After getting the pistons, cam, and oil pan back on in my last Operation Stude post I was super excited to get the rest of my Small Block Chevy buttoned up and back in the car! Before putting anything else onto my engine block, we first needed to clean out the bolt holes. For this you use a tool called a tap. Taps can actually create threads through a block of metal, but they’re also used when threads need fixed – or like we’re doing, just cleaning bolt holes up. Here’s a short explanation of how to use both taps and dies if you’ve never done it.

how-to-rebuild-engine-sbc-replacing-heads-02Before starting, you need to find a tap the correct diameter and thread count. If you’ve ever wondered why there’s different thread counts for bolts , I found this great explanation of fine vs course thread. You can see how much gunk a run through with the tap pulled out of a single bolt hole – these are the last dirty bits in my engine…woohoo!

how-to-rebuild-engine-sbc-replacing-head-gasketsOnce everything was out and the cylinders were cleaned and checked again, since these heads will be sealing the cylinders up for good, the head gaskets were added.

For many gals out there who’ve heard a mechanic say the head gaskets need to be replaced, they know this job is expensive and they may be wondering why. While the part is simple, the work done to get to this part is extensive…the head gasket is more or less in the middle of your engine (same goes for the piston rings!)

Replacing the head gasket doesn’t take anything special except for making sure everything is clean! My heads had already been taken to the machinest to be checked and decked – meaning that the lower mating surface was made completely flat. This is important because the bottom of the cylinder head and the top of the engine block need to form a perfectly joined surface in order for your engine to run properly!

how-to-rebuild-engine-sbc-replacing-heads-05On went the heads. Ethan put these on…they’re certainly not too heavy for me to carry, but they are heavy and need to be handled carefully.

how-to-rebuild-engine-sbc-replacing-heads-04If you read my last Engine Building Basics article, you’ll see that I discovered my heads are World Sportsman II heads. While I’ve decided to change my intake manifold and carburetor during this engine rebuilding process, the heads I’m keeping. They’re performance, but are mild enough for my SBC.

how-to-rebuild-engine-sbc-replacing-heads-03With the heads in place, it’s time to bolt them on! My husband mechanic says head bolts should not be reused when rebuilding an engine, so ours were replaced with a new set of ARP bolts from Edelbrock. Depending on the engine application, there will be a variety of lengths used on your head, as you can see above. If you’ve ever gone shopping for bolts, you’ll know that there are different grades of bolts. When choosing fastners for automotive applications, it’s very important that you understand that not all bolts are equal.

how-to-rebuild-engine-sbc-replacing-heads-bolt-grades-arpThis guide is from ARP’s 2014 Catalog, for MUCH more information on bolt manufacturing, strength, and what to use for which application check out the articles in their catalog.

Grade 8 is stronger than Grade 5, there’s also a Grade 3 but that wouldn’t be recommended for use on a car. You can see how much of a yield strength each has and there are many different versions beyond Grade 8. For Head bolts, they list the “A286″ material…which must be what mine are made of.

how-to-rebuild-engine-sbc-replacing-heads-torque-sequenceBefore getting too far on torquing head’s down, be sure you’ve got the correct head torque sequence for your particular engine. I found this SBC head torque sequence online and used it for reference. Going from 1 to 17, you start in the middle and evenly work your way out from there. Not only do you need to torque them in correct sequence, but also to the correct spec…

how-to-rebuild-engine-sbc-replacing-heads-gearwrench-electronic-torque-wrenchAfter snugging the bolts up per sequence chart, I did torquing in three rounds (some only do it in 2)…the idea here being that you want to evenly distribute the pressure as you’re bolting your heads down. Using my Gearwrench electronic torque wrench makes easy work of this, I made the first pass at 25 ft-lbs and then a second at 50 ft-lbs and lastly at 70 ft-lbs per specs for a SBC.

how-to-rebuild-engine-sbc-replacing-heads-01Now that my heads are on Studie‘s engine is beginning to look like a real engine again! Isn’t she purdy?

how-to-rebuild-engine-sbc-replacing-heads-07It’s always good luck to give your engine a little kiss now and again :) Onto the intake manifold and then back into Stude!

8 Responses

  1. JP Kalishek

    “Isn’t she purdy?”

    Of course. Always was jealous of Ethan … oh, wait … you were talking about the freshened lump of cast iron ..weren’t you?

    I do like the non-standard block color. I was always too lazy (and cheap) to paint the engines I put together for myself or the racecar I used to work on.

    A pair of tips for chasing threads: Be careful not to remove metal while doing it with a tap. And to help prevent that, when replacing things like you head bolts, take one of those and grind a grove or two down it’s length to give the gunk somewhere to go and use that to clean out the gunk. then if there is any slight damage, a tap or chaser can be used to fix the issue.

