Technical 65' 500F engine rebuild

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Technical 65' 500F engine rebuild

AndrewHarvey

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Jan 17, 2015
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A sporting camshaft and bigger carb will give you a bit more zip - but changing a 500 for a 126 is a bigger jump.
There are no cheap gains- you want fast - you have to pay
 

jjacob

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Oct 2, 2012
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For the experts i would like to ask what is the effect of a sport camshaft on a stock 500 engine with or without a 28 carburetor and also what can someone expect for a 540/camshaft/28carb. Is this modification worth?
Thomas

I looked at modifying my current 1969 499cc engine by going with the 540cc kit and mild cam. What it gains is not very much. A few more horsepower and a little more torque. You are only adding 41cc, about 8% more displacement. Going to the 650 adds 30%+ displacement. I really believe that you should just buy a rebuildable 650cc engine and transmission. The cost to rebuild the 650cc is less than rebuilding the 499cc to 540cc. There are more options in cams, etc. for the 650. Plus the transmission gets you a little more relaxed engine rpm and synchromesh on the top three gears. You should be able to go from 18 hp to 30 hp without spending more than the cost of a simple rebuild and a mild cam. A no brainer to me.
If you are in North America getting the 650 engine and transmission is more difficult. If you are in Europe you have no excuse!
Just my opinion.
John
 

Ricambi Fiat 500

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IMG_1484171580.088276.jpg
$2800 I have 650cc engine with alternator reconditioned like new & synchronized gearbox with Fiat 500 driveshaft ready to fit & go. [emoji469][emoji106]?
 
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cdeorio

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So I took some pics of the Crankshaft journals. After closer inspection they look like they might be scored? I also includes some pics of the bearings as well.

After receiving the 540cc pistons (they are Nurals) and comparing them to the ones I pulled out I realize the ones that were in the car are much bigger in diameter. See pics attached.

Ricambi Fiat 500 I am interested in your 650cc engine and transmission w/ 500 axels. Can you tell me more? where are you located?

Chris
 

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cdeorio

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Few more pics of the barrels and block which is a 110F. Totally confused as to what was in there. Also looks like spacer possibly on the barrels. believe the bore is 77.
 

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Toshi 975

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It looks like the ordinal 500 crankcase has been bored out to take 650 barrels and pistons hence the spacer which will be about 1cm thick. Unfortunately that means you will not be able to fit the 540 cc kit. As for the crank it is difficult to tell from the pictures. Best to get it checked by an engine specialist.
 

gordinir8

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So you got a 650 There, not bad, but I think that crankshaft need to be overhauled.
As Toshi said go to a specialist he will tell you what you must do.
 
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cdeorio

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I got the correct pistons and barrels. I was wondering if someone could give me advice on the direction of the pistons as there are no arrow markings on them. I have attached a couple of pics that hopefully can help.

Haynes says they go a certain way.
 

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John,

Thanks for the info. So I purchased some new 540cc pistons and after looking at the camshaft was not going to upgrade it. But now after having it all apart, I was thinking I might as well upgrade it to a sport cam (passione500 has one that goes with 540cc that is a 35/75). If I replaced the camshaft and the crankshaft isn't worn then new standard crankshaft bearings would be ok?

Also, now that I am thinking about the camshaft upgrade what else do I need to change or be concerned about?

Chris

Hi Chris, Having upgraded my cam (35/75-75/35) in my 126 engine I found that you must just check that the valve spring cap underside will not contact the top of the valve guide when on max lift. Check the max lift on the cam (details should come with the cam) multiply this figure by 1.5 (rocker ratio) this will give you the max lift at the valve. Get your engine shop to measure this and check that you have sufficient clearance available. If not they can simply increase this by taking metal from the top of the valve guide, good luck with the rebuild.

Ian.
 
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