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Thread: VS 5 litre low comp...rebuild time?

  1. #1
    Registered User MartyRX2's Avatar
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    VS 5 litre low comp...rebuild time?

    Hi guys, my daily driver Volvo has had a rough idle for a few months. It's always been pretty doughy off the line. Yesterday it dropped a cylinder so this morning I decided to do a compression test for the first time. Results are:
    1- 110psi
    2- 115psi
    3- 115psi
    4- 115psi
    5- 135psi
    6- 120psi
    7- 120psi
    8- 120psi

    This is my first time playing with these things. Google tells me a healthy one should make around 140-150 psi and be within 5 psi on all cylinders. I need this thing running right as it's left me without transport. Are these compression figures low enough to cause the misfire or do I have another problem such as injector not firing? Anyone got a healthy 304 lying about?
    Cheers


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  2. #2
    Registered User MartyRX2's Avatar
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    VS 5 litre low comp...rebuild time?

    Now running on 8. Problem located. Still a low compression nugget though.


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    Last edited by MartyRX2; 26-05-17 at 12:09 PM.

  3. #3
    Registered User mad_cow's Avatar
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    Add boost?

  4. #4
    Goat roper Motherfucker Jones's Avatar
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    Generally if they're pretty even its a good sign it's ok. None are 50psi so it's probably healthy enough to go for awhile longer
    Quote Originally Posted by RVK 355 View Post
    Hold it flat cunt

  5. #5
    Registered User MartyRX2's Avatar
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    Do you reckon comp figures like that could be the cause of my shitty idle?


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  6. #6
    Registered User gtrboyy's Avatar
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    Usually it's ignition or a vacuum leak gives crappy idle.

    Did you give it wet test also to check if it's rings or valves?
    an easy fix is get a mate to drive in front of you at 60 then 80 then 100 and mark in on your speedo with some liquid paper.

  7. #7
    Registered User MartyRX2's Avatar
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    No I didn't. Ignition is pretty good. Plugs, leads, dizzy cap and rotor button not that old. The shitty idle doesn't really worry me, I'm just thinking it might be caused by the wide range of compression values. I'd really like to strip this thing down and give it a good freshen up...especially if it goes a heap better once I'm done.


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    Registered User dnegative's Avatar
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    Bit tired but still good
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  9. #9
    Goat roper Motherfucker Jones's Avatar
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    I don't think it'll go a heap better unless put some flat tops and a stick in it. It might use less oil though!
    Quote Originally Posted by RVK 355 View Post
    Hold it flat cunt

  10. #10
    Registered User 9triton's Avatar
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    did you hold the throttle open when taking the readings ?

    i allways figure 10% is ok between lowest and highest reading - rather than a fixed PSI differnec
    Last edited by 9triton; 26-05-17 at 09:53 PM.

  11. #11
    Registered User dnegative's Avatar
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    Compression tests just cause heartache and pain if its running fine with no issues.
    People read into them too much.
    If its running fine, making good power, not using oil then ignore it.
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    Down with ma homies Greg Rust's Avatar
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    Clean the throttle body whilst you're there.
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    Registered User gtrboyy's Avatar
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    It's probably got few years of life left in it or untill oil leaks get the better of you.

    For it to really jump in power they need flat tops to be worthwhile of any mods...better yet budget stroker kit + small cam.
    an easy fix is get a mate to drive in front of you at 60 then 80 then 100 and mark in on your speedo with some liquid paper.

  14. #14
    Registered User Euronymous's Avatar
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    Does it have much blow by? Shitty idle could be totally unrelated to comp readings.
    Could be dirty or flogged out injectors, dirty iac, vac leak etc etc

  15. #15
    Registered User MartyRX2's Avatar
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    VS 5 litre low comp...rebuild time?

    Quote Originally Posted by Euronymous View Post
    Does it have much blow by? Shitty idle could be totally unrelated to comp readings.
    Could be dirty or flogged out injectors, dirty iac, vac leak etc etc
    No, doesn't seem to. I was going to check out the IAC valve but been lazy. Might give it a go this week. If the thing lasts another couple of years all good. I'll drop an LS in it by then anyway. Been cruising around North Straddie in it all weekend.


