Our Listings : 500 EFI Uppers, Crane Cams #168731...10K in resale with these blue-top setup's...These are complete and ready to Run, hook them up to your ECM (MEFI) and go!!! I have 2 complete 500EFI uppers with sensors, throttle bodies, and injectors. These are an AWESOME upgrade for 454/502 MAG motors. The uppers ALONE without tuning will give 80-100hp good for 2-3mph gain, but with tuning and cams good for a 6-8 MPH gain!!! They are a DIRECT plug n' play on 94'-04' motors with the MEFI 3 computer. They match

this from the classifieds here... he has two intake manifolds/ throttle bodies from an hp 500. he claims directly that bolting these on a box stock 502 mag is worth 80 to 100 hp. i can't even remotely believe that that can be true but have not seen that hardware to know. seems to me that if it IS true then those set ups would be being bolted onto 502s as fast as they could be manufactured...

Not likely that a carb (with decent intake) to EFI conversion is worth much HP...probably 0 MPH

The entire valvetrain would have to be changed not just the cam. Also the exhaust and would need to be upgraded.

Wow if true adding those parts to a 502 mag which produces 415HP stock, add the low end of the number 80 HP you get 495HP which is more than a stock 500EFI makes which is 470hp. All without adding exhaust.

in every carb to efi comparison I have seen, peak HP is similar. drivability and economy are EFI strong points

The mefi computer of the right era might plug in but it's not programmed identical,the exhaust is different,as mentioned the valve springs are different, hp 500 made 470 vs 415 so your looking at a 55hp gain if you put ALL the hp 500 efi stuff on which clearly isn't included in the sale. As far as carb vs EFI,I don't know where that came from but XSM is asking about converting his mpi efi 502's not carbed motors,Smitty
Steve,if you were going to go that far buy good headers as a further upgrade and custom ground cams from Bob Madera,buy the mefi software and a 02 sensor and make a decent gain!

It could probably be done, but for that money plus the cost of exhaust and a retune of the ecm, you be looking at about 18k. Not worth it. You probably find a pair of very low hour 500efi's complete for less than 20k.

no no... it never occured to me to seriously consider this... and i think some of the posters above may have misread the ad ( or i did) ...

he is claiming a bolt on 80-100 by unbolting the stock efi from a 502 mag and bolting on this efi intake etc... no cam.

he talks about the cam later. i only cut and pasted the intake part. nothing in my experience suggests that there are any magic intake manifolds like that. or that that particular throttle body can be so much better. but i had to ask.

certainly you can get 80 hp with cams and valve trains and exhaust etc etc but it just took me a bit by surprise to see that sort of black and white claim in an ad that was likely to be read by knowledgeable people. it made me wonder. that intake and throttle body are straight off the gm ram jet 502 correct ?

those make 500 hp with al heads much bigger cams etc etc...

i don't know... i just thought it was interesting.

i am perfectly happy with my 502's. i made some semi dry headers for them when the gills got weak and they run great. if i was going to do anything at all i would have just put a 540 rotating assy in them which i talked about some time ago but just didn't feel like it.

no... this thread was all about that particular claim about that particular magic intake and whether i was just missing something completely.

I saw the ad too and thought it was BS. The price is also about double what it should be.