Lotus Elan

oil pump question

PostPost by: 2cams70 » Sat Sep 02, 2017 4:04 pm

Hi Guys,
I'm in the process of converting a NOS Ford oil pump over to HV / HP specs. Why is it that on all the high pressure pumps I see the spring loaded filter bypass valve is replaced with a blanking plug? Isn't the bypass valve there so that should the filter become blocked oil can bypass the filter so the engine isn't starved of oil? Surely this is a good thing and so it would be best to have the valve in place regardless of whether the pump is HP or not?
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High pressure on left, standard on right
1970 Ford Escort Twin Cam
1972 Ford Escort GT1600 Twin Cam
1980 Ford Escort 2.0 Ghia
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PostPost by: mark030358 » Sat Sep 02, 2017 7:34 pm

Isn't the spring the pressure relief valve? And not a bypass?..
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PostPost by: Craven » Sat Sep 02, 2017 7:44 pm

Subliminal Flash,
you can raise the operating pressure of the pump by gently tapping the blanking cap further in!!!
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PostPost by: rgh0 » Sat Sep 02, 2017 10:32 pm

Modern replacement pumps have done away with the filter bypass valve to save costs I presume. Given the care and attention and low mileage of most Elans these days it is not a problem. They have also done away with the relief valve dump port back to the sump and just recycle in the pump itself.

Be careful when changing over the internals of a HP / HV pump into an original body as some of the dimensions may be different and not fit correctly. I tried it a few years ago and gave up in the end due to differences. I was doing it due to cracking in the pump bodies at high revs due to engine vibration

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PostPost by: promotor » Sun Sep 03, 2017 7:39 am

As a HV/HP pump is mostly intended for a racer then the maintenance schedule is likely to be better than a daily driver.
The by-pass was needed in the days when oil would become sludgy and build up inside the filter when owners perhaps didn't change their oil as regularly as they should.

If putting in a replacement set of rotors check to see that the outer rotor has a chamfer on one of the outer edges (sometimes they have a chamfer either side as a fool-proof mechanism) - this chamfer is to run facing the alloy body - a sharp edge can cause cracking in the corner of the rotor housing. The sharp edge is to face the outer plate.

Something else to consider is that high volume is better than high pressure, and that high pressure has the effect of causing more load on the skew gears on the pump shaft and jackshaft so will likely introduce wear much more quickly. However, the fact that you are likely to be using an original Ford(?) skew gear will certainly help. I have heard that the modern skew gears aren't too soft as most people think but are actually too hard and are ripping camshaft/jackshafts to pieces.

Of course the lower miles that people are doing in their classics should mean that problems are caught for more quickly in mechanical life terms than if doing 10,000 miles a year.
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PostPost by: 2cams70 » Sun Sep 03, 2017 2:08 pm

Thanks guys. What I don't understand though is that if one buys a standard replacement pattern pump these days (original Eaton pumps as originally supplied to Ford are NLA) they still always include the bypass valve whereas the HP or HP/HV versions don't. Surely if modern thinking is that it's not required they would delete the bypass valve on the standard pump too? Also if one buys an oil pump uprating kit to increase the pressure of a standard pump it includes a disc blanking plug to replace the bypass valve.

I managed to find an early NOS Ford canister type oil pump that was HV / HP. It seems to be a factory supplied part and not an aftermarket modified standard pump. I'm transferring the innards of this to an NOS Ford Spin on type pump. Having dismantled two NOS Ford spin on pumps I can say that the quality control on even the Ford pumps is a bit hit and miss! The first pump had a very roughly machined bore for the pump rotor shaft. There wasn't excessive play but with all the machining ridges and gouges I'm not sure how long it would last! The second pump was OK in the rotor shaft bore but not too good in the machining of the bore for the outer rotor - again there were gouges in this case about 2mm wide and detectable with a finger. I'm taking my bets with using the second but it's not perfect.

One thing I did notice is that the standard spin on pump is slightly higher flow than the standard canister type pump. The standard spin on pump has a slightly wider rotor.

Interesting comments about the drive gear. Disregarding the cost do you think the standard Ford gear is better or one of the tuftrided ones from Burton's or QED. I believe the tuftrifded one can be used together with the original cast jackshaft without problems but would like to seek your opinion.
1970 Ford Escort Twin Cam
1972 Ford Escort GT1600 Twin Cam
1980 Ford Escort 2.0 Ghia
Peugeot 505 GTI Wagons (5spdx1) (Autox1)
2015 Honda City 5spd.
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PostPost by: Chancer » Sun Sep 03, 2017 2:39 pm

I cant recall the internal porting of the standard pump having concentrated on the 5 port dry sump pumps in the main but I think the problem with retaining the bypass valve on an uprated pump is that of it bypassing at higher revs when the o?l is cold, precisely the conditions for high wear when you want the o?l to be filtered.

I had similar problems on my first dry sump set up until I increased the diameter of the o?l lines.
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PostPost by: William2 » Sun Sep 03, 2017 4:52 pm

Many people have told me over the years that an HP pump on a standard engine road use car is not necessary and that the pump will put unnecessary additional pressure on all the oil seals/gaskets.
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PostPost by: 2cams70 » Sun Sep 03, 2017 10:22 pm

I would normally agree with you but this engine has a steel crank and rods so I guess the HP/HV pump gives a bit of extra peace of mind!
1970 Ford Escort Twin Cam
1972 Ford Escort GT1600 Twin Cam
1980 Ford Escort 2.0 Ghia
Peugeot 505 GTI Wagons (5spdx1) (Autox1)
2015 Honda City 5spd.
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