MPI compatability
#3
Platinum Member
Platinum Member
Aren't the mag efi units port injected?
Why couldn't they use some filler epoxy and build-in the ports in the manifold to approximate the head openings? That would minimize turbulence and injecting at the port would eliminate the fuel dropping out of suspension due to low runner velocity.
Thoughts?
Why couldn't they use some filler epoxy and build-in the ports in the manifold to approximate the head openings? That would minimize turbulence and injecting at the port would eliminate the fuel dropping out of suspension due to low runner velocity.
Thoughts?
#5
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Location: Spicewood, Texas USA
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Merc used that rectangle port EFI system on the peanut port 7.4 EFI engines in late '96 & 97. The engines were called 7.4LX and rated at 330 PSHP. So, even thought there is a port mismatch it appears to still have been worth a 30 PSHP gain on the 300 HP 7.4. The mismatch does not seem to be as critical in a port injection environment since the fuel is injected directly into the port. However ECU programming would be quite a bit different than the Mag.
#9
Charter Member #1171
Charter Member
Depends on which 330 you are talking about,,, I would assume you mean a carb 330. My 97 7.4LX MPI was 330hp and had the same injection system as the mags.
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#10
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Posts: n/a
Re: No
The intake ports are a big mismatch. The 330 has a small oval port and the Mag EFI has a large rectangle port.
This is because actually the efi manifold is not a large rectangular port. The ports are very rectangular but are some what narrower and shorter then rect port heads. They are actually the same size as the large oval port heads except the rectangular shape means they mismatch in the corners and the floors are a little higher but they are quite a bit, 3/16 " narrower and 3/8" shorter then rectangular port heads and so,,,, the MAG efi manifold is a mismatch no matter what heads you use, something that I always thought odd.
These are avg dimensions from some heads and manifolds I have measured over the years. as you can see the merc manifold is a closer match to the oval ports altho with square corners the heads would need some work as large manifold to smaller head is worse then smal manifold to larger head because of the step created in the flow path.
GM Large rec ports 1.6" x 2.35"
GM Large oval 1.5" x 1.9"
GM peanut oval 1.5" x 1.4"
Merc Mag efi manifold 1.4" x 1.9"
Last edited by ursus; 03-04-2003 at 11:38 AM.