Fresh 360 breaking up at low RPM'S.

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74RR

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So I dropped in my fresh 360 along with a rebuilt 904 and 8 3/4.
My problem is that in idle or when I have it on jack stands it runs great. I can pull rpms and the throttle response in awesome. Now, when I pull it out onto the street I can't pull anything beyond 2500/3000 because it breaks up so bad. I have to let off the gas it regain and basically idle back to my garage. I did have a friend put a gun on it to time but I'm not sure where he locked it in at. Does this sound like a timing or fuel issue?
360
KB 107'S
Comp 508 cam / ported heads / RPM Gap
recurved dist with stock ignition and Accel coil that gets very hot when running


Thanks.
 
74RR said:
So I dropped in my fresh 360 along with a rebuilt 904 and 8 3/4.
My problem is that in idle or when I have it on jack stands it runs great. I can pull rpms and the throttle response in awesome. Now, when I pull it out onto the street I can't pull anything beyond 2500/3000 because it breaks up so bad. I have to let off the gas it regain and basically idle back to my garage. I did have a friend put a gun on it to time but I'm not sure where he locked it in at. Does this sound like a timing or fuel issue?
360
KB 107'S
Comp 508 cam / ported heads / RPM Gap
recurved dist with stock ignition and Accel coil that gets very hot when running


Thanks.
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Yes I think we'll need to know what the initial and total timing are. Also, what carb? What fuel pump? What size fuel lines? What stall converter? What rear gears? What size rear tires?
 
Check your battery/alternator voltage. Low voltage to the ignition under load will cause that issue. Also make sure that all electrical connections and grounds are tight.
 
Walker434 said:
Yes I think we'll need to know what the initial and total timing are. Also, what carb? What fuel pump? What size fuel lines? What stall converter? What rear gears? What size rear tires?
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I knew I was forgetting info. My mind is still at 4th of July weekend.. 750 DP mech sec / Holley carb not sure what size? 3/8"lines. 9.5" PTC convertor. 430 spooled rear. 255/60/15 tires for now
 
Oldschool said:
Check your battery/alternator voltage. Low voltage to the ignition under load will cause that issue. Also make sure that all electrical connections and grounds are tight.
Click to expand...
Ok thank you. That gives me a few things to also look at.
 
the pickup coil or the reluctor gap . would be my guess since someone was into the distributor . and are you running a resistor ?
 
also check that the coil wires on correctly...plus and minus...
 
Yes I am running a resistor. I will check the + and - at the coil.
 
dot to dot is not the same as degreeing the cam
it presupposed there were no mistakes made in the production process of the cam

and if that is true, your golden, but if the centerline of the cam is not true, your dot to dot timing will be off as well

using a degree wheel would allow you to install the cam regardless of centerline trueness
(but it sounds like your aware of that)
 
318willrun said:
If the cam manufacture messed up so bad that dot to dot made it backfire and break up, then a degreeing wheel isn't going to be a fix for that..... Just say'n
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Probably not, but you are familiar with the term "tolerances stacking up against you" right?

A few degrees off on the cam may not be his issue...but it could be part of it
 
diymirage said:
Probably not, but you are familiar with the term "tolerances stacking up against you" right?

A few degrees off on the cam may not be his issue...but it could be part of it
Click to expand...
Now, a flatten cam lobe or two can cause that....

74RR- is it back firing through the carb? Electrical will be a "SNAP/POP" break up. Timing, either ignition or cam will be a "backfire snap" break up, often through the carb. If it's a fuel break up, it can "snap" due to lean, but will usually show symptoms of "running out of gas".
 
No back firing through carb at all.I should add that I pulled a few plugs and it is running very rich.
 
74RR said:
No back firing through carb at all.I should add that I pulled a few plugs and it is running very rich.
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It may not be running rich at all. It may have a serious spark delivery causing the plugs to turn black along with the back fire. But, it could be massive overloading of the carb causing your problem.
 
You mentioned "Accel coil which gets very hot when running" I think I'd check there first. If your + and - are wired correct it might be time for a new better coil, I have heard bad things about Accel stuff.
 
MOPEkidD-3 said:
You mentioned "Accel coil which gets very hot when running" I think I'd check there first. If your + and - are wired correct it might be time for a new better coil, I have heard bad things about Accel stuff.
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I have heard bad things about this Accel coil too. Would be nice if this was it. Easy enough fix. lol..
 
73AbodEE said:
definitely check and double check the float levels. fuel pressure is a big deal as well.
Click to expand...

And it may very well have a piece of crap stuck in the float needle from messing with all of it.
 
I just doubt it would idle good if something was in the float. It would overload pretty bad.
 
I've had a real nice idle only to have it run like **** down the street and flood out on me because the floats were too high
 
73AbodEE said:
I've had a real nice idle only to have it run like **** down the street and flood out on me because the floats were too high
Click to expand...

but that would be an off idle stall, it sounds like he can pull to 2500-3000 RPM before it dies
 
well y'all can argue with me but I have 35 years of dicking with nothing but Chrysler products and all the aftermarket stuff that goes with it. Ive built and ran probably 300 plus carbs in my day and you would be shocked at all the different problems a poorly tuned or jacked up carb can cause. it takes 1 hour to completely go through a Carter or Holley carb. it doesn't hurt to double check a carburetor and it's fuel supply. without that in working order, nothing else is going to work correctly. none of us are there so we don't know EXACTLY what is happening.
 
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