Click to Print

Technical Advices > The Cylinder Block

2.1 - Cylinder Block Preparation

Caution: Racing is like any other hobby, if you want to be good at it you must spend time at it. The same goes for engine building. You cannot read too much, you cannot listen to much, but eventually you will have to get down to brass tacks and put that motor together. A good friend of mine who builds a lot of small block Chevrolets put it quite well when he said, "The Cheapest way to Build a Really Good Motor is to do it Right the First Time". The recommendations that I give below are just that, recommendations. There is no express or implied guarantee of performance.

Now it has to be said, that it would be really neat to just wave a magic wand and end up with that 1000 cc killer motor you always wanted, but that is simply not possible. Even more to the point, while it is possible to build such a motor, unless you are doing all-out racing it may be better to try for something more conservative. Now that I have gotten my reservations out of the way, I am hopeful of working through a complete engine buildup for an all-out racing motor. Along the way I will suggest alternatives for something more conservative as well.


Bottom end of motor that went to Europe in 2001

Note: You should recognize some of the components. This is the bottom end of the motor that is currently in the car in Europe. As you read on you will see that we have changed our mind as to what the preferred way of doing this is. This motor incorporated prepared 850 connecting rods. The current motors have Scuderia Topolino rods, with special ARP2000 connecting rod bolts . We are continuing to use Abarth billet crankshafts, as long as they last and/or can be found.

2.2 - Block Preparation

I cannot stress strongly enough how important this first step is. The largest single item is the block. Unless you want to build an engine that is historically correct for an Abarth 750 GT, or the like, I would stay away from using a 600 block. For 1000cc motors these blocks require a great deal of work. There are two worthwhile alternatives, either an 850/OT1000 block or one of the 903/A112-1050 blocks. (For those wanting a real shortcut for a street motor, just buy a 70 hp A112 1050 motor and put it in your 600 and it will transform your car. This is still not a straight swap, but the work is quite easily done. The clutch end of the cranshaft will have to be drilled for a bronze input shaft bushing. This is not a hand drill operation and will require the removal of the crankshaft from the block. You can also start off this way and then if you want more performance, upgrade for more horsepower later.)


Two new blocks being prepared

The 817/843/OT1000 family of blocks are what I refer to as the "short deck" variety of block, whereas the 903 and 1050 are "long deck" blocks. The difference being that the long deck blocks are about 4-5 millimeters taller. Other than this the blocks a dimensionally similar, with the exception of the main bearing bore. The 817/843/903 use a smaller diameter main bearing bore, as compared to the 982 and 1050 blocks.

Before proceeding any further, clean the block in a parts washer and then have the block thoroughly magnafluxed for cracks. 1050 blocks are particularly prone to cracks in the front surface of the block, between the front main bearing and front cam bearing bores, and all blocks can suffer block cracks around the center main bearing web. Doing this now will save a great deal of wasted work. If the block is at all doubtful, find another one.

Check how far the block has already been bored . I consider the maximum safe cylinder diameter is 66.4mm or so for all but the A112a2000 (A112 70HP) block, which can be bored to 68.00mm. If the block is already to 1mm over standard, consider a different block. There are many blocks out there that are still standard, and these provide a good bases for development.

Note: US machine shops will probably measure blocks in thousands of an inch, so a good formula is that 1mm equals very close to .040 inch. Therefore, a .25mm larger bore is the same as .010 thousands of an inch.

Next determine if the deck of the block has been decked and is flat. If the top of the block has been previously machined, you may find that a standard connecting rod/piston combination will stick out above the block slightly. This is not the end of the world, but just means more work. If it is not flat, but at close to standard height, do not worry about it for now. The standard height for a 817/843/1000OT block is approx. 172mm, whereas a 903/965/A112A1 or A112A200 block will be around 177.8mm in height.

Now determine if the deck is parallel to the crankshaft bearing bores, the cylinders are at 90 degrees to the top of the block, and the front and rear block surfaces are precisely at 90 degree to the crankshaft bore. It is important that all of these dimensions are exact if we are to extract the maximum amount of horsepower out of the engine. If any of these dimensions are out, bring them back into specification. If the ends of the block are not square, and are out by more than .005 thousands of an inch, find another block.

Note: Do not assume that the factory manufactured the block correctly. Remember that this was a production motor and the tolerances for a race prepared motor are much tighter.

