GMPP Ram Jet 502 vs Merc HP500/525 EFI

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08-25-2007, 05:06 AM

#11

BadDog

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The link shows the specs of cam and PN
http://www.gmperformanceparts.com/En...9121&engCat=bb

08-25-2007, 06:45 AM

#12

Pat McPherson

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Quote:

Originally Posted by BadDog

The link shows the specs of cam and PN
http://www.gmperformanceparts.com/En...9121&engCat=bb

That does look to be the same cam as the ZZ502. All the EFI gurus I've spoken to say that with 110°LSA it is not a great cam for EFI.

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08-25-2007, 08:03 AM

#13

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500efi
Crane HR-292-2S-14 IG
292*/298* @ .004"
230*/236* @ .050"
.598"/.610"
109* ICL
119* ECL
114* LSA

ZZ502 / Ram Jet GM#12366543
224*,234* at .050"
.527", .544"
110 LSA

=============================
Also.....
Merc Blue has adj roller rockers / cast iron rect port 119cc chamber heads / crane hyd roller lifters

GM ZZ502/Ram Jet has stamped steel rockers/aluminum GMPP ovalport heads with 110cc

More differences but that's the basics.

===================
LSA is not everything when considering a cam for EFI. It's more overlap in consideration with intake vacuum levels. Taking the same cam in same motor but just changing LSA will effect overlap and thus intake vacuum levels. Major components like intake manifold design can also greatly influence intake vacuum levels. LSA is just measurement between intake centerline and exhaust centerline.

08-25-2007, 08:32 AM

#14

ROTAX454

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Quote:

Originally Posted by Pat McPherson

That does look to be the same cam as the ZZ502. All the EFI gurus I've spoken to say that with 110°LSA it is not a great cam for EFI.

Same cam: 12366543 224intake 234 exhaust

08-25-2007, 08:36 AM

#15

ROTAX454

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Quote:

Originally Posted by handfulz28

http://www.gmperformanceparts.com/En...9121&engCat=bb

Other than some obvious issues with marinizing the crate Ram Jet, just how far apart is this motor from a Merc blue motor? Is a "GM" MEFI 4 easier to get access to than a "Merc" MEFI 4, for custom programming? Is the Merc HP EFI intake a GM part?

I can offer some assistance if you wish to go with the ZZ platform. I have a fair amount of knowledge/research/dyno time that may help you.

08-25-2007, 08:06 PM

#16

TRYME

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Post Them Please, Im Intrested Too Thanks

08-26-2007, 06:37 AM

#17

thunderusone

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Mefi 4 ECM is the same on both motors. Anyone that can program marine MEfi's can program the crate motor.

08-26-2007, 01:56 PM

#18

Bubbletop409

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Quote:

Originally Posted by kennyo

Hell Dude, you can get a 572 cheaper than a freakin' blue motor!

Keep in mind the 572 is based upon a tall deck block, this raises and spreads the heads, and could cause an exhaust alignment problem.

62 Bel-Air 409

260 Eagle XP HP500EFI

2002 Corvette M6 Coupe