Engine rebuilding

[rgh0]

HI Stephane

Good to see you got an Ultrasonic gauge

When measuring a block I measure each bore at the front and back and each side ( North, South East West). The casting OD has small lobes between these measurements so this is the normal minimum thick areas.

My thickness gauge has a scan function and automatically reports the minimum thickness when I scan from top to bottom. If manually scanning I would check at 5 or 6 points down the bore from below the top deck to the bottom of the water jacket. The bottom of the water jacket is often the thinniest due to corrossion in this area where sludge has built up. The oil cross drilling passage between cylinder 2 and 3 below the water jacket needs to be checked if possible especially if boring above 84mm. It takes care to pick this up but is possible

your guage should have a calibration function and you should use this to calibrate the speed of sound in you actual block casting in an area you can directly measure.

The most critical areas are the thrust faces on the bore in the top half of the cylinder which sees the greatest piston thrust loads. Small areas of thinner than desirable in other areas can be tolerated but its a judgement issue

Ideally i aim for 3 mm minimum wall thick in a race engine
In a road engine 2.5mm is OK.
If the block has been sleeved it get more complicated which I will not cover here as from memory I dont think your block had sleeves installed ?

This thickness target is consistent with the orginal Lotus bore grading done with spot caliper measurements

Offset boring can normally be done to achieve these with 83.5mm up to 84.0 mm bores assuming the block has not had a large overbore previously without offset boring and it already has a thin wall.

cheers
Rohan

[rideaway]

Hi,everyone,

Thanks for your reply, Rohan

I'm working on refurbishing my engine block so that I can take correct measurements and clean it properly.
The water chambers looked clean with the core plugs in place and the core plugs looked spotless.
But to my surprise, when I removed the core plugs, which were as thin as paper and ready to leak, I found a large quantity of mud.
Even on old Perkins tractors engine, I'd never seen so much.
It seemed to me that the little time I drove the car, the temperature was high.

I think that for Twincam specialists, this is a well-known problem, but for others, I think that when you're working on the engine, it's essential to replace the core plugs.

- What method do you use for cleaning (mechanical, acid)?

- Do you use a sealant to reassemble the core plugs?

I'm sorry if these questions have already been asked, but sometimes I have trouble searching because I don't know the right search terms. Sometimes my friend Google translates in a strange way.

Best Regards

Stéphane

[RichardHawkins]

Stephane,

I removed all the core plugs, used bent bits of wire and screwdrivers to remove what “mud“I could see and then used a pressure washer through all the openings, this seemed to work. I did try proprietary cooling system cleaners, but these made little to no impact on the “mud” that you mention.

With regard to sealant, I spoke to Loctite for advice, who recommended Loctite 243 as used by Ford in their current engines.

Hope this helps,

Richard Hawkins

[mbell]

I took a similar water and poking approach and removed quite a lot of junk out of the engine.

[2cams70]

Stephane,

I removed all the core plugs, used bent bits of wire and screwdrivers to remove what “mud“I could see and then used a pressure washer through all the openings, this seemed to work. I did try proprietary cooling system cleaners, but these made little to no impact on the “mud” that you mention.

With regard to sealant, I spoke to Loctite for advice, who recommended Loctite 243 as used by Ford in their current engines.

Hope this helps,

Richard Hawkins

Threebond make a specific sealant for core plugs - 1386B

[rgh0]

I also have used screwdrivers and wire to clean out the mud and sludge followed by high pressure jetting. If the block is going to be bored by an engine shop I get them to also clean it after this in the washing tanks that has a mild acid. I have seen people making up a molasses solution and soaking the block in a large container of that as it is effective at removing corrosion scale in the water jacket.

I use brass core plugs and loctite 243 also as a sealant and retainer.

cheers
Rohan

[lotusfan]

Rohan - I’m curious why you use brass core plugs. Isn’t there a chance of galvanic corrosion between the brass and cast iron? And surely steel core plugs would be protected by the antifreeze you must use anyway?

[rgh0]

I have pulled corroded steel plugs out of many blocks but never seen a corroded brass one. With regular antfreeze changes maybe it makes no difference and all the steel plugs I have seen were abused with no coolant changes. I Just stick with the Brass as they have worked for me and it appears than they will last even with depletion of the coolant corrosion inhibitor.

cheers
Rohan