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Compression on 803 Engine
Posted: Mon Jun 26, 2006 3:37 pm
by HarryMango
Hi Folks
Can someone tell me what PSI I should expect from a compression test on 803cc engine - I cant seem to find it.
Rog
Posted: Mon Jun 26, 2006 4:31 pm
by Kevin
I cant seem to find it.
What no compression
Posted: Mon Jun 26, 2006 10:44 pm
by bmcecosse
'Compression' and '803' are not often used in the one sentence. Not surprised you can't find it!!
If you are doing a compression test - I would think 140/150 psi would be very very good ! Probably more like 120/130 though.
Posted: Tue Jun 27, 2006 12:31 pm
by HarryMango
I would have thought it would be less on 803. I have a few problems I need to sort out & thought I would do a comp test before I pull it apart. It has started idling / running roughly. It is also dripping a little oil from the Air Silencer when hot.
I have not got a comp tester yet so will let you know when I do the test.
Cheers
Rog
Posted: Tue Jun 27, 2006 11:36 pm
by bmcecosse
Oh but 140/150 IS low for a normal engine. More likely you will have 120/130 - if lucky!! Remember to take out all the spark plugs - hot engine with battery full charged - and prop the throttle open with a brick on the pedal. Take it off again before starting engine when finished!!
Posted: Wed Jun 28, 2006 12:34 am
by Kevin
and prop the throttle open with a brick on the pedal.
Why
I have never done that when checking compression or seen it done so I must be missing the point somewhere
Posted: Wed Jun 28, 2006 2:10 am
by Scott
The throttle needs to be open otherwise the vacuum can affect the readings. It won't make that much difference if you're tracing a duff cylinder though.
Posted: Wed Jun 28, 2006 1:20 pm
by bmcecosse
Yep - it just makes sure the engine has best chance of sucking in a good charge of air. If it struggles to breath past a closed throttle - there will be less difference between 'good' and 'bad' cylinders.
Posted: Wed Jun 28, 2006 3:22 pm
by HarryMango
Hi Folks
Well I've done the Compression Test & got the following :
110, 105, 65, 105 & with added oil 165, 170, 170, 165.
Is that as bad as I think it is then ?
Rog
Posted: Wed Jun 28, 2006 4:06 pm
by Onne
bmcecosse wrote:'Compression' and '803' are not often used in the one sentence. Not surprised you can't find it!!
If you are doing a compression test - I would think 140/150 psi would be very very good ! Probably more like 120/130 though.
It's not a sidevalve mr Ecosse! I would think it is comparable to the later A-series, which you seem to know so much about!
Onne
Posted: Wed Jun 28, 2006 11:23 pm
by Scott
HarryMango wrote:
Is that as bad as I think it is then ?
Yes
.
At least you know your valves are OK
.
Posted: Thu Jun 29, 2006 7:26 am
by bmcecosse
Onne - the 803 has very low CR - hence the low expectations.
Harry - afraid it shows your bores/rings/pistons are in pretty poor shape. Maybe hard to get pistons for this engine.
Posted: Thu Jun 29, 2006 11:57 am
by HarryMango
[quote="Scott
At least you know your valves are OK
.[/quote]
I would have preferred to just do the head though
Cheers
Rog
Posted: Thu Jun 29, 2006 12:01 pm
by Kevin
Is that as bad as I think it is then ?
Rog it certainly looks that way, I cant believe the 100lb increase on number 3 that must have some wear in it.
Posted: Thu Jun 29, 2006 12:04 pm
by HarryMango
bmcecosse wrote:Harry - afraid it shows your bores/rings/pistons are in pretty poor shape. Maybe hard to get pistons for this engine.
Thats what I feared
I'm chasing up a couple of possibilities on recon 803 blocks though as I want to keep it to original spec.
Thanks
Rog
Posted: Thu Jun 29, 2006 12:10 pm
by HarryMango
Kevin wrote:I cant believe the 100lb increase on number 3 that must have some wear in it.
Hi Kevin
Icouldn't either but checked it twice - I don't think there's a piston in no3
I think I might revert to Fiesta power for Sunday otherwise it'll take me all day to get there
Rog