Bb140a blowby problem

"Gentlemen
I have enjoyed the

"Gentlemen
I have enjoyed the sight for several weeks now, and have came to the point I need the help of the forum. I have done a search and read all the pertinent volvo postings.
I am having oil being pulled into the carbs at medium to high rpms.
History: Rebuilt this motor about eight years ago. Bored to .5mm oversize, new pistons, rings, bearings, swaopped to two solex downdraft carbs.
Performed two compressionm checks, hot and cold. Psi ranged from 155 to 175. Engine cranked and otherwise ran well. Headbolts were all tight, headgasket was good with no identifiable problems to my eye. Valves look in good condition.
My questions are, with compression this good, can the rings be worn out?
If the valve guides are bad, how can I tell this?
El Pescador suggested marinizing automotive motors in an effort to repower. I an not clear, but will A B20, B21, or B23 automotive engine work? If I was to ask for a motor at the wrecking yard what exactly would I ask for?
Thanks for you insight and help!!
Pops86"

"Wayne,

1) Regarding y

"Wayne,

1) Regarding your first question, the answer is: yes, they can be worn or even broken. A compression test tells you only one part of the story, but a leak-down test will tell you where there is loss of compression (e.g. piston rings, valves, etc) and even how bigh is the leak. Leak-down tests have been discussed before in this forum.

2) When valve guides are worn, the usual symptom is high oil consumption. However, the exhaust gas pressure is generally too low to cause any significant blow-by through valve guides.

3) Your engine has a B21 block, and the direct automotive replacement would be and engine pulled from a 1976 to 1982 240 Volvo."

"Thanks for the timely respons

"Thanks for the timely response. I must admit for all the mechanical work I have done, I have never heard of a leakdown test. I searched for the previous posts and downloaded the info to make and do them. I can understand the value they can be in diagnosing problems.
Trouble is, I have already removed the head from my 140. Would it be stupid to reassemble the head and perform the test?
As far as high oil consumption, this engine does not use much oil other than what it has pulled in the carbs.
An engine from a 76-82 240 volvo may be difficult to locate around my area.
The oil pressure in this engine has been good. Would it be dumb to mic and rering if feasible, put in a new oil pump, new gaskets, and run it??
This old bayliner is not much, but has given much pleasure just boat riding, knee boarding, and shrimping over the years. I just do not want to put in several thousand dollars in a repower for a 86 model boat.
Thanks!!"

"Wayne, I think it is cheaper

"Wayne, I think it is cheaper to reassemble the head and do a leakdown test than just taking everything apart, provided you didn't put too many hours on the engine since rebuilt. However, if the engine is tired, you may want to measure the cylinders and see if you can get away with re-ringing, or whether you need a new engine. If you can get an automotive engine in good condition for a good price and marinize it, you can probably get a few years of service out of it."

"I would try to rering, and re

"I would try to rering, and rebuild....WAY CHEAPER!!!!! (in the long run)"

What max rpm do You obtain?
S

What max rpm do You obtain?
Sometimes the problems You describe may be 'solved' by change of propeller and make the engine get to the higher limit of allowed rpm at max speed.
Another might be the oil quality You use. Are You running mineral or synthetic?
When de-glazing/boring be sure to use a low grade oil the first 20 -50 hrs so the rings seat as quick as possible. Using a high grade oil at run in might ruin the whole job as the rings does not wear in properly.

"Do as Morten suggests, and de

"Do as Morten suggests, and definately look at the cylinder walls."

"In the early 90's Volvo b

"In the early 90's Volvo began recommending 20W50 for the 4 cyl, OHC. Synthetic is not necessary. Most so called sythetics are made from something called "hydro cracked or hydro dewaxed petroleum", a class of refined but otherwise common oil. Mobil I is a true synthetic but much too low in vis for a high speed machine like the AQ 140."

"I appreciate all the comments

"I appreciate all the comments. I have had trouble logging in to respond, but here goes. I have ran a 14x17 ss propeller for several years and have recently replaced it with a same size aluminum. The engine ran well, usually cruising between 4000 and 4500rpm. It top ends at 5300rpm. Like I said in my original post the oil problem has gotten much worse. I have used 10w40 valvoline oil for several years. What do you mean by a low grade oil for breakin if I am able to rering??
I have re-examined the piston tops and cylinder walls. I can see no visible problem with them.
To get an idea of the condition of the cylinders I mic'ed them as close to the top of the piston as I could and at the top, about a half inch down. If I understand right the block was bored to accept .5mm oversize pistons, meaning the bore should have been 3.6417" The biggest measurement in any cylinder is 3.6430" or .0013" wear in the cylinders. Taper at most is .001"
If I understand correctly, the maximum tolerance for wear is .0025", piston to cylinder bore clearance. I re-examined the head and can find no visible problems. I will find a marine head service shop to look at it for me.
I am going to pull the engine so I can remove the pistons to mic them so I can see exactly how much wear I am looking at, and the condition of the rings and existing ring gap.
Any thoughts would be greatly appreciated!!"

"There are 'break-in'

"There are 'break-in' oils available that has NO additives. This is mainly used by engine manufacturers at initial test of engines in the factory. Some cars are delivered with it from factory, and has to be changed rather quick in time.
When rebuilding, use Molycote on bearings and do the first hours of run in with a single grade , 'cheap' oil."