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AQ 131 A275 Cylinder Head exhaust port

J

Jim G

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"I have a 1986 AQ 131 A. This

"I have a 1986 AQ 131 A. This has been a great little engine for the past 5 years. Last year, I developed an exhaust leak around the exhaust port on #4 cylinder. This resulted in the engine overheating unless I ran with the engine cover off. Figuring I had a hole in my exhaust manifold, I didn't tackle the problem until this spring. I removed the exhaust manifold and discovered a piece of the exhaust port on the cylinder head has either cracked away or corroded away exposing what looks like an iron ring that lines the exhaust port and a 1" X 1/8" crack behind it where the exhaust is escaping. Any attempts to seal up the crack by brazing have been unsuccessful. I am not particularly skilled in that area. Plus, it looks like dissimilar metals. The ring inside the port appears to be ferrous metal and the cylinder block aluminum? I've priced new cylinder heads and they cost more than the boat is worth. Anyone have any ideas?"
 
"It seems to me that the head

"It seems to me that the head has been repaired before. You can take the head to a shop and either ask them to TIG weld the port, then machine it, or to make another insert. However, if you wish to keep the boat for anumber of years, I suggest you sould get an automotive head from an autowrecker. The heads that will fit your engine should be from a Volvo 240 years 85-93; or a Volvo 740 8-valve, years 85-92. You will still have to use your current camshaft, as an automotive camshaft will not work on a boat."
 
"I think I see ..... are you s

"I think I see ..... are you suggesting the ferrous metal insert was placed there to seal up a previous crack in the port, or is that a normal component? Maybe I can get by with inserting a longer sleeve?"
 
"The head is aluminum, and por

"The head is aluminum, and port #4 tends to corrode on OHC VP engines; it is the closest to the exhaust and therefore the closest to the water. Installing a steel insert is a common type of repair, and another one is to build up the head with aluminum via TIG welding. You will have to check with a machine shop whether or not installing a longer sleeve is feasible."
 
Change the head and transfer t

Change the head and transfer the cam. Easy fix.
Gotta watch for the heads with the holes for the injectors. May be a problem.
The heads are out there. just gotta hunt.
 
"If the heads have holes for i

"If the heads have holes for injectors, just seal them with RTV sealant or a cap. Easy fix.
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"
 
"OK. I went out on a limb and

"OK. I went out on a limb and gambled $100 on an '88 240 cylinder head on eBay. Now that it is here, I see the casting numbers are different. I have 1000531 on the boat and 1000530 in the box. I'm guessing the one I bought is for a smaller displacement engine. Is this still going to work?"
 
"Eric,

Change the head and

"Eric,

Change the head and transfer the cam? Is that really all? No need to change the pistons or springs? Just curious, because I'm about to do just that.

Thanks,

Chris"
 
"Smokediver, there is no diffe

"Smokediver, there is no difference between "marine" and "automotive" heads, except for the camshaft. Just make sure you get the correct one."
 
"One last check ...... I'm

"One last check ...... I'm considering taking the new cylinder head to the shop to have a valve job done. They look OK, but I'm not equipped to inspect them correctly. Since I am using this head for a marine engine application, are the automotive valves OK for this application?

So thanks to everyone for your input and advice. I'm thinking this is going to be an OK outcome. I've only pulled a cylinder head once in my life, but I have my Clymer manual in hand. Just a little worried about keeping the timing from getting screwed up."
 
"The automotive valves will be

"The automotive valves will be fine. And don't worry for the timing; if you screw-up you cannot damage the valves, as the engine is non-interference."
 
"So, I picked up a used cylind

"So, I picked up a used cylinder head today. It had about 87K miles. Car was rear ended. Not mine, the one the head came out of. Anyhow, it had a very nice coat of varnish. Almost looked like copper. Thank goodness for part washers and all those chemicals that make up the Superfund sites. I removed the automotive cam, transferred the water temp sensor, a couple of threaded plugs, etc... Bolted in the marine cam and voila!, nothing. The cam wouldn't turn. So, in my infinite wisdom, I decided to get a chain wrench to turn it. Big mistake, well, maybe not big, but really stupid. I ended up shearing the freakin' locater pin for the cam sprocket. So, off to Volvo of Annapolis tomorrow to pick up locater pin. Um, do you have to turn the crank in order to turn the cam? As in reinstall it before you can turn it? I know some cams come with areas that you can slide a wrench over to turn it while it's out of the engine, but not in this case.

One thing I did notice, I might have to drill a hole on the air intake side, lower right corner, for the coolant. The marine head had a big hole, then it seems someone filled it and drilled it to make a smaller hole. The automotive head does not have a hole at all.
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Well, that's it for today. Stupid locater pin.... Stupid me and my chain wrench...

I'll post again tomorrow

Chris"
 
"Chris, it is possible that th

"Chris, it is possible that the cam did not turn because of one or several valves being stuck. In any case, nex time try installing the timing gear, it should move by hand.

I recall my AQ140 head had a hole drilled on the aft side, but not on the forward side. I guess it is just to get the intake manifold warm so that the gas does not liquefy when running the engine in very cold weather."
 
