Presumably you cam deck the head to up the CR whilst the engine is out?

 

Not a big job so I guess it doesn't really matter which of the engines you start with??

You doubt you will be able to get an 8.33:1 3.9 litre engine up to 10:1 by skimming the head. By my calculations each cylinder is 494cc. At 8.33:1 compression the compressed volume is 60cc. So to get to 10:1 you need to reduce the compustion chamber by 11cc. Its only 28/35cc to start with. Thats a lot to skim off.

 

Having said that its probably worth checking how the compression ratio is achieved. I seem to remember reading that the compression was sometimes dropped with a composite head gasket. If it is you can just change to a standard gasket to get the ratio up.

carefull with the skimming. Too much and the inlet manifold won't fit anymore

rather than going to the trouble of head scimming just fit a blower or turbo a 91 3.9 should be a good un check the oil filler for creamy sludge a sign of death for a V8 ,good luck ive only got a 3.5 to play with

pete2b

good luck ive only got a 3.5 to play with

(It had to be done!) Everyone say aaahhh (in a strong and manly way of course).

 

Nigel

Your best bet is to get hold of "Tuning Rover V8 Engines" by david Hardcastle. Lots of good advice in there. Add to it the forums on www.v-8.org.uk and you'll have plenty to think about

I have David Hardcastles book. I would agree, its well worth a read.

My dad has got a 3.9 in his RH but it was especially designed for it. Uses the SD1 gearbox as well. Sounds amazing!

 

He's out of the country at the moment so it is off the road. He was changing the gearbox recently.