oil passages in 1725 block

[Tom H]

Last October there was this exchange:

Quote:
Originally Posted by Jim E
Jan you ever drill the one oil passage in the block like is sugested?

Yes, I do that on every 1725 engine that I rebuild. That modification, I would approve.
Jan

There was no answer posted. Jan, Jim E, or anyone, can you explain please before I assemble my 1725 (now 1820) block.

Thanks, Tom

 

[husky drvr]

Last October there was this exchange:

Quote:
Originally Posted by Jim E
Jan you ever drill the one oil passage in the block like is suggested?

Yes, I do that on every 1725 engine that I rebuild. That modification, I would approve.
Jan

There was no answer posted. Jan, Jim E, or anyone, can you explain please before I assemble my 1725 (now 1820) block.

Thanks, Tom

I am curious also. I do not recall ever hearing about this modification until that post. What passage? Whose suggestion? Why is this modification needed? What does it accomplish?

 

[Tom H]

Jim E, Jan, You guys started this

Jim, Jan, You guys started this isssue about oil passage mod. How about an answer. Inquiring minds want to know.
Thanks,

Tom

 

[jumpinjan]

The interest here are the branches that branch off the main gallery to each main bearing. They can be opened slightly to get more flow. I don't know what the drill size is, but the idea is to enlarge them.
Jan

 

[AlsPine]

Here is some info I got off of an alpine site on the net.

Here is the link

http://www.team.net/www/rootes/sunbeam/alpine/mk1-5/techtips/techtips.html



Engine oiling modifications for improved reliability:

1. Groove the center main journal on the crank the width of the groove in the bearing shell and approximately .060 inch deep.

2. Drill the oil passage from the main oil galley to the center main all the way with a 21/64 inch drill bit.

3. File the oil pump housing to provide no more than .001 inch of end play for the pump gears.

4. Obtain a new oil pressure relief valve or shim the old one to provide 60 psi of oil pressure. These valves are also prone to sticking if the pistons are too tight.

5. Be sure and remove all the oil galley plugs and thoroughly clean the block. Don't have the block cleaned at the machine shop without also cleaning it thoroughly yourself before assembly.

Of course, the previous should be augmented with good high performance engine preparation techniques. Also, to make power above 6000 RPM, you'll need some cylinder head work and a high performance camshaft.

Milo Muterspaugh
Colorado Springs

 

[AlsPine]

The link didn't come out on the post, so here it is again. Just add the HTTP WWW to it.

team.net/www/rootes/sunbeam/alpine/mk1-5/techtips/techtips.html

 

[AlsPine]

More good info from that link.

Jarrid Gross' modified 1725cc oil pressure relief valve



Here are the instructions:Chuck the old relief valve in a lathe, then machine the pip on the end
"if it has one" flush with the base of the hex.
Use the lathe to "drill" a 3/8 inch ID hole into outside of the hex.
Be carefull,and slow, because when you reach the piston bore, the
spring will want to pop out.
After you get the spring and piston out, debur the inside bore to elliminate
any blemishes from the bore that may impede or even stick the valve open
Tap the new hole with a 7/16 fine tap to just inside the bore 1/16 inch.
Get a brass 7/16 fine bolt and a stainless steel washer that fits inside the
newly tapped hole.
Turn the brass bolt in a lathe to remove the last few threads, so the
brass bolt can be turned beyond the end of the threads.
Radius the end of the bolt so that is captures the stainless washer and
allows the bolt to rotate against the washer like a bearing.
Clean, Clean, Clean all the parts, then install the piston, spring and
washer.
Put a liberal amount of non-hardening threadsealer to the bolt, then
screw it into the valve body until spring resistance is felt.
Turn 2 more turns on the bolt to insure adequate oil pressure for startup.
Install the valve into the filter base, then start the engine. If the pressure
is too high or too low, adjust it immediately. Clockwise rotation will
increase the pressure, and counterclockwise will decrease the pressure.
I recommend adjusting the relief valve to 65 PSI at 3000 RPM.
Oil condition, viscosity and temperature will all effect the operating pressure,
so adjust to whatever condition that you feel is appropriate.
Setting the pressure too high, will put more load on the pump, and could
cause the pump shaft to shear at the pump rotor.

prvalve.gif

 

[Jim E]

I was refering to the main oil passage. Also lap the oil pump housing for as near zero clearance as posible. Not sure about the groove in the main cap never found a shop that would do it. Do not care for the oil pressure relief valve mod, pretty easy to screw that up and relief valves that are good are not all that easy to find. Setting the crank thrust up right is important and something that seems to get over looked if the number of new built engines I have seen with spit thrust washers is any sign. Oh I also like to resize the big ends of the rods or at least check them.

I am very interested in seeing how the chevy rod engines hold up over time and if they are better when it comes to low RPM oil pressure [idle that is], and spinning number three rod bearing. Chevy rod guys how is your oil pressure?

 

[RootesRacer]

I am very interested in seeing how the chevy rod engines hold up over time and if they are better when it comes to low RPM oil pressure [idle that is], and spinning number three rod bearing. Chevy rod guys how is your oil pressure?

My oil pressure never dips below 60psi, but this is because I modified an the oil pump to take the MGB gerotor set, which adds 22% more oil capacity.

 

[alpine_64]

Jarrid,

Are you pinning the bearings? Have you had any trouble with the high psi moving them?

 

[RootesRacer]

Jarrid,

Are you pinning the bearings? Have you had any trouble with the high psi moving them?

I would hardly call that high PSI.

I thought about pinning the mains, and when I sent it all off the the shop, didnt discuss it with the machinist, so it didnt get done.

I am now considering making a girdle for the mains.

That would be almost as good.

 

[Tom H]

Pinning? Girdle? I can figure that pinning the bearings means adding a pin or two to each (or at least one) bearing half and drilling a hole in both the bearing and the shaft bore and putting a pin there to keep the bearing from spinning. Or maybe just putting a hollow "pin" in the existing oil hole, presumeably after expanding the hole in the bearing and bore slightly. Is that correct ?

But I cannot imagine what a bearing girdle would be. Could you please explain.

Thanks.

Tom

 

[RootesRacer]

Pinning? Girdle? I can figure that pinning the bearings means adding a pin or two to each (or at least one) bearing half and drilling a hole in both the bearing and the shaft bore and putting a pin there to keep the bearing from spinning. Or maybe just putting a hollow "pin" in the existing oil hole, presumeably after expanding the hole in the bearing and bore slightly. Is that correct ?

But I cannot imagine what a bearing girdle would be. Could you please explain.

Thanks.

Tom

Pinning often is not actually pinning but rather having a sleeve or guide installed in the block where the main threads are. The cap is then machined so that it has a very close tolerance to the sleeve and as a result, the caps cant walk around too much, which is a bad thing at high RPMs.

A girdle is a method to keep the caps lined up that physically connects the caps to one another (and often to the block too) via a structure.
Many newer hipo engines are designed with a cast girdle, which really stiffens the bottom end.

 

[Bill Blue]

Pinning? Girdle? I can figure that pinning the bearings means adding a pin or two to each (or at least one) bearing half and drilling a hole in both the bearing and the shaft bore and putting a pin there to keep the bearing from spinning. Or maybe just putting a hollow "pin" in the existing oil hole, presumeably after expanding the hole in the bearing and bore slightly. Is that correct ?

But I cannot imagine what a bearing girdle would be. Could you please explain.

Thanks.

Tom

Tom, the procedure you describe of drilling a hole and using a roll pin can be used on the bearings. It too is called "pinning the bearing". So I'd say you made a good guess.

Bill