454" Engine Moving Foreword ???

[toobroketoretire]

About 6 months ago I pulled my TH700R4 out to repair it and when I put it back in I noticed the transmission mount bolts weren't contacting the slotted cross member in the same place; about 1/4" foreword of where that had been. And I also noticed my fan blades were about 1/4" closer to the top of the radiator. It seemed as though my 454" engine was somehow moving foreword but I can't imagine HOW it could move. Yesterday afternoon I heard a little ding ding ding ding ding noise under my hood and when I opened it I found my fan blades were hitting the top of my radiator when it used to have about 1/4" clearance. Naturally I am very perplexed over this seemingly impossible situation.

To give my 7-blade clutch fan more clearance I put 4 grade 8 studs into the clutch then added two 5/16" nuts on each stud for spacers which will position my fan about 9/16" further back. Moving the fan back won't solve the problem of my moving engine but it'll buy me time while I try to find the cause.

 

[SVO]

Broke Motor Mounts?

Strange problem. Is this a 454 swap into a '81 body? The motor mounts and the transmission mount locates and anchor the motor & transmission into the body. For the motor to move forward would indicate that the engine mounts have either broke or the mount bolts have loosen & fell out. But I would expect the transmission mount to still keep the engine from moving forward. It would be strange for both motor mounts to fail, because typically under aceleration, the driver side is under tension and the passenger side is under compression. Usually, it is the driver side mount that typically fails. In the late 60's- early '70's, GM redesigned their engine mounts to incorporate a limiter to hold the mount together and limit the motor from torquing over. Could a early style mount be used in the swap? Anyway, the place to start would be the two motor mounts and the transmission mount.

 

[toobroketoretire]

Engine Has Moved Foreword 1/4"

Knowing how old motor mounts can pull apart under torque I installed 2 new mounts and then drilled a 3/8" hole thru the middle to put a bolt and self locking nut. With the 3/8" bolt thru the center it's impossible for them to pull apart. This is a 454" engine in a 1971 chassis but it isn't the original 454" engine. After I bought it I installed 10 to 1 pistons, a magnum camshaft, Air Gap intake, and a #3310 Holley. Then I installed a beefed TH700R4 and a set of 3.70's to give me terrific acceleration and still retain good fuel mileage. This last summer I converted the L-88 style hood to ram air so it's a real nice running engine and with it's factory A/C it's a great C3 to drive on long trips.