Topic: Elite top end rebuild (Read 2748 times)

JamesV6CDX · « **on:** 19 March 2007, 20:59:37 »

I appreciate not all of you may agree with this as the best way forwards, but it is the way that I'm choosing. I can confirm that a manifold stud has snapped on the drivers manifold, and as such, due to lack of access, the head needs to come off to get at it.

And there's no point in doing just one head, is there

I'm going for the full top end rebuild.

Tonight I stripped out bagpipes, plenum, inlet manifold, coolant bridge, EGR, sec air injection, I've stripped a lot down in just under 2 hours, until the dark and rain came!

There are lots of deposits in the valley, and to be honest it wasn't put together totally well... so I'm going for the rebuild option.

Feel totally confident doing this, second time round now.

I will update this thread with pictures and things that I encounter

JamesV6CDX · « **Reply #1 on:** 19 March 2007, 21:00:32 »

At the same time, it will have new stat, new oil cooler, new HBV and a known good Rad from my 2.5

JamesV6CDX · « **Reply #2 on:** 19 March 2007, 21:02:19 »

And new water pump, cambelt kit, etc etc etc...

ClarCE · « **Reply #3 on:** 19 March 2007, 21:24:28 »

Quote

At the same time, it will have new stat, new oil cooler, new HBV and a known good Rad from my 2.5

All sounds good James, I'm envious!

I want to do my stat..

jonny2112 · « **Reply #4 on:** 19 March 2007, 22:45:13 »

Good luck James, and please do keep us posted. Pics would be great too, as you never know what's round the next corner with an Omega

Martin_1962 · « **Reply #5 on:** 20 March 2007, 10:45:55 »

So James what are the plans for....

Original 2.5
The LPG donor 2.0CD
The VGC 2.0GLS
The Elite

JamesV6CDX · « **Reply #6 on:** 20 March 2007, 11:03:50 »

Quote

So James what are the plans for....

Original 2.5
The LPG donor 2.0CD
The VGC 2.0GLS
The Elite

Original 2.5 - Rob for parts to sort out Elite, and scrap
LPG Donor 2.0CD is probably already crushed into the size of a shoebox
VGC 2.0GLS - Repair the gearbox
The Elite - Top end rebuild and MOT

Potentially sell the 2.0 when it's all finished, to pay for a brand new LPG kit on the Elite perhaps?

Martin_1962 · « **Reply #7 on:** 20 March 2007, 11:54:40 »

If you fit the gas kit to the 2.0 you should be able to get high hundreds, possibly even a 4 figure sum with all the toys and the economy.

It struck me as a good runaround car and after what was spent would be criminal to scrap.

Kevin Wood · « **Reply #8 on:** 20 March 2007, 12:22:05 »

Hi James,

Before you put the 2.5 heads on, I would try to measure the volume of the combustion chambers. If you get a sheet of clear plastic and locate it over one of the combustion chambers, make a hole in the centre and then drip water into it (taking note of how much you use) until the combustion chamber is full the volume of water will tell you roughly the combustion chamber volume.

To this you can add an estimate of the volume taken by the head gasket (bore area x gasket thickness).

I'm not sure if the pistons are flat topped or pocketed on the V6 but if the latter, add a guesstimate of the volume of the pockets.

Plug the numbers into the formula here http://en.wikipedia.org/wiki/Compression_ratio and see what compression ratio you're looking at, using the 2.5 head combustion chamber info and the 3.0 bore and stroke.

In fact, by rearranging the formula and knowing the original compression ratio of the 2.5 you probably don't need to measure it!

Cheers,

Kevin

Kevin Wood · « **Reply #9 on:** 20 March 2007, 12:42:00 »

Quick back of a fag packet calc says you'll be running 12.6:1

This is assuming the pistons on the 3.0 are roughly the same as the 2.5 and don't contribute more to the combustion chamber volume.

It'll certainly be a super unleaded job!

