Crankshaft drilling

[old grumpy]

Now and then I read about cross-drilling the crankshaft to get more oil to the 3:rd conrod bearing. This operation is not that easy. Is it still mandatory for the fast revving motor? Has everyone who is operating a racing or go-fast engine done this?

 

[old grumpy]

I assume..............

 

[Bill Blue]

The 3 main engine is notorious for spitting #3 rod bearings. It can happen quite easily, even in a non racing engine/use. It did to me 40 years ago.

I do not think it is an issue with the 5 main engine.

And that's all I got to say about that.

Bill

 

[old grumpy]

The 3 main engine is notorious for spitting #3 rod bearings. It can happen quite easily, even in a non racing engine/use. It did to me 40 years ago.

I do not think it is an issue with the 5 main engine.

And that's all I got to say about that.

Bill

"notorious" You said, not "rarely" How about "spitting #3 rod reluctant" (no, sounds silly)...seldom? well, the point is I don't like the world "notorious" It's so.............so.......negative...

 

[Bill Blue]

"notorious" You said, not "rarely" How about "spitting #3 rod reluctant" (no, sounds silly)...seldom? well, the point is I don't like the world "notorious" It's so.............so.......negative...

I guess you could say "seldom" as it usually happens only once per engine.

Bill

 

[old grumpy]

I guess you could say "seldom" as it usually happens only once per engine.

Bill

That means every engine! A 100% disaster record!
Odd, it has never happen to me. So crankshaft drilling is the answer?
Higher oil pressure maybe?

Or do you have a very bad relationship with this engine?

 

[alpine_64]

The 1500 (1494 series I) had a reputation for spinning bearnings, rootes reacted to this by stiffening block and making a forged crank for the 1600 (1592 Series II) motors. The later 1600's IIRC dont have a forged crank.. so they obviously dcided the issue was solved.

As for the 1725.. they had a rep for #3 big ends going didnt they.. and in racing.. often,

low oil pressure in any alpine is a bad sign.. and it they have it.. you are on borrowed time. You need ot make sure the pump is not worn and the OPRV is not sticking.. if its the celarences on the bearings.. you will ikely loose one sooner or later.

As for cross drilling the crank.. not sure... back in the day they used to knife edge the cranks.. not sure they cross drilled.

As a side note.. much like the MG guys.. many racers think the 3 mains are a sweeter free revving motors VS 5 main.. but 5 have a rep for being stronger.. perhaps underserved?

 

[Bill Blue]

That means every engine! A 100% disaster record!
Odd, it has never happen to me. So crankshaft drilling is the answer?
Higher oil pressure maybe?

Or do you have a very bad relationship with this engine?

I had an early Series II have a #3 rod to start ticking. Had it replaced, the mechanic (a personal friend of my Father) said I caught the problem before the crank was damaged. Everything else was good. This was at about 25K miles. Whenever you hear of an Alpine loosing a rod, it is always #3. The only rod bearing I've lost, driving cars for hundreds of thousands of miles on engines.

Several years ago, RootesRacer posted rather extensively on this problem. I don't know the answer.

Bill

 

[puff4]

Yes, but is this true of the later 1725 motors? I had thought by then it had been resolved.

 

[65beam]

drilling

i've had two 1725's that had bearing failure on #3. the first 69GT that i bought back in the late 70's had a hole in the block at #3 due to bearing failure and another time i was driving the wife's series 5 on I85 east of atlanta when #3 failed. the risk must still be there.

 

[old grumpy]

I had an early Series II have a #3 rod to start ticking. Had it replaced, the mechanic (a personal friend of my Father) said I caught the problem before the crank was damaged. Everything else was good. This was at about 25K miles. Whenever you hear of an Alpine loosing a rod, it is always #3. The only rod bearing I've lost, driving cars for hundreds of thousands of miles on engines.

Several years ago, RootesRacer posted rather extensively on this problem. I don't know the answer.

Bill

Mr RootesRacer! Where can this post be found?

 

[puff4]

i've had two 1725's that had bearing failure on #3. the first 69GT that i bought back in the late 70's had a hole in the block at #3 due to bearing failure and another time i was driving the wife's series 5 on I85 east of atlanta when #3 failed. the risk must still be there.

