701M block bought new direct from Ford

[promotor]

I've managed to get my hands on a 701M block that has about 100 miles use on it and it's still on standard (although worn) 80.98mm bores.

The person I bought it off told me that the owner previous to him bought it new direct from Ford.

The only thing is that it doesn't have any stamps on the front face (ie LA, LAA, LBA etc) so I'm not sure of (if the info Miles Wilkins provides on block grading is gospel) what the max size it will take is?

The dilemma is i'm not sure if the standard sized block is likely to only go to 83.5mm (if that!!).

It has what look like Cosworth steel caps, and it also came with Cosworth crank, rods, and pistons. I'm quite happy to keep the internals and not use the block if likely to be no good.

I guess this means it's possible Lotus are the ones that graded the blocks and maybe sent back ones that they deemed no good after sonic-testing?

I appreciate this is slightly along the theme of previous topics but i've never seen any info on how Ford actually marked those blocks that Lotus didn't use.

[stevebroad]

A worn block with only 100 miles on it? Are you sure it is only 100 miles? With only those miles on it there should be no wear and the honing marks should still be visible. Hell, mine were with a couple of thousand on it.

This may of some use:

http://www.lotus-cortina.com/library/block/blocks.htm

[promotor]

Yes it sounds impossible but it ran a supercharger, and methanol (was in a drag car), which creates really bad bore wash as it thins the oil very quickly, so it had had a hard life!!

[types26/36]

I would have no qualms about boring it to 83.5, if it was in the Ford exchange scheme with a 81mm bore then the chances are that it was never even sent to Lotus so why should it have any LB etc. grading as I believe it was Lotus who graded their blocks.
I have never seen a pre Xflow or Xflow from a Cortina or Escort OHV with the LB etc. stamps.
You can of course have it ultrasonically tested if you want to spend some money and sleep better at night

[512BB]

Am I missing something here Al?

Why would you want to take it to 83.55 when it has not even been bored out to the first standard Lotus bore size of 82.55mm? They were supplied at 81 odd mm from Ford, and were then taken out to the Lotus size, but your block is still at the original Ford size.

Leslie

[promotor]

If the block is only capable of going to, for example, 82.55mm and no further then it's hardly worth using as a Lotus block and would need to be kept for use in a standard-ish pre xflow.
That's my question really - what is it that caused the blocks to be graded/rejected - I'm guessing because they weren't good enough to provide a reasonable service life!!

Seeing as some of the pre-xflow 120e blocks were no good beyond 82.55mm then it's feasible to question whether this block is actually useful in a Lotus engine.

[types26/36]

As far as I remember Ford only ever supplied oversize pistons up to +60 thou (for OHV engines)which brought it up to standard Lotus size, Lotus on the other hand only ever supplied one oversize of +15 thou for standard road cars (obviously non OE pistons are available in various sizes) but I believe the 701 block will easily take this although + 15 thou pistons are probably NLA.

[stevebroad]

Yes it sounds impossible but it ran a supercharger, and methanol (was in a drag car), which creates really bad bore wash as it thins the oil very quickly, so it had had a hard life!!

Ah, you hadn't mentioned that! In that case a 100 miles in a drag car is around 25 miles at full throttle plus burnouts, warming up, cooling down, etc. That would account for the wear. I would, however, suggest having the block checked as it has had a short but very hard life experiencing stresses it wasn't designed for.

[rgh0]

The dilemma is i'm not sure if the standard sized block is likely to only go to 83.5mm (if that!!).

I dont know who did the final boring and marked the blocks with LA, LB, LAA in the orginal production. Whether it was Ford or Lotus who took standard blocks off the line at some point and then continued the machining to the Lotus bore I dont think anyone knows. The thickness checks for the stamping I believe were spot checks using special calipers through the core holes. Certainly ultrasonic thickness checks would have been slow and expensive back then with the equipment avaiable and not suitable for a production line environment.

Almost all blocks will go to 83.5 mm. However you will often need to offset bore each cylinder individually to get the maximum wall thickness and avoid thin areas. The bores are never concentric with the cylinder castings as the cores always moved around when being assembled for casting. Ultrasonic testing and offset boring is the way to go to maximise the strength and life of a block if boring it for sleeving or for going out to 83.5 and beyond.

cheers
Rohan

[StressCraxx]

I've managed to get my hands on a 701M block that has about 100 miles use on it and it's still on standard (although worn) 80.98mm bores.

The person I bought it off told me that the owner previous to him bought it new direct from Ford.

The only thing is that it doesn't have any stamps on the front face (ie LA, LAA, LBA etc) so I'm not sure of (if the info Miles Wilkins provides on block grading is gospel) what the max size it will take is?

The dilemma is i'm not sure if the standard sized block is likely to only go to 83.5mm (if that!!).

It has what look like Cosworth steel caps, and it also came with Cosworth crank, rods, and pistons. I'm quite happy to keep the internals and not use the block if likely to be no good.

I guess this means it's possible Lotus are the ones that graded the blocks and maybe sent back ones that they deemed no good after sonic-testing?

I appreciate this is slightly along the theme of previous topics but i've never seen any info on how Ford actually marked those blocks that Lotus didn't use.

