Fuel injection rebuild

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Tony Z
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Re: Fuel injection rebuild

Post by Tony Z »

I've used JB Weld for the extensions too. It is the only epoxy that I can find that is rated for use in oil and at temps above where our oil sits. I do however still use a clamp, but I make sure its one of the HD clamps, not just a normal jubilee clamp. I then bury the clamp in epoxy too.

Hermans comments about the bolts are good too. I use cap screws and loctite blue for this spot, along with annealed copper washers.

Good progress!!


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Re: Fuel injection rebuild

Post by Simmy »

Thanks for the advice.

So I have clamped the tube using a normal stainless pipe clamp. I will keep an eye out for something more heavy duty.

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The temp sensor already has a home in the one pressure relief valve. I had a new plug made up with a hole for the sensor. I may just add another 1/8 NPT plug in the sump as a backup in case I want to move the dipstick sensor elsewhere one day.

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I have a variety of stainless fasteners which I can use to replace the studs. But I was wondering if it's better to use a nylock nut or threadlocker in these areas? I would think a nylock is oil resistant? Maybe a spring washer and threadlocker for added security?
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Re: Fuel injection rebuild

Post by Wentzel »

I have been meaning to ask, what size did you make the casing vents? 1/2" bspf tap and fittings?

I like to see your progress but havent posted any of mine yet.
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Re: Fuel injection rebuild

Post by Tony Z »

cap screw with a copper washer, inserted from the case side using loctite to ensure you dont ever unwind it back into the case. Nylock onto a copper washer to hold the sump in place, or double nut
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Re: Fuel injection rebuild

Post by Simmy »

Got it. Thanks Tony!

I stuck to NPT since that seems to standardise with all of the AN fittings. BSP would have been easier to find tools and fittings, but then all of the AN stuff would have needed adaptors.
The port is 3/8th... Again because then I only have 3 sizes of plug / port to worry about.
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Re: Fuel injection rebuild

Post by Simmy »

Not a huge amount got done this weekend, but here are the highlights:

Cleaned up the machining around the lifter bores. One of the lifters didn't seat fully as a result. No all of them are clean and burr-free. Also cleaned up the sealing surfaces... Someone here in another thread suggested polishing them would help ensure a leak free seal.

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And then I got to measuring... There is almost zero runout on the crank. Maybe 0.01mm at bearing 3, but little else noteworthy anywhere else.

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And then I decided it was time to torque the case together and measure the bores with the new bearings... Partial success...

Image

You can see all of the bores are basically round and oil clearance is right on the bottom end of the allowance range... Except for number 3. It's oval. Tried changing to the torquing sequence... No change.

So looking again at the bearing, I think I have found the issue. It's already tapered from the ends to the centers.

Image

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I did note before that I was suspicious of the bearings, so this just confirms it. I also checked them against the old set, which are also Mahle (I think). They are substantially heavier and better made (the other bearings are much the same as the originals):

Image

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I feel that they are far too flexible and hence are going oval when I put it together. I assume sturdier ones will be better.
So what do you guys think? I can't take them back, since I have already modified them. A new set? And then same brand again and hope?
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Re: Fuel injection rebuild

Post by Tony Z »

Your old bearing is likely steel backed, judging by the weight difference.

Your bearings being smaller at the join than in the middle actually rings a bell about something I learned about in my marine engineering classes, but I cant be sure anymore. I"ll see if I can dig up any info.
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Re: Fuel injection rebuild

Post by Tony Z »

I pulled this from a V8 site that I subscribe to, its worth reading but doesnt address your bearing taper


Is it better to build an engine with tighter bearing clearances and run it on low viscosity synthetic motor oil, or is it better to build an engine with more traditional or even looser bearing clearances and use heavier viscosity oil?


Tight bearing clearances and relatively thin synthetic multi-viscosity motor oils work well in many performance applications from NASCAR and circle track racing to drag racing.


Keep in mind, however, that most of these engines are purpose-built engines that are machined with exacting tolerances. Crankshaft journals are precision ground to be as round, flat and true as possible, the journals are micropolished to a mirror-like finish of a couple microinches Ra or less, the bearings are precision fit to exact tolerances using a bore gauge and micrometer (not deformable plastic gauge), and the engines are run on high quality synthetic racing oil, not ordinary motor oil.

The oil clearance is the gap between the inside diameter of an installed bearing and the outside diameter of the crankshaft or camshaft journal. The clearance is measured 90 degrees to the bearing parting line, which is the thickest part of the bearing (bearing thickness tapers slightly toward the parting line).


