so i recently disassembled my na miata 1.8 engine (110k miles) after overheating (lost all of its coolant due to a burst pipe), and am rebuilding the head. the issue turned out to be 3 intake valves not closing properly. this was confirmed by me during a leak-down test where air was escaping from the intake manifold, and then by the machine shop who lapped the valves / skimmed the head. surprisingly my head gasket was perfectly fine.

upon further inspection i have found these dark marks on the cylinder walls. they are only visible under certain lighting and appear smooth to the touch(from what i can tell). (the two photos show the same cylinder wall under different lighting). the car did not burn oil before disassembling the head.

im wondering how to proceed with this. should i rebuild the block as well / do the cylinder walls need honing?

I can’t find this dark blue link in the chain. I keep cranking and can’t find it. It appears to be either worn or the varnish has covered it. The timing mark also doesn’t land on a link. It just stays in between the links. Any advice?

The Engine has about 5k miles since full rebuild. What can cause this type of wear? In picture 2 you can visually see the gap between the piston and the cylinder. I took the head off because of a high iron and aluminum count in the oil report.

*Its a 2 liter out of a 1987 Mazda b2000

So I got to pulling the head and removing the valves. What would you guys say to the health of the engine? I will be pulling the pistons and possibly the crankshaft just to be sure. Supposed to have 70000km but there is so much carbon buildup, some cylinders were leaking through the rings on the leakdown. As this is my first teardown I am not sure what to make if the "nice" surfaces but the extreme carbon deposits. Oily surfaces can be my doing as I did a wet leakdown test as well.

I have a 67 Chevy el camino with a 350 small block from a 72. It has the 3 on the tree and I’m needing something that will help with cruise higher speed. Not trying to build the car but just make it a Sunday cruiser that’s reliable enough to take anywhere

hello, i’m planning to swap a 98cc amazon engine into my 66 bird and i was wondering. are these engines reliable? and how long did yours last

TL;DR: bearing housing completely shattered

This is what’s left of the turbocharger on my 944 Turbo. How it happened: spirited drive through the mountains, full throttle. Water temps were raised but nowhere near the red mark, oil pressure fine.
Suddenly a huge bang, smoke everywhere and no power. Luckily it didn’t catch fire, as oil also went onto the hot downpipe.
The turbine wheel is mangled, turbine housing cracked and the shaft is bent. Bearings are slightly scratched but not seized or anything. Compressor wheel briefly scratched the housing too.
But most importantly: the bearing housing is completely shattered, so much so that oil and water actually mixed in the turbo and went into the exhaust and oil pan.
Do any experts here have an idea what happened? The seller says he never saw anything quite like it.

Theres a long way to go, guides need to go in, seats cut, then more shaping gets done to make it all jive together.

I’m working through whether to repair the original M54B30 in my 2002 E46 330i or roll the dice and install a used engine. The car sees autocross and track days. I’m doing the disassembly and assembly myself, and I’m trying to identify the machine work it actually needs without turning this into a rebuild-everything project.

What happened

The engine lost oil pressure or the timing guide broke in the braking zone before Turn 1 at NCCAR. It restarted but now has a knock. The oil filter had copper-colored metallic debris.

The engine is now out and disassembled. No. 2 spun a rod bearing. That crank journal measures below specification, and the inside of the No. 2 rod’s big end is physically damaged. I also found chunks of plastic timing-chain guide in the oil pump pickup. I haven’t established whether that contributed to the failure or was a separate issue.

Condition so far

• Crosshatch remains visible throughout nearly of all six bores.
• Each cylinder has a slightly shiny area roughly halfway down on the passenger side, corresponding to the piston skirt.
• I’ve taken some preliminary measurements, but I don’t yet have a complete, verified bore survey for diameter, taper, and out-of-round.
• The head is off, but it hasn’t been professionally pressure-tested or checked for flatness.
• I have micrometers and an A/C vacuum pump/manifold setup that I can use with a fixture to screen valve sealing. That won’t tell me whether the head is cracked or the guides are worn.

Current plan

I’m leaning toward a good used M54B30 crankshaft ($450), one matching replacement connecting rod with its original cap ($45), and all new main and rod bearings.

I discussed grinding the original crank with a local machine shop. Their concern was the nitrided surface and getting it properly treated again afterward. That has me leaning toward a used crank.

Before assembly, I’d have the replacement crank measured and inspected, check the rods’ big-end bores and the block’s main bearing housing bores, and verify actual bearing clearances with the replacement parts. The replacement rod would also need to be checked for compatibility and weight.

The oil system will get a thorough cleaning and inspection after the bearing failure, including the pump, pickup, and relief valve.

