Head/Piston Damage Continued

[Jdddrigot]

Much thanks to everyone for their input and suggestions. I’m learning a lot and am thankful to have this forum. With that said what is my best path forward?  At this time I only see used pistons in the correct bore on EBay and custom forged pistons from IE. Any other suggestions?  My dad was a machinist at AMC making crankshafts for 30 years. He had a way with words, none of which are politically correct. I’m guessing he would have sent me to the boneyard for an engine. Kinda pass that point now. 

[TobyB]

I'm sure there are one or 2 out there,

 

but I've never seen a 'good, used' piston come

out of an M10.

 

Boring a 4 cylinder block's actually pretty inexpensive-

and just like there are no good used pistons, the M10 block

NEVER needs anything more. (for a street car)

 

Likewise, 98% of all 'unfailed' cranks can run with just a polish.

 

Bore it, new pistons, a refreshed head, and you have an engine that

will run for 200k, and give 'new' power for 120k of that.

 

t

 

[Jdddrigot]

6 minutes ago, TobyB said:

I'm sure there are one or 2 out there,

 

but I've never seen a 'good, used' piston come

out of an M10.

 

Boring a 4 cylinder block's actually pretty inexpensive-

and just like there are no good used pistons, the M10 block

NEVER needs anything more. (for a street car)

 

Likewise, 98% of all 'unfailed' cranks can run with just a polish.

 

Bore it, new pistons, a refreshed head, and you have an engine that

will run for 200k, and give 'new' power for 120k of that.

 

t

 

Thanks. Where would you suggest buying pistons from?

[Conserv]

1 hour ago, Jdddrigot said:

Thanks Steve. I do appreciate an opinion more informed than mine. Right now I’m only finding used pistons in the correct bore on Ebay. Would you install used with new rings?  What are my other options?  Kinda how I’m feeling at the moment -

New rings on used pistons would be preferable assuming the used pistons were still within factory specs. And if a used replacement set of pistons is not within spec, whether you (a.) use new rings or (b.) re-use old rings, you’re going to be back in the soup shortly! Your engine is tired: I’m guessing it has more miles on it than you know. I see that the head, cast March 1976 (3 nubs surrounding “76”), was replaced previously. It’s not clear if the bottom end has been rebuilt. The answer is probably no if the bores are still 89 mm. 

 

Has your mechanic measured the bores to see whether they will clean up with simply a honing, i.e., without over-boring them? I’m a bit incredulous that the collapse of piston #2 didn’t leave some damage in the cylinder. I’d want a good mechanic or a machinist to examine all four bores, to determine what it would take to completely clean them up. Honing? Maybe, but not likely. First oversize? Much more likely. A very good set of used piano tops, particularly in first oversize (approx. 89.22 mm.) or second oversize (approx. 89.47 mm.) would allow you to overbore all four cylinders to match the new pistons and start fresh. And, actually, new 8.3 piano tops tend to sell much cheaper than their high-compression cousins (9.0 and 9.5).

 

If I were in your shoes, I’d slow down the process and start shopping (including German eBay) for a set of piano tops in the 8.3 compression ratio. This would be after determining whether I could run standard size pistons, or would require over-boring. I’d look at used and new examples. But I’d check out the availability and pricing of new piano top pistons at the usual suspects: Walloth & Nesch, Blunt, Maximillian, etc. Remember also that when you buy a set of new pistons, it generally comes with rings. And they all work, and are within spec.

 

Alternatively, I’d consider looking for a good used engine and simply store your old block, assuming it’s original to the car — crazy car nuts ? do remove good engines at times, just so they can replace them with great engines!

 

I’m hoping / assuming this is not your daily driver. If that’s correct, time is your friend to find relatively rare parts!

 

But the cheapest solution is often not the... cheapest solution. Take your time and think carefully about this.

 

Regards,

 

Steve

 

[Son of Marty]

New rings for sure and hone the cylinder walls to the ring manufactures specs.

[tech71]

34 minutes ago, Jdddrigot said:

Thanks. Where would you suggest buying pistons from?

Do you have a replacement head for your hosed cylinder head?

 Find a good head first then go on a piston hunt. 

I believe you mentioned that you are ok with lower comp ratios?

That increases your possibilities a bit,  you could use a later E21 head with flat top pistons.

Decreases your Comp Ratio from 8:3 ( E12 head, low piano pistons) to 8:1 ( E21 head, flat top pistons)

Not much difference and given the probable condition of the rest of your engine, the slightly lower 8:1 compression would still be an improvement.

