My 4.6 V8 Rebuild Thread

[101RRS]

Yesterday I got the block and crankshaft back. The block has had the damaged stud hole all repaired (I hope), a hone and the block decked.

Work on the crank showed that number 5 big end had "picked up" a bearing meaning the big end journals needed to be ground down so will need first oversize bearings - the mains just needed a polish.

Oh I have decided to put the 4.0 pistons on the 4.6 rods so this will give me a compression ratio of about 9.1:1.

So first question - is there any advantage is sourcing bearings from the UK or is local OK?

When the bottom end is together, that will lead me into what camshaft. (when I order the bearings I will order a twin chain cam chain and maybe a cam). I have decided to go a mega jolt ignition (or mega squirt injection/ignition) so I will not need a dizzy so could use the original 4.0 cam which has only done low km and is in good condition. However not sure. I do not need an increase in low end torque but mid range - 2-3000rpm.

So second question - seeking advice on whether to stay with the original 4.0 cam or should I source a performance cam to assist in giving an increase in torque in the midrange. If I should get another cam where is the best place to source these.

Third Question - I need to de carbon the 4.0 pistons - what is the best way to do that - was thinking using my Dremel with the little 1" wire brush in it. Should be strong enough to lift the carbon but not damage the metal.

Thanks

Garry

[bee utey]

My favourite decarboning tool was the blunt (curved) end of a stainless steel 6 inch ruler. However an auto store should have gasket remover discs, never used them myself but I believe they are like scourer pads to fit to your power drill.

Also break an old ring in half to clean the ring grooves. Wear gloves when doing this, the rings have sharp edges.

[Hoges]

Yesterday I got the block and crankshaft back. The block has had the damaged stud hole all repaired (I hope), a hone and the block decked.

Work on the crank showed that number 5 big end had "picked up" a bearing meaning the big end journals needed to be ground down so will need first oversize bearings - the mains just needed a polish.

Oh I have decided to put the 4.0 pistons on the 4.6 rods so this will give me a compression ratio of about 9.1:1.

So first question - is there any advantage is sourcing bearings from the UK or is local OK?

When the bottom end is together, that will lead me into what camshaft. (when I order the bearings I will order a twin chain cam chain and maybe a cam). I have decided to go a mega jolt ignition (or mega squirt injection/ignition) so I will not need a dizzy so could use the original 4.0 cam which has only done low km and is in good condition. However not sure. I do not need an increase in low end torque but mid range - 2-3000rpm.

So second question - seeking advice on whether to stay with the original 4.0 cam or should I source a performance cam to assist in giving an increase in torque in the midrange. If I should get another cam where is the best place to source these.

Third Question - I need to de carbon the 4.0 pistons - what is the best way to do that - was thinking using my Dremel with the little 1" wire brush in it. Should be strong enough to lift the carbon but not damage the metal.

Thanks

Garry

Re Third question:
went through this relatively recently. I bought a can of Lanotec Citrus degreaser, squirted a small amount on the crown of the piston, let it soak for a couple of minutes and then (wearing "hercules blue gloves") scubbed away with a green plastic pot mit (couple of dollars for a pack of 6 from Woolies).

Took about 10 minutes to clean each one up like new. I then rubbed some singer sewing machine oil over the piston and around the cylinder and moved onto the next one... worked well.

[clubagreenie]

On the dremel use (or make) some scotchbrite pads rather than the wire. The wire on alloy may still mark it, which would have negligible effects but I'd prefer not to. +2 about the broken rings to scrape out the lands.

Just a small point, but one that leads to potential for part ordering errors, usually because the knobs you buy from order exactly what you ask for without checking (what should be impossible). Your bearings, if it's the crank side will be one size LARGER, due to the crank being ground smaller. You should be able to hopefully go down by 0.0005thou, but if it needs more than 0.0010" on damage I'd have the crank inspected/x-rayed.

With the cam, try speaking to Mark Adams , he's been around tuning them for quite a number of years and is the only known person to successfully crank and re-chip D2 ECU's so he should be able to give some advice. I'd be interested in knowing the details and maybe able to split shipping if it's a reasonable price and they have something for both of our needs.