Kevin

Martin_1962 · « **Reply #10 on:** 20 March 2007, 13:54:08 »

No problem as he wants to LPG it and for running on gas stupid CRs work well

Kevin Wood · « **Reply #11 on:** 20 March 2007, 14:35:56 »

It'll be nice on LPG, with better power and economy than a standard engine, in theory. I don't know what it's going to be like on Petrol but hopefully the ECU's knock retard will prevent it killing itself.

Kevin

Martin_1962 · « **Reply #12 on:** 20 March 2007, 14:43:28 »

Well with Tesco 99. Shell and BP stuff - try it out

Auto Addict · « **Reply #13 on:** 20 March 2007, 17:36:30 »

Quote

Well with Tesco 99. Shell and BP stuff - try it out

Thought Tesco only went upto 97?

Marks DTM Calib · « **Reply #14 on:** 20 March 2007, 17:52:01 »

Quote

Quick back of a fag packet calc says you'll be running 12.6:1 This is assuming the pistons on the 3.0 are roughly the same as the 2.5 and don't contribute more to the combustion chamber volume.

It'll certainly be a super unleaded job!

Kevin

I got 12.75:1...so pretty high.....its actualy direct injection territory!

Marks DTM Calib · « **Reply #15 on:** 20 March 2007, 17:56:38 »

Heres my theory

Cr=((Pi/4)xb²xs+Vc)/Vc

A bit of simple alegbra gives:

Vc=((Pi/4)xb²xs)/(Cr-1)

Which using b=8.16cm and s=7.96cm (I use cm which goes against the grain a bit because I want Vc in cc's)
gives Vc = 42cc

Plug this value back into the original equation using the 3.0 bore and stroke and you get the Cr....

razzo · « **Reply #16 on:** 20 March 2007, 19:33:02 »

Oh i get it now, i think :-/ :-/ :-/ :-/ :-/

tunnie · « **Reply #17 on:** 20 March 2007, 22:11:42 »

Quote

Heres my theory

Cr=((Pi/4)xb²xs+Vc)/Vc

A bit of simple alegbra gives:

Vc=((Pi/4)xb²xs)/(Cr-1)

Which using b=8.16cm and s=7.96cm (I use cm which goes against the grain a bit because I want Vc in cc's)
gives Vc = 42cc

Plug this value back into the original equation using the 3.0 bore and stroke and you get the Cr....

riiiiiiiiiight then. :-/

I am sticking to computers!

sounds2k · « **Reply #18 on:** 20 March 2007, 22:20:07 »

Quote

Heres my theory

Cr=((Pi/4)xb²xs+Vc)/Vc

A bit of simple alegbra gives:

Vc=((Pi/4)xb²xs)/(Cr-1)

Which using b=8.16cm and s=7.96cm (I use cm which goes against the grain a bit because I want Vc in cc's)
gives Vc = 42cc

Plug this value back into the original equation using the 3.0 bore and stroke and you get the Cr....

OK ... so s=stroke (79.6mm) and b=bore dia. (81.6mm) ... what's x??? :-/

seeing that brings back memories ... of headaches!!!

theolodian · « **Reply #19 on:** 20 March 2007, 22:21:26 »

Quote

Quote
Heres my theory

Cr=((Pi/4)xb²xs+Vc)/Vc

A bit of simple alegbra gives:

Vc=((Pi/4)xb²xs)/(Cr-1)

Which using b=8.16cm and s=7.96cm (I use cm which goes against the grain a bit because I want Vc in cc's)
gives Vc = 42cc

Plug this value back into the original equation using the 3.0 bore and stroke and you get the Cr....
OK ... so s=stroke (79.6mm) and b=bore dia. (81.6mm) ... what's x??? :-/

seeing that brings back memories ... of headaches!!!

multiply

JamesV6CDX · « **Reply #20 on:** 21 March 2007, 14:02:05 »

Mark, in your wisdom, am I going to have any big problems putting the 2.5 heads on??

Marks DTM Calib · « **Reply #21 on:** 21 March 2007, 15:18:55 »

It will give you 'head' aches.....unless you want to build a race engine!

Plus you would want to use the 3.0 sodium filled exhaust valves any way.....

