273 Commando Back From Machine Shop-Issues Continue....

[Bossanova5]

Picked up the pieces the other day.
The machine shop supposedly verified the bores and pistons were within in spec, even when I told them my measurements indicated otherwise.
When asked what the ring gap was they said .017"
I measured the ring gap as .034". Way out of spec of .010"-.020"
They honed the cylinders, but there is still a feelable ridge at the top of cylinders
They installed new cam bearings, but the oil holes in the bearing and the block are not lined up on three of the bearings.
All 8 valves leak on one head. and 5 do on the other head.
The crank and rod bearing clearance (The rods and the crank were ground at .010") came in at .0015" (Using Plastigauge) which is at least at the tail end of the allowable spec.

Pretty disappointing.....

 

[WV64Signet]

 

[Lefty71]

You have our sympathies for sure. Now the more brutal part; dont go back to that guy, period. Measure everything you can, yourself, even if that means buying better tools.
I'm hoping you can salvage the pistons (and bores) and move forward with some new rings.... i always gap them myself.
I love my machinist, but I do literally everything myself, that i can do myself....thats part of the reason i love the hobby, and it doesnt bite me in the tail, except the $$ lol.
Btw, you can buy a proper cam install tool and the proper mandrels from Speedway Motors.....dont buy that rubber grip crap....its ***.

 

[Bossanova5]

Needs new oversize pistons and rings.

 

[toolmanmike]

Needs new oversize pistons and rings.

And bored and honed to size.

 

[4spdragtop]

The cam bearings are fine. I was worried about an "offset" on ours as well. Showed my machinist(50 yr mopar guy) and he said don't sweat it. Sorry to read tho, very disappointing.

Picked up the pieces the other day.
The machine shop supposedly verified the bores and pistons were within in spec, even when I told them my measurements indicated otherwise.
When asked what the ring gap was they said .017"
I measured the ring gap as .034". Way out of spec.
They honed the cylinders, but there is still a feelable ridge at the top of cylinders
They installed new cam bearings, but the oil holes in the bearing and the block are not lined up on three of the bearings.
All 8 valves leak on one head. and 5 do on the other head.
The crank and rod bearing clearance (The rods and the crank were ground at .010") came in at .0015" (Using Plastigauge) which is at least at the tail end of the allowable spec.

Pretty disappointing.....

View attachment 1716421065

View attachment 1716421066

View attachment 1716421067

 

[GTX JOHN]

The cam bears are OK. They will be plenty of
oil thru that opening.

The ring gap @ 34 is certainly not optimal but will
run fine in a street application.

I am not crazy about a ridge in a fresh bore/hone either and you
wonder how good the job was otherwise.

If the pistons and rings were expensive, it "might" make sense to
find and prep another block even this late in the game.



Flame Away Everybody!

 

[Bewy]

It sounds like they honed the bores, which is what you asked for, no? If there is a ridge, that means there is wear. If you measured the ring gap near the top of the bore, then you will get a bigger gap. The ring gap with a block like this should be measured at the bottom of the bore where it is not worn.
I assume the rings were NOT ' file to fit', so they come with larg-er gaps. If they removed 0.002" for honing, your ring gap increases 0.006".

 

[Bossanova5]

I mentioned to the owner of the shop when I dropped it off that I had measured all of the bores and they were all out of tolerance, and it would need to be bored. He came back a few weeks later and said he measured everything and everything was ok. When I dropped it off my ring gap was .032" with new OEM rings. And yes, I measured the ring gap at the the top, middle and lower places in the bore. At no point was I able to achieve a ring gap between .010"-.020" in any cylinder. Pretty disappointing not only for the waste of money spent but also the time. The caveat, is that EGGE recommended this guy to me. Live and learn.....

 

[NC Engine Builder]

That is unacceptable work. I'd be really interested to see what the piston to wall clearance is, I bet its horrendous.

 

[XFX]

Can not defend the crap work but on the cam bearings it at times is a matter of splitting the difference in a crap casting and the core shift fight. This was ma mopars work here in these pics. But only you can tell if that was your case or they shop just sucks.

