handfulz28

Just poking around for fuel injection intakes since I occassionally entertain the idea of a carb to EFI conversion.
Came across these on ebay and noticed the ASM is different from what I normally see as a Merc MPI intake.
Can anybody shed any light on the different applications?
Thanks,
Michael

Bryan Rose

the top one looks an awfull lot like the base on my 500 EFI intake....it just is not blue.......Maybe

Bryan

Pat McPherson

The AZ Speed Intake was used on Volvo Penta 7.4GSi (454Mag) and 8.2GSi (502Mag) marine engines. Merc Racing also used them on the 500EFI and still uses them on 525EFI engines.

The Merc Intake was used on their 454MagMPI and 502MagMPI engines.

The intake manifolds are not vary different but the intake plenums are. The AZ Speed plenum has less volume and the TB is in the front vs on the side like the Merc.

From what I've read and been told, either works vary well up to 500HP. The AZ Speed works better then the Merc on higher power engines.

handfulz28

Thanks guys. And I think I just learned a little more technical terminology: intake "manifold" versus "plenum".
It looks like the big difference is the "mating area"? Essentially a long- vs short- runner?
So the Merc manifold definitely needs the Merc plenum, but I wonder if the AZ intake would accept the Merc plenum? Just a thought.
Merc plenums are probably a lot easier to come by than the AZ setup I bet; probably best to find a 500EFI setup complete if that's what I wanted?
Thanks,
Michael

Pat McPherson

The Merc 454/502Mag fuel injection systems do seem to be a little easier to come by and they are less $$ for sure. Like I said earlier, they are great for under 500HP. There are modification that can be done to the Merc manifold to shorten the runners but I'm not sure the $$ are worth it.
I would say that the Merc Racing/AZ Speed setup would be the way to go for 500HP+ application. That's if you can find a unit for reasonable $$. Merc Racing didn't use there own on 500+HP for a reason.
As for swapping the plenum, a Merc plenum is not going to work on the AZ Speed intake. You could probably modify the Merc intake to except an AZ Speed plenum, but...

kennyo

The AZ plenum has shortened runners and is extrude honed. You can shorten and port a merc plenum yourself . I did mine.

handfulz28

OK, so let's say I can get over not having the blue paint and EFI500 placard. Will the MPI manifold bolt to Mark IV 454 MAG heads? I've been doing a lot of reading, and somewhere I saw there's a difference in port size between the manifold(s) and the heads.
Am I crazy/stupid to consider just bolting on an MPI setup to an old carb'd MAG?
Thanks,
Michael

engine

The manifold used on 502 has rectangular ports to match the rect intake ports on the heads, you have to find out if your engine has round/oval/rect ports. I would not recommend to install rect port intake to other heads than rect. Just check the casting number on your heads and do a google.

I do believe that the Magnum EFI intake/Plenum requires less space in front of engine than the 500EFI so you have to check if you have the space needed in you engine bay if you decide to go Blue 500EFI intake/Plenum.

The Carb to EFI conversion will be a very interesting challenge and upskilling experience for you. It will cost you more than the benefits of EFI is really worth for one engine but I believe that your new knowledge will pay of in the future.

I´m in the process myself to swap from MagnumEFI intake to Blue 500EFI intake on my 502(515) I will buy a Holley commander ECU to be able to tune it myself.

Pat McPherson

Nice, that will be fun...
AZ Speed & Marine is now offering packages of software, ecu, and harness as well...

handfulz28

Thanks again guys.
I've got twins, so all the expense/effort is x 2. But I'm sure the basic reward won't be quite double.
I've got plenty of room in front, it's actually the height that I need to consider. I don't think there's much more room on top of my carb setup as is.
I know from everything I've read I should just stick with a rebuild/upgrade of these puppies, but keep it carb'd.
Thanks,
Michael