Small block super imola 186

[Lord-Spanner]

Morning folks,

As an all or nothing type bloke I've decided to go balls deep with an engine for my project Li150, no it won't be cheap but I can't take it with me as it were, so decided on a Super Imola 186 for a small block casing Li150, now when I put the block on the engine casing it's hanging on by a thread with the base face, personally I don't like the look of it (see picture with pencil line on block base where the case sits on the block base) as its asking for a leak, I have a few options I've looked at...... get the original casing welded up to make the face bigger, get a spanish later casing if I could find one with a thicker flange and gasket face or to buy a new SIL 150 casing and chain case from Scooter restorations (which is my fave option)

I don't want to modify my original lump as I want to keep that stock for resale point of view if I ever decide to get rid.....

Not sure I'd find a spanish casing and possible more trouble than it's worth If its cracked any where......

So that leaves the new sil150 case from scooter restorations which has a thicker flange and gasket face, so has anyone done this combination of a super imola 186 on a new sil 150 casing and have you come up against any problems with deck height, base gasket/head gasket combinations and or squish etc

Thanks LS



https://www.flickr.com/photos/192653958 ... ed-public/


https://www.flickr.com/photos/192653958 ... ed-public/

[Warkton Tornado No.1]

If i were assembling such an engine, besides the cylinder kit, I would consider the choice of crankshaft, specifically stroke & conrod length. i state that because there are significant advantages to a greater stroke & longer conrod in fine tuning the geometry relevant to port timings & the power characteristics of the engine.

However, presuming that you have gone with the standard format, you need to consider squish, compression ratio & the transfer & exhaust port timings.

i would suggest you put the engine together, omitting the rings & wrist pin circlips & see what you have. Do not fit gaskets & see what you have got.

I never, ever fit head gaskets, but that is up to you. The thing is, IMO it would be great if you 'discover' that you require some form of base packing, say, 2 mm or so. Even if base packing was less, I'd strongly advise that a metal base packing/gasket be used. They not only are reusable, but add some 'integrity' to the build with durability. not forgetting the fact that they serve as templates in transferring (excuse the pun....) port geometry from cylinder to case & vice versa.

With a good petroil proof sealant (NOT blue Hylomar) i would not be too concerned about the lack of wall thickness, especially as any metal base packing/gasket will sit outboard of both faces it is sandwiched between. In my time I have had to go with considerably less wall than you have!

[Lord-Spanner]

If i were assembling such an engine, besides the cylinder kit, I would consider the choice of crankshaft, specifically stroke & conrod length. i state that because there are significant advantages to a greater stroke & longer conrod in fine tuning the geometry relevant to port timings & the power characteristics of the engine.

However, presuming that you have gone with the standard format, you need to consider squish, compression ratio & the transfer & exhaust port timings.

i would suggest you put the engine together, omitting the rings & wrist pin circlips & see what you have. Do not fit gaskets & see what you have got.

I never, ever fit head gaskets, but that is up to you. The thing is, IMO it would be great if you 'discover' that you require some form of base packing, say, 2 mm or so. Even if base packing was less, I'd strongly advise that a metal base packing/gasket be used. They not only are reusable, but add some 'integrity' to the build with durability. not forgetting the fact that they serve as templates in transferring (excuse the pun....) port geometry from cylinder to case & vice versa.

With a good petroil proof sealant (NOT blue Hylomar) i would not be too concerned about the lack of wall thickness, especially as any metal base packing/gasket will sit outboard of both faces it is sandwiched between. In my time I have had to go with considerably less wall than you have!

Thanks for the reply ,

What I going to do was get the parts over a period of time because of cost (new race crank, 6 plate clutch, variotronic/electronic ignition, chamber pipe made for the super imola, VHSB carb etc and to finish a 5 speed AF box) then dry build (well with a little oil) it with the standard S3 Li150 58/107mm crank I have without the use of gaskets like you say and see how that goes as far as timings (might need help with that part), squish etc, if the standard size stroke/rod combo works then go with a race version 58/107mm but if it would benefit from a longer rod go with a 58/110mm race crank and like you say use base packers/head gaskets to get the correct squish, port timings etc.