This motor actually ran pretty well with 106k miles and flaked out brittle oem cam bearings. Most were off a bit, worst block I ever seen for upper core shift.

I did slot the new cam bearings as needed but it would of still lived.

Sorry your not having the best of luck.

 

[Bossanova5]

By slotting the cam bearings? Do you mean you enlarged the oil holes in the new cam bearings to line up with the oil holes in the block?

 

[65TerrorCuda]

A machine shop did my cam bearings like that, but worse the cam was binding. Bought the tool and did it myself 100% right the first time. Made me wonder how in the hell can the pros screw it up if an absolute beginner can nail it without wasting a single bearing!

 

[Inertia]

We (and every repair shop in N America) did lotsa overfender overhauls, very common.
Valve grinds happened about 80k and re-ringing, cuzza smokey exhaust started about 110k miles.
Lotta folks couldn't afford or wouldn't pay the price of machine shop overhauls, and the overfender overhauls were 95% successful in most cases .

Factory service manuals include the procedure.

Here's the specs that Hastings supplied as guidance for a successful job.
I can tell you we did dozens of engines, some \6 Taxis we did 3 times and got 250k, no machine shop required.

I'd re-ring that puppy with those rings, gaps 180* apart at the wrist pin, and know it would be successful for another 50k for street use, and sleep well every nite.
I'd go after the ridge again now, if it is really significant, reamer shouldn't affect hone crosshatch.

Good luck. True experience.

 

[XFX]

Very true. Unfortunately things that many of us did in our youth that worked has been demonized in the days of the internet and yes some for all the right reasons.

Today they do make a fuss about taper and it killing the rings however this is illustration I think is also from Hastings and shows the ever changing gap with the increased taper. Say in maybe 86 I had an SD455 with .011 taper and the shop owner was a friend and fellow tractor puller and it was briefly mentioned and then we moved on. I ended up getting another 60k miles of hard street beating and weekend brackets and never had an oil issue. And yes, this re rung, high taper SD455 would do a number on my stock well running 70 440-6 Runner and a friends GS 455-1 and with a 3.42 gear would easily handle the 5.0 and GN-s light to light and on the interstate. Honestly them times were seemingly much more fun as we were all the captain of our own ship and not internet servants.

Those were the days of pre internet where if it ran when coming apart it ran with rings and bearings, cam ect.

I would not toss your stuff in the dumpster but rather maximize what you have and go have fun.

 

[Inertia]

Most common mistakes.
Not properly cleaning used piston ring groove, leaving carbon at the back of the groove.
The new piston ring can't move deep enuff, causing scuff and heat.
Not removing the cylinder ridge, and the new square edge of the ring slams into the ridge, often breaking the ring or ring land.

I know this cuz I took a lotta engines that were "overhauled" at home and didn't work-out, so the person went to Sears and bought a rebuilt engine.
Sears used us to install their engines, and these unsuccessful engines had new parts that just needed correct assembly. So I paid the core and took them home .

Cheers

 

[Swinger 340]

A machine shop did my cam bearings like that, but worse the cam was binding. Bought the tool and did it myself 100% right the first time. Made me wonder how in the hell can the pros screw it up if an absolute beginner can nail it without wasting a single bearing!

I new a guy who worked at a machine shop years ago, that installed disc pads backwards on a Chrysler at my shop. Your shop is only as good as the people working there.

 

[Inertia]

Very true. Unfortunately things that many of us did in our youth that worked has been demonized in the days of the internet and yes some for all the right reasons.

Today they do make a fuss about taper and it killing the rings however this is illustration I think is also from Hastings and shows the ever changing gap with the increased taper. Say in maybe 86 I had an SD455 with .011 taper and the shop owner was a friend and fellow tractor puller and it was briefly mentioned and then we moved on. I ended up getting another 60k miles of hard street beating and weekend brackets and never had an oil issue. And yes, this re rung, high taper SD455 would do a number on my stock well running 70 440-6 Runner and a friends GS 455-1 and with a 3.42 gear would easily handle the 5.0 and GN-s light to light and on the interstate. Honestly them times were seemingly much more fun as we were all the captain of our own ship and not internet servants.

