Tuning 650 Engine Questions

[telemike4]

Hi all
I am slowly and opportunistically collecting bits for my 650 engine build and have a few questions.

I currently have a 500 engine, a Panda30 head, and a NOS Weber DGF carby. I have the opportunity to buy a 40/80/80/40 cam at a good price.

Will the 40/80 cam be too much for an engine that I want for weekend drives?
Will it all be too much for the 500 engine casing? I heard a long time ago the 500 case wasn’t strong enough and it was better to start with a 650 case (which I don’t have). I don’t know how true this is though.
If I’d be better with a 650 case, where might I source one? I’m in Australia and it will be quite difficult and costly to get one here I think.

I’m a bit of a way off the engine because I need to finish the body, but since I have the chance to buy this cam I thought I’d ask.

thanks

Michael

 

[Bounding Bambino]

I have a 40/80/80/40 cam on my 540cc build. Again, i haven't dynoed it. Will be happening this spring.

For the stock cylinder setup. You definitely are leaving more to be desired if you plan to stick with the stock cylinder displacement. The extra flow of the panda 30 head will not exactly show the best results.

The stock block has somewhat of a limit if you plan to go with larger cylinders. The 540 kits on the market will fit with out case modification. IMO & IIRC 595cc is kinda the limit to fit on the stock 500 case. It all depends on your resources. If you have a shop that can weld and reinforce the stock case, the sky is the limit really. Most go with a 650 case, and work their way up from there. Obviously dependent on resources and budget. The 650 case opens a much larger world of modification. However there are other parts required too. Like a 126 transmission, or at minimim the belhousing from it. As the 500 and 126/650 case have different starter positions and require the matching belhousing.

Honestly its lost hp if you throw on the panda 30 head, and other go fast goodies, and keep the stock 499cc displacement.

A 540cc kit with a panda head and that cam, might not be too bad of a combo. Just depends what your expecting from the finished engine performance wise.

 

[Toshi 975]

I have built both 594 and 650 engines on the 499cc crankcases with no problem. The necessary 10mm spacer plate that fits under the larger cylinders also adds a little strength as does the fitting of an alloy sump without a gasket. Structurally there seems very little difference between the 500 and 126 Niki crankcases.
You have done very well getting your hands on a Panda 30 cylinder head and that would suggest to me that 650 would be the natural way to go, same ccs as the Panda.
I do know that only 97 126 Nikis were officially imported into New Zealand but I think Australia took a lot more so you may have a chance of picking up an engine , maybe tranny as well. There have been a number of guys from Oz posting on the Club 126 UK forum, one or two proposing to do engine swaps so might be worth keeping an eye out there.
I can weigh a bare 126 crankcase if you wanted to know the weight for shipping.

 

[Bleeding Knuckles]

Hi telemike, congratulations on obtaining a Panda head they are becoming difficult to find. Depending on how far you intend to go with the engine tune I would council you to have the area between the valves inspected for a crack between them, this is a known problem and the standard repair will add strength to the area, you could change the inlet valve and go up one mm to 35 at the same time as this helps the engine breathe. Check that the Weber DGF was intended for a Panda and/or check the jetting as these carbs were intended for different applications (if you need the numbers let me know) Depending on your exact cam the 40/80 gives some 7.70 of lift x 1.5 rocker ratio and you get 11.55 lift (at the valve) you should check and measure the valve movement for clearance above the valve guide as contact with the valve spring cap underside can happen, check for valve spring binding too. While you're doing all that change the valve seals as they will be well past their best. Any questions get back to me.
Ian.

 

[the hobbler]

Hi telemike, congratulations on obtaining a Panda head they are becoming difficult to find. Depending on how far you intend to go with the engine tune I would council you to have the area between the valves inspected for a crack between them, this is a known problem and the standard repair will add strength to the area, you could change the inlet valve and go up one mm to 35 at the same time as this helps the engine breathe. Check that the Weber DGF was intended for a Panda and/or check the jetting as these carbs were intended for different applications (if you need the numbers let me know) Depending on your exact cam the 40/80 gives some 7.70 of lift x 1.5 rocker ratio and you get 11.55 lift (at the valve) you should check and measure the valve movement for clearance above the valve guide as contact with the valve spring cap underside can happen, check for valve spring binding too. While you're doing all that change the valve seals as they will be well past their best. Any questions get back to me.
Ian.

I can only speak from my own experience. At Radbourne Racing we took the 500 engines up to 652cc (the same as the Mk2 '126'). This as far as I can recommend for the 500 engine, because if you go any larger, there is a good chance that when you open up the crankcase to accept bigger barrels, you will remove the sealing 'lip' on the crankcase that the barrel sits on, with a gasket (or as I use, a 0.3mm copper ring). We never, to the best of my knowledge, had a problem with this 'upgrade' and we did a fair number. As Abarth did not have the 126 engine to play with, he increased the stroke (up to 76mm) in order to bring the engines up to 695cc.
If you have to fit a spacer between the barrels and the crankcase, this will help stiffen the crankcase, as will fitting an alluminium sump (with 'goo' instead of a gasket) just be careful how you spread the 'goo' on the mating surfaces, so non is squeezed into the sump when tightening the sump-retaining screws.
As people have pointed out, whether the Panda30 head gives much of a gain on a moderately tuned engine is debateable, but as you have it, you might as well use it. I would suggest that you carefully 'port' it and go up to 35mm inlet valves---for 'road-use-only' you can leave the exhaust valves standard. You will have to carry out a fair bit of 'fettling' to the cylinder head (i.e. chop the top corners off!) to enable the standard fan shrouding to fit round it.
Jacques (bounding bambino) pointed out that the 126 crankcase and 500 bell-housing are not compatible. If you DO manage to obtain a 126 crankcase, you will need to fit a 126 bell-housing to your 500 gearbox (it fits), a 126 starter, starter shield, starter brace and dedicated '3rd starter mounting bolt'. In your situation,it might be better to obtain another 500 crankcase and go from there.
The 40/80/80/40 cam will be fine--about as 'wild' as you would want for 'road-use-only' I have put my thoughts regarding the tuning of the 500 and 126 engine down on paper---if you would like a copy, feel free to contact me direct--- tommontagu @yahoo.co.uk

