Race Engine Forum UK

Hello Guy,
Together with my friend we have started building a Fiat Seicento with 1,4 16v Fiat engine(used in Panda for example). The car is going to be used for rallies. Right now all car is completely stripped and standard engine will be prepared shortly.
I have few questions regarding porting of head, throttle bodies size and exhaust manifold design for this engine.

I have attached few pictures taken today that show dimensions of the valve seats, ports and valves. If you need any other dimensions then just let me know and I will make them and post here.

What we would like to get from the engine is about 150-160HP with driveable torque from about 3,5- 4,5krpm. We have a short ratio 6 speed straight cut gearbox with LSD.

The question is: How do you think we should modify the inlet and exhaust ports. The head has quite bad short side radius as it looks like the inlet port has sharp angle. The ports also look very small. The casting is very bad and rough as can be seen on the pictures.
Should I modufy the valve seats just like you recommend for 2.0l TC engine?
What do you think of the standard valve design- can we gain something from modifying them?
Standard CR is 11:1 - I am thinking of rising it to 12:1 or even 12,5:1 by using Fiat 1.2 16v pistons(it has smaller dish than 1.4 piston)
What size of throttle bodies would you recommend for that engine. I am thinking of using 4x38mm. How long manifold should I make?

Cams.
We have for the moment two set of camshafts for this engine, hopefully one o them will be suitable, if not then we will try to get cams that you will recommend.
1. 9,2mm lift and 276deg duration
2. 9,2mm lift and 259 deg duration
Inlet and exhaust cams are the same and if neccesary then I can mix the sets

What size and lengths of exhaust manifold will be good for this engine.

We would like to change the hydraulic lifters to solid lifters but there it will be very dificult to check the clearance after the conversion as there is no way to see the cams as the cambox is closed design with no way to put a "gap" gauge so maybe you know o some method of proper clearance measure method for such engines?

I hope I have described the engine correctly, if you need any additional ino just let me know and I will do my best to get all the data as soon as possible.

The engine will run on Megasquirt EFI just like simmilar 1.2 16v engine used in Fiat Cinquecento described in Megasquirt topic(we got recently 122HP from that setup).

I will post results and dyno feedback as soon as the car is ready

Thanks for help.

Today a Flex-Hone has arrived so I will be able to finish the bores properly.

Tomasz, hi

thank you for your well-laid out post and I'm sorry for not looking at it sooner.

First I want to say that 1) I don't agree with using cast pistons you should be on FORGED and 2) no way can you run hydraulic lifters over 7000rpm so that is going to severely limit your power. Get som solids made!

No, as for the rest. I need to know:

1. The angle of the inlet port to the head face
2. A VERY good photo showing the SSR - I need to get an idea of the dist from the port floor where the curve starts to the valve.
3. I need the through-diameter of the inlet port splitter and ex too.




If the head was full spec - and they are quite a good sized inlet valve for that 1.4 motor, easily capable of 40% more power than std or more with the right cams and fuel system, and I would probably be looking at anything from 18mm - 22mm dia in the splitter bore, but first I want to know the production size. If I read your pics right the inlet port outer face is 35.8 x 21.4mm?The port outer may need some enlargement.

I figure the inlet ports have quite a good downdraft angle but before advising on valve and seat mods I want to know (1) above. The valve ratio is not good, in 27mm ex 22.4mm dia, E/I (relative valve area ex-in) is only 69% of inlet, but you might have to live with it unless you can get some bigger made. You really want E/I valve ratio of 75% which is a 26mm ex valve.

GC

Thanks.
I will make all the measurements tommorow together with pictures and post it here.
Tomasz

You are absolutely correct about the hydraulic lifters but changing them to solid lifters is a non-starter. There was an interesting article in a recent edition of racecar engineering that suggests someone has developed a generic technology for this sort of thing but I've been unable to find further information on the subject. For all intents and purposes you are stuck with those lifters and subsequently near standard lift. We've tried all sorts with these engines but because of the way the head is assembled there is no practical way to check the gap on a solid lifter and definitely no way to shim it up without dismantling the head again which rather defeats the object.

