Triumph Repair: Engine smoke after new pistons, triumph spitfire 1500, hatch pattern

Question
QUESTION: I have a 1974 Triumph Spitfire 1500. I just had the heads redone by a engine machine shop. I put new pistons, rings, timing gears, and chain in. The engine starts up and seems to run great but I'm getting a lot of smoke from the exhast. In checking the plugs they are black with carbon but not wet. The compression is 110 on each cyclinder. Any ideas on what could cause this problem?
Thanks
Bill

ANSWER: Hi Bill,
The color of the smoke tells what it is. Black smoke is excess fuel. Blue smoke is oil and white smoke is coolant.

If your plugs were flat black powder, that is a second indicator if the smoke was black too that it is a fuel problem. (Too much fuel)

If the plugs were wet sooty black that is an indication of a fouled plug and/or oil burning if the smoke was blue.

The compression test of 110 PSI is very poor for a fresh rebuild. Who put the pistons and rings in? The machine shop that did the head? Were the cylinders rebored?

Howard

---------- FOLLOW-UP ----------

QUESTION: Thanks for responding Howard,
The smoke is blue in color and you can smell it. I put the new pistons in I order the standard size, I gapped the rings according to the sheat that came with the pistons .015, I think I indexed them properly. I did not have the cyclinders borded, althrough I used a cyclinder tool to put new cross hatch pattern on the cyclinder walls. The machine shop that rebuilt the head informed me that if this engine smokes it isn't coming from the heads. Not sure how to prove that one. I have about 60 miles on the new pistons and rings. Do you think I should drive it a little more?

Thanks
Bill

Answer
That sounds like you did that correctly but you didn't say anything about getting the scraper ring/s up right or up side down. Most scraper rings (second ring down) are angled and slide over the oil on the way up and scrape the oil down to the oil ring on the way down. Some pistons have more than one scraper ring and some even use the top ring as a scraper. The dot close to the end of the gap MUST face up. Some don't put a dot but place the size close to the end gap (Std., .010,.020 etc.)

The standard method to separate oil burning from valve guides or rings is a large puff of blue smoke every time you start the engine and the smoke mostly goes away after that is valve guides.
Blue smoke on acceleration is for sure rings.

Putting new pistons and rings on a used bore (even honed) will smoke for some time because the bore is not perfectly round and the rings need about 500 to 1000 miles to seat in to the used bore.

Another problem using a used bore with new pistons and rings is the time that it takes to seat in will cause a lot of blow-by into the crankcase causing crank case pressure and that can make the oil rings not work effectively and thus burn a lot of oil. On many used engines the mesh in the box in the valve cover that has the case vent needs to be cleaned as it gets coked up over the years and does not allow good case venting. Most are sealed in and difficult to clean. If you have that type of vent you should take it to a shop or machine shop and ask if they have a way to clean the mesh. Some machine shops have a vat they can soak it in.

A dry then a wet compression test may show a problem in the rings.

Read my tech tips on engine rebuild. http://mg-tri-jag.net/Preamble

Howard