Compression on 803 Engine

Post by **HarryMango** » Mon Jun 26, 2006 3:37 pm

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

Post by **Kevin** » Mon Jun 26, 2006 4:31 pm

I cant seem to find it.

What no compression

Post by **bmcecosse** » Mon Jun 26, 2006 10:44 pm

'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.

Post by **HarryMango** » Tue Jun 27, 2006 12:31 pm

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

Post by **bmcecosse** » Tue Jun 27, 2006 11:36 pm

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!!

Post by **Kevin** » Wed Jun 28, 2006 12:34 am

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

Post by **Scott** » Wed Jun 28, 2006 2:10 am

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.

Post by **bmcecosse** » Wed Jun 28, 2006 1:20 pm

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.

Post by **HarryMango** » Wed Jun 28, 2006 3:22 pm

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

Post by **Onne** » Wed Jun 28, 2006 4:06 pm

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

Post by **Scott** » Wed Jun 28, 2006 11:23 pm

HarryMango wrote: Is that as bad as I think it is then ?

Yes

.

At least you know your valves are OK

.

Post by **bmcecosse** » Thu Jun 29, 2006 7:26 am

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.

Post by **HarryMango** » Thu Jun 29, 2006 11:57 am

[quote="Scott
At least you know your valves are OK

.[/quote]

I would have preferred to just do the head though

Cheers
Rog

Post by **Kevin** » Thu Jun 29, 2006 12:01 pm

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.

Post by **HarryMango** » Thu Jun 29, 2006 12:04 pm

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

Post by **HarryMango** » Thu Jun 29, 2006 12:10 pm

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