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Just Done A Compression Test On The 2.5-16; Results, and opinions? Dear friends? lol
Topic Started: Wed Mar 26, 2008 8:47 pm (1,316 Views)
Martrider
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Longest build time in history?
Evening all, just completed the compression test on the 2.5-16 and some strange results.

Im hoping that quite a few of you will let me know your opinions on the results. These are the results of both a dry and wet test, didn't appear to make any difference what so ever. What does this mean in particular?

Cylinder 1: 160 psi

Cylinder 3: 120 psi

Cylinder 4: 155 psi

Cylinder 2: 160 psi

I can't remember if i told you lot or not, but I snapped a half shaft on the way back from work the day i was retiring the red one, i am now driving a Volvo so no rush on sorting it out, luckily, because it looks like it's going to cost me a lot more than i though and be a lot longer winded!

Oh, and i also changed the oil, new filter, half a pint of diesel and flushed through, got one more to do before i start the proper strip down.

So what do you think?

Cheers,

Mart ;)
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Lewis 190E 2.5 16
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W201
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Well, 1,2 and 4 are about right...
Could be alittle higher circa 170.

But no.2 is too low, piston rings prehaps on that cyl...
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cossie connoisseur
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there can be only one ;-)
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for staters you will be suffering with engine inbalance which means you will have a vibrating engine(similar to if an engine mount is out)

now i was driving my car with figures of;

115
112
92
87

and it ran like a dog

could be rings, but is probably valve wear from petrol wash. very common and also varys per cylinder.

car is still usable in my mind but i would have it at the back of my mind that the car is sick which aint nice when driving her.

it could well be the rings but only one way to find out!
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Lewis 190E 2.5 16
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cossie connoisseur
Mar 26 2008, 07:53 PM
it could well be the rings but only one way to find out!

Yes....
Head off time...

Could also be leaking valves, head gasket, valves not seating correctly etc...
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Big Ben
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Most probably valve seats and guides. Not at all unusual and normally the result of running with a bad mixture. It will only get worse if its not addressed. Get the head reworked and the mixture set up properly and you will notice a marked difference in performance!
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Martrider
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I know it's head off time, thats why i did the test while the engine was still in the car so i could get some figures to work on. One more flush and it will be removed. Not this weekend though as i am going to Donnington for a big Lotus show!

Anyway, the car isn't useable anyways as it has no front end, no windscreen, drivers door, and lots of dents etc... lol

Obviously i realise there is a problem, is it common for this cylinder to be more tempremental?

Would somebody mind posting the workshop book figures? I am brand new to the 2.5-16. I need to get myself a copy of that CD i think!

CC: Why do you mention an imbalance? Just caused due to lower compression on one?

Lewis: All of the above will be covered anyway when i get the head rebuilt/freshened.

The big questions is, and i have few conflicting thoughts so far, do i sort the bottom end out at the same time?

Some say it is better left untouched, some say do it as a matter of course. So far there are 3 people in each camp!

Thank you guys.

Mart ;)

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Big Ben
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Nicks figures were far worse than yours but doing the head bought them back to identical across all four. The engine is a lot smoother and has lost all sorts of weird vibrations (even the gearbox was making strange noises before the head work!). Imagine an engine running towards three cylinders and that's what you have with your compression figures! The bottom end is remarkably strong on the 16 valvers and I would really be surprised if the rings have gone!
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Martrider
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I think i should have added on the first post just in case anybody didn't know. Would link to my "Im back" thread from a couple of weeks ago

This is not my daily driver, it is a work in progress to produce a road/track car with bike-carbs. So set-up will be of course looked at all the way through.

Original project thread if anybody is interested?


Big dreams - They have got bigger since!


Being chucked off the computer, i'll be back in a bit. lol
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Desmoboy
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What do you mean by "wet test" , if it means what i think it does, pouring oil down the bores. If this makes no difference as you said then its not likely to be rings/ bores. More likely to be poorly seating valve on that cylinder.
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merc190uk
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The Godfather

Desmoboy
Mar 26 2008, 09:32 PM
What do you mean by "wet test" , if it means what i think it does, pouring oil down the bores. If this makes no difference as you said then its not likely to be rings/ bores. More likely to be poorly seating valve on that cylinder.

yep what he says :D

wet test and no change says rings are good.

or so i was taught :unsure:
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Martrider
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It's the only thing that makes logical sense so don't worry Steve, you're right. lol

So along with the headwork.......
What should i do while it's apart?
Dare i mention cams? Although i have a feeling that if combined with Bike carbs might be a bit too fruity for the road!! lol

I have the perfect engine in my head, but it's a daily/track engine of maahoooooosieve proportions.

But is there that feint fume of "Go big or go home" in the air? lol

Make it stop? Make the madness stop?!?! ;)

Mart ;)


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dave_irl
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Glad to see you finally got the finger out :P

Welcome to my world!! Whats this "go big" about?? I reckon see the R1-16 through first.. And you can never have too lairy a cam for the road. Ever! Uber lumpy tickovers are cool :D

PS A bottom end freshen up cant hurt, although it would slow the project down a little.. But if time is your friend, then why not? at least you'd know its done. 4:3 to the crankjob lol
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Neil
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Martrider
Mar 26 2008, 09:56 PM
I have the perfect engine in my head, but it's a daily/track engine of maahoooooosieve proportions.

But is there that feint fume of "Go big or go home" in the air? lol

:lol: :lol: :lol: You boys crack me up.

Mart, I think it is widely known as being on the 'slippery slope'.
A similar thing happens when you fit 17 or 18-inch wheels to a bog-standard car.
Next thing you know, you've bought:

New Shocks
New Springs
New Wheel Bearings
New Spring Pads
New Anti-Roll Bars & Bushes
Adjustable Camber Arms
Bigger Brakes
Braided Brake Hoses
New Steering Wheel
Momo/Sparco Pedals
Matching Gearknob

You may be able to see where this is going :lol: :lol: :lol:
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carl mcgraw
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Martin, you know what you have to do.. ;-D
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Martrider
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I thought i would ressurect this thread temporarily, after reading more on the forum recently - to ask the question about shimming.

Could this be the first port of call for the case of this engine?

It wasn't particularly rattly when the engine was running, the only thing i am worried about is that if i do this, i will now know the differenct until the engine is back up and running, but by then it will be on bike carbs.

Just wondered if i could gauge opinion.

Thank you all,

Regards

Mart ;)
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Uk Merc Man
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190e Leg-End
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personally, i think those results lean towards a valve train issues - possible gaps. usually, a wet test would improve the results if the bottom end was at fault.....just imo obvioulsy....
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Martrider
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So it could just need the valves re-shiming and having a look at. Timing chain was deon fairly recently and the cams are in good condition, seems a shame they didn't do this at the time.
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Big Ben
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Shimming is a good starting point as its the cheapest option. If the problem persists then its head off time to check for wear!

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Martrider
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Sounds like a sensible course of action. ;)
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jeremy
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Sorry to rub it in , But I had mine done yesterday .....
cyls 1/2/4 = 170
cyl 3 = 175

Jeremy
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RobertE
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Sounds spot on, I recall that Original C/R was 12 bar (?) which is c. 180 psi.
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Johnboy Mac
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RobertE
Thu Aug 6, 2009 8:21 am
Sounds spot on, I recall that Original C/R was 12 bar (?) which is c. 180 psi.



The compression spec. is pinned in the Engine section.
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Martrider
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That sounds excellent Jeremy, looks like i have a bit of work to do. Considering a blueprint while it's open, depending on the results of my meeting on Monday.
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