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Seicento Seicento 8V build

Introduction

Hello everyone,

I'm Kruno from Croatia and have two centos.

I'm in the line of work of vehicle restorations where we mostly do Skyline GTRs, 911s amongst other cars. We recently did an EVO 6 TME for a customer in UK.

In my free time I like to fiddle with underdog stuff so my engine selection and cash dumping can seem unreasonable and peculiar to an average by the book logical guy.

Although You know most of the details about FIRE engines, I will still post my whole thread that I made for another forum where FIRE knowledge is vague.

This build started when I discovered that Subaru STI 2003+ uses shimless buckets in 35mm diameter so I wanted to build a 8V FIRE to use it.

I also wanted to build a car with a wide powerband to use it with a long ratio gearbox since we have one track in Croatia and it's a fast one.

I would kindly ask a moderator to enable URL posting for me so I don't spam the board for nothing.

Thank You and best regards!

Kruno
Hi Kruno, welcome to the forum.

Site Admin have not given us mods a switch/button which allows us to bypass the URL limitations on a per user basis.
However, what you want to do - while noble, doesn't help if the other forum/website ever shuts down as all of your info will be gone and the links you've posted will be dead (this would also happen if they ever decide to change any URL's).
Instead, consider creating a thread on here and copy-pasting everything from the other forum. It may take longer, but will be much more useful to our future members.
 
Last summer I've had enough of my Alfa Romeo 166 V6 and bought two Centos for fun.

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As I moved to a capital of the Croatia, Zagreb I needed a smaller car for parking so I went Italian once again.

They are simple, parts anywhere for cheap etc.

First I bought the Cinquecento Sporting that previous owners used for autocrossing.

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It was already uprated with a 75Hp engine from a Fiat Punto and had some poorly done mods to it, I decided to buy a Seicento for daily driving and use this for a project car.

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Over the last 10 years I was mostly reading stuff and gathering information and never had a chance to do a project like this with my Japanese cars due to various reasons.

I always upgraded suspension and brakes on my cars so I wanted to go backwards with this car - everything is about engine building here.

Main purpose of the car was to make a hot street toy but it eventually progressed to a potential track day car that will probably see the track eventually.

My personal goals to be made:

1. Use almost no off the shelf parts
2. Adapt parts from other vehicles
3. Run Bike Carburetors
4. Make as much power as possible through the whole rev range and not emphasise on peak numbers
5. Use 8 valve engine to retain original look and simplicity
6. Use the biggest displacement engine from the same family
7. Cylinder head porting needed to be done by myself by hand
8. Achieve something in the range of 120-140 horsepower if possible

So first I bought 4-5 engines for parts and stock.

Grande Punto 1.4 8V engine purchased for the bottom end and few Punto 1.2 8V 75hp engines bought for the cylinder head and spares.

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Those engines have bad bore/stroke relationship with 72mm bore and 84mm stroke with a lousy rod ratio and short rod in general so I didn't want to put any money whatsoever in modifying the bottom end before we test it in the car.

As the bottom end had 60000 kilometers we only put new rings in it and left the original bearing shells so I don't need to clearance it and everything ( and they were as good as new)

General idea was to use high compression pistons to achieve desired Compression Ratio, but due to block/head combo and bigger stroke we achieved something in range of 11.x :1 with standard pistons and I didn't want to go overboard with pump gas.

Decision was made to mate it to an older style cylinder head as the head design is much better and selection of cams for newer style head is virtually nonexistent.

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After going through the FIA papers for the Panda Kit Rally car that used the same combination of block/head castings and following common sense, camshaft selection was determined as well as the port sizing/shape and valve sizing.

From that I resorted to valves that were commercially available - Grande Punto 1.4 8V valves that were bigger in size (I 33,5mm vs 31,5mm stock and E 28,1mm vs 27,5mm stock) and smaller in stem diameter (5mm vs 7mm stock) that made them noticeably lighter as well.

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For this modification a custom set of valve guides needed to be made as well as new valve seats needed to be pressed in and machined at 3 angles for better flow.

I wanted to go larger on the intake valves but it's a far more custom job as it involves eccentric guides and custom valves so that will wait for a new cylinder head build sometimes in the future.