I think I will try a new SIL 150 crank case from scoot restorations unless there's a good reason not to? Mainly to avoid using my original casing for the sake of re-sale and for the thicker wall/gasket face which will give me piece of mind (better safe than sorry, be just my luck for it to bugger up) in the 80/90's when rebuilding my "A" series mini road/race engine I never liked blue hylomar anyway and don't plan on using it now or any time soon , kind of sets rubbery but yeah I would be using a very good quality sealing product for this build so there's no leaks,

Thanks again

[Warkton Tornado No.1]

If I don't suggest that you uprate your crankshaft, then somebody else will!

SIL crankshafts are good for such an engine only if they are re-rodded with a decent bearing. IMO you may as well go for a longer stroke, though whether you will find SIL webs in 60 mm these days, I don't know.

In which case, 61 or 62 mm stroke crankshafts become a tempting consideration. Go for the longest conrod available is my advice. Anything to lower primary compression

There are very good crankshaft builders & hopefully you will receive recommendations. Probably the best is a bed-wetting control freak that was once a friend, but power & money can change people.....

[Lord-Spanner]

If I don't suggest that you uprate your crankshaft, then somebody else will!

SIL crankshafts are good for such an engine only if they are re-rodded with a decent bearing. IMO you may as well go for a longer stroke, though whether you will find SIL webs in 60 mm these days, I don't know.

In which case, 61 or 62 mm stroke crankshafts become a tempting consideration. Go for the longest conrod available is my advice. Anything to lower primary compression

There are very good crankshaft builders & hopefully you will receive recommendations. Probably the best is a bed-wetting control freak that was once a friend, but power & money can change people.....

As I don't want to go to deep into it as dollar is tight and reliability might become an issue. But saying that yes I will be upgrading my crank shaft/rod (A Cambridge Lambretta one) but not sure on rod length yet, I wouldn't want to use a longer stroke crankshaft though just stick to the 58mm, but as for the longer rod then maybe if it has good benefits for the engine but would only be the 110mm rod on a 58mm stroked crankshaft.

[Andy B.L.C.]

Dunno if this helps...

https://youtu.be/uxH6COqZs10

[ULC Soulagent]

Decent power from a bolt on kit Andy
I’ve looked into this kit also along with the quattrini 210. As with most Tino’s barrels it will probably need tweaking too make sure all ports are of equal measure( previous experience with imola kits).mine had a 60/110 crank in it which like WK1 has said makes a vast difference.Me personally I would leave the bottom n top end rebuild too a professional tuner. Although it won’t do ur bank balance any good the outcome from it will have you grinning like a Cheshire Cat

[Andy B.L.C.]

Would be beyond my means, add to the list, quelle surprise..!. Still in the market for a small block mental barrel mind, just worried that the fuels that we're going to be stitched up with will be pissing on our bonfire...

[Psychedelicropcircle]

I think a standard LI crank won’t handle this power, twisted in a heart beat!

[Lord-Spanner]

Would be beyond my means, add to the list, quelle surprise..!. Still in the market for a small block mental barrel mind, just worried that the fuels that we're going to be stitched up with will be pissing on our bonfire...

Slightly beyond mine too but I'm gunna have a go (but was always messing and rebuilding 4 stroke engines 30 years ago and used to build and race a 26cc 1/5th scale 2 stroke remote controlled off road cars) and take my time doing it, I'm sure there is some kind of additive or octane booster about for these issues??

Decent power from a bolt on kit Andy
I’ve looked into this kit also along with the quattrini 210. As with most Tino’s barrels it will probably need tweaking too make sure all ports are of equal measure( previous experience with imola kits).mine had a 60/110 crank in it which like WK1 has said makes a vast difference.Me personally I would leave the bottom n top end rebuild too a professional tuner. Although it won’t do ur bank balance any good the outcome from it will have you grinning like a Cheshire Cat

Its a relatively new kit so I would hope those faults would of been ironed out Think I might go 58/110 to avoid any possible work inside the casing for the longer stroke, I'd love to get a pro builder to do it but like most dosh is tight so I'll be doing it, I might learn the hard way but we'll see, always got the stock motor to put back in it I like the sound of that though

Dunno if this helps... https://youtu.be/uxH6COqZs10

Very nice, looks like it was trying to take off

I think a standard LI crank won’t handle this power, twisted in a heart beat!

No it won't handle the power, my crank will be upgraded to a much better bomb proof race one

[Warkton Tornado No.1]

As a new or stronger crank is a 'given' then the additional costs in terms of money & time for a longer stroke are minimal just to accommodate.

