Technical 1368 mk.1 Punto ELX85?

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Technical 1368 mk.1 Punto ELX85?

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Hi gents - on https://www.fiatforum.com/punto/328181-1368-mk-1-punto-elx85.html they said 'some real 16v experts in the cento section' so here I am.

Looking to put a 1368 bottom end into my smoky 140k mk.1 Punto Cabrio ELX85, which has mk.1 Sporting spec i.e. 16v 1242 86PS with the better cams, cable-op throttle etc compared with the mk.2 1242 Sporting/ELX85.

Tho they put the stronger cams back in the mk.2-and-a-half 1368 95PS Sporting as well as bigger cc, it's still looking best to keep my rebuilt mk.1 head plus everything top-end, just get a lo-mile 1368 bottom end.

This is for basically standard Mk.1 setup, just more ccs, not tuned up.

The question for the 16v experts is -
- is it right, to keep my mk.1 head, on a 1368 bottom end, or wd that be losing bigger ports, valves etc?
- is the mk.1 head compatible with mk.2 pistons - CR, valve clearance etc?
- would any 1368 be OK, for just bottom end, with my mk.1 head, or should Starjet bottom ends be ruled out? If not Starjet then AFAIK I'm limited to Stilo and mk.2-and-a-half Punto - correct?

Prob more Qs, but enough for now. Thanks in advance.
 
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Great! All have same piston crowns?

What happens to CR, clearance etc with 1242 mk.1 16v head on 1368 block?
- 1368 has 72 bore vs 70.8 for 1242 - could the 1368 piston-top pop-ups clout the deck-edge of the 1242 combustion chamber?
 
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you need to check the piston clearance for each piston as well as the head clearance for each cylinder and add a factor for max revs...

strait edge and feeler gauge

may be restricted in how much skimming you can do so you also need to check for flatness of head and crankcase before you start e.g. you may be starting with skimmed bits already or banannas

dermal with a jig is an option...

you need to keep the crank pulley and ECU as a matched pair
 
Thanks - good advice - inching towards a well informed decision.

Checking clearances, feelers etc, yes - but what shape the 1368 piston-top pop-up on top of the bigger-bore piston - will it fit nicely, inside the 1242 combustion chamber shape? Could hit the side, or CR could be higher, or lower, depending on how the shapes fit.

Thanks for the oil way tip.
 
if there is clearance between the piston top and the crank top allowing for max RPM id not worry
if the piston is too near to flush or +ve you need to check the head has sufficient
if it is marginal Plastigauge rotate the engine by hand with head gasket and torqued but without out cam shafts
id be more worried about valves
id refurbished the head and have a minimal skim even it was flat
ditto bottom end
 
It is totaly fine to use :).

Am running 1368 16v block and a mk 1 punto sporting head.

You really have to turn the fuel pressure up, else it runs really lean.

If you find someone that can map the older ECU type let me know.

P.S, I am also using the MLS gasket.

Ming
 
Great info - incl about gasket - is MLS special in some way?

In https://www.fiatforum.com/punto/328181-1368-mk-1-punto-elx85.html
fingers99 said, about remapping the standard mk.1 ECU to suit 1368cc:

"Peter very much rated what could be done with that ECU.

As a rough guide, folk seem to get 110bhp out of the 1.4 16v with nothing more than a decent manifold and a "proper" TB (Rover K Series Dell'Orto, etc.) when running aftermarket ECUs. A remap should give you much the same."

So quite readily done, it seems.
 
Just realised your not too far from me feel free to drop me a pm and drop round if you need timing tools and or help

Ycming that might help me re turning fuel pressure up I'm guessing you need to take apart the mk1 sporting rail to remove stock regulator then use an adjustable one?

You don't have to, i got the info from honeymonster. You regulate at the return.

Just leave the stock on in with no vacuum pipe attached. at 4 bar fuel pressure the car felt great the hesitation "almost" disappears, but spluttering at idle is gone.

This points to me we need bigger injectors and a remap of course.

