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MG MGB GT V8 Factory Originals Technical - Rover P6 pistons on SD1

Hi there all. I'm taking a break from the MG Bodywork and making a start on the V8.
I'am rebuilding an SD1 engine (approx 1986) and have a good set of samesize 10.1-1 comp-ratio P6 pistons. Does anybody know if these are a straight swap. Would I have to swap onto the SD1 conrods? I have heard that using different pistons/conrods to the original crank can cause balance problems?? Only planing about 200bhp, fastroad motor. Anybody recommend a good cam? I currently have a 3.9 cam.... not sure if it is any different to the SD1 standard cam.
Sorry for all the questions.
Many thanks
Brian
b bourne

The early O/E P-6 pistons are lighter than the sd1 pistons. I rebuilt my P-6 motor with NEW .020 over pistons & thay were 100 grams heaver (I think, 21 years ago I did this). Rod are the same. 3.9 cam is good. You can mill .040 off the top of the block & make sure the piston sits .010 below the deck, use steel shim O/E head gasket & you will get 9.5-1 comp. with the sd1 pistons. Have done this mod. to a LOT of motors! Sd1 pistons are much better than P-6 piston. Lighten the flywheel to 20-22 lbs. (hits rpm faster). Hear in the U.S. I do not have run high test, I run the mid grade (89 oct.) with the 9.5 comp.
Glenn Towery

Brian,
In addition to the helpful information from Steve above , there are several books on conversions for the various Rover V8 engines into MGB's you may want to buy.

The most popular ones are by Roger Williams.

Pete.
Peter Thomas

Gents, Many thanks for the replys. I think I,m more or less heading in the right direction.
Cheers
Brian
brian

This thread was discussed between 04/01/2008 and 17/01/2008

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