Gents,

Mentioned a couple of days ago was a mod to the oil pump to get some more oil through it.
How much do I need to overbore, and how eccentric?.
I presume I then need to make and fit new veins and springs. Does anybody have a drawing with dims I can work to?

Hedd

I think its 1/64th offset and 1/32nd overbore?

Just a quick point, mine has been "done" and runs off the scale cold and just off the scale when running hard at 60 mph (innacurate speedo). It only comes down when running slowly or if it gets really hot when climbing a hill (or when I run out of oil on the A30, but thats another story!). I would think that a 0-20psi gauge would be a good mod, but I cant find one at the right price!

regards

Steve.

Hedd,

As steve has said you need to increase the offset by half the ammount you increase the diameter of the bore.
It is important to only just clean up the bore at the new offset, ie remove very little material on the outlet side of the pump. I dont think there is any need for modified vanes and springs.

You asked on the earlier thread about getting the jets out. Remove the plugs over the jets and drift them out, was not difficult when i did it (crank and rods probably need to be out). This damage the ends of the jets as they are fairly thin wall section but this wont matter if you are replacing them with new bigger ones. I can check the dimensions for boring out the pump and the bigger jets tomorrow.

My dad has done this mod on both his cars and has modified the size of the jets by the appropriate ammount to give the same pressure so the original gauge is fine.

Regards

Rob

Rob,

If you could get all the dims that would be very usefull, the bore on my oil pump is a bit scored hence why I thought boring it bigger would be the way forward. Keeping the standard pressure but with more oil seems a better way than the higher pressure. I dont want it to leak more oil than 'standard'!

Many thanks

Hedd

The dims quoted are right. 1/64 extra offset, 1/32 bore. Standard vanes & springs, as long as they are OK, Make sure that any scoring on the end plate is removed.

No reason for your engine to leak oil these days!!

STEVE

Hedd,
Why don't you take it a step further if you want to protect your big ends and make a 4-jet lub system as shown in A7 Companion I think. I have done 2 cars like this .It isn't a big job to make,just a bit fiddly to fit and line up. Well worth it for peace of mind.
Regards,
Dave.

Because I've got better things to do with my time than to improve a design that has proved itself to work!. The oil pump needs boring out as it is scored, and Id like to keep the pressure as original. Can anybody help with a oil jet size to accomplish this.

Other projects on the go include fitting a new firebox into my steam roller,

I have just measured jets in 3 crankcases:- 2 forward starter types and one die-cast rearward starter 1931 type. I can just put the shank of a 3/32" drill down those jets which have not been made out-of round.I know you do not want to try 4 jets but as you will need to align the jets with the crank troughs if you have access to a copy of the A7 companion there is a good article in it by MJ Forrest on p251.
Sorry can't help you with the steam roller.

I have the austin 7 companion, I'll look it up.

If you are interested in the steamroller look at
www.geocities.com/austin7_and_steam

Hedd,

My Dad is away at the moment, should be back by the end of the week i will post the details of his mod to the jets as soon as i can get them from him.

Regards

Rob

Eye by-gum, that roller would make short work of any Austin 7 that got in the way!

Good luck with the project.

Cheers,
DG

Hi Hedd,

The standard jets are:

OD 5/32"
ID 3/32"
Head OD 3/16"

This gives the area of the bore as 0.002197 sq inch

The modified jet details are as follows:

OD 11/64"
ID 7/64"
Head OD 3/16"

This gives the area of the bore as 0.002991sq inch

This doesnt sound much but it is a 36% increase in area and therefore flow. Dad was fairly sure he had modified the pump to the same dimensions as mentioned previously, I know he would have done it by as much as physically possible. The effect on our cars was to give the standard pressure on the gauge.

In order to fit the jets you will need to carefully drill the hole in the crankcase out to 11/64, this is best done on a mill or good pillar drill. This does not leave much of a head on the jet but it is enough. The head cannot be bigger without interfering with the core diameter of the thread for the plug. Obviously to make the jets you will need access to a lathe.

Dad also bent the jets inwards to sqirt at the crank for a larger part of the rotation but not by a huge ammount.

I hope this helps!

Regards

Rob

Many thanks Rob.

Hedd,

My dad has checked one of his modified pumps (machined out four or five once the machine was set up). The original pump bore is 1" the modified ones are 1.045" with the offset increased by 0.0225" accordingly. The rotor is 7/8" so the pump capacity is increased by approx 39%.

Just realised the jet areas i gave on the previous post were out by a factor of Pi (i had just got back from the pub). They should read 0.006903sq inch standard and 0.009396sq inch modified. Percentage increase was correct at 36%. This means the pressure is a tiny bit higher than standard but what you actually get depends on how much everything else leaks.

Cheers

Rob

Okey dokey, seems the steam roller is a little simpler in the lubrication dept. Total loss.