 The finished grooves are about .035" deep and .038" wide so that the .040" diameter wire will be a nice fit. |
After setting up the boring bar and cutting tool I removed enough material to leave me with about .004” to hone. It is not necessary to use the deck plate (torque plate) when boring the block but it will be used for the honing process. The KB Pistons forged slugs call for a .005”-.007” piston to wall clearance for a drag racing application. I am going right to the .007” limit partly due to the filled block not being able to expand as much as a un-filled block and also for a slight reduction in friction at operating temperature. The KB slugs measured in at 4.0360” which means I’m after a finished bore size after final hone of 4.043”. I bored the block to 4.039” and all went well except for one hole which did not completely clean up after boring. It has a “eye brow” that I measured to be about .002” deep right at the top of the cylinder but it should disappear when honing. If I would have bored the block .030” over it would have required a sleeve to fix the eye brow. In the words of Maxwell Smart, “missed it by that much.” Boring was completed and the next step was to machine a very slight chamfer at the top of each newly bored hole so that the piston rings would be able to be installed without catching the edge and breaking. This is done with a simple hand drill and a special cone shaped rubber arbor with a sanding paper cone attached. It doesn’t take much of a taper but it has to have some.
Next up was a mock up of the crank, rod, and piston assembly to check for any clearancing issues with the stroker assembly. I assembled a piston and rod together, no spiral locks at this point, and installed the main bearings in the block. The crank was laid into position and turned carefully to see if the counter-weights were going to hit anything and all was clear on that front. Next I carefully slid the piston assembly into cylinder #1 and installed the rod cap with the bolts just snugged up. Once again turning the crank I got the expected interference problem common to a stroker, the rod bolts were hitting the bottom skirting of the cylinders. I carefully
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First thing was to paint some blue layout die around the oil pump hole in the block. Then I used a oil pump gasket and a scribe to mark out the proper location of the hole by lining up the bolt holes in the block with the holes in the gasket. I opened up the hole a smidge and then contoured a taper shape leading down into the hole. It kind of looks like a funnel. This way the hole in the block will be slightly bigger than the hole in the oil pump and there wont be any “hitting the wall” effect for the oil leaving the pump. Then, using a small carbide bit, I smoothed out any sharp edges and corners in the oil path leading to the filter mount. Next up was a slight enlarging of the main saddle oil feed passages. I used a 11/32” drill bit and carefully drilled thru the passages to where they intersect the main oil galley feed hole that runs the length of the block. That is pretty much the extent of what has to be done to a 302 block oiling system. I also tapped the front oil galley plug holes for a 1/8” pipe plug to replace the pressed in factory types that can potentially dislodge under pressure.
The last step before finish honing is to machine the receiver grooves into the block for the stainless wire that is referred to as “o-ringing” the block. I can machine these grooves with my boring bar but I actually still prefer to do it with a tool I bought a long time ago from Isky called a “Groove-a-Matic.” The pictures show what it looks like and it really works great along with building up your arm muscles. Basically, you set the tool to the desired diameter you wish to cut (approximately 1/8” bigger per side than the bore) and set the depth with old pieces of feeler gauges. The cutting tool is then centered in the bore with the centering fingers of the tool and you turn the cutter in a clockwise direction which allows the tool steel cutting bit to form a groove in the deck surface of the block. Once the groove has been cut deep enough the studs on the top of the centering fingers ride on the block and prevent going any deeper. Incredibly simple tool that works great.
When final assembly rolls around I will demonstrate the installation of the wire and explain some of the benefits of this type of combustion sealing. Well that’s it for now. Next issue we should have some fun. I will finish hone the block and be ready for assembly! I have a whole pile of neat stuff from Comp Cams awaiting a home and rings that need gapped, cam bearings installed, clearances checked, etc. Man, if I’m not careful I might convince some people that building an engine is actually a real job! See ya next issue!
Always remember, there is always hope.
And, when in doubt…DO A WHEELIE!!
Sources
| Ohio Crankshaft www.ohiocrank.com |
Moroso www.moroso.com |
KB Pistons www.kb-silvolite.com |
TCI www.tciauto.com |