By Brandon Baldwin
It’s now winter, so many of you may be doing your car projects to get ready for next summer. For many, it may be engine building, so I’m going to sway off the emission track for a bit. I’m close to finishing the 3rd head gasket job I’ve done in the past year. Of course, some engine jobs are more than head gasket jobs, but even if you are doing a short block, you are into doing a head gasket. Hey, there’s one of those terms that those of you who are new to this may have heard before: short block. It doesn’t matter the manufacturer, a short block is the engine minus the heads or anything above that point. In other words, it’s the block with the pistons and rotating assembly in it. So, first we will consider the short block when doing a head gasket job, in the order you would do it.
1. As you pull each head bolt out, even if you are going to replace them, put them through the bottom of a upturned card board box, or in a designated engine assembly stand, or if you have your own way of determining it that is fool-proof, make sure you can identify where EVERY bolt came from. I found that this is a great way to determine the area of failure of a head gasket (not just looking at a gasket) or where it would have failed. The coating on the bolts is a good indication of what is leftover in the head bolt holes, which you will need to clean out. If it is clean enough that you would consider licking it if you had to, then it’s clean enough.
2. This bolt assembly card board can be written on with a Sharpie so you won’t confuse the bolts or direction on the head front to rear where they came from. And, don’t count on remembering. Sometimes life gets in the way and you may not get back to it when you thought you would. You’ll be glad you provided yourself directions when you finally get back it, and man-o-man it is so much faster to put back together. (My students who don’t follow this warning often spend wasted hours looking for the right bolt for the right hole because they are in a hurry to take it apart.) Put it in a very safe, and hopefully dust free spot.
3. When you are removing the head bolts, you will remove them in the reverse order of tightening. This usually means starting from the outside and moving towards the inside in a circular pattern going inward like a snail. But, you should read the manufacturers directions. You will place the bolts in the small holes you already punched in the cardboard box (or other labeling method you use).
4. Before you remove the head, which may take prying or use of a rubber mallet to break it loose, have a designated spot to put it that is contaminate free. Flat cardboard works well for this too. I’ve seen some techs slide the head on a bench only to work harder later to get the scrape marks off the head.
5. Use a fresh gasket scraper to gently remove old head gasket material on both the head and the short block. This is far more critical for those working with aluminum heads and/or blocks, which is what I’m focusing on as the end product turns out better anyway.
6. Next, measure the head warpage (if you have the means to do so). I’ve gotten a few head gasket jobs because the head was warped and the tech just replaced the gaskets without checking. If the warpage is greater than specifications, you will need to take the heads or block to the machine shop.
7. Here is where we may sway from the old techs: the cast iron heads and blocks could take the use of a right angle die grinder with a brown 3M cookie disc, or the GM approved yellow or green plastic teeth disc. These work fast to remove the foreign material from the surfaces. BUT, if you are on aluminum, this old method will embed the foreign material into the aluminum. AND, the discs are far too abrasive so you will remove more block or head material than you are aware of. (Thank you to all of you who do this because I have gotten cars for $500 or less. This method leads to either another head gasket failure soon after the job or complete catastrophic failure, which I can fix too. But, this article is for the members so that they don’t make a costly mistake.)
8. For aluminum, use sanding blocks. Of course, you can buy different grades of sand paper for sanding blocks, but you can use counter top sink cut-outs or some other perfectly flat piece. Many manufactures recommend 50 RA or smoother. I shoot for 13 RA which is close to looking like a mirror finish. I mean, you can see the reflection of something in the surfaces. If you go to a reputable machine shop (such as Paul Dyke Jr) your head surface roughness will be at 37RA. But, if you use the sanding blocks, you will see the machine tool marks, yet be able to get smoother. The smoother you get it, the better the head gasket sealing surface, the longer it will last. You can do this in a few ways, but I use multiple sanding blocks starting at 320, then 600, then 1200. I have a student who races lawnmowers and this method had him going from 3 head gasket failures per racing season to none. But, this take time to go to this degree.
9. Once you have prepared the surfaces and cleaned them of any oils, you will install your head gasket. Please pick a good one. Why cheap-out on this? Make sure you are installing the head gaskets with the right side upward so that the coolant and oil passages line up. There should be line-up dowel/tubes so that the head will line up correctly.
10. Install the head making sure you line up the dowel/tubes line up with the right openings on the head with sliding it around to find those spots.
11. Install new head bolts. ARP makes the best. READ the directions. Some head bolts come with a special lubricant for the threads of the head bolts. If you use the manufacturer’s head bolts, you will most likely be directed to use a drop of the engine oil you will be using on the threads, NOT a drop of oil in the hole. I’ve seen some jobs where someone either put some oil in the head holes of the block or didn’t clean out the head holes=the bolts will not go down all the way. This results in the wrong amount of clamping on the head.
12. Torque the head bolts according to the manufacturers directions or ARP’s directions if you bought ARP. Make sure you have the latest head bolt torquing directions as they may get updated over time. Subaru, who is known for head gasket replacement, is a good example of this where there are new directions. Take your time. This is very important. You will be starting at the bolts in the middle of the head and working your way out, just like squeegee of a sticker. You may need to re torque in the same sequence and even be required to loosen, then retighten to an angle rather than torque. Use a quality torque wrench that has been calibrated for assure the quality of your work.
13. Now you will move onto adjusting valve lash if needed and valve covers.
Happy New Year.