Technical Foreign Object Damage

[Bounding Bambino]

I can't find any Wellseal in Nova Scotia, so I wrote to Nanni Ricambi to ask what sealant they recommend, and guess what, Nanni wrote that "nothing is required between the head and the cylinders!" I'm not sure I believe that. I also wrote to Permatex to ask them which of their products they recommend for this purpose, and they wrote back that none of their products are designed to be used without a gasket. Hmmm.
I measured the "lip" thickness at 7mm. That gives a mating surface area of about 44mm^2. That doesn't seem like much to me. Even with a sealant.

Im comparing chemical data sheets between both. Both seem to be near identical products, but im still researching...

Permatex looks like they forgot about their one product then. https://www.permatex.com/products/g...tion-form-a-gasket-no-3-sealant-liquid-16-oz/

Both That permatex and wellseal seem to be very similar compositions. Atleast you can try the permatex "locally avalable/cnd tire sells it" and if it fails, then seek out wellseal. They also have the same "rated" temperature range also in their TDS, flash points, colour, and both alcohol based solvents. Ill take a risk and say they are likey very near identical products.

im actually going to pick up a bottle of the permatex next time im at the store. I personally never have seen a engine without any sort of physical "head gasket", but not dismissing the ideal of it. I will definetly try it out on these engines and see what the outcome is.

 

[bugsymike]

I measured the "lip" thickness at 7mm. That gives a mating surface area of about 44mm^2. That doesn't seem like much to me. Even with a sealant.

The other thing to take into account is that the smaller the contact area the higher the sealing pressure when torqued down, much the same with lapping in valves (where a good thin line of contact is much better than a wide band) so as long as the two mating surfaces are even and flat it should be fine.
It is not as though you have to worry about coolant/antifreeze creeping properties.

 

[fiat500]

You could fit a thin, cylinder-head gasket despite the supplier saying it's not needed.

 

[Bounding Bambino]

You could fit a thin, cylinder-head gasket despite the supplier saying it's not needed.

I would second this. If you could source a thin copper gasket, it would be a decent compromise imo. You can even make copper head gaskets from flat stock if your feeling handy.

As a side note, i did pickup a bottle of the permatex version of the sealer today. It definitely has a unique smell, that seems to be a common consensus from others online who have use Wellseal. I might give it a try on one of my engines.

Anyways you have options. But my concern is. if for any reason you have a slight "height difference" between the cylinders when mounted in the case, you will not get much life out of the liquid gasket for it to be effective, the cylinder faces need to be absolutely parallel. Which is easily obtainable if the case had a light skim machining done "ie during a performance build or such" but obviously in your application, your just doing a cylinder swap, on a stock aged case. Regardless your mileage might vary.

 

[bugsymike]

Anyways you have options. But my concern is. if for any reason you have a slight "height difference" between the cylinders when mounted in the case, you will not get much life out of the liquid gasket for it to be effective, the cylinder faces need to be absolutely parallel. Which is easily obtainable if the case had a light skim machining done "ie during a performance build or such" but obviously in your application, your just doing a cylinder swap, on a stock aged case. Regardless your mileage might vary.

Excellent suggestion for matching everything.
Only thought, if more than a very light skim it may bring piston to head/valves too close , so worth checking tolerances there as no gasket to help.
On many diesels in the past I have fitted head gaskets with a series of notches which indicated thicker gasket after head skim etc. The thicker the gasket the more notches.

 

[ronstox]

Responding to Hobbler's & Bounding Bambino's suggestion that I assemble a cylinder in order to measure where the pistons come up to on TDC, I enclose a couple of pictures of my new pistons. I note that they are "stepped" so I wonder if they are meant to project above the top of the cylinder at TDC? If so, how far can they safely go before interfering with the valves?

 

[smart51]

The step is meant to be above the top of the cylinder at TDC. It is there to reduce volume of the combustion chamber and increase the compression ratio. The valves open to by the part that isn't stepped.

 

[Bounding Bambino]

The surface with the piston info/writing is technically the piston face where you would measure the "squish" from. Piston surface to cylinder top.

