Tuning 695 Engine Project

[Bambino]

I secured them for peace of mind and also if I ever sell the car it can be returned to its original state more easily if no wires are cut and wound together.
Chris

 

[RogerNZ]

Hi Chris, I recall you used the same conrods in your engine as the ones I have bought for mine (130mm H bean style sourced from 500Ricambi) as per pic attached. I just wondered if they had provided any torque settings for them. Mine came with no info and as they are radically different from the standard rod it occurred to me that I might benefit from your experience on this one (again!).

Cheers Roger

 

[Bambino]

Hi Roger,

Yep - that's them - 130mm rods from 500 Ricambi in Holland.

I didn't get any information either and didn't get a reply when I asked. I approached the tuning guys up here (Barnes High Performance) with both the old and new rods. They looked at the bolts and then advised me to use the same torque settings. On what basis they gave that advice I'm unsure. I guess they thought that the bolts had the same elastic characteristics.

So I torqued them to 24 ftlb. Haven't heard a bang yet and oil pressure is OK so maybe all is well.

Chris

 

[RogerNZ]

Hi Chris, I am now in the process of putting my engine together. If you recall our conversation earlier in this thread about gaskets and piston height you may be intersted to know that when assembled without a base gasket my pistons crown above the cylinder height by about 2.0mm. I recall yours were below cylinder height by around 0.2mm. I got a few steel base gaskets with the kit, but nothing suitible for the height I am after, so I'm now getting a 2.5mm gasket made up. Strange that two kits "the same" appear so different. I wonder if the difference is in the piston height or perhaps possibly a small difference in the engine case?

Cheers Roger

 

[Bambino]

That's disappointing. Maybe the crankcase is at fault ... I've forgotten - are you using a 650 or 500 crankcase ?

When I ordered my parts, all I asked was that the cylinder heights were as close to their specified height as possible and that they were matched.

Prior to assembly I took the parts to Barnes High Performance (http://www.barnesperformance.com.au/newsite/) who are in my local area and had them check the tolerances etc. They do a lot of engine tuning for racing, including motor bike preparation, and have more equipment and knowledge than I can ever hope to amass in one lifetime. They were happy about the parts and so I proceeded to assemble the engine, measuring and photographing as I went along.

I've no doubt that you are a very competent restorer - the photos are sufficient evidence - and it's upsetting to see problems like this crop up when they don't have to. The spacers will act like thick gaskets and won't compromise the rebuild - it's just a hassle to have to get them made.

What did you decide about the end cap bolt torque setting ?

Chris

 

[RogerNZ]

Yup, that's it Chris, it's just one of those things that pop up during a build. When you start mixing and matching parts for a bespoke build you've got to expect it. That's why we did a quick test build and fitted the pistons without rings - an easy check that quickly shows up and problems. I'm using 650 cases. My guess is that the height difference between our two kits is in the piston. Since we were only looking to test piston height I have not yet torqued the rods. I sent an email to the supplier just as you did and got the same result - no reply. I am going to try and get some info from the manufacturer, but am not hopeful! In the end I think I'll go with the standard torque settings just as you did.
Cheers Roger

 

[jjacob]

This is a good time to discuss compression. I have been looking into various piston sets. On various supplier sites I see three different piston types for any bore. So for let's say for a 79.5mm bore they list three different compressions. 25, 38, and 40. 25 is listed as low compression and 40 as standard.
This may be the difference between Roger and Chris' pistons. I may have this wrong also as it is possible that each of these pistions takes a different connecting rod length.
Maybe someone with knowledge in piston compression types can weigh in.
As for me, when I build my engine I want to target a compression ratio of something like 8.8 - 9.0 to 1.
John

 

[babbo_umbro]

