Thread: 4.6 Rebuild

I was up getting some info from company that is going to convert my 4.6 onto straight gas. (in the rangie ute I am building).

I am going to use Gas Research gear which is a bit more expensive but is meant to be a lot better.

The interesting thing was that he recommended not going to high with the compression ratio. I was always under the impression that high compression (like 10:1) was better but he has told me not to go past about 9.3:1 so installing High comp pistons should make it about perfect.

remember raising compression will generally also lift the rpms that the torque band happens at...

but for a bit more power and an improvement in economy if you dont take advantage of it.. If you HAVE to replace the pistons Id spend the $$.

Why not keep the lower comp pistons and ad some forced induction by means of a supercharger which will work good on either peterol or lpg 1k spent on superchargeing would give beta results than 1k on pistons and higher comp

Ron,
do you have an idea of the cost of the liners. I have a 4.6 block, crank and pistons here with just 1 stepped liner and I would like to have the others done before I put the motor together. I will get Crankshaft Rebuilders in Melbourne to do the machining but the cost should be similar I would think.

thanks,
Ian

I would go for the 9.35:1.
If you want to use ULP, you could get Bruce to take a little bit out of the combustion chambers to drop to say 9.00:1, as this is supposed to be the about the limit for ULP.
If you are going to run on gas most of the time leave it at 9.35:1 and use PULP.
Main gain is in economy.
Regards Philip A

Yes, I would be interested in the cost as well as I will be doing mine soon.

I know a I got a price from Deacon Automotive a couple of years back and they quoted $2k to step the liners.....but they tend to be very expensive.

I don't think I HAVE to replace the pistons. I think they are still OK but I'll get them checked. They might be saleable if I don't use them.

9.35 was standard fitment overseas. We got the low compression pistons.

I rarely use petrol so PULP isn't a problem. The higher compression should be useful on LPG.

The liners cost $2200 installed.

Ron

Ouch. That is is a lot isn't it.....especially for a fault which may or may not eventuate.


I emailed Dave Ashcroft from Ashcroft Engineering yesterday. I was told they were selling some new 4.6 blocks at very very cheap prices (under $3000).
Got the reply today and he wont deliver them overseas.


So looks like I will have to follow you and step the liner and install high comp pistons. I needed new rings anyway.