Next, knock out all of the freeze plugs (sometimes known as welsh plugs) from the water jackets and the one at the end of the camshaft gallery. These may look like they are OK from the outside, but as they are in contact with the cooling water on the inside, you may find considerable erosion. Put in new ones. You will also find small plugs at the end of the oil galleries and these should also be removed. It is likely that you will want the block hot-dipped, unless you do not plan on replacing the camshaft bearings. These will just disappear in the hot tank process. The oil galley plugs must be removed for cleaning no matter what. Further, remove all bolts, studs etc. so that the machine shop gets a totally naked block, as this means you will get it back with all of the threaded holes thoroughly cleaned. This will save the machine shop time and you money.



Two different doweling methods.

Have the machine shop check the block for main bearing saddle alignment and dimension, otherwise you may never get a good bearing fit. The 1000OT and A112 blocks register the main caps with either dowel pins or hollow dowels. I think doweling is a really good idea.

Do not automatically assume that a block needs to be line-honed, but if it appears that the block does, then this is a warning flag that it has had a rough life. Have another good look at this block before you go further. Once this is done, have the machine shop double check the ends of the block for squareness.

The next step is to examine and clean every thread in the block. This means running a tap, or better yet a “thread chaser” down each threaded hole and then blowing it out so that all of the debris is removed. Only then will you be absolutely sure that the fastener will properly torque to the required specification. I have found that many older blocks require some threads to be repaired with helicoils. I no longer take any chances with the head bold threads, if they look at all suspect, they get a helicoil inserted. Inserting helicoils is a precision job. DO NOT attempt to do this with a hand drill, as the threads will not be straight. Later on in this article I will talk about head bolts versus head studs, and you will understand exactly why this is so important.

Your machine shop should also be able to pressure test the block for you. You will have to make sure that all of the freeze plugs and oil galley plugs have been replaced. If the block passes the water and oil pressure tests, then you can proceed.

Next, the machine shop will need the pistons that you plan to use. Follow the piston manufacturer's instructions for piston fit, but a good rule of thumb is .001-.0015 (0.025-0.038mm) for each inch (25mm) of piston diameter. Thus a 65mm piston would have about .0025-.003 (0.063-0.076mm) of piston to cylinder wall clearance. (Max. recommended clearance .0035" [0.090mm]) Any honing of the block should be done with a deck plate bolted in place and torqued to the required head bolt torque. Cylinders will distort slightly and using such a plate insures that when the head is torqued down the bores will be round. Generally, bores should not have more than .0005 taper to them. To get accurate, straight cylinder bores requires the use of a Sunnen honing machine, or similar equipment. I do not recommend hand honing, except as a last resort and then only if you are well experienced at doing so. All too often, with hand honing, the hone spends more time in the center of the stroke and you end up with a "barrel" shaped cylinder. This makes ring seating very difficult and is very hard on piston ring lands, as the rings move horizontally during each piston stroke, very quickly wearing out the piston ring land and generating unwanted friction and heat.

Note: The dimension printed on the piston box usually denote the bore size required in the block for the enclosed pistons to meet specification. I say USUALLY. Do not leave this to chance. Whenever I have a block bored/honed, I ALWAYS have the pistons available for the machinist, so that he can personally check the size and fit.

Next, you will need to temporarily assemble certain components into the block to double check critical dimension. After making sure that the block is clean and dry install the crankshaft with the three main bearings and thrust bearings in the block. Install these dry, as at this point we are not assembling the motor yet, only checking dimensions. Lay the crankshaft in the block. Then place a dial indicator against one of the counterweights of the crankshaft and test for thrust bearing end play. I like an end play reading around 0.003 0.005 inch (0.076-0.127mm). Even clearance up to 0.010 inch (0.245mm) is probably OK, but you will have to double check other clearances more carefully.

2.3 - Lubrication System

The standard configuration for Fiat blocks is an oil pump within a wet sump, attached to the bottom of the block. This oil pump feeds oil to the various components of the block (and head which will be discussed later).

One problem associated with 817/843 and some early 903 blocks is the implementation of a partial oil filtration system, using a centrifugal filter in the front pulley. This implementation also did not have a direct oil supply to the center main bearing. Abarth realized this problem and in all of the Abarth derived blocks this was changed. I also recommend the following:

First, ANY orifices that have sharp edges on them should be radiused. Normally after oil is picked up by the pump, it goes to the pressure relief valve in the block. This area needs some serious cleaning up and blending to make sure that we get good oil flow. ( 1972 or later 903/A112 engines have the revised oiling system already and also have a filter mounted to the block.) For a race motor I recommend that you have a new crankshaft pulley machined from steel or aluminum. The pressed metal ones that are silver soldered have been known to come apart.

