I have the original 400 out of my 67GS400 convertible. I currently and in the process of putting this into it a mildly built 70 455 stage one with a mildly upgraded TA cam the new oiling pump assembly but I have the original motor that will need a rebuild but I think I would like to build the 400 if possible.. How crazy can I go with the 400 with readily available parts... Or should li not worry about the 400 and just build another 455 block I have sitting around? All advise greatly appreciated? Michael
Communicatin', aside I get what you're asking. You have one built 455, and another buildable, so go with those, and maybe build the 400 to stock specs, and pickle it. If you use Joe Gibb's assembly lube, it should be good for a long time in pre-break in condition. (the Gibb's is a grease and will stay in place longer than some of the "thick oil/gel" types of assembly lube) Just make sure you have all the internals "pickled" to prevent any surface rust or "sticking" from dry-out. All of that is based on your age and intentions of keeping the car and for how long.
well ad you know the crank, bearing, rods, cam etc are all the same. the piston is of course different but a proper size unit shouldn't be a bank breaker. you will be limited on valve sizing due to the smaller bore hampering flow. but no reason it cant be a string runner with small valves.......but if it's the numbers matching motor why risk it even having the chance to get broken. we have the original 400 for my brothers 68 sitting around, just in case
Michael, We all face the same quandary as we work on our projects. My opinion is that if you happen to own an extremely rare or historically significant car, then that particular car and the hobby at large is better served to keep the car original. When it comes to drive trains, it is simple to pull the original stuff and go to town with "disposable" non numbers components. This leaves the door open for originality, without doing irreparable damage to replaceable components. That said, I have a 67 GS400 convertible with a 4 speed that has a 400 engine with a mild tune in it. The body and frame are flexible enough that this car can not be considered a performance car, so I am very pleased with the 400 engine. I ended putting together a 100% correct engine with all correct castings, date codes and original 4 speed carb, so unless you look for the stamped serial number on the block, it appears correct. I considered a 455 because my car is not a numbers car, but opted to go with as original as I could get and now that it's done, I don't think I could use the 455 torque effectively other than to make smoke In the end, however, it's important to remember that the car is yours and "he who has the money makes the rules", so do whatever makes you the happiest!
Keeping the original 400 close to factory specs makes sense. Maybe a mild cam upgrade, overbore, and minor head work. Nothing too much. However building a "crazy" engine to me would include milling the deck which would remove all the stampings from the original block. I'd also overbore a 400 out to 430 specs. If you want "crazy" take the easy way out and go with the 455. A lot of "crazy" needs to be added to a 400 to make up for 55 cubic inches of power.
I’m on my second GS400, and like the first it had a 455 transppant. I have the original engine stored but have not once been sad that I have more cubes tgan the fender badge says. Patrick
