FAQs about PVR6 engines.

  • Problems that can lead to cam destruction in the 260 engines.
  • DON'T plane 6 cylinder heads.
  • Symptoms of PRV cams starting to go bad.
  • I'm concerned about cam wear.

  • Problems that can lead to cam destruction in the 260 engines.

    To: swedishbricks@me.rochester.edu
    Subject: 264 Cam rehab
    Date: Mon, 27 Jul 92 20:56:47 PDT
    From: Rick Farnbach <fsf@wv.mentorg.com>

    If you are not a 260 owner, thank your lucky stars, take an oath never to buy one of these pigs, and move on to a more important message.

    For those of you still reading, I finally got my 260 engine manual after waiting almost three months. (For those of you who don't go to the trouble of putting car with faces, er, e-mail addresses, I'm the guy who just discovered that his 260 had gone through another set of cams in less than 10000 miles.) Well, I read the manual on how to do it right. Hopefully, I can save some other poor soul out there the expense of doing it wrong.

    First of all, walk away from anybody offering to punch some holes in your firewall and fix your problem without removing the heads. It's not going to work. Yeah, yeah, I'm sure it has worked for somebody, but the probability is decidedly low. If whoever does the job is willing to stand behind his work and redo it 10,000 miles later, then what the hey, give it a shot, otherwise you are likely to waste your money. From what I've read over the weekend, chewed cams are only a symptom. Replacing them may make the symptom go away temporarily, but it will likely return.

    These 260s are like thoroughbred horses. There's about a billion things that can go wrong with them and they all show up in the hooves, or in the car's case, the cams. The following are problems that can lead to cam destruction in the 260 engines. Don't stop looking after you find the first problem, however, since you may have several.

    1) Sludge. If there is any carbon deposits in the valve casing, or any water in the oil, you must thoroughly clean the valve casing, the timing chain casing, and the oil pan. Sometimes sludge may be present without being visible with just the valve covers removed. If you really want this to be the last time you replace your cams, *always* clean these areas. They should look brand new before you seal them up.

    2) Water in the oil. Head gasket, at least. Get ready for some real work. If your problem is a warped head, the Volvo manual claims that you can't machine the heads flat, and have to buy new ones, for which the local dealer wants close to $700, are you ready for this, EACH. Personally, I'd sooner give the car to a scrap yard. Which brings up where I plan to get replacements for my heads. I'm going to grab a straight edge and some feeler gauges and find me a head that is less the .005" warped, since that is what the tolerances are. Then, I'm going to have it machined flat. I just can't stand the idea of putting a warped head onto the car. If the head gasket has .005" of play in it, then machining the heads this much can't have that much of an impact. I might also consider getting off my high horse and buying rebuilt heads for $175, and trusting that they didn't do anything stupid in the machining.

    3) Gas in the oil. Your oil should not smell like kerosene when you change it. I don't know where to tell you to look for this problem. My guess is faulty rings, but I guess a bad head gasket could also be a culprit.

    4) Worn timing chains. If the timing chains are worn, oil will leak past the piston in the tightener and divert too much oil away from the upper end. You can inspect this without removing the timing chain cover.

    5) Low oil pressure. Check this before you ever attempt to repair upper end problems on your car. Low oil pressure can have a number of sources, not the least of which is a defective pump, or a sludge caked pickup screen. To be safe, I'd correct the low pressure problem before undertaking the cam/rocker repairs. If you are sure you know what the problem is, you might be able to save time by fixing it at the same time you fix your upper end, but recheck your oil pressure often during the upcoming month to make sure.

    6) Air in the oil. Some of the early 260's (I can't remember which ones), had a problem with a collar slipping and allowing air into an oil passage. The manual claims you can detect this condition by watching the oil flow from the jets under the rocker arms. I don't know how you could, however, since the jets are tucked away where they are hard to see.

    7) Bad release vent setup in the oil filter area. This was a design deficiency in the earlier Volvos. If you've got a B27F engine, then you need to fix the release vent. To check to see if this has already been done for you, take the oil filter off and look for a vent next to the post on which the oil filter mounts. If you see a screen in the vent, you're probably OK. Otherwise, install the newer configuration. Apparently, this was implicated in the high mortality rate.