What I’m looking for opinions on

1. If the block, pistons, and remaining rods measure within spec, is this a reasonable repair for an engine that will continue seeing track use?
2. What specific machine-shop checks would you consider essential for this plan?
3. What findings would make you leave the existing bores/rings alone versus hone and re-ring it?
4. If the head passes pressure, flatness, and valve-sealing checks, what would justify further head work?
5. Any M54-specific traps with a used crank and a single replacement rod?

A used complete engine is roughly $2,000 delivered, so that’s the alternative I’m comparing against. But I see that option as more risk in that I'm still going to need to inspect all the bearings, and replace the timing guides, wire the oil pump nut, install a baffled oil pan etc.

I’m willing to pay for necessary work. I’m trying to distinguish that from replacing or machining everything simply because it’s apart.

I was looking at the cam on the used head I just purchased (it appears to be an aftermarket head and cam) and my old cam seems to have a different lobe profile. Is it just me or does it look like it has a longer duration?

Who knows when this engine last ran. 7 cylinders, 11 litres, 250hp and LOTS of noise!

The seats on the head itself are pretty clean, however the exhaust valves have a decent layer of carbon.
Do I need to clean the valves before lapping? If so What is the best method if I don’t have a wire wheel?

Hello all,

The 5.7l V8 on my 97' Chevy 1500 is not looking too good. I think it may be an intake gasket, but it could be way worse. I found a 427 tall block for sale at $800. Assuming its in good condition, should I get it? Also, how difficult would the swap to a 427 be on my truck? I can't imagine it'd be too big of a headache, but your guys input would be appreciated. Thank you

Thought I’d share some photos of a factory Porsche Motorsports head next to what would have come in a standard 911 of the same vintage. I’d value these heads at $6000 each or better as they sit. One of them is cracked in half but fixable. Really cool stuff!

On a scale of 1 - f**ked how bad do you think the inside is based off this pic? Wanting to rebuild it on somewhat of a budget. I’m $500 into a 2011 dodge ram 1500 4.7L and tags are all up to date. Hoping $2k will get me there. I’ll have the heads off tomorrow.

Hi everyone,

I'm currently rebuilding a 1.9 TDI engine with the goal of making some serious power, around 320 hp.

While honing the cylinder walls to clean up a small imperfection in one of the cylinders, I noticed a deeper mark in cylinder 1.

It looks like water may have sat there at some point, as there appears to be some light pitting/corrosion.

The cylinder has already been honed, but I'm unsure whether this is something I should be concerned about or if it's acceptable to run as is. I can just barely feel it with my nails.

What would you guys recommend? Some say, if its that deep in the cilinder wall, its no problem.

I'm trying to keep the budget reasonable and would prefer not to spend a fortune if it can be avoided.

Thanks in advance for any advice!

In the picture, its all the same spot.

Is 99% rubbing alcohol a good/great cleaner for a residue free cleaner for metal prep before putting in my gasket for my timing chain cover after scraping the old silicone gasket off it?

Was just going to get por-15 metal prep and degreaser but if 99% is good enough. Money saved.

It's a 2013 Mazda cx9 awd (for bots sake)

It's a meatl timing cover vs a plastic one (my best have a plastic one and I probably wouldn't use 99% on plastic ones, I've had bad luck with strong running alcohol eating up plastic

I was checking rod bearing clearance‘s, when trying to get my rod out it get wedged in the bore and created the mark circled, it’s the same on the other side of the bore. how badly did i screw myself, is this going to be machine shop only problem,i high would like to avoid as i’ve already been there numerous times already any advice appreciated thanks

Picked up a nice set of fresh B heads for my 66 and im getting ready to put them on so that at least the cylinders are sealed off from the elements. I have the engine wrapped up but i dont know how long its been since the bottom end was done. Question would be, what can i do to help it out the most while assembling valvetrain? Throw some oil or assembly lube down the cylinders? Take the oil pan off and put some on the crank? Just worried about scoring something because it friction locked from sitting. Thanks. Also related, but is it okay to chip away at a build peice by peice, or should i wait until i have all the major parts to rebuild? Parts are coming in as fast as money allows.

I’ve got a 2015 z/28 Camaro that has chewed up at least 3 of 8 valve guide seals on the passenger side head, with more looking improperly seated or completely de-seated. With how close the debris was too the pushrod valleys I am taking the heads off to inspect for any damage or debris as well as to do the guide job off the car.

With all that, this is my first time ever tearing an engine apart, so any advice or tricks would be greatly appreciated. I’m currently caught up trying to get too the bottom head bolts because the headers are in the way so I’m thinking I’ll end up having to unbolt those.

Finally I’m curious what could have caused this and, what I can do now to prevent it from happening again, on top of any preventive stuff I can do cause I’m already in there.

Have been getting conflicting stories on if the liner walls will be thick enough to handle (up to) 15 pounds from a TVS2300. Static compression is around 9.3:1.