Reducing the oil clearance between the rod and main bearings and the crankshaft has a number of advantages. A smaller gap spreads the load over a wider area of the bearing surface and distributes pressure more uniformly across the bearing. That’s good, provided the bearing is strong enough to handle it. A smaller gap also decreases the volume of oil that has to flow into the bearing to maintain the oil film between the bearing and shaft.


That’s also good, provided the oil is thin enough (low viscosity) to flow well into the bearing. This also reduces the amount of oil pressure the engine needs, so some extra horsepower is gained by reducing the load on the oil pump.

In a NASCAR engine, rules limit the minimum diameters of the rod and main journals on the crankshaft. The rods are 1.850? in diameter while the mains are 1.999?. Most of these engines are running rod and main bearing clearances of .001? or less, and they are doing it with low viscosity racing oils such as 0W5, 0W30 and 0W50. These racing oils are as thin as water and are highly friction modified.


They also contain extra anti-wear additives such as ZDDP (phosphorus levels up to 1,850 ppm or higher) to protect the cam lobes and flat tappet lifters. These are race-only oils and are not recommended for street use because they do not contain the same detergents, dispersants and corrosion inhibitors as ordinary motor oils. Ordinary motors have to handle extended oil drain intervals while racing oils do not. Also, the level of ZDDP is too high for late model vehicles equipped with catalytic converters.


With fuel injection, many NASCAR engines are now making close to 900 horsepower without a restrictor plate, and are turning 9,500 rpms for 500 miles. The bearings take quite a pounding but hold up extremely well (when was the last time you heard of a NASCAR engine blowing because of a bearing failure?). But what works great for NASCAR may not work in other forms or racing or on the street.

One of the disadvantages of closer bearing clearances is that it can increase both bearing and oil temperatures. That’s no problem as long as the bearings and oil can handle the heat, but if they can’t it increases the risk of lubrication breakdown and bearing failure. That’s why high quality synthetic motor oil is absolutely essential if you are building an engine with tighter than normal clearances.


The old rule of thumb is to provide .0007? to .001? of bearing clearance for every inch of shaft diameter in a stock engine. Consequently, if the crankshaft has two-inch diameter journals, the rod and main bearings should be assembled with about .0015? to .002? of clearance.



For performance applications, some bearing manufacturers recommend adding an extra half a thousandth of clearance. Why? Because the rod bores don’t stay round in a performance engine at high rpm. When the piston reaches top dead center on the exhaust stroke, inertia stretches the rod and elongates the bore on the big end of the rod. This, in turn, deforms the bearings and reduces bearing clearances on the lower rod bearing while increasing it on the upper rod bearing.

For high revving performance engines, some bearing manufacturers recommend rod bearing clearances of .002? to .003?, with an absolute minimum clearance of no less than .0015?. The tighter the clearances, the tighter the geometry requirements are for the crank journals (as round, straight and smooth as possible with little or no taper).


Street engines can benefit from tighter tolerances and thinner oils for everyday driving. But when power adders such as nitrous oxide, turbocharging or supercharging are used, or the engine’s power output gets up in the 450 to 500 plus horsepower range, looser bearing clearances are probably safer to accommodate crankshaft flexing, main bore and rod bore distortion.


The same reasoning applies to drag motors, truck pull engines and other performance engines that produce serious horsepower. Many of these engines are built with rod and main bearing clearances in the .0025? to .003? range.


For the Saturday night dirt track racer, clearance is your friend because of the contaminants that often get into the crankcase. Looser is usually safer.

od and main bores should be as round as possible with no more than plus or minus .0005? of variation for a performance engine (.001? is close enough for stock). You also have to take into account the fact that the bearings themselves may not be perfect. Manufacturing tolerances of up to plus or minus .00025? are not unusual in some bearings, while others may vary only .00015? or less.


Main bore alignment is also critical. Some bearing manufacturers say adjacent main bores should have no more than .0005 inch of misalignment (.001? overall) if you are using tri-metal bearings, and no more than .002? of misalignment between adjacent bores (.002? overall) with aluminum bi-metal bearings.


One of the advantages of looser bearing clearances is that it allows more room for “slop,” which is important if the crankshaft isn’t machined to near perfection or there is some misalignment in the main bores. Wider bearing clearances do require a heavier viscosity oil (such as a 20W50 multi-viscosity oil or a straight 30, 40 or 50 oil). The heavier viscosity oil is absolutely necessary with wider clearances to maintain the oil film between the bearing and shaft so the bearing isn’t starved for lubrication. This also requires more oil pressure from the oil pump and/or more oil volume.

