Restoring a '71 Sprint

[PhilJohn]

Hi everyone, I'm a bit new to this site, but have been amazed at the depth of knowledge and general helpfulness from the posts I've been reading.

I wondered if you would be interested to hear about an Elan Sprint I am in the process of restoring back to its former glory? I bought the car in complete and original condition nearly 2 years ago and have been slowly and painstakingly dismantling it ready for complete renovation. At present, my car looks more like an Airfix kit, rather than one of the worlds all time great sports cars!

My Sprint is a 1971 drop head finished in Gold Leaf Team Lotus colours. When I was a kid I loved the Lotus F1 cars that raced in those colours, so I'm looking forward to getting back to its original paint finish; when I bought it, it had original paint, but had just faded badly over the years. Also, the car had been in storage for about 10 years and although complete, was in fairly poor, but original condition. I was lucky with a number of other things too; my car had a galvenised replacement chassis back in the late '80s, which has held up reall well, so only minor renovation required. Also, the engine was 'blue printed' by Twin Cam Techniques at some point. The block is painted blue and the engine carries a metal plaque to this effect. I have no idea what this means, but a very helpful guy called Kim from LDC said this was good. I have an absolute mountain to climb to get it finished, but it's going to be stunning when it's done!

Would you believe I've never actually been out in one of these cars yet, as my Lotus experience to date has been all M100 Elan!! I'm sure it will live up to all the accolades and praise though! I plan to do some sensible mods to improve the enjoyment and usability of the car, without detracting from the original, ie an alternator in place of the dynamo; Spyder tubular front wish bones; a larger radiator to aid summer cooling. I was really interested to read the posts on the TTR/Susan Miller drive shaft conversion. I really wanted to do that, but feared I would be burned at the stake!

Any thoughts or helpful suggestions would be much appreciated. If there is any interest, I will post some photos of the project and send regular updates - which might help me keep the project on track!

I live in Tamworth near Birmingham, so if you're passing, you're welcome to come and view the car/give me encouragement/lend a hand.

Many thanks for all the help and advice I've recieved from this site so far and I'm sure going to be needing your help in the future.
Phil

[GrUmPyBoDgEr]

Hi Phil,

all the best with your project & welcome.
Tamworth is nice & central, there are a few Elan.ne(u)tters not too far away from you.
A few years ago I worked at BMW Hams Hall just outside of Coleshill; just down the road from you.
As far as the drive shaft conversion is concerned; I'd heard so many sob stories about how difficult it is to replace donuts that it became top of the list in my restoration.
Fit & forget, so to say.
Read more in the Forum about poor rubber quality etc.
Your engine sounds interesting, Blue printing is an odd description, I thought that was only done to engines in one make catagories to get maximum performance within the scope of manufacturer's production tolerances.
Let us know more when you find out more about it

Cheers
John

[jimj]

"Blueprinting" is when stuff like the old carbon paper, used in old invoice books, is sandwiched between the manifold and block, for example. When removed, the blue markings left show where there is an overlap between the flange and the block which would slow gas flow. Careful filing away the blued areas to give an exact smooth flow through the joint is THE most cost effective way of improving performance.
Jim

[bcmc33]

Phil,

I've sent you a pm. I will explain exactly what blueprinting is when I see you.

[john.p.clegg]

And I always thought that "blueprinting" was "fettling" the engine back from production tolerences to how it was supposed to be on the drawing (blueprint)

John

[rocket]

I,m with John on this one..


Ian.

[GrUmPyBoDgEr]

Jim & John,

back in the "Formula Ford" days when they were using production cross flow engines the tuners used to blue print the engines.
The process was to utilise the maximum or minimum production drawing tolerances on all vital components in order to achieve the maximum performance from what still could be called a "production specification" engine.
This could also include the the port matching that you mention Jim, but only to the extent that the parts stayed within drawing tolerances.
I remember that "blue printing" those engines was a painstaking & very expensive process; more so than producing a full race engine.
Unless you are competing in a "one make" formula where the regulations are strictly enforced "blue printing" is not the way to go to get improved performance; too costly & relatively ineffective.
Dunnell Engines do a "blue printing" job on "Zetec" engines which they supply to all competitors in the competition class (which I can't remember, Westfield I think).
Those engines are bench run & provided with a test sheet & are "sealed"prior to delivery.
Comparitively speaking the amount of work needed to be done on a "Zetec" is far less than was required on "cross flow" engines, due to the much improved manufacturing methods used today.

Is that your take on it Brian?

Cheers
John

[bcmc33]

John,

Yes I agree in principle.

The word Blueprint is an americanism derived from the American standard of making copies of technical drawings onto coated paper that produced white detailing on a blue background. (In the UK it was blue detailing on a white background.)

The original idea of blueprinting was an attempt to eliminate balance problems that affected competition engines in the early days of automotive engineering as we know it today. And they did this by getting all engine components as near to nominal specification as possible, as this would then result in a perfectly balanced engine.
This was a relatively easy thing for OEMs to do by selecting parts from mass production quantities. When this was not possible parts were specially made from pre-machined components to nominal specifications.
However, history shows us that using components to nominal spec does not necessarliy make a perfect engine, and is inherently very expensive.

My thoughts have gone to trying to establish when the first balancing machines became available for rotating engine parts. Perhaps, John, you could research this with Schenck?

