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Badly Scored Cylinder
#1
Photo 
Hi there, 

I was wondering if anyone might be able to tell me whether my block is scrap...

I've took the valve chest cover off to see what the clearances were, they varied from 0-10 thou. 

I took off the head to see if the valve seats were burned and they appears to be ok, coked a little but not blue. 

I then noticed that the no.4 cylinder is very deeply scored from top to bottom, both front and back of the cylinder respectively, where the gudgeon pin is. 

I know nothing about the internals of this engine other than the pistons say 58.00 and measure 2.280 inches (+80). 

Are these Renault 4 pistons? If they are does that mean I've got a 1.5" crank and Renault rods too?

I don't think that I can put this engine back together knowing about these score marks. It was running very under powered and producing a lot of smoke. 

Do I need a new block or could I get away with a liner? Photo attached.

Any advice would be greatly appreciated  Smile

Thanks!


Attached Files
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#2
Hi, you could have the block linered, liner od is around 59 mm so you could not go back to 58 mm.
If you want the extra capacity get another block, if you are happy with 747 cc then liner back to standard, but would be more expensive than getting another block.
The fact that it is 58 mm is not indicative of it having Renault pistons,as you can get A7 ones that size.
The Renault rods have press fit small ends so unlikely the pins would have moved and scored the bore, only way to know for sure is to pull the block off.
I have Spare 58 mm block if you are interested. gene.h@hotmail.co.uk
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#3
You’d need to take the pistons out to find out if they are R4 or not.
Really you should consider the state of the rest of the block. I’d be surprised if lack of power is caused by that score, unless it’s partially seized, too. If the other bores are ok, you could fit a liner to just that bore. I’d make sure I was using 3 ring pistons (no ring below the pin), and get them to fit a liner to just slightly more than the depth of the lowest ring. That way you preserve as much block strength as possible - the wall next to the crankcase flange will be very thin with a +80thou liner. It works, I’ve done it and used such a block for several racing seasons, and in the end it wasn’t that that failed. However if you need to do more cylinders I’d start to worry, at that stage a new block would probably be cheaper anyway.
Alan Fairless
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#4
(07-04-2018, 04:44 PM)Alan Wrote: You’d need to take the pistons out to find out if they are R4 or not.
Really you should consider the state of the rest of the block.  I’d be surprised if lack of power is caused by that score, unless it’s partially seized, too. If the other bores are ok, you could fit a liner to just that bore. I’d make sure I was using 3 ring pistons (no ring below the pin), and get them to fit a liner to just slightly more than the depth of the lowest ring. That way you preserve as much block strength as possible - the wall next to the crankcase flange will be very thin with a +80thou liner. It works, I’ve done it and used such a block for several racing seasons, and in the end it wasn’t that that failed. However if you need to do more cylinders I’d start to worry, at that stage a new block would probably be cheaper anyway.

The no.1 exhaust valve clearance was closed up completely so I think it wasn't seating properly, so that might account for some power loss too. I couldn't identify where the smoke was coming form and realise now that it may have been coming from the valve chest breather if the gasses were escaping down these large grooves. 
Next step is block off and see what horrors lie inside... 
Thanks for getting back to me! W
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#5
William's failed to mention as he has done on the Austin Seven Facebook group page that this is to use his words "a powerful blown engine" and he doesn't wish to lose any performance.
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#6
(07-04-2018, 07:32 PM)Jeff Taylor Wrote: William's failed to mention as he has done on the Austin Seven Facebook group page that this is to use his words "a powerful blown engine" and he doesn't wish to lose any performance.

Ah... yes minor detail I forgot to mention - sorry! It’s a GM mk22 blower on a grasshopper drive. Trials engine designed to compete in MCC trials. It should go like stink but it’s very underpowered and smoky.
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#7
In which case I wouldn’t bugger about. Get a new block.
Alan Fairless
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#8
Hi Wills,
At this stage if you did not Build the Engine your self and are wanting to compete in some form of motor sport.
my suggestion would be to completely strip & rebuild, as you appear to have more than one problem that way you will know what you have .
this will take time but worth it in the end.

Colin
TINOPAI NZ
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#9
(07-04-2018, 04:19 PM)Wills Wrote: Hi there, 

I was wondering if anyone might be able to tell me whether my block is scrap...

I've took the valve chest cover off to see what the clearances were, they varied from 0-10 thou. 

I took off the head to see if the valve seats were burned and they appears to be ok, coked a little but not blue. 

I then noticed that the no.4 cylinder is very deeply scored from top to bottom, both front and back of the cylinder respectively, where the gudgeon pin is. 

I know nothing about the internals of this engine other than the pistons say 58.00 and measure 2.280 inches (+80). 

Are these Renault 4 pistons? If they are does that mean I've got a 1.5" crank and Renault rods too?

I don't think that I can put this engine back together knowing about these score marks. It was running very under powered and producing a lot of smoke. 

Do I need a new block or could I get away with a liner? Photo attached.

Any advice would be greatly appreciated  Smile

Thanks!
As stated elsewhere, with such equipment and use, anything, other than a full rebuild is not the way to go.
Short cuts rarely work and the long term reliability is always going to be suspect.
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#10
I'd agree with Colin and Nick,there is no way you can short cut on an engine like this.Not sure what your blower is (Roots type?)Is it any good,it could be taking as much power to drive it as it produces.Is  drawing oil though the s/c causing it to burn oil?
I've never done MCC trials but your car will need to be well engineered and tough if you want to finish.
Where is your supercharger fitted ?
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