Lotus Elan

New Owner '69 S4 - Unravelling the Mystery

PostPost by: rgh0 » Tue Nov 11, 2014 10:11 pm

This sure generated a lot of interest between when I went to bed and this morning

It appears most of the questions have been answered as far as I can see.

The engine appears to a tall block conversion using a 2737 block and a spacer plate. The block appears to not have been substantially decked and to use special pistons (which I prefer) rather than the approach of taking about 6mm off the block and using the standard twin cam pistons and a thinner spacer plate

You may want to look at the engines mounts as they may have needed to be modified to fit the tall block in so it did not hit the hood (bonnet).

Should be possible to check the bore to determine what its bored to and if the 75mm is really 0.75mm and means a 30 thou over bore. if its not that then I don't know what the 75mm means

The fitting of sprint cams and the bigger 1.625 inch diameter inlet valves introduced with the Elan Sprint and a tubular exhaust and removal of emissions crossover pipes would all be expected modifications to an engine if you were rebuilding it with a tall block bottom end sometime in the 80's. The distributor should have been modified to remove the emission required ignition retard and to change the advance curve to the non emission Stromberg engine curve also. A longer swing arm for adjusting the timing chain tension is now available for the tall block conversion which was not available I don't think back in the 80's and you may want to source one of those. Using the standard arm means the adjuster piston in the timing cover does not line up correctly with the arm located in the pivot in the head and the adjusting screw needs to go in much further limiting your ability to adjust for future wear.

Overall it looks like a well done conversion and should produce a healthy 130 hp and very tractable engine with great torque.

cheers
Rohan
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PostPost by: seniorchristo » Tue Nov 11, 2014 11:06 pm

Hi John,

My situation is very similar to yours in that I recently bought an Elan S3 from California which also has a "tall" block. Mine is a 711B. After my initial disappointment of finding my car didn't have the original engine, I discovered many interesting facts about the tall block. Most have already been discussed here but mine has a similar spacer block and headers. I'm not sure about my cams or pistons but from service records I know the sump has a pivoting oil pickup similar to that supplied by Dave Bean. I am anxious to know what's inside but the car is running strong so I don't want to rip it apart unnecessarily.
Getting to your question of oil leaks, I have similar issues. After researching oil leaks through the Lotuselan.net archives, I thought high oil pressure might be a contributor. My car has 60 lbs. hot while standard pressure is in the order of 45 lbs. Just this week I discussed this with Ken Gray at Dave Bean and he tells me 60 lbs. is pretty much standard for the SE engine and was not the cause of my leaks. Most likely problem areas are the front timing cover, valve cover gasket, breather tube and rear crank seal. Having a front cover spacer complicates the problem and much is dependent on how all those parts fit together. Check the archives as there is good information on how these parts should align and what gaskets and sealers should be used. :)
Later,
Chris
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PostPost by: rgh0 » Tue Nov 11, 2014 11:59 pm

Hi Chris
A 60 psi oil pressure with a high pressure pump fitted is a "common" modification but it is not "standard" as the standard oil pressure relief valve was set at 40 psi for all twin cam engines. However the higher oil pressure does not normally contribute to oil leaks which typically come from low pressure areas where there are joins in the engine components (sump, front cover, back plate etc) as you observe and not from the high pressure oil galleries

cheers
Rohan
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PostPost by: jbeach » Wed Nov 12, 2014 12:08 am

Thanks everyone!

My head is spinning at this new information. I contacted the previous owner (a great guy, by the way) and he said although he owned the car for 25 years and changed his own oil, he had no idea what a "tall block" was or that this car had one.

More importantly, because my car is getting a valve job right now, I need to alert my mechanic of this change so he'll know not to base his reassembly, timing adjustments, etc., on the notion this is a standard engine.

Rohan, thanks so much for the information on the cam adjuster. My mechanic is already in contact with Ken Gray, so I'll have him speak to Ken about this and be certain to install the new part while he's in there.

