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Lotus Twin Cam .120" oil orifice...pinging Rod;

Lotus Twin Cam .120" oil orifice...pinging Rod;

Lotus Twin Cam .120" oil orifice...pinging Rod;

(OP)
Examination of the illustrations in the David Bean catalog shows an oil restrictor, #1710 with an orifice of 0.120".

A friend of mine over on the Europa board, is having low oil pressure problems on a fresh Twin Cam overhaul, clutching at straws now; but is anyone familiar with the placement of the orifice, and the likelihood of it's being overlooked during an overhaul? "overlooked" means "left out" of the casting. I would assume it would be removed for cleaning the oil galleries?

  

RE: Lotus Twin Cam .120" oil orifice...pinging Rod;

...so from a project standpoint, when confronted with such a problem, I'd have a quick brainstorm session to try to identify other possible causes of the problem, then eliminate the easy ones first, then go after the hard ones.  You might find that there is no way around another teardown, in which case it doesn't matter whether the orifice was left out or not, because you'll soon be looking for it.

in general, I'd start with whether you can determine adequacy of supply volume (or at least reduce the probability that supply is too low), then go after places where the oil could be escaping too easily (missing or damaged gasket?  misplaced cooling jet?  bearing with too much clearance?  missing orifice?)
   

RE: Lotus Twin Cam .120" oil orifice...pinging Rod;

And of course double check that gauge/sender, too.

RE: Lotus Twin Cam .120" oil orifice...pinging Rod;

(OP)
Yeah, all the easy stuff has been checked, pick up tube reswadged, (seemed a little loose where it was pressed into the block) screen verified clean, a "New" oil pump installed, mechanical direct reading gauge of known servicability installed, NO JOY.

an old moss-back once told me (regarding troubleshooting) if you're out in the Texas panhandle, and you hear the thundering sound of hoof-beats, don't think of zebras right off the bat. Think of horses or cattle.

In this case, the horses & cattle have been ruled out.

I understand that the orifice is in a place that will involve pretty invasive, labor intensive work to access.

thanks for the input!

RE: Lotus Twin Cam .120" oil orifice...pinging Rod;

(OP)
I need to add that off idle, ( I wouldn't have tried this, myself ) oil pressure builds in a linear fashion with RPM, 60 psi @ 2500 RPM, no load.

RE: Lotus Twin Cam .120" oil orifice...pinging Rod;

so the pump is working and the oil is leaking out somewhere... that orifice might be the culprit.
 

RE: Lotus Twin Cam .120" oil orifice...pinging Rod;

Never seen a problem with the oil restrictor orifice.  Generally, without it the top end would simply be flooded and I would think that would be noticeable.  What it may be, and it's happened to me once when I was just learning the twincam Fords, is you may have the wrong main bearings.  The factory (god love the British) had some bad block castings and rather than scrap them it was customary to over bore the mains 0.015" and fit oversize bearing shells to compensate.  If, like me, you don't notice and put in standard shells, you will have the same problems as you describe.  I have heard of it happening to others since then.  My mantra is NEVER skip a quick Plastiguage....

Okay, I reread the posts and you mention the oil pickup.  That is definitely something to consider.  The early wet sumps had threaded blocks and the later Kent blocks had pressed in.  I have had similar oil problems (air sucked into the pickup) and resultant bearing failure from improperly installed oil pickup. I don't use the stock oil pump or pickup so I had not thought of that.  Also, the early pumps had the ck valve spring come loose when mechanics put a washer behind it to boost oil pressure.  Stock twincams live quite well with 55psi hot and our race engines at 95psi hot (not attainable with a stock pump) but people still try by 'shimming' the ck valve.  If you want a bit higher pressure, change the spring.

One other problem I encountered due to replacing the rear main oil gallery inspection plug with one that was a bit too long thus covering the secondary oil drilling to the main bearings...That was another dumb move on my part...low oil pressure to the mains and subsequent failure...There is a lot to learn AND a lot to forget.  I hope some of this helps.

Rod

RE: Lotus Twin Cam .120" oil orifice...pinging Rod;

Having worked on one a long time ago, reaching into the corner of my head tells me the restrictor was pressed into block deck, before placing head. It was a so called aftermarket part as such, as the heads took far too much oil than was needed at high rpm. This lead to flooding, and failure to return to sump fast enough which meant the breathers took a hammering as did the priority journals/drillings.

