Grif 500 Compresion Test good results?
Discussion
Mine were done by Mark Adams when he was fettling the ECU chip!!
He seemed to think that they were quite good as they were all fairly evenly matched
They came out as:
No.1 - 160 No.2 - 157
No.3 - 153 No.4 - 157
No.5 - 155 No.6 - 155
No.7 - 150 No.8 - 157
The engine had done about 17000 miles then
It gives you a rough idea to start with,
mack
He seemed to think that they were quite good as they were all fairly evenly matched
They came out as:
No.1 - 160 No.2 - 157
No.3 - 153 No.4 - 157
No.5 - 155 No.6 - 155
No.7 - 150 No.8 - 157
The engine had done about 17000 miles then
It gives you a rough idea to start with,
mack
Sorry if i am hijacking your thread but i just did did a compression test as a process of elimination with a detonation problem i am having and got these readings:
Readings in psi
No.1 - 150 No.2 - 125
No.3 - 100 No.4 - 120
No.5 - 150 No.6 - 150
No.7 - not checked No.8 - not checked
Reading the bible Steve says it should be 150-250 lb although it doesnt say what would be a tolerable variation in compression between cylinders.
Would No.3 be low enough to be causing me a problem?
Readings in psi
No.1 - 150 No.2 - 125
No.3 - 100 No.4 - 120
No.5 - 150 No.6 - 150
No.7 - not checked No.8 - not checked
Reading the bible Steve says it should be 150-250 lb although it doesnt say what would be a tolerable variation in compression between cylinders.
Would No.3 be low enough to be causing me a problem?
bluebottle said:
I thought it may be impending disaster,
Car is now booked into Dulford's as they are pretty certain its the camshaft :-(
thanks for the advise chaps
Hamish, once they've checked it out would you post the result on here, please? If it is the camshaft I'm intrigued to know how.
supprised.
poor compression has to be rings/valves(heads) i would have thought. they're leaking, either past the rings down the bores or past the valves.
consistancy is the key...+/- 10 = VERY good?
andy
not sure how the camshaft would affect it unless it was keeping the valves open, had shagged the valves (lateral movement.
suppose it could be closing the inlet too soon?
anyway...good luck!
poor compression has to be rings/valves(heads) i would have thought. they're leaking, either past the rings down the bores or past the valves.
consistancy is the key...+/- 10 = VERY good?
andy
not sure how the camshaft would affect it unless it was keeping the valves open, had shagged the valves (lateral movement.
suppose it could be closing the inlet too soon?
anyway...good luck!
[quote=Guillotine]supprised.
poor compression has to be rings/valves(heads) i would have thought. they're leaking, either past the rings down the bores or past the valves.
(quote]
Or head gasket I suppose? You'd probably have other signs as well like oily stuff in the water and/or steam coming out the exhausts and high water consumption.
poor compression has to be rings/valves(heads) i would have thought. they're leaking, either past the rings down the bores or past the valves.
(quote]
Or head gasket I suppose? You'd probably have other signs as well like oily stuff in the water and/or steam coming out the exhausts and high water consumption.
red griff 500 said:
[quote=Guillotine]supprised.
poor compression has to be rings/valves(heads) i would have thought. they're leaking, either past the rings down the bores or past the valves.
(quote]
Or head gasket I suppose? You'd probably have other signs as well like oily stuff in the water and/or steam coming out the exhausts and high water consumption.
true, non of these symptoms mentioned...yet!
Won't know for certain until monday morning, but i did question their theory and was told the following;
With low compression figures if you have a knackered cam lobe on the inlet port, the inlets valves can open late reducing the volume of gas in the chamber before it is compressed - sounded plausable to me, but a compression leak down test will confirm this theory.
This and the list of other symptoms and noises are what is leading them to this conclusion, and as Giullotine has pointed out non of the usual water, steam & oil issues associated with head problems seems to be pressent.
I will update you all on monday when they do their tests and start stripping down the engine.
>> Edited by bluebottle on Thursday 27th October 09:18
With low compression figures if you have a knackered cam lobe on the inlet port, the inlets valves can open late reducing the volume of gas in the chamber before it is compressed - sounded plausable to me, but a compression leak down test will confirm this theory.
This and the list of other symptoms and noises are what is leading them to this conclusion, and as Giullotine has pointed out non of the usual water, steam & oil issues associated with head problems seems to be pressent.
I will update you all on monday when they do their tests and start stripping down the engine.
>> Edited by bluebottle on Thursday 27th October 09:18
oooooooooohhhhh dear!
Well my engine has now been turned into 200 plus shiny oily ornaments.
Well, would you like the short answer or the long answer?
The short answer...everyone was right
The long answer;
2 cylinders were leaking past the exhaust valves, two cylinders leaking past the piston rings and one of my low compressions passed the leak test which subsequently turned out to be round cam lobes, and i do mean round. I doubt the inlet valve was opening at all, it the worst cam wear they have ever seen.
Well my engine has now been turned into 200 plus shiny oily ornaments.
Well, would you like the short answer or the long answer?
The short answer...everyone was right
The long answer;
2 cylinders were leaking past the exhaust valves, two cylinders leaking past the piston rings and one of my low compressions passed the leak test which subsequently turned out to be round cam lobes, and i do mean round. I doubt the inlet valve was opening at all, it the worst cam wear they have ever seen.
Thanks Guillotine, heres a full roundown of what they found wrong with the engine;
The heads look as tho they have had some additional time spent on them as they are ported and gas flowed very nicely, so re-ground seats and the heads are good to go(I did note that some of the valve seats did have some minor recession ridges).
Piston bores need re-honing and a new set of rings & seals required, one bore is quite badly scored but given the lack of lobes on the cam its hardly surprising (it looks more like a rolling pin now)
The big end shells need replacing but the crank appears to be unscathed. Both exhaust manifolds are scrappers as is the duplex cam chain.
It was rather depressing watching the engine coming apart and seeing just how bad it all was, but fascinating and enlightening watching the masters at work.
Not going to be cheap, but boy am i going to have well sorted engine next week
The heads look as tho they have had some additional time spent on them as they are ported and gas flowed very nicely, so re-ground seats and the heads are good to go(I did note that some of the valve seats did have some minor recession ridges).
Piston bores need re-honing and a new set of rings & seals required, one bore is quite badly scored but given the lack of lobes on the cam its hardly surprising (it looks more like a rolling pin now)
The big end shells need replacing but the crank appears to be unscathed. Both exhaust manifolds are scrappers as is the duplex cam chain.
It was rather depressing watching the engine coming apart and seeing just how bad it all was, but fascinating and enlightening watching the masters at work.
Not going to be cheap, but boy am i going to have well sorted engine next week
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