Technical 704cc 'HOT' Engine Build

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Technical 704cc 'HOT' Engine Build

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Greetings All, I'm raising this thread to document the build of a 704cc engine. The parts have come from a variety of sources, but suffice to say it's a collection, and instead of having a pile of spare parts laying around I'm gathering everything into what I hope will be a hybrid of 500 and 126 engines (y)(y)
I'll start with the assembly of a 'short engine' that is assembled purely for the purpose of balancing and then I'll run through the different areas and what I have done to modify things.
I have a late 80's 126 crankcase that has needed a lot of cleaning prior to starting assembly and as I'm a little manic about cleanliness the need for everything to be spotless will be noticed. The reader will have noticed that the capacity of the engine will be 704cc this is using an 80mm bore (VW sourced barrels) and stroke of 70mm from the 126 BIS. I have also used a BIS crankshaft that has needed some work to make it acceptable, both the main bearings (+0.4mm) and big end bearings (+0.01mm) needed regrinding and to clean the crank properly the core plugs were removed and the difficult job of removing a great deal of muck from the inside gallery began. Because the gallery is not straight black muck builds up in the corners so my engineer used small stiff brushes to get into the corners. The crank was then washed out. I will add that this crank was removed from a serviceable engine :eek::eek: and as it was largely an unknown needed careful preparation. The core plugs were replaced and spot welded to prevent them from blowing out (y)(y)
I'm using copper/bronze bearings (hi quality) from a performance application because they can withstand greater heat, stress and lower oil pressure for longer, but the downside is the price :mad::mad: It's a simple job to assemble everything once the engineering work is complete. The flywheel is now 4.56kg and the clutch pressure plate is part of an uprated unit. The rest of the rear of the engine goes together as standard, but I think the crankshaft backlash will need checking after balancing as it seems a little tight
(n)(n) The bearing journals have been lubricated with Graphogen which is a very good engine build paste.
The remainder of the balancing build-up is to have the pistons running in the bores without rings, The max speeding rods are fitted with ARP 2000 bolts, but these will be replaced as the past fitment is unknown and any stretch will be unknown also. The barrels will be clamped down and an original sump fitted so that the assembly can be dynamically balanced by spinning it all at 270rpm on a balance table that detects out of balance forces, as the force is linear it will all be the same at 10,000rpm :eek::eek: but I have no intention of going that far even if the bolts can take 220,000psi tensile loading. I'm not sure how long the balance will take, but I'll get back with the result and progress when I can. (y)(y)
Ian.
 

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Hi Ian , that all looks and sounds very impressive. Is this going to be the next generation of tuned engine for your car? I guess that you have been planning this for a while. If this is a 'HOT' engine then I have been planning a slightly 'WARM' and far more modest engine project for a while as a winter project to make use of some of the parts I have here. I am starting with a clean bare 499cc crankcase to which I am going to fit one of the already reground crankshafts I have and new bearings of course. I have assembled the new 540cc high compression pistons and barrels I have with 126 con rods to get the double oil squirt onto each bore. They will fit along with a late 126 camshaft and new timing chain kit. Will also use a 126 timing chain cover to get the benefit of the larger oil pump and a Nanni alloy sump. Yet to make a final decision on the cylinder head but thinking of using the Weber 26IMB5 carb I have which is the same spec as the original 500 Sport carb. Just doing it for fun really and to bring together some interesting parts :)
 
Hi Dave, Yes I suppose it is a step up, but like you I have managed to collect all the pieces of another engine and instead of having some spares I'll assemble them all together.
I don't want a race engine just a good useable road item. It will have a better cam and carb, and I will probably 'borrow' the alloy fan from my present engine. The big sump and oil filter + cooler system and exhaust will also swap over. I am concentrating on getting the bottom end as good as I can afford (balancing) as I feel that most if not all of the aftermarket kits for these engine only focus on the top end at the expense of the rest.
Ian.
 
Well here it is all ready to ship off to the balancing man, I've only to find some wood bits and pieces and test my carpentry skills to crate it all up :eek::eek::eek:

Ian.
 