A bit slightly left of centre, what side of the crank journal is damaged? If looking at the journal when raised in relation to the rotation (i.e. at TDC for the cylinder in question), is it the side, upper face or lower face? What I'm suggesting will lower the piston by about 0.0005" if going to 0.0010" undersized. Have them offset grind the crank so you move the journal back towards the centreline of the crank. This will do a number of things (normally I'd reserve this for a performance $$$$$ build to achieve assisting in doubling (or more) the rev capacity of the rotational mass but since you need it ground anyway) moving the rod closer to the centreline of the crank reduces the rod angle and so reduces the load on the piston against the side of the bores (where you see the piston polished on the skirt) which in turn can also allow you to run shorter skirt or even skirt-less pistons and in this case it ever so slightly (in other cases I've done up to 3mm) reduces the stroke (which I've previously regained in bore) which increases it's rev capacity and response times.

I realise it's a bit to take in and in your case make little change but I believe in reducing loads, friction and wear as much as possible and if it's part of the process you have to undertake and it means only giving different instructions to machinists then why not.

[101RRS]

Just a small point, but one that leads to potential for part ordering errors, usually because the knobs you buy from order exactly what you ask for without checking (what should be impossible). Your bearings, if it's the crank side will be one size LARGER, due to the crank being ground smaller. You should be able to hopefully go down by 0.0005thou, but if it needs more than 0.0010" on damage I'd have the crank inspected/x-rayed.

The engine rebuilder has indicated that he reduced big end journals by 0.0010" so first oversize bearings will be required so i will just order accordingly and measure them when received to ensure they are correct.

With the cam, try speaking to Mark Adams.

Sorry - who is Mark Adams??

A bit slightly left of centre, what side of the crank journal is damaged? If looking at the journal when raised in relation to the rotation (i.e. at TDC for the cylinder in question), is it the side, upper face or lower face? What I'm suggesting will lower the piston by about 0.0005" if going to 0.0010" undersized. Have them offset grind the crank so you move the journal back towards the centreline of the crank. This will do a number of things (normally I'd reserve this for a performance $$$$$ build to achieve assisting in doubling (or more) the rev capacity of the rotational mass but since you need it ground anyway) moving the rod closer to the centreline of the crank reduces the rod angle and so reduces the load on the piston against the side of the bores (where you see the piston polished on the skirt) which in turn can also allow you to run shorter skirt or even skirt-less pistons and in this case it ever so slightly (in other cases I've done up to 3mm) reduces the stroke (which I've previously regained in bore) which increases it's rev capacity and response times.

You have lost me a bit there - I do not know what side of the journal was damaged (just a scrape mark). Surely if the new bearings are thicker by exactly the same amount that has been taken off the big end journals then the piston will remain in the correct position. Has already been done so I need to use it as now ground.

Thanks for your advice and information - I appreciate it.

Garry

[Davo]

I've used neat CT14 on pistons and it worked very well, very quickly, but it can eat ally so you must rinse it off right away. I wouldn't ever use any sort of a metal brush on a piston as they can scratch very easily.

For a cam, I'd contact a few companies for a custom grind as you have a very particular and unusual use for this motor.

[chazza]

So second question - seeking advice on whether to stay with the original 4.0 cam or should I source a performance cam to assist in giving an increase in torque in the midrange. If I should get another cam where is the best place to source these.

Don't know about the best place, but give Crow cams a ring; they have an excellent reputation with the mechanics I know! Crow Cams

Cheers Charlie

[101RRS]

Thanks - Crow is on the list so I will give them a call - would prefer to use the standard cam but I am not sure how it rates and whether an aftermarket cam will make a lot of difference - was hoping for some experience on AULRO.

I once spent quite a few dollars on a hi performance cam for a Subaru 1800 once and it really made little difference so am a bit weary.

Cheers

Garry

[Pedro_The_Swift]

The D2 already has a very low max torque rpm,,
going to a 4.6 with the standard cam should give you, what 20% (?) more at the same revs,, 9.1 should bump the other up too,,
how many revs at 100kph Gary?

[clubagreenie]

An aftermarket cam might just be a bit harder and last a bit longer to.