The amount of oil that is actually between the bearing and shaft surface at the point of highest load isn’t much. Though the installed gap between the bearing and shaft may be .001? to .0015? or more, the oil is displaced when the bearing is loaded. At its thinnest point, the oil film may only be .00002? thick (1/100th the diameter of a human hair!). That’s not much oil between the metal surfaces, but it doesn’t take much to maintain hydrostatic lubrication. When the shaft starts to turn, an oil wedge forms between the shaft and bearing that lifts the shaft up and away from the bearing surface. The shaft then glides on the oil with minimal friction.


If a crankshaft grinder wobbles while a crankshaft is being ground, it can leave lobes around the circumference of the journal. These may be invisible to the naked eye and very difficult to detect with a micrometer. But if there’s any distortion on the surface, it may interfere with the formation of the oil wedge under the shaft if the bearing clearances in the engine are too tight. Polishing the crank can reduce surface roughness on the journal but it won’t get rid of the lobes or ribbing.


Another factor to consider is that the upper Babbitt layer on a tri-metal bearing is very thin, typically .0005? to .0008? thick. The top layer of Babbitt acts as a dry film lubricant when there is no oil between the shaft and bearing. That’s fine for a dry start that may only last a couple revolutions of the crankshaft, but it is quickly wiped away if the engine starves for oil when it is running under heavy load or at high rpm.

And once the protective upper layer of Babbitt has been destroyed, the intermediate layer of copper/lead alloy will quickly seize if there’s no oil film to keep it separated from the shaft.


One of the reasons why many performance engine builders use tri-metal bearings is because they want bearings that have good seizure resistance in high rpm applications. Tri-metal bearings also handle high engine loads well and have good fatigue resistance. The Babbitt surface layer also provides embedability if dirt or debris gets past the oil filter. Tri-metal bearings are typically recommended for use with forged steel crankshafts.


Aluminum bi-metal bearings, by comparison, have high wear and corrosion resistance. With harder aluminum/silicon alloys, they can also handle higher loads while providing good anti-seize properties. Aluminum bearings are often recommended for cast iron cranks because they have a polishing effect on the journal surface. What’s more, according to some bearing manufacturers, a high silicon alloy aluminum bi-metal bearing will actually resist seizure longer than a tri-metal bearing if the protective oil film goes away.

That brings us back to the oil and bearing clearances. The oil doesn’t care what kind of bearing and shaft it is lubricating. It only needs to maintain enough oil film between the two surfaces to provide hydrodynamic lubrication and prevent metal-to-metal contact. There has to be enough oil pressure and flow to keep the bearings lubricated and cooled, and the oil itself has to have enough shear strength so it isn’t pushed out of the gap between the bearing and shaft at the point where the load is greatest.


Multi-viscosity synthetic motor oils flow more easily than conventional straight weight oils at both low and high temperatures. So they can handle cold starts as well as elevated operating temperatures (which is really important with turbochargers). To reduce friction and improve fuel economy, most late model stock engines are factory-filled with 5W20 or even 0W20 oil. Combined with tighter engine assembly tolerances, these oil and bearing combinations work relatively well for everyday driving and even mild performance use. For racing applications, though, the oil needs to be formulated specifically for racing – especially if the engine has a flat tappet cam that requires plenty of ZDDP in the additive package.

You can get oil viscosities ranging from 0W5 to 120W60, with 15W40 being a popular viscosity for stock car racing, road racing and spring cars. For wider bearing clearances, some prefer to use a heavier 15W50 or 20W50 oil. In drag racing Top Alcohol and Pro Mod classes, AHDRA Nitro Bikes and blown alcohol tractor pulling, 20W60 may be the lubricant of choice. For NHRA Top Fuel dragsters and Funny Cars, a 70WT oil might be used. So the type of oil that’s used will depend on the application and the bearing clearances inside the motor.


An additional layer of protection can be achieved by installing coated bearings. Various types of proprietary coatings are available that provide scuff resistance where there is no oil between the bearing and shaft. Such coatings cost extra, but are good insurance against dry starts and may save a crank if the engine loses oil pressure in a race.

