As several people have said, idle is too high or the throttle is open too far.
That is why some car companies started to put electrical anti-dieseling throttle stops on the cars.
When ignition was off, the plunger was all the way in and the throttle was totally closed.
When the...
Gross HP and Torque vs Net HP and Torque...
HP
GROSS / NET
275 / 235 @5000rpm
TORQUE
340 / 310 @ 3200rpm
http://www.hamtramck-historical.com/images/dealerships/DealershipDataBook/1971/71_Dart_Demon0011.jpg
Change over to the cast crank was April 11,1972.
Started at Engine # HM340R-3911-8000
http://www.hamtramck-historical.com/images/TSBs/1972/09-07-72D%20p1.jpg
"That hot air in the exhaust port is forced out and with no air left a vaccum is created which rushes ambient air back into the head."
How is hot air forced out and what happens to 'cool air' when it is surrounded by hot metal??
And kids ridding the mini bikes and go karts around with no...
" Part of the valve is in the guide and part of it is exposed to the air."
Yes, but the exposed valve is surrounded by a very hot head and very hot air in the exhaust port.
Let's put it another way.
Bake a cake in the oven at 400 deg for 20 minutes.
Open the oven door and 3 minutes later..grab the cake pan with your hand.
Bet ya the 'cool outside air' hasn't cooled the pan very much at all.
I dare you to run the engine for 5 minutes with no manifolds, shut it off and let it sit for a minute and then stick your finger up in the exhaust port.
Not to butt in.............
For the rear O2 sensor, you can always install a syms box. It always tells the computer that everything is fine.
Used one on my 98 R/T when I sorted melted the converter while towing and most of the guts got filtered thru the exhaust system.
Check to make sure your breather hoses have not gotten soft and collapsed internally.
Also clean or replace your PVC valve and make sure the connections on your valve covers are clear.
As many of you guys know, all the Nascar bodys break their cams and valve trains in on non-running motors with "soft" springs.
Of course, they have a bit bigger budget and run just a bit more cam.
I picked up about 1 mpg on my 5.9 Dakota when I put the Shaker hood on it.
And the fresh air really made a difference while towing...and it sounded better too.
Make sure the piston is about a half inch away from top dead center.
When you are done, crank it up to TDC and stick a shop vac up to the hole.
If you have a small magnet, swipe it around just for grins and giggles.
Install plug and go for a ride.
360 with a Thermoquad is the way to go.
Very small primaries and the bigger displacement means really good torque,throttle response and fuel mixing during normal driving.
Huge secondaries only feed as much air as the engine can take and also gives you that splendid 4 bbl moan.
Your tranny linkage is just a hair out of adjustment.
Get the car up on jack stands and crawl under the driver seat.
Have somebody run the tranny thru the gears and then put it back in park while you watch the linkage move.
The lever and rod attached to the tranny will move to the rear of the...