AV1-16 vs AV1-1644 on a small (5 litre) V8?

[storm]

Just looking for some feedback before I consider ordering a AV1-1644 for my IMPCO 425.

My engine, still on petrol, is a 5 litre (308ci Holden) V8. I will be fitting a T700R4 for an overdrive that will bring the revs down to approx 2000@100km/h, it currently has a T350 and the revs are aprox 3000@100km/h. I was wondering if it would be beneficial to economy if I fitted a AV1-1644 gas valve instead of using the AV1-16 that it come with. I know the lean gas valves are intended for larger small blocks and big blocks from about 370 ci (>=6 litres) but wonder if a small V8 like mine would still benefit from one.

Does anyone have any ideas or experience with this?

[Steptoe]

The 1st thing I would do is drop the new trans in..as thats a definate , right?
Then look to changingf other stuff ... one thing at a time
Personally once u get that 308 ci cruising at around 2000 rpms /60mph, get timing/ mixtures into ball park u should do better than my 17+ mpg of lpg
And then put that into NZ petrol price terms, u are around 30/32mpg, considering the wifes old corolla did 38 granny footing.
Or in other terms a 308 ci about the same as a 2L car. or the same cost as a 96 bighorn diesel..
Get there and to go further u are really starting to push proverbial up hill.

[storm]

The 1st thing I would do is drop the new trans in..as thats a definate , right?

Yes I am hoping to order it this month, depends on how much work I get, and i'll fit it over the Christmas School holidays probably early January when business' reopen so I can get a new (shorter) front tailshaft.

Then look to changingf other stuff ... one thing at a time

That was my plan but knowledge is power so to get knowledge I asked a simple question about 1 aspect of an IMPCO 425. Can we stick to that please?

Personally once u get that 308 ci cruising at around 2000 rpms /60mph, get timing/ mixtures into ball park u should do better than my 17+ mpg of lpg
And then put that into NZ petrol price terms, u are around 30/32mpg, considering the wifes old corolla did 38 granny footing.
Or in other terms a 308 ci about the same as a 2L car. or the same cost as a 96 bighorn diesel..
Get there and to go further u are really starting to push proverbial up hill.

Mate, I know how to tune an engine. I used to get 24 mpg (Imperial) out of my 6.6 litre Pontiac Trans Am 4 speed Bandit using a Quadrajet without going anywhere near the timing nor did I pussy foot driving around but when I got to cruise speed the driving was stable. The comparison between NZ and AU running costs is not valid, the comparison between a Corolla and a truck and my car is not valid. I don't have to be happy with OK fuel consumption according to NZ cost comparisons. I live in a big country, I do a lot of miles, I want the best economy I can achieve with my engine with a reasonable outlay.

All I wanted to know is there any measurable benefit on a small 5 litre V8 in using an AV1-1644 compared to the stock AV1-16. I want cruise economy, of course I will set the timing up accordingly but timing is not the only thing that affects fuel economy so the obvious question of fuel flow through the gas valve at cruise comes to mind. It is rather like swapping out a Quadrajet's Primary needles on a 308 from a 41/42 to a 43/44 while keeping stock jets or adjusting the APT with stock needles, this works on a petrol engine of about 5 litres (and you get even more benefit with 6.6 litre Pontiacs btw) with a Quadrajet. I was simply wondering if the same reasonable benefit could be achieved with a simple gas valve swap, from the standard gas valve to the lean cruise valve, on the 425 in a 5 litre. Can we stick to that please?

[C3H8]

Missed this post. Is there a measurable difference? The answer can go either way. The 1644 was introduced to handle vehicles larger in size, say 2 to 5 ton. Also for trucks pulling fairly heavy trailers especially with blunt fronts with a lot of wind resistance. IMPCO deigned the profile of the valve to remain leaner longer. Drivers that did not floor the gas pedal to get up to speed could achieve better economy. The power portion of the valve did not come into play unless the engine was in a higher RPM situation and at least at the 80% plus mark for load. This kept the engine from demanding fuel when it really did not need it. Some of the issue was the transmissions in these trucks that were designed to keep the engine at the peak power range. If you look at a 366 GM truck engine the governor was set for 3600 RPM. This engine had its best power from 2400 to 3200 RPM. Drivers that kept the RPM under 3000 could take advantage of the 1644 valve. The valve will also be effective on smaller vehicles. How much. I don't think there is any quantifiable data. The design of the valve can make an engine feel a little lazier in the mid to upper range. This causes some drivers to just step harder on the gas and the result is little benefit to these drivers. Easy going drivers can achieve some benefit but there are not guarantees as to how much. Some of our customers loved it. Others took it back out after trying it. Sorry I can't provide any specific data.

[storm]

Thanks C3H8, based on your response I'll finish setting the car up and drive it for a while. Early Commodores aren't heavy and are, for their age, reasonably aerodynamic so it is highly likely that there wont be much of a difference. I'll get some figures from normal driving and then make a decision. Thanks again.

[Imperial73]

The few 1644's I sold also gave varying results. So if you decide to buy one, consider it an interesting experiment rather than a fuel saving device.

[storm]

If I do fit one its primary purpose will be to see if I can save money on fuel, there is no other reason to even consider doing it. Depending on where I get casual work I can drive through town with very little highway driving (10 minutes max) or I can have mostly highway driving at 100km/h (30 minutes) with about 1km of 40-60km/h. The highway has hilly sections but in my wagon (1996 VS Commodore with a 3.8 Ecotec and 4L60E) the cruise control is smooth and very rarely does the automatic kick down out of overdrive on the hills to work. I am hoping the Brock will be similar. Now I am older my driving style is conservative unlike when I had my TA. I am basically after a very nice high speed cruiser that is powerful (when required) but easy on fuel and comfortable to drive.