New drivetrain for my 1973 1200 Honda Civic Rebuild

[Steph]

The last thing you need is to get pulled over by the police for blowing smoke, because they'll send you down to Regency where they'll go over it with a fine tooth comb. The other issue is if a motorist decides to report you the police, not to mention the damage you're doing to the environment. :?

[RTR75]

Andreas,
Glad to see you back.

Sorry you have to swap engines, but you have a spare to begin with is good. :o

When you pull it down, yes look at the head, valve guides and seals but…
This has always been the rule of thumb, if you are smoking more so on deceleration this is a sign of valve seals. The engine is creating more vacuum sucking the oil down the valve.

As opposed to what you are saying, more smoke on acceleration. This is sure signs of the piston rings not sealing properly and oil is being left on the cylinder walls and being burnt in the combustion chamber.

One thing I don’t think was asked, did you have the cylinders bored over size?

8) Linc

[ASM]

Andreas,
Glad to see you back.

Sorry you have to swap engines, but you have a spare to begin with is good. :o

When you pull it down, yes look at the head, valve guides and seals but…
This has always been the rule of thumb, if you are smoking more so on deceleration this is a sign of valve seals. The engine is creating more vacuum sucking the oil down the valve.

As opposed to what you are saying, more smoke on acceleration. This is sure signs of the piston rings not sealing properly and oil is being left on the cylinder walls and being burnt in the combustion chamber.

One thing I don’t think was asked, did you have the cylinders bored over size?

8) Linc

Yes, glad I still have to other engine. parts like that are increasingly rare - no more CIVICs on the scrapyards here!

to your question: yes, cylinders bored and new oversize pistons + rings were put in. Together with new bearings top and bottom of the rods.

One more thing about the smoking: After driving about 10ks with the engne nice and snug warm the smoking almost stops. It's like being switched off.

And there is one thing I have had in the back of my had nagging ever since. When I put the engine back together, or rather when I put the camshaft in, I noticed that on two of the long bolts the thread was mangled, flattened. I got a couple of other bolts from MikeS and all was well, but I kept thinking how or why those bolts were damaged. So far I don't know.

But now my scenario, and it mainly involves the head.
- oil is seeping into the inlet somehow. valve seals are new so they shouldn't (well..) be the trouble. When engine is started in the morning this would have happened all night with the oil initially warm and thin.
- on starting that oil is burned making smoke.
- smoking on acceleration is because enriched mixture is flowing around the valves taking up oil on the valve/stem into the chamber
- smoke taking off at the lights, similar cause and at idle vacuum is highest so more oil is sucked in
- smoking stops at warm engine. Now this one has to do with the mangled bolts. Somebody fiddled around with the engine and mucked something up when putting the head back together. Don't know what but as a consequence the head fractures. Now when the engine is cold the fractures open and let oil seep in (e.g. overnight) once the engine warms up the metal expands, partly closing the fractures.

Question: would a fracturing somewhere "in" the head, e.g. around a valve stem "hole", not going through to the base of the head or the valve seat go undetected when the head is pressure tested? I had the head pressure tested when I hade it machined and new valves put in and nothing showed up.

[Bill]

I think that Linc nailed it, rings. But even if that is true, you are right to pull it down and inspect everything. Good luck, and have fun with the swap.

[RTR75]

Hey Andreas,
"I" don’t think "buggerd" bolts are a concern, a crack in the head letting oil in...doubtful.

Another question to go with your theory, :roll: did they replace the valve guide? if they did check to see if one is loose! A loose guide would explain your theory, if not the lower end will have to be gone into.

When you pull the lower end down, after checking for proper installed rings, also check the piston ring end gap, don't recall the specs at the moment should be in "The Book"

When they bored the cylinders it is possible that they wear given the wrong size rings. This too will cause your symptoms

Happy engine swapping!

8) Linc

[Gusto]

I'll check the engine receipts for if the guides were replaced next time I'm over where the car is.

https://www.1stgencivic.com/forum/viewtopic.php?t=15411
Continuation of this car's development is (as owner has changed, thought it best to give it a new thread).