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sbc running rough
I have a 68 350 i'm running in my truck.I had tbi on it and run little rough becuz of the aftermarket cam i had in it.So i put a carb on it and now it runs rough all the time.
it has a 600 cfm 4bbl carb. hei dis. It idle ok little rough but as soon as i open it up it starts to fall on its face.it sounds likes it only running on 7 cly when i give it gas.Put it in gear and die's.It has spark knock if i give it gas whlie it is in gear.
I adjust all the lifters when i put the new intake on with the carb.
I try a diff dis and run the same.When i check the timing with the light the pointer is off by about 15* it is not were itshould be and i think it is from the blanace being newer. My vac is about 15 low but needle is satying still.
I hope some one can help.I have never had so much trouble before:confused:
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you say your "pointer is off by about 15" degrees.....are you saying that the timing tab is not positioned properly or that your timing is out of whack?
In my unqualified opinion, it sounds like your timing is way out of whack in conjunction with other problems. Whatever existed before was exacerbated by the installation of the carb. Not necessarily by the carb itself, but through the installation process.
You'll need to get some firm baselines and provide more info. What are the specs on your aftermarket cam?
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btw: welcome to CHR....there are a lot of really smart people here (I am not included) and in my opinion, the better you are at defining your problem and clearly stating relevant details in anticipation of their questions, the more likely you are to get the help you need.
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There are a few things I would question..
1) Is the distributor in the right place ( not 1 or more teeth off)?
2) What are the chaces you have a vacume leak in the intake or under the
carb?
3) All of the above?
4) How many miles on engine may be timing chain??
OH I didn't notice till I posted Welcome to CHR If it can be fixed there are people here that can tell you how.
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Re
What i mean about the pointer is.
it should be at the 1:30 almost 2 o'clock spot with the timing mark and what it is when the timming light is on it is at the 10:30-11 o'clock
But when i turn the engine over tdc is right with the mark.
I did check for leaks.did not find any.I cover up the carb with my hands and check it with brake clean nothing.
Being off a tooth i do not think. cuz it runs pretty good.at idle.
I put a new chain on the enigne before i put it in this truck and maybe 30-40 miles tops.Miles on the engine is unkown maybe 50000 tops
The truck had some power just not what it should of have when the TBI was on it.
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I did check the compression in the front four 1,2,3,4 cly i get about 135psi
i can not check the back four becuz of the header are in my way
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Welcome aboard....
Sounds mostly like too much timing advance (spark knock under load, etc). Although, things can get more complicated with EFI computers and what-not that I can't really speak to. (computer controlling timing?)
Assuming good ol' carb'd motor you should have about 8-12* (BTDC)timing at idle without vac. advance and somewhere in the ballpark 32-38* (BTDC) advance at 2500-3000rpm. If you're shooting "11 o'clock" against a "2 o'clock" timing mark at idle that's close to 45* and way too much. Disconnect and plug any vacuum advance lines and shoot it again... you'll want to loosen the dist hold down and rotate the body clockwise to reduce your advance....
If there are computers involved, I can't help but I'm sure there are others around that will chime in....
Good luck,
Chris
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No computer.And the timming mark is there without the vacuum hooked up.
If i turn the dis either way it will not run good.if at all.
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Hmmmmm... how'd you set your idle mixture? Maybe air/fuel off enough that it needs more advance at idle (too rich??). I'm grasping here.... hopefully others can pop in with a suggestion or two. Have you checked your plugs/wires? Still sounds like too much time....
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I have adjust the idle mix a few times no change.The wires are new the plugs were new and i just clean them.the gap is .40...It does seem rich and i change the jets down to .60 the smallest ones i have in my set.
I just had a buddy down off a diff carb to test with just for the heck of it.But it is a 390cfm 4bbl.
I will try anything before i start pulling valve covers and intakes and timming covers to check everything else.
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I know you said it is in right butif it were me I'd remove the dr side valve cover get # one TDC and see where you are with your timing mark. You have to start some where. Thats where I'd start
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yeah that was the next step i will do tonite.
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"But when i turn the engine over tdc is right with the mark."
How did you determine this? What method did you use?
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Well thats what I'm trying to find out. You have to start somplace and this is as good or better than anyother.
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i pulled the #1 plug and stuck a Screwdriver in the hole while i turn it over
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and the damper mark is at "0"?????
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will it looks to be + - 2* cuz the timming marker is bent a little.The marker was for a smaller blancer then the 8" i'm useing
Will in about 3 hours from now i will pull the vavle covers and check and see how the valves are open and closeing then i will go and pull the timing cover.I will let everyone know what i come up with tonite.I was just hoping for some thing else
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This may sound dumb but do you have the fireing order right on the cap/plugs??
