Engine and Transmission Tech

Well, after a year of slow progress, my MGB Rover 3.5 conversion is fully assembled and I'm finally trying to light the fire. I primed the oil pump, made sure I'm getting spark at compression, double-checked my firing order, and turned on the fuel pump. I'm using an Edelbrock 500 CFM, and it's definitely getting fuel to the venturis - I can see it on the jets. However, it's nowhere close to catching. I get intermittent backfires (through the exhaust, not the carb), but that's it. I have screwed the mixture screws all the way in (lean, I believe).

At this point I'm past my depth - where do I go from here?

Thanks!
Billy

Double check your firing order. Unlike the MGB engine it is possible to get the distributor installed 180* out so you have to make certain that you are on the compression stroke.

Jim

My intuition is the same as Jim's... I suspect the distributor is 180 degrees off. However, I also think the idle air screws need to be backed away from their extreme (closed) setting because you'll need some fuel to get past them for the engine to idle!

If you don't have an owner's manual for the carb at hand, you can download and read it in pdf form from this link: [www.edelbrock.com] - the idle air circuit's theory of operation starts on page 2 and tuning instructions for that circuit are on page 7.

I did that on a 2.2L Dodge turbo. Easy thing to do. The other possibility that's happened to me before is I put the dist in one cog off. Something that has worked for me in the past is to have your buddy crank it and you turn the dist back and forth with a thick glove on.

Ditto on the distributor.

Another vote supporting the previous posts
Get your #1 piston at TDC and check that your distributor rotor is firing on #1 cylinder.

Right you were guys, thanks! Despite learning about both of these pitfalls while doing the initial testing of the ignition, I screwed it up when I pulled the distributor to re-prime the oil pump before turning on the fuel.

I corrected this and the engine ran! For about three minutes before it blew up. An apparently internal clanking appeared while I was adjusting the idle, and turned into a LOUD clanking in the three seconds it took me to dive through the window and kill the ignition.

Apparently the guy who rebuilt the engine screwed it up, and I'm about to be looking for another rebuild or another engine. Curtis or anyone in the Denver area, can you make recommendations?

For now, I'm going to go cry over a beer.

Did you get the distributor inserted fully? If it was not, it would not have engaged the oil pump drive tang and would have starved the engine for oil. We should have warned you about this, personally I never gave it a thought as I'm sure the others would also say. Second nature is not good when giving advice I guess. Three seconds may or may not have been enough to damage the bearings, and probably did no other harm. If that was the problem, I would first re-prime it and see what oil pressure you get, and then see if it still turns over easily. If both of those check out you may be safe to restart.

Jim

The distributor was fully engaged. I stupidly forgot to look at the oil pressure while the engine was running, but I just pulled a valve cover and there was plenty of oil up there, much more than after I primed the pump (during which operation I got 57 PSI).

So I don't think it was an oil issue. I'm 99% sure a connecting rod has failed, so I'll drain and pull the pan and see what there is to see.

Bummer. Well, carry on. Anything worth doing is worth doing twice. In the long run it'll be worth it.

Jim

Well, I pulled the pan and didn't find the dangling connecting rod I was expecting. There was plenty of oil in the crankcase. When I crank it, everything seems to be moving fine, both in the crankcase and at the rockers. However, there is definitely a funny sound I'm having trouble localizing. It's a "pok-pok, pok-pok", rather than the "clank-clank" I was experiencing, and I can't tell which cylinder it's coming from.

For all I know, the problem could be in the LT77, which I definitely filled with the right amount of ATF, and which was definitely in neutral.

I'm at my wit's end. Is there anyone in Denver who could take a look at this thing?

Hi Billy, I'm out of town at the moment but I'll be back in Longmont in a couple days. I'm no motor-head, but my eyes and ears will be at your disposal if you think it might help. As for recommending a Pro... I haven't worked with any of the local shops yet.

One quick idea I have is that you might find it helpul to remove the spark plugs, so you can evaluate the engine without compression. Do you have a convenient way to turn the motor over by hand without using the starter motor? (I use a big socket wrench on the crank bolt... the same bolt that holds the harmonic balancer on.) Turning the motor by hand through several rotations, see if you can identify any binding or any noise that might help you isolate the mechanical problem.

Good ideas, thanks. I'll need to pull the radiator to put a wrench on the crank bolt, but I'll probably end up pulling the engine anyway, so big deal.

Get an engine stethoscope or even a length of fuel line to help locate the source of the noise.

This article will give you the basics:


Engine Noise Diagnosis 101

[remanufactured-engines.com]

Engine Noise Diagnosis 102

[remanufactured-engines.com]

Makes the noise with the pan off? (Rods sometimes hit the pan)

Jim

Many many years ago at a shop where I worked in the mid 70's we had an engine making noise we thought was a rod, but it wasn't, it was the crankshaft moving along it's axis and one of the counterweights was hitting inside the block near a main bearing journal.
I don't remember the make of the car.

One of the first things I would do in your case is drain the engine oil through some cheese cloth or something similar to check for metal filings or pieces. If there is metal in the oil , determine what metal it is (aluminun, steel, iron, brass) and you might get a hint as to were the problem lies.

Steve

Having verified everything was moving normally in the crankcase and no connecting rods appeared loose, I buttoned it back up, refilled and re-primed, pulled the plugs, and did a compression test. All cylinders have pretty similar compression. The noise is almost definitely coming from #3. Anything left to do before pulling the head?

One time I found a lock washer in one of the cylinders of my TR4A. Apparently it was dropped into the intake by a neighborhood kid while I wasn't looking. I started the car and heard a racket like you described and thought the engine was toast. When the head was removed, there was my washer, stuck into the top of the piston, but not through it. I pulled it out and buttoned it back up. Even used the same head gasket as I recall. I am still running that piston 25 years later.

I'm definitely worried about a washer or other foreign object, but not really optimistic that my story will end as happily as yours. Good to know there's hope, though. Thanks. Will have more on that tomorrow night, I guess.

Found it!

When I pulled the head, I found no washer, but a bit of debris in #3. The debris was black, which led me to suspect the rings. No damage to the cylinder wall, at least to my untrained eye. The head was fine, and the noise continued when I gave it a crank. So I scratched my head and drained and pulled the pan again. Turned out my first guess was right. Somehow I missed a blatantly loose bearing cap on #3.

So pulling the head was technically a waste of time and gaskets, but no tears over that!

Before I tighten the bearing cap back down, should I put something on the threads so it doesn't loosen up again? Are there supposed to be lock washers on the clamps? I should probably check the bearing for damage, what do I look for? And finally, what is the proper torque setting?

Thanks for all your help with my little drama!