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PostPosted: Sun Dec 05, 2010 12:50 pm 
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Location: The Vale, South Wales
Car Model: ST185 CS/RC
As this thread states I may actually, possibly, maybe doing something constructive to the CS at long last. I know that has come as a bit of a shock to those of you who know me but alas the rumours are true, plus I’m getting a right ear bending off Vicky lol.

Anyway all joking aside the CS has coming to it a fairly major overhaul and up grade to suspension, brakes and engine.
My aim for the engine is not to go for some silly outrageous power figure which turns out to be un-driveable, unreliable or unachievable but to get as close as I can to 300hp without drastically changing the concept, appearance and components within my CS engine, ie when you pop the bonnet the engine still looks standard.
I’m currently in the process of removing the head for inspection etc, etc, so what I’m looking at is my options for the four round up and downy things inside.

My options being,
1, de-glaze the bores and re-ring the current standard piston which I can do my self
Or
2, re-bore .5 over and fit the set of JE pistons I just happen to have lying around somewhere.

The issue I have with the re-bore is that I don’t have the luxury of being able to drop the block plus I’m reluctant to disturb the mains etc as they are in good shape so this will mean an in-place re-bore which then means getting the car to someone reputable or possibly a mobile engineer?
My preferred method would be to put the thing on a trailer (not an issue) and take it to a reputable machine shop and get them to re-bore the block in place. Who’s reputable?

I’m questioning what performance advantages I will gain throwing in the pistons and maybe a set of rods over just a hone and a new set of rings.
Anyone got any thoughts on this or what might be needed to get close to the 300hp figure and has anyone any idea of what sort of prices I’m looking at these days for a re-bore.

Cheers all Dorris

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PostPosted: Sun Dec 05, 2010 1:37 pm 
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Hi Dorris,
IMHO I don't like any of the options!
Working on the block and creating swarf without a thorough clean afterwards could lead to further damage and a short lived rebuild.

With the engine in the car I can't see a way that you can accurately measure the bore for ovality and banana shape-ness (can't remember posh word).

It may not be an issue as some of the measurements I have seen for ovality and banana grading have been so small to be within spec even after 100K miles, IIRC your engine has already been apart a few times so who knows?

My approach would be to pull engine and start with a known quantity, once bores are measured you actually have to fit larger pistons anyway and the decision will be made for you. If you overbore now to 86.5mm and then have issues you may make the block scrap unless you are happy you have enough meat for 87.0mm pistons (again need accurate measurement and now ultrasonic testing of block thickness.

I have not heard of a in situ rebore service (apart from people using very coarse hone for an extended period (which will not get rid of ovality or banana-ness IIRC).

For 300 bhp easy then I would stick a set of St205 cams in, hybrid turbo or ct20b. 300bhp is right on the boundary of the 440cc injectors capability. (If it were me I would be sticking in 540cc st205 injectors and an aftermarket ECU.) You would get your money back on ECU from increased MPG over time. You could look at a ST205 ecu conversion also. Or piggyback ECU. In any of the options you could keep the AFM in place for looks and convert to MAP based ECU.

I am sure someone who knows a lot more about engine building will be along to advise on best practice/faesability. I am a little anal with that stuff as I don't have enough experience/understanding of what short cuts can be used.

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PostPosted: Sun Dec 05, 2010 3:39 pm 
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I agree with JP, I'm not keen on those initial options.

Rebore - needs a machine shop. Take the minimum amount of material off to ensure the bores are not tapered or oval - possibly 0.25mm oversize. Bores need to be cut to the size of each individual piston, (pistons require measuring).

WHy do you mention rebore? If the engine is ok, then re-vamp the head and then turn the wick up a bit :) (Don't forget new valve stem oil seals :) )

Good luck!

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PostPosted: Sun Dec 05, 2010 4:54 pm 
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IMO unless the car is burning oil or down on compression then don't touch the bottom end.

I don't see any way of properly re-boring an engine in-situ as the block needs to be very firmly attached to the bed of the boring machine.

A light hone in-situ is not ideal but with extreme care and the right technique is achievable IMO. I'm doing mine soon so I may end up eating my words :lol: I'm planning to leave the pistons in the bores but with conrods detached from crank and dropped down below normal lowest point, then seal round the perimeter with blu tac. Also covering over the block top with sticky tape a-la operating theater. Once finished, clean the bores then remove the pistons and clean the whole lot further.

IMO forged pistons are un-necessary for 300BHP unless you're planning on giving it serious rough treatment and running without knock control.

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PostPosted: Sun Dec 05, 2010 7:57 pm 
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ive built a few engines over the years an in my opinion i would never dream of doing anything to the bottom end in situ. it only takes one piece of swarf or dirt and your dropping the block anyway. if you have the skill to pull the head then why not borrow/hire a engine hoist an do the job properly. or leave it as it is and build another engine to your spec. :lol:


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PostPosted: Sun Dec 05, 2010 8:18 pm 
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Dorris,

but why?

i would pay for a leak down & compression test
i would inspect bottom end and look at big ends and mains
i would decoke the clinderhead, new valve stems, relap valves, reshim etc to restore lost power


...but i would NOT rebuild rebore deglaze unless there was an issue your not telling us.

