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MG Midget and Sprite Technical - Midget won't start !!!

I recently attempted to replace the factory exhaust headers with a Pacesetter exhaust headers. Before I removed the factory exhaust, everything was running fine, but now the engine starts for a few seconds and quickly dies out. I have not messed with anything electrical, so I'm pretty sure I don't have an ignition problem, and like I said before, everything was running fine before installing the new headers. The old headers had an inlet for an air injection pipe running off the air pump which now leads to nothing. Could this be my problem? If so, how do I fix it?
S McKean

I forgot to mention: it is a 1500cc from 1979.
S McKean

The air injector pump is designed to put air into the burnt mixture expelled from the cylinders. In theory, it promotes the burning of unburned hydrocarbons by the cat. Not all of us accept this theory and promote the alternative theory that the fresh air dilutes the burnt mixture, combining with it to show a lower CO and HC reading at the tail pipe where emissions are measured. It should have no effect on your problem.

I am not familiar with the Triumph engine and do not know if the late model midgets had the exhaust manifold combined with the intake manifold as the late model MGBs did. If it does, you may have an air leak at the intake manifold which is causing your problem. If the intake and exhaust manifolds were separate on the 1500 engine, then all you could have changed were the exhaust header and associated gasket(s). The engine will start and run with a leaking exhaust gasket. This would only leave some form of blockage in the exhaust system to cause your problem--think of stuffing a potato up the exhaust pipe.

I will be interested in seeing what information and ideas the 1500 owners can provide.

Les
Les Bengtson

Sounds exactly like air leak on the inlet manifold to cylinder head joint. With an enormous air leak you will tend to not be able to idle the engine and as the revs reduce the engine will cut out.
Bob (robert) Midget Turbo

Im afraid I dont know much about the 1500 as well....but dosnt the intake enter the head from the opposite side from where the exhaust goes out.

Just a thought....I wonder if the better flow with the new header, is causing extremely low back pressure, and thats entretupting the pressures inside the carberator thus effecting the diaprame....

gryf would be the one to talk to about this....

you might also try going to the triump section at the bottom of the page,,,and posting under tr6 and tr7.

prop
Prop

Prop, the intake/exhaust on the 1500s are on the same side.

Now as to the problem, it more than likely is a leaking intake manifold. They are notorious for leaks as the bottom 2 nuts are a bear to get tight enough.
Clive Reddin 76 Midget

Thanks Clive, I think you may be right. The new headers came with a real crap paper gasket to replace the old one, and those bottom two nuts are near impossible to get to. I removed the intake manifold to take a second look and the gasket was stained brown running from the bottom of the intake manifold. Any tips on getting a better seal?
S McKean

When I put my Weber on a few years back, I had the same problem with a leaking intake manifold. I simply got a second gasket and piggy-backed it on the first and tightened everything up and it's been great ever since. The gasket was less than a buck. The sealing of the air leak--priceless.
J London

You might check that the intake flange and the exhauste header flange are the same thickiness, I have heard a number of times that the 2 flanges can be differant thickiness,,,and need to make a step down washer....but yeah Id say your in the corrct line of thinking....When I put my header on my 1275, it was a bear to get to a couple of threads and had similar problem but mine ran like crap, till I hit it with wd40 and found the problem....just make sure they clean and crisp so they spin on with little resistance.

prop
Prop

Prop. That was what I was going to suggest. Many times, the thickness of the header flange is different from the thickness of the factory intake manifold's flange. When tightened together there is in improper seal. You need to measure the thickness of each flange, then, shim the thinner one out to the required thickness if you are to get a good seal.

Fel-Pro makes quite good gaskets and most auto parts stores can order what you need--either an entire upper or lower gasket kit, or individual gaskets.

Les
Les Bengtson

Yeah, those two lower nuts are really difficult to get to. I was able to snug mine up by slipping an open-end wrench between the two manifolds and making short swings, but since you've got the header, that will affect access. Not sure how!

And yes, the two manifolds bolt together on a stock 1500. But ideally, you'd torque all the mani-to-head nuts first before tightening the bolts that hold the manifolds together. This isn't really applicable here, since the header won't bolt to the intake at all.

I agree that you need to check the flange thicknesses. Even though the clamps are free to rock a bit, they apparently clamp much better on equal flanges.

Now for the air pump hose - since the pump isn't doing anything anymore, you should be able to remove it, or at least take the drive belt off.

-:G:-
Gryf Ketcherside

As has been stated, Fel-Pro make decent gaskets and that's what I have on my car rigt now.

If you get the head set, it will give you every gasket from the head gasket all the way up to the valve cover. Can't hurt to have some spares around.

The Fel-Pro one will be aluminized on one side and is fairly robust. Can't recqall what side goes where but it should be marked.
Clive Reddin 76 Midget

The clamps on the 1500 engine should be a bit more forgiving of unequal flanges, but it could still be the problem.
Dave O'Neill 2

It's good to see I'm not the only one who's having a real pain getting to those bolts. I'll definitely check the flange thickness now, I'd never really considered how it would affect the seal.
S McKean

This thread was discussed between 03/05/2008 and 06/05/2008

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