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    Last edited by MartyRX2; 28-05-17 at 06:08 PM.

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    See this on the gateway early mornings every now and again. Sounds good if that is of any help


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    Registered User MartyRX2's Avatar
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    Quote Originally Posted by cub35 View Post
    See this on the gateway early mornings every now and again. Sounds good if that is of any help


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    Just a tradie spec 4wd hilux


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    Resident Oaf Jim's Avatar
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    Usual causes of low comp in ford and Holden old school motors is worn cam lobes or worn bores or both. Did you do a wet test? If it comes up a lot then bores and rings are flogged. If not, then it needs a cam and lifters. Alternatively, put a dial indicator on a rocker and measure lift.

    TBH it's usually both tho.
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  20. #20
    Registered User MartyRX2's Avatar
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    Engine got a new cam/lifters by previous owner. Don't know if I'll bother rebuilding this or go the LS route. I should really be focussing on other car projects and rebuilding the 5.0 would be about a quarter the work of an engine swap not to mention cost.


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    Chopped BigMuz's Avatar
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    Quote Originally Posted by Jim View Post
    Usual causes of low comp in ford and Holden old school motors is worn cam lobes or worn bores or both. Did you do a wet test? If it comes up a lot then bores and rings are flogged. If not, then it needs a cam and lifters. Alternatively, put a dial indicator on a rocker and measure lift.

    TBH it's usually both tho.
    Cam is always the first thing to check on the plastic motor, they kill them. Being brand new doesn't mean shit unfortunately.
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    Registered User Euronymous's Avatar
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    Nice 5.0 powered 244 surf wagon!
    If it doesnt have much blow by, then rings are probably ok. ( as suggested good idea to do a wet test)
    Also can just chuck a bottle of top end cleaner through it and see if that helps

  23. #23
    Registered User MartyRX2's Avatar
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    VS 5 litre low comp...rebuild time?

    So Iíve been thinking about this again and had a little brain wave. Considering the previous owners standard of workmanship on the rest of the car thereís a pretty good chance he never dialed in the new cam properly. Iíve never dialed in a cam on one of these before so Iíve been watching a few tutorials. The more I watch the more convinced I am that this engine has a cam timing issue. Thereís every chance thatís what is affecting the compression. The engine itself just runs far too well for something worn out. It uses no oil or coolant and starts easily. It just feels about 40% down on power. Itís a bit embarrassing how slow it is off the lights. Anyway, Iím looking at these Comp Cams degreeing kits. If Iím going to go to the trouble of degreeing the cam I may as well throw a better stick into the thing too. The question now is what stick. Iím not planning on touching anything else so the 8.7:1 comp will have to stay. Iím thinking some way down the track of boosting this thing so a grind that suits turboing will probably be chosen. TK a while back recommended a Camtech CT248 520a which has 224/230 at .050 and 110 lsa. Iím tipping this wouldnít really suit the boosts though.


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    Hyd roller.

  25. #25
    Look behind you... Milkman Don's Avatar
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    While you putting a decent stick in may aswell send the heads off to be cleaned and a light skim to give you a little more comp. Could do a home port match job for the exhaust if you are keen enough.

    What ratio diff is in it? If slow off the lights a smallish converter or diff gears will help you out
    Quote Originally Posted by Faux Forg View Post
    I agree with Rdyno

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    Registered User MartyRX2's Avatar
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    Being Jewish Iíd rather not pull the heads.


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    Flaccid Member bbits_elements's Avatar
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    Thereís no gas in there mate, just a gasket and some cylinders.
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    Ha ha ha ha ^
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  30. #30
    Registered User 9triton's Avatar
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    ^^lol (Edit to BBits post)

    why not check the cam timing before you do anything else .

    then adjust-if necessary . as the cheapest Yiddish first step

    do you know the specs of what cam is there? and a dial guage on the push rod and Top dead centre marked and go from there.

    could check all the lobes that way and see if there is any significantly worn
    Last edited by 9triton; 22-01-18 at 08:28 AM.

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