1800: First Engine Rebuild

[CA124]

Hi All,

Finally sourced a complete 1800cc engine and going to do a rebuild. It turns freely and was running when pulled.
Question is how should I rebuild this engine? I currently have a 1438cc engine and its fun revving but lacks guts/HP.
So my quest was for more hp which the stock 1800 will give me but since i'm rebuilding I wanted to take the opportunity to do some mods. Looking for ideas from light to medium mods using the same block and head combo.

BTW: If there is an existing thread about this exact topic please point me to it. I've searched and couldn't find one.

Thanks!

[chrisg]

If you don't have it already, I'd recommend Guy Croft's book as a guide. I don't mean that I recommend you build an all-out GCRE spec monster for your car (but, hey, you might want to), but there is a very good, practical section about the investigative break down (and of course, rebuild) of a twin cam engine.

I have not recently researched this topic here, but i did recently find some good engine building information, along with some interesting data on how 2L & 1.8L engines can be mixed & matched to increase compression at mirafiori. I don't know if it's bad form to recommend checking out a different Fiat forum, but there is a wealth of information there. I was planning on heading down the same path with what I was going to refer to as a 'warmed up' (basically European spec, maybe cams, maybe IDFs) 1.8 for my 124 Sedan. As it happened, I stumbled onto a stalled out 1.8 build that was supposed to be somewhere along that spec, so I am using it as a basis (I may be using it for parts...that remains to be determined) for the project. A lot of people would say to jump straight for the 2L engine due to the increased torque and HP at a lower RPM, but I think the characteristics of a nicely built 1800 would better preserve the driving characteristics your car has now. Have fun!

[Nut124]

What's your budget?

I have an 1800 car that I built approx to the Guy Croft fast road spec (less HC pistons. Running 9.0CR) back in 1999 or so. It runs like about 125HP. 16.1s quarter mile at the local drag strip. Fun car.

[CA124]

Thanks for the reply!

I've heard the 1.8 is a great engine as a base and it'll def fulfill my quest but wanted to see if I should use different pistons or cams to make it a little more sport purpose.

I've heard of Guy Croft and can read up on tips when stripping down and rebuilding of a fiat engine. Don't want to go completely crazy (or should I?)

As for budget - the least amount for the most HP would be best of course.

@Nut124 How much did your rebuild cost you back in 1999. Also where are you located assuming you need higher octane gas for the HC

[Nut124]

I would never rebuild an 1800 back to US stock condition, 8.0:1 CR etc.

At a minimum, I would do:
- remove all emissions gear
- Medium CR 4mm(?) dome pistons
- 40-80-80-40 street cams, Isky springs
- header
- improved carburation
- electronic fuel pump and a pressure regulator
- pointless distry. The late Fiat one is OK

Desired:
- High CR 8mm(?) domed pistons
- larger (37mm) intake valves and a valve seat job
- spin balance
- dual 44IDFs
- ARP stud head fasteners
- mild port work

I had started a rad 1800 project, but my donor engine had suffered massive detonation and the bores were beyond repair. Looking for a new 1800 donor engine.

[joelittel]

I’ve got a modified 2L with low dome pistons. I haven’t done a compression test so I cannot say exactly where I ended up. But... If I had to do it again I’d go for the high compression 10:1 pistons.

The low dome medium compression pistons made a difference, but not as big of a difference as I was hoping for.

When I built mine I found all sorts of conflicting and confusing accounts. One post would say the 10:1 pistons caused problems and another post would say they were the greatest thing ever.

I wasn’t willing to take the risk so I settled on the low domes.

Since completing my build I’ve read more positive posts than negative about the 10:1 pistons, hence my current opinion that if I had to buy new pistons tomorrow they’d be 10:1.

If those pistons caused issues I’d reduce the compression with a thicker head gasket.

Definitely add billet cams (not regrinds) and adjustable cam pulleys to your shopping list.

[Nut124]

Just another point to remember. Most tuning mods do not improve engine torque or HP and normal RPM ranges. HP improvement is gained by improving volumetric efficiency (flow of air) at high rpm. This allows the same torque to be produced at a higher rpm, thus more HP. If you can produce the same torque at 10% higher rpm, you have 10% more HP. These mods often hurt torque and power at low/mid rpm.

The increased HP can only be had by revving the engine higher. This is why F1 engines run at 12,000rpm.

The only mod, generally speaking, that significantly improves torque and HP at low/mid rpm is turbo/supercharging.

[CA124]

Good info - thanks!

I'm planning on using this engine for rallys thought back roads so low to mid range power would be nice to have. I can give up low end and lean more on mid range to high. With that said does anyone have a guide to an 1800 engine spec that achieves this curve range? My findings show that 1800 has a pretty linear curvehttp://www.automobile-catalog.com/curve ... _1800.html

Thanks!