HELP!!! Can I use the bottom end of a XR3I on a RST?

Slik Johnson · 21-02-2009, 06:55 PM

I've got hold of a RST engine apart from the bottom end. As I'm running a XR3I MFI engine I thought I could use the block from that, but the guy I'm buying the engine off said it will not hold up as the top end is pushing aroud 200bhp. Can I use my bottom end for the RST convertion??? HELP!!!

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Rick · 21-02-2009, 08:37 PM

No mate. The block on an RST has an oil return in the casting. You could modify your sump for this though. Main problem is your pistons are too weak, and give too high a compression. Do you know the mfi on a 3i is totally different from an RST?

iansoutham · 21-02-2009, 09:41 PM

You can fit an oil-return into an XR3i block, well EFI anyway.

The EFI one has a casting blanked off which you simply drill out and insert the metal insert from the crankcase breather in the block (same insert). MFI may not have the casting which is big enough though. Have never checked.

21-02-2009, 08:37 PM	#2
Rick 15K+ Super Poster!! Garage is empty, add now Trader Score: (0) Join Date: May 2003 Location: Stockport, Cheshire Posts: 15,560 Rep Power: 24	No mate. The block on an RST has an oil return in the casting. You could modify your sump for this though. Main problem is your pistons are too weak, and give too high a compression. Do you know the mfi on a 3i is totally different from an RST? __________________ Bespoke calibration and remapping, OEM & Aftermarket management

21-02-2009, 09:41 PM	#3
iansoutham OCD Victim Garage is empty, add now Trader Score: (0) Join Date: Sep 2005 Posts: 1,687 Rep Power: 8	You can fit an oil-return into an XR3i block, well EFI anyway. The EFI one has a casting blanked off which you simply drill out and insert the metal insert from the crankcase breather in the block (same insert). MFI may not have the casting which is big enough though. Have never checked. __________________ "What is your major malfunction soldier?" Hi. This is the qmail-send program at kermit.axnoc.net. I'm afraid I wasn't able to deliver your message to the following addresses. This is a permanent error; I've given up. Sorry it didn't work out.

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21-02-2009, 09:41 PM
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