 

[telemike4]

Hi, thanks all for the informative responses.

I had forgotten that if I moved to a 126 case then I would need a 126 starter and bell housing etc. I’ll keep my eyes open but that sounds like it will be difficult or costly (or both).

I was planning on 650cc cylinders to make the most of it.

I got the Panda head about 25 years ago at a decent price after helping someone stranded in their 500. I didn’t know then how good a deal it would prove to be in the long term.

And I forgot to mention, from the same person I can get some 35mm and 30mm valves. I was going to fit the 35mm inlet valves and port it, but I had read in other people’s posts that it’s not really worth upgrading the exhaust valves.

The DGF carb is labelled for a 126.

And finally, the Alquatti A12 40/80 cam is marked with “0,20” in mm for the inlet and exhaust. That doesn’t look close to the measurements Ian mentions above, or is one of those measurements imperial and one metric. Puzzled on this one.

Michael

 

[Bleeding Knuckles]

Michael, I would only fit the 35mm valves to the inlet as the room left available between it and the exhaust is minimal, porting the head will take time as there is a lot of material to remove and it is best to match the exhaust elbows too. The DGF should have the correct jetting, but check anyway. As far as your cam is concerned you should have detail (or be able to obtain) of the cam as in the pic - it shows all the cam profile(s) on my cam and something similar should have come with yours.
Ian.

 

[Toshi 975]

Could that A12 actually be A/2?

 

[the hobbler]

Michael, I would only fit the 35mm valves to the inlet as the room left available between it and the exhaust is minimal, porting the head will take time as there is a lot of material to remove and it is best to match the exhaust elbows too. The DGF should have the correct jetting, but check anyway. As far as your cam is concerned you should have detail (or be able to obtain) of the cam as in the pic - it shows all the cam profile(s) on my cam and something similar should have come with yours.
Ian.

 

[the hobbler]

As Jacques has mentioned, just take the inlet up to 35mm---leave the exhaust as standard. The valve clearance of 0.2mm (8thou) is a normal setting for these cams---COLD. The fun will come when you try to adapt the fan-housing to fit round the corners of the Panda30 head---a hacksaw and file will initially be your main tools! (I know--I am in the process of doing that job myself. It might be wise if you did that job prior to doing a final build-up of the engine---that way you can give the crankcase a really good clean prior to putting all the engine together.

 

[Bounding Bambino]

Also fyi i have the same cam.

 

[telemike4]

The cam box (I only have a photo) does seem to be A2, what I thought was a line is actually where a pen has scratched through the paper. I can’t see the duration marked on it though (Perhaps there is some more documentation inside).

I think I have enough info now to know these parts will work as a package. I will organise to buy them and then post some photos when it is clearer exactly what I have. And I can tell the back story on the parts as well.

thanks again

Michael

 

[Kiwi126]

As a noob to the forum, it was great reading through this, and I hope the build has progressed well for you Michael. I am looking to fit a 40/80 cam to my 126 based in NZ. Hope you can source a 126 engine and box in Aussie should that be the way you want to go. I may be able to help with that if not - feel free to drop me a line.

Cheers,

Andy

 

[vitorio]

On this topic, does anyone know the cam profile on the stock 650 cam? I bought a 500L with a 650 engine fitted, and in time i might want to try and spice it up a bit, i just cant really find any info on whether a 35/75 cam would be a significant upgrade, and given the cost of these things...

 

[Toshi 975]

On this topic, does anyone know the cam profile on the stock 650 cam? I bought a 500L with a 650 engine fitted, and in time i might want to try and spice it up a bit, i just cant really find any info on whether a 35/75 cam would be a significant upgrade, and given the cost of these things...

The 35/75 is generally regarded as a sport camshaft sometimes referred to as fast road/rally. I ran one in a tuned engine and it worked well for me the 40/80 is another notch up but still good for around town as well.

 

[smart51]

The 650 cam has a duration on 263 degrees (depending on year). A 30/70 cam has a duration of 280 degrees, a 35/75 cam has a duration of 290 degrees and a 40/80 a duration of 300 degrees.

Take your pick, but go too far an your bottom end losses would outweigh any top end gains you would make. Fine for racing, but how often do you rev your car that high?

 

[vitorio]

The 650 cam has a duration on 263 degrees (depending on year). A 30/70 cam has a duration of 280 degrees, a 35/75 cam has a duration of 290 degrees and a 40/80 a duration of 300 degrees.

Take your pick, but go too far an your bottom end losses would outweigh any top end gains you would make. Fine for racing, but how often do you rev your car that high?

Thanks, that is what i was looking for, seems like a 35/75 is already a significant upgrade from the stock cam, so well worth going for. Will keep that in mind for when the engine comes out of the car.