We encourage teams to build their own engines for many reasons. You can save money, have fun doing the build yourself, and also control what you have. We will offer some important tips that professional engine builders have known for some time that can help make that engine build a success. First we have to teardown our old engine.
When we want to learn all of the important details that go into any operation, we should listen to someone who has done it a hundred times before so we can know more about how things can, and often do, go wrong. Here are a few tips that may help you succeed when you build your own engine.
This series is not intended to be a complete engine building guide. There are many great articles in CT that explain in great detail how to do all of the operations involved in rebuilding a race motor. What we offer here are some of the more simple things we can overlook that can affect, not only the amount of useable horsepower we will have, but how long our engines will live.
Most, if not all, of the tips and procedures we talk about are the result of problems that have occurred and solutions that have been worked out by numerous expert engine builders and tuners. Some of these you may recognize and some will be new to you. If you discover just one tip that saves your engine, the time spent reading this collection will be well worth the effort. Let’s get started.
Most often we begin our engine building experience by tearing down a motor. This might be the one we built and ran last season or one we purchased used. No matter which, we need to pay attention as we disassemble the motor. There are clues as to possible pre-existing problems that, if we are attentive, we can locate and fix before investing lots of money in new parts.
The rod and main bearings are an area where we can see potential problems associated with restricted oil flow, binding, or improper clearances. Aside from a spun bearing or the obvious signs of galling or burning of the bearing surface, we should look further if one or more bearings is a different color than the others. This may be an indication of restricted, not blocked, oil flow. One or more bearings may be running hotter than the rest and failure is imminent.
When we detect a problem like this, we should take extra time to inspect and clean all oil passages. Other areas to be observant are the felt torque on all bolts that we remove. If one or more bolts are already loose or take less effort than the others, the threads may be stressed in the block or warping of the block or head may have occurred from overheating at one time or another. Where we might have thought the block or head was OK as is, we may now consider having it surface milled to make sure it is a truly flat surface.
This step is fairly obvious to most engine guys, but always mark the rods, caps and pistons as to the original location as they come out of the engine if you intend to reuse them. You can stamp them by number or use an age old method for those who don’t own a number stamp kit. Use a punch and punch a series of dents to represent the number for the rod/piston combination, end cap that goes with those as well as the main bearing caps. One dent for “1,” two dents for “2,” and so on.
Block and Head Preparation
Prior to assembly, we will want to have the block and heads cleaned by acid dipping or other means to remove all of the old paint, sealants, and oil deposits that remain. Now is the time to think about what you will need as far as machine work before assembling the motor.
A limited amount of machine work may improve your chances of success with this motor. Usually, the shop where you take your motor to get it acid dipped is also the machine shop that can mill the block and heads, align bore the block and re-cut those valve seats for you. Price those jobs out and see what you can afford. The areas of valve seats and alignment are well worth the cost and effort.
If you have several bolt holes that show worn threads, make sure to have them repaired by someone who knows how to do that. Now is the time to pay attention to those areas, not just before we are to assemble the motor.
Request that the shop not heavily oil the block after the work is done. This will only cause you to have to thoroughly wash the block to remove all of the oil. Once the block is back from the machine shop, a light washing is always a good idea to remove any particles left over from the machining process, but you shouldn’t have to scrub hard if the block has not been oiled. Don’t let a few small patches of surface rust bother you. This can easily be removed by lightly sanding with a very fine grit paper.
Go through all those oil passages and make sure all of them are free of sludge and grit. You can lightly oil the block with WD-40 or equivalent, to prevent rusting until you can assemble the parts.
New parts are often coated with a heavy oil to prevent rusting. This protective covering has to be removed. Wash all new parts in a solvent that will dissolve the protective coating. Lightly coat the parts with a spray lubricant such as WD-40 or equivalent. Never use silicone lubricant as these contain water and will cause rust to form.
An area of concern is with the pushrods in your valvetrain. These units are coated with oil before they are packed. The rods are then packed lying on their sides and the oil inside the rod lies on one side of the rod and gels. If this oil is not removed, the rod will exhibit strange characteristics when run at high rpm due to the greater weight at one side of the rod. Uneven heating of the rod can occur also due to the residue oil and this can cause the rod to bend. Even a small amount of rod displacement can cause unwanted valvetrain harmonic vibrations that inhibit the valvespring function.
One of the most important things you can do to ensure the success of your build is to make sure you communicate the correct information to your parts supplier. Use a lot of detail when telling them what you need in parts. Nothing slows down an engine build like getting the wrong parts and them having to wait for the new parts to arrive.
Tell the supplier exactly how you will use this motor. A valvetrain kit intended for a 600-plus-horsepower motor that will turn 8,000 rpm is no good for a Limited Late Model motor that will produce less than 400 hp and turn no more than 6,800 rpm. The harmonics will be all wrong when using the high rpm components in a lower rpm motor. The high rpm designed valvesprings will not live long at the lower rpm.
Measure your old pushrods to make sure the new ones that come with the cam kit will fit properly for the optimum valve geometry. This is extremely important to help provide the best flow at high rpm. If the pushrods you install are too short or too long, the geometry, or angle of the rods and valves to the rocker arms will be all wrong. This affects the timing of the opening of the valves as well as the amount of lift of the valve. Improper timing and reduced lift equals less horsepower for all of your effort.
Preparing the Parts
The rods, pistons, intake manifold, cam, block, and other engine components need to be deburred and thoroughly inspected before assembly. This includes removing all casting marks and rough edges left over from the machining processes. This step takes considerable time and effort, but can’t be overlooked if you intend for your motor to live a long and happy life. Rough edges on highly stressed parts are the exact areas where cracks will form. Once these edges have been removed, there will be much less chance that a rod or piston will fail.
The sides of the cam lobes are often left rough and jagged after the cam has been ground. You must take the time to deburr and smooth these edges so that when installing the cam you will not gall the cam bearings. Every hole where a piston pin, crankshaft, or piston will fit must be inspected and deburred where necessary. This means that the entire block must be gone over and worked on.
All new parts must be inspected for defects, proper fit and suitability for your application. We often see where the parts supplier makes honest mistakes or misread what your needs are. The quicker you inspect the parts upon arrival, the sooner you can return them for the right part. Don’t assume that all of the parts you are shipped are exactly what you ordered.