[supernovanator]

May be looking into some 64cc heads for $30 tomorrow or Monday but I have no idea how to check for cracks/etc in places other than the surface. Is there really any way to check the valve guide areas and such or will they need to be taken to a machine shop and magna-fluxed?

 

[Vin63]

Have the heads pressure tested.

 

[Paul Wright]

First, visual checks can find obvious problems. Spray carb cleaner in the ports and see if it leaks past the valves. This test alone will smoke out many a "recently rebuilt" head.

Bring a spring compressor and pop off the springs and check the seats for cracks. The area between the seats is prone to cracking. Bring a small wire brush to clean off carbon. Once clean the crack may be visible. Bring a magnifying glass.

The proper way to check guides is with a bore gauge or a go-nogo gauge, but you can do a quick check with the wiggle test.

Over ground,sunken seats are a problem on decades old heads. Look at valve margins. Narrow or non existent margins mean new valves needed. If the seats are sunk, they need machining out and inserts installed.

Most of these swap meet quick checks can weed out "good deal" junk, but if you aren't familiar with heads you may not spot everything. Take it to the shop for pressure check and mag check. Good luck.

 

[Nova_Guy]

If you can pop out a couple of valves check the middle exhaust valves. On the later model heads you can often see the cracks in them. They often crack right there because of the amount of heat in that part of the head.

 

[stock z/28]

Just my opinion here so take for what its worth (about nothing).


Im not a big fan of relying on a pressure test of a cyl head. I have seen a lot of heads that had cracked chambers that would not leak in a typical pressure test of say 40-50lbs, of air. Heads with this type of crack may never let coolant, seeing as to how the cooling system pressure is probably much less than 40lbs, and the coolant is much more viscuss? (thicker- you know-what ever) leak into the cyl., but that dosent mean that cyl and or cumbustion pressure/gases will no leak into the cooling system, especially under load.

In my opion if a head leaks during a typical pressure test it obviously has a problem, but just because it dose not leak is no real guarantee it is ok.

If its iron would magnaflux the chambers as well. Some cracks (as was prevously stated) are so large you can see them easily, some are not.


I have been told there are pressure testers available that use arould 2500lbs of inert gas (argon?) in the chamber to look for leaks, but Im not aware of any locally.


Sorry to ramble (i need to avoide this site-it is very enjoyable (atleast for me) but it does consume a lot of time.

Jeff

 

[74 hatchback]

bring a can of carb cleaner and spray down the chambers and gasket surface wait for them to dry then were ever it remains wet will be a crack.

 

[supernovanator]

Sorry to ramble (i need to avoide this site-it is very enjoyable (atleast for me) but it does consume a lot of time.

Jeff

NONSENSE I enjoy every tech post you and all the gurus here make.

bring a can of carb cleaner and spray down the chambers and gasket surface wait for them to dry then were ever it remains wet will be a crack.

Awesome, will do. Now hopefully this guy will email me back about them. I know I was the first one to email him too.