If I put more than 32 degrees total timing into the motor, it starts fluttering and missing out. Runs OK at 30 degrees total timing, but you can still hear it fluttering at cruise speeds. There is no vacuum advance hooked up, this just makes it real bad. Initial timing is at 8 degrees. I once read that I should have closer to 36 degrees total timing, though I know this doesn't always hold true. I would like for initial to be more around the 10-12 degree mark, and the total will have to stay at 30 because that's where it runs at. I guess I should modify the slots on the mechanical advance to allow only 20-22 degrees of movement. I am just asking if there's something I am missing here? The plugs are a nice golden brown, so it's not lean.
440 total timing
- Thread starter GUP
- Start date
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abodyjoe
Well-Known Member
in big blocks i usually try to run a total of 38* +/- and somewhere near 17* inital.. sure you don't have a vaccuum leak or something?? what kinda of combo are you running... something has to be being overlooked here..
Keith Mopar
Mopar Nut
Are you sure the timing mark hasn't moved on you. Is your damper the stock one? After 20 years they have the tendency to move a few degrees on the rubber ring.
In my big block I run 36 Total.
In my big block I run 36 Total.
340mopar
Sorgermotorsports
I was thinking the same thing. If it runs better at an indicated 30 degrees then I would suspect that the total is actually a higher number.Keith Mopar said:
I will look into it. I am running 10.5 to 1 comp, fluid damper harmonic balancer, edelbrock alum heads, M1 intake, Holley 750hp carb, Mopar 286 deg cam with 557 lift, comp roller rockers, Mopar electronic distributor. I am using an adjustable timing light, and when I dial the timing into it, it brings it right back to zero on the timing tab. I am overlooking something, because this doesn't make sense. It should be 36-38 degrees total 10-12 initial. I'm gonna go nuts.
i dont know what kind of Tab there is on a bigblock to measure timing to but is it possible that its not in the right posision, or that the timing marks on the balancer is in a diferent posision?
if there is nothing else left i would try unscrewing the #1sparkplug and see if i could check if TDC is realy top dead center, my 318 had an old balancer that was way of and i found out by puting a screawdriver in the #1 sparkplughole and found out that TDC on the balancer was over 10degrees wrong, this may not be the most precise way of checking but i think you should notice if its of by much.. it took some patience and a lot of strenght to turn the engine over by hand but i found out;)
if there is nothing else left i would try unscrewing the #1sparkplug and see if i could check if TDC is realy top dead center, my 318 had an old balancer that was way of and i found out by puting a screawdriver in the #1 sparkplughole and found out that TDC on the balancer was over 10degrees wrong, this may not be the most precise way of checking but i think you should notice if its of by much.. it took some patience and a lot of strenght to turn the engine over by hand but i found out;)
JoeDust451
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GUP said:
Are you sure the timing light is ok, i just use a conventional timing light! those adjustable lights do nothing for me, also, on your dist. does it have a gold plate, on the newer ones they are adjustable, down were the counter weights & springs are, you can set them anywhere you want, or lock it out! i adj. mine too have 20* int. & 35* total.
Could the missing out at cruise speed when timing is at 36 be a result of a lean condition? The plugs are light grey when I pull them out. The motor heats up VERY quickly upon startup after sitting all night. Maybe this is it. I have 80 in front and 82 in back. I will bump them up and see what happens I guess.
moper
Well-Known Member
It definately sounds like there is an issue. The Fluidamper could be slightly off, I've seen the marks on them off 3-4* in one case. Always a good idea to verify and re-mark the TDC when it's being put together, regardless of brand of balancer. Also, what pistons are used for the "10.5:1" you have? A flat top with lose quench will like more timing than a dished piston with tight quench. I generally run (VERY general..each car/setup is diffferent) 38* with iron heads, 32-34 with aluminum modern chamber heads. Especially if they are pump gas engines. The fuel burns much faster, and in a well designed head/chamber/piston top combo, will not require as much timing to run well. Looking quick, I'd say part of the problem is the 750 carb. If it's a typical 4150, it really flows about 690 cfm wet (with fuel). More importantly, the air bleeds are sized for an engine that is smaller. You're able to pull a lot of air with your heads, and I think the carb is just sized too small in it's out-of-the-box form. a smaller carb youcan replace air bleeds on will really help the lean cruise. A larger carb, like a 850DP, or something like a Mighty Demon 825 or 850 will make tuning on the street much easier. Many guys only use CFMs to size a carb, but if you go to the Barry Grant site, you'll notice more than CFM or cubic inch, they use cam size too. For a street and strip engine, it's important to get things sized right, so you dont "give up" anything in any driving situation. Just a thought anyway...
Thanks all. I have sent the dist. to get the curve done. It had 24* of mechanical advance, and it is having it all in by 1600rpm. I am going to set initial at 20* and total will be at 34*. I will have about 4* of adjustability with the screws on the plate. I am sending it to BFO, if any of you have heard of them. "4secondsflat.com" At any rate, I will look into the bigger carb, but for now I will have to make due. I will open the air bleeds up 2 sizes and see what happens. I redid the compression math, it's actually 9.98:1. Thanks Again, I think this will help.
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