are the same. The elements it is exposed to will have a great effect on the actual structure of the casting and if will become unstable at some point in the future.
Custom modifications
Always have a good look at what you need to purchase before looking at the item for sale. Remember every detail about the mounting brackets and make sure something hasn't been modified. Custom rods and race cars are famous for these mods.
Stains
Harsh chemical used to remove the dirt and scum build up can leave permanent discolor streaks, the other problem with these chemicals is that sometimes the stains are permanent and require a lot of material to be removed before a uniform profile can be achieved. Chemicals used on very porous manifolds can actually trap these corrosive containments in the surface profile and deeper by penetrating the pin holes in the casting. These chemicals can bleed out after the parts are installed and gone through a few regular cycles of hot and cold on the engine.
Warping
This could happen a number of ways, when a welding repair is made incorrectly, or if an engine over heated due to a fire or any other higher than normal incident, evidence of this can be cleaned away by cheap sandblasting and would appear fine. So this a tricky one to spot, its hard to know for sure if it is warped. Closely inspect all mounting holes for depressions and mushrooming which is a sign of over tightening. In some cases warping can be corrected by resurfacing and your local machine shop should be able to check it for you.
Good resale value
Most hot rodders I know change manifolds and engine combinations all the time, so keeping your parts looking pretty to retain their resale value is always a good idea. One EXTREME Glass Beading job and it looks great and cleans up real nice after many seasons of use. |
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