Looking for advice on 454 or 502
 

Looking for some feedback on which avenue to take.

I have a 454 efi with a bad crank that needs a rebuild. I just bought a rebuilt 502 long block thinking I could just swap parts and flash the ECM for the 502. Well it turns out the 502 has rectangle intake ports and my mpi is oval. So that won't work. Here is where I'm not sure which direction to go. The 454 heads won't work on the 502, chambers are to small and the 502 has high dome pistons.

Do I rebuild the 454?
Buy new heads for the 502 and use my 454 efi setup?
Buy another efi setup for the 502?
Swap the 502 over to a carb setup?
Is it possible to convert my oval port efi setup to rectangle intake ports?
How big a pain is it going to be to program the ECM for my setup? The 502 is suppose to be around 425 hp

Not trying to throw a ton of money at this, each option seems to be another few grand. But either way ill have some parts to sell.

Thanks for any advice in advance.

Personally, I would just build a 502 carb motor and be done with it...two years ago I had both my 454s rebuilt and if I had it to do over I would have bought a set of used 502s...I would have been happier....just my .02

I agree. Throw an carb and intake on and be done. Much better starting off with a 502 over the 454. To put the oval or round port intake on the 502 would be a waste.

Ebay seems to think that the 454 and 502 mpi intake is the same part....

What all is involved with switching to a carb setup? Do I need a new wiring harness? Can anyone recommend a intake and carb setup that works decent without breaking the bank?

I did the conversion earlier this spring. I bought a victor jr intake and a Holley 850 carb. I also bought a thunderbolt 4 wiring harness and distributor from someone on here. After that, just bolt it all on and go. The harness and distributor can be had on hear for very good deals. Think I paid $75 for all of it.

I ended up going with a blower so still have the carb and intake sitting on the shelf. If you decide to go that way pm me and I would work you a deal for the carb and intake setup.

What comes with the Thunderbolt wiring harness? I need an ignition module of some sort correct?

Yes. I bought mine on here. It came with dist, harness and module. Unplug the old one and plug in the new one.

If you have a complete long block 502, do the carb/intake setup. IF your 454 was a 385HP mag, then you'd have the rect port intake like the 502 mag. But you obviously had a 7.4L 310HP MPI version with vortec heads.

I'd like to run the 502 to be honest. I've been looking around for a 502 mpi setup too, just seems to be bad timing. I found one setup for 700 but its a mefi 1. And has had the intake etc... all ported. So I'm kinda dragging my feet. Feedback?

Otherwise its buying intake, carb, wiring harness, distributor and ignition module. Did I miss anything?

Honestly, I wouldn't get hung up on having EFI..just build a nice carb motor and enjoy it...spend the extra cash on a decent set of headers...if you really have your heart set on EFI, I would use the 500efi intake...

I saw a few folks selling 500 efi's wasn't sure if they would work without needing to do more motor work. I'm assuming a nice intake carb setup will get me close to fuel economy and HP of MPI.

Yeah, that I don't know...not an engine expert at all, but if I was gonna build a efi 502 motor I would build a 500 clone...if it were me, I would use the money I was gonna spend on the efi system to build a healthy carb motor for sure...

A 454 mag mpi and 502 mag mpi of same vintage have the same intake manifolds, the 454 efi 310 hp has all junk parts, oval port intake, cast crank, cast pistons, etc, Smitty

Ended up going with a carp setup for now.

I think its a good choice. Not to mention my efi setup was heavy!!! Think it weighed over 90 lbs when I shipped it out.