i just called on a 86' formula 357 with cyclone 400's

how do these compare with the 420's (total hrs out of them, peak power rpm, true output, etc)

whats the innerts ( cam, valve train, crank, etc)

seems 86 was their last year and the 420 or 425's basically replaced it??

I have the 400 Cyclones in my Excalibur Hawk 40....I don't know the specs but they do have steel cranks and crane gold roller rockers on them....mine have aftermarket Edelbrock RPM intakes and 750 Demon carbs....push the tank to 60mph best on GPS...I think the 420 came next after production of the 400's....Fred

400 MCM Cyclone
454 cid
8.8:1 CR
Rectangle port heads
Aluminum Intake
4 bolt main block
Forged pistons
Forged crank
Aluminum roller rockers
Hydraulic lifters
lift @ valve .530in .551ex
Don't know these engines, but they sound like a good combo....
even if they need a rebuild you've got a good foundation in the short blocks...lets see a little compression, port work, higher lift cam, dominator carb...................

Sonic30ss....where did you find those specs?.....Thanks for them....Fred

Bone stock true power about 390 hp, hours --well depends on how you drive them, maintain them etc. but doing everything rightyou could probably see 5-600 hrs before opening to 'check' bearings, valvetrain etc. With slight mods they will put out 475 hp comfortably, as sonic said they have the right parts to start with.

You will most likely need an aftermarket exhaust system to get 475hp out of them.

HAD MY 400'S APART ABOUT A YEAR AGO THEY ALSO HAVE THE DIMPLE 7/16 BOLT RODS!THESE ARE SOME OF BEST THAT GM PRODUCED.I BELIEVE THE ONLY DIFFERENCE BETWEEN 400'S AND 420'S WERE THE EXHAUST MANIFOLDS.420'S USED THE GILL OFFSHORE STYLE.ALL GOOD PARTS ON THE INSIDE.GOOD LUCK