Hmm... OK. So is this crankshaft drilling process documented somewhere?

 

[RootesRacer]

Hmm... OK. So is this crankshaft drilling process documented somewhere?

IIRC there is mention of it in the series II competition handbook.

Its a pretty simple mod since its just enlarging a passage that's already drilled.
The consensus is that this particular journal doesn't get enough oil from the main gallery. Enlarging the path helps.

 

[puff4]

IIRC there is mention of it in the series II competition handbook.

Its a pretty simple mod since its just enlarging a passage that's already drilled.
The consensus is that this particular journal doesn't get enough oil from the main gallery. Enlarging the path helps.

I don't see it in that comp prep manual.

• http://www.sunbeamalpine.org/downloads/Sunbeam_Alpine_Special_Tuning.pdf

And I also don't see it in the "Building a bulletproof Alpine runner" article from way back, either.

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

Anybody else know where this exists? I'm not doubting it, mind you, just trying to find the proper instructions to DO it!

 

[old grumpy]

IIRC there is mention of it in the series II competition handbook.

Its a pretty simple mod since its just enlarging a passage that's already drilled.
The consensus is that this particular journal doesn't get enough oil from the main gallery. Enlarging the path helps.

Are we talking about the 3-bearing crank?
First and forth bearing have oil from their own main bearing. The second and third bearing has oil delivery from the middle main bearing so in reality both would be in danger. The passage is about 5,5 m.m. 7/32 inch. How much enlarging is necessary?

 

[puff4]

Actually, if what's being said here is correct, it seems BOTH the 5 and 3 main bearing cranks suffer from this problem.

 

[old grumpy]

Actually, if what's being said here is correct, it seems BOTH the 5 and 3 main bearing cranks suffer from this problem.

Funny, I have never had this problem on any engine . Not even when I did run the car with water in the oil 50/50% The engine didn't brake down but when I did take the engine apart all bearings looked funny. (for a natural reason)

 

[owakip]

A fix for big end failure

I race a very successful ( front runner) Alpine motored race car in NZ. I had on going bearing failure problems on both 1725 and 1600cc engines.... Inhad tried the normal fixes...drilled the centre main gallery, upped the oil pump output and relief valve pressure, plumbed in an a
Acusump and still had failures. The problem was cavitation on the inlet side of the oil pump... The fix ... throw away the original gauze filter on the oil pick -up and replace it with a MUCH coarser gauze + preferably increase it's surface area. I also smoothed out the inlet port of the oil pump with a die grinder (carefully)... The result... two full seasons of racing with no problems.. and I come in after a race still with 65psi oil pressure.

 

[tigretr]

Cross drilling may help get more oil to the bearings, but if it is not delivered in the right place on the bearing it will be only of marginal help. The real issue with the Alpine crankshaft is that the oil is not delivered to the crankshaft in the optimum position relative to peak pressure exerted by the rod as a result of combustion. The goal is to ensure the oil wedge is at its thickest when peak pressures are seen. That is as the crank swings over TDC combustion has already started. As pressure builds between the connecting rod and the crank, you want that oil hole to be delivering oil in that area or just before it. If it is too early or too late the oil wedge is already thinning and physical contact between the crank and the bearings is more likely. Add to that high RPM's and the resulting higher power associated with RPM's and you get what many of us have experienced. The number 2 and 3 rod journals are particularly susceptible to failure since that middle journal on the crank is not only feeding 2 rod bearings but also the entire top end of the motor. Add to that an old oil pump and your problems are exacerbated.

When I had my turbo motor built (after spinning the #3 rod bearing), my engine builder assessed the peak pressure relative to the existing holes in the crank and determined they were in a less than optimal position. We then welded up the existing hole and re-drilled new holes which were more appropriately placed. Wish I had more information on where we put the holes relative to the existing ones. I would need to look for a picture if someone is interested.

Brian

 

[bmohr]

Hi Brian,

If you still have the pictures, I'd be interested in the information. If it's more convenient, my email address is mohrstuff. The domain is gmail dot ummm com.

I saw the pictures of your engine in the gallery. Pretty nice work.

Thanks,