The Holden Grey motor is often referred to as the Holden side plate. The engine earned its name as they were painted grey from the factory. They came in 2 sizes, 138ci and 132ci. More engineering and after market modifications have gone into this engine than any other engine in Australian automotive history.

August 03, 2014

Performace Holden Grey motor build

15:42 Posted by Unknown 1 comment


The project started with a call from Graham from Bombala NSW enquiring about a 3-1/4 piston kit I had put together for a grey Holden engine. He owns a restored FJ Holden and was wanting to repower it with a hot grey and top it of with something unusual. I suggested a multi point EFI and electronic ignition to which he agreed and away we went from there.

I had in stock a standard bore Canadian block (as the myth goes).  These blocks were believed to have been able to be over-bored to 3-1/4" so to be sure we had the team at Orger Engines in Bayswater, hot tank, crack test, pressure test and sonic test the bore walls for thickness and core position, which is critical when overboring an older engine to large sizes. It was determined that this block was not suitable for our project. The lack of parent metal around the bore would not support the deck surface leading to deck distortion and possible head gasket I failure and overheating. I then provided three more blocks for inspection and all failed. I had been warned I may have to go through as many as 10 blocks to find one suitable, at around $300.00 a block we decided not to worry. A 3-3/16" piston kit was purchased instead and our project was under way. 




Prior to the acid cleaning we removed all welch plugs and scratched out the lower troughs of the water jackets to remove hard scale that acid cleaning often does not remove. Removal of the main oil gallery plug at the rear of the block and using a length of 5/ I 6' rod to tap out the front oil gallery plug is also essential to cleanliness before we start. Don't forget to refit this gallery plug on reassembly.

The first machining was to bore and hone the cylinders and then to machine the deck. It required the removal of .015" to clean up and another .015" to aid in compression gain. On the bottom end, in the past, main bearing strengthening caps were bolted over the main caps. These are becoming hard to get so we fitted a set of EJ caps which are much stronger than the other models and then once again line-bored the main tunnels.  The main bearings were then fitted and the ID measured to calculate an accurate size to grind the crankshaft journals.

Below: The grey con rods are robust and reliability can be assured by doing several simple mods. Rod bolts from Mitsubishi four cylinder can be used, or they are also available from ARP Fasteners.



The grey crankshaft has an inherent problem with breaking if held in the high 5000 RPM zone. The ideal fix is to replace it with a similar period Vauxhall six crank. This is an expensive job so I selected a crank that had only shallow factory balance drillings in the counterweights which lessens the interruption of the casting grain. Heat treatment or Tuff Triding is also recommended.  The flywheel was lightened and a red motor style modern harmonic balancer was acquired to assist in smooth running. Grinding the journals to undersize presents no problems when it comes to strength as a competent grinder will grind in a large radius in the fillet area that helps in retaining strength.

The grey con rods are very robust and reliability can be assured by doing several simple modifications. Rod bolts from a Mitsubishi four cylinder can be fitted, or they are also available from ARP Fasteners. Polishing the side beams, shot peening all over and resizing makegthefobrig nice tunnels will rods.

The was camshaft sent to Wade Cams in Oakleigh for regrinding, it is important to check the distributor drive gear as they are prone to wear, rendering the cam not serviceable. The grind selected was usually used in speedway cars and is a little strong for smooth street use, but as we were using electronic fuel injection this will help maintain high manifold vacuum and lowdown driveability and a nice lumpy idle at the tailpipe.  We fitted a billet steel timing gear supplied by Motor Improvements in St Kilda and pressed it on with .006" clearance to the thrust plate. 



The bottom end was now ready for the final cleaning and assembly. To assure no piston ring damage the bores should be scrubbed with a course nylon brush and strong detergent to remove honing residue.







Once the crankshaft and number one piston were fitted, we then slid the camshaft in and set up the dial indicator and degree wheel to check our cam timing specs were correct. With only one piston in it is much smoother to turn the engine over to make accurate movement to read our specs.

