502 in 71 nova

What is the deal with it being to the left and all that, did Chevrolet not center the big block or what? Yes the motor is indeed shifted to the passenger side because a big block is Big! So big it will not fit on the centered SBC motor mounts. To make it clear the steering box (with cast iron exhaust manifolds not headers) the factory moved and raised the motor to make room. In doing so it shifted the hole in the radiator shroud, ran it into the heater box, and offset the transmission.

What is a flat block six cylinder? The original six displaced 235 cid in it’s final form. It is known as the stove bolt six because it used 1/4-20 fasteners to hold all of the tin on the motor just like an old coal fired cast iron stove. It differs from the newer thin-line sixes which share the bore spacing of the SBC by being chunkier with a thick cast cylinder wall you could bore over about 0.120 of an inch if desired (the new sixes will go 0.030" and have a max overbore of only 0.060").

I still don’t know what I have to with the motor mounts. Do I have to change the frame mounts or just put solid mounts on the motor? This is another historical problem that confounds people but it has nothing to do with the BBC conversion.

In 1968 GM had the first ever federally mandated safety recall of a product ever. The motor mounts were breaking because the cars were getting heavier each passing year and the motors were also getting bigger and more powerful. So in 1969 all motor mounts had a new design. It is taller than the 1967 and 1968 design used on the SBC. It is also narrower to prevent you from installing the 1969 mount on a 1968 car by mistake. Every parts guy back in 1970 knew this and would get you the correct part.

Fast forward forty years and all those parts counter guys have retired. There was another major change in the motor mounting system in 1973 which GM still uses today. There is a lot of confusion as to what is the correct motor mount for a specific car. The article explains that there are in fact four different engine chassis stands and motor vibration isolation mounts. You can install a modern clam shell mount on your Nova if you desire to do so it just requires finding a donor from a Monte Carlo or a Chevelle from the mid seventies to do it.

Big Dave

I won't tell you what I'm wearing right now it is to close to dinner time on the East coast and I do not want to ruin any ones digestion. Suffice to say it is still above 78° an hour after dark and I have not a lot of clothing on as I sit here typing in a puddle of sweat (just hung up my Christmas lights out side, most of them anyway before being driven in by mosquitoes).

In a word do not try it. I had a ZZ502 four, five years ago before I built the 582. It was in my Impala (3800 pounds before I take a seat). I went through three 700R4 in a month. I would pull them out discover what broke replace all of the broken parts with Heavy Duty parts and try again using the tried and true if you replace enough parts you will eventually make it bullet proof. Ain't going to happen. I replaced every part in the thing three times using stronger after market parts after factory Corvette and 4L60 parts failed. I replaced all of the usual suspects with billet and case hardened pieces, and still blew parts out the back of the case (which is hard on parts and cases).

It comes down to the old adage about the irresistible force attempting to move the immovable object. What gives every time is the 700R4 which is based upon the TH350 which was never put behind a BBC. Use the TH400 OD upgrade if you want an overdrive automatic. They are called 4L80e transmissions and even stock a ZZ502 won't break one. (you will need to go through it if you want more power with a bigger big block and run slicks but that is a future option).

Big Dave

That is a sensible way to sell a radiator. We are trying to shed BTUs and there is a direct corollary between BTUs and horsepower. Your 502 will put out an honest 540 horse at the flywheel as shipped. With aftermarket heads and a solid roller cam you can get 650 out of one. I run a BeCool in my 502 powered Suburban (I had to put that old ZZ502 someplace). My other car has a Griffin radiator. Both work great with zero cooling issues. Well that is not totally true because in the "winter", when the temp drops down to 50°F, here I have no heat in the Suburban; though that could also be attributed to the 160°F thermostat and fact that I still have my by-pass hose connected.

Difference between the two (besides price) is the BeCool uses a welded (fabricated from sheet stock) tank, and the Griffin uses a stamped tank which is epoxied onto the dual 1-1/2" aluminum core. When painted black the Griffin looks stock. No amount of paint can hide the slab sides of the BeCool so I leave it as is.

Big Dave