Guys haven't seen this conversion done, I would think that it would give the car a nice weight balance, I must admit I haven't been able to find the weights for the Holden red motor, six or eight, I believe the alloytec weighs under 170 kgs, can't see it being heavier than the red motor, it would also sit further back in the chassis which would be good for handling not that the car is a sports car.

I think what would really wake the alloytec up is more compression, I would suggest running it at 12 to 1. This bump in compression may and I stress may by offset grinding the crank. However I am not familiar with the crank except for what I have read. The fact it is a forged steel item with large journals is a good start, tidy up the heads which look pretty fantastic and build a set of custom headers and exhaust. An aftermarket manifold is said to add 30 HP to a standard engine, more on a modified one. Tuning via the blackbox also raises the game, good for up to another 30 HP.

My wife's car has a Gen IV 6.0 running a liquid LPG system which is a fantastic system, great power, tends to be around 5% better than petrol and great economy too. They make a liquid system for the alloytec, the conversion to gas will alloy the 12 to 1 comp ratio. Every point of compression adds about 3% so about 6% gain. In all and I know these changes need to work in harmony together to get a nice gain. However HP in the low 300 range wouldn't be hard to imagine maybe even mid 300s.

I wouldn't do the conversion on basis of outright power but a great and economical cruiser and it is something a bit different, which is part of the appeal. If the engine was lighter than what came out by a decent margin, I think you could crack into the 13 second area which is no slouch for a nice running small capacity N/A engine.

I'd still stick with an EFI 304. Bolts straight in with a HT-HG 253/308 sump and pickup.

It would be interesting to see how it would perform even
as a standard unit plus having cheaper 6cyl reg.

Agree on all points cloudy, that 3.6 is a great engine, more powerful than the 3.8 supercharged ecotec, I would use the sidi engine if I wasn't intending to use lpg, however there isn't a decent liquid system for them yet. Remember they start out with 225 kw or 300 HP from factory. The biggest advantage that direct injection has over a high comp LPG system is that no fuel is lost out the tailpipe during the overlap phase.

Also as you say they go quite well in a car that weighs 500 kgs more than a HK, so couple that with most likely a further reduction weight reduction with an alloy V6 versus a cast iron inline 6.

As we already have 3 V8s in the household I don't want or need anymore hence the looking for interesting options.

Cheers

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Originally posted by petaus
even just by increasing the rev limiter they make heaps more power, but then the rods start to come out lol

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I had no real idea of the strength of the rods, however as I mentioned in the opening post, offset grinding the crank would require new rods and after working out the options, a suitable aftermarket rod could be found.

I would love to put the heads on a flow bench as I am pretty sure they are stellar heads. They would certainly flow more than any cast iron head ever fitted to a Holden. Just need to maximize that airflow into a suitable package. In the all out attempts with high revs they make over 400 HP. That is like the earlier Porsche GT3 engines and given the bore is smaller than a GT3 that is quite an achievement.

However for a good driving/cruising car which is what i want, the engine needs to be tuned in around where the factory has it now. So I need to trap more air in the cylinders to get the VE up, maybe regrinding the cams is an option? Quicker ramps and a touch more duration.

What I have found with engines I have built is that when you build a great exhaust and then bump the compression, tidy the heads, intake etc, the engine really takes off because you have increased air velocity in the tracts and that gives great throttle response too.

Cheers