4.6 block swap

gulf blue rsr · Post by **gulf blue rsr** » Sat Dec 04, 2010 2:42 pm

I've got the dreaded pressurising block problem with my 1999 4.6 thor p38 Range Rover.

I've done a deal with a nice man for an engine out of a classic advertised on here, basically it's an rpi built engine with stage 1 heads rp4 cam balanced crank and pistons etc

Now I'm guessing that it will be running with a distributor and front cover to suit etc, the question is am I right in thinking that I can just pull my engine, swap the flex plate and everything else that is needed from the rear of the engine to suite my gearbox, then swap the front cover with oil pump etc for the serp belt type of my engine, and then put it straight in?

Will everything be there for the various sensors that the p38 will use (mounting bolts/lugs etc) will the crank nose and rear flange accept the p38 parts and cover/pulleys?

Am I correct in assuming that as it is 4.6 it will just be a p38 block backdated to suit a classic waterpump pulley and distributor cover etc, are all the 4.6 castings the same?

One last thing, am I correct in thinking that the Thor ecu is self tunning to the modded heads/cam?

Sorry for long post but don't really want to make a monster job out of a simple engine swap!

spend · Post by **spend** » Sat Dec 04, 2010 2:52 pm

There are 2 different caps tigged in to hole for the flwheel crank sensorj, odds on you will have the later one & said block is the later one. Not sure if you can just plug the Bosch ecu into the Gems sensor or vica-versa?

gulf blue rsr · Post by **gulf blue rsr** » Sat Dec 04, 2010 2:57 pm

Thanks for quick reply!

Is the sensor at the front or back? would it be possable to alter the hole? I have a friendly engineer as a top class tig welder

Anyone know if the sensors swap?

Also are the sensor points there on all 4.6 blocks?

STEVE

topsparks · Post by **topsparks** » Sat Dec 04, 2010 6:43 pm

Thor and Gems are different,they are Tig welded in,but you can swap them over ,I have an aloy mig welder,but need some more practice!

ChrisJC · Post by **ChrisJC** » Sat Dec 04, 2010 7:57 pm

The crankshaft sensor hole in the block is the same on all blocks as far as I know. There is an insert which mounts the actual sensor, that may be different and needs bringing over.

The camshaft sensor is also possibly different between GEMS & Thor, but if you are bringing over the front cover, that should be fine.

Go for it.

Chris.

dnb · Post by **dnb** » Sat Dec 04, 2010 9:01 pm

I believe the trigger pattern on the cam sensor is different between GEMS and Thor engines. This is determined by the cam pulley rather than the sensor itself.

I believe the pulleys are compatible between the later cams (early cams may not be compatible), although I am not 100% sure on this.

Yes, the Thor ECU does do learning type tuning and it's not too bad at it.

Muscle-Manta · Post by **Muscle-Manta** » Sat Dec 04, 2010 10:31 pm

Quote" then swap the front cover with oil pump etc for the serp belt type of my engine, and then put it straight in?"

Only if the new block is also serp type!

To convert a "V" belt engine to serp you need a longer woodruff key on the crank to drive the oil pump.

The 3.9 intrim engine was serp with a distributor. They have the short nosed crank like the v belt engines, however with the longer woodruff key to drive the crank driven oil pump.

The 4.0 and 4.6 engines have a longer nosed crank than the earlier engines. I am not sure if you can use the front cover from this engine on a short nosed crank engine. You may need an intrim front cover. I am sure someone on here will have the answer.

Paul

spend · Post by **spend** » Sun Dec 05, 2010 12:00 am

He has to swap the cam... if it had a cam that drove a dizzy the front cover won't go down and the cam gear won't fit on that cam. (followers as well)

gulf blue rsr · Post by **gulf blue rsr** » Sun Dec 05, 2010 12:43 am

Hmmm thought this might get complicated and throw a few ?????'s!!

So basically from what I'm reading the general thoughts are that if nothing else the block and pistons will work no problem.

The cam may need changing but I can use my existing cam and followers at worst, at this stage all I really need is for the engine to be in and running to get the car usable, performance can come later! Although if possible I would like to use the cam from the new engine as newer and uprated, without more details I may or may not be able to just change my cam pulley from my existing engine to the new one?

Assuming that the new engine is built from a original 4.6 not built up to 4.6 by change of crank/rebore and pistons from a smaller block, would that then mean that the crank must also be a long nose crank with a spacer on to adapt to a different front cover to suit a dizzy on the new engine existing set up?

From the way I am reading all the answers so far all looks good to go and looks like I have found myself a new engine/project for the next couple of weeks!

Thanks for all the replies so far keep them coming, I'm sure I will be asking more ?????'s before this engine is in and running yet!!

Steve

Muscle-Manta · Post by **Muscle-Manta** » Sun Dec 05, 2010 2:25 am

As long as your new short engine is an original 4.6 you wont have any problems, apart from the cam as Dave has quite rightly pointed out.

I have to admit I didn't read your first post all the way through and thought the new engine was the earlier type as it had a "V" belt front cover....sorry about that.

Regards, Paul.

gulf blue rsr · Post by **gulf blue rsr** » Sun Dec 05, 2010 10:28 am

Thanks Paul for clarifying that point.

That's it then I will be carrying on and buying the engine then!

Thanks for all the help with this.

Steve

chrisbowler · Post by **chrisbowler** » Fri Dec 31, 2010 7:52 pm

If it is any help, I an currently converting a 4.6 GEMS engine to run HOTWIRE. Have got complete HOTWIRE front end SERP timing cover PAS and Alternator set up and have up upgraded 3.9 cam and tappets with 3.9 timing chain and gears.

Why - I wanted to run a stand alone GEMS in the DISCO 1 but cannot find GEMS manual flywheel anywhere

Chris Bowler

DEVONMAN · Post by **DEVONMAN** » Sat Jan 01, 2011 2:09 pm

A minor point not yet mentioned is that you will also need to swop the sump and oil pickup pipe as the front is shaped to suit the vertical oil filter on the 4.6 timing cover.
Regards
Denis

chrisbowler · Post by **chrisbowler** » Sat Jan 01, 2011 8:56 pm

Good point - I have that bit still to do - Only have the headers, dissy and aux drive belt left to fit and after putting oil and coolant in we can fire the old girl up.

I had a 3.9 serp engine as the donor so all parts to hand.

Regards Chris Bowler