Follow the instructions below for reverse engine oil flow and pressurized center main bearing on earlier 843/OT1000 blocks:



This is the 3/16th hole going to the bottom of the main cap hole from the center main.



AN-12 Fitting installed in bypass hole
Be careful when installing. Use Teflon tape and do not over tighten.

1. Drill a 0.187 inch (4.5mm) diameter hole in the center main bearing saddle (use a center main bearing with the requisite hole to locate the position) on an angle to intersect with the bottom of the left main cap bolt hole. You do not have to drill very far, perhaps just a quarter of an inch or so.

2. Remove and discard the oil galley plug from the outside of the block. (You should have already done so by now anyway for cleaning purposes) and use a long, straight 0.187 inch (4.5mm) drill bit, to drill an oil passage to intersect with the previously drilled hole. (I recommend that you do this on a vertical mill) If you allow the drill to go off-center, then you will get to start over with another block.( In my engines, as I use the rear-most boss on the oil galley for return pressurized oil supply, I tap this center entry in the oil galley for a 1/8th pipe fitting for an electric oil pressure sender.)

3. Carefully enlarge the outer hole at the oil gallery and tap for a fitting for the oil pressure feed line for the block. Remember this is cast iron and it does crack. A "-10" Aeroquip fitting with a pipe fitting on the other end is fine. Make sure that you install this fitting with a sealer or Teflon tape. This is where oil goes in to pressurize the entire engine.

4. Next turn the block upside down and find the hole where the oil pump outputs oil. Enlarge this hole for its full depth to 10mm. (The same goes for the gasket).

5. Next to this hole is another hole (bypass return hole) that must be permanently blocked.

6. Fabricate a main cap blanking plate for the #1 main cap and install with gasket.

7. If the crankshaft you plan to use came from a motor with a centrifugal oil filter, plug the hole in the snout of the crankshaft. Again, I recommend drilling and tapping for a Allen head plug, installed with loctite.

8. You will have already removed the pressure bypass valve in the side of the block. Inspect the oil passage and relieve/open up as required for better oil flow. Remember that this is going to be the output orifice for the oil pump.

9. Make fitting to go in place of the pressure bypass valve. Again, this will have an AN -10 or AN -12 Aeroquip fitting on one side and and a metric (20x1.5mm) thread with a flat face for an annealed copper or aluminum washer on the other side. Scuderia Topolino has available a kit to do this modification.

The oil now is picked up by the pump and exits the block via the special fitting in the bypass orifice in the block.

 

 

2.4 - Oils and Additives

Recent changes in oil formulations have proven to be troublesome for older vehicle is general, and for cars with flat tappet engines in particular. Up until a year or so ago, almost all engine oils had small amounts of zinc and phosphorous as part of their oil chemistry. The typical amount would have been 1200 ppm (parts per million). Manufacturers have asked that the level of phosphorous be reduced, as it has a negative effect on the longevity of catalytic converters. Oil companies have responded by cutting these additives by 75%, as they are also expensive ingredients in oil-formulation chemistry.

Both phosphorous and zinc are specifically indicated friction modifiers, particularly applicable to "sliding interfaces". These would include the following interface junctions:

  • Cam lobe/lifter,
  • push rod/lifter,
  • push rod/adjuster,
  • rocker arm/rocker shaft,
  • rocker tip/valve tip.

Most engine oils have had the level of these vital additives reduced to 400 ppm. The exceptions to this rule are as follows:

