TC block castings

[Exlimey]

Watching the TC for sale on BAT,the latest comment from the seller in part says, “has a rare 701M6015 casting,rare and special “ Is this a true fact, my car has the same and I assumed ( dangerous) that they all had the same.

[jbcollier]

Well, hard to say.  Some say "Wow!"  Some say, "Whatever."  Google the number and you'll find lots of discussion with no firm conclusion.

[BDA]

I found some information in Dave Bean's English Ford Racer's Catalog (I advise getting all of Dave's catalogs for the information and insights alone. There is a lot of good information in them!). It wouldn't make a lot of sense to just discuss particulars of that block without comparing them to others - and to be candid, I'm not capable of judging most of those particulars. According to the "comments" section on the chart of all the Kent blocks, the 701M were cast specially for Lotus and had a thicker cylinder wall and the letter, 'L' on the left hand side. Dave did not say they were rare, but if they were a Lotus-only block, that would most likely be true. That probably implies that it was the original block. Having thicker cylinder wall would increase rigidity and/or allow for more aggressive/safer over-boring. For that reason, they would probably be desirable for building a racing motor.

[Bainford]

It is my understanding that all Twin Cams fitted to Europas had the 701M block with the L cast in. Someone please correct me if this isn’t true.
Mine has it.

[literarymadness]

Rare is a relative term. Ford built 2.8 million Cortinas for the UK. How many of them had the same type of engine block but not as beefed up as the Lotus version?  It would make the Lotus version by comparison seem relatively rare. And not all L blocks were created equal. They were subdivided into LB, LA, and LAA based on cylinder wall thickness. Most Twin cams are LB while 10% have the slightly more heavy duty LA block.  LAA blocks went to Lotus tuners only.

[4129R]

I took a block to a very specialist engine builder, Scholar Engines in Suffolk, to have new standard sized liners put in the corroded bores, and the machinist who was vastly experienced told me it was a late block with the larger main bearing caps which give less problems than the earlier blocks.

He knew about the Zenith head to Weber head conversions by Omnitech in the USA, so he knew his stuff.

I will take him my Zenith heads to see what it would cost to convert them to Weber heads, as all the 2nd hand Weber heads I have bought have been sold for a reason, they need a lot of work.

[literarymadness]

The earlier Elan Twin Cams (S1-S3...I don't about the S4) do not have the 701M block. Lotus made the change to 701M block around late 1970/71. All Europa TC and Specials, and Sprint Elans, that I know of have the 701M block. Here is a link for some of the other blocks used in Twin Cams.
https://www.lotus-cortina.com/library/block/blocks.htm

[Exlimey]

Thanks for all that, it seems that ‘rare and special’ applies to all TC Europas. I also question the Lotus Cortina,just withdrawn from BAT (suspicious #’s) which said it’s engine was stroked to 1700cc, I didn’t think that could happen with a regular lotus block. That led me down another rabbit hole and I found my old lotus cortina was still registered ten years ago! It’s raining hard!!

[rjbaren]

I have a 73 TCS and the gentleman who rebuilt my engine, Barry Sales at PHP Racengines, bored it 1mm and then used a different steel forged crank (I think from a Ford 1600) and new pistons and said the engine is a now 1705 or 1710 that I can rev to 7000 rpm safely.  The block has an L cast into it and the serial number is S29955 if that means anything?

It was Stromberg head engine and I now have Mikuni carbs and electronic ignition.  Since it went on the dyno before and after the carb change, it makes 10 more HP with the Mikunis and the electronic ignition.

[literarymadness]

rjbaren: The S29955 ID number is the engine's individual serial number.  What are your dyno numbers? And are they at the wheel or at the crank? I would love to know both numbers (crank and RWH) if you have them. And what compression ratio are you running? On the Elan forum, most Twin Cam engines lose about 20-22% HP at the rear wheel.

[rjbaren]

I only have engine dyno numbers at the flywheel. 

HP topped  - 145.9 HP @ 6900 rpm with 111 lbs. Torque. 
The Torque topped out at 124.2 @ 4900 rpm with 115.9 HP.
The torque stayed flat from 4400 rpm @ 120.1 lbs. to 119 lbs. @ 6300 rpm. 
Between 4600 rpm and 6000 rpm it was mostly 122 lbs. and 123 lbs.
From 4400 rpm where there was 100 HP, it went up from there 2-3 HP every 100 additional rpm to 145.9 @ 6900 rpm.

[literarymadness]

rjbaren: Are you running High Compression? What is you cam profile?

[jbcollier]

Very impressive numbers!

[rjbaren]

I know they are performance ground cams and I believe they are the original cams reprofiled?  I don't know the compression ratio.  I could find out though and report back.

[rjbaren]

I called and got some info on the engine.  They are the original cams that were reprofiled.  The compression ratio is 10 to 1.  The rods are the stock 125E rods, and the bolts are ARP bolts.  The crank is from a formula ford 1600 and it is not forged but cast steel.  Barry calls the engine a 1700.