[4BoltMainiac]

Hello to all. can anyone out there help me on this mark IV block that fell into my lap.. Its a forged crankshaft 1053 steel with 6223 cast no. The block is 384779 with big ol 4BoltCaps that are beeeefy...There is MarkIV Truck with the no. 10 cast at rear of motor. I will measure the bores to see if it is 366, 402, 0r 427t but would like as much knowledge on this as possible. Thanks much 4 B M

[68NovaSS]

I don't find a BBC number 384779, you sure it's not 364779? That would be a 366 truck, 4-bolt, '68-'90.

The 6223 crank comes up as a forged 396/402/427

http://web.archive.org/web/200805130...ec.com/bbc.htm

[4BoltMainiac]

Thanks for the numbers 68novaSS. I was hopin a 402 or 427 but ya cant win em all. my question is this.. is a .060 over on my 366t to make 377 c.i. worth it? I am interested in a durable torquer that can tow and offroad... Nothin too outrageous say 325 horse with 379 cu ft/lbs of torque at 4500rpm? (not sure if this is accurate)
Just somethin that will out tow the 379 detroit diesel currently runnin strong(she
goes well with the 4spd o/d standard trans) not known to be a mighty tow motor but she sure has been good to me.
I know she wont last forever... If i could build this BBC mark IV say to what chevy mightve put in the scottsdale if they WERE NOT trying to compete with the SAKI_ROCKETS on fuel mileage... Or save the crankshaft ,polish and balance her to a 402 or 427 and just upgrade to one of these blocks? Tight budget like most of us so got to be thoughtful and well organized to do it right...
Thanks again for the knowledge. 4Bolt

[BOBCRMAN@aol.com]

It takes a lot of $$$ to build a hot 366. Even then you would be dissappointed. EVERY 366 I buy gets the main caps,crank and rods removed. The block is scrapped and certain head castings are kept.. In over 40 years of building engines I have rebuilt less than half a dozen 366 for private (non-commercial) customers. Most hate the 366 and opt for a 427 or drop back to a 350..

[machine shop tom]

Think of it this way. A 366 is like a REALLY HEAVY 350...........

Maybe breathe a little better, but $$$$$ to many any power.

tom

[4BoltMainiac]

Thanks BOBCRMAN and Machine Shop Tom for the good knowledge... I am ready to start teardown for the crankshaft, rods. Since these heads fall under 454 with large oval do I keep em? Thanks again for the help and I welcome all your information and innovation. 4Bolt

[airboat]

Why Bother?

I guess I should expound on that. I think you can take a roller cam 350 and put a stroker kit in the short block for $500 torque plate hone and decked plus less than $1000 for the 383 rotating assy. So many choices for heads the Vortecs or great aftermarket iron. What you are looking for the stock cam would probably do it but budget depending you might do a little better.. Roller dam 5.7 or 350"s arn't worth that much that it would make me build a tiny bbc, unless it's going to be spending it's whole life carrying big loads uphill. I like 454 and bigger but I imagine fuel burn is a consideration. I would run a 383 and make sure cooling is good.

However if I was in a position where I could make a fine running machine for not much cash infusion like if the engine runs good run it. If you don't know how it runs I have been doing cam break in's just with garden hose hooked up to waterpump inlets sitting on the oilpan and some jack stands or blocks around it. 366 would be like a Detroit for sure. You check my videos my son is liking throttle a little to much... http://www.youtube.com/my_videos?feature=mhum