Today engine builders have their own ideas on what components should be on top, nominal or bottom limits of the tolerance range to make their perfect engine, and they won't advertise their secrets on any forum. But what I am sure is, consistent for all competition engine builders, is that matching components should be dimensionally the same within the tolerance range, and to that end, I?m sure, better balance results are achieved.

One thing that has always puzzled me regarding the blueprinted engines ? how did they truly blueprint a crankshaft in the days before CNC machines were available?

As you point out, John, modern engines are built to standards well beyond the wildest dreams of our abilities in the 50?s, 60?s and 70?s, and the work needed to achieve the original blueprinting objectives will be significantly less.

[PhilJohn]

My sincere thanks to everyone who has PM'd me about the project. Thanks especially to Andy who identified Twincam Techniques as being run by Dave Ingrams before he went over to the 'good ol USA' and sold his business. Heaven alone knows whats inside this unit, but the information on blueprinting is very interesting. I will post some photos as soon as I can and I thank you all once again for the enthusiasm expressed. Phil

[bill308]

My own recollection of blueprinting an engine was really an optimization process, much as D.J. Pelly described. Balance, clearances, and casting defects could be worked to eliminate "defects", for the purpose of maximizing performance and or reliability. So, port buggers, including interface matching, bearing and piston clearances, and timimg events could be optimized for the intended purpose unless prohibited by class rules. The basic guideline was one needed to stay within the production tolerences.

Bill

[GrUmPyBoDgEr]

The original term "Blueprint" does indeed refer to the copies of drawings.
During my school holidays I once worked for a drawing office supply firm in Bristol; my job was to make Blueprints from drawings brought in by various companies. The process used Ammonia & it really was a pungent smell.
My reward was being able to afford some very nice Thornton drawing instruments at cost price
Nice for a young lad who was hoping one day to become a Draftsman.
Later printing processes eliminated the Ammonia & the copies I became accustomed to in my job were black lines on a light grey background. Later to be replaced by microfilm & now of course CAD.

On the old Formula Ford engines in order to obtain maximum cylinder capacity they could "re-stroke" the crank.
That entailed re-grinding the big end journals at maximum centre line distance (drawing spec.). This resulted in needing to use a smaller bearing shell, which also had to be within drawing spec. i.e. -.010; -.020 etc.
Cranks had to be sortd & selected selected for being suitable for "re-stroking".
This sort of practice was applied to all vital components e.g. camshaft re-grinds etc.

Cheers
John

[jimj]

Yes, I stand corrected. blueprinting (according to Mr. Google and he knows everything) is building a STANDARD engine to optimum original specifications. I`m sure that carbon paper was/is used for port matching though, and I`ve heard it referred to as blueprinting.
On the subject of driveshafts; I fitted Mick Miller shafts about 5,000 miles ago and have used the car, particularly, on classic rallies where the driving tests involve full bore starts, stop astrides etc. I did not replace the standard diff. mounts with TTR ones and have had no problems. Perhaps Pete finds it much hillier in Wilmslow than here in the Peak District !!
Jim

[john.p.clegg]

"The basic guideline was one needed to stay within the production tolerences."

Bill


Bill

Production tolerences or Design tolerences?

John

[atthelimit]

Hi Phil

I see you now have had much information on blue printing and essentially it was as already described, matching tolerances and porting etc, often acheived by selecting parts form a whole range available to produced perfectly matched (or as near as possible) dimensions, weights and tolerances etc. So matching pistons, rods etc that sort of thing. Extremely time consuming and labour intensive and as said elsewhere with improved tolerances and machining methods of today, newer type engines really don't benefit that much anyway. However, on xflows and twinks etc in a racing series where modifications were banned this was one way of extracting power or making sure the power produced was at the maximum possible whilst staying within the rules.

That said, I beleive your car to be a road car and as such it would not seem to be worthwhile doing this when you are not constrained by racing regulations. It is more likely to have been modified and when you lift the head you may find you have hotter cams and larger valves etc.

Twincam Techniques enjoyed a very good reputation for building/modifying engines, Tony sold the business when he moved to the states and whilst the new owners carried on for about two years I believe they went bust, I think in those years the quality and work may have been different.

Tony Ingram is still in business in the states as GB Components
G B Components Incorporated
404 Por La Mar Dr
Santa Barbara, CA 93103
Phone
(805) 965-6169

They restore and look after racing car preparation, sell parts and they still build many twincams, mainly for racing, and his reputation is very very good.

I know you were trying to get in touch with him did you manage it?
He still sells competition and upgrade Lotus parts in the UK through Ebay.


Best wishes, and good luck with the restoration.


Kim

[bcmc33]

Stop it John (my friend), you're being very naughty, but I'll join you as I can see where you?re coming from.

In my general experience during the 60's & 70's design tolerances were double the production tolerances on the basis that design engineers never trusted us production/manufacturing engineers because they believed we always took twice what they allowed. This changed during the 80's & 90's when production and manufacturing disciplines improved dramatically in response to the Japanese threats. I guess the benefits can be seen in modern engines that can rev up to 8k with ease and 9k with only minor changes.

And for the record, ?engineers blue? has nothing to do with ?Blueprinting?. That is simply known as "bluing" and a standard method of working for fitters and toolmakers worldwide.