Engine blueprinting has become standard
procedure in many performance engine shops. Blueprinting is
an absolute necessity to obtain maximum power and to insure
the longest possible engine life and reliability.
Blueprinting an engine means hand building
an engine with perfectly fit components using maximum recommended
clearances, and minimum recommended volumes. These specifications
should be determined using the engine manufacturer's tolerances
for the engine being built.
All parts must be one hundred percent
clean. The block should be boiled out making certain water
jackets are perfectly clean. All bolt holes should be re-tapped,
cleaned and oiled, as well as their mating bolts. Any surfaces
being refinished should have all holes chamfered, and any
casting burrs or irregularities should be ground away.
The V type block should be align bored
exercising extreme care to maintain perfectly equal deck heights
and keeping the crankshaft parallel to the decks. Any variation
in these areas will result in irregularities in combustion
After align boring, the cylinders should
be bored with the main bearing caps still torqued in place.
The cylinders should be finish honed to their proper size
using a 220-280 grit stone and taking care to obtain a good
cross hatch pattern. After honing the block should be thoroughly
cleaned, taking care to remove all honing grit from the bores
and also from the lower end of the block. Be sure to oil cylinders
Some engine builders paint the inside
crankcase area of the block. This is recommended as a detergent
to carbon or sludge buildup, and also seals the pores of the
iron preventing oil from washing deposits, left in the pores
after cleaning, into the oil. Painting will help insure the
absolute cleanliness necessary for top quality performance
and engine life.
crankshaft must have correct angularity of the rod throws
as well as be perfectly straight. It should be 100% inspected
for cracks and have the journals ground to perfect angular
index. Fillet radii should be held to recommended arc as well
as having oil holes chamfered and bearing surfaces polished.
The oil passages should be cleaned thoroughly with a good
brush. Some builders use fully grooved main bearings or groove
or cross drill the crankshaft main bearing journals. These
procedures are also helpful in insuring longer engine life.
The connecting rods should be carefully
checked for imperfections and Magnafluxed. All rods should
be reworked so they are EXACTLY the same
length from crankshaft centerline to wrist pin centerline.
Performance builders recommend allowing from .002-.003 for
rod stretch at high speeds. Generally the length of the rods
will be controlled by working to the minimum manufacturer's
clearance for piston to deck. Any burrs and irregularities
should be removed from the rods, and always use new rod bolts
and nuts. The rod alignment and side clearance are also critical.
The pistons should be individually
and carefully fit to the respective pins. Chamfering any sharp
edges on the piston reduces possibility of localized hot spots
which cause pre-ignition and/or detonation. Each piston should
be carefully matched for clearance with each bore. Too little
clearance will result in scuffing and too much clearance reduces
the effectiveness of the rings.
The compression rings should each be
placed in the bore and straightened with the top of a piston
to square the ring in the bore. Gaps can then be checked,
with .0035 per inch of bore the minimum allowable gap. Staying
as close to minimum as possible is recommended. Also be sure
to check ring side clearance in piston groove. The maximum
is .006 but .003-.004 is most desirable.
Now that the main reciprocating components
are selected and fit, the engine should be balanced. It is
recommended the balancing be done with all ring, S, pistons,
rods, bearings, crankshaft and also flywheel and crankshaft
dampner and pulley. Some engines
(Ford 427 for example) recommend an
allowance for oil weight in the crankshaft when balancing.
These specs are available from A.E.R.A. or from the manufacturers
of balancing equipment. Additional weight is added to the
bob weights in these cases to compensate for oil weight.
Balancing will provide insurance for
engine durability, and will also help obtain maximum horse-power.
The cylinder head should be disassembled,
cleaned and carefully inspected for cracks. If the surface
is in questionable condition or the head is warped, it should
be resurfaced. If resurfaced all holes and sharp edges should
be carefully chamferred and deburred. Bolt and spark plug
holes should be retapped and cleaned. The valve guides should
then be checked and replaced or repaired as necessary. Remember
to also check valve stems and replace those valves not acceptable.
This is also the time to machine the valve guides if necessary
for the installation of Hastings P.S. seals. The valve job
should be done according to recommendations for the engine.
Make sure valves and seats are not worn so as to sink the
valves too far into head. A valve stem height gauge should
be used to keep all valve stem ends the same height above
the spring seat. All burrs and irregularities should be polished
out of the combustion chamber. After this the chambers should
be checked for volume in cubic centimeters. The chambers should
be enlarged to the volume of the largest chamber. When all
chambers are equalized the desired minimum CC's can then be
reached by milling the heads carefully until the correct volume
In order to check the CC volume of
the chamber a Plexiglas plate, light oil, and a chemical burette
are needed. With the spark plug and valves installed the plate
is placed over the combustion chamber and sealed with a light
coat of lubricant. Using the burette it is then a simple matter
to measure the amount of liquid needed to fill the combustion
Valve springs should be checked for
tension and installed height, and replaced or shimmed as needed.
If the head has individual rocker arms on studs the stud should
be threaded or pinned in its boss.
In engine assembly be very sure to
follow recommended procedures for bearing and ring installation.
Torque main bearing and rod bolts slowly and in progressive
steps to the proper tension. Use protectors on the rod bolts
to prevent crankshaft scars, and keep rotating the engine
as each step in the installation of the crankshaft and pistons
is taken. This will enable spotting the exact location of
any misfit or mismatched parts.The use of Plastigage here
will serve as a double check on clearances.
Many performance engine builders are
using support "girdles" for the lower end of the
block. These girdles are readily available for most popular
engines and are a very important aid in strengthening the
engines lower end. The girdle supports the center mains and
also serves to stiffen the engine block.
When installing the timing gears and
chain the use of a camshaft degree wheel will insure perfect
crankshaft to camshaft timing.
Offset keys or cam gear bushings are
available to allow accurate adjustment of possible timing
After installing the heads, making
sure they are torqued to the proper specifications, the valve
train should be completed and checked. In cases where higher
lift camshafts have been installed it is possible to have
the valve spring bottom out, or the canoe type rocker be interfered
with by its mounting stud. Where this happens the spring must
be changed, and the rocker arm relieved to provide the necessary
The complete engine build must be performed
as painstakingly and accurately as possible. Always keep in
mind that dirt is the greatest enemy of engine life. Perform
your engine build under the most antiseptic conditions possible.
The blueprinted engine is the utmost in performance and durability
possible, and its success is a real testimony to the expertise
of the engine builder.
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