I'm also interested to read your comment on the pistons, etc. To clarify, which of the two scenarios you mention do you believe I have? The one you prefer, or the other one?

As a final point, should I have my mechanic remove the spacer and install a new gasket between the top of the timing cover and spacer, or leave that be? Is there even a gasket in there?

Are there any other differences caused by this change I need to know about? As this new knowledge begins to sink in, I'm becoming very pleased to learn my engine has the Kent block, but I'm going to have to study up on how this changes things.

Thanks again for your help!

John
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PostPost by: jbeach » Wed Nov 12, 2014 12:11 am

Oh, and can I safely take this engine to 9,000 RPMs like Jay Leno with his Kent conversion '69 S4?

Don't worry, I'm kidding!

John
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PostPost by: rgh0 » Wed Nov 12, 2014 12:34 am

Hi John
Judging by the thickness of your spacer which looks like about 10 to 12 mm I believe you have a un-decked tall block. To then get the right compression ratio you need to use a special piston with an approximately 6mm higher compression height to bring the piston top up to the top of the undecked block. This is what you appear to have.

Normally the standard cork gasket is installed top and bottom on the spacer but you need to ensure you do not have to much crush on the gaskets so they squeeze out and you have oil leaks. Using Loctite / Permatex Aviation Gasket Cement No3 on the cork gaskets help hold them in place and not squeeze out. When you take the head off as you have you should replace both these gaskets

If you are removing the front cover also and replacing the timing chain you will need to check how many links you have in the timing chain and ensure you get the correct length chain to suit your undecked tall block. Ken at Dave Bean should be able to help on that also.

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Rohan
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PostPost by: gjz30075 » Wed Nov 12, 2014 9:38 am

Hi John, welcome to the forum. Phil owns the Pistachio green Elan you see on the home page here. A fantastic looking car. He knows his stuff, too.

Greg Z
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PostPost by: oldchieft » Wed Nov 12, 2014 6:57 pm

rgh0 wrote: A longer swing arm for adjusting the timing chain tension is now available for the tall block conversion which was not available I don't think back in the 80's and you may want to source one of those. Using the standard arm means the adjuster piston in the timing cover does not line up correctly with the arm located in the pivot in the head and the adjusting screw needs to go in much further limiting your ability to adjust for future wear.


Question for Rohan, about the longer swing arm.

Is this longer between the sprocket and the pivot point centres?

Or is it longer between the sprocket centre and the pad were the plunger acts?

I was under the impression that the was just a pad welded to the standard part to restore the adjustment range.

What are the options and who makes them?

Jon the Chief
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PostPost by: saildrive2001 » Wed Nov 12, 2014 9:39 pm

The cams are the SE spec cams for the Stromberg engine and they were also used for the Sprint. You don't know whether the cams have been reground so you really need to check them for the lift & duration.
Keith Marshall
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PostPost by: jbeach » Wed Nov 12, 2014 9:43 pm

Hi Greg. It's great to hear from you.

Don't worry, I noticed Phil is one of the experts - he was the first to notice the spacer and alert me to the possibility I have a "tall block."

I'm fortunate to be a part of lotuselan.net. Its' a great resource and the members (you included!) are extremely knowledgeable and willing to help.

I'll be posting "Unraveling the Mystery, Part 2" shortly.

Best,

John
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PostPost by: jbeach » Wed Nov 12, 2014 9:44 pm

Thanks, Keith - very good advice. I have a call into my mechanic and plan to look into this shortly.
Best,
John
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PostPost by: abstamaria » Thu Nov 13, 2014 12:15 am

John, a belated welcome. We have the same year Elan, but I bought mine in 1977! With all the work you are doing, I wonder if you should consider finding a short block, preferably with the "L" and switch to a Weber head. That is a potentially expensive promotion, but here may be complete engines got sale somewhere.

Good luck, and best regards,

Andy
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PostPost by: jbeach » Mon Nov 17, 2014 11:16 pm

Thanks for the welcome, Andy.