Ming
 
Hi There thanks for posting. I seem to think I have the same problem with spluttering at idle and the rest. My Punto 1.2 16v sporting s reg hesitates at times . Do you think I should ask the garage to increase the fuel pressure?(y)
 
Hi There thanks for posting. I seem to think I have the same problem with spluttering at idle and the rest. My Punto 1.2 16v sporting s reg hesitates at times . Do you think I should ask the garage to increase the fuel pressure?(y)

Have a look at your plugs if the "nose head" of the plug is really white then is probably running lean. Or just look at the lambda.

But being a 16v with everything matching like injectors , ecu you shouldn't have to.

Did you change your fuel pump to a high pressure one?

Ming
 
Thanks, no have not changed it for a stronger one yet. I have not done anything physical on it yet either apart from narrowly avoiding a huge bill from a Fiat Dealer (Shame). All that has happened recently is the loss of power while cruising in first in a traffic jam at around 2K rpm. Increase the revs and she pulls out of the splutter. Get home and release the full filler cap and there is a very strong vacuum release, as mentioned this eases the problem. What do you you sceam?
 
The long delayed project creeps forward - putting a 1368 Stilo bottom end under the existing standard-spec top end of my 1242 16v Punto mk1 Cabrio. The hope is that the existing Punto electronics will continue to manage the 10% large capacity without need for tweak.

The allegedly lo-mile Stilo 1368 bottom end was bought v cheap, unseen on eBay, and indeed turned out to have perfect bores and journals, now effectively built into a near-new engine. The Punto top end is also rebuilt to near-new.

Today we did some rough CR measuring. We set the 2 blocks, new and old, and the head level and simply filled the chamber spaces with diesel, flush with the block/head face, using 5ml 'oral syringe'. The results are below and I'd welcome any comments on whether they look credible.

1242 = 310.5cc per cyl, 70.8 bore x 78.9 stroke:
Punto piston dish 16cc, 1.5mm gasket 6cc, Punto chamber 12cc, total 34cc
CR = (swept/chamber) + 1 = (310.5/34) + 1 = 10.13:1
Various data sources say it should be 10.2 or 10.6

1368 = 342cc per cyl, 72 bore x 84 stroke:
Stilo piston dish 22cc, 0.5mm gasket 2cc, Punto chamber 12cc, total 36cc
CR = (swept/chamber) + 1 = (342/36) + 1 = 10.5:1
Various data sources say it would be 11 or 11.2 if using the Stilo emissions-oriented head, which is prob different from the performance-oriented Punto head that we're keeping.

The question that even the experts on here couldn't answer, is what CR I'd end up with, in this combo. I was worried that it would give a lowered CR - these figures suggest it's actually up a bit, tho not as high as the standard Stilo.

Any comments?
 
I would not worry too much about the CR ratio. As long as it is around 10:1. It will be more to do with the ECU coping with running the engine.
Going higher on the CR ratio will require much stricter fuel control to stop detonation, even though 10:1 is high any way. Another issue will be the intake supply being adequate for the extra capacity. The ECU may get the mixture correct but be starving the engine to maximise it's potential?
 
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I thought ECUs rely on having a high enough CR to create knock, so they can run good advance but retard that instantly when they detect knock? Provided that's happening, then higher CR the better?
 
Going slowly - have had to source a new (pattern) sump and oil pickup because the 1368 short engine didn't come with em and the 1242 ones are quite different.

With the 1368 head gasket being 0.5mm thick compared to the 1242's 1.5mm, so the 1242 head is 1mm lower on the 1368 block, than it was on the old 1242 block, there's a worry that the valves may clout the piston tops. The valve clearance cutouts in the top of the 1368 pistons look about same depth as in the old 1242 block, so it'll be close!

Subject to that, it cd be a good tweak for 1242s - use the 1368 gasket for extra CR? Is this thin gasket what they call MLS -'no compliance so block must be skimmed'?

We've had to keep the 1242 flywheel because that didn't come with the short engine either. The 1242 flywheel obviously has extra metal than the 1368 one - why would the 1242 flywheel need to be heavier?
 
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