Tuning 695 Engine Project

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Tuning 695 Engine Project

Hi there I about your conversion with interest. You must be very pleased with the results. I too have a 500 with a 650 engine and gearbox fitted by a previous owner assembeled with a sports cam and exhaust running the 123 electronic ignition, not sure of the spec of the camshaft though. I was particularly interested in you big valve cylinder head. My mechanic has my engine apart at the moment as itcwas leaking oil and needs new gaskets and piston rings as well as another few bits so I was wondering if it would be worth fitting larger valves at the same time. Is it an involved job and would it be of any advantage unless also having the head skimmed and flowed? If so would it maybe be better to concentrate in upgrading the carb instead, maybe to a 30mm as it's still running the standard weber 28 imb? With you experience I'd be interested in hearing you opinions. Obviously I'm not looking for wild gains but just something that might compliment the upgraded cam and exhaust. One last thing I was wondering was if the camshaft should have any stamps on it that would help identfy it's spec.

Thanks,

Colm.
 
Colm,

The guys that fitted the large valves for me (I can't do this type of thing) and matched the inflow tract to take the 32/28 carby took one afternoon to complete the work.

The size of the exhaust valve is not so critical as the gas leaves under pressure during the exhaust stroke whereas a larger inlet valve permits better breathing and a larger volume of fuel/air mixture during the intake stroke which results in a bigger bang and more engine power.

If you have to, matching the carby throat with the inlet by widening the intake tract removes any steps that may interfere with the 'laminar' flow of mixture into the cylinder. It is probably not critical for a street car.

For a larger capacity engine the carby may become a limiting step in extracting optimal power for the state of tune and most people will fit something with at least a larger venturi though the 28 IMB fitted to the 650cc engine should be enough (the 500cc engine ran a 26 IMB). If you want to go to a 30mm choke, you'll need to fit a 30 DIC or something like that as the IMBs only go up to 28mm (I think).

FWIW, my advice would be to fit the larger valves and use the carby that you currently have.

As to the camshaft, it may be stamped or if not, it can be profiled at any auto tuning place. At the least what you need to know is the opening and closing angles in each cycle given a particular clearance and the lift (height of the lobe).

Talk to your local mechanic and get his advice and let us know how you get on.

Chris
 
Chris, thanks so much for your advice. I don't really want to go wild as I'm running standard suspension and brakes and I know once you start tuning things can spiral and also reliability and drivability are more important than outright power. I just figured that as the engine was already apart it might be worth going the big valve route. I think your right the carb is something that can be tackled if needs be at a later stage. The decision then is just whether to stick with the standard 28 exhaust valves and go for 34 intake valves or maybe go 35 on the intake and 29 on the exhaust as you have done. Anyway I will take to my mechanic and see what he says. I'll let you know what transpires. Thanks again for the advice.

Cheers,

colm.
 
Hi Chris,
on the subject of replacement valves I was wondering if you could answer a stupid question? While browsing sites I noticed, as well as the valve size; 33, 36 etc and what must be the length there is a measurement of 7 or 8mm which I'm presuming is the diameter of the valve stem. I had thought 8mm would be standard for the 650 engine but I see measurements of both 7 and 8 mm listed on various sites for both fiat 500 and 126. I was wondering what was the difference and which would be usable for a 650 engine.

Regards,

Colm.
 
Colm,

The standard valves on a 650cc engine are 28mm (exhaust) and 33mm (intake) and both have 8mm stems and are also the same length (115mm).

I've attached a photo of the ones I pulled out of an old 650cc head to show the detail at the top of the valve stem as well.

Chris
 

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    Standard 650 valves.jpg
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Great! Post...

I'm embarking on a 750cc upgrade to my 600cc Fiat 500 R engine. I hope to do a similar threat once the block comes back from my engineer.
 