Manufacturer

Oil Type

Synthetic/Organic

Weight

Phos. PPM

Zink PPM


Castrol

Syntec

Synthetic

5W-40

1000ppm


Vehicle

Castrol

Syntec Classic

Synthetic

20W-50

1200ppm


Vehicle

Castrol

TWS Motorsport

Synthetic

10W-60

1000ppm


Vehicle

Castrol

BMW Long-Life

Synthetic

5W-30

995ppm


Vehicle

Castrol

Power RS GPS

Synthetic

10W-30 10W-40 20W-50

1000ppm


Motorcycle

Castrol

Power RS R4

Synthetic

5W-40 10W-50

1200ppm


Motorcycle

Brad Penn Oils

Formerly Kendall

Synthetic

Various

860ppm


Vehicle

Swepco

306






Royal Purple

Max Cycle

Synthetic

20W-50

1200ppm


Motorcycle

Amsoil

Harley V-Twin

Synthetic

20W-50

1200ppm


Motorcycle

Cosworth

Racing Oil

Synthetic


1150ppm

1250ppm

Vehicle

Shell

Rotella T CI4

Organic


1300ppm

1400ppm

Diesel

Pennzoil

Racing Oil

Synthetic

20W-50

1800ppm

1950ppm

Vehicle

Quaker State

Q Racing

Synthetic


1800ppm

2000ppm

Vehicle

Valvoline

VR1

Synthetic

20W-50

1200pp,

1300ppm

Vehicle

Valvoline

Racing Oil

Synthetic


1200ppm

1200ppm

Vehicle

Royal Purple

Racing Oil 21

Synthetic

5W-30

1130ppm

1961ppm

Vehicle

Royal Purple

Racing Oil 41

Synthetic

10W-40

1171ppm

1901ppm

Vehicle

Redline Oils


Synthetic

10W-40

1371ppm

1350ppm

Vehicle

Redline Oils


Synthetic

10W-30

1340ppm

1407ppm

Vehicle

Redline Oils


Synthetic

5W-30

1419ppm

1421ppm

Vehicle

Mobile 1


Synthetic


1223ppm

1376ppm

Vehicle

Joe Gibbs*


Synthetic

Various

6000ppm

6000ppm

Vehicle

Joe Gibbs Racing oil also has increased levels of Sulphur.

This was the information as of the middle of Jan 2008. Obviously almost all of the racing oils had increased levels of zinc and phosphorous, vital to the proper running of an Abarth motor. You should check on the brand that you are using, to make sure that it has not been reformulated. As a general rule, somewhere between 1000 -1200 PPM would be a good minimum number for both elements.

The follow-on question is then what weight of oil should I be using. The key to oil numbers is the second number. So, in 10W-40 weight oil, the "40" part indicates that this oil has a viscosity rating of 40 weight oil at 212 deg .F (100 deg. C) however it has a consistency of 10W oil. Now the question is, just what rating do I need? Do I automatically go for 10W-60? Well, maybe !!

The key is temperature and oil pressure. At whatever you oil temperature happens to be, you should be able to maintain 75 PSI (5 Bar) of oil pressure at 6500 RPM (this happens to be Ferrari's formula for high performance vehicles). If you can do this with 10W-30 then good. If not, then move up to 10W-40, or 10W-50 etc. In other words, depending on the state of the motor, you can tailor your oil grade to maintain a pressure level that is indicated. Using a grade of oil with a higher viscosity rating, beyond this, will only cost you horsepower. Now in the top leagues of auto racing they may use 0W oil for qualifying, but this usually means a motor that was broken in on the dyno on a higher grade, and then they only care if it last 3 laps.

For those who want to know more about oils and how they perform, please read this report. Draw your own conclusions. Yes, the report was sponsored by Amsoil, but the results really do speak for themselves.

http://www.syntheticoilnlubes.com/pdf/g2156.pdf

At Scuderia Topolino we break engines in on Shell Rotella T non-synthetic oil. This is for two reasons. First it has a good zink/phosphorous additive mix to protect the camshaft during break-in. Second, it is not "super slippery", and therefore rings will seat quickly in the cylinder bores. After this we change to Redline Synthetic Racing Oil or Amsoil 10-50 Motorcycle oil. Yes, motorcycle oil, as it has the higher level of zinc and phosphorous. Alternatively, Joe Gibbs oil is probably very good, but the price my put some people off.

Amsoil has also earned a very good reputation with their engine oils in motorcycle gearboxes with a rating equivalent to 80/90W gear oil. As it has no Extra Pressure (EP) friction modifiers, it may be a good solution for Fiat transaxles as well. This oil may work well with the standard synchro rings and the bevel gear pinion used in this transaxle. As it has superior gear wear characteristics, Scuderia Topolino hopes to test the oil on our dyno, and in the transaxle during the 2008 season, in preparation for a major effort in 2009.

 

 
Specialist Services
Calendar and Race Reports


Gallery