500EFI Intake modification/adaptation to Pro Flo EFI
11-10-2015 | 08:48 AM
#21
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From: Vancouver BC
My advise to you is ditch the MEFI system. The 500 EFI manifold is not as bad as everyone seems to think. I built a modified 540 EFI and had the stock 500 efi intake assy. with the top mount Tyler Crockett throttle body kit. This engine was 693 Hp at 6000rpm on the dyno. I had the same engine refreshed after 20 hours run time and switched to a Holley EFI system with an Edelbrock intake. This motor is 714 HP. Identical motor except the intake and injection system. So the 500 EFI intake costs roughly 25 HP on a 700hp engine. Mefi system is nothing but a headache. Not being able to tune anything yourself is a joke. My mefi system was always rich or not running right in some shape or form. With the Holley system you just put in the o2 sensor and it basically tunes itself. . Sending a mefi ecm back and forth for tuning gets old. Since switching to the Holley System the boat runs night and day different. It is worth every penny and selling your old system with net you half the cost of a Holley system. Call Mark at MER performance and get some real numbers from him. He has done both my motors and just got done doing a set of motors with ported stock 525 intakes and larger throttle bodies with the Holley Injection installed on them. Jeff Wurl
11-10-2015 | 12:46 PM
#22
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From: Tampa, FL USA
Jeff & Eddie: Thank you kindly for the information. Your experience will be helpful in the decision making process. I'm leaning towards modifying the upper plenum to accomidate a larger TB and possibly adapt in the Holley EFI. From what others have done with this manifold, it seems that the torque numbers are pretty good. I talked to Larry @ Raylar and he had plans to manufacure an 675HP upper, but the project went sour when his partner Ray and him had a falling out.
I think if someone redesigned the upper, overcoming the choke point so that the TB is in front, instead of on top, it would be a win, win for so many of us that have this set up and are limited to engine space or just want to keep the original "HP EFI" look. The question then would be how much CI can you build before the lower portion becomes the issue.
Haxby Speed or Anybody else wanna guess or give their thoughts on this?
I think if someone redesigned the upper, overcoming the choke point so that the TB is in front, instead of on top, it would be a win, win for so many of us that have this set up and are limited to engine space or just want to keep the original "HP EFI" look. The question then would be how much CI can you build before the lower portion becomes the issue.
Haxby Speed or Anybody else wanna guess or give their thoughts on this?
11-10-2015 | 01:21 PM
#23
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From: Tennessee
There was someone on here that had an intake made to replace his 525 efi intake. I believe it was a fabricated/sheetmetal intake that was absolutely beautiful. IIRC, it made some pretty damn good power as well. I'm sure the intake wasn't cheap, but it still looked very similar to the 525 but flowed much better. Anyone know who that was?
Eddie
Eddie
11-10-2015 | 01:49 PM
#24
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From: West Michigan
There was someone on here that had an intake made to replace his 525 efi intake. I believe it was a fabricated/sheetmetal intake that was absolutely beautiful. IIRC, it made some pretty damn good power as well. I'm sure the intake wasn't cheap, but it still looked very similar to the 525 but flowed much better. Anyone know who that was?
Eddie
Eddie
http://www.offshoreonly.com/forums/g...ml#post4017246
11-10-2015 | 01:56 PM
#25
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From: Maryland
I just think that this modified TPI system is grounded in tq not HP, ASM was the original designer of this manifold and supposedly GM bought the rights. I have to admit with my setup I probably had one of the best tunes and setups and reliability with mine the way they were. Instead of spending the time and money to redo and have a "maybe" you would be better off selling them complete and doing a manifold with the big throttle body. I took it as far as i could, then went big.
11-10-2015 | 02:03 PM
#26
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From: Vancouver BC
Jeff & Eddie: Thank you kindly for the information. Your experience will be helpful in the decision making process. I'm leaning towards modifying the upper plenum to accomidate a larger TB and possibly adapt in the Holley EFI. From what others have done with this manifold, it seems that the torque numbers are pretty good. I talked to Larry @ Raylar and he had plans to manufacure an 675HP upper, but the project went sour when his partner Ray and him had a falling out.
I think if someone redesigned the upper, overcoming the choke point so that the TB is in front, instead of on top, it would be a win, win for so many of us that have this set up and are limited to engine space or just want to keep the original "HP EFI" look. The question then would be how much CI can you build before the lower portion becomes the issue.
Haxby Speed or Anybody else wanna guess or give their thoughts on this?
I think if someone redesigned the upper, overcoming the choke point so that the TB is in front, instead of on top, it would be a win, win for so many of us that have this set up and are limited to engine space or just want to keep the original "HP EFI" look. The question then would be how much CI can you build before the lower portion becomes the issue.
Haxby Speed or Anybody else wanna guess or give their thoughts on this?
11-10-2015 | 03:34 PM
#27
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From: Tennessee
Thanks for the link BG. For the life of me, I couldn't remember where I saw it.
Eddie
11-10-2015 | 03:51 PM
#28
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From: OK CIty, OK
We have done quite a few where we removed the 500 efi intake and replaced it with the Holley single plane setup. We have also used the Edelbrock intake as well, but I prefer the Holley. We buy the intake without any electronics in a complete kit. This includes the intake, 2000cfm throttle body, fuel rails, injectors, TPS, IAC, ECT and MAP sensors. You just reuse your Mefi 3 ECM and harness. The harness will require some mods or we offer a replacement harness that is tailored to fit the intake perfectly. It's a really nice setup that works great. If you do reuse your harness, you will need to repin the IAC connector as the Holley comes with a Chrylers IAC instead of a GM. It's a simple mod but must be done for the IAC to work.
Several years ago, I built a 555 ci engine and tried to use the 500 efi intake. It was a pretty healthy piece with some pretty large heads, cam 10:1 compression, etc. The customer insisted on using that intake. Well, we got it on the dyno and it was a complete turd. It struggled to make past 600 hp and wouldn't pull beyond 4800 rpm. I knew it wasn't going to work, but I had to prove it to him. So, we pulled the intake on the dyno and put a Holley intake and 2000 cfm throttle body. The first pull netted 80 hp more. With some tuning, it made 700 hp. It was a completely different animal to say the least. This is an extreme example because it was to much CI, head and cam for that intake. My point is that the farther you get from a 500 efi, the worse the intake is.
Eddie
Several years ago, I built a 555 ci engine and tried to use the 500 efi intake. It was a pretty healthy piece with some pretty large heads, cam 10:1 compression, etc. The customer insisted on using that intake. Well, we got it on the dyno and it was a complete turd. It struggled to make past 600 hp and wouldn't pull beyond 4800 rpm. I knew it wasn't going to work, but I had to prove it to him. So, we pulled the intake on the dyno and put a Holley intake and 2000 cfm throttle body. The first pull netted 80 hp more. With some tuning, it made 700 hp. It was a completely different animal to say the least. This is an extreme example because it was to much CI, head and cam for that intake. My point is that the farther you get from a 500 efi, the worse the intake is.
Eddie
11-10-2015 | 04:07 PM
#29
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From: On A Dirt Floor
11-10-2015 | 06:49 PM
#30
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From: Tennessee