My point is, its a simple test to see what is happening. Measure oil pressure at block, and then at head. If you have no pressure to head, its blocked. Or gasket could be fitted incorrectly(can you place these upsidedown?)
The engine should work fine without said flow restrictor since it was a sort of after thought. Which then leads me to believe its either blocked(If you have block pressure, but not head) or that your problems lie with the pressure bypass stuck open on the oiling circuit.
I have two links here on said issue which may interest you also,
http://www.lotuselan.net/forums/elan-f15/cylinder-head-oil-restrictor-t16875.html
See other link, on that link.
Its a long time ago since I built one of these, so maybe the links will provide more use than I can, but I do know It not being there will not matter. If its blocked, it will matter, do a block, and head pressure test and see if they are the same. If they are both low, suspect oil bypass. And also know that a new, dealer pump can have a faulty bypass as I found out, 3 times in 12 years. When you have to start doubting new genuine parts, engine building quickly becomes not fun anymore...

BG

 

RE: Lotus Twin Cam .120" oil orifice...pinging Rod;

Rod beat me to it, hes fast for an old guy ;P!

RE: Lotus Twin Cam .120" oil orifice...pinging Rod;



tongue

Ole Rod...

RE: Lotus Twin Cam .120" oil orifice...pinging Rod;

Dumb question-what oil pressure is he getting?
I am happy to defer to the experts above, but "normal" oil pressure for the standard Kent engine is 40 psi.
My twin cam runs 35/45 psi and talking to more knowledgable persons than I, the consensus is volume is more important than pressure.
Chasing pressure gives a reduction in motor HP, when it may not be required.
Ross

RE: Lotus Twin Cam .120" oil orifice...pinging Rod;

(OP)
a cut & paste from the original post:

"My rebuilt twin cam filled with 20W-50 has no oil pressure at start-up, but builds pressure at higher RPM. At engine speeds above about 1500 RPM, the oil pressure fluctuates. At idle, the oil pressure drops to near zero. I've verified the symptoms with a mechanical oil pressure gauge."

He's plastigaged the bearings, last post I saw,

NO JOY

RE: Lotus Twin Cam .120" oil orifice...pinging Rod;

Yeah, would be nice to have a followup, TTF.
My money is still on the oversize main bearing bore.

Ross, back in the day, we would replace the ck valve spring to get a small boost in pressure and about 55psi hot was all the 'high volume' pump would do (that's 85+ cold and you had to be very careful not to rev the engine above 3000 until the oil warmed).  Today we use a multistage dry sump pump suitably plumbed into the wet sump to achieve the 95psi hot pressures and still maintain less than 100psi cold...still using caution with revs until the oil warms.
We also now have an accumulator plumbed into the system (55psi release pressure) where back in the day we did not.  It's all about leaving no stone unturned.  If it saves ONE engine it will pay for it's expense.  My engines in the late 60's made about 165hp, the same engine in the late 70's, 185hp...Today our David Vegher tuned engine is 197hp@8400rpm and he, as well as other vintage Lotus twincam tuners, are making in excess of 200hp from 1600cc on a regular, reliable basis.  In order to make these high hp engines live at 9000+ rpm, it takes high flow and high pressure oil systems.

There is a world of difference in racing and street preparation.  What will work reliably on the street often will end in catastrophic failure on the track...AND VICE-VERSA!

Rod

RE: Lotus Twin Cam .120" oil orifice...pinging Rod;

(OP)
"mains have huge clearances" (speaking of axial movement on the crankshaft)

QUOTE FROM THE POOR GUY DEALING WITH THIS ISSUE.

Now, "Huge" is a pretty subjective measurement.

What sets crankshaft end play? Clearance on a thrust bearing, I suppose.

Is there a "plus-or-minus" limit called out?

RE: Lotus Twin Cam .120" oil orifice...pinging Rod;

TTF, I don't have a book in hand, but typically something like 0.005"-0.009" would work.  However, I really don't think that would account for the oil pressure problem.  At least not totally or to the extremes you posted.

Perhaps this chap should take his engine to a qualified mechanic that knows what to look for.  The bottom end of a Lotus is not much different than that of any English Ford (or Toyota clone, for than matter)!

