My Alfa Romeo 33 rebuild - FIRST TIMER

[timinator]

Hi WhizzMan, Helmholtz is interesting stuff. Swartz and Bowling have calculators for determining runner length. Chris's engine looks to have approximately 6in. of intake tract from the bottom of the carb to the intake seat. A runner that short would have a 2nd, 3rd, and 4th harmonic above 11,000 rpm. Not much use for this engine. As far as i know the Helmholtz free energy effect is confined to each individual cylinder. A Helmholtz resonator would only have a value in regard to minimizing the air cleaner box "roar".

Tim

[Brit01]

My error.

Old coil was not ballasted. What looked like a resistor was just a plastic cover connected from ground to postive!

There is rather a long oil debate going on on the Alfa romeo forum about using a 60 viscosity oil with hydraulic tappets!
I found my tappets bled out in summer with 50 oil.
Some seem to think 60 is too thick for the oil channels in the tappets.

Well after 6 months the engine and tappets have never been this quiet with the 60 oil.
When the tappets don't hold their pressure they start making noises.

Proof is in the pudding?

[Brit01]

Coil readings

Old:
Primary:1.55
Sec: 6.55K

New:
Primary:1.5
Sec: 8.91K

The old coil has a significantly lower resistance on the secondary.
A short or low resistance in the coil's secondary windings will result in a weak spark.

[Guy Croft]

Helmholz:

start a new thread if you want.

Keep it off here, Chris has enough to worry about.

No disrespect intended.

GC

[Brit01]

Thanks Guy.

Guy: What is your knowledge around the topic of hydraulic tappets and the effect of oil viscosity? You know I am running 60 viscosity and would like to know if using this thick oil can cause the tappets to pump up too much and cause excessive wear on the lobes over time.

I was under the impression that tappets are self adjusting and only pump up to create a zero clearance between the lobe and valve stem. Whether it's 40, 50, 60 or 70 psi. They cannot over-pressurize.
If the oil becomes too thin or pressure drops then problems can arise due to them bleeding down.

Also if I'm correct the tappet will pump up to create a 'solid tappet' to overcome the force of the valve spring to lift the valve.
If it becomes too high the valves will not close properly resulting in loss of performance and burnt valves. Can this happen do you know?




Regards

Chris

[timinator]

Helmholz:

start a new thread if you want.

Keep it off here, Chris has enough to worry about.

No disrespect intended.

GC

No need for a new thread - the topic is covered all over the internet. Unless one has the ability to fabricate entire intake systems the subject is purely academic.

Chris, oil filled coils last longer if they are not mounted in the vertical position. The oil cools the business end of the coil.

Found a copy of 'The Dellorto Superformance Tech Book' by Bob Tomlinson written in 1989. He uses .55 idle gas jets for 1.6L engines using 36 or 40mm carbs for street type engines.(pg. 110) .52 idle jets for passing emissions tests.

Andy, when you increased valve size or intake runner volume how much did you raise the compression ratio to compensate for the loss of air speed and/or increased overlap? In case Chris wants to follow up his rebuild with performance changes it would help his planning to know the added costs of changing components and machining.

Tim

p.s. GC, no disrespect taken. Always better to stay on point.

[Brit01]

Chris, oil filled coils last longer if they are not mounted in the vertical position. The oil cools the business end of the coil.

Found a copy of 'The Dellorto Superformance Tech Book' by Bob Tomlinson written in 1989. He uses .55 idle gas jets for 1.6L engines using 36 or 40mm carbs for street type engines.(pg. 110) .52 idle jets for passing emissions tests.

My coil is horizontal. Thanks for the tip.
You saw the resistance differences of the secondary?

I will try the 55 idle jets then before looking at the floats.

Regards

Chris

[WhizzMan]

10W60 is basically the same viscosity as 10W40 oil at room temperature. Yes, it's both 10W oil, but with different additives. The 40 or 60 is the equivalent W number at "working temperature" so around 80-100 degrees Celsius. The oil is much thinner at that temperature, so even if 60W is thicker than 40W, it's thinner than the 10W it is at room temperature and the tappets work fine with "cold" oil. How someone thinks that suddenly at working temperature that could be a problem, is a mystery to me.

Tappet wear is caused by low(er) ZDDP contents of modern oils, dirty oil, caused by extended service intervals (also known as lazy or cheap owners/mechanics) and for instance bad air filters that let silicate get in, and eventually worn other parts that make the tappets not fit properly anymore. 10W40 or 10W60 viscosity have very little to no effect on tappet clearance or wear.

