4.6 Rocker arms on 3.5 engine

smoker · Post by **smoker** » Fri Apr 06, 2012 3:38 pm

Hi all, I replaced my worn rocker gear with a set from a 4.6 Range Rover and now my engine is missfiring and difficult to start.

Car is a 3500 Rover SD1. Engine ran okay before apart from the tappety noise from the worn rockers. I thought 3.5 to 4.6 Rocker gear was a straight swap ?

unstable load · Post by **unstable load** » Fri Apr 06, 2012 6:39 pm

You probably had the plug leads off, so first step is to recheck they are on the right plugs and also if they are correctly pushed onto the plug and distributor.
Backtrack all the steps you took to dismantle and follow them through. 9 times out of 10 it's the last place that was worked on that causes troubles post maintenance.

ChrisJC · Post by **ChrisJC** » Sat Apr 07, 2012 8:14 am

3.5 to 4.6 rocker gear is a straight swap, so that's not an issue. But best to be sure that all the pushrods are correctly located in the end of the rocker arms.

Chris.

smoker · Post by **smoker** » Sat Apr 07, 2012 4:42 pm

Thanks John & Chris,

Checked that the plug leads were correctly fitted - I only took off No 2 & 4 from the RH bank to get the rocker covers off.

The engine was really reluctant to start and sounded flat and unwilling to rev like the time I refitted the rocker shafts without the shims under the posts. I presumed that the valves didnt shut properly so always fit them now.
The heads and inlet manifild have had about 50 thou skimmed off about 2 years ago.

Valley gasket is off now and all that seems to be wrong is that that the tappet on number 3 exhaust has no preload. Could explain the lifter noise but not explain the poor starting and running. I'm going to try to reassemble with thinner shims - cant see why fitting the 4.6 rockers would prevent the engine running properly as it was running fine, if a bit noisy with 3.5 gear.