Chevy Big Blocks. David Vizard

Chevy Big Blocks

Chevy Big Blocks - David Vizard

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hone finish might be just the ticket, but achieving it may not be within the realm of practicality in a local machine shop. In any event, I take a more practical but still conservative approach, which I feel is about the middle ground.

Fig. 1.7

       Fig. 1.7. This is a top-quality bore finish that works just fine, but can be improved upon if you are willing to work at it.

Fig. 1.8

       Fig. 1.8. Here is the bore finish on one of my engines. Note that the hone pattern is visually indiscernible, and the overall finish is nearly mirror-like.

      I suggest you use a machine shop that works on race engines as a major part of its business. That means they have experience in this area. If the shop you are using does race engines regularly, they may well have an effective standard procedure. A number of viable routes can lead to an effective bore finish.

      If you don’t want to go with what your machine shop is offering, here is what I do: I call for a bore finish smoother than that used for a typical production engine. This usually entails taking out the last half thousandth of an inch slowly to avoid overheating the bore and overloading the stones. This final operation requires a set of 400-grit stones, rather than finishing with the 320-grit ones used for a production rebuild. After sizing is achieved, the bores should then be final finished with a brush hone to smooth out the micro scarring that is inherent with any abrasive metal removal process.

Fig. 1.9

       Fig. 1.9. The Total Seal dry powder ring break-in lube has shown good results on the dozen or so engines on which I have used it. It is inexpensive and I recommend it for any budget-oriented build.

       Final Finish

       The following is the final finish procedure that I use, but I should also tell you that it is frowned on by some and embraced by others. Some of the tech guys at Sunnen, the company that makes the honing machines, agree this is one viable route to go.

       After the block is back from machining, spray Gunk engine cleaner down one bore at a time and use a green Scotch-Brite kitchen pad to rub the bore surface in an up-and-down motion. This process only needs to be done for a couple of minutes or so. To test the finish, I wipe the bore clean and see if a finger nail runs up and down the bore with a very smooth feel. You can easily tell the difference by checking a bore that is “as honed” compared with the one you are working on. It usually takes about an hour to prep 8 bores like this and maybe another 30 minutes to wash and dry them. Cleaning the bores in this manner processes the finish at a micro level in the direction of the piston/ring motion.

       To make full use of this friction reducing process you also need to prep the rings in the manner I describe in Chapter 2, Pistons, Connecting Rods and Crankshafts.

       After a good brush hone finish from the machine shop, you can apply the above final finishing step so you smooth off any micro raggedness at the tips of any pinnacles, which might still be sharper than you would want.

       With the bores prepped, a long break-in, although still advisable, is not necessary. I cannot definitively say how much power this produces, but I can tell you that I have used this technique on engines that have finished first in every race in the process of winning a championship.

       After “Scotch-Briting,” the bores should be repeatedly washed, first with detergent and hot water, then with lacquer thinner. Be sure you have a good air line because after the water wash the bores will rust in seconds. Also have some WD-40 ready.

       The lacquer-thinner wash continues until a white paper towel wiped over the bore remains totally white.

       As a last check, apply some Total Seal dry powder break-in lube to the bores. If it turns green when it’s rubbed on the bores’ surface, the bores are not clean enough, so start again and reclean them until they are absolutely clean.

      Bore Finish and Break-In

      Regardless of your bore finish specification be very aware that the break-in procedure is important to get the best output and life from your big-block. Over the years I have tried many break-in procedures and felt that they were less than optimal. This led me to develop my own break-in lube and procedure. I did this in conjunction with Oil Extreme. You should note what I have to say about this in Chapter 2, Pistons, Rods and Cranks.

      Following my Oil Extreme–based break-in regimen is worth about 7 to 10 hp on a typical 750-horse engine and as much as 12 or more on one of those 1,000-hp-plus builds. This extra power comes with a longer bore/ring life.

      There are quite a few things you should know about the lubrication system in your big-block. You have probably heard of “mains priority oiling” and wondered exactly what it means. If you follow the oil routing from the oil pump, on stock two-piece-seal engine blocks, the camshaft bearings are fed first and from there, the oil is routed to the mains. On one-piece-seal Gen V/VI and aftermarket blocks, the preferable discharge route is where the oil pump feeds the mains first and then the cam bearings.

      Although the lubrication system is pretty good on all big-blocks (and better on the later ones), you can perform modifications to improve the system as a whole. The importance of the lubrication system, both in terms of power and reliability, is covered in detail in Chapter 3, Lubrication Systems. Be sure you read it before doing anything to your own block!

      Also in connection with lubrication read what is said about timing sets, thrust bearings, and cam buttons in Chapter 10, Valvetrain Optimization.

      If the budget is so tight you cannot cover the cost of new ARP bolts, be sure you polish the threads of the ones you have with a wire brush in a drill gun. Only when the threads are very smooth do you achieve the full clamping loads, so don’t shortchange the build on this account.

Fig. 1.10
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