Marks DTM Calib · « **Reply #22 on:** 21 March 2007, 15:19:46 »

Quote

Quote
Heres my theory

Cr=((Pi/4)xb²xs+Vc)/Vc

A bit of simple alegbra gives:

Vc=((Pi/4)xb²xs)/(Cr-1)

Which using b=8.16cm and s=7.96cm (I use cm which goes against the grain a bit because I want Vc in cc's)
gives Vc = 42cc

Plug this value back into the original equation using the 3.0 bore and stroke and you get the Cr....

riiiiiiiiiight then. :-/

I am sticking to computers!

Tunnie, the ONLY thing a computer can realy do is computations......yes lots of them.....but its still maths!

JamesV6CDX · « **Reply #23 on:** 21 March 2007, 15:36:34 »

What sort of headaches mark, serious ones, or niggles?

Happy to keep the car on 99RON....

JamesV6CDX · « **Reply #24 on:** 21 March 2007, 15:37:12 »

also, what would it do to emissions....

Marks DTM Calib · « **Reply #25 on:** 21 March 2007, 15:41:29 »

In theory, the engine would require a higher octane fuel plus, the knock sensor is likely to retard the timing further....all to prevent pre-ignition.

More NOx would be created as a result of the higher compression but, in theory you should get better efficiency (you might struggle to actualy achieve this!)

The V6 (2.5 and 3.0) have a pretty high compression ratio already......

JamesV6CDX · « **Reply #26 on:** 21 March 2007, 15:43:35 »

NOx isn't measured on MOT is it?

Kevin Wood · « **Reply #27 on:** 21 March 2007, 16:38:11 »

Quote

NOx isn't measured on MOT is it?

No, but your biggest problem will be knock. Yes, the engine has knock sensors so it can theoretically cope but who knows how much timing adjustment the ECU will allow before it throws in the towel and goes into limp-home? Or maybe it will just lob in as much correction as it allows and yet still hole a piston?

Compression ratios this high are extreme even in tuned engines, and those generally have more aggressive cams which result in less VE in the medium rev range where knock can be a killer - meaning that the effective CR is lower until they hit high revs. They also generally have forged pistons at this level so are much stronger and able to cope with a little knock.

I think trying this with an otherwise stock setup where you can't adjust fuel and spark is asking for trouble - unless it has been tried before with success. It's an easy upgrade (just like 3.0 cams in a 2.5) so if it worked, people would be admitting to have tried it

(just like they do with 3.0 cams in a 2.5). The silence speaks volumes, IMO!

It would be a real shame to go to all the trouble and expense of a top end rebuild only to find out you've got an engine that doesn't run.

Kevin

JamesV6CDX · « **Reply #28 on:** 21 March 2007, 16:56:29 »

I agree with all of this logic... but... it's Sooooooo tempting to try it

theolodian · « **Reply #29 on:** 21 March 2007, 17:03:15 »

Quote

I agree with all of this logic... but... it's Sooooooo tempting to try it

If you're sure that you will be running LPG most of the time then the arguement changes.

JamesV6CDX · « **Reply #30 on:** 21 March 2007, 17:06:57 »

Quote

Quote
I agree with all of this logic... but... it's Sooooooo tempting to try it
If you're sure that you will be running LPG most of the time then the arguement changes.

I will most likely be running on Optimax most of the time, LPG won't be instant, if at all, given that I now only do about 20 miles a day instead of 100+ !!

Martin_1962 · « **Reply #31 on:** 21 March 2007, 17:07:10 »

What about 112 Octane rating?

JamesV6CDX · « **Reply #32 on:** 21 March 2007, 17:11:54 »

Quote

What about 112 Octane rating?

Imagine that must be LPG... but.. BP are now doing a 102 octane petrol!

Interesting when that gets local

Martin_1962 · « **Reply #33 on:** 21 March 2007, 19:26:04 »

Quote

Quote
What about 112 Octane rating?

Imagine that must be LPG... but.. BP are now doing a 102 octane petrol!

Interesting when that gets local

Yes it is - but 102 sounds interesting if you have the CR

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Author Topic: Elite top end rebuild (Read 2748 times)

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