The cam selected and bought was CatCams steel billet 290° cam with 10,2mm lift and 105° LSA.

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In the next stage I wanted to do a lighter valve train with shimless buckets and bought one Subaru STI lifter for testing purposes.

They can be made to work and we did everything to make them work but unfortunately I couldn't source the lifters at the time so I resorted to Grande Punto buckets that are again lighter than stock and work really well for cheap. (also far easier to set it up with shims but again heavier)

As we had custom valve guides to suit the valve/head combination the standard springs/retainers/collars didn't fit as well as the standard valve stem seals so with the whole parts bin we made a combination to suit with smaller/lighter but also softer valve springs that mostly aren't good for high RPM applications.

AFAIK some Nissan economy car engines used titanium retainers from factory, but I couldn't find them at the time so I didn't use that unfortunately.

Since the valve train was lighter as well I suspected the springs will sustain the RPM range of a "factory stroker" engine without any valve float. If I diagnose valve float problems at high RPM, I'll probably adapt some Honda B/K engine valve springs or something in Honda range that fits.

The head porting began and when I inspected the possible port work vs the ideal ports on paper, next step was finding the exhaust manifold to suit.

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After googling some photos of motorcycle manifolds, I bought CBR1000RR standard manifold as it looked like it could be modified to fit.
Eventually manifold arrived from Germany and it matched almost perfectly with calculations of the sizes and lengths needed to make this engine breathe and scavenge well.
In the final stages of engine installation we just modified the primaries as I intended. Cooling system needed to be modified to fit the manifold in the car as the engine is really in the nose of the car but again we have a far superior and lighter item than something available commercially that is not some expensive works/motorsport stuff.

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The next stage involved my internal battles. I always wanted to do an ITB engine with Standalone ECU but again I always wanted to do a bike carb conversion as well.

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As I missed the days of simplicity with the carburetors and wanted to remove all the weight possible from the car, I opted to buy a set of Keihin CVK38 carbs from a ZX7R. I chose the size with midrange torque in mind and to keep the car streetable, CV carbs are the bomb.

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As no off the shelf manifold exists we made it from scratch with mild steel as I didn't have access to other materials at the time.

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Also, when You buy something used here in Balkans, it probably doesn't work. With that in mind we first installed the intake on the engine that was already in the car so we would be sure everything works before putting it on the expensive built engine. Only one slide of four worked so I had to rebuild the carburetors with new diaphragms and seals. That actually made me happy because I actually learned something new about CV carburetors and I was also positive that I have something that shouldn't be a nuisance in the future.

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The heater system needed to be removed from the car to fit the intake and we also removed power assisted brakes so I don't have to pull vacuum out of the intake that would disturb the intake pulses in the combustion process.

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To jet the bike carbs properly for car application some parts are needed that I'm still waiting from UK because of the whole situation in the world.
When parts for the jetting arrive, we will plug in the Innovate Wideband sensor and jet it on the road as well as going to a dyno to get the data.


For ignition I chose the Magneti Marelli distributor derived from a Fiat Uno, it works well for a baseline and it was the simplest thing to do at the time as I didn't like the idea using a standalone ECU that I had at the time just to control the ignition without fuel.

I will eventually fiddle with ECU powered ignition box since I can't get the timing curves ideal and I'm probably loosing about 20% of potential power on the timing alone.

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During the installation most of consumables we installed new and after a few test runs it was obvious that the stock engine mounts wouldn't handle the engine so I bought Strongflex Polyurethane engine mounts.

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Also we had to make some small modifications on the engine block and auxiliary equipment to make sure it fits and works properly.

I got the Vernier pulley made so we can degree the cam properly.

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With engine installed and tested I needed to get the exhaust done for the car.

Made a few phone calls and nobody offered what I wanted so with a lot of luck and some amount of money I accidentally found 12 year old NOS lightweight muffler and resonator made by Vitomir Jankovec that is allegedly in some way associated with Akrapovič.

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Both the muffler and resonator weigh 4.8Kg together and do a great job cancelling the noise while providing excellent flow, exactly as I wanted. I couldn't be happier with the exhaust and I'm really fortunate as the thing weighs less than some titanium stuff on the market.