[Guy Croft]

Sorry I have little exp on hydraulic lifters so cannot comment substantively on the effect of viscosity.

G

[Brit01]

10W60 is basically the same viscosity as 10W40 oil at room temperature. Yes, it's both 10W oil, but with different additives. The 40 or 60 is the equivalent W number at "working temperature" so around 80-100 degrees Celsius. The oil is much thinner at that temperature, so even if 60W is thicker than 40W, it's thinner than the 10W it is at room temperature and the tappets work fine with "cold" oil. How someone thinks that suddenly at working temperature that could be a problem, is a mystery to me.

Tappet wear is caused by low(er) ZDDP contents of modern oils, dirty oil, caused by extended service intervals (also known as lazy or cheap owners/mechanics) and for instance bad air filters that let silicate get in, and eventually worn other parts that make the tappets not fit properly anymore. 10W40 or 10W60 viscosity have very little to no effect on tappet clearance or wear.

Very valid and accurate fact whizzman. Thanks.

[Brit01]

I have a question regarding oil viscosity, flow rate and pressure.

I'm aware that putting a oil that is too thick in the engine can cause excessive friction as the oil flows through the bearings and create a heat build up and too thin equals too much flow(loss of pressure) and a heat build up also.

Let's take a 60 viscosity oil as an example.
Under normal running conditions and a clearance of 0.055mm on the main bearings.
If my gauge is showing ~50 psi @3000 rpm am I ok running the 60 oil or can I reduce it to 50 oil?
I imagine the pressure would drop maybe 5-10 psi @ 3000 rpm.

Can I simply rely on the psi readings to determine the flow rate at specific rpm?

It's a bit of a dark area for me and I'd like to understand it better to make sure I'm not running an excessively heavy oil (fuel consumption is not my concern, just bearing temperature/friction).

Thanks

Chris

[TomLouwrier]

hi Chris,

In contrast with what many people believe it is not the pressure from the oil pump that keeps your bearings going. In a car engine the bearings are hydrodynamic, not hydrostatic. So it's the friction within the oil film, generated from the friction between the oil and the two moving parts (like crank and rod) that builds up a wedge shaped oil pressure profile. It is this pressure that actually carries the load and it's much higher than the few bar (psi if you're not metric) your oil pump delivers. (Mind you: this system needs a certain minimum bearing play as well in order to work. You can't close up your running clearances to nearly zero and think you have optimal, blue printed, bearings. Nope.)
The oil pump's main purpose is to feed the engine with enough oil volume so that the feed exceeds the leak down. That way your bearings won't run dry and thus can maintain their own internal pressure build-up.
Oil pressure as in 'main gallery pressure' is just an indicator for the oil pump's ability to keep the system fed with enough volume.

So a thicker oil would have less leak down and more friction, it can build up more pressure in the wedge and thus may offer more load carrying capacity. Nice, but if you're not using that capacity, no real gain. You do get some power losses however and maybe the thicker oil will not flow to small and remote locations (cam, tappet) with a high enough rate. That may mean starvation on that spot.
A very thin oil will leak down faster, meaning you need more volume to keep it going. The lesser friction means it will build up less pressure by itself, so it has less load bearing capacity. You can make up for this by running the engine faster or putting less load on the bearing.

As you see the main components here are: oil viscosity, oil feed rate, running clearance, bearing speed and bearing load. Given an engine with old bearings (lots of play) and bad oil (low viscosity) and a worn pump (low feed rate) then pulling hard from low revs is a sure way of breaking the oil film (in fact knocking through it) and damaging the bearing. The other way is to run the engine at such high speed and power that the leak exceeds the feed which makes it run dry and seize. Either way you're shafted (excuse my french).

Of course many engines rely on some form of oil spray, from either the rod or a dedicated nozzle, up the cylinders to keep the pistons cool enough. Too thick an oil may mean not enough volume there, leading to overheating of pistons. Similarly, too thin an oil may mean too much of the flow is lost to those cooling sprays and the main bearings get starved.
So too thick can be bad (starvation of 'the end of the line' and the cooling spray) and too thin will be bad as well (more leak down than feed rate).