The stepped feature is more of a "performance improvement" design feature of the piston. Its intent is to help increase compression ratio for stock heads. Theoretically during a engine blueprint, you measure the offsets and valve stroke and figure out valve to piston clearances. But for your application, there should be enough room in factory form with factory rockers and standard camshaft.

Things start to get interesting when your running a high lift cam, high lift rockers, and oversized valves with a higher compression ratio head. But in your case you shouldn't have an issue at all. You'll find out if things hit when you start turning the engine over by hand when your setting timing.

A quick dirty easy way to gauge piston to valve clearance is temporarily assemble the head and camshaft and have the entire rotating assembly synced up with proper valve rocker clearance. but before you put the head on, put some modeling clay on the piston top. Manually turn the engine over a few times, and you will see the valve indent on the clay, and you can slice it and measure and approximate clearance.

 

[Bleeding Knuckles]

Hi Ron, I note in the pic of your head that quite a lot of material has been removed, because of this fact I would council that you remove the lip from the top of the cylinders to give you the maximum surface area for contact between head and cylinders. If you are not going to use a gasket be sure to measure the capacity of the head for the C/R calculations. You can fit spacer/support plates under the spigot area to adjust the deck height, they are available in different thickness and add strength to the crankcase. It will probably be difficult to arrive at the perfect squish measurement and C/R by adjusting the deck height as it its dependant on the amount of material removed from the head in the first place. In the assembly of my 'Hot' engine to arrive at a C/R of 10.5:1 we had to use different spacers with a 0.5mm copper gasket AND then remove a small amount of material from the piston top. All this was due to an unknown amount being removed from the head prior to my ownership. I have larger valves, a 40/80-80/40 cam and roller rockers running at 1.55 ratio and still don't have any piston/valve contact problems the squish gap measurement is not perfect, but it is as close as we can get it.
If you need any more info pm me.
Ian.

 

[ronstox]

Bounding Bambino: I asked Permatex about their Aviation Form-A-Gasket product in lieu of a head gasket. This is their reply:
"Aviation Form-A-Gasket would definitely not work as a head sealant in place of a head gasket. The pressure and heat will burn the sealant right out."

 

[bugsymike]

Would lapping the two surfaces together to make a perfect match as I mentioned we used to do on racing Villers engined Karts back in 1970 work?
We used fine grinding paste on plate glass to give a perfect seal. The only problem I can see is two individual barrels and one double cylinder head getting them to match heights, as ours were single cylinder engines.
Pro Seal Grey made in USA is good for 650 degrees Fahrenheit. K2 Black is good for 350Degrees Centigrade, Heldite Jointing Compound is another good for 350 Degrees Centigrade.
What temp. do you anticipate at head area?

 

[ronstox]

I've not done much on the engine in the last little while, but I'm now over the hump of all the other things on my plate, so I'm back at it again. Yea!
Here's some photos of my pistons. #2 looks like where it all started. The top ring was half gone, and it looks like it chewed up some of the piston on the way out. The middle ring was all there but broken. Oddly enough, I didn't see any damage to the cylinder walls. #1 has some damage too, but the engine did before it could get to bad. All is rings were whole, but the top one was pinched by the head of the piston.

 

[bugsymike]

I've not done much on the engine in the last little while, but I'm now over the hump of all the other things on my plate, so I'm back at it again. Yea!
Here's some photos of my pistons. #2 looks like where it all started. The top ring was half gone, and it looks like it chewed up some of the piston on the way out. The middle ring was all there but broken. Oddly enough, I didn't see any damage to the cylinder walls. #1 has some damage too, but the engine did before it could get to bad. All is rings were whole, but the top one was pinched by the head of the piston.

Is that "pinking/pre ignition" damage on top of piston, or my bad eyesight?
Is it nearest the spark plug position?

 

[ronstox]

I think that there was likely some pre-ignition going on, especially with all that carbon on the piston head, but that damage you see occurred in the "squish" area and appears to be bits of piston ring bouncing around in there. I even found a small piece of ring embedded in the piston head.

 

[ronstox]

My bad, I checked #2 cylinder more closely this time, and yes there is damage.