This is a good time to discuss compression. I have been looking into various piston sets. On various supplier sites I see three different piston types for any bore. So for let's say for a 79.5mm bore they list three different compressions. 25, 38, and 40. 25 is listed as low compression and 40 as standard.
This may be the difference between Roger and Chris' pistons. I may have this wrong also as it is possible that each of these pistions takes a different connecting rod length.
Maybe someone with knowledge in piston compression types can weigh in.
As for me, when I build my engine I want to target a compression ratio of something like 8.8 - 9.0 to 1.
John

What do 25, 38 and 40 signify? You're looking for a combustion chamber volume of 43.5 to 44 cc; assuming a flat-topped piston that rises flush with the top of the cylinder barrel your head gasket gives you 5 cc of chamber for every mill of thickness, then your actual chamber is on top of that. I doubt that the con rods vary in length, especially as these engines give you the option of spacers under the cylinder barrels.

 

[Boodajuda]

This is a brilliant project

 

[jjacob]

What do 25, 38 and 40 signify? You're looking for a combustion chamber volume of 43.5 to 44 cc; assuming a flat-topped piston that rises flush with the top of the cylinder barrel your head gasket gives you 5 cc of chamber for every mill of thickness, then your actual chamber is on top of that. I doubt that the con rods vary in length, especially as these engines give you the option of spacers under the cylinder barrels.

The 25, 38 and 40 I believe refer to the compression height. I am just not sure what is being measured. See the pics below.
There are different length connecting rods available due to the fact that the piston pin location is in a different spot on some larger diameter bore pistons.
I will try to do a little more internet research and see if anyone knows the piston compression numbers that are listed. I may try to send an email to one of the suppliers. Thought someone here might know.
John

 

[Bambino]

To the best of my knowledge and with reference to the attached image, I think this is what is happening -

The conrod length in both the 500 and 650 is 118mm and the piston heights are also the same at 40mm giving a combined height of 158mm. If you add this to one half of the stroke (35mm) you get a grand total of 188mm which when you add the deck clearance (2mm) gives the deck height of 190mm. The deck height is made up of the crankcase height (100mm in the 500 and 110mm in the 650) plus the cylinder height (90mm in the 500 and 80mm in the 650).

When I rebuilt my engine I mated 30mm pistons with 130mm conrods giving a height of 160mm which left me with a deck clearance of ~0.20mm.

Compression ratio is determined by a combination of deck clearance, head gasket thickness, piston crown shape and of course cylinder head shape and volume. Because I used standard flat topped pistons and didn't want to shave the head, the only way I could increase my CR was to decrease the deck clearance and use a thin gasket (copper).

I probably should have explained a little better what I did at the time, but I was so chuffed at actually getting a response from the sellers in Europe and having the stuff arrive intact, that I got a bit carried away and proceeded to assembly after all of it was checked by a local engine rebuilder. I should have taken more photos, but didn't - maybe next time

I thought about all of this the other night after Roger had problems with his rebuild and unless he has bought 32mm pistons with 130mm conrods thus leaving him a 2mm excess above the deck, I have no other explanation. Once he fits 2mm spacers, all will be well. Maybe I just got lucky.

In the end I think my CR up from the standard 7.5:1 to around 8.5:1 though I have no real way of measuring it at present other than doing some basic maths on the other standard engines.

Chris

 

[babbo_umbro]

I assumed these numbers might be compression height but the large discrepancy can only be achieved through different-length con rods, which I (mistakenly) assumed was unlikely. Longer con-rod has the advantage of lower side thrust and friction on piston, lighter piston probably more than cancelled out by heavier con rod, I'd just make sure that its reduced angularity doesn't put it too close to the bottom of the cylinder barrel.

 

[RogerNZ]

Hi Chris, I agree with the basics of your calculation, but the math is a little out. 118mm rods, plus 40mm pistons, plus 35mm of stroke equals 193mm, not 188. No biggie of course, but I was scratching my head reading your post over and over thinking "there's something not right"!

