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MG Midget and Sprite Technical - 1975 engine compression test

I have just checked my engine compression after a run it heat it up. I get 145lb on #4, 128lb on #3, 120lb on #2 and 140lb on #1. I turn over engine with gas pedel press down and cranked about 10 times. From what I understand there can only be about 10-15% between each cylander.
Does this indicate and overhaul?

Dick Bishop
RC Bishop

How many miles on the engine?? Doesn't sound awful, just bad enough to wonder about the head gasket integrity between cylinders 1 and 2...?

R
Richard 1979 1500

I got to agree with you richard, Id say give it a retorque, probably wont work, but you never know,,,,got nothing to loose by trying...besides Ive heard of worse,

If any thing have a shop do a leak down test,and stick a vacume gauge on the intake manifold...that would certianly narrow it down.

prop
Prop***The End in 2012

There are 93k on the engine (if you can believe the odometer). There could have been work done as the there is no play in the thrust bearings. The oil pressure is about 50lb after a hard drive in the summer at 60 mph and drops to about 15 at idle. I was thinking that it could be a head gasket also.
I have to pull the engine as the transmission needs to be overhauled so I could do what other work needs to be done.

Dick Bishop
RC Bishop

Dick. If I were you, I'd do the compression test again and then I would add some engine oil to the cylinders, say a couple of tablespoons or so. Crank it over and compare the readings to each other.

The test is known as a dry and wet compression test.

If the readings come up because the oil acts as a sealer it's worn rings, if they remain the same, it's bad valves.

In this case, there seems to possibly be some problem between the 2 and 3 cylinders. Retorquing just might cure the problem but there is even a possiblity (slight in my opinion) the head might have warped. Have you over heated the engine or anything?

Clive Reddin

Sence restoring the body I have only driven it about 300 miles (Summer of 08). It did not over heat on any of the drives that I took. I don't know how it was driven before I bought it. Just had a list of the maintance completed.
Tomorrow I will check to head bolt torque and then do a dry/wet compression check.

Dick Bishop
RC Bishop

You say the engine's coming out to get at the transmission anyhow. In which case an inspection and a new head gasket are not that hard to do.

Ant
Ant Allen

Checked the torque on engine today and found head bolt #2 would not torque down, removed nut and bolt and found that the nut was bad, stripped out. also found bolt # 4 also loose but could be torqued.
The bolt on # 2 looks good so will get a new nut and try again.

Dick Bishop
RC Bishop

Hey dick,

Id get a new stud and nut...make sure they are grade 8 or better, dont use reg. everyday hardware off the shelf...most likely this is the problem of the hardware that wont torque down

If your cylinder head is held on by "bolts" and not studs and nuts, you may have a problem, if thats the case, Id certianly go ahead and get a new H.G., and do what ever refreashing to the head thats needed...like, no lead exhauste seats, valves and seat faces re-cut, new guilds and seals, magnifluxed for cracks ect. ect. (oh and yes get the proper hardware made for the head and engine.)

But im guessing what your calling a "bolt" is really a nut....a common typing mistake....dont worry we wont laugh at you to loud...after all, I can barely spell....so your well ahead of the game....LOL.


Prop
Prop***The End in 2012

Your are right it is a stud that I removed. I am going to pull the engine to do a transmission overhaul so I will replace the stud and nut at that time.
Hey everyone, thanks for the great help and responses. This is the greatest forum on midgets on the internet by far.

Dick Bishop
RC Bishop

Dick (greatest forum)

yes, we think so too, some of the best people on the planet live in here.

If you are pulling the engine, replacing the head gasket will be a minor task within that job so you may as well do it properly. Studs, nuts and all.

Do keep us in the loop, we feel that we are collectively keeping cars running on all of the continents here with our interaction. Yours is part of our family now, you too.
Bill sdgpm

This thread was discussed between 19/02/2009 and 20/02/2009

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