94 mtx top engine knock? With video link

[Cole maclachlan]

If the car has this many miles, I would suspect rod bearings as well unless you know they were changed at some point

I think this can be possible. I am going to put it all back together and do some running tests.
Once I’ve done that I will disassemble again and dig deeper.
Thank you

 

[zoomlater]

I will say for an engine with 300K miles, the cams and inside surfaces looks pretty clean. The previous owner must have done regular oil changes.

 

[Dirty Harry]

I wouldn't think a cracked piston, as suggested earlier, would cause exhaust to blow back out of the throttle body. Although this is not the cause of the knock, it should be addressed. Do a compression and leakdown test. Could be cracked or worn valves.

As a side note. Yes it's a clean engine. I can recall as a kid in the sixties (1960's for the young crowd) pulling a valve cover off an engine that still used non-detergent oil. You had to scrape off an inch of mud & gunk to even see the top of the head. Thank God for additives.

 

[Cole maclachlan]

I will say for an engine with 300K miles, the cams and inside surfaces looks pretty clean. The previous owner must have done regular oil changes.

Yes it has been well kept for sure.

 

[Cole maclachlan]

Ok so I have found the culprit
Cylinder 6 crank bearing/ Babbitt bearing?

It was super loose I could move it with my fingers

The main nuts are off in this but it would do this before I took them off.

Now I am in search of new bearings which I haven’t looked to hard for yet as I have been super busy with work.

I don’t think my local parts store can get them but I will check soon.
I will also new dfront and rear main seals.

There weren’t too many shavings in the oil pan but the oil stank pretty bad

So here’s a question
The oil pan drain plug I couldn’t get off because the exhaust pipe cerise’s over and was right in the way.
Does the y pipe “upgrade” cross in front of the opdp? There is a rod shifter and the pipes go around it to accommodate. I just want to know if the y pipe is the reason why it crosses in front of the opdp.

Asides from that next step is
bearing (single) or all 6 replaced
Torqued
Gasket set/seals
Clean all the parts thoroughly
Back together
Pan
Exhaust
Starter
New oil
Filter

Then give her a run

Once that’s done and out of the way I will return to the top end and re do everything

Valve cover gaskets
Intake manifold gaskets
New plugs

Etc...

Also want to thank everyone for their input
It has helped tremendously in the search for what was wrong.

Much appreciated

 

[blk\blk90]

Wow. Yeah, I'd say that's what's causing your problem, how do the journal surfaces look? If they're gouged that's gonna be bad, as I dont think you can get oversize bearings. But, shosource has standard size in stock. For now.
http://www.shosource.com/catalog/product_info.php?cPath=61_43_48&products_id=256

 

[zoomlater]

Replace all the rod bearings.
Do you have an equal length Y-pipe (take a look at the picture on the Shosource website). That can get close to the oil drain plug and make it difficult to remove.

 

[luigisho]

If it's open replace them all. As mentioned above I would look a the rod and crankshaft mating surfaces. If they are mucked up the chances of replacement bearing failure in short mileage in that spot goes waaay up. If you can see and feel damage on the crankshaft journals or connecting rod bearing mating surfaces then you should replace those items or swap in a replacement motor

Don't chase your butt on this. You are talking about alot of maintenance work on an engine that may need to go. Assess that first.

 

[rubydist]

unfortunately, replacing bearings does not solve that problem - since the bearing spun, it wallowed out the rod end and likely messed up the crank journal too. I would be looking for a new short block.

 

[NoSlo]

Updates?

For bearings, rockauto.com - Clevite CB1435P x 6, with forum discount code.

Looks like they spun, from the radial wear on the connecting rod. There's not much edge keeping bearings on the correct side any more...

See that replacements bearings are flush with connecting rod cap top and bottom. If they don't line up perfectly flush with the finished mating surfaces and a machinist level or glass, that's a surefire sign that the connecting rod bore has been worn and dished from spinning.

An industrious person would get at least a replacement connecting rod cap. A shadetree mechanic might score or mar the old cap's surfaces across the spinning marks; scratches might keep the bottom bearing in place and distribute the scoring. Even lap fractions off the cap mating surfaces until plastigauge crankshaft clearance can be brought near max allowable.

Really up to you if you want a new connecting rod, (+ piston or pin with tool, rings and lip bore, ring compressor, etc) and head gasket now or later.

Clean up crank with a band of 600 grit paper. Assemble; connecting rod cap is first 26, then 36 ft-lb. Plastigauge with new bearings. Cross fingers. Use assembly pre-**** on the crankshaft.

(This thread is remarkable for such casual-ness opening up the top, front, and bottom, usually even exhaust studs are an annoyance.)

Connecting rod crankshaft journal - 51.976-52.000mm
Connecting rod bearing bore diameter - 55.000-55.016mm

Connecting rod bearing - clearance to crankshaft:
Desired: 0.024-0.056mm; Allowable: 0.08mm
(bearing wall thickness 1.484-1.496mm)

 

[Cole maclachlan]

Updates?

For bearings, rockauto.com - Clevite CB1435P x 6, with forum discount code.

Looks like they spun, from the radial wear on the connecting rod. There's not much edge keeping bearings on the correct side any more...

See that replacements bearings are flush with connecting rod cap top and bottom. If they don't line up perfectly flush with the finished mating surfaces and a machinist level or glass, that's a surefire sign that the connecting rod bore has been worn and dished from spinning.

An industrious person would get at least a replacement connecting rod cap. A shadetree mechanic might score or mar the old cap's surfaces across the spinning marks; scratches might keep the bottom bearing in place and distribute the scoring. Even lap fractions off the cap mating surfaces until plastigauge crankshaft clearance can be brought near max allowable.