While I waited for my 2.5mm barrel gasket to be made I measured my rods and pistons. They are the same as yours, so the only thing that can be different is the crankcase height, ie mine must be about 2mm lower than yours. The exact height is not easy to measure on a half built up engine so I haven't bothered, but it is interesting. I gave away my old barrels so have not been able to check for them for marks which would show how far up the pistons came on the original rods and barrels.

I had a bit of extra fun and games with the engine once the base gasket arrived, I'll post an update on my thread later this week with some extra details.

Meanwhile I have solved the conrod torque setting question. I emailed the supplier and like you got no reply. But then I googled the code ARP 2000 that was on the bolts and it turns out ARP are massive global suppliers of conrod bolts. The ARP 2000 bolts are tempered to a strength of between 200,000 and 220,000 psi. You can see more on this at http://arp-bolts.com/pages/technical_metallurgy.shtml

I then checked their torque spec sheet at http://arp-bolts.com/pages/technical_torque_us.shtml and it seems the torque should be between 28 and 32. I'll be using 28 when I torque the bolts tomorrow - note that value includes using a proper lube.

Cheers Roger

 

[Bambino]

Sorry all - 193mm is right. Don't know how I got 188mm ?? I blame my Grade 3 teacher for making me use those useless cuisenaire blocks

Lucky I didn't need to add up much to rebuild the engine. Looks like I'll have to remove the sump and torque my con rods big ends a bit more as well. Funny that the crankcases should be out by that much when the rest of these engines are built to quite close tolerance.

Thanks for pointing out the errors and corrections Roger. As one of your previous PMs once commented about the net migration of Kiwis to Oz - 'at least it's raised the IQ of both countries'

Chris

 

[RogerNZ]

Hi Chris, a very small point, but I wondered what your experience may have been with different spark plug heat ranges for your tune? I am dreaming of the day when I get to test such things myself....

Cheers Roger

 

[Bambino]

Roger,

I started with NGK BP6HS plugs but they seemed too cold so I replaced them with 5HSs and have had no trouble. The engine cold and hot starts easily, idles well and doesn't foul the plugs.

I must admit that I asked around a bit and got a lot of confusing information, so I went with a reliable general purpose plug in the first instance.

What have you heard and what will you use?? I'd be interested in your opinion.

Chris

 

[RogerNZ]

Thanks Chris, I planned to start with a 6 like you and take it from there. I'll let you know how I get on.
Cheers Roger

 

[Timothy500]

Him
Wow you did a great job,, I like one day soon to start with mine,, but you might help me how could I know that my engine is 500 cc,,, or 595 cc,, because on my log book of my 1967fiat it says 594 ,, is there any way that I could find out which engine I have without take the cylinder head out
If some could help that would be great like always
By the wat did you reinforce the block to put 650 cylinders when you took it to the engineering
Well thanks for now

 

[jcang0408]

The engine block should be stamped on top of the cylinder head (between carb inlet and rear of engine) with the displacement in CC.

Him
Wow you did a great job,, I like one day soon to start with mine,, but you might help me how could I know that my engine is 500 cc,,, or 595 cc,, because on my log book of my 1967fiat it says 594 ,, is there any way that I could find out which engine I have without take the cylinder head out
If some could help that would be great like always
By the wat did you reinforce the block to put 650 cylinders when you took it to the engineering
Well thanks for now

 

[Napalm Dog]

A word of caution - I had a 500F starter motor that sheared the lugs off its mounting on the bellhousing as a result of metal fatigue in the aluminium - they beefed it up on later ones, I think - doing astronomical revs does set up massive off-balance vibrations in this type of twin. In the end I threw the Fiat engine away and mounted a 700cc flat twin BMW engine - an absolute gem of an engine, full of ball and roller bearings, which produced something like 40 horsepower and would cheerfully do 7000 rpm all day. At the time, the Mini Cooper was king of the small cars and my 500/BMW would eat them for breakfast.

Buona fortuna con il progetto. (Off to our Italian home for two months tomorrow, so keeping my hand in.)

Hey, have you had any transmission issues running what I assume to be an R70 engine?