 

[ronstox]

I measured the head chamber, as Bounding Bambino suggested, at 41cc.
The stepped piston head I measured at -13cc.
Assuming zero deck clearance (reasonable, see below) and no gasket (as Nanni Ricambi says), that gives me a compression ratio of 10.7:1,
If I add a 1mm Copper head gasket, I'll get 9.5:1, which I think is what I think I should be aiming for.
I've been inquiring at a machine shop in Dartmouth, NS that can laser cut a 1mm copper ring gasket that will fit on top of my cylinder lip (I.D. 70mm, O.D. 71.4mm, thickness 1mm).
If I apply some gasket goo (Thanks to The Hobbler for a tube of Wellseal) to that, I think it would work. What do you think?

I haven't assembled the piston/arm/crankshaft/cylinder yet, but the 540 cylinder is 90mm high, same as the 499, so I'm confident the deck clearance is zero.
BTW, Does anyone know the head chamber and piston dome volumes for a bog-standard 499cc?

 

[the hobbler]

I measured the head chamber, as Bounding Bambino suggested, at 41cc.
The stepped piston head I measured at -13cc.
Assuming zero deck clearance (reasonable, see below) and no gasket (as Nanni Ricambi says), that gives me a compression ratio of 10.7:1,
If I add a 1mm Copper head gasket, I'll get 9.5:1, which I think is what I think I should be aiming for.
I've been inquiring at a machine shop in Dartmouth, NS that can laser cut a 1mm copper ring gasket that will fit on top of my cylinder lip (I.D. 70mm, O.D. 71.4mm, thickness 1mm).
If I apply some gasket goo (Thanks to The Hobbler for a tube of Wellseal) to that, I think it would work. What do you think?

I haven't assembled the piston/arm/crankshaft/cylinder yet, but the 540 cylinder is 90mm high, same as the 499, so I'm confident the deck clearance is zero.
BTW, Does anyone know the head chamber and piston dome volumes for a bog-standard 499cc?

Hi Ron;
The standard 500/126 pistons are all' flat-top' so there is very little, if any, 'dome' volume. If they don't cost too much, how about getting the machine shop to cut you both a 1mm and a 0.5mm head gasket and see what difference in make in the c/r? I normally use a copper head-gasket, for which one doesn't normally need any 'goo'. I would suggest that you do try to keep the c/r to UNDER 10:1 for a "road-use-only" car, where reliability is of a much greater importance than the last ounce of bhp. I am about to go out to my workshop---i will have a look and see if the cylinder-head that I was given is a 500 unit. If it is, i will try and measure the combustion-chamber volume for you.

 

[bugsymike]

It wasn't a problem when 5* Star petrol was available, but unless you run on aviation fuel higher compressions are a problem.
I rebuilt a Ford "Tickford" 2.8 Turbo Capri many years ago that was burning holes in the pistons and had been rebuilt several times by other garages I obtained a set of Mahle pistons that gave a compression reading of 150psi against the originals of 180psi and the customer was well pleased as he could give it full boost with no pinking etc. and the engine stayed reliable.
Before he was using Octane Boosters and all sorts.
He told me his was one of the last 50 still going out of a 100 made, this was in the late 80s.

 

[the hobbler]

It wasn't a problem when 5* Star petrol was available, but unless you run on aviation fuel higher compressions are a problem.
I rebuilt a Ford "Tickford" 2.8 Turbo Capri many years ago that was burning holes in the pistons and had been rebuilt several times by other garages I obtained a set of Mahle pistons that gave a compression reading of 150psi against the originals of 180psi and the customer was well pleased as he could give it full boost with no pinking etc. and the engine stayed reliable.
Before he was using Octane Boosters and all sorts.
He told me his was one of the last 50 still going out of a 100 made, this was in the late 80s.

Hi Ron;
I have had a look in my workshop (the 'spares' dept) and although I was told that it was a 500 cylinder head (the one that I was given) it is in fact a 126 head. Would you like me to pop a couple of valves into the '595'head and see what the combustion camber capacty is in that head?

 

[ronstox]

Thanks Tom, but don't go through the trouble. I was only curious. I don't need it for my engine.
BTW, a 0.5mm gasket would me a C/R of 10:1