Chopperharris

Hi

I’m in the process of rebuilding the engine of my 82’ 4.5 Euro (I’m in the UK). All bores look good except one which has 1x score line about a hairs depth which you can catch your nail in. The car is a slow burn resto project and was saved from the crusher - as a result I can’t confirm what the oil consumption was like prior to it being taken off the road. I did do a compression test when I got the car and this cylinder (no 4) was about 20% below the highest and 10-15 below the rest (hopefully that makes sense). I’ve not removed the pistons or split the case yet so I don’t know if a broken ring is the cause, however the top of that piston is slightly more pitted than the others - nothing major but a difference is perceivable.
I’m interested in thoughts as to what I should do from here on? Some previous posts suggest ignoring minor scores whilst others suggest relining or replating ... I’m aware of the difficulties of boring/rehoning alusil.

Thanks in advance

pic below

Kiln_Red

What initially prompted the desire to rebuild the engine? Were there known or suspected internal coolant leaks? High oil consumption? Or was the engine an entirely unknown commodity and, as such, was cause for enough motivation to want a fresh starting point? Most importantly, what are your expectations for the whole restoration project? Clean driver? Concourse?

icsamerica

No way that small score could cause a 20% drop in compression. If you look close there are 5 other small lines. Something scuffed the bore in that area so that hole needs to be refinsihed at the least. Has to be something else going on. I would take the piston out and have a closer look and repair or replace as needed.

The next step is to evaluate the depth of the largest score and take some careful measurements of the bore and piston. Most of it may be able to be honed out and perhaps you would end up on the larger end of allowable bore tollerance. That would be a best case scenario.

If the largest score is deep and you want it done right then you will need an over bore and piston at best and a replacement block at worst.

GregBBRD

You need to remove that piston and see how much damage there is and what caused it.

Then you proceed, from there.

Jason89s4

^^^^ What Greg said.
Because, I also agree it is not just that score causing compression deviation.
-Jason

C531XHO

What they said

My S2 block had scoring which came from a broken ring.

Chopperharris

Thanks all - plan to continue the strip down tomorrow so will see what else could be causing. I suspect broken ring too. I’ll also do some measurements of the bore etc.
What’s your option on having just one bore relined as i’m not sure who there is locally who can do the correct Alusil honing?

Chopperharris

Hi
Engine was an unknown and had been parked up for 8 years. I was expecting badly corroded heads and nonexistent head gasket! Neither was the case which was good.
Intention is to get somewhere between clean driver and concourse - not looking to win shows but want it done right.
Thanks

C531XHO

I had bore damage on my S2 but that was obviously from a broken ring. I didn't bother pulling anything as the block had other issues.

Biggest pain for you will be removing the crossmember to gain access to pull the sump and release that piston but hey your sump gasket will need to be changed anyway. Guarantee it's leaking...

David

Kiln_Red

Sounds like work!

I say set the head back on to properly pull the engine. Re-evaluate after you get it on an engine stand.. if the engine isn't out already.

Chopperharris

Thanks David - i removed the engine this weekend just gone so no issues with access luckily. Sump already removed and hope to get time over the weekend to explore further by removing the offending piston.
Did you end up replacing your block?
cheers

C531XHO

I got a good spare shortblock and then bought anothet S2 which actually turned out to be perfect engine wise internally. I sold the original S2 as it was stored 500 miles away but i kept the good spare engine in case I need it. Also bought another running car which makes me more patient when repairing the non runner

Chopperharris

👍 Excellent!

Chopperharris

I’ve removed the pistons and whilst there are a few marks on the piston from cyl 4 the rings are fine. I can also assume some crap got into the engine at some point in the past.
I’ve not taken the valves out of the head but will do later this week before sending them off for a light skim and checking/replacing guides etc.
I’ll get the machine shop to check out the bores and give me options. Looks like my next job will be removing the studs then!

Any comments and guidance welcomed.

Cheers

Kiln_Red

Soak those head studs in the best penetrating oil you can find. Double nut method works well for me after a few days of soaking and re-applying penetrating oil.