Barksavon
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| posted on 28/6/16 at 08:51 PM |
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Pinto compression?
Can anyone tell me what the compression figures should be for a 2.0 litre Pinto, both the high comp and also the low comp engines.
I ask because a few years ago i bought a 2.0 engine out of a transit (didn't know at the time it was a low comp engine) I had it bored out
to+0.5mm and fitted new pistons and rings. Now I know a little bit more about these engines I'm curious as to whether I've now got high
compression or low
Thanks Ian
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britishtrident
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| posted on 28/6/16 at 09:54 PM |
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The LC version would have started out dished pistons.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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snapper
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| posted on 29/6/16 at 04:20 AM |
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No all Pinto pistons are flat
Compression is decided by piston deck height
Standard high compression pistons are approximately 0.5mm below deck, lower compressions would be 1mm and 1.5mm below deck
On the last 2 Pinto's I built the piston deck height was stamped on the pistons, in 1 case it was 0.382mm
Standard compression ratio is 9.2 to 1
I believe LC engines came in 8,5 to 1 and 8.2 to 1
Whilst measured cranking pressure is not a good way to measure static compression ratio Haynes manual gives expected readings from a compression test
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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Tazzzzman1
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| posted on 29/6/16 at 06:38 AM |
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Ideally you should be looking at 150-170psi on each cylinder with throttle wide open. HTH
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Nickp
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| posted on 29/6/16 at 11:02 AM |
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quote:
Originally posted by snapper
No all Pinto pistons are flat
Compression is decided by piston deck height
Standard high compression pistons are approximately 0.5mm below deck, lower compressions would be 1mm and 1.5mm below deck
On the last 2 Pinto's I built the piston deck height was stamped on the pistons, in 1 case it was 0.382mm
Standard compression ratio is 9.2 to 1
I believe LC engines came in 8,5 to 1 and 8.2 to 1
Whilst measured cranking pressure is not a good way to measure static compression ratio Haynes manual gives expected readings from a compression test
So you can deck the block to increase CR then, presuming the deck has enough meat on it?
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Barksavon
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| posted on 29/6/16 at 11:13 AM |
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quote:
Originally posted by Tazzzzman1
Ideally you should be looking at 150-170psi on each cylinder with throttle wide open. HTH
Thanks for this info - is 150 - 170 for a high compression engine doing the test with the engine cold?
Ian
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Tazzzzman1
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| posted on 29/6/16 at 12:08 PM |
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Hi
I would expect even a high compression Pinto to still be within this region. Anything less than 150 PSI is usually a sign of an engine issue (Pistons
of Valves)
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mcerd1
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| posted on 29/6/16 at 03:25 PM |
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quote:
So you can deck the block to increase CR then, presuming the deck has enough meat on it?
you probably could, but its probably easier to just swap to the HC pistons 
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Nickp
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| posted on 29/6/16 at 03:38 PM |
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quote:
Originally posted by mcerd1
quote:
So you can deck the block to increase CR then, presuming the deck has enough meat on it?
you probably could, but its probably easier to just swap to the HC pistons
Possibly, I was thinking more about running them flush or even protruding for an even higher CR. Not that I have a Pinto, or intend getting one
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snapper
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| posted on 29/6/16 at 06:00 PM |
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Decking is preferred but only for high comp Pistons as head bolts will bottom out
Fitting ARP studs is better
Compression can be increased by skimming the head and using a thinner head gasket
Max compression for cast Pistons is about 10.5 to 1 although with carefull ignition timing 10.7 to 1 has been used
Here is the pinto conundrum
Pinto's like compression
Pistons don't
Cam shafts above FR33 needs compression and revs
The rods don't like revs
Cheaper options are Cosworth rods (bullet proof) but have floating gudgon pins
I fitted modified V6 Pistons to Cody rods but wished I had fitted forged
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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jollygreengiant
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| posted on 29/6/16 at 06:25 PM |
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Old Skool for upping the compression on a std 2.0 pinto was to fit a 1.6 GT (or Sport) head. You got the porting of a 2.0 GT head and the 2.0 Cam
shaft, but it whacked the normal 9/9.2/9.5 Compression Ratio up to about 10.5 -11.0 to 1 region. All because of the smaller combustion chamber on
the1.6 GT head. It does work, I did it myself.  BUT, you do need to know that your bottom end will take it and your starter motor is up to the job,
because it does tend to make it grunt.
