73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: greenmonster on January 11, 2008, 10:00:26 pm
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My truck runs fine but one day I put a timing light on it and noticed it had alot of advance.I turned the distributer and it started to back firer though the carb before I could even get it on the timing marks.I thought the timing marks were off but I checked and TDC is right on zero.It has a rv cam in it do you think the cam is off.If so should I fix it.
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are you positive you aren't one tooth off? yea, your TDC might be "on", but it doesn't mean you have the distributor lined up just right. one tooth can happen to the best of us. and yea, if your cam is off...i'd say you'd need to fix it.
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How do I check the distributor.
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You can put the distributor in anyway you want provided you have enough room to rotate it to acheive your proper timing. What you should do is (assuming you have an HEI w/ vac advance) check your timing with everything hooked up at 2500 RPM and see what it is.
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I don't have a light with advance to do that.But like I said it run fine.I am confused on why the timing marks are off but TDC is right on.
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??? If when you are at TDC the timing pointer zero mark lines up with the balancer mark then your marks are fine. Not realy sure what the problem is here
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Yes the marks are right on.I was thinking the cam was off a tooth.Is it possible for it to run fine if the cam is off.If i bring the timming to 12 degrees it idles but if I give it a little gas it back fires though the carb.
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I doubt you jumped timing on your chain. It'd have to be REALLY sloppy and would be making a lot of noise. Which way are you turning the distributor to make it pop? Counter clockwise or clockwise? Do you have an HEI with vacuum advance?
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It is HEI with vac.I dont think it jumped time I was thinking the guy I bought the truck from put the cam in wrong.I think I was turning it counter clockwise.
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Counter clockwise is advancing it. If you are advancing it and only getting 12° advance with it popping I'm gonna suggest you don't have the inductive clamp around the #1 spark plug wire or you have more issues.
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I dont remeber witch way I turned it but I do know when I look down at the timing marks the one on the balancer is to the left of the marks about two inches.If I turn it to get the mark on time it will back firerwhen I give it throttle.
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Well we really need to know if you are advancing it or retarding it. Counter clockwise would be advancing it. Clockwise would be retarding it. You should invest in a decent timing light. Most now have advance, RPM and a metal inductive clamp that won't melt for under a hundred bucks.
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I am retarding it to get it on time it is showing that it is way advanced.
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What RPM are checking your base timing at? Are you disconnecting the vacuum advance and plugging it when you check it?
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At idle around 800 rpm and with vac disconected.If I plug it in to full vac the mark gets farther away.
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What is it at when you check it? You need to check your advance at like 2500 rpm. Don't worry about base timing right now. total timing then compare it to base. If you have correct total timing your advance is sticking.
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I don't know. The mark on the crank is to far away from the timing marks.If I had to guess judging by distance I would say about 50 degrees advanced at idle.The advance in the dist. moves freely.
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If you don't want to buy an advance timing light your other alternative is timing tape. http://store.summitracing.com/partdetail.asp?part=SUM%2D162591&autoview=sku
Without accurate numbers we really can't help you determine if in fact there is a problem. If it runs good where it's at do the old street tune and advance it til it pings when you womp on it and retard it til it doesn't ping. lock it down there as a baseline and see if it restarts hot ok. If it hard starts retard it til it starts easy and leave it there.
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I would like to buy a timing light but I don't have the money right now.It runs fine now so I won't fool with it until I get the light. Thanks for your time.