Engine Overhaul

[Tim]

GOt 2 engines that need help. I have some questions before tearing them apart.


It's been determined that my Blue Festiva needs a rebuilt carb, new rings, head gasket, and some other misc stuff.

Here's the questions I have about this engine:


Can the overhaul be done without removing the engine from the car?

Is the process fairly simple and straightforward?

What should I do if cylinder(s) are out of round? A rebore and oversized pistons are out of the question. Is it possible to get oversized rings or something to overcome this?

--------

My Red Festiva has a seized engine (girl driver... :roll: ). It basically spewed its guts all over the engine bay.

Assuming the block and head aren't cracked or warped (unlikely, but there's still that possibility), how much work is involved in getting this engine running? Am I better off just going to the junkyard and finding another engine?


Also, is there a specific loosening/tightening sequnence for the head bolts?



Regards,

Tim

[FB71]

ok, re-ringing is fairly simple. Yes, it can be done in the car. You'll need to remove the head and pan.

before describing the process, let me answer the out-of round question.
first, I've found these engines to be almost un-naturally durable. unless something catastrophic has occured, I doubt the cylinders will need much attention. Therefore, you should be installing standard size rings. What I have found, is that Mazda (along w/ everyone else at the time) was using newly formulated low-tension rings, to help increase fuel economy by reducing parasitic internal friction. Obviously, the rings do not retain their tension well, which leads us to current situation.
If the cylinders are excessively scored, tapered, or out of round, the only repair is overboring.

Now, once the head and pan are off, remove each of the rod caps and extract the piston and rod from the top of the block. The rod cap may not want to come off. Use a PLASTIC hammer to GENTLY tap up on the rod bolts to break loos the cap. Once the cap is off, put some rubber hose/ vinyl tube over the bolts to prevent scratching the crank. Push the piston up out of the block with a hammer handle, wood stick, etc. Make sure to keep the same cap with the rod, and oriented the same way it was removed. Yes, these things have a front and back. If you mix them up or turn them around, your engine will go BOOM, no joke. Remove the old rings by spreading them with your thumbs and lifting them straight up. DO NOT walk the ring around the piston. This will cut and or roll the edge of the ring land, allowing unwanted ring flex when running, which will ruin the cylinder. Take an old ring, pull it apart until it breaks, and use the broken peice of ring to GENTLY scrape any carbon out of the ring lands. Be careful not to remove any metal. Failure to remove the carbon will cause the engine to sieze when warm, due to the carbon expanding behind the new rings. Install the new rings the same way you removed the old ones. Take care to ensure the ring end-gaps do not line up with each other. Meaning, the oil ring(bottom), the scraper(middle) and the pressure(top) end-gaps all point in different directions. Before installing the piston, use a cylinder hone to 'break the glaze', or re-hashmark the cylinder walls. This promotes seating of the new rings. After honing, wash out the cylinder with warm water and dish detergent. I know that sounds wierd, but it works best. Dry the cylinder, and wipe with a clean, oily paper towel. DO NOT use cotton rags. Their fibers are to difficult to break down, and can actually damage the pistons and rings. Install a new bearing shell in the rod, making sure the bearing seat in the rod is surgically clean (no dirt, oil, etc), pour oil over the rings and piston skirts, and install a ring compressor on the piston. They have an up and down also, check the tool. Orient the piston with the notch facing the passenger side. Using the PLASTIC hammer again, gently tap the piston into the bore. If it stops, DO NOT hit it harder! Chances are one of the rings is catching the edge of the bore. Hitting it harder just destroys the piston. Reset the tool and try again. After its in, clean the cap, put a new shell in it, put the cap on, and TORQUE it, no guessing! Do the same for the main bearings, but only do one at a time, to prevent mixing up the caps. To get the bearing shell in the block without removing the crank, use a small screwdriver and carefully push the bearing shell and rotate it out of the block. Clean everything with brakeclean, and put the new one in, reversing the procedure.

Cylinder head torque sequence is easy. There's 10 bolts. Start with the two in the middle, back one first. Then do the two just to the right, the the two just to left. Then the outer right two, then the outer left two. Removal is the opposite.

[Tim]

Thanks, Jim!

What do you mean by "caps"? I don't think I've ever run into that term before.