Beware of the Goldfish in the tulip mines. The ONLY defence against them is smoking peanut butter sandwiches.
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Nickp
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| posted on 29/6/16 at 06:57 PM |
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quote:
Originally posted by snapper
Max compression for cast Pistons is about 10.5 to 1 although with carefull ignition timing 10.7 to 1 has been used
Just Pintos? I've built VW 8v GTi and Fiat / Lancia TC engines, both with over 11.5:1 CR on std cast pistons. Both peaked around 7krpm but I
kept the rev limit below 7.5krpm. Both were fine and the VW did a full seasons racing no probs. Maybe I got lucky?
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britishtrident
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| posted on 29/6/16 at 08:16 PM |
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When comparing different engines keep in mind an aluminium alloy cylinder head will allow the use higher compression ratio than an iron head, usually
around 1.2 higher without any other changes. Also modern engines have better swirl characteristics than older lumps.
[Edited on 29/6/16 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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mcerd1
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| posted on 29/6/16 at 09:36 PM |
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quote:
Originally posted by Nickp
Possibly, I was thinking more about running them flush or even protruding for an even higher CR. Not that I have a Pinto, or intend getting one
can't really let them go higher than the block, its not like the head has any space for them to go 
as above you'd still really want HC pistons, and chances are you need new ones anyway so why get the wrong kind
I've made mine flush using effectively HC piston heights (actually my pistons are 0.060" shorter than stock but my rods are 0.060"
longer than stock)
and that gives me the 1mm gasket thickness as my clearance to the head - 0.75mm is the minimum value I've seen quoted, so I'm not got much
to play with at that....
one other thing that's not be mentioned in the above is how cam duration affects the static CR you want....
[Edited on 29/6/2016 by mcerd1]
[Edited on 29/6/2016 by mcerd1]
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Nickp
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| posted on 30/6/16 at 03:30 AM |
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quote:
Originally posted by mcerd1
quote:
Originally posted by Nickp
Possibly, I was thinking more about running them flush or even protruding for an even higher CR. Not that I have a Pinto, or intend getting one
can't really let them go higher than the block, its not like the head has any space for them to go
[Edited on 29/6/2016 by mcerd1]
[Edited on 29/6/2016 by mcerd1]
They can protrude into the gasket space which can actually help with squish, in theory. About 0.5-0.7mm into a 1.5mm gasket is usually safe enough and
can help achieve your desired CR.
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snapper
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| posted on 30/6/16 at 04:30 AM |
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Fitting the 1.6 head was done in the past but using the older thicker head gaskets and doing some serious chamber work to in shroud the valves
2.0 L head had chamber volume of 48 to 50cc
1.6 head 38c
On a standard 2.0L engine with a 1.3mm gasket chamber volume needs to be about 43cc for 10.5 to 1
It's the ring lands on pinto Pistons that give out first, the rings are thick and heavy and the ring lands are thin
Running flush Pistons or even slightly out of the block needs a whole engine plan
Absolute minimum piston the head gap is 0.75mm or rod stretch will have piston touching the head at high revs
0.90mm is safe
The only thing separating the piston from the head at TDC will be the head gasket thickness
Cam type & timing, valve lift st TDC etc. Has to be considered
The last point to consider is the spark plug earth electrode, these can hang down below the head face on highly skimmed heads, I have 1 head with plug
inserts to take 10mm plugs thus raising the electrode out of Harms way
And another head where I index the plugs to see where the electrode is positioned when tight
A blob of paint on the ceramic insulator where the shoulder of the earth electrode is so when fitted you can see where the electrode orientatsbfrom
the outside
This meat God requires a collection of plugs to find four that will sit with electrode in an acceptable position
[Edited on 30/6/16 by snapper]
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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mcerd1
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| posted on 30/6/16 at 06:27 AM |
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quote:
Originally posted by Nickp
They can protrude into the gasket space which can actually help with squish, in theory. About 0.5-0.7mm into a 1.5mm gasket is usually safe enough and
can help achieve your desired CR.
But most pinto gaskets are around 1mm thick when compressed
I'm in the middle of doing a dummy build to check valve to piston clearance as snapper says...
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