Technical 650cc Engine Upgrade

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Technical 650cc Engine Upgrade

Pete145

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Hi everyone,

I've been the owner of my 1971 500 Lusso for about a year now. It was restored pretty well before I owned it so, to be fair, my work has been limited to fixing up some missing trim and a few tweaks here and there on the engine (some oil pressure issues, brake lights, oil leaks, the odd gasket here and there).

The engine has had some work. The head has been gas flowed and ported, high lift camshaft has been fitted, better carb, better exhaust. This has added a few horses and it now runs at about 33-35bhp.

A year in I'm seriously considering upgrading the car to include a 650cc engine and gear box, as well as fitting disc brakes.

Don't get me wrong, generally speaking I do love and enjoy the car as it is. But where I live is quite hilly and, I'm not gonna lie, I do find it hard to drive the car in modern traffic, which is a shame.

I haven't got the space and the appropriate tools to swap the engine, and I'd be looking to outsource the work of finding and fitting the new engine. Disc brakes I could handle, but while I'm at it I'd outsource that as well.

So, here's my question. Can anyone recommend where I could get this work done? I've used Middle Barton Garage for some engine repair work, and was pleased with what they did. But I'm all ears in regards to recommendations!
 
If you are getting that sort of power from a 499ccs engine then fitting a standard 126 652ccs engine would not help you. However if you were to go with a 652 then swap your tuning parts it could be a different story. What carb do you have on there and has the inlet port been opened up on the head ?
 
I'd agree with Toshi. You will only get about 23hp with standard 650
 
I`m assuming a 33-35 is only a guestimate and if it`s a 500cc engine it`s probably a bit optimistic:) It would be nearly a 100% power increase.


As Toshi said if you used your upgraded parts on 650 engine, this would make a nice difference. Also you would be better off keeping the standard gearbox if you want to go up hills faster as the 126 has a "longer" final drive.
 
The engine has had some work. The head has been gas flowed and ported, high lift camshaft has been fitted, better carb, better exhaust. This has added a few horses and it now runs at about 33-35bhp.

Hi Pete,

My 695 with similar mods gets around the same horsepower (~50bhp/litre).

I could get more but it would take some serious raising of the compression ratio, tuned exhaust, very lumpy cam etc. and would most likely result in an engine that was unusable on the road.

Mine has been mildly breathed on, starts and idles well, isn't peaky and is a hoot to drive, particularly in my hilly suburb. :D

My humble advice is to do the upgrade but don't overdo it unless you want to go racing. :)

You'll find plenty of friendly, helpful advice on this part of the forum.

Chris
 
What carb do you have on there and has the inlet port been opened up on the head ?

I'm pretty sure it's the 126 carb, and the head was skimmed, gas flowed and ported. It's the car from Classic Car Rescue, which aired on Channel 5 about a year ago. Jondel Racing did the work on the head.
 
I`m assuming a 33-35 is only a guestimate and if it`s a 500cc engine it`s probably a bit optimistic:)

Oops, sorry, my mistake! I've added 10 bhp! According to Jondel it's achieving 23-25bhp now.
 
I'm pretty sure it's the 126 carb, and the head was skimmed, gas flowed and ported. It's the car from Classic Car Rescue, which aired on Channel 5 about a year ago. Jondel Racing did the work on the head.

If it is a 126 carb then it will have 28 IMB on the casting as opposed to the 26 IMB on the 500. The inlet port diameter on the 500 head is 26 mms and 30 mms on the 126 so I assume the tuning guys took that into account. Did they increase the inlet valve size? Also if they put together a higher revving engine did they upgrade the standard cooling fan?
 
Did they increase the inlet valve size? Also if they put together a higher revving engine did they upgrade the standard cooling fan?

They did increase the inlet valve size, but they didn't upgrade the cooling fan.

So, what I'm hearing is that a 650cc engine upgrade won't give me any more bhp than I'm already achieving from my modified engine. Is that correct?
 
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