I promised an update on my new Polish 650 motor and gearbox in an earlier post so here goes...I recieved my new complete motor/gearbox from Poland after over a month of waiting for it. I hit a few snags but was able to get it installed thanks to the wealth of information I found on this forum. First problem...the starter was not new but remanufactured in Poland. It wouldn't spin reliably so I brought it to a local repairman. He said he never saw such a sloppy rebuild but was able to fix it for $100. Next problem...gearbox would not change gears smoothly. I checked everything in the clutch, linkage, etc. Ended up taking apart the entire gearbox to find that the gears were all machined very poorly. Haggled with the guy I bought the motor from and he refunded me $600 to cover a gearbox rebuild. I put it all back together without new gears and drove it the way it was for a few hundred kilometers. Not sure how long it will last but things loosened up and it shifts smooth now. Next problem...low engine oil pressure. The motor ran fine for some time (few hundred km) and I have been braking it in properly. The oil light then started to come on when hot at idle. Then it started to remain on almost constantly when warm. I checked oil level, raised idle speed, tried different oil grades (10w40, 20w50, straight 50), and nothing helped. The problem is progressively and quickly getting worse. I removed the idiot light and installed an actual pressure guage and I have no pressure when the engine warms up even at open throttle. I'm getting about 36 lbs when cold. I tried a new oil pump, oil pump housing, blew out all the oil passages with air, and nothing. I'm hoping it's not the bearings but I'm running out of ideas. Nothing like rebuilding a brand new motor. If anyone has any thoughts, let me know. Moral of the story...look for an Italian motor, and rebuild it yourself so you know it's done right. It will be much better than any "brand new" Polish crap.
 
Hi Chris, with my 500D shell now at the panelbeaters and most of the running gear sorted I'm turning to the engine. After much thought on whether to go mild or wild I reckon I'm going to go 695 with much the same overall spec as yourself. Just wondering which of the 695 kits on offer you used (and what you thought of it) and also whether you changed out your conrods or ran with standard?
Cheers Roger
 
Roger,

My 695 is deliberately on the mild side, rather than the wild side as I have to drive it on the roads and therefore tractability is important to me.

Most of the parts I got from Fiat 500 Ricambi in the Netherlands.

The pistons, barrels and rings came together (79.5mm bore)
Crankshaft is standard stroke (70.0mm)
This gives a displaced volume of 694.95cc.

Because the gudgeon pins are closer to the piston crowns when compared to the standard 650 engine, the conrods were longer at 130mm. These were expensive at 340.0 euros for the pair.

I got the reciprocating parts balanced at a local tuners (Barnes Auto).

Flywheel is standard.

Camshaft is 43/77 77/43 and is fairly sporty. Ignition is a 123 electronic unit.

Valves are 35mm inlet and 29mm exhaust on a standard (new) 650 head. Valve seats are hardened and the head gasket is copper.

Exhaust is a nice twin pipe one which emits quite a bark.

Carby is a 32/28 Dell'Orto FZD.

It puts out 34bhp at the flywheel - about 50% more than a standard 650 at the same rpm (5500). Fuel consumption is more than the standard 650 but still excellent - I figure about 50 to 55 mpg (~ 5.5 l/100km).

Do it - you won't regret it. A bit more power makes these little cars great fun.

Chris
 
Chris,

I'm putting together a shopping list and have a couple of questions. Looking over the Fiat 500 Ricambi site I noticed they stock 82mm and 85mm cylinders/pistons but not 79.5. Did you source them from somewhere else, or am I being dense? (It wouldn't be the first time!)

Also they have 36mm valves but not 35mm ones - were these from somewhere else?

What year was the Niku you got the engine/drivetrain from? I'm thinking of picking up a cheap Polish one here in the UK, but I've heard the build quality can be poor. That said, I'm not sure how likely it will be that I'll find a 1970s Italian built one that's rough enough to justify using as a donor.

I'm still searching for a Dell'Orto FZD that isn't silly money, but they seem to be rarer than hen's teeth.

Cheers,
Matt
 
Matt,

On the invoice, the pistons are listed as 80mm but are actually 79.5mm. They are there under Tuning and 'Piston Liner Kit, 80mm' (MO 1109).

I might have bought the 35mm valves elsewhere - I'll check. You may be able to fit 36mm inlet valves - whoever sets up the head will be able to let you know how big you can go.

The Niki was a late model (?1990) one that I got here in Oz for a song. It was a piece of crap and I used it mainly to learn on. I had the gearbox and diff apart and inspected by a mate who rebuilds transmissions for a living and he said it was fine, so it's in the car. The rest I either tossed or gave away.

It took me ages to find an FZD and I swallowed hard when I bought it, but it is a good carby and parts are still available. The other alternative would be a Weber 30DIC - they were used on Fiat 850s (I think) and there are still lots of them around. The main benefit comes from having a carby with an accelerator pump circuit which is missing on the IMB's.

