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MG TD TF 1500 - Engine breakin procedure?

OK, Lily Christine IV is alive again, the question is how best to proceed with the "break in".
I've trolled through the archives and found a great deal, most of it boils down to this :

" 2,000 RPM with vehicle stationary for 20 minutes, to break in the cam & lifters. Then low intake manifold vacuum,repeated with high vacuum. I.E. wide open throttle, followed by off throttle, done on the highway.Repeat this on/off throttle as often as you can during the first 500 or so miles, this seats the piston rings. Use regular non synthetic oil for break in. Rpm limit? perhaps 4,500." (thx Len Fanelli).

I noticed Tom Lange adding that the head should be retorqued after half an hour or so, in an unrelated thread just recently.

So, please, any additional stuff I should be checking and looking at?

Retorquing of any other engine bolts apart from head?

Firstly, I need to check and adjust timing and tuning, neither has been done since the rebuild.
My aim is to run the engine for an hour over the next day or so, checking for specific issues. Oil pressure, water temperature etc. My crankshaft pulley which has been getting hot needs to be monitored. I expect oil to continue burning off the engine but less over time.

Please, any suggestions are very welcome! I'm not sure I've ever been more nervous :)
Geoffrey M Baker

Fire suppression should be at hand..

Key on...check for fuel leaks

If you haven't primed the oil system... Spark plugs out..key off...crank the engine in 20 second intervals until you see oil pressure. If you don't see pressure after about 4 attempts them you may need to take other measures to get the pump primed.

Keep a surplus coolant container handy as there is a good chance you will need to add some as the pumps pushes coolant through the system and displaces air pockets.

Fire the engine and listen for odd noises and look for any leaks... observe that the oil pressure jumps up to a good operating range. screw driver should be handy to increase the idle speed immediatly to 2000 rpm.

Keep checking for oil/fuel leaks during the inital brake in and watch the oil and temp gauge and shut it down if any signs of trouble appear.

Of course you should set the timing statically before you begin.

Best of luck.
MG LaVerne

err... not to discount the advice on re-torqueing, but I never do, unless I have an aluminum head.

Dave Braun


Why don't you do a re-torque? Seems a good practice to me.

And for those that do re-torque - - do you do it with the engine hot or after it cools?

Tx, Dan
Dan Nordstrom

I didn't used to but I do now on advice of someone with a lot more experience than me. Hot.
MG LaVerne

Geoff I'd been following your "51 TD engine restart" with some interest & had noted that you've already had her running on a couple of occasions. I wondered how critical it is to ensure that the very first time she turns over, that the engine is run for the 20 minute break in period? I understood that the cam & follower damage is likely to occur in the first few minutes. Perhaps someone here who has successfully rebuilt XPAG engines can offer an opinion? Cheers
Peter TD 5801
P Hehir

May I expand a little on my question.

Seems waiting for the engine to cool would be the proper procedure. Engine heats up and expands then cools off and shrinks. Since we are dealing with several different types of metals, Cast iron (block & head), steel (various bolts), and copper (gaskets).

Since I am nearing my start-up this is of importance to me.

Thanks guys.

Dan Nordstrom

I always torque them at least four times when cold (after start-up, after an hour, at 100 and 500 miles), and have not had a blown head gasket in almost 30 years.

I hate to remove and re-do the valve adjustment, so I use a 19/32" short socket bought at the Tool Barn for a quarter, to torque the head nuts with the rocker gear in place. I only have to remove the clips on the end of the rocker shaft to reach those head nuts!

Saves a ton of time.

Tom Lange
MGT Repair
t lange

Yes on retorquing the head when hot. I got a couple or more of the head bolts with significant rotation when I did mine.

Alex Waugh

Geoffrey. One item I noted. NOT regular oil, but an engine break in oil with added ZDDP. A good break in oil that my machinist recommended is Driven Racing Oil. Here is a web where they talk about cam break in.

Break in is the most critical point for the cam and lifters from what I have read and you need the high ZDDP.
Bruce TD4139 Cunha

I change the oil and filter after the first run. Think it was Tom Lange who mentioned to torque the bolts at three levels prior to reaching 50 PSI. In proper sequence.

On actual drives. Fluctuating the speed and rpm is critical. Do not go far from home. Bring tools with you and extra coolant.

Relax it eliminates tunnel vision and you will see and hear things better.
JWP Policastro

Just copied & pasted the following from the link mentioned by Bruce:

"Break-In Preparation

Always remove the inner spring during break-in when using dual or high pressure valve springs. An alternative solution that addresses this same concern is using a set of low-ratio break-in rocker arms. Both of these solutions provide your best chance of proper camshaft break-in and long term durability. While these tips may be a slight inconvenience, a little time and effort on the front-end is much better than destroying your new engine.

Proper Procedure

As soon as the engine fires, bring the rpm up to 2000 to 2500 during the first 30 minutes of operation. Slower engine speeds will not supply the camshaft with an adequate amount of oil for the break-in period. The engine rpm may be varied periodically from 2000 to 2500 to direct oil splash to different areas of the camshaft. After the 30 minute break-in period, the inner valve springs should now be replaced and the correct rocker arms installed."

It seems this procedure should be followed as soon as the engine fires. Also this is the first mention I've seen of the necessity to remove the inner spring during break-in. Re-torquing is good practice, especially so if the CR has been raised & Tom's method of performing this operation with the rocker in situ is a good tip. Cheers
Peter TD 5801
P Hehir

I doubt many go to the trouble to remove the inner valve spring but I have seen that before. Another builder recommends setting the valve lash very sloppy for initial break in as well.

You might consider putting a drop of white paint near the top of each push rod and observe that each rod is spinning when the engine is running. It is imparitive that they spin or the tappets will be ruined in short order.
MG LaVerne

This thread was discussed between 07/01/2016 and 08/01/2016

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