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PostPosted: Sun Dec 05, 2010 10:06 pm 
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p.s. in my case, ringlands have failed for a second time, block is scored, the car is basically only used for competition (low speed, high power). Not fussed about it being perfect as long as it lasts another season. If the engine comes out, it won't be going back in.

As I said, if there are no issues better to leave it alone, bodging will probably make it worse. If you want a long lasting engine do it properly.

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Last edited by Nibbles on Sun Dec 05, 2010 10:07 pm, edited 1 time in total.

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PostPosted: Sun Dec 05, 2010 10:07 pm 
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Location: The Vale, South Wales
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I do like it when you guys speak sense and give me a little slap, was a silly idea I know doing machine work with things still in situ but I was sort of pre-empting just in case really as the reason the car came off the road in the first place was because it was badly smoking when changing gear and what with all the other nif naf problems and oil leaks etc.

A quick up date, I got the head off today and think I might of found the culprit, number three right hand exhaust port is very wet and oily so my opinion is that the valve stem seal has popped, whether this is the only problem is yet to be confirmed.
I've not had chance to have a proper look at the bores or head yet but as you can imagine everything looks a bit black, oily and messy so I guess I’ve a lot of cleaning to do first and don’t worry I plan on being very cautious whilst cleaning.

Last time the CS was put on the RR it was kicking out 242hp with a blowing manifold, some inaccurate boost and some seriously eye watering over fuelling so with all them issues addressed the thing should start to behave its self.

The problem I’ve always had with the CS was the previous owner or more what he had done or not done whilst cruising around with his ASBO sound system in the boot. I’ve addressed all the big problems to get the car on the road after I bought it but it has now got to the stage where all the little problems are becoming big problems and the car is starting to look a little sorry for its self being sat around for a while. I have a boot and garage full of GT4 goodies to be fitted that I’ve been collecting over the last couple of years so I think its time to get busy and get this beastie back on the road and looking good again. D

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PostPosted: Sun Dec 05, 2010 10:10 pm 
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Was the car drinking oil ?

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PostPosted: Sun Dec 05, 2010 10:28 pm 
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No so much drink the oil but more throw it everywhere. I remember the exact moment it happened, I was half way down the M3 slip road coming off the A43 and running late so the foot was to the floor when I got a mist up the left side of the windscreen, thinking it was water I put wipers on and it soon became apparent it was oil. When I stopped I popped the bonnet to have a look I found it was oil spraying out my manual boost controller, cut a long story short the crank case was getting pressurised so initial fears was some sort of cylinder/ring damage but a popped exhaust valve stem oil seal would also make sense. I think first things first get everything cleaned up and checked out and take it from there. D

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PostPosted: Mon Dec 06, 2010 12:41 am 
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Those symptoms scream piston ring/ring land failure to me. Valve stem wear/seal wear would normally only result in a smoky exhaust. I can't see any way this would result in pressurising the crankcase. For planning purposes I would assume that at the very least you would need new pistons and rings. The bore may be OK but you will only be able to confirm this by getting it measured by a machine shop.
BTW I'm sure we've had this conversation before :lol:

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PostPosted: Mon Dec 06, 2010 1:12 am 
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Agree with Don. No way you'd get that much gas up a valve guide even if a seal has gone.
I suspect you'll see some scoring in a bore from broken ring or ringland.

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PostPosted: Mon Dec 06, 2010 11:40 am 
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Chris-de-Bear wrote:
Agree with Don. No way you'd get that much gas up a valve guide even if a seal has gone.
I suspect you'll see some scoring in a bore from broken ring or ringland.


Having heard Dorris' tales of "giving it large" I suspect that the sustained "pedal to the metal and the thing to the floor" style of driving I have heard about from him I also suspect ringland departure :-)

That's not a dig Dorris - these things are meant to be driven (Doh - own goal). However sustained high speed and full chat runs are likely to lead to detonation on a standard engine - maybe a case for forged pistons afterall if you intend to continue to drive it like your pants are on fire :-)

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PostPosted: Sat Jan 29, 2011 1:13 am 
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Ok quick up date and as ever you guys are right, ring land failure and broken ring on number three, will get some pictures up later, I had a hunch something was wrong with number three as the big end was on the point of failing again, the big ends have only had twelve months use.
I’ve already got the front suspension down and won’t be long before I drop the block and transmission. Dorris

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PostPosted: Sat Jan 29, 2011 12:09 pm 
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Sorry to hear of your woes Dorris... I'm sure a man of your calibre will sort the problem :)

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