LPG motor on Petrol NA

[Mustangman570]

There is a lot of talk about using a LPG motor with boost (like on Carnage). But I haven't seen much on running an LPG motor NA on petrol. Since the green tops are higher compression I imagine they would make decent power on petrol with a tune, extractors and a good cold air intake. I'm assuming someone has done this in the past. Could you point me to a thread for more info. Cheers

[k31th]

Yes, it's an option... but not a good one as the extra compression just invites knock, hence why people go E85 etc which is far more knock resistant.

[El Andrew]

Not a bad idea though. Especially if you ran it exclusively on 98. When designing the NA motor and determining compression ratio, Ford obviously had to assume 91.

[Puffwagon]

The reason people want to use the green top is because the rods are an unbushed turbo version. They are a fair bit thicker than the normal na version. The pistons are just as weak as the na pistons when you have a close look at them (there are holes through the skirt in the oil ring groove and less material around the pin area) and obviously being semi floating, aren't great for high load boosted applications. With the tight ring gap, under boost, the pistons just crack or tear in half horizontally when the rings inevitably touch.

 

They would go alright in an na application but as mentioned you'd want decent fuel. They were designed to run LPG which has a much higher RON than pump fuel.

 

Obviously there is stuff all in Florida to get hold of, but there is a place here in South Australia that sells all kinds of parts, including new gas pistons etc, if you wanted to experiment with the different compression ratios.

 

https://www.precisionintl.com/