Bedding in Piston Rings.

[Frank]

Having already had the smoky and oily experience I am trying to make sure that

the TR3/Warwick engine I'm rebuilding beds in the rings properly this time.

 

I've had a rummage around with the Forum search engine without finding gold.

 

Are there any TR assembly sequence/tricks should I use to make sure that the

rings bed in sweetly? It's in bits at the moment, and I haven't bought the

new pistons/liners so I can incorporate any honing or other machining that's

needed. What about during start-up and running in? Should I use a running-in

oil, and when can you change on to regular Duckhams?

 

I've heard the folklore about putting Vim down the inlets, but I really need

this to be foolproof. I don't want to be "tail end charlie" anymore!

 

Contributions much appreciated.

 

Frank

[Eyetee]

You can ask 100 people and get a 100 answers, listen to them all and glean your own theory, or like me find someone you trust and get their help. The last engine I was assisted in building the final assemble was paramount.

 

Bottom end (built with oil can waved at all moving parts) and gearbox put in car. Then spinning starter motor everything else was added piece by piece, oil cooler, filter, head, rockers, then set the timing and plugs.

 

Since then its been driven upto 6500 revs, should go to 7500 (when the valves consider bouncing) but my driving doenst warrant it and I want the engine to go on. Oil change after each meeting 1 * 20 mins qualifying, 2 * 30 min races approx 100 + miles, using Motul classic at the momment, a mineral oil that doesnt break the bank, unlike the motul synthetic that smells like bubble gum when fresh.

 

Cleanliness (sp) of all engine parts and area where engine is assembled crucial

[Rodbr]

Build up,

This is the most important part of the rebuilding process. CLEAN. Each and every component in the

engine must be clean. The machined parts, the new parts, tools that you use, and of course, your hands.

I have seen more rebuilds fail because of built in dirt when assembling an engine than any other reason.

Each little piece of dirt acts as a miniature machine tool which starts grinding and cutting new components

as soon as the engine is placed into service. I have even seen several engines that had dirt related

damage from just rotating the engine during assembly. These engines had never even been installed in a

vehicle.

Remember, CLEAN parts, CLEAN hands, CLEAN Tools.

 

A few years back I had a friend who swore by Molyslip in a spray can/bottle. As he build the engine he coated the parts in sprayed Molyslip and turned the engine over regularly as he went, coating again, and again.

Correct fitting of piston rings and pre coating of bores with Molyslip prior to fitting pistons, valve stems and valve stem oil seals are another area for careful attention.

Personally I would use whatever oil you intend for the engine from the getgo, and change the oil and filter a couple of times in the first 2-3000 miles.

We built, Lotus and Alfa twin cams, ford pinto, ford crossflow, MG, Ferrari, 2.6 vauxhall rally engines all with this technique and the engines lasted well and did not smoke.

 

Perhaps you could be more explicit in your decription of what happened and by what you mean by "a smoky and oily experience". How much of a rebuild had you done, how did you drive the car afterwards and the results. Sounds a bit like you may have had a broken ring. What is the reason for new pistons and liners?

 

Hope this helps and as the man says 100 people and 100 different answers, this technique worked for me and I built racing hillman Imps engines that would blow up if you looked at them the wrong way.

[Steve Knight]

Do NOT use molyslip down the bores. One of the most important parts of your rebuild is bedding in the piston rings. If not re-boreing, the old bores must be “glaze busted” and honed. Multigrade oils are too protective. Piston rings will never bed in unless you use a standard 30 SAE ( special oil is not necessary ) so the rings wear in properly against the bores.

Some engines may be smoke free without this. Run in for 500 + miles no labouring – reasonable revs are okay.

 

Extract from the Bible:

 

6.30 Running in

Race camshafts may need running in for a few minutes when first firing up - check the manufacturers instructions. The sort of revs required are: 1 minute at 1500, 1 minute at 1750, 1 minute at 2000 rpm, and repeat. The followers and lobes then get matched together.

 

You should have assembled the camshaft and valve train – plus the crank bearings etc - with assembly lube’; the all purpose stuff is ideal. Newly assembled engines (without valve springs) should turn over easily by hand, but spin it over on the starter without the plugs to build up some oil pressure, and bleed the air out of the PI injector pipes; all the unions must be loosened until petrol seeps out.

 

It is possible to prime the oil pump and pressurise the galleries first using an electric drill. Remove the distributor/pump drive gear on the side of the block, and use a long drive shaft to accurately engage with the oil pump. Run anticlockwise for about a minute.

 

Fill the radiator with hot water, and tighten up any hose leaks, then ideally poor in a final pint or so of oil to flood the rocker housing, that is after getting the first positive cough. Any 30 SAE grade oil is right for the job, special running in oil is not essential, don’t use multigrade.

 

You must never blip the throttle or allow the engine to idle, in fact race camshafts should never be left to tick over or excessive lobe wear can occur due to lack of oil flow. There is always a bit of a dilemma about running a cold new engine at 2000rpm. Maximum wear; over 70% takes place on a cold engine, but we need a healthy oil supply for the cam and valve train. You must protect new bearings but need to bed in the piston rings. Engine builders have different views on this, but all agree never labour on low revs, and vary the engine speeds as much as possible during running in, especially on long motorway journeys.

 

Pre heating the engine has positive advantages. An external heater will pump water around the block overnight to about 85 deg. A small paraffin heater under the sump or even a 150W light bulb under the bonnet will all help. Most modern race engine tolerances are so fine, they must only be started when hot.

[Guest ntc]

Don't believe all you read Ivor

[88V8]

Don't believe all you read Ivor

A chap becomes confused with all this information....