As long as you can assess any necessary additional clearance for the increased stroke & operate a sanding drum in the crankcase, then that would be the only essential machining. Even that can be obviated by speaking to crank builders that will reduce the size of the conrod big end outer diameter!

Then, what have you GOT to do? Select base packing to ensure the correct squish with the chosen stroke/conrod/piston combination.

You don't need to match ports or modify port timings @ this stage. Many of us would, but it would be useful to measure & record timings & then just run the thing!

Inevitably, you will have reduced the transfer & exhaust durations from what the 'optimum' should be @ 58 mm stroke, but so what? Try what you have bought 'as is' & then you can think about what, if anything, you would change & approach the matter with some well learnt knowledge.

Two last pieces of advice. Think about your carburation & select wisely. Don't just follow the herd. Try & incorporate an effective air filter, even if you have to make your own.

[Lord-Spanner]

As a new or stronger crank is a 'given' then the additional costs in terms of money & time for a longer stroke are minimal just to accommodate.

As long as you can assess any necessary additional clearance for the increased stroke & operate a sanding drum in the crankcase, then that would be the only essential machining. Even that can be obviated by speaking to crank builders that will reduce the size of the conrod big end outer diameter!

Then, what have you GOT to do? Select base packing to ensure the correct squish with the chosen stroke/conrod/piston combination.

You don't need to match ports or modify port timings @ this stage. Many of us would, but it would be useful to measure & record timings & then just run the thing!

Inevitably, you will have reduced the transfer & exhaust durations from what the 'optimum' should be @ 58 mm stroke, but so what? Try what you have bought 'as is' & then you can think about what, if anything, you would change & approach the matter with some well learnt knowledge.

Two last pieces of advice. Think about your carburation & select wisely. Don't just follow the herd. Try & incorporate an effective air filter, even if you have to make your own.

Hmmmmm now that sounds like a very good plan so why not, thinking 60mm stroke with a 110mm rod, I do have the tools to sort a little grinding to accommodate a longer stroke crank if need be, better to case grind than grind the rod.

I'm sure some time with a calculator would be close then a little poz or neg on the thickness of base plate and head gasket would get the squish right, though some folk run with out head gaskets don't they?? so is it better with or without or is it dependent on squish measurements?

I might purchase a buzzwangley thing for that or just use the steel timing disc I have, we'll see on that one at a later date though as this will be a long slow process due to the cost of parts many other parts.

As for the carb/filter combo I'm thinking VHSB Delly and dependent on room a nice K&N filter(used these for many years on minis and remote controlled 2 stroke off road cars) If they do one the correct size, all that and I've still got the box to consider, deffo a 5 speed though.

[Warkton Tornado No.1]

As a new or stronger crank is a 'given' then the additional costs in terms of money & time for a longer stroke are minimal just to accommodate.

As long as you can assess any necessary additional clearance for the increased stroke & operate a sanding drum in the crankcase, then that would be the only essential machining. Even that can be obviated by speaking to crank builders that will reduce the size of the conrod big end outer diameter!

Then, what have you GOT to do? Select base packing to ensure the correct squish with the chosen stroke/conrod/piston combination.

You don't need to match ports or modify port timings @ this stage. Many of us would, but it would be useful to measure & record timings & then just run the thing!

Inevitably, you will have reduced the transfer & exhaust durations from what the 'optimum' should be @ 58 mm stroke, but so what? Try what you have bought 'as is' & then you can think about what, if anything, you would change & approach the matter with some well learnt knowledge.

Two last pieces of advice. Think about your carburation & select wisely. Don't just follow the herd. Try & incorporate an effective air filter, even if you have to make your own.

Hmmmmm now that sounds like a very good plan so why not, thinking 60mm stroke with a 110mm rod, I do have the tools to sort a little grinding to accommodate a longer stroke crank if need be, better to case grind than grind the rod.

I'm sure some time with a calculator would be close then a little poz or neg on the thickness of base plate and head gasket would get the squish right, though some folk run with out head gaskets don't they?? so is it better with or without or is it dependent on squish measurements?

I might purchase a buzzwangley thing for that or just use the steel timing disc I have, we'll see on that one at a later date though as this will be a long slow process due to the cost of parts many other parts.

As for the carb/filter combo I'm thinking VHSB Delly and dependent on room a nice K&N filter(used these for many years on minis and remote controlled 2 stroke off road cars) If they do one the correct size, all that and I've still got the box to consider, deffo a 5 speed though.

