Compression tests...

jimberlake

jimberlake

0
Hi all, hope you can help here. was wondering about the compression on the Commers. To be honest the engine appears to run well but it does breathe a bit through the oil cap once warmed up so I thought I'd do a compression test and stick a USB cable camera down there, a must have accessory, cheap at £14.99 off Ebay. 2 metres waterproof, 7mm width and 4 adjustable LED lights on the lens with a photo or video button on the cable perfect for down the spark plugs.
Anyway - its an alloy head HC and I got 135,125,115,115. The two higher ones were quite sooted (running rich) and the two 115's were burning perfect. Doesn't appear to burn oil or smoke from the exhaust.

Whats people opinionsexperience on compression being so different, is it an acceptable difference or on the limit? I think HC should be 150-170 according to the book.

Runs ok so should be ok for the Summer before I re-ring it over Winter. However looking at the bores and valves could people give an opinion as I've never seen random scratches, maybe its normal? There is a bit of a vertical score also that you can see. I've included one pic but all bores were the same, also does the valve look ok or think may need a re-seat? Going to add oil next time I'm out there to see if it is the rings or valves, didn't get time last weekend as removed the gearbox.

Calling on peoples vast experience of Commers as I'm a 70's Japanese car man normally running Toyotas.

Thanks chaps

Bore
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Vavle
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Hasta la supervista baby
 
It looks like honing marks on the bore which would suggest the bores are OK. It could be that the rings have gummed up with lack of use or they are worn - I recently re-build my ally head engine and found the bores perfect but rings needed doing (it breathed a little heavy as well) The valves could do with a de-coke too.

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Summer's Coming
 
Does sound a little low on the figures. Next time it's off the road pull the head and re-seat/replace the valves and check the bores :)

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"You,re only supposed to blow the bloody SLIDING doors off"
 
Thanks guys, I'll whip the head off next time I'm there. Was thinking of getting it unleaded anyhow so might be a good opportunity to do the lot then. I guess I'll need to pop the pistons out to check the ring condition. I guess checking the bores would be for roundness and the size?

Hasta la supervista baby
 
Why dont you stop faffing and making yourself work. Just get your gearbox back in,get in the van and drive it!! With all the honing marks on the block it looks to have had a recent set of rings/pistons maybe, that may need to bed in a bit.If the rings are new it will breathe heavy if it hasnt been run in. Problen is todays oils cling to everything and make running old engines in a pain.

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A commer with even bigger boost will be appering on a screen near you soon!
 
quote:
Originally posted by jimberlake

I always do this, a little knowledge is a dangerous thing :)

Hasta la supervista baby



Stop stressing get in it and go camping and relax. It's a Commer and will never be a Rolls Royce no matter how much time and money you spend on it. As long as the pistons go up and down and it moves itself along under its own steam without over heating your doing well. Now stop messing about with cameras get that interior made put a bed in and sleep under the stars ;)

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A commer with even bigger boost will be appering on a screen near you soon!
 
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