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poor compression
jim75 - 18/5/08 at 11:31 PM

I posted a few weeks ago about my pinto. It's not running right. I double checked the timing got rid of the vapour separator (which helped) balanced the carbs (this helped too) it still doesn't want to accelerate though so today I did a compression test and got

1 - 100
2 - 70
3 - 70
4 -120

According to the manual they should be on 170 !!!

So it needs _something_ done to it.

I'm going to have to take the engine to bits I suspect.

So ... it's not been modified for unleaded as far as I knw so it could e the valve seats are not right.

Piston rings could be shagged
Head gasket could be screwed
Block could be damaged

I guess I won't know until I take it to bits.

How will I be able to tell whats wrong when I take it to bits?

Can you guys recommend a place to take it to sort it out. I'm not too bothered about tuning it just getting it to run right.

On the other hand is there anything it would make sense to do while the engines in bits?

Any opinions welcome.

blakep82 - 18/5/08 at 11:42 PM

sorry, i'm not help, but... might help if you let us know where you are so someone can recommend somewhere near you

mookaloid - 18/5/08 at 11:56 PM

If you squirt some engine oil in to the cylinders and repeat the test, If the compressions go up the chances are it's the rings. If there is no change its head gasket or valves.

Might just be worth trying this before you rip it apart - if it is the rings you might be better off (financially) with a replacement bottom end

Cheers

mark

britishtrident - 19/5/08 at 06:24 AM

Check the valve clearances it could be simply the valves don't have enough clearance to close properly.

Low compression on two adjacent cylinders could indicate the head gasket has failed between tye two cylinders however my money would be on burnt exhaust valves due to an leaded fuel engine running on unleaded.

jim75 - 19/5/08 at 07:15 AM

Oh and I'm in london

Presumably the only way to check the exhast valves is to take the head off.

Oh and another thing is that when I start it there is white smoke coming out the exhaust for the first ten seconds or so.

Also when doing the test only 4 got to that compression right away the others got to their readings after several revolutions.

So it could well be a combination of valve clearance and piston rings. Which would mean gettting new valve seats put in and reboring the block and putting in larger piston rings right?

How would the cost of that compare to a new bottom end?

Sorry for all these questions but I have to get this sorted. It's no fun to drive right now and I'm pretty sure it would fail the sva on emissions at the moment.

I found a place called vulcanengines who are just down the road from me and they would sell me a new engine ready tuned for 1850 (Ouch!) I can't really spend that much.

Anyone used them before? Would they sort my engine out for less than the cost of a new one?

Cheers for all your help guys.

indykid - 19/5/08 at 07:41 AM

are those readings taken at wide open throttle?

can't remember who it was but someone before has found really low compression readings and it turned out they were doing it with the throttle closed.

tom

02GF74 - 19/5/08 at 07:50 AM

^^^ wot tom says. you would expect compression to get up to max in about 3 or so revolutions.

also you test will all plug removed - sure you did that but .....

Macbeast - 19/5/08 at 08:26 AM

You can probably buy a decent second hand Pinto for £50 - £100 so I personally wouldn't consider a new one at that price.

White smoke for 10 secs to me would be oil getting past the valve stem seals.

Looks like a top end refurb.

Where exactly in London ? Theres some kind of head refurb place near Dalston / Hackney I could go in and ask if you like.

britishtrident - 19/5/08 at 11:31 AM

sounds totally knackered.

locoR1 - 19/5/08 at 01:15 PM

As indykid said (and it was probably me that said it before! speaking from experience)if you didn't have the throttle wide open you wont get a true reading on compressions.

jim75 - 19/5/08 at 01:25 PM

From your comments I've done the compression test all wrong.

I did it with the throttle closed and all plugs in except the one I was testing.

I'll do it again tonight the right way.

The fact that I got such different readings is a concern though.

MacBeast, I'm near chiswick but work in farringden so hackney dalston is certainly not out of the question.

If you could have a look I'd really appreciate it.

My thoughts on picking up a second hand one are that there is no guarantee it won't have exactly the same problem.

Will have a dig round ebay though to see if something jumps out.

jim75 - 19/5/08 at 01:41 PM

quote:
Originally posted by britishtrident
sounds totally knackered.


Arse.

Sounds like the best bet might just be looking for a second hand engine then as redoing both the bottome end and the top end just sounds like more hassle than it's worth.

Macbeast - 25/5/08 at 04:20 PM

Jim you have U2U re Dalston Cylinder Head Specialists.