Rod

RE: Lotus Twin Cam .120" oil orifice...pinging Rod;

Just to add another bit,
Ive taken vw inline 4s apart with 2.0mm of crank axial float, and they were perfect when running.

BG

RE: Lotus Twin Cam .120" oil orifice...pinging Rod;

(OP)
Rod, I think he put an indicator on the crank, and got .007" which is nuts-on your 'ball park' figures.

The owner apparently bought this engine, overhauled by a local "experienced Lotus Twin cam mechanic", but never run.

I have no idea where he's located.

Everyone is about 'out-of-bullets' on this deal.

RE: Lotus Twin Cam .120" oil orifice...pinging Rod;

TTF---Hey, what the heck is an experienced Lotus mechanic if it's not ME?  I said at the outset of this thread that in the beginning all those many years ago (That's kinda like 'once upon a time'---I should have been a novelist smile ) I did exactly as I suggest is his problem...I had no idea that there was such a thing as a 0.015" oversize shell available or that the folks at Ford UK would produce such an overbored main bearing bore.  Live and learn...I did.  Since that engine (around 1968 or so) I have seen this done on several engines of UK origin. No where else, though.  Like I said, ya just gotta love the British!

Bottom line---If it can happen to me, etc---sad

Rod

RE: Lotus Twin Cam .120" oil orifice...pinging Rod;

Rod

Being an experienced air cooled VW boxer engine guy, I can absolutely verify that over boreing the main bearing bores in the crankcase is std operating procedure on the VWs when overhauling as the bearing shells inevitably pound into the aluminium or magnesium crankcase and lose bearing crush.

Regards
Pat
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RE: Lotus Twin Cam .120" oil orifice...pinging Rod;

Yes, Pat.  I know about the bug engines although I prefer the wobbled out mag cases as 'campfire fuel'.  What I meant was overbored engines from the OEM and not from a rebuild scenario.  
Of course, at the time I learned about it (the hard way, of course), in my 'group', "VW" was used in the pejorative mostly.  I love ya, babe...I'm just not a bug person!  winky smile

Rod

RE: Lotus Twin Cam .120" oil orifice...pinging Rod;

No problems Rod.You love em or hate em, mostly for the same reasons. They served me well, but then again I mostly barrack for the underdog and loved the ummm shall we call it the surprise effect when the old beat up Beetle pulled into the overtaking lane up a steep mountain road and blasted past a big V8 already doing his best.

Regards
Pat
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RE: Lotus Twin Cam .120" oil orifice...pinging Rod;

(OP)
First off, thanks to all for the help & suggestions.

Here's the cut'n'paste from the long suffering Lotus Europa Twin Cam operator:

"I finally got the engine installed, and on start-up, the oil pressure is
60PSI.  The problem was that the oil pickup tube was too close to the bottom
of the pan, which "strangled" the oil pump.  I cut off 3/8" and now I have
great oil pressure."

Apparently someone suggested a wad of modeling clay under the oil pick up screen when dry fitting the pan, and then measuring the clearance!

"All's well that ends well"

RE: Lotus Twin Cam .120" oil orifice...pinging Rod;

(OP)
A follow up to my previous post, by another interested party:

 I'm curious, and you may have already told us this way back somewhere .

#1 Is this engine based on a 711m or 771m "tall" block ?

#2 would it be "does it have a Lotus or Kent/Cortina  pan on it ?"

I fear light is dawning on Marble head over here ...

RE: Lotus Twin Cam .120" oil orifice...pinging Rod;

Early twincams had pans with rope seals.  Four bolt flywheel flange on the crank, small main caps and, thread in oil pickup. 105E and truck "L" blocks were common.  Later engines used a variant of the Kent with a pressed in pickup, big maincaps, neoprene rear seal with a six bolt crank flange.  Both are "low" blocks in stock form.  It is, however, quite easy to use the 116E block, the Kent Cortina/Pinto 1600 block for a big displacement twincam...any where from 1700 to 1900 with almost no real added expense aside a decent forged or billet crank and a good set of Carillo/Cosworth/whatever connecting rods (I use a set of L18 Nissan rods).  I don't cut the block but rather make a spacer for the front cover, a couple added links in the timing chain and a relocated chain tensioner.  You cannot tell the difference with a bit of camouflage paint...clown

For intent and purpose, save the rear seal, both pans are identical.

Rod

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