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Very interesting Ian---I am following your progress with great interest. Who is doing your balancing for you. As I have advised you, Oselli, despite rumours to the contrary, are still able to balance the 500/126 cranks, something they have a lot of experience doing,so it would be interesting (if it all goes well) to have another 'arrow in the quiver' with regard to crank balancing.
 
Very interesting Ian---I am following your progress with great interest. Who is doing your balancing for you. As I have advised you, Oselli, despite rumours to the contrary, are still able to balance the 500/126 cranks, something they have a lot of experience doing,so it would be interesting (if it all goes well) to have another 'arrow in the quiver' with regard to crank balancing.

Hi Tom, I'm going to go with Steve at Vibration Free, It seems to me that the 'Dynamic' balance method is more accurate with these Type 2 crankshafts, than only having the crankshaft assembly and working out the balance factor. I will see how it all goes and report back - hopefully with good news (y)(y)(y)
Ian.
 
Hi Tom, I'm going to go with Steve at Vibration Free, It seems to me that the 'Dynamic' balance method is more accurate with these Type 2 crankshafts, than only having the crankshaft assembly and working out the balance factor. I will see how it all goes and report back - hopefully with good news (y)(y)(y)
Ian.
I wonder what adjustments will be needed given the BIS crank was designed to be used with pistons moving in a horizontal plane?
 
The VW barrels...
I presume the bolt pattern is different. Did you need to modify the crank case to fit them?


I had asked about the larger barrels available from 500sport and understood that due to the larger diameter skirt that fits into the crank case needs to be modified to suit this, I presume this is also the case with VW ones, although I have never seen a set in person.


I had not considered how much difference a thorough cleaning would make. I will have to add this to the list once my engine mods begin.


I have been looking into knife edging the crankshaft
https://i160.photobucket.com/albums/t180/christomalan/boxedcrank.jpg


The centre of mass of the bis crank is closer to the axis which helps it spin faster. Also the profile is less blunt which allows the crank to punch through the oil in the sump a bit easier.
Knife edging allows the crank to cut through the oil to a certain degree. This can be carried out on an aircooled crank.


The trade off as always is less mass = less torque


I will be reading this thread with continued interest!
 
I wonder what adjustments will be needed given the BIS crank was designed to be used with pistons moving in a horizontal plane?

As to why the Giardiniera and Bis engines create such an out of balence force just because the cylinder plane is moved from vertical to horizontal is totally beyond me but with both of those engines the balence is maintained by the loading on the flywheel and crankshaft pulley. The Bis crankshaft itself is balenced and is seen as a good upgrade without spending a 4 figure sum :)
 
When I was at 'Radbourne Racing' we fitted "Nardi" 650cc kits to the 500s. If my memory serves me right, the barrels supplied were VW based---I seem to remember them still having a VW part number cast into them. The crankcases were stripped to 'bare' and then sent away to have the barrel aperture increased. We did it this way so that the original engine number stayed with the car. The old VW 1300 and 1600 barrels are, as far as I can see, of the same external dimensions--the 1300 has thick barrel walls which are bored out to give a 1600 capacity (an extra 75cc per cylinder).
As to the cleanliness of the crank-case, I get all my aluminium parts "aqua-blasted" (aka, vapour blasting). The beauty of this process is that as the abrasive medium is carried in high-pressure water, it leaves no 'pock-marks' on the gasket surfaces, which makes for much easier preparation. "Aqua-blasting" is also a good way to get complicated-shape non-ally parts de-painted ready for re-painting (fan and heater shrouding being such examples).
 
As to why the Giardiniera and Bis engines create such an out of balence force just because the cylinder plane is moved from vertical to horizontal is totally beyond me but with both of those engines the balence is maintained by the loading on the flywheel and crankshaft pulley. The Bis crankshaft itself is balenced and is seen as a good upgrade without spending a 4 figure sum :)

I'm guessing that the problem with a horizontal stroke is that gravity is not aligned with the piston movement in the way it is with the vertical design and perhaps that puts in an extra wobble?

...short memory on me...I see we've discussed this before. ;)

https://www.fiatforum.com/500-class...tal-question-balance.html?417971=#post4015095
 
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So what do you guys think is the right timing advance at idle and at 3K rpm for this engine? I have a similar 700cc build and am trying to work it out (but still trying to get the carb jetted properly first).