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thats not dumb at all.I check it 4 times today every after i drop a diff dis in and had it runing......
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and the rotors pointing to # 1 plug wire.
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If all this is right it should run the only other thing would be vacume leak. Maybe someone else has a idea or 2
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Yeah it does point to #1 ...I think i'm over looking some thing.Maybe the cam is worn a lob or some thing or i miss adjust a lifter...I will find out tonite.I hope
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when you find it post us I'm courious and sorry I couldn't help
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i will do.. Thanks every one for trying to help.Its not easy when your not there..
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mikey, read this please.....
http://www.streetmachinesoftablerock...opic.php?t=350
1. dies when you put it in gear....indicative of a lean condition
2. falls on its face when punched.....indicative of a lean condition
3. spark knock.....indicative of a lean condition
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ok i have check the lifter adjustment and is good.
last night i have some trouble with getting running after that but i cleaned the plugs and now its running again but still the same thing.
What is a real puzzle to me right now is why the damper mark is so far off when it is running???And when i was turning the motor over going to #1 for the valve adjustment the intake is not all the way closed at that point and i know when i had the tbi on it the mark was not that far over and running this bad.
And the pulgs were foul from being to rich.I'm not the best at tuning carbs but i get by.I don't know how to lean it out any more then it is.I have the samllest jets in it..This carb worked great on the last motor i had it on two years ago.It just been sitting on the shelf the whole time.
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ok i think i not told you what i have all the way
68-74 sbc 350 stock
accel dis with vac
600cfm holley 4bbl vac sec
short accel spark plug-becuz of the header room i have
the damper is off a 94 sbc 350
the timing chain is for a 86 sbc
edelbrock intake
edelbrock cam match set for the intake and carb set up
stock rockers
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now the engine use to run good with the stock tbi off a 94 sbc.just not enough power becuz of the cam not working with the computer very good.
all i changed was the intake dis and put a carb on it.
hopefully this will help
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I don't know if we covered this?? If your valves on #1 cyl. are not closed and the timing tab is on "0" compresion stroke. then your timing gears are not allingned right. Chain has sliped or was not on right to begin with. This will cause the problems you are having.
tobad your on the other side of the state
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right...Both valves are closed when its on 0* that is the thing.
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when i was turning the motor over going to #1 for the valve adjustment the intake is not all the way closed at that point :eek:
I think I'd check the timing gears ALSO check if someone put in an off set key.
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what i mean was they are closed when it is on the 0* mark..sorry..but were the mark is when it is running the valve would be open some.
I know there is no offset key in there..
Do you think it is cuz its too rich??
Maybe need some hotter plugs.
I just don't want to pull the front cover off.I don't feel like pulling apart the whole front of the motor apart..Its not easy being in a s-10 blazer you kow..
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When you cleaned the plugs what did they look like black white gray???
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That sounds rich OR sucking oil from somewhere. maybe PCV stuck?? Did you use a sealer when you set the intake??
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i used sealer on the ends of the intake.and i have no pcv.
i know it burn a little bit of oil but not that mush in all the cly's
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ok i figrure out the timming mark thing.me being dumb on that part.the idle was way up.but it did not same like it was.but still runing bad rough idle and fall's on its face when open the thottle quick..I had to stop for the night do to the noise and being smoked out of the garage..I did change the plugs to a stock range and size.not easy.
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Just a thought... maybe idle circuit too rich (fouled plugs lots of advance at idle) but main circuit/transfer slot too lean (knock and bog)? You mentioned you're running the smallest jets you could find. I'm not an expert but maybe an approach like:
1) set timing to ~8-10* at idle (should be ~35* all in ~2500 rpm)
2) adjust idle mix and idle speed for max vacuum at xxx rpm (800?)
3) start increasing main/secondary jet size until it runs right
maybe have a stuck power valve?
As I said, I'm not an expert so take this with a grain of salt and maybe better suggestions....
Good luck,
Chris
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If the carb set on the shelf for two years with any amount of gas in it, I'd say you need to rebuild it. The metering block is probably full of varnish.
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well i did clean the carb when i put it on the truck.
i got it running the best sofar today but still no powerwill taking off from the stop sign...The timimng mark on the blance must be off becuz the it is still at like 30-60 deg...i get it any were close to were it should be it will not run.
i just change the carb to a 390 cfm 4bbl and still to rich..Maybe i have a bad cly..I not able to check the compresson in the back 4 cly becuz of the headers being in the way.i think i need to find a way check them..pull the header or some thing...
Well i think i will start the tear down tonite.Pull the whole front so i can see the chain and pull the headers to check the cly's..and i will try to find a way to check the blancer and go from there
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Hope your inside its going to get WINTER out