Buick 350

Discussion in 'Small Block Tech' started by Blurredman, Dec 21, 2017.

  1. Blurredman

    Blurredman Well-Known Member

    Hi Guys,

    I know it's been a while but after fixing the majority of what I needed to fix or replace on my '80 LeSabre, all is going well.

    However there is one thing which I have tried to address but never really completed is that the engine somewhat lopes on idle. It is not smooth at all when idling, the engine rocks side to side but with no particular pattern.

    All 8 sparkies look good and have good spark. The timing is on point. Despite the vaccum hoses all over this engine, I can't find any hoses which have perished to the point of splitting or allowing secondary air through the system and i'm a little bit stumped for if it was a vaccum leak i'm not sure it would give that effect on the engine?


    Any pointers/ideas. Much appreciated in advance..!
     
  2. Mark Demko

    Mark Demko Well-Known Member

    What year Buick 350?
    If it has EGR, (diaphragm round thing at back center of intake) it could be leaking exhaust gas into the intake at idle causing it to idle with a lope, like it has a cam.
    EGR is only applied at cruise, its off/closed at idle and WOT.
    Does the engine smooth out off idle?
     
  3. Blurredman

    Blurredman Well-Known Member

    Thanks for the response.

    I noticed the car was a 1980 in the post. :p I have the EGR disconnected and the the hoses that lead to and from it joining to eachother directly. Equally, the small vaccum bottle attached is blanked off.
    The EGR is disconnected mainly because it clicks quite loudly, which I need to look into.

    I do notice that applying the throttle in a smooth action doesn't necessarily apply to the engine. It more sort of lightly 'kicks' the engine and the car moves off. It's not specifically overly noticable really, but it's not smooth.

    I will be doing more investigations specifically into this issue soon (after christmas- with a video), but wanted some pointers first. It's definately not the happiest engine at idle, and although it does rock a little with throttle applied, it sounds even and the rock is neglegible. The idle rock is however considerable.

    I have been driving the car 7,000 miles with this issue.
     
  4. ceas350

    ceas350 "THE BURNER"

    Id start by using a vacuum gauge to set the idle a/f mix screws on the carb.
     
    MrSony likes this.
  5. alec296

    alec296 i need another buick

    Crossed spark plug wire or valve train issue.
    But do a compression test and leak down to confirm the internals.
     
    MrSony likes this.
  6. gstewart

    gstewart Well-Known Member

    If a piece of carbon gets under the valve in the EGR, this cause similar symptoms. Had same in my 1981 Cutlass back in the day.
     
  7. Fox's Den

    Fox's Den 355Xrs

    Get the vacuum gauge to see what is happening. Then reset the carb to get the highest idle and vacuum off the gauge then you will have the carb set correctly.

    Start by closing in the screws and when the gauge drops open each one 1/8- 1/4 at a time and wait 15 seconds for the engine to settle down.

    Then start the process over again un till you reach you highest vac reading, at this point close the screw 1/8 or less then you are done. This does work real good with the car in drive so block the wheels and put on the parking brake before you begin.

    You should hook up the EGR since it is part of the system to keep the engine running smoothly at part throttle. You can get cleaners for this and just make sure that it works when vacuum is applied.

    You could have a lot of carbon built up on the valves and this could be what the problem is. Put some additive in the tank to help clean this up.

    You can always try the old trick of slowly squirting water down the carb while you are pushing on the gas, just don't squirt so much water down to stall the engine, little at a time and keep the rpm up.
     
    Harlockssx and alec296 like this.
  8. MrSony

    MrSony Well-Known Member

    Can he even adjust the mixture screws? Didn't GM block em off in the late 70s/80s? I've seen a 79 buick 350 qjet with them blocked off from factory.
     
    Mark Demko likes this.
  9. Mark Demko

    Mark Demko Well-Known Member

    The early (I think 1975 they started) tamper proof carbs had plastic limiters on the adjustment screws, you could adjust from 10 to 2 o'clock position, these you could pry off.
    Later ones had miniscule cup plugs pressed in, IIRC, you could remove these also, but the carb had to come off to do it.
     
  10. MrSony

    MrSony Well-Known Member

    Would he also need the proper idle screws as well? The normal ones stick out quite far, and if they were plugged they might not have the slot in them. I found a video on youtube about it. It's a Dualjet, but the process should be quite similar. That is of course, if the OP actually has to do this.
     
  11. Blurredman

    Blurredman Well-Known Member

    Okay.

    Sorry for the late reply guys.. Life and all that..

    Had time to look at the car yesterday. Annual inspection is coming and there are things that needed to be sorted.



    The carb mixture adjustment is non-adjustable and blanked off!! Grr

    So, at some point i'll take the carb off the car completely and see if these blanks can be removed or not. I've never cleaned the carb in any way, anyway.
     
