hideously expensive main bearings?

chuggernought · Post by **chuggernought** » Wed Oct 31, 2012 10:53 am

i have a lateish(1998) serpentine 3.9 disco engine to rebuild, it would seem it uses a 4.0/4.6 block with a 3.9 crank as the crossbolt castings are there on the block but not drilled also has full width mains carriers but not drilled and tapped for cross bolts etc.
the problem is main bearings appear to be an odd size and only available from main dealer at £160+ a set!!!!

i suppose this is because the last of the 3.9's used the later block for the 4.0/4.6 with its bigger crank journals ready for the disco 2 and already used in p38 and they just fitted slightly thicker mains to make up the difference until the end of disco 1 production?
is there really no firm that makes mains at a reasonable price for these "interim" engines? ive been building v8's for years but mainly older 3.5's and 3.9's and never come across this before, dont want to be bent over and screwed if i can help it.

kiwicar · Post by **kiwicar** » Wed Oct 31, 2012 11:12 am

Hi
Are you positive this is the case? just 4.0 mains are a lot bigger than 3.9s and if things are as you state the shells will have to be very thick. If it is the case that you have 4.0l main bearing bores I would just bin the crank you have and get a 4 litre crank (£25 for the crank in used servicable condition about £50 for the rods) and rods and use them, because it will be cheeper than forking out £160 for shells

Best regards
Mike

spend · Post by **spend** » Wed Oct 31, 2012 11:30 am

Are you sure about what you are saying?

Sounds possibly like its just a 3.9 small journal, but the usual faffing over the thrust bearing (bottom half plain).

chuggernought · Post by **chuggernought** » Wed Oct 31, 2012 11:44 am

according to my engine number(at work so cant put it on yet ill add it later!) it corrersponds to these bearings STC 3724, tried 4 different suppliers and they all say the same, main dealer only and between £160-£220!!!
must admit they do look a little thicker than expected, cant think of any other reason for them to be main dealer only unless they only fitted them to a couple of years worth of the last 3.9's
could do with someone mikeing up a set of standard 3.5/early 3.9 to see what the difference is

chuggernought · Post by **chuggernought** » Wed Oct 31, 2012 11:49 am

spend wrote:Are you sure about what you are saying?

Sounds possibly like its just a 3.9 small journal, but the usual faffing over the thrust bearing (bottom half plain).

go on then whats the thrust bearing faff? can standard 3.9 mains be modded?
i am a 3.5 man, larger v8s a bit new to me.

spend · Post by **spend** » Wed Oct 31, 2012 1:16 pm

chuggernought wrote:
spend wrote:Are you sure about what you are saying?

Sounds possibly like its just a 3.9 small journal, but the usual faffing over the thrust bearing (bottom half plain).
go on then whats the thrust bearing faff? can standard 3.9 mains be modded?
i am a 3.5 man, larger v8s a bit new to me.

The 'note' on:
http://www.v8tuner.co.uk/product.php?id=33
says it all.

At the price you have been quoted you could buy 2 normal sets to get the extra plain shell for the cap end of the thrust bearing.

Try V8D they do 100's of cars with that spec bearing (nearly all small journal TVR's Chim/Griffs havethat spec). Even TVR Power will be cheaper than what you were quoted.

You DO NOT have a large journal 4.0/4.6 anyway so try not to get confused with that issue (the crank pins would be 2.5" rather than 2.3"). Your issue is simply how the block, cap & crank are formed to accept thrust bearings (they are what limit the crank going fore / aft). There are some issues with some thrust bearings being the wrong width, but as mentioned the easiest answer is to just get them from someone like V8D.

bodger · Post by **bodger** » Thu Nov 01, 2012 8:53 am

have you tried ISLAND 4X4 ... i always use tham for my bearings

http://www.island-4x4.co.uk/

paul c · Post by **paul c** » Thu Nov 01, 2012 11:28 am

bodger wrote:have you tried ISLAND 4X4 ... i always use tham for my bearings

http://www.island-4x4.co.uk/

I am not sure if Island give you a choice of manufacturer, I stopped getting parts from them after a few britpart failures.
V8 Tuner has been good for bearings and other engine parts for me.

softdash3.9 · Post by **softdash3.9** » Thu Nov 01, 2012 7:44 pm

I have an interim 38D in my Range Rover Classic, cross bolt pads, with no bolts and non crossbolt main bearing clamps. (38D low comp 8.13:1 cr, 36D are 9.35:1 cr)

Although has high comp pistons now

The block has 14 holes for each head, but is fitted with 10 bolt heads

These run standard small journal bearing as per 3.5 and 3.9

need4speed · Post by **need4speed** » Thu Nov 01, 2012 10:20 pm

Get Michigan or Vandervell bearings.

PLEASE UNDER NO CIRCUMSTANCES GET BRITPART BEARINGS FROM ISLAND 4X4

DEVONMAN · Post by **DEVONMAN** » Fri Nov 09, 2012 8:45 am

Hi Chuggernought,

What was the outcome of your bearing problem?
I assume you did not have to pay £160 for them.
Were the 3.9 type bearings suitable for your block?

It would be a first for me to hear of special thicker bearings that allow a 3.9 crank to fit in a factory 4.0/4.6 block.

I've never come across these and if they are available then they may be useful in a future project and it would be good if you could confirm either way.

Regards Denis

chuggernought · Post by **chuggernought** » Fri Nov 09, 2012 6:22 pm

hi been away a few days and not had a chance to strip the rest of the mains and mike up, plus some theiving scrote has broken into my workshop and nicked all my snap-on tools, £3500's worth, pissed off doesnt begin to describe it!!!!
but im guessing it is the middle shell problem above. i'm going to buy 2 sets of standard bearings( but need to wait until payday) and see what i can make up. will let you know the outcome.

mgbv8 · Post by **mgbv8** » Fri Nov 09, 2012 8:42 pm

need4speed wrote:Get Michigan or Vandervell bearings.

PLEASE UNDER NO CIRCUMSTANCES GET BRITPART BEARINGS FROM ISLAND 4X4

I'm pretty sure most of the small bits I've got from Island 4x4 come in Land Rover bags with the green logo ?

POAH · Post by **POAH** » Sat Nov 10, 2012 3:24 pm

thats an early interim block - later ones only had 10 bolts. both use 28cc heads with comp gaskets

softdash3.9 wrote:I have an interim 38D in my Range Rover Classic, cross bolt pads, with no bolts and non crossbolt main bearing clamps. (38D low comp 8.13:1 cr, 36D are 9.35:1 cr)

Although has high comp pistons now

The block has 14 holes for each head, but is fitted with 10 bolt heads

These run standard small journal bearing as per 3.5 and 3.9

POAH · Post by **POAH** » Sat Nov 10, 2012 3:28 pm

according to des hammils book the vast majority of late interim blocks have the large main caps of the 4.0/4.6 but the main bearing tunnel is machined for the small journal crank.

I've got a 95 disco late interim 3.9 in my 110.