454 - 502 exchange

Guardian · June 11, 2003

I recently blew up my trusty 454 on a trip over the mountain pass, and I'm currently considering my options. I'm thinking about putting in a 502. I hear that it gets about the same mileage as my 454, but puts out a lot more torque. Anyone got any ideas or advice on the subject?

Oh, I also tow a 30' gooseneck trailer weighing in at about 18,000 lbs. Also looking at picking up a 30' fifth wheel.

Thanks for the advice.

Robert J. Simmons

1991 Chev K2500, ext cab, full size bed, 4 wd (best truck ever made)

steppetoe · June 11, 2003

All I can tell you is that GM does offer an emission legal 502 retro kit for 454 trucks. I don't know what years are covered. You can go onto the Scoggins Dickey site and look under crate motors, or any site that offer GM Performance crate motors I guess.

americanmuscleman · June 11, 2003

Steppetoe is right. GM offers a 502 crate motor conversion kit designed to replace a tired (or in your case blown) TBI 454.

A 502 has the same deck height and block dimensions as a 454, so a 502 should be a direct swap. I'm sure you have to use a newer generation block so you can use your factory knock sensor, oil filter housing, and oil pressure sending unit... but dimensionally they will be the same and a direct swap.

You'll see a nice torque gain with a 502. If you keep the stock heads, you probably won't see a big horsepower gain due to the fact that the factory TBI 454 heads were a hinderance on that motor... so they especially will be on a 502.

Guardian · June 11, 2003

Thanks for the info. The 502 I'm looking at is a complete crate motor, just missing intake manifold and ignition system. I was considering rebuilding the 454. BUT someone just told me that the 454 is known for breaking or cracking cranks at around a 100-130 thousand miles. Anyone know anything about this? I would like to have the torque of the 502, if I could do that safely with the 454 I would probably just rebuild it.

Thanks for all the help!

Robert J. Simmons

bcfitzsimons · June 13, 2003

I can't remember if the 454 cranks that were put into late-model trucks were cast or forged. My bet is that they're cast, to decrease cost. If that's the case, then almost every cast crank in a high-torque application sees significant wear by 100-130K miles.

What a bummer. Can you imagine loading up your truck and then snapping the crank? I've heard driveshafts break, and I thought THAT was loud. I couldn't even imagine a crank snapping in two.

Out of curiousity, what happened to your 454? Did you make a window in the block?

Fitz.

bcfitzsimons · June 13, 2003

Oh, and by the way-a good forged crank will cost you between $500-$1500. Summit sells a bunch of them for 454's-it's only a matter of how much you want to spend (naturally . . . )

Fitz.

Guardian · June 20, 2003

Thanks for all the great info. I've talked it over with my wife and we've decided to go with just buying a new truck and selling the other as is.

No window in the block, but it did sound about equivalent to my 12 gauge going off. Finally did get the motor out. Turns out it was an oil pump failure. That seized the main bearings, damaging the crank, and then destroying the connecting rods. Which ruined the block (So that's what all that grinding noise was!)

Tomorrow I go over and get my new truck! 2003 Dually CrewCab, 4x4, longbed, with every option I can get! Hope my wife lets ME drive it sometime.