    Last edited: Feb 23, 2018
  12. No Lift

    No Lift Platinum Level Contributor

    The EGR problem should have been explained more. If a piece of carbon is wedged under the seat of the EGR valve it will cause a leak from the exhaust into the intake manifold AND it doesn't matter if the vacuum hoses are hooked up or not. This would greatly affect idle quality. It doesn't take much of a leak to affect it. The EGR has to come off to check it, replace it, or replace it with a block off plate.

    After you check the EGR, check the vacuum and do a compression check. A burned valve in these engines wouldn't be unusual.
     
    Harlockssx likes this.
  13. Blurredman

    Blurredman Well-Known Member

    Thanks for the reply.

    Sunday last I eventually looked for the knocking that had got progressively worse over my ownership of the vehicle. At first I thought it was the exhaust knocking, as it only took place when in reverse gear. But, like I said, it got worse, and started occuring in Neutral/Drive too.

    Traced it to the toque converter. Tightened up the three bolts. Of which one was loose and the other two not tight enough IMO. Will keep an eye on that problem, as research has told me it can lead to loosening up again, even with loc-tite and possible flex plate issues when they come loose the first time.

    Engine has a much better idle. A little rocky, but a lot smoother to pull away (and in general) - and the whole car doesn't shake any more. I think it's possible the clutch lockup might kick in again like it used to (all the uneveness of the engine might have prevented it?).


    Anyway, when car has completed it's inspection, will remove the EGR pump, as well as the power steering (it is leaking) and over-haul them, if I can.
     
    MrSony likes this.
  14. MrSony

    MrSony Well-Known Member

    There is an EGR valve, the thing behind the carburetor, but no EGR pump. If you mean the AIR Injection pump or "Smog" pump, you can remove it entirely, or just cut the belt to it. However, since you speak of inspections, that may not be the best idea. I don't think they are rebuildable, here are two on RockAuto. I forget which VIN# the 350 was in 1980, but there are two options. It's expensive, but it may be your only option.
    https://www.rockauto.com/en/catalog/buick,1980,lesabre,5.7l+350cid+v8,1018673,exhaust+&+emission,air+/+smog+pump,4920

    Edit: I just noticed one is out of stock, well, at least they list the part numbers so if the out of stock one is the one you need, you have the #s.
     
  15. Blurredman

    Blurredman Well-Known Member


    Interesting. I was unsure of the difference. My daily driver is a 1 litre carbureated Peugeot, and I predominantly repair two stroke bikes, so a lot of the things on the Buick are quite fascinating to me. I never realised US tech was so layered. Heck, we didn't get rid of leaded fuel in petrol stations until 2000.

    Inspections for emissions are fairly non-existent in the UK for older vehicles. I am obviously getting confused over the EGR and SMOG. So, unlike the EGR Valve, which is indeed connected and presumably working. The SMOG just burns fuel already in the exhaust?- At which point it will do nothing for economy?
     
  16. MrSony

    MrSony Well-Known Member

    It essentially "injects" fresh, outside air into the exhaust manifolds to fully burn the spent exhaust gases. Carbed cars tend to have minor amounts of raw fuel and unburned hydrocarbons in the exhaust, so this aims to cure it. It kind of worked. Wikipedia sums it up nicely: https://en.wikipedia.org/wiki/Secondary_air_injection
    Since you have no inspections, just yank all that crap off. It does little to nothing to hamper performance (as much performance as a 150hp 5.7 liter has), it;s just less stuff in the way. For simplicity's sake, I'd keep the stuff on there. It doesn't hurt anything.
     
  17. Blurredman

    Blurredman Well-Known Member

    Thanks Mr Sony! I will block up pipes and take off belt to the SMOG pump then!
     
  18. Blurredman

    Blurredman Well-Known Member

    Sorry guys, I know this is an old reply to this post, but I am the creator- and it is still relevant :p:p


    Taken off the SMOG pump, blocked the vacuum lines including installing a blanking plate for the entrance pipe. I can actually see the engine now.. I know there's hardly any paint on it left- but it is nice.

    Anyway. The EGR Valve is definitely not working. I got one bolt off fairly easily, but the other is unfortunately being a complete pain and I have given up for now before the stages of rounding start to develop. I can only think that I have to physically destroy the valve unit itself to get anywhere.

    What a bugger!

    Anyway, as above carburettor is non-adjustable - when the EGR is removed and blanked/or replaced (funds for importing of new valve pending), I will likely have the unstable idle issue solved.
     
  19. Blurredman

    Blurredman Well-Known Member

    Okay.

    Got the EGR Valve off, fabricated and affixed my blanking plate. I can't see any difference in the engine- It still rocks somewhat. I suppose next option is to take the carburettor off and thoroughly clean it for crap, as well as possibly discover broken diaphragmes etc? :)
     
  20. alec296

    alec296 i need another buick

    Check spark plug wire order. And condition. Compression test might be needed . Change Gas filter. Run engine in dark / night and check spark ark over from wires
     

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