bulindg up a 711m block for an everyday twink

[tdafforn]

Hi guys,

I am just begining to rebuild a 711m 1600 block to replace the L block
on my twink..

The reason for this is that as some of you have seen, the engine leaks
oil like the Exon Valdese and shows all the signs of needing a rebore.

Rather than have the car of the road engineless I have got hold of a
711m engine (still with standard sized bores) which I am going to
convert.

My question is, does anyone have any recomendations for things to do
while rebuilding the bottom end.

How far should I bore the engine out?

What type of pistons should I use?

Are the standard con-rods OK to use?

Should I use uprated bolts for the mains and con-rods?

Which oil pump?

Where should I get it prepared?

etc

Any advice would be useful before I get into the heavy engineering bit

Just for information, the car is used as a daily drive and not as a
racer.

Cheers

Tim

[ElliottN]

Tim, I expect you'll get lots of input but IMHO....

Read the Miles Wilkins Twincam book (if you don't have it - get it!). Although he doesn't discuss 1600 blocks (I sense he doesn't agree with them) most of the internals are common and he has lots of good info on rods, cranks, machining, etc.

Have you just got a 711M bottom end - or complete with tc head? If bottom end only and you're using your existing head you'll need the appropriate spacer for the timing case plus different timing chain and chain tensioner, etc.

I run a 1600 block (not 711M unfortunately) - but the engine was in the car when I bought it. The 2 PO's did some racing but to date I'm a road user only. I have not touched the bottom end yet but I have had the head rebuilt.

When built up, my block was bored out .50 mm (.020 ") - yields just under 1700 cc as I recall. 1600 blocks accomodate this fine - a good 711M should be OK for 1.0 mm (.040"). You just have to ask yourself why you want to do it, how much you want to bore out and how much money you want to spend.

Don't know what pistons I have for sure. When the head was off for rebuild they appeared to be standard Hepolites (+.020" of course) - probably from the '80s - and I have an empty Hepolite box that came with the car so it's a fair probability. There's a lot on the forum about pistons.

125E rods are fine if you aren't going to push the rev's beyond recommendations.

I would recommend uprated bolts, studs, etc. wherever (ARP) - with square caps of course (which would be on a 711M anyway) - it's a small investment.

Use the standard oil pump. The later screw on filter type is nice (wish I had one). Unless you're racing, I think the high pressure pump will cause more problems than it's worth.

You'll run into some minor issues like you often have to use the traditional exhaust side engine mount on both sides. The normal inlet side mount is higher than the exhaust mount to ensure he carb's clear the footwell on the standard engine - but on the 1600's they will almost certainly push your valve cover right up to or over the bonnet line.

Where? - Sorry, can't help you. I know a very good engine builder but I'm afraid he's in Sydney (Oz)!

Have fun.

[Dag-Henning]

- pls remember ; using the 711 block and maintaining the 125E rods will require special pistons w/ increased compr. height ! ( - I take it you will keep you Lotus crank w/ 72,75 mm stroke.....?)

DH

[tdafforn]

I was planning on keeping the 711m crank and rods, adding twink pistons and having the block decked.. Is this not correct?
Tim

[types26/36]

Tim,
That is correct, you only need the special piston's (increased) hight if you keep the 125E rods and you will find the special pistons cost an arm & and leg compared with standard Lotus ones. Dont worry about the prophets of doom in regard to boring to 82.55mm, I would guess 95% of 711 blocks will bore to 85mm with no probs. (thats MY guess) I have done 4 or 5 and the only time I had a prob was when I got over ambitious and bored one to 86mm.......the bore collasped into the water jacket.
Oh, just remembered that was not even a 711 ...it was a 681F

[rgh0]

I f you dont have it get the Dave Bean Catalogue as this details all the practical combinations of cranks, rods and pistons you may want to put in a 711 block.

regards
Rohan

[tdafforn]

Rohan,
Will order the catalogue right now!
As far as the rods/pistons go I noticed that Burtons are doing accralite pistons for the 1600 conversion for 90 quid each...
How much cheaper can you get the Lotus ones?
Tim

[tdafforn]

I'm also assuming that I'll have to swap the sump and oil pick up etc from the twink?
Tim
PS have just finished dismantling the Ebay 711m I bought..
It looks pretty prestine, no marks on the main bearings which have standard shells and measure 50mm, the big end bearings are standard and the crank pin? diameter is 49.2 and no wear ridge on the bores (which measure approx 80.5 mm. So looks as though it hasn't had a hard life!

[rgh0]

Tim

I am no expert on tall block conversions as all my work has been done on standard 1500 blocks.

You can get custom made forged JE racing pistons complete with rings and gudgeon pins for around A$400 each ( around 130 pounds) which is what I buy. Mass produced cast pistons should be around half that.

I believe Ford tall block 1600 engines came with different sump configurations depending on the car they were used in. I think in the same way the 1500 blocks had different sumps. If the sump well is at the front you should be able to use the same pickup and sump as it came with in an Elan, if its at the rear you will need to change it.

regards
Rohan

[types26/36]

[quote="tdafforn"]I'm also assuming that I'll have to swap the sump and oil pick up etc from the twink?
and no wear ridge on the bores (which measure approx 80.5 mm. quote]

Sounds like you have a standard motor although the bore should be 81mm (80.980) as far as I remember without getting the books out.
Yes you have to fit the T.C. sump and pick up (providing it is the push fit in your T.C.)
Here is a couple of pics of the tall block conversion on my Seven.

[types26/36]

and these pics show the difference between the Xflow and Lotus rear oil seal housing.....note the Xlflow takes a wider seal. Either can be used with the correct sump seal

[Dag-Henning]

- the sumps w/ pickup are all the same from -67 and on. ( -as from the arrival of 6-bolt crank.) Except the Escort-sump of course, but that would not interest you guys.... DH

[tdafforn]

brian,
when you say "correct sump seal" what do you mean?
tim

[types26/36]

Tim,
If you look at the last pic you will see the distence between the two raised parts (where the sump seal fits) is different, the 711 takes a wider rubber seal. If you get a sump set for a 711 (and you are useing the 711 housing) this seal will be correct but the front seal will be wrong.
You can use the houseing of the T.C. on the 711 block and just get the Lotus sump set and all will be correct.
You could of course get two sump sets and use the rear 711 seal from one and the Lotus front seal from the other assuming you wanted to keep the 711 houseing on.
Hope you understand this

[tdafforn]

gotcha