WillieB's 1275 Engine Rebuild

[MiniDave]

OK, so the crank and rods checked out fine, so we're going ahead with the build.

Consensus is the combination of loss of oil pressure, lugging and detonation caused the problem. Broken ring land is pretty obvious sign of detonation and the wear pattern is because of the offset rods causing the majority of the thrust to be on that side.

So, we'll make it all new again, I'll make sure the distributor advance is working correctly and WillieB will make sure he's not lugging the engine. I still need to take the transmichigan apart and look into the oil pickup screen - maybe it never had one but I find that hard to believe.

More as it happens.......

[cstudep]

Glad to hear everything checked out with the crank and rods. Were you able to get away with a simple honing or do you have to go with larger pistons?

[MiniDave]

Don't know yet, and he hasn't said if he's going to grind the crank down or just polish it, but at least it's straight and not bent.

[MiniDave]

One of the mysteries of this engine is what happened to the screen over the end of the oil pick up tube? You can see in these pics the imprint of the screen and where it might have been soldered on. I don't know if the screen got chewed up in the gears and run thru the engine or if maybe the tube didn't have one when it was assembled?

Either way - it's a puzzle.

Of course my assumption is it was there, came off and got chewed into tiny bits and sent thru the works......either way we'll put a new one in.

I've looked thru the sump and can't find any trace of it, and absent a brass magnet or a complete stripdown of the gearbox I don't know if I will. So. My plan is to set the gearbox on it's end and spray some clean clear solvent in the case and see if anything washes out - it not I'll call it good. I already stood it on it's end in a clean pan to drain every smidgen of oil out and found no pieces in the oil....I'm thinking it's either been digested or it's in the oil filter in a billion bits.

[Willie_B]

Stranger and stranger still... 50.gif

[BruceK]

I wonder if pieces of the screen could show up in some of the oil galleries? I sure hope not.

[MiniDave]

The machine shop has already washed the block out, so I don't know....I asked them to check but I'm sure he just put it in the jet washer and turned it on....

difficult getting parts right now, particularly suspension and engine parts. WillieB is looking all over for pistons - no one has them.

[94touring]

Just need the one or having to bore for a new set?

[MiniDave]

Same bore, but we decided to replace all 4 since one broke, the others could be suspect. 20 thou over 1275 high compression.

Machine shop update: All good news, the bores will easily clean up with a light honing, the crank is straight and not damaged, we'll do a micro polish on it. The head will only need a very light recut of the seats and it's good to go. The rods are straight and not damaged.

So, we'll have them install the new pistons on the rods, then check the balance and do whatever needed there. Then I'll pick it all up and start the rebuild process once I get all the parts. It should be home for Xmas!

[Jimini II]

That's good news from the machine shop.
Just curious Brad with the detonation issue/damage what distributor were you using? I think the last time you had some issues coming home from MMW a few years ago that you were using a 123 distributor?

[Willie_B]

That's good news from the machine shop.
Just curious Brad with the detonation issue/damage what distributor were you using? I think the last time you had some issues coming home from MMW a few years ago that you were using a 123 distributor?

The 123 issues were a wet dist. I am now running one from CSI. Programable just like the 123. It could be that the rattle I was hearing was not mechanical but pinging. I just did not think that was what it was so just keep driving.

[MPlayle]

Just curious: if it was detonation (pinging), what is the solution to prevent it from happening again once the damage has been remedied?

Would it be a combination of higher octane fuel and a timing adjustment?  Change in timing which way?

[Jimini II]

That's good news from the machine shop.
Just curious Brad with the detonation issue/damage what distributor were you using? I think the last time you had some issues coming home from MMW a few years ago that you were using a 123 distributor?

The 123 issues were a wet dist. I am now running one from CSI. Programable just like the 123. It could be that the rattle I was hearing was not mechanical but pinging. I just did not think that was what it was so just keep driving.

I guess you need to look into the advance curve you were running with the new CSI dizzy.

[MiniDave]

Retarding the timing a few degrees should cure it, assuming the compression ratio is not to high. I'll be able to more accurately check that once I get the engine back and do the dry build so I can measure everything. I'll also CC the chambers while it's there.

[94touring]

This was under load it was making the rattling?  Do you recall which csi curve you're using?

[Jimini II]

Retarding the timing a few degrees should cure it, assuming the compression ratio is not to high. I'll be able to more accurately check that once I get the engine back and do the dry build so I can measure everything. I'll also CC the chambers while it's there.

Yes and checking the maximum advance.

[94touring]

No idea which curve on the csi???

[Willie_B]

Just picked up a belt cam drive setup. Looks very well made. Probably overkill. Should I go for it and have Dave use it?

[cstudep]

Wow that thing looks really well made!

What's the draw to going to a belt setup and since we are on that subject, are these "interference" engines?

Having had/have several different Toyota's the timing belt models that are interference engines are just a hassle. Of course at the miles generally put on a classic like this it's probably not as big a deal.

[BruceK]

I see there's a lot of adjustment with that belt, but the service life of a belt would surely be shorter than with a nice duplex chain, right?

[MiniDave]

I doubt it matters, even tho WillieB's done 30K on this motor, he's in the minority - most Minis are lucky to get 1000 miles a year, some are lucky to get 100.

But - since you have it - let's use it!   77.gif

Is it for an A+ engine?

Plus too and also, it's adjustable so I don't have to set the timing with offset keys. I wonder if there's a lock plate that the screws go into that goes under the gear too? I didn't see anything in the pics you posted.....

I seriously doubt these are interference engines, you'd need well over 1/2" of lift to clear the head. As for quieter - these engines rattle and thrash enough that I doubt you'd hear the difference, but I expect the belt will last longer than a chain - and belts don't stretch like chains do.

[cstudep]

It is a beautiful piece of kit there is no doubt about that

[Willie_B]

Rear of the cam gear. 

Is there a difference between A and A+ for that part?

[MiniDave]

Only in the cover design, the A+ engines have a kick out under the alternator for the timing chain tensioner - this looks like it's that style.

[Lone Star Mini]

Dave.. with your knowledge, I wish you created videos of rebuilding an engine.   I'm about to begin tearing my engine apart.   What I thought was a 1275 is actually a 1360 (I forget the exact numbers now).    I will have to follow this thread.... Oh Mr. Willie B is going to get a fabulous engine no doubt...