    I need to get a new set of taps and dies, mine was cheap, and I need to replace a few of the sizes from breakage, so might as well get a better set.

    Reply
    • Kristin Cline

      Thanks JP ;) Whenever anyone tells me that Ethan is a lucky man, I always reply with “I’m a lucky woman.” We’re both lucky to have found each other and quite a good little pair if I do say so myself!

      For chasing threads…do you mean to grind off the threads on an actual old hold bolt and use that to chase out the oil rather than using a tap? I can see that. Taps do take some finesse to use – it’s good to get some practice in before doing a job where it “really counts.” We borrow a friend’s tap and die set when we need to – but otherwise we just buy them seperately as jobs call for them. I know in the long run that’s more expensive, but since we have an awesome hardware store just down the street…it’s pretty convenient to do it that way.

      Reply
      • JP Kalishek

        Yes, I am sorta making a tap from a bolt (I have a bolt box from two other bikes the same as mine so I tend to have spares) except it isn’t going to cut any metal. Take the old bolt and using a thin cut off wheel (or on small bolt, a 3 corner file) cut a flute much like the Tap has, but only one, maybe two depending on the diameter. I also tend to go up the bolt at an angle of about 90 degrees to the threads. On smaller screws, I just file or grind it to look like a self tapping screw.
        Also, if it is just a bit of rust or a small amount of dirt, and pretty dry, I like to put a bit of grease in the slot to hold the dirt and rust … if it is gunk like you were chasing out of the holes it tends to stick on its own.
        Do a good angled cut in a Grade 8 (or the metric equivalent) and it will do minor cutting to damaged threads in aluminum or soft iron. I’ve had taps remove too much metal a few times when it was only one small bit that needed dressing.
        My uncle has an old set of tread chasers made in the 40s I think. They look like taps and dies, but are not as sharp, and coated in copper.

        I bought the tap set I have as I needed a few different ones, but everything I have is metric, and singles for those are fewer and far between. And Honda sometimes uses the same diameter but different thread counts and many times with no rhyme or reason. Like when it’s a 10mm bolt and there isn’t a whole lot of difference between a 1.25 and a 1.5 tpmm held in single shear. The hardware in the next town over (it’s only a 11 mile trip to the nearest one to me) has a decent brand, so I might get one from them and they do have them in singles in case I need one of those I broke or lost.

      • Kristin Cline

        11 miles, that’s a looong trip for me! My hardware store is luckily less than 1 mile away :) Thanks for making me think about different ways to clean threads, that will come in handy in the future!

      • JP Kalishek

        When I lived in the New Orleans area we had a Home Depot and two autoparts places within a mile, and within 11 another, a Lowes, numerous autoparts houses, a few Ace hardwares, a Tru Value or three.
        Now I am in Alvarado, TX on a small horse ranch, and there is a building supply nearby, but they don’t have everything one might need, but we do have two parts places (A PartsPlus and Autozone), and living in the sticks, one gets used to longer trips. Though If I need groceries and what that is only a few miles into town.
        Upsides; my rent is cheap for a place with a garage, I can make a parts run without needing to even close the doors and the noisy neighbors are not inside of hearing most of the time … downsides; I need to mow almost 2 acres, and on rainy days like today the driveway can be a bit slick (almost a quarter miles of driveway)

    • RRay Botts

      hey quick question similar to this subject.
      I took the head off a block and noticed “new moon” valve marks on the pistons. maybe 1/64″ marks. it must have been done cranking with a key because it bent the valve tops outwards slightly. I had the shop redo the head.

      other than a slight increase in combustion volume, is it anything to worry about before I install the head?

      the clearances seem fine.

      also, im trying to clean the block in the vehicle. whats the best way to clean it because I’m definitely not going to get it shop ready clean. just scoth bright pad the buildup enough to rough up the sealing surfaces for the new head gasket?

      it’s a 1.6l 4-cyl 16 valve Daewoo engine. eTech. everything laying flat fortunately.

      Reply
      • JP Kalishek

        Check closely for cracks atop those pistons contacted, but otherwise if it was just a minor tap, ensure the timing of the cam is correct. If the head was shaved at any time, the timing might be a bit off. A fudge to the wrong direction will possibly bring valve to piston contact. I’m not well founded on DaeWoo(/Suzuki/Opel/GM) stuff , so your best bet is to get a Haynes’ or Chilton’s manual for the car or find one online or a support forum with images you can use, and see if there are any little quirks to installing the head on that motor. I know the older versions of that motor had several marks that can confuse things when timing the cam. It’d not surprise me that the twin cam was even more so.

      • JP Kalishek

        Oh, and make sure that you have good head bolts. Make sure you have either reusable head bolts, or if they are single use, get a new set. So used to old stuff, or studs instead of bolts, I forgot that bit.

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