"El Pescador,

I made sure a

"El Pescador,

I made sure all the valves were free while the cam was out.

Timing gear? I'm not sure about what your referring too. Can you show me a drawing?

About the mysterious hole. I don't need to drill another one. I looked at the intake manifold where the "hole" would be and it's solid.

Thanks,

Chris"
 
Timing gear. Got it. Item #7

Timing gear. Got it. Item #7. That is the sprocket I was referring to. The small rolled metal pin that keeps it from rotating is what sheared.
 
"I'm not worried about mes

"I'm not worried about messing up the valves. I'm more concerned about putting the thing backtogether and having it run lest I screw up the timing by installing the marine cam improperly or not aligning timing marks and belt, etc. Slapping in a new cylinder head may be an easy fix for most, but I'm mechanically challenged. That said, I'm too cheap to turn this one over to a mechanic. It sits right on the edge of "I can do this"."
 
"Well, I found a locater pin.

"Well, I found a locater pin. Volvo wanted $1.50 and 10 days to ship it, Volvo Penta wants $1.05. Home Depot sold me 2 for $0.56. Go figure. HD calls it a tension pin. All different sizes, including the size needed to fit into a camshaft.
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Anyhow, the cam is turning like it should and it's all bolted back together (to factory specs, of course). I'll put the peripherals back on tomorrow (i.e. alternator, heat exchanger, carburetor, etc...) and crank her up. Hopefully she'll start. I'm kind of in line with Jim G, hoping that the thing starts when I'm done. With any luck, I'll be in the water on Sunday.

Hasta mañana,

Chris"
 
"Hi all,

I'm trying to

"Hi all,

I'm trying to reinstall the timing belt so I can put finish putting the engine back together. I know how the cam and intermediate shafts line up, and they do, but but for the life of me, I can't find anything on the crank sprocket or anything on the block for it to line up with. Do I need to pull the crank pulley off? If so, how do I keep the crank from spinning?

Thanks,

Chris

PS - Does anyone have a picture of what the timing marks look like on the crank. Thanks"
 
"Chris, there is a timing mark

"Chris, there is a timing mark in the crankshaft front seal housing and another one (a notch) on the crankshaft gear inner guide plate. No need for a picture, you cannot miss them. However, you have to remove the 6 screws and then pull out the crankshaft pulley to see the marks.

To keep the crankshaft from spinning (or to move it) use a deep socket and either a ratchet or a break bar."
 
"Hello again,

So the engine

"Hello again,

So the engine is almost back together. Everything except the heat exchanger tank. I didn't want to put it back on and fill the system until I was sure it would run. I can't seem to get it to turn over. It has fuel, it has spark at the end of the compression cycle via the new PerTronix module. I'm not sure what to do next. It doesn't seem to want to crank. Any suggestions you all may have to help me out are very welcome.

See ya,

Chris"
 
"By the way, I never did find

"By the way, I never did find the timing marks on the crank. I just moved the #1 Piston to TDC. I assume that's what the purpose of the timing marks are in the first place.

Chris"
 
"If the engine does not start,

"If the engine does not start, make sure your distributor is not 180º off. You may be getting the spark at the end of the exhaust cycle instead of at the end of the compression cycle. If you get spark and the compression is good, it can be only fuel, ignition timing or valve timing.

I still think you should have removed the crankshaft pulley to verify the timing marks, but it is your call."
 
"Hello All,

She cranked and

"Hello All,

She cranked and purrs like a kitten!! Had to do a preliminary timing set because I don't have access to a timing light here at the firehouse. I also have a small raw water leak coming from the gasket that connects the exhaust manifold to the outdrive, but I'll look at the tomorrow. Other than that she's running great. I ran her for about 30 minutes, temperature hung around 180 or so (which is good with a 180 thermostat, haha). Can't wait to put her in the water to make sure she doesn't overheat while underway and to confirm that overheating is no longer an issue.

Many, many, many thanks to all those who have assisted me by answering questions and such. Special thanks to El Pescador who seems to always be online offering sound advice to anyone who asks.

Gute Nacht,

Chris"
 
"You are welcome, Chris. Pleas

"You are welcome, Chris. Please keep us posted of the sea trials results.

Buenas noches, I'm also off to bed."
 
"Hello again,

Well the sea

"Hello again,

Well the sea trials didn't go so well. The engine ran great I'm glad to say, but something weird occurred. It seems that when I went to give it some throttle it wouldn't go past 2500-3000 RPMs and it never exceeded 10 miles per hour. Also, the throttle lever seems to go farther forward than it used to (again without the increase in RPMs.) Additionally, on a few occasions, when throttling up, I would hear/feel a slight shudder as if it were trying "to change gears".

The timing is dead on at 6 degrees before and the engine runs smooth as silk from idle through 4500 RPMs except for a little hesitation if you try to open the throttle too fast. However, it is when it's under a load that the problem occurs. If there was a transmission, I would know what the problem is, but...

If anyone has any suggestions, I'd be grateful.

Thanks, Chris"
 
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