Race Engine Forum UK

Hello all.

A little introduction my name is Adrian. I am not building race engines but do have a passion for my road car, namely my original Fiat Bravo.

My car's engine failed, without any previous engine experience I decided to give it a right good go and jump in at the deep end. With a lot of research of course. I was very excited to learn hands on about engines and of course make my car nice clean example of a Bravo. There are things I would do differently and I think mistakes I have made.

This was one of many proud moments; Now it turns out the engine I put together burns oil at a rate of 1Ltr per 600 miles, but the performance is not negatively effected in any noticeable way. The spark plugs are a nice dry light brown, the car is really responsive and nippy.

Original Engine was a 1997 Fiat 1.4 12v 80bhp with 34000 Miles on the clock
My original problem was a misfire, that was caused by oil getting into the combustion chambers. I tried to logically figure out the problem, there was a lot of oil going through the oil breather into the inlet manifold. A compression test showed uneven results but did not as far as I could tell show a clear cut reason to the problem.
1 153 psi
2 190
3 190
4 170

I wanted to use a borescope to check inside the combustion chambers but had no access to one. I decided the only way I will know the cause is to take the head off.

Then it became apparent. All four bores badly scored and hatchings are gone. I decided to clean everything up get a block from a scrap yard and put it all back together. Using all Fiat original parts. At first as a plan I wanted to change the piston rings and big end shells. This is where I think I have made one of the mistakes. The replacement block I got was at 77000 miles and had been without a head in a scrap yard for a few days maybe a week I was told. When I got the block I looked at the shells and decided they where good. I looked at the bores, the hatching where even all they way around (pictures dont bring them up well).

I think my biggest mistake was underestimating the black discolouration you can see here; This piston is at the very bottom of its stroke, you can see where the piston rings have been sat for a while just over 1/3 of the way up. Every scrap yard block I had seen was like this so I decided there wasn't anything to worry about? Is this wrong?

second and where I am guessing my problem comes from is the black discolouration you can see at the bottom of the bore. This piston was the worst but others had a small amount of it as well. I looked very closely at this and felt it. It seemed perfectly smooth and just looked like though it must just be a discolouration perhaps carbon, perhaps oil?. I had seen this discoloration under big end shells so In my inexperience I decided it was nothing to worry about as well.

So what do you experienced people think of this image? Does anything look obviously wrong here, Do I need to pull it to bits and replace piston rings? re-bore it? Or just keep topping up and see if it gets worse or better? I have done 4000 miles since the rebuild.

My car is quite a unique colour and the shell is in very good condition, so id like to keep it.

Thank You for reading.
Adrian

My Car

I realised the pictures where stupidly large. I have edited my original post to reduce the image sizes.

I had my MOT today and as I expected it failed on emissions because it is burning oil. I normally want to do things to the best possible standard, for some reason partialy based on advice I decided not to change the piston rings and re-hone it . Now I really regret that.

I'm very sorry indeed I did not catch this thread in time to warn you, sorry about your bad luck there.

Live and learn?

G

Oh yes Guy. I wont be leaving anything to chance in the future. I defiantly learnt a lot about engines which was my main goal to start with, so all was not lost. Im not sure what I will do with this car yet. Something new is tempting, I really like the design of those 1.8 and 2.0 (20v non-VIS) Fiat engines.

Guy are you familiar with the Fiat 1.4 12V SOHC Head? Any opinions on it?

Here are the only pictures I have. It is SOHC obviously, with 12 valves. Two inlet and one larger exhaust valve per cylinder. The tappets are hydraulic self adjusting. A lot of these heads suffered from cam shaft failure due to oil starvation, but my head pictured here at 34000 miles did not. The engine management is a Bosch Monomotronic SPI (not re-mapable). The fuel injection is governed by throttle position, Rpm and lambda only so it is very basic. No MAP/MAF sensors here.

Cylinder Liner (Bore) 82mm (82,000÷82,010)
Stroke 64,87mm
CC 1370
Compresion Ratio 9,85 (± 0,15)
Valve Inlet Diameter 30,200÷34,500 (angle 45°30' ± 5')
Valve Exhaust Diameter 34,500÷35,700 (angle 45°30' ± 5')
Max Power 59kW / 80CV
Max rpm 6000
Max torque 11,2daNm at 2750rpm

Good Evening Guy, I hope its all going well.

Can I quickly ask Guy the black marking on this cylinder wall in this image. Is it Wrong?

I have sold this car to someone who has the workspace to look at it again. They have started to strip the engine. I can see in an image the black marks are still on the cylinder wall in part even after several thousand miles. I now own a 1996 Fiat Bravo 1.8 1747cc 113Bhp

Those marks look remarkably like corrosion damage from water/coolant. Many times that can be enough below the cylinder wall surface to remain indefinitely. They will fill with carbon and look very black.

Sorry I didn't notice this question was directed to Guy. Delete if necessary.

Robert

Hi Robert, No its fine I appreciate any reply.

Im trying to understand if the corrosion marks would give any problems, like burning oil or loosing compression. Also how would you put them right. would a hone be enough or would something more substantial need to be done.

Thanks
Adrian

From my experience the surface discoloring as long as you can not feel it with your finger tip will not cause high oil consumption unless sever over fueling exists.. I would error on the side of caution and hone it anyway.

If you can feel the darkened area with your finger it is at least .0002 in.. Really insignificant and should disappear with a quick licking with a ball hone (looks like a bottle brush with an abrasive ball in each whisker.) and remain in spec assuming the bore is properly sized in the first place. Low mileage rings will re-seat in a few hundred miles of firm driving. Or if you prefer new rings.. Reverify piston ring indexing and end gap while in the bore.

Nothwithstanding good posts from Robert, Adrian you need to STOP engine building (for now) and do some READING!

Start here:

http://guy-croft.com/viewforum.php?f=3

GC

Sorry my last two posts were poorly written, I accidently drifted into how to fix the problem when that is a non-issue. I know the black marks are wrong but all I wanted to understand and what I should have only posted about was the possible cause and effect of those marks, thankfully Robert was kind enough to answer. This is the only engine I have put together, in my original post I tried very carefully not to use the word build. As all I really did was clean a few parts, mate a supposedly good block with a supposedly good head, lap the valves and properly time it with Fiat tools. All in an effort to learn about engines. As you can see I thought about fixing the engine properly a second time but decided the 1.4 12v engine was not a worthwhile investment. I know I need to learn a lot more before doing anything else.

Thanks for your help Guy and Robert. I have a lot more reading to do.

That's the spirit! Good for you!

Confronted with the state of the bores I'd be thinking: 'what's the state of the pistons, rings?' There would be no question in my mind as to what I'd find - wear. Bores never just wear on their own and corrosion damage will have ahd consequences elsewhere. Not just pistons, bearings too and potentially anything with oil on it because water will have got down into the sump.

I would never waste time on honing given the water corrosion present because assuming 1) the pistons are clean and unworn and their grooves are in sufficiently good state to accept new rings (and dressed accordingly which is no easy task) and 2) that new rings are available and 3) that the rings will not be damaged by any 'wear ridge' at the tops of the bores, and 4) the ring end gaps are good after honing: 14-16 thou and 5) that the bores clean up sufficiently well (and Flex-Hone would HAVE to be used, grade according to ring type) - the thing will never seal as well as a rebored/honed block with new pistons and rings.

G