I appreciate your suggestion. My guy is almost done with the valve job. He says everything is looking good and the car should run very strongly once he reinstalls the head and associated gaskets, sets timing, adjusts, valves, etc.

I'm actually very pleased to have the tall block on this car. Before the current work this engine pulled strongly all the way to (and a hair past) the 6,500 RPM red line. If the valve job causes even an incremental improvement, I don't believe I'll have any complaints about the tall block or desire to change back to the standard block.

I MAY look at switching to a Weber head at some point, but that's at the very bottom of my current list of projects.

I'm already enjoying the roller coaster ride of Elan ownership. This Forum is a great addition to that.

Best,

John
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PostPost by: Famous Frank » Tue Nov 18, 2014 1:58 am

John,

Congrats on your new Elan!!! Hopefully you will have years of enjoyment as I have. I haven't been without a Lotus of some sort since 1973. I like lots of different cars, but I love Lotuses.

Your notes show someone spent a bunch of time and money in the past. And spent it in a sensible manner. Your Tubular Headers are larger in diameter than standard Lotus Tubular headers. And they appear to be stainless too. If you have extra cash, consider getting them Jet Hot coated or something similar to spice up the engine compartment a little.

The tall block conversion is a good one. As for the oil leaks, there are not many Twin Cams that don't leak. What you are after is to eliminate MAJOR leaks. Small seepage leaks are nearly always bound to appear. It's and old joke but if your Twin Cam doesn't leak, it has no oil in it!!!

Weber Head vs Stromberg Head, .......there is a conversation that can go on forever. Webers are definitely sexier looking but for a street driven car, Strombergs can perform as good. Especially in engines under 150 HP. If you want the Strombergs to look good, consider using the European intake manifold extensions with the balance tube. These work very well and eliminate the blocked cross over ports that are so unsightly when blocked off.

To help with the oil leaks, consider having the valve cover fitted with a secondary breather tube to releave some of the internal pressure.

One more thought, Lotus cylinder heads are expensive to replace. Be damn sure your engine builder REALLY knows what he is doing. One mistake can be disastrous. I'm not trying to worry you but it's a fact.

Another thing. You may be leaving a bunch of free horsepower on the table if the cams are not degreed. You can tell if someone degreed them in the past by looking to see if there are offset dowels locating the cam gears on the camshafts. Many, many people have assembled their engines and timed the cams by lining up the marks on the cam. The engine will run okay this way but rarely puts out the horsepower it's capable of. Example: Many years ago I bought an Elan whose engine was rebuilt with lots of expensive parts. When I purchased the car, the engine looked terrific. Started easily, idled okay, but just didn't have the get up and go I thought it should have had. It had head work, higher compression, high performance cams, a dry sump, etc. I removed the engine and put it on an engine dyno at PHP Race Engines in Wauconda, Illinois. It was only putting out 92 HP. We changed the distributor curve. Engine went up to 97 HP. We degreed the cams, horsepower went up to 117. We changed the chokes in the Weber carbs, horsepower went to 125. Finally jetting changes finally moved the horsepower to 137. What a difference! And never changed one part.

Finally, consider paying for and installing ARP Rod Bolts. Dave Bean probably has them. Stock Lotus Rod Bolts will stretch over time and some day when you are spinning it up to the 6500 rpm and a rod lets go, you may never know why. I've disassembled engines where the rod torque was as little as 10 lb feet to remove the bolts. This is because they have stretched!

And finally, finally, if your car doesn't have an Alternator, install one of the mini ones available from Dave Bean. 90 % of your Lucas electrical issues will disappear!

And finally, finally, finally, if your car doesn't have CV joints in place of the donuts on the rear axles, ..........well, those donuts have to go too. Gosh I love spending someones money!!!

Enjoy the ride,
Frank
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PostPost by: Famous Frank » Tue Nov 18, 2014 2:08 am

Oh, I forgot to post a pic or two. I love pics!
Attachments
stock headers bright silver.JPG and
Alternator side.jpg and
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