Let us know how you go,
Chris
 
Thanks Chris for all the advice. I plan on starting my own rebuild thread once I've got all the bits. I take it you used the rear drum brakes and hubs from your donor 126? Did you source your disc brakes from Fiat 500 Ricambi too?

Matt
 
Yes they were from the 126. I rebuilt the rear drums with new pistons, pads, springs and drums.
The front brakes also came from Holland. They fit perfectly and are designed for 12" rims. Sometime I'd like to re-pipe the hydraulics so I can fit a twin master cylinder.
If you get a chance, I documented most of the rebuild in a thread on this bulletin board called 'Project Bambino'.
I'll follow your engine thread with interest,
Chris
 
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Hi Chris, I'm curious about how your brakes feel using 126 pistons and brakes on a 500 master cylinder? I am fitting 126 brakes to my D and was looking at the new master cylinder today. To get it to fit I will have to slot out the holes on the flange so it fits the studs on the pedal block, cut a whole through the battery panel to accommodate its length, fit an aftermarket brake switch and sort some extra brake piping. All this to achieve a dual circuit system when, frankly, I don't perceive the single circuit system to be so bad. It's not like the various fiat bulletin boards are full of stories of catastrophic brake failures! I've not worked out the ratios for each type of master cylinder, but even when I do, I'd rather rely on real feedback from someone who has the setup in their car and can really say how the brakes feel. Appreciate any comment you may have.
Cheers Roger
 
Hi Roger,

I may not be much help here as in this case my 'experience' is from an N = 1 trial. All I can say is that the original brakes were not very good, but had been severely neglected with both rear pistons seized and one of the front drums very much out of round.

At the moment the brakes are infinitely better but whether they are better than a good rebuilt standard system I can't really say as I've not recently driven other 500s for comparison nor do I have any stopping distance/pedal pressure data.
As I was up for a complete rebuild, I took the opportunity to move to the 4x98mm stud pattern so I could at least get better rubber. The rears are rebuilt 126 drums and the fronts are 12" discs.

Maybe I should do the whole twin system conversion, but at present I'm quite happy with the way the car stops. The guys from whom I bought the front discs reassured me that the standard master cylinder would be up to the job, so I took them at their word. If it is a smaller bore than the 126 m/c, then the brakes should actually be more 'effective', at least in terms of pedal pressure.

Unfortunately I've ditched both old m/cs so I can't measure them, but someone else on the list may be able to help.

Sorry I can't be of much assistance at present, but I'll search around for more information for you and see what I turn up.

Regards,
Chris
 
Thanks Chris, it was how the brakes "feel" that interested me. As it happens I should have done a little research before posting my question. I had assumed that fiat would have altered the master cylinder size over the years (italian motorcycle manufacturers used dozens of variations over the same timeframe) but it turns out fiat used the same 3/4 inch (19.05) size throughout. They started by matching this to 3/4 inch wheel cylinders all round and then moved on to 15/16 inch front and 5/8 inch rear (23.8 and 15.7mm) and eventually back to a combination of 15/16 front and 3/4 inch rear.

Now I could do a lot of maths to figure the ratios once looking at the pedal leverage setup on each car.... Or, I could ascertain that as I long as I stick with a known mix of wheel cylinders then I am at least matching what fiat engineers thought was a good mix! Since I'm going with the last settings used by fiat on a late 126 I'd like to think they had perfected the ratios so I'm not rushing for the calculator...

Cheers Roger
 
Interesting - thanks Roger. I have little information on the 126s and it looks like a conversion to a split system would probably not be of much benefit.
It's funny how metric nations use imperial parts, though I guess there is probably only a limited market for things like hydraulics.
Still, it should make it easier to get seals etc. if everyone uses the same measurement standard - or so you'd hope :p
Chris
 
for Jcang0408;

For an interesting ignition switch look on web-site of:- 'Fiat 500 Ricambi'---part number TU1031--the on/off switch is under the red flick-up cover, aircraft style
 
Hi Chris, I seem to recall seeing somewhere a picture of an oil pressure sender you had fitted to your car. Can't see it in this thread but am sure it was you? Anyway, as I recall it was a hollow hex that I assume was threaded male at one end for going into the block and female at the other to take the regular switch, and then drilled and tapped to take the sender unit at 90 degrees to the switch. Does that sound right? If so, did you buy the part or make it?
Cheers Roger
 
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