Miura workshop, technical details

It seemed appropriate to start a thread geared more to the actual owner, mechanic people who spend time with the actual vehicles. My own focus is the Miura, but the technical issues extend to most of the 2 valve V12 of the same era 64-78? 350, 400, Islero, Espada, Jarama, Countach

I am investigating a first over bore for a Miura engine and piston purchase and want to ask for any recent experience with Lamborghini piston purchases. Standard bore is 82mm and first over appears to be 82.5mm.
USA companies with past production history of Lamborghini pistons seem to be JE, CP, BRL, but maybe many others. Anyone have pertinent details to share?
thanks
Craig
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I've used oversize JE pistons, a good product. Rings came from Deves, if I recall correctly they were also the size for a Chevrolet Chevette.
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Thanks Tim, Yes, i hear JE pistons for Lamborghini several times over the last 10 years or so. Are there more details you would have around this particular application? Size and style of rings perhaps, maybe the cylinder finish recommended, a job number for this piston buy, and all the things you would be concerned about during a rebore. Piston weight, wrist pin design, additional grooving, skirt type and length. Do you have a copy of the paperwork from JE? That would answer quite a bit, realizing the price may be out of date.
Any help is great!
Craig

 

I'll see what I can find but it is quite a while ago.

 

The Miura parts manual has several, fatal mistakes and the camshaft illustration from the early series Miura is no exception. I am pretty sure this mistake carried thru to all Miura.

All Lamborghini camshafts are stamped on the flange end with alpha numeric pertinent information at the time of manufacture. Has anyone recorded these data off of a Lamborghini camshaft set that they can share?

This particular drawing has an owner note (from 1978) applied to the exhaust cam which implies to me that an 07711 cam is the more current # (from 1978) to replace the MD-03728. The drawing also mistakenly associates the Marelli drive with the exhaust cam.
Anyone have Lamborghini camshaft experience? 350? 400? Espada? Jarama? Anyone purchase a new vintage application Lamborghini camshaft lately?
Craig
ps-the mistake is the intake cams are number swapped 2840/2844...i am not sure if the other Lambos share this mistake on tha parts list.
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a great page for cam links- http://powermechanics.com/camlinks.html

 

I'd love to join in but unfortunately our last two motors were outsourced and I don't have specifics on pistons (I believe JE), etc. Next one (400gt 2+2) will hopefully be all mine...

But I'll keep watching, love the tech stuff.

 

Why 2 different intake cams, and 2 different exhaust cams - do they rotate counter to each other?

 

Hi, what number 400GT 2+2? Thanks!

Fred

 

My pistions/rods (bottom pix)

http://www.400gt.com/photos/engine_rebuild/EngRebuild.htm

I was advised "do not rebore" if you don't have to. That rebuild was 1983, car's still running like a champ, smooth as silt (ooops...I mean silk)

Cheers,

Fred

ps: more pix:

http://www.400gt.com/photos/engine_rebuild/EngRebuild2.htm

 

It is simple mechanical fit/design, the cylinders are staggered, therefore the cam lobes are staggered....yet all the cams need to be driven, on the flange end, in the same plane. So front/rear cams are different..yet the same. Even my drawing will show long and short "journals" if you look close enough, and this is due to the cylinder position.

 

Hi Fred, Do you recall the dimensions for pistons/cylinders that made it sensible to continue to run the OEM pistons?
thanks
Craig

 

i got motivated to establish a better thought pattern for all of the engine related repairs needing to be accomplished prior to engine assembly. Maybe other have already done this and can share their thoughts. A thought with me this morning is .....
If you purchase pistons prior to having a engine bored/honed, so you can achieve best fit.........
why would you not purchase, install and size engine/rod journal bearings prior to having crank repairs done?
any thoughts?

My list today for crankshaft repairs, it seems you would want

1) checked for cracks thru some technical methods, maybe several
2) run out true to some spec TBD
3) Repair method for journals well proven and experienced.
4) correct size diameter journals for bearing set
5) journal fillet radius within some spec TBD
6) thrust bearing surface within some spec TBD
7) correct oil galley relief on all journals
8) 12 oil galley plugs removed for inspection and final cleaning prior to assembly
9) balanced (configuration?)to some spec TBD
10) nitrided or other coatings

This has got to be a naive list from me as i have given it just a small amount of thought.
thanks for any help
Craig
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The cylinders are offset from one bank to the other and thus the cam lobes are in different places along the camshaft. The head gaskets are not interchangeable either.

 

That pretty much covers it.

You would never want to grind the crankshaft until you actually had bearings in your hand.

