After a long wait, the 425 is being torn out of my H&E DeVille. Going with several ideas that I got from this forum, and other ideas from Marty at MTS.

The plan and parts:
1. converting to a ported-out 472 intake painted stock blue, no need to re-do the AC brackets like w/ the edelbrock
2. carb re-tune
3. timing advance
4. shift improver kit
5. 500 exhaust manifolds, x-pipe dual exhaust conversion w/ fleetwood crossmember, no cats, high-flow mufflers
6. full head work including porting, grinding
7. all new valves, springs, lifters, etc
8. #5 MTS cam swap

Any thoughts? Still hoping to come in under what a 500 swap would have been when you add it all up, plus I'll have the satisfaction of keeping the 425. Honestly, I've started having second thoughts about maybe going with a #3 cam rather than #5 for off the line performance. Hoping the head work makes up for this. Going to leave the rear end alone for now I think and see how it runs. It will look totally stock too, which I want. Getting excited to see what the finished product will be. Would love any feedback.

Joe

On the 472 intake... make sure you get the AC comp mounts from the 472 intake.. not sure if the front one is the same but I know the rear mount is not the same...

No one else? Thought this would generate a lot more discussion.

Sounds like a good setup to me. I'm not too impressed with the power of my 425; very tame. I blame the cam the most. I didn't look at the specs on the MT5 but I don't think you need to get too wild; anything will be a big improvment over stock. I didn't realize 500 manifolds flowed better. I will be on the lookout for some cheap ones. Let us know how yours turns out.

Like to know how this works out for you. Sounds exciting.

You planning dual exhaust? How are you planing getting by that left side crossmember? There is a guy on ebay who is manufacturing crossmembers for GM A-bodies. Don't know if they would make it across a C body.

got a crossmember from a fleetwood w/ duals that should work. i actually decided to do a few more things, including have headers built, and up the ratio on the rear end as well. i'm also going with a better stall converter. i consider this project an experiment to see how much we can squeeze out of the 425 without going into the bottom end at all. there's no reason why 425 cubic inches, once the bottlenecks are out, can not provide all the torque that is needed without having to swap to a 500 ci engine.

Hopefully the engine will realize it has 425 cubes. How the heck did GM choke that thing down to 180 hp? oh yeah, small cam, small valves and restrictive manifolds. I was looking at those MTS cams and since the MTS3 is an efficient fuel mileage cam then I would go on the wild side and try the 5. I heard somewhere these 425 Caddies were great in street stock drag racing or some class that allows almost no modifications. I assume they gut it to get the weight down. Keep us posted 79vert. Since yours is a custom convertible I assume there will be no drag racing.

I'm really looking forward to the finished product, hopefully it will be done in the next couple of weeks. We're trying to hunt down a rear end right now that will get the new power down. The MTS # 5 cam is exactly what I chose. The heads should be back in about a week from getting totally redone and ported. I heard that these engines are used for dirt track racing somewhere. Thanks for the feedback. Oh yeah, no drag racing for me, just some red light to red light fun.

. Honestly, I've started having second thoughts about maybe going with a #3 cam rather than #5 for off the line performance. Hoping the head work makes up for this.
Joe

Actually, headwork usually is more noticable in the mid to upper rpm range, not the low end as much. I would still go with the #5, as the lower peak range of the #3 may not even utilize much of the gain from the heads...