I have a full 123 ignition and electronic coil setup if that will help. I have posted previously, but didn't get any insight from others other than to use the values for the 126 BIS engine (but I can't find those values).

Thanks, and happy holidays!!:worship:
 
Evening Dax;
There are so many things that can affect what timing is required, including altitude and what fuel is in the car (I use 98 octaine in my engine) that all I can give you is the (652cc) 126 basic timing, which is:--10deg at idle (700rpm) + 14deg at 3,000rpm + 21deg at 3850rpm--all BTDC. I am still to fit my '123' system, so I would also be interested in which setting people who HAVE fitted (and using) the '123' system are on.
 
Greetings All, apologies for the lack of progress of late, but I have been enjoying some festive cheer with the Irish side of the family!!!!! (y)
I'll continue with the cylinder head and modifications thereto, but please All note that this involves a PANDA 30 head only.
The head has been previously skimmed to a capacity of 34.2cc and a repair has been carried out to both cylinder areas between the valves, one being cracked (known problem) and the other not. I have been advised that the repair does add strength to this area. The valves have remained standard at 34mm IN and 28mm EX. The valves could have been enlarged, but this would have increased the cost and cause more stress to the area between them. The theoretical ideal valve size can be arrived at providing you know the stroke x bore and rpm limit thus -
@ 6000rpm Inlet 34.29 Exhaust 29.15mm
@ 6500rpm Inlet 35.69 Exhaust 30.34mm
Both of the Inlet and Exhaust tracts have been extensively ported and polished. The valve springs have been replaced with a new standard set, again hi performance springs can be obtained but are expensive (n)(n)
One area that did concern me was the wear and tear the plug threads have suffered, so, on advice I had solid inserts put in - these are not helicoil or memfast, they are a solid strong non alloy insert. I didn't want a plug blowing out at High compression/rpm !!!!:eek::eek:
Panda heads have two step pushrod tubes with a fixed tube in the head and a short flexible tube from the head into the crankcase. I have found that the oil seals for the top tube go hard and permit oil past them, so no matter how good a seal you achieve at the bottom the oil loss at the top can be massive :mad::mad::mad: the oil seals would be next to impossible to replace as they are set into the head casting. So, knowing this I elected to use VW pushrod tubes that can be inserted when the head is in place and adjusted up tight, the oil seals provided are a much better item being more robust and larger. To allow the use of these tubes the original fixed tubes in the head need to be removed which can be a difficult job, then the lower tube holes need to be enlarged to allow the VW item fitment. The one fly in the ointment is that the centre tube for the oil delivery pipe has a different mounting that is part of the head casting (see pic) so one of your pushrod tube needs to be cut by the same amount as the casting to fit the same length as the other four. I am undecided regarding the fitment of a head gasket, it will depend on the results gained from careful measurement of the stroke and deck height, I am looking for a C/R of 10.6:1 maximum and keeping the squish area to the ideal 1mm may or may not involve a gasket. I would think that a lower spacer of 85.5mm fitted at the cylinder spigot will be required to adjust the deck height and it will add strength too. I'll continue with rocker ratio's and camshaft lift / pushrod length and adjustment. Also I'll cover the issue of the top valve cap underside contacting the top of the valve guide during operation in my next update. (y)(y)

Ian.
 

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OK, rocker ratio's and camshaft lift / pushrod length and adjustment. The engine rocker ratio is 1.5 so for my first engine using a 35/75-75/35 Cam with a published cam lift of 7.25mm x 1.5 = 10.875mm AT THE VALVE. But, with the standard valve guides being fitted both of the exhaust valve spring retaining cap underside distances were measured and found 1mm too close !!! :eek::eek: so the valve guide top was adjusted to give sufficient clearance during operation. the inlet distances were ok. The pic shows the adjusted pushrod length, bearing in mind that the head has been skimmed and that the rocker arm should be horizontal at half of max cam lift to give the best results otherwise you loose some of the effective valve opening time :mad::mad:
As I am using a 40/80-80/40 cam this time (7.70 x 1.5 = 11.55 lift) we shall have to measure again what the clearances are and cut pushrods and possibly valve guides to suit !!! I shall probably use two nuts on the 7mm valve adjusters to lock them tight.

