This information has been supplied to assist in keeping engine repair costs to sensible levels. The information below is all the more important since AVGAS was replaced with Premium Unleaded Petrol!
TECHNICAL NEWSLETTER ISSUED WITH ALL PURCHASES OF NEW OR FRESHENED-UP HQ RACE ENGINES. 01/2007
This class of racing is based on an engine designed back in the 1950’s. This was the time when the local police shop drove push bikes to the local pub to catch the SP Bookies.
The Red 202 is old in terms of engineering design. It has done a fantastic job in it’s original form where one hundred thousand kilometers was achievable with sensible maintenance and driving.
Then the motor sport got hold of it and produced the CAMS specification that the HQ class now enjoys. The engine has problems at the top end of this class and it will help you, the owner, and us the rebuilder, to acknowledge those areas of the engine’s design that either fail or have serious limitations when pushed at the race end of specs.
By the regular exposure to those engines that we, and others have built, that come through our shop, it will help your driver and your sponsors ( if you are fortunate ) to study what we regularly see.
Engine tuning problems:
To extract the maximum power and life out of one of our engines your team has to treat coolant system heat as their No. 1 problem.
Heat comes from the basic physics where the heat from combustion goes 1/3rd to the radiator and lubrication systems and then away from the engine via conduction and radiation to atmosphere; another 1/3rd goes out via the exhaust system in the form of incomplete burnt gases, and the remaining 1/3rd pushes the piston down. (Approximately)
Your team needs to devote some effort towards keeping temperatures DOWN. Be innovative. (Within the rules.) Keep the intake temperature down. Breath cool air. Your cheapest power. Go big on radiator capacity. ONLY use the genuine water pump to have the cast impeller. And CONTROL combustion……….. What does this mean?
The combustion characteristics and the engine performance of the 202 engine is influenced by tuning in the following ways.
The engine you have received has had very considerable dyno and track time to where the top end of the HQ Race engines now produce more power per cubic inch than the Formula Ford class of race engine. Many variables come into play.
The engine designer of the 202 expected fuel to be leaded petrol, with a particular burn rate, after ignition, that coincided with where the piston would be on it’s way up the bore then over the top going down and the pressure of this burn (combustion) would ideally be around some 800 PSI most of the time. Not higher.
But during development of the after-market head gasket, in the 1960’s, dyno room tests showed how a faulty ignition setting produced enough pressure within the combustion chamber to lift the head off the head gasket. Pressures exceeded 2000 PSI.
To demonstrate this, a feeler gauge of 0.002” was assembled between the head surface and the head gasket and the distributor was moved to beyond the correct advance during the dyno load and the feeler gauge could be pulled out of the assembly as abnormal pressures (detonation) occurred.
This is detonation and is actually an explosion rather than a combustion process.
The factors that influence this serious problem are:
Temperature within the combustion chamber: Keep the coolant system at 100% condition. Don’t run on the lean side of tune where more power often exists but which will kill the engine the moment other factors go against controlled combustion. For example, following another competitor in their draught; perhaps a very hot day.
Now that Premium Unleaded Petrol is the fuel specified, know that variations exist. Fuel can become aged. Only purchase fuel from high volume sales outlets. Dispose of the tank’s fuel after the race weekend and freshen up JUST prior to the next dyno run or race meeting.
Check your harmonic balancer TDC to confirm that the outer rim, and therefore your datum, for setting ignition advance, has not slipped on the vibration dampener rubber.
Establish your tune specifications at a chassis dyno and RECORD them.
Check your ignition points setting before EVERY race. They close up due to wear and will change the ignition setting.
Premium Unleaded Petrol has been a challenge for the HQ class. Your engine has been supplied with a distributor specifically made for THIS ENGINE DESIGN. The curve is not like that used with AVGAS.
Start off at 8 degrees before TDC. Then move up or down a degree at a time until power peaks without detonation. Reconfirm air/fuel as you go. Then back off a degree for safety.
It is highly unlikely that total advance will exceed 34 degrees; more probable that the setting will be below 30 degrees total.
Make sure that your team boss allocates responsibilities for all track-side duties to individuals BY NAME and enjoy the improved results this brings. Run a log book and record the dyno tune settings. Do not rely on memory.
Miss any of these team maintenance duties and we will find some or all of the following:
Burnt oil stains under piston heads;
Broken piston ring lands;
Loose main bearing caps;
Loose bearing shells in the con rods;
Blown head gasket;
Valve seizures at the port end of the exhaust valve stem;
Vertical cracking between core plugs down the manifold side of the block;
And definitely a slower engine than what you paid for…..
Then we have the base design problems that are fine for the original purpose that the engine was designed for. They don’t give problems at normal revs and power output.
But when we introduce 170 + BHP at the flywheel and 7000 RPM, we really should not be critical of the engine designers when premature failures occur as follows:
The timing gears have been upgraded from fibre to steel helicals and fail after a grueling 3000 race kilometers at the top end of the field. A crack will develop around the hub. Sounds like a sharp tinkling noise at the front just before the timing cover sheds alloy into the crankshaft bearings from contact by the broken cam gear.
The lubrication of this gear set is contrary to logic because the oil spray jet feeds from the block at the wrong side of the gears. The oil is actually thrown off at high revs before it can lubricate the contact point of teeth engagement. Consequently, crankshaft bearings receive metal fragment s from the gear set as the load side of the gear teeth break up. This is more pronounced with engines using the cheaper alloy cam gear. ( not in our spec)
Valve collets and valve stem grooves show wear after running at valve bounce revs. This is a constraint of the CAMS rules where the engine can only run a single valve spring. The main exposure for the driver to acknowledge is when second gear is over used for braking. Dropping back to second will mechanically drive the engine up into the 7000 RPM range and definitely into valve bounce territory.
