Holden HG Project Part 2 – Engine Rebuild

By: Greg Leech, Photography by: Ellen Dewar

Date: 03.03.2009

Project HG Part 2 – Engine Rebuild

Our pet HG Premier gets a fresh-up for the powerplant...

Holden HG Project Part 2 – Engine Rebuild

Project HG Part 2 – Engine Rebuild

Holden HG Project Engine Rebuild

Time to breathe some new life into the old girl. And she should have some real hop now. Here’s what we did…

The engine in the HG project Premier was an unknown quantity. We knew it started, but ran on five cylinders and very rich. So, it seemed like the right place to start our restoration.

It was off to engine building supremo Keith Davidson from Davidson Race Engines to find out what just what we had.

In Keith’s own words, "There was no doubt the engine needed a complete rebuild. It was at the end of its days."

Okay, so we knew where we stood.

LET'S OPEN HER UP

The first step was removing the engine from the car and totally dismantling it for inspection. During this process it was found that the engine had been rebuilt once before; the bore was already 30 oversize. Also, the crankshaft was cactus, so a new steel item was sourced.

Interestingly, steel crankshafts cost more and are more desirable among enthusiasts, but Keith suggests the cast ones are just as good.

"For a streetable 192 like we’re building here, cast would be fine," he tell us. "Ours is steel and it looks better, but Holden red six crankshafts just don’t break. There are cases of cars running 13 pound turbos, putting out 500 horsepower on red six cast crankshafts!"

Back to the workbench, and the next job was boring and honing the block to suit ACL flat top pistons. The block was decked, refinishing the block surface and gaining zero deck height (where the piston top is level with the top of the barrel) at top dead centre.

New rods were the order of the day and we decided to up-spec a little here, fitting Starfire rods (these are stronger than the standard red items). They had to be resized of course. New 60 oversize pistons were also fitted.

Next came the balancing of the engine. This entails physically balancing components including the crankshaft, flywheel, pressure plate and balancer, conrods and pistons. A big job, but one that is essential to arrive at maximum power and a happy donk.

Up at the top-end, the cylinder head came in for some real attention, and this is where a lot of the real power improvement is to be made. Keith throated out the ports, and totally reconditioned the head to suit the use of unleaded fuel via fitting hardened exhaust inserts.

New oversize XU-1 sized valves were fitted, along with stiffer performance valve springs.

A warm 70/30 camshaft got the nod. While the cam will improve horsepower numbers (along with the cylinder head improvements), we decided to keep the car streetable. We could have gone more radical on the cam grind, but at this level the car will still pull strongly off the bottom – torque characteristics are much improved – economy remains acceptable and, more importantly, manifold vacuum is retained.

The compression ratio was set at 9.5:1; once again, sensible but greatly improved.

The engine was basically blueprinted, meaning all tolerances and dimensions were methodically checked and adjusted to suit our hot-up application.

Time for full assembly. Carb/inlet duties are now handled via a tried and true 350 Holley and Redline manifold along with a set of performance extractors to help with the exhaling characteristics of our now much improved 192ci beastie.

The engine was placed back where it’s going to live and is now ready for a bit of dyno time to optimise fuel mixture and ignition curves.

SHOW ME THE MONEY

So, a rebuild like this will set you back around $4000. That’s pretty cheap when you consider you get a pretty bulletproof, essentially brand new engine that you could drive reliably to the moon.

Once again, this type of restoration is in the realm of most people that want to be involved, get the fun and satisfaction of doing a car up but don’t want to take out a second mortgage to do it. Value? That’s what we are talking about. Go for it!

Next up, the HG gets all new exhaust and suspension. She’s coming together...

THE MASTER…

Keith Davidson has forgotten more about building hot Holden red engines than most of us will ever know.

He found he was doing so much performance work for RPM Engines that it made sense for him to start doing it for himself. His business Davidson Race Engines was born and he hasn’t looked back.

Keith builds a lot of the engines we see in front-running HQ racers, so reds come through his Romsey, Victoria premises pretty regularly.

He reckons the majority of his work is older muscle-related, although he has four XR8 quad cam engines slated for his touch right now. His work is sought after because he’s meticulous and that’s what anybody looking to get some resto/hot up work done should look for.

Keith Davidson can be contacted on 0401 533 564 or email (which he greatly prefers) keithdavidson57@iprimus.com.au

THE BILL SO FAR

1971 Holden HG Premier

Original purchase of car: $3500

Engine hot-up and rebuild: $4000

Total: $7500

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