Ian.
 

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That's really interesting techy stuff Ian....I like detail. [emoji3] I wouldn't bother with doubling the locknuts on the adjusters. You'll be adding more weight to a rapidly moving part and maybe upsetting a delicate balance. But more importantly you won't achieve anything in terms of security because unlike when you tighten a nut against a stud or other fixed , threaded item, which is independently secured when the nut can benefit from a second locknut, the tappet screw is a loose fit in the rocker-arm and works reciprocally with the locknut to achieve friction. Effectively this is already like the action of two nuts tightened against each other.
 
That's really interesting techy stuff Ian....I like detail. [emoji3] I wouldn't bother with doubling the locknuts on the adjusters. You'll be adding more weight to a rapidly moving part and maybe upsetting a delicate balance. But more importantly you won't achieve anything in terms of security because unlike when you tighten a nut against a stud or other fixed , threaded item, which is independently secured when the nut can benefit from a second locknut, the tappet screw is a loose fit in the rocker-arm and works reciprocally with the locknut to achieve friction. Effectively this is already like the action of two nuts tightened against each other.

Hi Peter, Yes, it's all in the techy detail - I like your explanation of the rocker action so I shall dispense with the extra nut on the adjuster (anything to save money!) I must say that I am enjoying discussing engine detailing with my engineer chap (old school) It's truly amazing how much detail a professional engine builder will go to based upon the proposed use of the unit! :worship::worship::worship:

Ian.
 
Right, pistons, conrods, cylinder barrels and bolts.
Having acquired the parts of a previously running engine it's very easy to assume that the same engine just needs a quick rebuild and Bob's your uncle!! (n)(n)
If you are willing to spend time and a little money with the gamble that it will stay together for more than a few minutes after the first turn of the key you are welcome to try, But don't be upset :cry: if it all ends in tears (been there, done that) bitter experience has taught me that the more time and money you invest the more likely you are to end up with a jewel of a motor purring away behind you:(y)(y)
When the cylinder barrels arrived they still retained the obvious top lip, this has to be removed to allow a good cylinder to head seal with or without a gasket. (see before and after pics) also the cylinders had not been properly honed so that needed to be done too. We arrived at a final piston to bore clearance of 1.4mm which is about the maximum you can goto before you need to consider a rebore. It needs to be said that pistons of 80.5mm are available from Italy (CPS) but are very expensive :eek::eek:
Standard 126 BIS pistons (80.0mm) are freely available with ring sets too, They have the standard three ring pattern and have a compression height of some 33mm. I do not intend to go wild with massive changes of compression height as you only move the corresponding deck height question elsewhere. Unless there is a need to use shorter compression height pistons (light weight and a racing application) you will find that the cylinders will need reskimming too.
There will be a need to adjust the piston ring size as well, essentially the rings can be clipped to lower the contact (or Grip) they have on the barrel wall depending on future use and any heat expansion expected. The ring ends (at the gap) can be rounded off too to reduce any possible scratching of the cylinder wall.
As mentioned before the conrods are 'Maxspeedingrods' (130mm stroke) with ARP 2000 bolts, due to the unknown application prior to purchase I had the rods checked for true at both the big and little ends. Again, I am using bearings from a performance application. The ARP bolts are to be replaced too as the total stretch is unknown and I don't want the rods exiting through the crankcase :mad::mad::mad: It took me some time to find the correct torque and stretch figures to apply to the new bolts, but persistence paid off. Using 5/16" ARP 2000 bolts I will apply the final torque (it has to be applied in stages) of 32 ft/lbs with a recommended bolt stretch of between
.0055" to .0060" .(you need a special gauge for this)
Mr Ebay kindly allowed me to find replacement bolts with the special lube too. Thats all for now. (y)(y)

Ian.
 

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Greetings, I've just found what may turn out to be my Christmas present to me ! :cool:
I was intending to use a new fiat timing set Crank - Cam sprocket and chain, But D'Angelo Motori have a nice gear set for the same (y)(y) The only problem is the cost (n)(n) Has anyone on here any knowledge of this type of gear set and how good it is ????????(n)

Ian.
 

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