Hello all,

Having successfully changed my sparkplugs and got the ol' girl up and running, Pop and I have decided it's time to build an engine!

Sadly, we know nothing at all about engine building, so I was wondering if there was such a thing as a 'build your own engine kit'. Kinda like legos, but for grown ups who drive lego size cars.

The current engine is going fine, so this'll be a project to learn all about how to do engine-y stuff, with the end goal of making a 650cc engine good for somewhere between 40 and 800 hp (probably closer to 40).

The real issue is that I don't know what to order. There are lots of different piston sizes, cam grinds, lumpy thingies, rubber thingies, etc, and I'm sure that I can't mix and match at random. If there's no such thing as a kit, does anyone have a build/order list from a build that they did that I could steal?

Thanks!

A good starting point would be to read the stickie thread on here called 695 engine build by Bambino. Its a comprehensive guide to building a 695cc sporty engine that gets about 38hp

http://www.athenaparts.com/files/pdfs/Big_Bore_FIAT_500_web_eng.pdf

This is what I purchased......its also supplied by UK specialists

http://www.ebay.co.uk/itm/332147772785 :devil:

Yep, but Fuzzy is American....

http://www.ebay.co.uk/itm/HAYNES-V8...309362?hash=item1c47e588b2:g:I2EAAOSwp5JWVElQ

I do realise that you are in the US of A, but the easiest way to build a 652cc engine is----to buy a 2nd hand 126 (late type AIR-COOLED) engine, rip it apart whilst taking lots of pictures and making copious notes. My 652 engine produces about 34bhp at the flywheel, and my 500 will happily sit at 65-70mph. The 'Athena 700cc' kit requires some knowledge of the engine and also some machining of the crank-case in order to fit the bigger barrels. I CANNOT recommend that you machine a 500 crank-case out to the point that it will accept the bigger barrels.
Whilst the 500/594/652 engines are basically very simple, tuning them to give (relatively) large bhp increases is NOT cheap---bigger inlet valves, ported cylinder head, better camshaft, bigger carb, lighter flywheel etc.,etc.
I have written up a list of work to carry out in order to build a 695 engine, if you would like a copy, e-mail me direct. To use the info for a 652cc engine, retain the original barrels and pistons!
All the best with the project

I'm pretty sure both of those models are about the same displacement as the stock motor...

Thank you for the link to the 695, I think that will be very helpful. There aren't a lot of 650cc motors kicking around the states (or 126s), so it looks like I'll be importing.

For an engine this size, do you think I'll need two stamps in the post?

-Fuzzyface

Time for some dumb engine questions:

Lots of stuff to learn about internal bits, so here goes...

Crankshafts have different strokes, ranging from 60mm to 80mm. I understand what stroke is, but haven't found a good resource for when you might want a longer or shorter stroke. (If it's helpful, I'll be driving on roads). Can someone explain?

Is 79.5mm the largest you 'should' bore a 650cc motor if you're looking to not grenade your engine?

Like cranks, cams come in all flavors. 35/75, 55/85, etc, etc. How would you select the right grind for an application (other than voodoo)?

How do you choose a carb size, around all of this?

I know it's a lot of questions, but the sticky 650/695/Bambino didn't get much into why particular components were chosen...

-Fuzzyface

When creating the build spec. I was advised that:
For every additional 50cc see 2.5 HP
700cc is about as large as you go before it gets really serious / expensive.
Peaky cam makes for a difficult road drive so 35 - 75 is reasonable.
Stroke length effects compression ratio - this is key. Higher the CR more power.
Panda 30 head has two ports whereas the 126/500 has one. This means carb choice alters also.
Single port use a webber 28 or Dellorto 32/28
Twin port you can go "big" and run upto twin webber 45's in extreme circumstances
Bigger inlet valves are available - wisdom says leave exhaust as is

Whats your budget?
Will you get it lightened / polished / balanced / ported ?
Have you upgraded brakes?

Tuning engines operates the principle of diminishing returns once a basic level of work is carried out.

35 hp is straight forward and well within a home build.
50+ is getting expensive
60+ is expensive
70+ is specialist

I hope i am correct in the above. I researched widely before my build - but i may stand corrected.

If I may offer a small correction in that stroke alters the engine displacement. An engine with a standard crankshaft can be enlarged by a greater bore measurement but, at a certain point further enlargement of capacity can only be achieved by lengthening the stroke. When using what our American friends call a stroker crank it is necessary to have taller barrels to accommodate the longer throw and therefore piston travel.

Hi;
I got your private message and, yes, I would be only too happy to send you a copy of my 695 specs. E-mail me direct:- T[email protected] and I will send it to you.
All the 500/126 engine range have the same stroke---70mm (Abarth went to 76mm stroke and 76mm bore for HIS version of the 695) and this does not need to be altered.
You CAN bore the 652cc 126 barrels out to 79.5mm, but you run the risk of ending up with very thin skirting at the bottom of the barrels--I do NOT recommend it.
For just-road use, I suggest that you use a 35/75/75/35 cam (with new followers) with new timing chain and sprockets.
The standard Weber 28 carb can still be used. A nicely 'warmed-up' 652 engine will give you a real performance gain over the standard 500 engine without becoming very expensive. I will put all this into my e-mail with my 695 specs.

Hello all!

Thank you very much for the great advice.

My big objective here is to learn how everything works and be able to do more work myself. Basically, I want to be less stupid, and I've enjoyed the heck out of making this all up with my dad so far. We drive it every day (and it hasn't exploded yet!).

-When you talk about a 35/75/75/35 cam, what does that mean, both within the engine and in practical (driving) purposes? How might it be different from, say, a 40/80/80/40 cam?

-Understanding that longer stroke = more displacement, does that also mean higher compression ratio? My understanding is that higher cr = higher octane fuel needed to keep knock down. Is there a limit to what the cr should be in one of these motors? Is there a way to calculate cr?

-How would you select the proper head? What are the advantages/disadvantages of single vs dual port? How much carb does one need?

Finally, to answer the 'what are you planning to do with it' questions:

I don't really have a budget in mind. I suspect it would be cheaper to buy an already built motor, for around $3000usd, than build one myself, as 650cc motors seem to be quite expensive in the USA. However, the goal is to build something myself, so whatever.

Nearly all of my driving is on twisty backcountry roads, between 35 and 65 mph, so my ultimate goal will be to build something that can be driven in a 'spirited' manner under those conditions. I suspect 40-50hp with a syncro trans, front discs, and a bit of suspension work to lower it a tad will be what gets done in the long term.

I would love if I could squeeze more revs out of each gear, though, so I might look at what it takes to get things balanced/lightened, etc.

Thanks again!

-Fuzzyface

As it is just gone 11.00PM over here, I will sit down tomorrow morning and go through all your latest batch of questions. Don't forget to let me have your direct e-mail address in order that I can send you my '695' specs.
For a bit of 'bed-time' reading can I suggest that you obtain a copy of:---
"Four-Stroke Performance Tuning" by 'A. Graham Bell' The publisher is;--
'Haynes Publishing' and the 'Library of Congress' catalog no. is:- 2011943928
This is quite detailed book on all aspects of engine tuning--a fair part of which you wont need, but it will give you a good insight into engine tuning.
Just for interest, what is you real name--I can't believe that your parents actually christened you 'fuzzy-face'!

Thank you! Through the magic of Amazon, I'm already reading it (and now know what a '4 stroke engine' means...)

You should have an email from me in your inbox...

and my real name is Benjamin.

Sleep well!

-Fuzzyface