 

Get your block bored and fit new pistons, replace that head with an overhauled one.

Its going to cost a few $K but if you have a financial advisor, it should be easily within reach.

 

Welcome to the Vortex.

Edited May 6, 2021 by tech71

[Jdddrigot]

56 minutes ago, TobyB said:

I'm sure there are one or 2 out there,

 

but I've never seen a 'good, used' piston come

out of an M10.

 

Boring a 4 cylinder block's actually pretty inexpensive-

and just like there are no good used pistons, the M10 block

NEVER needs anything more. (for a street car)

 

Likewise, 98% of all 'unfailed' cranks can run with just a polish.

 

Bore it, new pistons, a refreshed head, and you have an engine that

will run for 200k, and give 'new' power for 120k of that.

 

t

 

Thanks. Where would you suggest buying pistons from?

[tech71]

13 minutes ago, Jdddrigot said:

Thanks. Where would you suggest buying pistons from?

Again... What cylinder head will you be using? Surely not that chewed up aluminum ingot  candidate that came off?

 

Edited May 6, 2021 by tech71

[Jdddrigot]

Ok, I’m half laughing, half crying. Yes, it’s my daily driver. PO had the head replaced.   My mechanic is saying the current head has been saved (or as he really said, “you have enough money into the head”).

 

Here’s what I’m thinking. Have the block checked by the machine shop. Look for appropriate size piano pistons based on cylinder appraisal. Tell wife she’s covered for my birthday and Xmas for the next 10 years. Keep telling my financial advisor it’s an investment. Maybe I don’t retire in two years like I had hoped. Get an electric bicycle.  Start taking more cues from my dog -

[tech71]

You do have another option not yet mentioned.

Unload it and walk away...

Thats probably what your dog would do ?

 

I found no new or NOS low comp pianos in my quick search.

Edited May 6, 2021 by tech71

[Mark92131]

47 minutes ago, Jdddrigot said:

Where would you suggest buying pistons from?

 

Budget piston option for E12 Cylinder head.

 

Mark92131

 

https://www.ebay.com/itm/261435360374?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

 

[tech71]

I know that there are custom made pistons also available, some folks here have gone that route.

My machinist here mentioned it to me so is probably pretty mainstream. Cost? No idea.

 

I have been playing the Piston game for about 3 years, spend too much time looking/buying online for NOS pistons/sets mostly on Ebay. A weird obsession .

 In that time, I recall seeing 1 set of NOS low pianos in standard size (not good) and 1 single NOS low piano in second oversize. 

I have bought 3 sets of NOS pistons  in 3 years but none are suitable for an E12 head.

Afraid in your situation, time really does equal money

Edited May 6, 2021 by tech71

[jimk]

20 hours ago, tech71 said:

Decreases your Comp Ratio from 8:3 ( E12 head, low piano pistons) to 8:1 ( E21 head, flat top pistons)

I have std vbore flat tops that have less than 80k miles on them from my one owner engine.  I want to measure the ring side clearance to see if they are in spec.

21 hours ago, TobyB said:

but I've never seen a 'good, used' piston come

out of an M10.

Maybe what mine will have some life left in them.

The whole set can be had for not much more than one new piston.

[Squid's 02]

Drop a used engine in the car so you can get back to driving. If you can't find one locally, post in the WTB section.

 

Determine what your goals would be if you rebuild your current engine and start sourcing the parts required for the build. If you are really 2 years away from retirement, maybe this becomes one of your first retirement projects. And when you are done with the build and install the fresh engine, you get to sell the used engine that kept you going for a couple years and recoup some funds. 

 

 

 

 

 

 

[jimk]

So I measured the ring side clearance with the feeler gauges I have on 2 sets.

Spec 1st ring 0.0024-0.0032 inches; 2nd ring Mahle 0.0012-0.0024 inches, 2nd KS 0.0016-0.0028 inches

Measurements: Mahle flat top, Std Size <80k street miles - 1st ring 0.003" goes, 0.004" no go, 2nd ring 0.002" goes, 0.003" no go

 

KS Bathtub Std Size <500 street miles - 1st ring 0.002"goes, 0.003" no go, 2nd ring 0.0015' tight go, 0.002 no go.

 

Both sets the ring grooves are within sped as best I can measure.  The KS bathtubs are virtually new so it is expected the side clearance is less.