Door stop or worth bringing back to life?

[JJDraper]

I have a block which I acquired some years ago for the price of the scrap iron. The story was that it had been machined to Lotus dimensions and the project stalled, as so many do and the block was never used. The bores are at 84.6mm, and the height from the underside of the main bearings (without shell) to the top of the deck is 175mm - as far as my dodgy measuring goes. I have in mind sleeving back to standard and building a replacement short engine for the next time I have to lift the head on the existing engine. I have attacked it with some wire wool and the deck looks unused and OK. The bore also look unused and OK - no cracks visible. Would they take a sleeve? The block type is unusual (691), and the engine number is strange - anyone recognise the number formatting? The rear dipstick hole has been welded/brazed closed. The main bearing caps are square type and look original & OK.

The existing engine in my car is on +60 with 100k on the current bores, so is due some attention, but I don't want the car off the road for the time it takes to fettle it properly.. I would like a nice fresh block ready for the day the old one needs to be changed.

Anyway, does the group think this old rusty block is worth bringing back to life, or should be left as a door stop? Any UK machine shops in the MK/Northampton area who could give a formal assessment?

All advice taken on board and considered appropriately!

Thanks

Jeremy

[types26/36]

The 691 block is a 1600 Xflow block fitted to the mk1 Capri and I think to some late Mk2 Cortina's, it is the 1600 Xflow prior to the 711 block (the 701 block was a 1500 used by Lotus) I think the 691 had the square main bearing caps as per 711 but still had the 1 5/8 rear core plug while the 711 had the 2" rear core plug although I'm open to correction there.

[RogerFrench]

Dead right, this is the first crossflow 1600 block, fitted to early Mk2 Cortinas etc.
I had a 1970 GT with just such a block.
The head had a small combustion chamber, unlike the perfectly flat head that came with the 711M block.

[types26/36]

Dead right, this is the first crossflow 1600 block,..

I'm afraid that is not quite correct, the first1600 Xflow block was the 2737 followed by the 681F (which was available as both a 1500 and a 1600)
The 681 was also available as a 1300 XFlow (although I have never seen one) and the 2733 was a 1300 Xflow.

[JJDraper]

A few more measurements..

Rear core plug is 2", deck height from main bearing centre line to deck is 204mm or 8", but this is with a steel rule not calipers, so may be the odd half mil out.

Does anyone have the standard twin cam deck height I can compare with? I know the bore is a little wide (!), but don't have the block dimensions anywhere.

Thanks

Jeremy

[types26/36]

This should help

[JJDraper]

Thanks for info - mine doesn't really fit any of these measurements, so I guess I will have to speak to an engine shop. Looks like it will need to be decked & linered, if they can get them in! 85mm pistons sound a bit scary.

Jeremy

[types26/36]

If it does not match the dimensions for the 1600 XFlow it has probably been decked for TC use.
Here is an other list mentioning the 691 although it does not give deck heghts.

[promotor]

It looks to me like it's been decked from the standard crossflow height already - probably for use with 1600 crank and rods, and Lotus twin cam pistons. It should be approx 5.75mm shorter than a standard xflow block if it has been decked with the intention of using 1600 parts and T/C pistons (5.75mm is the approx difference in the compression height of a crossflow piston and a lotus piston).

May not be suitable for flange top liners due to there being less material around the top of the block (there is a big chunk of material at the top which is removed when decking for a lotus spec block) so it would probably need to have straight liners.

Probably not worth it considering how much linering costs - cheaper to get a crossflow block and deck that and bore to standard lotus size. Depends if you like a project though!?

[rgh0]

Hi Jeremy

The lack of thickness in the top of the block due to the decking plus the over boring means it is potentially to thin and weak in the top bore area and not worth doing further work on. As a minimum I would spend a lot of time doing some ultrasonic thickness checks on it first before deciding if its worthwhile spending more money on.

Probably better to start with another block like promotor says. I have never liked the 1600 blocks decked like this one has been done to fit twin cam pistons on a 1600 stroke crank. For a 1600 stroke engine I would far prefer to use a standard height 1500 or 1600 block and sort out the rod length and piston deck height to suit either of the standard blocks.

cheers
Rohan

[RogerFrench]

Dead right, this is the first crossflow 1600 block,..

I'm afraid that is not quite correct, the first1600 Xflow block was the 2737 followed by the 681F (which was available as both a 1500 and a 1600)
The 681 was also available as a 1300 XFlow (although I have never seen one) and the 2733 was a 1300 Xflow.

Sorry, I should have said early 1600 xflow, not first.

[jk952]

If measurement of any use to you: I have a 681F6015DA ( has a N above that no.) engine in my basement mostly assembled, measures about 8.25 inches from crank to top of block or 8.35 from pan surface. Engine still at stock bores and x flow head guides orig. with the valve recess mentioned by others, valve cover sticker says 1600GT, rear plug hole about 1.65 in., 6 bolt... so I assume not re machined.

[JJDraper]

Thanks for all the comments, looks like it will remain a doorstop for the moment. Given the cost of liners, fitting etc one of these begins to look attractive - seem a lot cheaper than the QED ones. Why?!

http://www.ebay.co.uk/itm/FORD-RACING-N ... 27e920c4fb

Jeremy

[promotor]

Having seen one of the QED ones and spoken to one of the guys at QED at the Donnington show they reckon that their block will take 86mm bore no problem. So I guess the amount of metal and slightly different design is the difference in cost.
I think at that bore size the cross drilling for the oil gallery that passes between cylinder 2 & 3 most likely won't be present in QED's block as it'll be a weak point if not likely to go through if it's not cast and drilled in exactly the correct position. The oil would likely have to be directed on the outside of the block with an oil pipe and NPT type unions if that is the case.

Plus I think the ones like the one on Ebay were re-cast be Cosworth in USA and possibly done in large numbers, whereas the QED ones are probably done in very small batch numbers which also ramps up the cost.

If you really don't want to spend much money use a crossflow block with lotus pistons and longer rods, or specific tall block pistons : http://www.burtonpower.com/accralite-fo ... fl114.html. Still nearly half the price of that block even after boring the block and you get forged pistons and more capacity than a proper Lotus block!

[rgh0]

The QED blocks have Siamese bores and no cross drill to allow the bigger 85mm + bore. The Ford Motorsport blocks are a close reproduction of the original blocks and cannot go much beyond 83.5 mm in the same way the original blocks cannot. I you want to build a big bore big capacity engine then go with the QED block if you want a more standard engine capacity and cant source an original Ford block then use the new Ford Motorsport blocks

cheers
Rohan