ENGINE BUILDING/ PERFORMANCE RAMBLINGS ( page 1)

When building any motor, the place to start is at the bottom. Most guys are on the hunt for the magic cam,head, or intake manifold and carburetor but the most basic and most often overlooked is the block. Think about it; after all it is where all the action is going on, right? After a thorough cleaning and inspection to make sure it is healthy and useable, if you are going to drag race or use it for some other purpose that only subjects it to short run times, fill it. You do not want to do this on a street or circle track engine as the oil temperature gets high since there is no cooling going on at the bottom of the cylinders. This is not a new idea. It has been around since the fifties ( there was a product back then called tuf-block ). Filling strengthens the cylinder walls extremely. When an engine runs the cylinder walls flex and this prevents that. Less power is transmitted to the cylinder and more is used to turn the crank. Now you may not want to do this if it has some special collector value ( drag racers often race but worship their rare pieces ). We filled them leaving water space at the top for about an inch at the top. On a flathead where the ports are in the block, you might run into a little difficulty around or under the port area. We used a commercially available cable setting grout ( can't remember the name anymore ). It looks like concrete but is WAY stronger with it's own aggregate and metallic material already in it. Yes, it does add weight, but at the same time it is displacing water at eight pounds per gallon.

Next on the agenda, or first if you are not filling the block, would be align honing the main bearing bores. There has always been a lot of argument against this, mostly being " when I tore it down, the crank turned okay ". Well I would certainly hope so after a hundred thousand miles. An engine pretty well clearances itself. But try putting a correct set of bearings right back in it and torquing the caps and see how well it turns ( can you turn it with just your fingers on the crank snout ?). You won't believe the difference in how free the crank turns in a block that has been align honed. It is well worth the price. By the way, the other argument against doing it is mostly about the skill of the machinist doing the job. A common problem is when they remove the couple thousandths material from the parting line of the caps, they get the thrust cap crooked, so when you assemble the engine the thrust cap is in a bind and the crank won't turn.

Decking the block is done after this. For the optimum benefit, measure all the parts: crank stroke, rod length, and compression height of the pistons, and mill the top of the block to give about .035 piston to head clearance ( a good figure for an iron rod motor ). Of course, you have to be careful if there is a lot of material to remove because you don't want to mill away the valve seats. A side benefit of milling the block is getting a good gasket sealing surface.
Boring and honing the cylinders comes next. Measure all the pistons where the manufacturer says ( they aren't all measured in the same place ) and get an average number. They don't differ enough to bother selectively fitting a certain piston to a certain bore. Checking the cylinder wall thickness with a sonic tester is a good idea if you are going for a large overbore ( even if not going way oversize, it's nice to know what you have ). Leaving about .180 on the thrust side of the cylinder ( the right or passenger side ) is plenty adequate. You can get away with a little less if it won't be subjected to any real hard running ( many stock modern engines aren't this thick, for example the 305 Chevies made in the 80's with the one piece rear main bearing seal have only .090 thick cylinder walls ). Relieving the cylinder at the bottom of the bore if/where it runs into the top of the main web, is critical to getting a proper diameter at the bottom when honing ( this isn't a problem on all motors ). The block should be bored leaving .005 or so excess for final honing. Honing with a torque plate is highly recommended if it is available. On our flatheads this probably won't be available, but a creative type could make one for himself ( I really doubt BHJ Products makes one ). You can make one by using a piece of material ( iron or aluminum depending on your application ) using the head gasket as a pattern. The head bolts used during honing should have the same thread depth as you will use on the finished product. This could also be used for doing the valve job on a flathead. The torque plate simulates the stress placed on the block/cylinders when the head is torqued in place. Believe me, they move, especially in the area around the bolts. The same type of head gasket should be used for honing and assembly as the stress varies according to the type of material the gasket is made of. When the honing is done and the plate is removed, the cylinders won't measure correctly anymore because of the distortion being removed so don't panic. The cylinder finish varies according to which rings you will be using. Plain cast iron rings use a pretty rough finish while Moly rings use a finer one ( chrome is just no recommended ). An even finer finish is used on .043 and Dykes ( pressure backed ) rings for racing applications. While honing the machinist can control the taper in the cylinders, and they should be perfectly straight when done ( this is the reason for the relief above the main webs I spoke of earlier ). All the work should be done preferably on a Sunnen CK-10 or the CV-616 as Sunnen has honing down to a fine art.

