Cylinder head from RockAuto

[powderfinger]

Hello, I am new to the forum. I just purchased an 85 720 ST with a blown head gasket, engine was rebuilt a few years ago. My plan is to get it running and fix it up, replace parts, paint it, etc. I just took the head off of it this evening and it definitely did have a blown head gasket between cylinders 3 and 4 but unfortunately there is also a bad place in the head that I think is too deep to be machined flat.

 

Has anyone here purchased a re-manufactured head from RockAuto and if so were there any issues? I would upload a pic of the damage but I don't see an option to attach a picture.

 

 

[datzenmike]

Continuously running with the gasket blown will cause erosion from hot corrosive exhaust passing between cylinders. I would have it TIG welded closed. then milled flat and a new gasket, just to be sure. That's got to be cheaper than a new head.

 

The Z24 is notorious for blowing the head gaskets every 100K miles. The preventative measure is to re-torque the head bolts once a year. Loosen one bolt then tighten to 60 ft lbs. Then move to the next and do the same. As long as you do one at a time you don't have to follow any special sequence.

[powderfinger]

Thanks, it looks like that is exactly what happened. The head gasket blew and the previous owner drove it too long, probably trying to limp it home.

[datzenmike]

It will take longer than that but I've seen this before. A small dab of aluminum TIG welded in will seal it up. A shop can check for warp with a straight edge and surface grind the head to make it absolutely flat. If you can get any feeler gauge over 0.004" to slide under the straight edge it should be milled down.

[powderfinger]

Thanks, I found a local shop to do the tig welding and surface grinding work. Unfortunately, once they cleaned the head up they found two cracks so I guess I'll be getting another head.

[Madkaw]

I’ve got a spare ,  but don’t know the condition. I think it needs guides . It came from a running engine .

[Charlie69]

I would find another used head and take it to your machine shop and have them go through it and be sure it is checked for cracks.  If you buy a recondition head online you do not know what you are getting and if there is a problem it is a hassle at best to get anything done about it.

[datzenmike]

On 5/17/2019 at 9:55 AM, powderfinger said:

Unfortunately, once they cleaned the head up they found two cracks so I guess I'll be getting another head.

 

 

Likely cracks and the hole was from over heating. Head warps gasket blows... and they kept driving. The exhaust see sawing back and forth through the blown gasket will over time erode a larger gap in the aluminum.