 

I got my first up close look at a window winder for an early Miura - looks to be far superior to the later all-cable system that I'm grappling with now. it looked to be so well conceived and easy to fine-tune that I first thought it was a clever retrofit of a 3rd party winder. Anyone know if these were home-grown or adapted 3rd party products (and if they can be found)?

 

whew doggies! I can look through my old receipts and stuff and see if there is any info there. Unlikely, but I always love a challenge

(don't hold your breath)

Fred

 

Thomas, please post some photos of which winders you speak. Or maybe others have such photos?
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If you purchase pistons prior to having a engine bored/honed, so you can achieve best fit.........
Why would you not purchase, install and size engine main and rod journal bearings prior to having crank repairs done? any thoughts?

What technique and exact measurement equipment would a professional shop use to accomplish the task and how would you document the results? And if you have been involved in this task, can you post your last document for this new bearing size check? What type document follows the crank to the repair shop?

Since your shop bore measurement instruments and crank repair shop journal measure instruments will not match, how are you addressing this?

Craig

 

You have posed this same question in two different forums. The techniques used for building an engine aren't unique to Lamborghini (or Ferrari).

Are you expecting different responses?

The process of returning a worn/damaged engine to like new specs is documented in numerous automotive textbooks.

 

Thanks guys. I didn't factor the stagger into the equation.

Craig,
I think you're overthinking things a bit - experienced shops have simple methods for measurement and communication with sublet shops. Unfortunately, mistakes can happen no matter how well documented things are.

In the case of fitting pistons vs. fitting bearings, pistons are much more complicated beasts and its best to fit each piston to its respective bore before final honing. Bearings and their journal surfaces are simpler. Most everyday engines have their cranks cut to spec, are assembled, and clearances checked with plastigage. Clearances that are slightly out of spec can corrected by swapping bearings to even out the numbers, trying another set or brand, etc.

However, with high performance motors, it is advisable to mock up each bearing in the rod or main cap, torque, measure, and then grind accordingly.This allows not only a more exact clearance, but also allows for optimizing the 'looseness' or 'tightness' of your fit.

Does that help?

 

Fred- #0925...I think we've had pics on here somewhere. She's more or less a nice original driver with a repaint. Engine is starting to lose some oil through the rings I believe. Leakdown test is next on the list.

 

Tim, Yes similar singular subject posting. Some would agree BB Chevy is same as Lamborghini/Ferrari, others might not. Most definately expecting different answers, bigger gene pool. I am not so sure the process is documented...it is all in the details!

 

Some aspects are similar to a "BB Chevy", others relate to similar aluminum block/overhead cam motors. The technology dates from the 60s and was "state of the art" then but is "old school" today.

The specific operations required during a rebuild are the result of careful measurements taken during inspection. It is not uncommon for an aluminum block to need a "line bore" to make it straight again however it isn't always necessary.

One of the biggest differences between rebuilding a vintage Lamborghini 12 banger and a more "mass-market" engine is the cost and limited availability of some basic parts. If your Chevy has damaged cylinder heads, they would quickly be replaced with new (probably improved as well). New heads for a Miura or Countach or Ferrari Daytona are pretty rare items (not ruling out one left on a dusty shelf somewhere). Extensive repairs are frequently made to the original equipment. In many cases a combination of art and science.

Some items such as a crankshaft may need to be manufactured by companies like Moldex if the original can't be reused.

 

Craig it is best to have the bearings in hand because with Lamborghini you don't always know what is and is not available. Lamborghini unlike other manufactures does not always follow the normal standards that other manufactures seem to follow.

Take for example the bearings that are available for the 5 liter, 2-valve Countach. They are available in, standard size, first oversized and second oversized. The problem being is if one would assume that the first oversized set of bearings was 0.010" oversized like so many other manufactures typically produce they would be WRONG. As the first oversized bearing set is in fact 0.005" oversized and the second oversized bearing set is 0.010" oversized.

This is very good information to have before grinding the crankshaft. Maybe you can clean the crank up by taking 0.005" off from the journal diameters or maybe you can't. Or maybe if you assume that the first oversized bearing set is 0.010" oversized and you install them foolishly without checking them you have an engine without any oil pressure.

The later unfortunately happened to me at the hands of a self proclaimed Lamborghini expert by the name of Robert Ball owner of Supercars International Inc. Well this not only resulted in my Countach engine having no oil pressure. It also resulted in a lawsuit against Robert Ball and Supercars International Inc. This then led to eventual filing for bankruptcy protection by Robert Ball that took place exactly one year ago to the date.

Sincerely Vic