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Car is currently running without a proper setup and will be set up and dynoed in near future.

I will try to log the build here and make updates when I can.

Stay strong and enjoy the photos!

Regards

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Next on the line was testing the engine.

At that stage the carbs still weren't jetted properly, so I had a chance to test something I never did before.

Go full throttle on the first day and not seat the rings properly.

I know I was doing the damage but the idea was to build a bottom end from scratch so who cares, right?

Well I care since i screwed up rings really good and went to the dyno like that and that costs me power. These days I really don't have time to do it again so I'm driving it as it is with oil residue on my spark plugs and compression loss.

First test, the car didn't have any midrange but was really good on high end with the new unseated rings.



Then I bought the exhaust and we trial fitted



Even with the info I had at the time I wanted to go to the dyno before I grenade the engine in bits to make some conclusions about the stroke and valve springs.

With the symptoms we made 100hp:

1. New head gasket leaking water in cylinder number 2
2. Oil residue on spark plugs everywhere except number 2
3. 10.5bar of cylinder pressure on all cylinders
4. Valves not shimmed properly
5. Carburetors vacuum leaking on intake hoses
6. Ignition Advance Curve not ideal so I tuned the car on the road to be driveable

I know how the engine behaved when i first drove it so it certainly has more power in it even though the bottom end is bone stock.

The dyno plot looks like this:

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What we know from the plot is that:

1. Components are working in harmony and not colliding with each other
2. Power drops after 7500RPM after the engine gets to a physical rev limit
3. Head, cam, intake and exhaust can all support more power
4. We need to go up in revs to use all the cam has to offer
5. Valve springs are most certainly too soft for the application as it is
6. Stock bottom end without lightening doesn't like revs due to geometry

My next idea is to fit everything on the standard 1242 block and dyno it again to see what happens,although my static CR would fall under 10:1 and it's too low for this cam.

I made a halt on the project as it's very busy at work so this is going to wait for some while to progress.

I will most certainly build a decent balanced bottom end but something in the lines of 1242 crank with 72.5-73mm bore using bike pistons and some longer rods that I find suitable. More on that later.

After that is done will do another head as I finally found some photos of the Panda Kit engine and how they made power, will post it here.

As I have no interest in messing around with Fiat 16V head I will try to find most suitable bike head and go that route next like they do with A-series Minis (BMW K head) and Bergcup cars in Germany. ( Hayabusa or CBR heads)
 
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As I've had very little info of the Panda Kit engine at the time, I was under the impression that I can get close to 100hp per litre on 72x84 engine without any massive witchcraft but it's not certainly true at this point.

I know by the rule book they can use up to 35mm intake valve and they did.

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As You can see the chamber design doesn't have anything to do with stock as well.

They also probably used a blank casting and drilled the stem holes differently to fit that valve sizes. Shimless buckets as well as the titanium retainers and beryllium bronze seats.

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Cam selection quite more radical than mine.

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Steel crank and coated pistons.

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If I dig out some more I will post it.

The only reasonable explanation for using the 8V head in motorsport is:

1. Easy to get a lighweight valvetrain in to support revs
2. Easy to work on the engine (ie. when You convert 16V head to solid lifters You have problems with access due to cambox design)
3. Redesigning the 16V cambox would be too expensive to justify the costs
4. Torque curves are good on 8V and for example my engine is a joy to drive in the traffic.
 
The bike piston options that I considered:

1. Suzuki GSX-R750 SRAD - 72MM bore, piston pin diameter smaller (i think 16mm) - would maybe work in 1368cc engine with piston or rod modifications, I have a used set in hands and I can measure if somebody wants to know more.

2. Kawasaki ZX-7R 1996-2003 - 73MM bore, piston pin diameter same as FIRE 18mm - when I have them in hands I can measure the pin height and how they sit

3. Kawasaki GPZ900 - 72.5MM bore, piston pin diameter same as FIRE 18mm - when I have them in hands I can measure the pin height and how they sit

The benefits of bike pistons are light weight, low friction design of piston and rings, low costs etc.

My ideas are to build a long rod 1300cc engine to sustain revs.

