Volvo RWD 120-130 Forum

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Performance enhancements follow-up question 120-130

posted by  Aidan on  Thu Jan 22 08:48 CST 2004
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last visit: Wed Oct 22 03:47 CST 2014
[RELATED]

Hi,

Thought I'd start a new thread in case this post wasn't noticed further down. The advice that I received (and that I'm acting on) is that I'd be much better off with twin SUs, a C or D cam and a head change (my wife agrees that a head change would do me no harm at all...)

I was able to source the SUs, a suitable manifold and the cam and followers. The seller also has a B20 head but he's not sure what kind of B20 its from... He reckons that the larger valves will improve breathing but I'm not sure if a B20 head will work properly on a B18 block. Will it work (say with a B20 head gasket)?

I had a quick look at the current B18 head - its marked B18 and has some other numbers but doesn't seem to indicate anywhere that its a B18A head - is there any way of telling a B18A from a B18B etc?

Thanks for all the advice - I learned a lot from yesterdays posts (and saved myself a lot of frustration by the look of it)

Aidan
--
1967 131, 1969 131








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    Performance enhancements follow-up question 120-130

    posted by  walrus3 on  Thu Jan 22 09:10 CST 2004
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    last visit: Mon Dec 2 14:20 CST 2013
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    I haven't studied the B18 heads like I have the B20s but if you are fairly sure
    your head is not from a marine engine, the E and F B20 heads have ports for
    fuel injectors, the others (with smaller valves) don't.
    If it is LESS than 3 3/8" thick it is a high comp head (B20E, etc) but if it
    is more than that it is low comp (B20F).
    In either case if you are going to use a B20 head on a B18, your comp ratio
    may be low at standard bore but if you bore it to 3.5" it will be fine.
    (That is the main reason not to use a B20 head on a B18 engine.)
    You'll need to be sure the gasket is for a B20 and preferably the thin
    head gasket (B20E, etc).
    --
    George Downs, Bartlesville, Oklahoma, Central US








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      Performance enhancements follow-up question 120-130

      posted by  Aidan on  Thu Jan 22 09:25 CST 2004
      Author: [PROFILE] [EVERY POST] [THREADS] [BEST POSTS] RSS Feed     [IGNORE ALL POSTS]
      last visit: Wed Oct 22 03:47 CST 2014
      [RELATED]

      Thanks George,

      I was hoping to avoid a rebore so I'll hold out for a high conpression B18 head. I knew someone once who used to replace the piston rings as a matter of course while the heads were off (they were VW air cooled engines) and it seemed to help the compression - is there any benefit from doing this in my case?

      Aidan
      --
      1967 131, 1969 131








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        Performance enhancements follow-up question 120-130

        posted by  walrus3 on  Thu Jan 22 10:03 CST 2004
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        last visit: Mon Dec 2 14:20 CST 2013
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        If your rings are bad (and they might well be - difference between wet and dry
        compression check will tell this) they should be replaced. It is a LOT more
        work though - you just about have to pull the engine or drop the front
        crossmember to get to the bottom. On the VW you pull the cylinders anyway
        but not on the Volvo.

        You can run a long time on bad rings and not suffer too much in performance
        but you will use a lot of oil if they are really bad and blow a lot of blue
        smoke. Once you get the pistons out it isn't much further to go ahead and
        bore it.
        --
        George Downs, Bartlesville, Oklahoma, Central US








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          Performance enhancements follow-up question 120-130

          posted by  someone claiming to be Joe in St Louis on  Mon Jan 26 03:57 CST 2004 [RELATED]

          Old Timer Mechanic's Way of telling if oil is getting past the rings - Look at the carbon on top of the piston. If the carbon covers the whole top of the piston, you're ok. If the carbon is not deposited around the outside edge of the piston crown, oil is getting past the rings into the combustion chamber.

          Hope this helps!

          Joe in St Louis








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            Performance enhancements follow-up question 120-130

            posted by  walrus3 on  Mon Jan 26 04:25 CST 2004
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            last visit: Mon Dec 2 14:20 CST 2013
            [RELATED]

            Hey Joe!
            That's interesting! I guess the oil sort of "keeps the skillet good and greasy"
            so the carbon doesn't stick.

            If carbon does stick to the piston it means that the piston's surface temp
            is less than 700°F. Any hotter than that and carbon doesn't stick.
            (much hotter than that and they get hot enough to bulge, burn or crack.)
            --
            George Downs, Bartlesville, Oklahoma, Central US







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