Hi guys, Its been some weeks that you all helped me with my last posts. Thanks!!!! I followed all the leads posted and everything turned out fine. Engine pulls like a horse, got all the timing right, rebuilt the carb, got all the vaccuum hoses en possible leaks checked. Drove car for about 20 miles and all still good, shifting goes fine, no problem, but just drove it about 40 miles and same problem as in the beginning. Engine runns fine in park but when put in reverse or drive the engine stops. Only thing to get driving is to ref the engine and put it in gear and it'll grab the gear and leave of with tire squirking :3gears: Doing this it gives a real noticable "bang" before leaving off. Same problem occured before I fixed all above, but than it happened when engine was cool and hot. Guys.... this is getting out of my league o No: ... hope you can help me out. Many thanks!!!! Menno
Several possibilities: 1. Incorrect idle speed. Includes missing/defective idle solenoids and/or dashpots 2. Do you have a stock cam/carb? If so, you should have enough torque to run a stock converter at idle. If not, you may need a looser converter to allow normal idle speed.
Thanks! The weird thing is that it only happens when engine has ran for half an hour or so, before that all is fine. I already put the idle speed up a little, around 600 rpm. As far as I know its an all stock 73 455 and a 78 TH400. Thanks again! Menno
One problem here could be if you are by chance running manifold vac to the distributor at idle, this could cause the engine to die when put in gear. What you say? Thank you for asking. Think about it , if you have manifold vac at idle, when you put it in gear, the rpm drops, rpm drops, vac drops, vac drops , timing drops, timing drops, rpm drops, rpm drops vac drops,,,,,,,,, You see what happens here? Ran into this problem back in the mid 70's on my 65 GS with a 401 at the time. :Smarty: Jim Burek
Menno, Would like to help, but your not giving us enough details. You say you straightened out the timing, what is your initial timing at idle speed? Put a vacuum gauge on the engine, what vacuum is it pulling at idle speed? If this is a stock 73 engine, it should pull at least 18" of vacuum at idle, in park, maybe more. If anything you may need more advance at idle. I don't think the vacuum advance is contributing to this at all, especially with a stock engine. The stock vacuum cannister will give 14-18* advance at 16" of vacuum. You engine should pull at least 14" in gear, if in fact it is a stock engine. The 73 engines have EGR. What did you do with that? If the EGR is open at idle, the idle will be very rough, and it will stall. Hope you have a timing light, and vacuum gauge. These are essential tools for working on any engine.
Hi guys, thanks already for all the help. I give some more details. I dont have a vacuum gauge, so that will be something to aquire soon. Distributor has stock springs, I have set timing at about 12-14*, second timing mark will reach about 40* at 2500 at max. Everything on engine is stock. I have connected distributor vaccuum to the carb, as I have with my other 455's (also a 71 #matching GS Stage1, OW trans, built in Freemont, CA :jd: cool huh I have shut EGR vacuum hose. Only vacuum the carb sucks is from distr, pvc-valve and vacuum cannister. The rest is plugged. When engine runs for half an hour the misery begins, before that no problem at all, great pulling and constant idle. I have set idle in neutral at 600, could put it a bit higher maybe. But it runs great when its not been driven for more than half an hour. If someone needs more info just let me know, hope we can solve this problem, never had this before. Many thanks, Menno
Menno, OK, timing of 12-14* should be plenty at idle. Pick up a vacuum gauge, they are cheap. See what the vacuum is at idle. You mentioned that this doesn't happen until the engine gets hot. If this is a Q-jet, some of them had what's called a hot idle compensator valve. It is a passageway controlled by a bi-metallic strip(like a choke thermostatic coil). It is supposed to open up when the engine gets hot, to offset rich mixtures in the intake manifold, which would otherwise cause rough idle and stalling. I read about this in the Doug Roe Book on Q-jets. According to the book, these were used on Q-jets from 1967-the late 70's.
Thanks Larry! I havent seen this bimetal valve during rebuilding the card, its a 73 455 buick carb so it could be there somewhere, I will check another carb with same # to locate the possible position. Really appreciate all the the help from you guys!!! Cheers, Menno
Vac Schematic for 1975 455 Le Sabre? Does any one have a good vac schematic for 1975 455 in a Le Sabre? I need one bad! I have Vac Problems to fix. This problem on the stalling could be vacuum line in wrong spot. ie : ported instead of manifold switch-a-roonie or the lines could be hooked to the wrong spot on a thermal reactor ( temp driven vac switch) that is only coming on when the engine warms up. works as idle and then the game changes when it gets warm. Really need a vac diagram if any one has for 1975 455 - non calif. THx, Doug
Isn't That A Little Low? If the idle is set at 600 RPM in Neutral, won't that drop it to 500 or less in gear? Seems like it's a bit low to me, even with all stock carb, intake, cam, etc. Seem like if anything, that 600 RPM should be set with the engine up to operating temp and in Drive. Shouldn't be a problem with jerking the driveline around when going into gear. Just for giggles, way back when I had my 68 Riv I set the idle as low as I could and keep the engine running when I dropped it in gear. I think I got it down to about 450 or 500 in gear. Seemed like it was barely ticking over at that speed.
Is it possible that you have the wrong carb plate gasket? You said once it warms up it dies when put in gear. I would start by raising the idle just enough to keep it going and then spray just a tad of carb spray down the carb throat and if it smooths out then you have a lean condition. Proceed to spray around the base plate just alittle at a time, making sure you don't over do it and then check all vacuum lines the same way.Also the air fuel mixture screws could be turned in too far . If you turn the mixture screws out and it does'nt smooth out then the leak is too big for the carburetor to compensate. Note : keep you face from over looking the carburetor at all times as a back fire could ruin your day !!! good luck David :Comp:
Hi you all there! I think I'm saved from the stalling. Thursday the engine wouldnt start, so I disconnected the choke... it started immidiately. Dont know why but it worked. After that I set the idling speed in gear to about 510, my 1973 manual tells me to put it at 500. Now it hasnt been stalling anymore, I also removed the complete choke story from the carb and plugged the passageways. Hope it'll stay this way, but still havent figured out why it wouldnt start with the choke assembled. Thanks all you guys who helped me here!!!! Keep those 455's purrrrrrrrrrrrrrrrrrrrr Menno
Hey Erik, How's life, you're right I should have said RRROOOOAAARRRRRRRRRR Maybe see you in Stadskanaal next sunday, maybe if the weather is nice we take the 71 GS stage1 Menno
Too much timing? I had a 75 Chevy pickup that had a curve kit in the dist with the light spring. The timing advanced too quickly for what was basically an RV motor and it stumbled or died frequently until I re-curved it. I wouldn't run that much timing in a street motor. Another crazy thing that happened to me was the stupid vaccuum pot in the exhaust was sticking and causing a huge backfire, along with the typical "broomstick" Chevy lobes from stock motors of the day.