The valve work can be done either before or after the final hone work. Grinding the seats on a wet bench would be nice, but the sheer bulk of a block prevents that, so it will have to be done the old fashioned way, dry, on the floor. The seats should be ground so they are in the center of the valve face for good heat dissipation on a street motor. seat widths should be about .060 on the intake and .090 on the exhaust seats. On a more performance oriented application they are ground so the o.d. of the seat and valve are the same with a .045 width intake seat and .060 exhaust. This allows you to open up the bowl area a little with the bottom cut. By the way there is nothing fancy about a "3 angle valve job". It's the way it should be done in any case. The width of the seat is controlled by the top and bottom cuts. Lapping should NOT be done. This usually leads to the valves leaking more readily than if they had not been lapped. Any port work should obviously be done before the seats are ground to avoid any damage to the seats from a runaway die grinder. As I mentioned a torque plate could be used on the block when grinding the valve seats to simulate the stress caused by the head bolts near the valves ( they have them for Chevies ).

Now for the rotating/ reciprocating parts. The crank should probably be ground as after so many years of use and abuse it generally won't be round even if it doesn't have a lot of wear. It's also nice to have a nice fresh surface. The journals usually should be ground to middle/ bottom tolerance so bearing clearance won't be too tight ( .0015/.0020 is good for street use while .0025/.0030 is better for performance use ). The weight of some of these pieces can be downright monstrous and could probably easily shed a few pounds by judiciously grinding the counterweights and blending some of the material around the rod throws. All the extra weight is detrimental to actual engine acceleration. The more everything weighs the longer it takes to get moving and of course slow down ( the flywheel effect ). Knife edging the counterweights can also be done to improve windage ( a little more on windage and oil control later ). The rods should of course be straight. Too much emphasis is placed on fancy aftermarket rod bolts. ARP's are nice but in their absence don't sweat it as they probably aren't available, even after cross referencing, for our oldies . The big end of the rod should be reconditioned by honing. A few thousandths material is removed from the parting line ( after the rod bolts have been removed ), then the bolts are reinstalled and torqued properly and the big end is honed on a Sunnen rod hone. Again, as on the main bearing housing bores, you should go for top tolerance for performance ( .0020/ .0025 )and about nominal for street ( .0015/ .0020 ). The best way to set the clearances is to do the machine work first on the mains and rods, torque the bearings in place and measure the i.d. to determine the proper diameter to grind the crank. Polishing the side of the rod beams is optional. A lot of guys like to do it in the name of relieving stress, but any actual benefit other than getting rid of a little weight is up in the air ( they do look good that way ). Center to center length on the rods can be controlled when removing the material from the parting line prior to resizing. A little speed trick for high rpm operation ( and YOUR machinist may laugh at this ) is to hone the big end out of round ( big at the parting line ). This is done by squeezing the rod at the parting line with a pair of welder's vise grips when honing. Just a couple thousandths is good. By the way, the clearance at the parting line with a set of bearings installed is greater than with the length of the rod. When the engine revs, the reciprocating weight ( piston, pin, rings, and small end of the rod )works against the big end of the rod pulling the bore out of round. If it gets out of round far enough, the edge of the parting line of the bearing acts like a wiper on the crank journal removing the oil and POW. This is how most rod bearings are spun. In some cases where losing rod bearings can be a habitual thing, you can even pin the lower half of the bearing to the rod cap like in an aluminum rod. One main concern when resizing the big end though, is getting the bore straight. Many machinists don't have much understanding of this. They just place the rod on the gauge on the rod hone to check the diameter. This only checks the diameter in one place in the bore. You must pull the rod off the gauge slowly and watch to see if the bore is straight and not tapered or barrel shaped. This leads to poor bearing alignment with the crank journal and premature wear of failure.

Balancing everything is highly recommended. Although inlines are inherently smooth, ( they are neutral balanced because of the placement of the rod journals ) it's hard to believe what a difference balancing one makes. With an inline, all you have to do is equalize the weights of the pistons, big ends, and little ends of the rods. The crank is not bobweighted when balancing an inline, so the cost is less than for a V-8. Most serious imbalance problems are usually caused by the flywheel or most often, the pressure plate ( they always have a sticker claiming they are balanced, but that's on their fixture, not your flywheel ). The flywheel and pressure plate should be balanced on the crank for the best result and then marked so they can be reinstalled in the same position.( continued on page 2 )

Regards,
Del




[This message has been edited by DEL (edited 03-05-2002).]