Your block is likely just fine, but the bores are worn. I would keep the steel caps with that block since they were line bored to that block. If you use them on another block, it will require line milling the cap bottoms, and line boring again, quite an expense. Blocks can be bored and sleeved back to stock for a cost. We do that as a matter of course in Formula Ford because used std bore blocks are unobtainium and new ones are expensive. The new sleeve materials such as nodular iron or nikasil have lower coefficients of friction than the Ford gray iron, so there is a performance advantage as well.

A good machine shop can inspect what you have, advise the best course of action and bore your block to the size you need. Find out what you can do, then buy the pistons that are suitable for your service.

Regards,
Dan

[elj221c]

If the block is only capable of going to, for example, 82.55mm and no further then it's hardly worth using as a Lotus block and would need to be kept for use in a standard-ish pre xflow.
Seeing as some of the pre-xflow 120e blocks were no good beyond 82.55mm then it's feasible to question whether this block is actually useful in a Lotus engine.

I'm with Leslie on this one. Unless you are going racing stick to the standard twin cam bore. My 701 also does not have the grading on it (it does have an L) and was on the standard Ford bore before I had it taken out to standard twin cam bore.

As pointed out, the blocks are pretty rare and staying standard should give you years of block re-boring in the future!

[bcmc33]

I bought a new 711M block and had it decked and bored to standard Twink on the basis that it potentially now has a 40 year lifespan.
However, FWIW, an engine builder friend bores new 701M blocks to 85mm for his racing customers. He also replaces the main bearing caps for his special steel ones.

[avro]

Hi Al

In all probability your block will bore to 83.5mm without any problem. With well over thirty years of machining Ford and Lotus cylinder blocks I have never yet had one fail at that bore size. This would include quite a number of blocks such as yours that did not pass the Lotus selection process and subsequently ended up within the Ford engine exchange scheme.

The 701M "L" blocks with an 81mm bore size were often to be found in old Cortinas and Corsairs and I had spent many a day visiting the breakers yards in the 1970s and early 80s buying up as many as I could find.
Boring them straight out to an oversize of 83.5mm in those days would not have been quite the dilemma that I face now. It didn't seem quite so wasteful then . Now when you need to bore to that size to get the full benefit of a 1600 cc class limit it does play on the conscience. What you need is not always available as you often have little choice these days. Good used blocks that you may want to use in an expensive race engine have become difficult to find.

Perhaps I've been lucky and I'm sure someone will say that they have experienced problems with non graded Lotus "L" blocks, but my feeling is that Lotus were perhaps overly cautious with their selection process.

When inspecting any Lotus block prior to machining I completely ignore all the casting numbers. I first remove all the coreplugs and visually check the gap between the bores within the water jacket. Measurements can be taken not just at those points but also from the rear face of the block to number 4 cylinder and from the front face through the waterpump aperture to number 1 cylinder. From this you can determine the wall thickness of the cylinder bores at those points . However don't assume that they are going to be evenly cast throughout their diameter and length. Looking from the top face through the triangular and round holes into the water jacket will also give a reasonable indication of the thickness of the cylinder walls, but beware as this may not be all that it appears. There can be quite a pronounced undercut on many blocks at a point about .500"thou (12.5 mm) from the top of the block down and this can leave the remaining length of the bore wall a good deal thinner. I like to see at minimum .120"thou (3mm) wall thickness. Although you may get away with a little less in places, be aware that a lot of old blocks suffer with localized corrosion.
I have a pair of long modified calipers that allow me to measure through the water jacket holes and down the adjacent bore and although quite crude they do seem to work quite well.


Regards

Nick

[promotor]

Thanks for all the responses!! I knew a 701M would get people chomping at the bit!

Sounds like I maybe made it confusing with my initial reference to an 83.5mm bore - I wasn't intending to go to a 83.5mm bore straight away - I'm in the camp of keep as many lives in the engine as possible - but was just querying whether the block would go beyond 82.55mm if it was a reject! There's no benefit to me to go to 83.5mm but there is a benefit to have the option of further bores beyond standard size should i need them!

I've also got an LA stamped 701M block and from my initial checks through the water pump impellor hole and checks through the core plug holes I can't measure any discernible difference between the two blocks. The idea of some custom long calipers is now on my mind so will have a look at making some of those!

I completely agree about ignoring casting numbers as I think they just identified WHICH mold they came out of as a way to identify problems with any warranty claims etc - if they found a number of blocks with "T31" stamped on the side were cracking in the same place it would be reasonable to expect it was down to the mold. The classic myth is always the higher the "T" number the thicker the bores - well I haven't seen any Lotus blocks with any other numbers than 1-4 (not saying there aren't any, just that I haven't got my hands on one yet!) so by that token all those Lotus blocks should be worse than all of the standard pre x flow blocks!

It perhaps also makes sense that when the "L" block appeared Lotus ended up getting the blocks from the molds 1-4 as a seperate production line. I believe the block I have has "T4" stamped on it so at least that's "normal".

The issue I have at the moment is finding a decent machine shop that can even entertain the idea of offset boring and being able to do ultra-sonic testing - if I want these service I have to travel a fair distance as I don't know of any decent places in the Sheffield/Chesterfield area of the UK.

Perhaps a separate thread/topic (and it could be a "sticky") with a list of decent machine shops and their location/services offered would be helpful to all members on here (if there isn't already such a thing on here?).