Really up to you if you want a new connecting rod, (+ piston or pin with tool, rings and lip bore, ring compressor, etc) and head gasket now or later.

Clean up crank with a band of 600 grit paper. Assemble; connecting rod cap is first 26, then 36 ft-lb. Plastigauge with new bearings. Cross fingers. Use assembly pre-**** on the crankshaft.

(This thread is remarkable for such casual-ness opening up the top, front, and bottom, usually even exhaust studs are an annoyance.)

Connecting rod crankshaft journal - 51.976-52.000mm
Connecting rod bearing bore diameter - 55.000-55.016mm

Connecting rod bearing - clearance to crankshaft:
Desired: 0.024-0.056mm; Allowable: 0.08mm
(bearing wall thickness 1.484-1.496mm)

Thank you NoSlo
This I really appreciated
Updates coming soon guys
Sry have been slammed super busy working

 

[zak]

rod bearings. Has it been like that for a while? If not new bearings might save it. Depends on what the crank looks like.

 

[Cole maclachlan]

Alrighty guys

Sorry for the late update but have been working like a dog

I have cleaned out everything on the bottom end pretty good for inspection.
Nothing seems to be out of order in terms of cracks and excessive wear or damage.

I cleaned and inspected all the pan bolts and inner pan bolts as well as the oil pick up and the mains stabilizer pan and wrack with bolts.
Also cleaned and inspected the removed bearings (haven’t removed all of them yet) connecting rod caps and the starter. I don’t have a picture but I have found that the starter power connection post is stripped. Right into the base of the starter.

Thanks for the tip NoSlo Totally didn’t use the promo code as I’m new and didn’t know where to find it lol


Don’t pay no attention to the oil as I’m only going to use this cheap stuff to give the engine a thorough clean with some cleaner and then dump it for some good stuff.

I haven’t pulled the trigger on putting everything back together as I am still waiting for a couple gaskets ( oil pickup/ front and rear oil pan rubber gaskets) plastigauge pre-**** and some 600+ sandpaper for the journals.
Oh and an oil filter can’t forget that

Once I have everything I need I will be preforming most of what @NoSlo has posted
(Thanks a bunch )
I have never used plastigauge but I will do some research before hand. Any tips will help.

I will be attempting to do all of this from underneath the car (bottom end) while the crank and pistons are still in the engine.
From my guestimations it is doable.

My shifts at work have turned into nights which makes me a zombie ‍ and it is hard to set the body back to days which puts me all over the schedule map.

It will be done sooner than later.

Thanks again for everything.
much appreciated

 

[Irish Pride]

Can you feel any damage on that rod journal? If so, you are going thru all this for nothing. If the journal is messed up the crank is toast. Run your thumb nail across it. If you feel ridges, it's done.

 

[NoSlo]

Can you feel any damage on that rod journal? If so, you are going thru all this for nothing. If the journal is messed up the crank is toast. Run your thumb nail across it. If you feel ridges, it's done.

Not toast, the crank journal(s) would just need to be turned for .25mm undersized bearings. You can verify you got undersize bearings, because they will have black paint on the side instead of orange. Still available here: https://www.amazon.com/Clevite-CB-1435P-25MM-Engine-Connecting-Bearing/dp/B000C06ENA

Toast from a financial standpoint, maybe.

If the plastigauge on the inside of the bearing of both top and bottom squish to within clearance, even closely examining for low width areas from scoring, chances are good it shall run fine, (or spins again, no loss). Check bearing wear pattern & replace bearing 10K later after it has broken in the crank.

Maximum allowable 0.0031 on SHO - plastigauge squished to at least the .003 width:

 

[Cole maclachlan]

Can you feel any damage on that rod journal? If so, you are going thru all this for nothing. If the journal is messed up the crank is toast. Run your thumb nail across it. If you feel ridges, it's done.

Thank you @Irish Pride i will keep attention to each journal.

 

[Cole maclachlan]

Not toast, the crank journal(s) would just need to be turned for .25mm undersized bearings. You can verify you got undersize bearings, because they will have black paint on the side instead of orange. Still available here: https://www.amazon.com/Clevite-CB-1435P-25MM-Engine-Connecting-Bearing/dp/B000C06ENA

Toast from a financial standpoint, maybe.

If the plastigauge on the inside of the bearing of both top and bottom squish to within clearance, even closely examining for low width areas from scoring, chances are good it shall run fine, (or spins again, no loss). Check bearing wear pattern & replace bearing 10K later after it has broken in the crank.

Maximum allowable 0.0031 on SHO - plastigauge squished to at least the .003 width:

This is great
I have gotten these exact bearings.
I will have to pick up some plastigauge for sure
Thank you @NoSlo

 

[NoSlo]

This is great
I have gotten these exact bearings.
I will have to pick up some plastigauge for sure
Thank you @NoSlo

--- Luckily, you didn't, you got the correct ones from RockAuto. The last link, in my reply just to Irish Pride, is for undersized bearings - the -.25mm in the part number. They would destroy your crankshaft.

If the crankshaft has been quite damaged, as revealed by the plastigage showing too big a gap, then the only option is to have it turned in a machine shop. Only then would you use the undersized bearings

If the plastigauge shows the gap is too big, it is up to you if you still want to re-assemble anyway and drive until it goes sho-boom.

 

[NoSlo]

I don’t have a picture but I have found that the starter power connection post is stripped. Right into the base of the starter.

This can be fixed by replacing just the starter solenoid, which is available at Advance Auto with at least a 20% discount code anytime ("PS20" is the discount code they give when their website doesn't work), when you order for store pickup, for under $15.

Here's a thread where I describe how to work on the starter: https://shoforum.com/index.php?threads/howto-starter-motor-rebuild-and-replace-brushes.134666/