Our FIRE has 44MM journal diameter unfortunately so our options are limited. Every possible engine out there uses 45MM journals and very few of them are smaller then 44MM, most of them use short rods.

One option I considered is using a Nissan GA16DE/QG18DE rods modified to fit as the rod is really long and can probably be made to fit with custom crank grinding, piston selection and probably few more mods.

I didn't do any measurements since the project stopped but will do in near future.
 
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We calculated 11:1 from measuring the volume with the squished metal headgasket on a standard non skimmed head. Afterwards I had the cylinder head resurfaced and slightly skimmed but I also modified the combustion chamber so It somewhat zeroed itself out again.
 
pozdrav, super projekt, svaka čast! pratim dalje.

what caused the head to crack like that in first pic of post 9? overheating?
 
I binned the Cinquecento since I couldn't justify having two cars due to lack of storage so after a while of hesitation we decided to swap most of it in my Sei.

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So I bought the Ecumaster DET3 as a solution to get it driveable fast.

Swapped the upper end of things on to some junk 1242 block that I had laying around and paired it with IWP006 injectors onto 45mm TB with homebrew adapter. I revisited the cylinder head and modified it again to achieve more CR since the last setup wasn't enough for this cam to make power.

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With this in place I drove it for a day and wasn't satisfied with how the car was running with single throttle.

It lost most of the torque in the lower end of things due to cylinders robbing charge from each other in overlap and as well IAW gave me headaches with constantly adjusting idle with excessive timing. This cam had a really rough idle on single throttle so I had random pinging when IAW decided to bump the timing by itself.

Logical next step again was 4 throttles and that's what we did. We hacked the homebrew manifold that was built for Keihin CVK carbs and changed the design to fit 46MM throttle bodies from a 750 SRAD.

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Since Sei is a daily everything needed to be done with keeping the heater system, power brakes and everything else untouched.

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Only thing that is changed recently is that the battery is relocated to the passenger footwell to make room for a proper venting system in the future. The stock venting system is really bad and I don't have any proper way or room to do a multistage dry sump with a scavenge pump.

I also added an electric Vacuum pump for power brakes that will be upgraded with a pressure switch when it arrives and also we will make a vacuum tank in the future to keep the pump from constantly running.

Due to Covid everything seems to arrive late so I'm still expecting the switch and the velocity stacks for the bodies and few other small things.

I wanted to try the setup with 1242 in place to see what are the limitations regarding the RPM on a long stroke 1368 and it's mostly related to the valve springs as were my suspicions from the beginning.

I ordered some valve springs to try and test and will do that when I have a chance. The car was sitting for 3 months basically because nothing arrived in time and I drove it every once in a while with stock throttle body and wasn't satisfied.

I'll for now enjoy driving it and keep tuning it to make it better every day since I missed not driving it every day.

In parallel I plan to build a 73mm bore x 84mm stroke bottom end with 12.5:1 CR next and maybe do another cylinder head with bigger intake valves to accommodate extra airflow that these bodies deliver.

I didn't gain so much in max power probably but driveability is a lot better now and fuel economy improved as I'm running Alpha N with this cam. I can now cruise at 4% TPS uphill in fifth gear at 1500RPM without any pinging or bogging down whatsoever.

If mods can please change the thread title to Seicento 8V Build I would be grateful.

Regards and wish You all a Happy New Year!
 
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I didn't update for a while as my free time is limited to do anything on the car.

The last thing that's worth mentioning is the valve spring update that went well.

I updated the valve springs with a set of BMW N54 springs and retainers so now the upper end goes in any revs without any issues.

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So this happened with the bottom end.

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Since this was an engine just to drive around and test, it was not important to me at all ( although it still works)

I've decided to go all out and do a proper bottom end now.


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I also bought a milder cam (dbilas 272° 10.2/9.6mm lift on 108 LSA) to make it more streetable and use it more - but we'll see eventually where does it go from here.

Nice update is also a 38 to 44mm throttle body as I plan to use it on a single TB again since the ITB is too loud.

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I also decided to make the car nice and to build it again so I started to collect new parts.

Latest of them being the Braid Winrace A wheels in 7x13 ET11

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