Right now I can not tell you how much heat is actually generated in those bearings, I could look up the formulas etc if you insist. But look at it this way: lubrication is just one purpose of oil, the others being cooling, cleaning and noise reduction. In modern engines and oils the importance of lubrication, cooling and cleaning are often not placed in a specific order of importance anymore. Meaning: the cooling function is so important that there's a lot of heat transported by the oil.
At the moment my gut feeling is that the extra heat generated in the oil film will not have a significant influence on the total amount of heat carried in the oil.

regards
Tom

[WhizzMan]

I think Tom is right about the heat generated isn't out of tolerances with 10W60. In fact it isn't that much thicker than 10W40 at working temperature. A typical 10W60 has a viscosity of 25 or so cSt around working temperature (100 degrees Celsius). A 10W40 oil will be around 12 cSt or something close to that. That may sound like a big difference, but at 40 degrees Celsius 10W60 is around 150 cSt and a 10W40 oil can be anywhere between 70 and 100, depending on the manufacturer and what base oils and friction modifiers have been used.

150 cSt might sound high, but at 20 degrees 10W40 will probably be the same or even higher. There are various oil specifications suitable for almost every engine, depending on climate and most car manufacturers list those climates with the recommended oils in the user manuals of the cars. If you compare the viscosity of those oils at the temperature ranges given for cold start and assume 100 defgrees Celsius as "working temperature" you should know at what viscosity range your engine should be able to function. That's not the same as run optimally with as little wear or friction loss, for that you should be looking at the 70-100 degree celsius range and see if you can get an oil that matches somewhere in the mid range of that viscosity and also is sufficiently thin at your coldest starting event.

That is about viscosity, which is very important, but with modern engines, you will need to look at the additive package if you want your engine to last. The wrong additives or not enough and your engine will wear, your catalytic converter (if applicable) might die really quick and you'll be facing big repair bills. Get the right SAE and other additive packages specification and if you have no catalytic converter, get something with some ZDDP in it. Get additives from a recommended brand that is known to mix good with your brand of oil. A lot of aftermarket additives appear not to mix well, if I understand some people that claim to mix oil for a living correctly. Look on the internet, read up and form your own opinion, or just plain follow your car's manufacturers recommendations blindly. They may not be optimal given the fact that modern oils have improved, but they are good enough for your engine if you get the exact brand and type they prescribe.

[timinator]

Hi Chris, Hydraulic lifters bleed down for several reasons. If running 60wt. oil solves the problem then run it. The higher the weight oil describes how stable it is with increased temperature. All oil at normal operating temperature is as thin as water. I don't follow the reasoning that higher weight oil can't make it into small spaces. 20-50wt. synthetic oil pours out of my 5 quart oil can faster than mineral 10-30wt. I don't have scientific tests to back this up, however I have poured a lot of both, and that is what I believe.

I do not use oil heavier than 30wt. in n/a engines or 40wt. in turbo engines. This doesn't mean I am right, but it does indicate that I have not had to increase oil weight to solve any durability problems for the engines I build. However many of my customers insist on 20-50wt. so that is what they get. Have not noticed that it causes any problems or that it makes the engine last any longer. In your case the best answer is what you are doing because it solves your problem. Using oil coolers and oil temp. gauges are more important to the operation of the engine than what weight oil you use IMO.

Tim

[Brit01]

Tom, Tim and Whizzman: Thanks so much for your informative responses to my question.
I will read over them with interest again and take into consideration what you have suggested.

We tend to get fairly big changes in ambient temperatures between winter and summer here and I would like to swap between 15w/50 and 10w/60 but unfortunately the 2 grades are from different manufacturers here. I tend to think it's best to stay with one brand as not to mix the additive packages. I believe it takes a few changes to completely wash out the previous oil traces.

In winter we always make short stop/start trips around the city but in the hot summers we make long motorway journeys every weekend (but can get stuck in large traffic jams in heatwaves).

I'm concerned if I use the 10w/60 in the winter the working temperature will never be reached during the short trips.

Th 10W/60 Castrol does have a higher zinc level than the 15W/50 Motul (or 20W/60 Motul, currently used) so I'm inclined to try this out.
The Castrol is also the recommended/approved oil for most BMW models and I imagine these engines have very tight clearances.

Tim:

I do not use oil heavier than 30wt. in n/a engines or 40wt. in turbo engines.

What kind of oil pressures are you getting with a 30 viscosity oil when hot?

I don't follow the reasoning that higher weight oil can't make it into small spaces

I'm inclined to agree with you here. Think about the bearing clearances. 0.050mm for example and the 60 oil will flow through this and provide the wedge of oil no problem. So why the concern about a 1mm hole on the oil passage of a tappet?

Best regards,

Chris