360 magnum troubles
I rebuilt a 360 magnum and threw it in my Dart, but I can't get the damn thing running right. This is my first engine build and after a ton of problems, I finally got it to idle. The new problem arises when I apply any throttle. I can get it to start up and idle; but when i give it any throttle, it sputters, dies, and coughs out of the carb. Anybody had similar issues and have some sage like wisdom to share?
here are my specs:
Junkyard 360m bored .030 with stock bottom end
Keith black pistons
Custom ground cam on old core
Engine quest heads
Edelbrock RPM air gap
Holley 750 double pumper (recently gone through, maybe i'll do it again just to be sure)
Doug thorley headers
I had an engine like this with a 292/292/108/.508 cam and it liked a lot of idle bypass air, so the PCV worked well. It also wanted some thru-holes in the throttles valves. I moved that cam around from 100* to 112* installed and it didn't change the idle tune much at all. It was ok with 12 to 16 degrees of idle timing.My plug gaps have always been .045 to .055, and I use the sq-top Accell SuperCoil electronically triggered.
I think your T-port sync is just too far off,
and the pump-shot(as mentioned) may be; late,lazy, or insufficient.
and possibly the PV is late to the party
Or you have a massive vacuum leak,
Or some combination, of the above.
As mentioned, your T-port exposure under the plates should be a little taller than wide.And the mixture screws should be in the middle of their travel. On Holley types this will be about 1 turn out, while most others will be about 1.5 to 2 turns out. Then you leave those alone for a long while. To set the idle speed you will use idle-timing and idle-air bypass. To speed it up you add timing,and to slow it down, you subtract timing. When the speed is in the ballpark, you adjust the idle quality with the bypass, that you will have to engineer.
This is a recap of all that has been mentioned.
BTW, at this point I don't even use a timing lite. The T-port sync will command a timing that you just push or pull the dizzy around to get the right idle speed.
After you get this far,, and the engine is responding,then we can revisit the T-port sync,as may be necessary.
Don't be discouraged, this is an easy to-tune-combo, it just might take time.
The biggest monkey wrench is when the intake sucks air from the valley side, but this too is an easy find.
And as mentioned, if you have a flat tappet cam, you need to break that beast in before any of this gets done. I assume that since you are at this point, that, the cam has been broken in. If not, then the cam may already be junk.
