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MG MGB Technical - Starting a car with rebuilt everything

I am getting closer! Last weekend I got the engine into the car and the car finally into the garage. I am starting to bolt all the extra bits onto the engine again.

It's still a way off but I am starting to look forward to the day I can turn this engine over. Everything has been rebuilt. It has a new standard cam shaft that will need bedding in. I also rebuilt the carburettors (HIF4s) and also rebuilt the distributor (25D). The car was originally a 1978 Californian one (I finally got my Clausager book to check) but it has been de-yanked in the past hence the odd combination of carbs and dizzy on a 18V engine. When I got the car all the emissions stuff was gone and I have rebuilt it with new HC pistons. I have also fitted K&N air filters using the Bob method. The other mod I made was to port a carb to get vacuum from there instead of the manifold.

The question is what do I need to do in what order to get it running AND run in? I have all the manuals and looked in the archives but it would be great to have one definitive list of steps so I don't mess up. The bit that worries me is the initial start up and when to bed the cam in and for how long. Also the K&Ns may mean I need to go to the richer needle but it seems you don't know that until you try it. I am thinking it might be best to get the car running on the standard air filter and needle setup first.

So the things I need to do and in the order I think I need to do them are:

Set valve clearances, setup distributor points, set static timing, setup carbs so the car will start, put some oil in the cylinders and over the tappets and push rods as well as prefilling the oil pump and filter then turn the car over on the starter with plugs out to get oil pressure, put the plugs back in and start the car. Adjust the carbs as in the manuals for the correct idle, balance, etc.

Then I get a little hazy. Should you dynamically set the timing then run the engine to bed in the new cam? Or do you do the cam first? Also my GT always needed choke to start from cold so I imagine this roadster would too but they don't mention this in the manuals when tuning the carbs and running them first time. In that initial setup position will the car start without choke?

This is the first time I have done any of this so I kind of have to learn how to do everything all at once!

Simon
Simon Jansen

Simon, I think you are worrying more than you need to. If you do the steps you mention above, your engine will be fine. I've rebuilt several engines in my life and have always run the engine at above idle for the first few seconds and then slowly increase the revs until I'm about halfway to redline for that particular engine and then slowly back off on the revs until I'm just above idle and then repeat this for about 5 minutes before allowing it to idle. Check for oil and coolant leaks and set your dynamic timing. Gently drive the vehicle under "normal" conditions for the first 100 miles or so before any drag racing, etc. Your cam will be just fine. Just my opinion.

Scott
Scott Wooley

Simon,

Yes you will need choke to start the engine.

Set everything as you suggest.

Start the engine and have an assistant take it immediately up to 2500 rpm and hold it there.

Check under the engine for leaks!

Once you are happy with the engine temperature and oil pressure then adjust the idle screws to hold the revs at 2500.

Keep it at 2500 for 20 minutes.

If you need to make adjustments then turn it off - don't let it idle.

After 20 mins, turn off, allow to cool, retorque the head nuts and adjust tappets, then you can set the stroboscopic timing and fine tune the mixture.
Chris at Octarine Services

Sounds of my engine's first start after rebuild:

http://zippo.homelinux.org/mg/audio/start-mg.wav

Although the car is an MGA, the engine is a 5-main high compression MGB unit. The "Shut it off!" call at the end is in response to a fuel leak. (Warning - this is a 700k wav file - I haven't gotten around to converting it to mp3 yet.)
David Breneman

Simon,
Before you actually fire the engine spin it on the starter (plugs out) until ol pressure appears on the gauge. A cloth o loosly draped over the plug holes will stop any mess from the bores getting on the paintwrk.

This may take some spinning so let the starter cool between spins and spin in short bursts only of about 15 secs or so and have a second battery available also if possible.
If no pressure appears on the gauge do not proceed and start the engine until you find out why.
If all is as it should be refit the plugs and fire up and get the idle to about 2500 or so as alrady suggested.

One on the road keep the revs above 1/3 and below 2/3 max rpm and avoid any constant speed running for long periods like 2 hour freeway drives etc.
Varying the engine speeds and loads over a 500 mile or so period will help bed things in nicely.
Change the oil and filter at 100 miles and again at about 500 miles to get ALL the metal particles out of the engine.
Keep in mind the g/box and diff as well if they have been rebuilt and do the 100 / 500 mile treatment there too.

HTH, Cheers , Pete.
Peter Thomas

Simon
For best results use proper running in oil for the first 300 miles.
Graham
Graham Cherry

Simon - I was looking for the advice on Camlube - if you haven't used it - it may be worth taking some advie.

RMW

When I rebuilt the engine I used a lot of assembly grease on everything. It was sort of red stuff. The engine has been sitting for several months and that is still smeared over everything how I left it.
Simon Jansen

Simon What Chris and others have said but I would just like to add. Have a fire extinguisher handy just in case of a short or leak and when that first cam beding in run is over and the engine torqued and adjusted drive it as normal,dont baby it(or flog it)and above all dont let it lug or idle for extended periods. All the best with it. Denis
DENIS

Simon,
Sounds like your are well on your way to getting it running.One thing I would like to add is while you are spinning the engine over to get oil pressure up with the plugs out is to make sure you disconnect the power to the fuel pump.This will prevent fuel from spraying out the sparkplug holes.
Good Luck,Tony
Tony Shoviak

To specifically answer your questions...

When you have new cam or lifters or both the "bedding in" of the cam is paramount upon initial start-up.

The adjustments you describe are spot-on. Don't forget oil in the dash-pots.

Couple of other ideas:

Start the rig with the coolant cap off so you cna top it up as bubbles will invariably be captured in there.

Don't "hold it at 2500 rpm" for 20 minutes. I disagree here (as do other sources) and believe you should vary the rpm between 2k and 2.5k for 10 minutes or so (several seconds at each "step"). Your cam manufacturer is the final arbiter on this as they are the ones to satisfy you if it fails.

Shut it down to make any adjustments or if any leaks develop. Don't let it idle until the 10 min bedding in is finished.

Don't let it run without a load on the engine as much as possible. Get the adjustments and settings close enough to go and put some loaded miles on the new engine... This is ring-bedding time and being too gentle will lessen the seal and possibly lead to failed rings.

In the initial start-up position (two and a half turns "down") will likely be plenty rich to obiviate the need for a choke. Unless you are replacing the carbs exactly as they came off the (previously running) engine, in which case choke should be used, as before. I squirt a little ether in there to ensure firing but that's me (and I hear the cringes!).

The carbs can be balanced and properly tuned after all is happy with the cam but some "tweaking" can certainly be done as it is in the initial bedding run (pisons have equal lift, weaken or enrich for excessive soot or white smoke, etc...) but only enough to eliminate major difficulties.

Nothing wrong with dynamically setting the timing for max advance while bedding in either.

Enjoy.

Mike!
mike!

This thread was discussed between 17/02/2005 and 21/02/2005

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