But valve bounce goes far beyond collet damage. High speed photography exists that shows a valve train before and during valve bounce. At 4000 RPM all components of the train follow one another as the designer intended: The cam follower follows the cam shaft profile, then the push rod moves with it up to the valve rocker and onto the valve tip and then the valve opens and closes in harmony as the designer intended.
But at 7000 RPM, all component parts of the valve train leave their mating component and bounce all over the place. The cam follower initially leaves the camshaft surface only to then catch up again and smash into the cam lobe like a steam hammer. The push rod reacts in the same manner and floats between the cam follower at one end and the rocker at the other. The valve spring is something else. It starts to vibrate. It actually opens AND closes several times within the one camshaft opening. The valve spring retainer and valve collets actually float clear of their contacting faces and of course the valve is bouncing on and off the valve seat waiting for the rest of the moving parts to catch up.
Naturally, the camshaft has lost all control over the engine’s performance and power is clearly lost during valve bounce.
Drivers be aware.
Part of the team checks has to be to investigate power losses between races. Go back to the dyno and test. If power is lost at the top end of the revs, don’t immediately pull the engine. Confirm that compression is even in all cylinders (see below) that all other basics are as they should be, then remove a few valve springs, tie the valve stem secure and bring the springs in for us to test.
Cranking speed greatly affects the compression gauge reading. Don’t panic if a slow starter motor shows 220 lbs when you expect 290 lbs. Look for the even readings and crankcase blow-by to indicate engine condition.
New bolts are no longer available. The old steel is old design. They are 7/16ths UNC which, by today’s standard, is old technology. Please do not introduce new technology methods of head bolt tensioning back on to these old technology bolts. Our recommended head retensioning method is to back each bolt off, and then pull it STRAIGHT UP TO 75 LBS FT. one bolt at a time. With a tension wrench that has been checked, of course.
Modern head bolts are NOT made with course screw cut UNC threads that can create serious bolt stretch, or necking, at the top of the thread on the shaft of the bolt. Modern bolts are more often fine pitch cold rolled threads with a bolt shaft diameter smaller than the actual thread diameter to spread the loading along the length of the bolt to reduce the effect of necking. Then, either the torque to yield or stepped- tensioning methods are used with safety and with good effect.
IF YOU APPLY TORQUE TO YIELD METHODS, OR STEPPED TORQUING, TO OLD BOLT DESIGNS, EXPECT TO PULL THREADS OUT OF THE BLOCK.
Or put in another way, should the course UNC bolt be tensioned up to say, 65 lbs ft as part of a stepped-tensioning method, and then to the full 75 lbs ft, the bolt head and the main shaft of the bolt will rotate but the lower threaded portion of the bolt will not rotate in the same manner. Instead, only the upper section of the thread will move, together with a couple of threads in the top of the block. In effect, the bolt twists and starts to shear at the upper and smallest diameter of the bolt right at the end of the screw cut thread. If you are lucky, the bolt will hold; if not, the damaged bolt thread will pull the block thread out like a zipper. Either way, you now have a stretched and damaged bolt that will lead to gasket failure. The mechanics of this is explained by understanding that fine threads need far less torque to start the bolt moving than does a course thread. It is called inertia.
Use plain water. Coolant additives (glycol) can penetrate gasket faces under race conditions and lead to gasket failure. In the time it takes to rust out a block, the engine will have a few seasons behind it. As for the boiling temperature being higher with glycol? Well, why on earth are you running a race engine so hot anyway? Cool is power. Fix the coolant system. Fix the tune. Is the fuel fresh and of the right quality? Has the ignition system developed a fault? Run your engine cool
If you are running an aluminium core, take the manufacturer’s technical advice in looking after it. Should corrosion start inside the core, replace the core. Corrosion is a very effective insulator and that is not what you engine needs. It needs a core with maximum heat transfer to atmosphere. Note that plain water is the preferred coolant by senior teams and that they store their spare radiators full; not empty….A used radiator will corrode if left empty.
We supply a new radiator filter with every new or freshened up engine. This filter will catch the material falling away from the internal casting surface (water side) of the 50 year old engine block even after we have done our best to clean it. These particles will mainly be corrosion flakes and casting or foundry sand that dislodges as the engine goes through a bit of casting movement when pushing out the power during test or race conditions. If these larger particles lodge within the radiator core, expect engine overheating, loss of power and even a blown engine. Maintain this important filter by cleaning it out as required.
Our engine design uses the graphite head gasket part No. GSAG390D or AG390GT. Other brands have a thinner thickness and will increase the compression ratio beyond our specification and this can lead to detonation and serious engine damage. Equivalents do not exist.
Teams are free to play with different camshaft positions and it is acknowledged that only the team has all of the variables, involved in this choice, under their control. We will build it to your preferred cam position if so ordered. But no single camshaft position will allow the engine to be at it’s optimum for all tracks around Australia. Given that all other factors controlling track lap times are already optimized, by all means play with the cam position. But first get the basics right. Our build specification has the camshaft sealed at the oil pump and the crankshaft nose ground to facilitate frequent cam position changes if the team has every thing else working right. We suggest caution unless the team has the necessary equipment to set the camshaft position accurately and on board instrumentation to then retune at the track when conditions require it.