Finally, regardless of what type of bearings you put in an engine or how close you set the bearing clearances, always use plenty of assembly lube to coat the bearings. Also, use the proper break-in oil when the engine is run for the first time. Break-in oils are typically a straight 30W oil without friction modifiers for fast ring seating. But they also contain extra ZDDP anti-wear additives to protect the cam and lifters. The break-in oil can then be drained and replaced with the type of oil (conventional or synthetic) that will be used from that point on. Be sure to tell your engine customer how important it is to use a high quality oil and that it has the correct viscosity to match the bearing clearances and lubrication requirements of the engine and application.
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Re: Fuel injection rebuild

Post by Tony Z »

and bingo, the thinner section near the parting line is supposed to be there, it helps form the oil wedge
https://www.autoserviceprofessional.com ... fts?Page=3

Also, from the Mahle Clevite website - pg9 left side above the picture
https://www.mahle-aftermarket.com/media ... -10-07.pdf

First, let’s define how and where clearance
should be measured. Half shell rod and main
bearings do not have a uniform wall. The wall
is thickest at 90 degrees from the split and
drops off a prescribed amount toward each
parting line, depending on the bearings intended
application. This drop off is called “
eccentricity.”
In addition, there is a relief at the parting lines.
eccentricity is used to tailor the bearing shell to
its mating hardware and to provide for hardware
deflections in operation.
eccentricity also helps
to promote oil film formation by providing a
wedge shape in the clearance space. The relief
at each parting line insures that there will not be
a step at the split line due to bearing cap shift
or the mating of bearing shells that differ slightly
in thickness within allowed tolerance limits. (See
figure 1.)
For these reasons, bearing clearances are
specified as “Vertical clearance” and must be
measured at 90 degrees to the split line. The
best method of measurement is with a dial bore
gage that measures the bearing Inside Diameter
when the bearings are installed at the specified
torque without the shaft in place. Measurements
should be taken at front, center and rear of
each bearing position. Another common method
of checking clearance is through the use of
Clevite
®
Plastigage
®
.
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Re: Fuel injection rebuild

Post by german »

Very interesting
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Re: Fuel injection rebuild

Post by Simmy »

Thanks for the info Tony. Not one of the shop manuals even touches on the subject... So this is all new and good info to have.

So, the full circle bearings should be expected to be round, but the split bearings are expected to oval slightly. In my case, I think it's still too oval, since the measured oil clearance is effectively 0.0 perpendicular to the split line. I want to double check the bore itself again, and try one more tightening sequence which I didn't investigate... If I am still unhappy, I am going to try source another set, maybe steel backed, if I am lucky and they don't cost the earth.
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Re: Fuel injection rebuild

Post by Simmy »

Guys, this is still not working. So I did some drawing... The measurements are for the torqued condition. So focusing on the horizontal measurements as Tony's article prescribes above... there is basically -0.02mm clearance which explains the binding.

Image

The only thing I can see as feasible is to either put some lapping compound onto the journal and turning it as I torque it up to effectively open up the bearing ID. Or getting that journal ground and polished some more. Any suggestions, please?!

I also seem to be getting a similar problem on the cam. It binds COMPLETELY as soon as I start tightening the nut closest to the thrust bearing. Having set the clearance previously, V'd the thrust edges at the parting line (photo below) and also used the mallet method to seat the bearing, it's still not moving. It looks like it's riding up on the edges as you can see below where the Babbitt is polished off. Measurement confirms that there is insufficient clearance when torqued up, but I don't remember by how much.

Image

Is it safe to use the lapping compound method here as well (this article suggests it http://haysvwrepair.com/rebuilding-an-a ... toy-style/). Or should I bite the bullet and get another set which hopefully doesn't suffer form the same problem?
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Re: Fuel injection rebuild

Post by Tony Z »

without being there to look myself I dont really know what to say
I'd give new bearings a try as a start.

Are you torquing up the case in the correct order? i.e. starting with that one single M8 bolt first, before torquing up the big case bolts, then followed by all the other M8 case bolts?
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Re: Fuel injection rebuild

Post by Simmy »

I believe I am. M8 cam bolts at rear to 14ftlbs, then progressively torque up the big nuts in steps of 5 to 25, but it binds almost immediately anyway. Found that the centre cam bearing is doing exactly the same as the thrust bearing. I really think they just have high spots.

They are KS bearings, which I thought were decent, but I have seen others say otherwise. Both sets bind, so there isn't much chance just fiddling the pairs around to get it to work.
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Re: Fuel injection rebuild

Post by Tony Z »

I've never had this problem before. I use KS and Mahle when I can find them.
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