A head to barrel seal will achieved with a good spigot fit.

Race engine tend to run without gaskets, though not because the CR is not particularly high. Reliability is key. There are various suitable sealants but Loctite & Threebond are popular.

Head gaskets are a risk not worth taking & failure can wreck an engine.

[Lord-Spanner]

A head to barrel seal will achieved with a good spigot fit.

Race engine tend to run without gaskets, though not because the CR is not particularly high. Reliability is key. There are various suitable sealants but Loctite & Threebond are popular.

Head gaskets are a risk not worth taking & failure can wreck an engine.

I should hope the head to barrel is a good fit after the money it cost me, guessing a gasket is a weak point which could blow at any time causing major issues, I have my eye on the Threebond so will use that on the build, I'm wondering if there is anything I can get or do (to put in place of the base plate) to work out the thickness of the base plate so I don't have to buy to many base plates, but if buying several base plates is the only way then that's what i'll have to do

[Warkton Tornado No.1]

A head to barrel seal will achieved with a good spigot fit.

Race engine tend to run without gaskets, though not because the CR is not particularly high. Reliability is key. There are various suitable sealants but Loctite & Threebond are popular.

Head gaskets are a risk not worth taking & failure can wreck an engine.

I should hope the head to barrel is a good fit after the money it cost me, guessing a gasket is a weak point which could blow at any time causing major issues, I have my eye on the Threebond so will use that on the build, I'm wondering if there is anything I can get or do (to put in place of the base plate) to work out the thickness of the base plate so I don't have to buy to many base plates, but if buying several base plates is the only way then that's what i'll have to do

Fair question. Sometimes I have to remind myself of the loads of stuff I have amassed including base gaskets & packings

However, I usually have a good idea which can be based upon calculation but inevitably, a physical check proves the theory.

Besides Lambretta spares I have 100's of fasteners including M8 washers. They can always be found to be of a set thickness as they are stamped from sheet material such as 1.0 mm, 1.2 mm, 1.6 mm etc. You could cut some in half to fit between barrel & crankcase as packing & with some solder to measure squish get an accurate idea of what base packing is required.

Bear in mind that alloy base packings will compress a tad compared to steel washers, but you should get in the right ball park....

[Lord-Spanner]

A head to barrel seal will achieved with a good spigot fit.

Race engine tend to run without gaskets, though not because the CR is not particularly high. Reliability is key. There are various suitable sealants but Loctite & Threebond are popular.

Head gaskets are a risk not worth taking & failure can wreck an engine.

I should hope the head to barrel is a good fit after the money it cost me, guessing a gasket is a weak point which could blow at any time causing major issues, I have my eye on the Threebond so will use that on the build, I'm wondering if there is anything I can get or do (to put in place of the base plate) to work out the thickness of the base plate so I don't have to buy to many base plates, but if buying several base plates is the only way then that's what i'll have to do

Fair question. Sometimes I have to remind myself of the loads of stuff I have amassed including base gaskets & packings

However, I usually have a good idea which can be based upon calculation but inevitably, a physical check proves the theory.

Besides Lambretta spares I have 100's of fasteners including M8 washers. They can always be found to be of a set thickness as they are stamped from sheet material such as 1.0 mm, 1.2 mm, 1.6 mm etc. You could cut some in half to fit between barrel & crankcase as packing & with some solder to measure squish get an accurate idea of what base packing is required.

Bear in mind that alloy base packings will compress a tad compared to steel washers, but you should get in the right ball park....

That's what I was after really, just a ball park as it would not be set in stone until it was all (base packer, cylinder and head) bolted down correctly to check the squish, I will see if I can find some strips of different thicknesses of steel 1-4mm which would work with it all nipped down just as a gauge for a rough Idea for starters......

[dickie]

If you only want a rough idea, it's easy enough to calculate from stroke, rod length and piston crown height. I've assumed you haven't machined either end of the barrel.

[Lord-Spanner]

If you only want a rough idea, it's easy enough to calculate from stroke, rod length and piston crown height. I've assumed you haven't machined either end of the barrel.

I guess it would be to be fair, the only possible difference is the SIL 150 case, so possibly the base face might have a variation in height from the original Li150 case, back to your question though, no nothing has been machined off the base or top of the block