1988 Merc 420's
 

Does anyone know what Brand parts they put in the Bottom End of these motors? Im going to be pulling a couple down in the next couple months. I see Crane Gold rockers under the covers, have heard Crane Cams, 800 Holley on Weiand Team G Intake. Rec Port Iron Heads. Anyone know what the stock Compression Ratio is? Thanks! Tim

I believe they are 8.8:1 with trw 2399 pistons gm dimple rods and gm forged cranks

Correct me if Im wrong....the 420hp motors are 496in? If so...would be an aftermarket crank?!

If not..I may just sell the COMPLETE motors? Was planning on Hyd Roller Cam..."better" Intake and Quick Fuel 850 carbs......

I will correct you then. They are 454 cubic inches

420 is a 454, forged crank, 7/16 dimple rods, forged pistons, rectangle port heads, Crane 132561 flat tappet cam, Crane gold rockers, some had Weiand Team G intakes, some had GM intakes, Holley 800 carb, and most had Gil exhaust.

Interesting! Thanks...ya...got the Gil Exhaust.....I may put these motors on the Market ant start from Scratch! Serious! If anyone oyt there is interested....one motor has 120 hours ...other gas 3 hours...yes...3! Have the build sheet from CK Motorsports they charged the previous owner $7K in the re-build...NEW Crank, cam, lifters, etc..... If I can sell these...and they run GREAT! I will start with new Dart Blocks and go NUTS!! hahaha Lets talk!!

WOW! where the heck did I get 496 in my brain??!! lol Probably cuz that is where I am leaning! lol Thanks

what are your horsepower goals? That is a pretty decent foundation to start with depending on your goals.

What is reusable in these motors for a little more power.Also is the components quality enough that you could reuse almost all of the motor on just a stock rebuild even the camshaft if it checked out.

Reason i am thinking is seeing all these older 420s up for sale has me thinking to sell my SBC CMI and tail pipes for 1500 and maybe get another thousand out of my fresh nothing to special 300 horse 355 and buy a 420 to put in my little 19 footer..

Dumping another grand into sbc heads to get 30 horse doesn't add up to me when i could buy a 420 for 3000 and do a simple rebuild for a grand if the motor is in decent shape to begin with and have a base if i wanted to build 500 horse later if I chose to.