We succeeded in squeezing 150bhp out of an equivalent block with an 8v head but it was undriveable, we settled on a configuration that gives about 135bhp. A 16v head should definitely give you the flexibility to get to 150bhp with a more subtle cam profile (because with those hydraulics lifters you are going to be limited). On the downside the equivalent "works" rally engines (slightly smaller capacity) are only producing 130bhp contrary to the information they were publishing which suggests there is even more to it.

Julian, hi

I'm stuck with that one, because I don't know what the top of the head and bucket layout looks like...

G

Without a suitable diagram it is a bit hard to explain but basically once the camshaft is in place there is no way to get to the top of the lifters, you have to remove the camshaft to get to them which rather defeats the object of measuring the gap and changing the shims (or whatever adjustment mechanism you care to use).

Remove the cam to adjust setting, sure, but what is the difference betw that head in that repsect and most other 16v heads where solid lifters are used, with top hat underneath? If you can measure the clearance with feeler gauge and then take the cam off and remove the lifter to adjust the top hat thk, what's the problem? I assume they are direct acting not rockers ike this 1.6 Punto HGT I had here a while back?

Either I am completely wrong about the layout or this is pretty routine stuff.

G

Hello,
I have made few measurements of the head yesterday and here is what I got:

inlet splitter area diameter 21,5mm
exhaust splitter area diameter 18mm

Angle of inlet port is about 30deg on the top and bottom of the port- I say "about" as I have tried to make it as accurate as possible with a piece of steel wire shaped like the inlet port and then I have measured the angle- it may be 1-3 deg off.

The camboxes in those engines are closed design and there is no way to measure the gap like in 2.0 L 16v v engine. Below is a photo of that cambox.

I thought about machining holes in top of the cambox and then close it with an aluminium plate so that I will get enough place to check the gaps.

I have attached pictures of SSR.

The layout is unfortunately very different - the camshafts are installed in an independent cam carrier that sits on top of the head with the tops of the valves protruding into it. Unlike previous Fiat engine generations this one does not have a split cam carrier, it is a single piece with the cams inserted from the side. Once the camshafts are in place over the valves there is no access at all to the top of the valves.



It isn't a good diagram unfortunately but I think it gets across the basic design (apologies for the misaligned perspectives but I had to piece it together from a few diagrams that I dug out)

OK, great.

In this case the running clearance should be set by measuring the tip height of the valve relative to the head and the bucket position in the housing. I see no reason why, after pre-compressing the gasket to ensure it is fully settled and by carefully recording the measurements and grinding shims to suit that this is not 'do-able'.

And I would set the benefit of doing that and using solid lifters against running with hydraulics any day.

More later,

G

Any feedback on what I said above?

GC

For the moment we have held the project until we know what should be done to the head ports and valve seats. We try to source a good pistons for this engine and there is a chance to get forged ones.
As for the shimming of the head there is a slight problem about it as the valves are at angle to the gasket surface and it will be easy to make faulty measurements. Any thought how to make it 100% precise?

Tomasz, hi

I won't get involved at all on race engine conversions and mods to units running hydraulics. This means you have to start examining how to measure accurately to get the data you need by the means I described or you're on your own.

As for pistons - you know I design them but you're not asking me to help on that. Is it because you expect the cost to be too high? It may not be! I don't know of anyone who's complained about GC pistons - after they have actually seen them. If cost is an issue all round find an easier engine.

You need to start examination of the true costs of this engine done GC style or done low-cost style - for no other reason than cost. If you come up with details carefully thought-thru on assessing how to shim up in solid lifters - and go that way - I will give you all the help you need on porting and seats. Otherwise, sorry, it just isn't something I'm prepared to dwell on because a 3 year old could make a unit on hydraulics a bit more powerful but I know you like to do things professionally and get the very best.

Please consider this carefully.

GC

I will send you an email about the pistons. As for the budget for this engine, well it is not mine so also not my money will be involved in it and I cannot decide about it. I am just there to help to build it and I will be doing all the EFI setup job which I have done fine in last 1,2 16v project(engine is developing 122HP at the moment).
I will sort those solid lifters out and install it after the head is ready as it will depend on the cams used in it(and the clearances).