    8) Bad oil. Make sure your oil is at least SF grade. I don't know what all those grading letters mean, such as SF/CG or SF/CC, but I do know that pretty much all the oil I've seen is SG, and that's supposed to be better. If you *aren't* going to see temperatures less than 32F, use 20W-50, 10W-40 otherwise. From the chart they give, 15W-50 looks like the stuff to get, but I haven't seen anything like this in the stores. (Actually, I think Mobil-1 has a 15W-50, but that stuff's way to expensive, and a little quirky in my opinion.)

    As for my poor car, I'm going to drive the existing cams into the ground while I look for the cause of the upper end lubrication problems. Then, in a giant fit of industry I'm going to pull the timing chain covers and oil pan and scrub them shiny. I'll either get a couple of heads rebuilt, or just buy them already rebuilt and slap them in place. I'm going to have the jets machined so they expand outward and hence won't trap any happenstance debris they might see. I'm also going to fix that oil filter vent setup. While I've got the timing chain covers off I might even buy a brand spanking new oil pump, but I'll probably check the tolerances before I get this enthusiastic. The timing chains had *better* be OK, since I had them replaced when I had the cams redone. I'm also going to check on those fallen collars while I've got the oil pan off. If they're the type that fall, even if they haven't fallen, I'm going to do what the manual suggests to tack them in place.

    Finally, according to the Volvo factory manual, the cams in these cars are only face hardened. I'll probably go non-factory here and get me some thoroughly hardened cams. This won't really save me any work, though, since I'll still have to go tear the engine apart if the cams show any sign of wear in the future.

    Here's a neat trick I got from the manual on how to test the cams for wear less obvious than the gouges and grooves I'm seeing: Rotate the engine so that the piston you are testing is at top dead center. Then, turn the engine and record the number of degrees you had to turn it before each of the valves just barely starts to open. I don't have the specs in front of me, so I can't tell you what good values are, but at least you know there's a way to test your cams in place.

    Also, removing the oil pan doesn't seem to be too tough a job. I realize this is not he case in the four cylinder Volvos. I think that rather than cleaning the rocker arms periodically, or perhaps in addition to it, I'm going to remove the oil pan regularly and clean it. I think that will have more impact on the lifespan of the cams.


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    DON'T plane 6 cylinder heads.

    To: swedishbricks@me.rochester.edu Subject: DON'T plane 6 cylinder heads Date: Wed, 05 Aug 92 16:11:41 PDT From: Rick Farnbach <fsf@wv.mentorg.com>

    A while back I posted some thoughts on keeping up with the upper end troubles notorious in 6 cylinder engines. In there, I mentioned that Volvo says not to plane the heads of 6 cylinder engines. I said that I'd probably plain 'em a wee bit anyway, just because I couldn't believe you could take a head off a car and put it back on without it leaking.

    Well, I'm still not convinced that the latter is possible, but thanks in part to Tim, I've decided that planing anything at all off these heads is a big mistake. I guess I'll just have to take my chances reinstalling heads that are not completely flat on the bottom. Let me explain this change of heart...

    First of all, the guy who claimed to have fixed my Volvo *did* plane the heads, and now I have to redo everything he did, plus a little. So he definitely did something wrong.

    Second, Tim pointed out that the timing chain covers will no longer fit once you plane the heads. Hmmm. Now I think I know where all that oil is coming from that's been leaking out of my 264 of late: the junction between the timing chain cover, the head, and the valve cover. Andre', the guy who fixed my car, who also appears to live in a completely different state than the Andre' on this net, claimed to have planed the timing chain covers so they would fit, but apparently he didn't do this very well.

    Were oil leaks the only potential problem, I could just try to plane the timing chain cover better this time and consider the problem solved. This morning, however, I realized what the *real* problem is with planing the heads: slack.

    When you plane the heads, you lower the cam shaft pulley, which induces slack into the timing chain. On the 6-cylinder, each chain has a chain tightener which is operated by oil pressure. The tightener is pushed against the chain by oil pressure agains a piston at its base. When the piston reaches the end of its travel, it no longer seats in the cylinder, and oil flows around it into the timing chain casing, which happens to be away from the head, where you needed it.

    Big deal, you say, he surely didn't plane off more than .010", and the piston must have more travel than that. True, true, but he surely didn't plane less than .005", either. Because the piston pushes perpendicular to the chain, it actually must travel much further than just the amount of slack introduced. When you consider the chain tightener is intended to take up slack introduced by wear of the timing chain itself, and the chain probably doesn't wear by .010" between changes, you realize that the piston probably *is* at the end of its travel.


    (Anyone want to make a crack about having to throw away several hundred bucks worth of equipment over a couple of dollars worth of damage? Anyone think this is the sign of quality engineering?)