Those were the days of pre internet where if it ran when coming apart it ran with rings and bearings, cam ect.

I would not toss your stuff in the dumpster but rather maximize what you have and go have fun.

View attachment 1716421342

In the pix XFX posted

This is a perfect example of how rings get jammed up after a valve grinds, and the carbon is scraped off the top of the piston, I used grease at the top of the bore to stop all that nasty crap getting behind the rings.

A lotta the carbon gets between the wall and piston, you blow or brush as much off as possible, but the crap you don't get out gets literally blasted behind the rings the first time that piston fires.
The piston is at top of bore where there is max taper, lotsa gap, then explosion blasts crap down behind ring, as piston moves down, taper compresses crap behind rings, the rings stick in compressed position, not sealing against cylinder wall, so of course, over fender overhauls don't work, lol, - re-rings on tapered walls don't work, -rofl .

Then there's the ring grooves that aren't cleaned sufficiently at rebuild, rings can't compress, scrub the walls, melt the rings .

Now you know why, and how I made a lotta pocket money selling re - rebuilt engines.

Good luck

 

[65TerrorCuda]

I new a guy who worked at a machine shop years ago, that installed disc pads backwards on a Chrysler at my shop. Your shop is only as good as the people working there.

I've seen that happen but I can't understand it. Wonder if they own up to their mistakes.

 

[Lefty71]

I've seen that happen but I can't understand it. Wonder if they own up to their mistakes

I found a set of pads installed backwards in a Bronco back in the 80's..... i said, "note to self; i guess thats possible" lol.

 

[65TerrorCuda]

I found a set of pads installed backwards in a Bronco back in the 80's..... i said, "note to self; i guess thats possible" lol.

I've messed up drum shoes before but didn't let it leave that way. Metal plate against the rotor! That's gotta sound terrible

 

[Swinger 340]

I've messed up drum shoes before but didn't let it leave that way. Metal plate against the rotor! That's gotta sound terrible

Yes, that was a tale-tail sign, the grinding. Lucky he only went a half block before coming back to the shop, saying the brakes didn't feel right. I have him remove the front tires (yes, both) and tell me what he sees. He said everything was done right. I had to point out the problem for him. He blamed it on Chrysler, for making the pads flat on both sides.

 

[Woody500]

Picked up the pieces the other day.
The machine shop supposedly verified the bores and pistons were within in spec, even when I told them my measurements indicated otherwise.
When asked what the ring gap was they said .017"
I measured the ring gap as .034". Way out of spec of .010"-.020"
They honed the cylinders, but there is still a feelable ridge at the top of cylinders
They installed new cam bearings, but the oil holes in the bearing and the block are not lined up on three of the bearings.
All 8 valves leak on one head. and 5 do on the other head.
The crank and rod bearing clearance (The rods and the crank were ground at .010") came in at .0015" (Using Plastigauge) which is at least at the tail end of the allowable spec.

Pretty disappointing.....

View attachment 1716421065

View attachment 1716421066

View attachment 1716421067

Else where on A-Bodies its been stated cam bearing holes can/are partially blocked(restricted) to ensure not too much oil goes to the valve gear.
So check further with those more knowledgeable than me to be sure if those are OK.
How were they previously installed would be a clue.

 

[Woody500]

I mentioned to the owner of the shop when I dropped it off that I had measured all of the bores and they were all out of tolerance, and it would need to be bored. He came back a few weeks later and said he measured everything and everything was ok. When I dropped it off my ring gap was .032" with new OEM rings. And yes, I measured the ring gap at the the top, middle and lower places in the bore. At no point was I able to achieve a ring gap between .010"-.020" in any cylinder. Pretty disappointing not only for the waste of money spent but also the time. The caveat, is that EGGE recommended this guy to me. Live and learn.....

Wider ring gaps are for Boost!

 

[Bossanova5]

The original chrysler oem cam bearing oiling holes were installed perfectly in alignment with the block oil holes.