I'm shopping for a fan for my 70 chevelle , what is the size i need to get? i have a 454, and a 4 core rad. i will be using the stock fan shroud
thanks

I believe the stock fan size is 18 inches for the GM 7 blade clutch fan which is what i would run with a std or HD fan clutch depending on your needs. I have also see 17 inches listed for the clutch fan too for the BBC in 69/70 along with 18 iches so check that out,maybe both were used.

I run the std fan clutch (plus 18 inch) in my 1969 396 with a 4 core rad even though at times it could use the HD fan clutch in heavy traffic on a hot day which would cut in earlier for better cooling.

I had a HD han clutch (with the thermostatic engagement spring) on my 396 but they are always about a 1/4 engaged at all times for the HD cooling and man that sucks in a lot more dust/debris/crap and just trashes the eng compartment in one afternoon cruise.
I also noticed that the std clutch never fully engaged when hot,it always slipped a little
after it was engaged but when the HD clutch was fully engeged it was noisy and took some power away along with pulling in a lot of dust/dirt into the eng compartment.

I then swithced back to the std cooling clutch (also with a thermostatic engagement spring) and the eng compartment stayed much cleaner than when i was running the HD fan clutch but it did run hotter in traffic,it's a trade off which you would have to decide on.

Don't run the cheapo stock 4 blade non clutch fan,they are garbage and don't pull much air through the radiator in slow traffic.

You can get the clutch fan and fan clutch through Yearone,OPG,but you can get the clutch cheaper thorugh a local auto parts store. As for the fan some local parts store can get a 5 blade replacment clutch fan that works decent at 1/2 the cost of the GM 7 blade but it depends on if you want the stock appearance or if you don't care about that.

Scott