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    Symptoms of PRV cams starting to go bad.

    To: bchriss@arch3.att.com
    Cc: swedishbricks@me.rochester.edu
    Subject: Re: Are these PRV cams too young to die?
    Date: Tue, 08 Sep 92 09:53:18 PDT
    From: Rick Farnbach <fsf@wv.mentorg.com>

    >>>>> On Sat, 5 Sep 92 12:31 EDT, bchriss@arch3.att.com said:
    Bill> My Volvo dealer told me during the 120Kmile service on mu 85 760GLE that
    Bill> the cams in the engine are wearing and will need replacement. (The mechanic
    Bill> wrote "cams shot" on the shop order.) I remember some discussion in the
    Bill> past about those PRVs (I have the B28F) and thier lousy cams.

    If your cams are really shot you should here a regular, and fairly loud tapping when the car is running. It should sound almost like someone hitting a chunk of metal with a hammer. Another symptom is backfiring through the air intake. (For the technically minded, I don't think it's really a backfire.) If you are mechanically inclined, there are a couple of tests you can do to confirm the condition of the cams before you have the work done. One involves disassembling the rocker arm shaft in place, and the other involves measuring the number of degrees the engine rotates between TDC and valve intake/exhaust valve opening. The latter test is quite precise and may detect cam wear before the point of failure. Of coarse, if the damage is really bad all you'll need to do is pull the rocker covers off and look at the cams.

    There is a long list of reasons why these cams fail. "Normal" wear is not one of them. If all you do is replace the cam, you will likely have to repeat the procedure in a few thousand miles.

    In my experience, Volvo dealers are decidedly ignorant about the six cylinder cars. I've actually given up on letting them do anything to my engine. If I were you, I'd have the audacity to quiz my mechanic on the possible causes of your camshaft wear and make sure he knew what he was talking about. I'd also have him outline in detail what he intended on doing to fix the problem. Don't let him cop out and claim bad or dirty oil as the reason the cams failed unless he can come up with physical evidence to support his claim.

    I have saved a previous message I wrote with a list of the possible causes for the cam failure. If you are interested in this level of detail, email me privately and I'll send you a copy.

    Bill> 1) Do they wear gradually or will their be a sudden change as if a piece of
    Bill> the cam breaks off?

    The cams are "face hardened". Once you've worn through the face of the cam they go pretty quickly. No piece will break off, however. You should consider having the work done fairly soon, as the worn pieces in your oil are extremely abrasive.

    Bill> 2) Is there some kink of a hidden recall on this?

    I only wish. The dual overhead cams are tough to work with and are problem ridden.

    Bill> I really do enjoy this car. I purchased it last September and have
    Bill> travelled 24Kmiles the first year. My goal is to keep it for at least
    Bill> another 3 years and maybe 200Kmiles.

    Best of luck. By the time all is said and done, this cam problem may end up costing you as much as you paid for the car originally.


    I'm concerned about cam wear.

    Date: Tue, 27 Apr 93 22:24:32 EDT
    From: Tim Takahashi <tim@me.rochester.edu>
    To: edward@etch-eshop.berkeley.edu (Jay Edward Sparks), swedishbricks@me.rochester.edu
    Subject: Re: cam wear question

    On Apr 27, 4:56pm, Jay Edward Sparks wrote:

    } I was just informed that cam wear is a concern in some models.
    } My friend claims that the lobes have a hard material on the surface,
    } once that wears through the cams go flat in a hurry.
    } Does anyone know more? like which models and what to do
    } if yours is among those?

    I know of two models with "cam" problems.

    One group of cam problems is associated with B18/B20 family pushrod motors used from 62-75 on a wide variety of problems. The factory suggests that you adjust the valves every 6000 miles, many B18/20's are always noisy up top. There seems to be a serious problem with the iron camshafts sold for high performance use by IPD. I can think of three or four circumstances where well maintained motors ate cam lobes in very short order.

    The second model with famous cam problems is the french B27/28 family motors fitted to 260 and 760 series cars (76-90). In this case, it is really the rockers which wear abnormally quickly in an undermaintained motor. When the rockers have worn substantially, they begin to chew up the cams. This motor is very complex, very few mechanics will rebuild one.

    The cam problem on the B18/20 is a materials problem - inadequately hardened camshafts.

    The cam/rocker problem on a B27/28 is a lubrication problem -the oil passages to the rockers get plugged. The cams and rockers are a very high grade steel, and are induction hardened.


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