GM recommend 006" backlash on the timing gear.  With the gears in mesh I noticed there was no backlash at all, which is a recipe for failure as the gears will grind themselves away. We rotated the crank at 90° intervals  and it was still tight, after scratching our heads we realised that the line boring had closed the centreline dimension between cam and crank, so we removed the cam, pressed the gear off and had the gear teeth recut to give the required backlash and saved a disaster.

With the bottom end now assembled, we set about to recondition the oil pump.  The common wear area is the end plate so we resurfaced it and on reassembly fitted a new old stock kit that includes a new relief spring and plunger.

The cylinder head was supplied by the owner which he purchased already built. It had been ported out and red motor valves fitted, double valve spring kits are a little tough to find so standard V8 Holden springs canbe used which will give around 80Ibs closed seat pressure and no problems nbe used which will give around 80Ibs closed seat pressure and no problems with bending pushrods. A standard thickness head is around 3.300" thick, most heads can be machined down .100" to achieve a compression ratio of around 8.00:1. There is a telltale casting mark on the gasket face of around .060" deep that will give you a clue of previous machining.

Regularly on performance engines the head bolts are replaced in favour of studs. I fitted ARP studs that come with ground hardened washers and deep nuts in black oxide finish. On fitting the head gasket they can be moved around a little so it was positioned so that the fire ring was concentric with the top of the bore.The head was then fitted and torqued down using moly lube under the washers and on the threads. A small problem is created when fitting the side plate after heads and blocks are machined. The bolt holes into the block must be elongated and the rear lower corner trimmed around the distributor boss area to allow it to seal up. The rocker gear was reconditioned as standard and the only modification was to screw a small self tapper into the oil feed union bleed hole in the middle of the two rocker shafts.



Above: In the past, main bearing strengthening caps were bolted over the main caps. These are hard to get so we fitted a set of EJ caps which are much stronger than the other models and then once again line-bored the main tunnels.




The engine was then sealed up and painted which led us onto the next owner request of speed equipment with a difference. The distributor building was handled by Dick O'Keefe from Performance Ignition Services in Nunawading. He used a Ford style electronic body and custom made low resistance spark Ieads.  We supplied an original drive gear and he machined the base and shaft to suit. It was then re-graphed to suit the compression and fuel to be used.



The induction was to be the highlight of the project.  When we first spoke I opened my big trap and said that I had begun to assemble a multi-point fuel injection and needed an engine to fit it to plus a reason to complete it.  We started with my own cast throttle bodies that were bored to I - I /2" and SU butterflies and shafts were fitted. I then fitted spun alloy ram tubes to the intake side to keep it looking old style.  The computer was our next task. I decided to use the Autronic system for several reasons, primarily the local agent, David Baillie, has been working with this system for years and works closely with me in my workshop using the Autronic air/fuel ratio computer to cure many street and race car problems we are faced with. They are also an Australian company. With the help of Richard Aubit the owner and designer of these systems, we fitted 5.7 litre Commodore injectors on a common fuel rail, a Commodore fuel pump and an adjustable fuel pressure regulator.



These projects always present problems in getting them up and running so we enlisted the help of Danny Selva from Selva Racing Poewr Dyno services to help make the jigs and set the engine up on his dynometer.  David Baillie pre-set the computer to a general start mode, we spun in over to get up oil pressure, hit the start button and it fired into life.  I fitted a weld-in bung to the header pipe and had the oxygen sensor screwed in so that we could accurately make adjustments as we loaded the engine  up with the fuel it required through the RPM range.  These systems aslo have a cold start capability inbuilt that are also adjustable.



After a day in the dyno room we were happy with the engine and it was ready to be fitted to the car.  The owner did the fit off and David and I drove across to Bombala to do the final on road setup with the portable ait/fuel ratio meter fitted in the exhaust system.  The vacuum characteristics changed a little with the car weight so it’s essential to complete the final adjustments while in the car.


Article from Street Rodding magazine by Malcom Chruch.




1 comment:

  1. Hi, with the "Canadian"block, how are they identified? Is it the different logo cast into the side?

    ReplyDelete