Head/Engine repair

[230slhouston]

Hi Experts.
I am in the process of stripping my car for painting...taking longer than I thought. One of my tasks was to remove the head and replace valves/guides. etc. Why? When I used to dive it,  it smoked at start up and during acceleration, after idle. I did the valve seals once, in situ. The exhaust valve  seals where out of the guides....possible loose guides. After replacing, no smoke for a few runs. It returned after a while and the seals popped again. Hence my plan to recon the head.

My dilemma...i removed the head. There is some piston play in the bore, slight. I have not measured the bore as yet. I was thinking of removing the engine, replacing  mains/big ends and rings maybe polish the crank. I had no intention of doing all of this. Oil pressure was max on cold start. When warmed up, it was mid range on idle 1500rpm. Max on on acceleration and driving.
Car has 80000 miles. Engine number is not stamped, assuming it was changed at some point. Has to be prior to 1975, i have repair receipts from PO since 1975.

Will I get away with a set of rings....as i open up there is no end to where to stop, my wallet is though  
 Anyone just did a ring job without new pistons? Any suppliers who stock rings?

Thanks folks.

[ctaylor738]

Here are the choices I made.

Car #1 was a 280SL with 239K on the original engine.  It ran OK but had the same smoking issues that you describe.  When I took the head off, you could see and feel the ridge at the top of the cylinders.  It was a terrible car with a lot of badly repaired rust, and I didn't want to put a lot of money into it.  So had the head rebuilt including new guides and put it back together.  It ran fine for four years, including a 600 mile freeway trip to a friend's beach place and a trip to Maine.  

Car #2 was a 230SL with a destroyed crank (run out of oil).  I bought a used 230 short block that really didn't look any worse than the 280, but on the advice of the machine shop, went ahead with a full rebuild.  The pistons were hard to find, and very expensive.  Back together, the car ran OK, but not any better than the 280.  The mistake that I made with this car is that I bought all the parts from Metric Motors and had a local shop do the work on the short block, so I saved a couple of hundred bucks mainly due to not having to ship the engine to Metric, but ended up without a warranty.

In the course of figuring out what to do with car #1, I asked about new rings.  One place recommended Sealed Power rings, which were supposed to be designed to conform to cylinder walls in situations like this.  There was other advice to the effect since there was no obvious scoring or other cylinder damage, that I was better off to leave it alone.

It always comes down to the condition of the car, your plans for it, and money.  If it's a nice car, and you are going to keep it for a long time and are comfortable with the expense, my advice would be to go with a short or long block from Metric and be done with it once and for all.  Otherwise, just rebuild the head.

Cheers,

CT
 

[Shvegel]

Pistons should rock a little at the top if the bore is cold.  Since the majority of the aluminum is in the top of the piston it is machined smaller than the skirt(bottom) of the piston to allow for expansion of that mass of aluminum at the top of the piston when it is hot.  If there isn't a noticeable ridge at the top of the cylinder you are probably OK.  Deves should make stock bore rings for your car. 

More common is the problem of the valve guides coming loose in the heads and moving up and down with the valves.  I would suggest having the head gone through and replacing all the guides with the newer stepped guides that can not sink down into the heads. if all the guides are tight and there are no "Smoking guns" then I would start looking hard at the lower end.

I had exactly the same symptoms as you and the fac that the seals are popping off or more likely driven off when the valves guides went down leads me to think your problem is most likely in the top end.

[230slhouston]

Thanks CT and Shvegal for the replies. Exactly what i was thinking, needed some reinforcement. I will not replace rings and risk putting in new rings and interfering with the current seating.

I do all my own removal and installation to stripping the engine and reassembly.  I am am planning on removing the engine and replacing crank seals, sump gasket, polishing the aluminum and doing cadmium plating. All items removed, ready to lift out this weekend.

Follow up question, does it make sense to put in new mains and big ends? Was thinking of a new oil pump as well, any way of testing this?  Labor is no issues to remove and do a total rebuild in a few years. Any thoughts here?

I am spending decent money on the paint job and interior.

Thanks
MBP

[ctaylor738]

From what you said about oil pressure and miles on the engine, I would leave the bottom end alone.  My 230 core engine, despite cylinder wear, did not need any work on the crank and the bearing replacement was a "might as well" sort of thing.  The oil pump was re-used and worked fine.

Cheers,

CT

[ja17]

Most likely your engine will do fine with just the head work at 80,000 miles. Oil pumps have gotten extremely expensive over the last few years. If you you start making big expensive decisions like that you may as well go the whole re-build.

[230slhouston]

Thanks everyone for your input. I guess it will just be the head recon and all the seals. I did whip out the engine and tranny as part of the paint job. Did it all my self so it is just labor and beer at this point.
Getting ready to send part for cadmium plating.

MBP

[George Des]

With the engine and transmission out and the head off for reconditioning, IMO a big part of the job is already being done. A crankshaft regrind with new bearings is something the machine shop would do as would a rebore. The driver in doing a rebore would be the availability and cost of the oversized pistons. Ten years or so ago these were available and not outrageously expensive. Not sure about now. A new timimg chain and oil pump IMO is cheap insurance and on of those things that is easy to do at this point of disaasembly. When I rebuilt my engine over 10 years ago, pumps were under $200. It may also be a good opportunity to check the condition of the clutch assembly while these items are accessible. You can see how some of these jobs rapidly start snowballing, but accessibility for alot of these jobs is much, much easier if you are at the point you are right now