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Morris

Morris

Yoda
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Well I got everything working GREAT with my fuel injection set up, and now I have blown the rings on number 2 piston. I am smoking up the highway and blowning about a 1/2 quart out of my pan on my 8 mile drive to work.

I don't have the time, money or resources to pull and rebuild the engine right now. Even suggesting such a thing would surely result in my wife hitting me with a rolling pin. So I am wondering if I can do a kind of poor mans overhaul on the car: pull the pan and the head and remove the rods/pistons with the engine still in the car. I could then replace rod bearings (the ones I have now are still pretty good, so I don't think any grinding will be neccessary) and replace the rings with these

https://cgi.ebay.com/ebaymotors/MG-Midget...1QQcmdZViewItem

These rings are .020" over. Does this mean I need .020 pistons to go with them, or are they designed to work on the stock pistons?

The cylinder walls looked pretty good the last time I pulled the head. Could I just use one o' them stone hone thingermabobs on them?

I really need to keep the car on the road for a little while longer while I finalize the details on the fuel injection system. Once I have something that I can put on the market, I can get a small business loan and invest in making my car something that can be shown off in magazines and car shows. Or possibly buy another car that is already nice.

Any advice or opinions will be greatly appreciated.

morris
 
Oh god, oversize rings = oversize pistons.

Can't pull pistons with engine in car to my knowledge. Least I never could.
 
It is possible to pull the head and oil pan on the 1500 and change the piston rings when the engine is in the car.
When it comes apart, you *must* measure the bore and see what they are. Then buy piston rings that will fit those bores. If the cylinders are badly scored or grooved they must be re-bored (which means the engine must come out).

If the bores look smooth and measure to a correct size (standard, or +.010 or +.020 or +.030 or +.040) , you may be OK to replace the rings to the correct size.
You can only put +.020 rings on +.020 piston in +.020 bores.
You cannot use those e-bay ring unless you have +.020 pistons and bores already.
Using a glaze-breaker (thingamabob) is fine, but clean up all the grit carfully before reassembly.
If you do this, you should also check the ring gap. Put a ring in the cylinder (without the piston), be sure it's "square" in the cylinder, and measure the ring gap. Should be around 0.008" or so, but you could get away with up to about 0.015" in a pinch.
 
What about clearances on the Main/Rod bearings? If you change the rod or main bearings, don't you have to make sure there is still about .0010-.0020" (depending on the manual's specs) clearance or it will starve for oil?
 
I can't recommend anything first hand but take a look at this page https://www.teglerizer.com/triumphstuff/75w_newrings.htm It is a very non-conventional approach, but if it means being able to nurse the car until you can do a proper rebuild you might think about it. Just be mindful that you may have a catastrophic failure if your piston is too loose in the bore. It may go against every proper thing you are supposed to do but....
Chris
 
[ QUOTE ]
What about clearances on the Main/Rod bearings? If you change the rod or main bearings, don't you have to make sure there is still about .0010-.0020" (depending on the manual's specs) clearance or it will starve for oil?

[/ QUOTE ]

Correct. But when Morris measures the crank journals, he will be able to see what size they are. If they are within spec of "standard" (or a "standard oversize") he can install appropriate-size bearings. If they are way-off of any standard size, then a re-grind is needed. Obviously, no one should attempt any crank brearing replacement without careful measuring. I'd double check things using Plastigage as well. And personally, I'd renew the thrust washers too.

But I think Morris's original question was regarding the rings and an "economy rebuild".
 
How stupid would it be to reuse the rod bearings I have now?

They seem to have no play in them.
 
Not stupid at all if they are ok, i.e. not worn worth talking about.
 
Just check their clearance before you decide to reuse them
 
I just went through this with my Cortina 1500 MKII GT.
Was going to do an "economy" rebuild,but after I got it into
the machine shop,we found out that the cam was flat,& the tappets were worn out.
I decided that it was cheaper in the long run to go ahead & do a major rebuild (thanks Visa).
It's cheaper to do it right once,than to cut corners twice.
What I'm saying is,think about it carefully before making a (possibly) bad decision.
My 50 Pence worth.

- Doug
 
"thanks Visa" Uhhhuh. That hurts after a while. I tend to wait until I have cash. But the sentiment works for me. Do it right the first time. /ubbthreads/images/graemlins/laugh.gif
 
[ QUOTE ]
Can't pull pistons with engine in car to my knowledge.

[/ QUOTE ]

Why not? I can't think of any reason why you can't (on a A series anyway). Take the head and sump off, take big end cap off and push the con rod and piston up the same way as you would if the engine was out of the car.
 
It is a very low mileage engine that ran super strong before a supposedly new (thank you eBay!) fuel pump caused a super lean condition at wide open throttle, so it is possible that all the other stuff is still okay. Of course, everything will be checked while I have the engine all apart. Also, I am already quite beholdin' to Visa for my fuel injection project ( I went over my orginal budget by... oh it's too painful to even say ). I would like to do all I can to avoid debter's prison.

Thanks for the tip on Plastigauge, Nial. That stuff is cool! Can anyone reccomend an affordable tool for measuring cylinder bore?

Thanks for all the great advice, guys!

morris
 
Might be able to rent a mike from an outfit like Nations rental??
 
You know, if you were running supe-lean, you may have burned a valve.
We did this in our 1275 race car last Fall (we found later that it was running 18:1).
At the last minute, we had to use my #11 to run the 4-hour night event because the 1275 was only running on three.
Sometimes, a cylinder with a burned valve will call unburned fuel to create smoke (from excess unburned gas washing the cylinder walls). Valve job is easier than doing the bottom-end.
 
All will be revealed when the head is pulled. And that may not happen for a while. *sigh*
 
Morris, a simple leakdown test will differentiate between a burned valve and a bad piston or rings. And, if necessary, a telescoping gauge, and a 2"-3" micrometer should be adequate to determine the bore size. You can get a cheap set of 1" to 3" mikes that read to .0001" for less than $75, and probably 20 bucks for the gauge.
Jeff
 
Burned valve, busted piston... either way the head has to come off and the wallet has to come out.

Oh woe is me!
 
Shoot burned valve less than 100 bucks till running. And that is if you have the machine shop repair it. Fast too. Tear down one day and back up the next.
 
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