Can I remove the head with the intake and carb still attached?


To overhaul this engine, I plan on replacing:

All gaskets (kit from Northern Auto)

Rings

Water Pump

Crankshaft Bearings.


Am I overlooking anything?


Regards,

Tim

[aithanmier]

so i take it the rods are powdered metal with cracked caps like ford uses on the mod motors? that would explain the orientation being critical...

[Tim]

Well, the teardown begins tomorrow after work!

My first issue is getting the exhaust manifold cover off. Would it be easier just to unbolt the pipe where it joins the cat, and lift the section of pipe off still attached to the head?

How heavy is all this going to be? Can I remove the head and all the other stuff attached to it by myself?


Regards,

Tim

[aithanmier]

the head and intake won't be too heavy to do by yourself.

[Tim]

Thanks!

As far as the connecting rod bearings go, will I be OK if I order standard size ones?

Since the engine still runs, doesn't overheat, and the compression is OK in some of the cylinders, will I likely be able to avoid having the head and/or block machined?

Regards,

Tim

[FB71]

Thanks!

As far as the connecting rod bearings go, will I be OK if I order standard size ones?

Since the engine still runs, doesn't overheat, and the compression is OK in some of the cylinders, will I likely be able to avoid having the head and/or block machined?

Regards,

Tim

standard size should be fine, as long as the crank looks good. If its damaged, it will need to be machined (unlikely)

the block should be fine, but I would have a valve job done as well as new valve stem seals.

[FB71]

so i take it the rods are powdered metal with cracked caps like ford uses on the mod motors? that would explain the orientation being critical...

actually, orientation on all rods is critical, not just on powdered metal/cracked cap rods.

the caps and rods are flat ground at the mating surface, bolts installed, cap assembled to the rod, torqued, and finish bored and honed as an assembly. Unless you're having the rods resized, you need to keep the caps in order and in the correct orientation.

[FB71]

you can leave on the intake and exhaust manifolds, but get someone to help you lift it. You can do it by yourself, but expect a sore back afterwards. If you can get the exhaust off, its a hell of a lot easier.

[Tim]

Thanks everybody!

When I yank the head off, can I reuse the gasket temporarily in order to get from the parking lot to my friend's garage?

Any advice on ridge reaming and cylinder honing?

I figure that I'll spend $150 overhauling this engine - a very reasonable price considering that I'd pay twice that for a used engine in dubious condition at the junkyard!!!


Regards,

Tim

[FB71]

I highly doubt there will be a ridge at the top. these blocks have a high nickle content. When you pull the head, you will see a black ring sround the top of each cylinder. Its carbon. Use a scotchbrite pad and carb cleaner to remove it.

For honing, I use WD40 as a lubricant and detergent. Buy it in the gallon jug, you'll use a good deal, and its cheaper that way. you want the crosshatching pattern to be at about a 60 deg angle to one another, or 30deg from level.

How far is your friend's shop? Are you driving it there before you re-ring? I'm a little lost here.....
Its never a good idea to reuse a head gasket....

[aithanmier]

hey jim do you know of any goo aftermarket rods from another application that would fit? i'd like to go with some nice forged i beams, but would rather not go the expense of full custom. i'm doubtfull, yet hopefull lol.

[FB71]

corksport.com

they have high strength B6 rods, which are dimensionally the same.

price was reasonable, if I remember correctly. (less than $300 for 4)

[Tim]

How far is your friend's shop? Are you driving it there before you re-ring? I'm a little lost here.....
Its never a good idea to reuse a head gasket....

I was planning on doing the work in my friend's garage (not mechanic's place). He lives about 1/2 a mile from where the car is parked. I thought I might do it at his house for convenience's sake, since we are neighbours.

Or would I be better off driving about 15 miles to the mechanic's and doing the work there? He'll let me use his tools and shop for free. Since it's in South Houston, I'd be closer to DJ if I really screw things up and need help...

This car is unregistered and uninsured, which is why I'm a bit leery of driving more than a few blocks in it.


Anyhoo, what is a reasonable price to expect for a valve job if I bring in the head already disassembled? Would purchasing new valves (Northern Auto has them cheap) lower the cost even more?


Regards,

Tim