ATK 383 Long Block Update
I have a little over 100 miles on my ATK 383 motor so far. If you don’t remember me, I’m the red cap guy! ATK recommends 34-36 degrees of total timing, so I set mine at 35 degrees. I do have the vacuum advance hooked up to full manifold vacuum. I also have the carburetor set pretty good. I am going to advance the timing to 36 degrees and adjust the carburetor accordingly just to see if it I get more performance out of it.
I am very impressed with how the motor is running. I’m following ATK’s break in procedure to a T, so I have been easy on it. They recommend a few accelerations to about 4000rpm occasionally during the first 150-200 miles. The first time I did it, it was difficult to get the grin off my face. Now, I fully understand when people talk about their car really pulling hard. The PO was building the car as a drag car. It had a 355 with a pretty aggressive cam in it. It’s difficult to say what motor was more powerful because it had 4:11’s that I replaced with 3:73’s and the redline was at about 6500rpm with the 355. I believe the redline for this 383 is 5200rpm. But, my 383 feels more powerful and the low end torque of it is on a whole different level. I think this 383 by far outperforms the 355, but I have no idea as far as actual numbers are concerned.
The motor is a full roller motor, so I didn’t have to break in the cam. I did change the oil and filter after the first 50 miles even though I didn’t have to. But, I’m very particular about my vehicles and figured it’s not going to hurt anything. I also replaced the flex fan with the Hayden fan clutch and 7 blade OE style fan. I was shocked at how much of a difference that made. My temp gauge dropped 5 degrees, the sound is minimal compared to the flex fan and the belt is not loosening after every drive and hasn’t been thrown off yet. I’m very happy with that.
After a few more miles, I’ll need to check the valves for adjustment. I believe at 500 miles, I will change to oil again. But, a break in oil is no longer needed. I have been using ATK’s recommended Joe Gibbs BR40 break in oil and a K&N filter. I know I will need to use a conventional 10w-30 with the zinc additive after that. I have to say that I’m very happy and pleased with my 383 from ATK. I would definitely recommend this motor to anyone looking for one. ATK’s customer service is great, too. My only suggestion would be to quadruple check that the red caps that are shipped on a new radiator, if you are installing a new one, are definitely out BEFORE you attach the hoses!!!
I think after my bank account recovers I’m going to replace the car’s complete wire harness and look for some bucket seats. My Chevelle currently has those plastic drag racing seats that are not very kind to my back.
Thanks again for everyone’s help!