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I’m considering this upgrade to a 600hp Fitech multiport system. I have a 383 crate that dynoed at 485 HP. Has anyone done this upgrade that can speak to their experience? Installation, tips, advice, and of course my main reason would be to potentially add HP. How much HP gain would a system like this add? I’m seeing mixed reviews online and was looking for input on anyone who has done this.
I have converted my 77 to a FiTech EFI system.
You can look at numerous you tube videos showing dyno shoot outs between EFI and Carburetors.
You will find a fairly mixed message.
Bottom line, we put EFI systems on for easy start ups. Drivability, and often better fuel economy. Ease of dialing in the fuel mixture, computer controlled Ign timing. And sometimes just to replace a worn aging Carbureted fuel system.
But peak horse power. Not so much.
Which intake manifold your using may make some difference.
But a properly sized carb, properly jetted up will make the same if not more horse power than EFI.
just 2 different systems getting the same job done.
If your looking for ease of start ups, warm ups. Better general Drivability. and even a bit better fuel economy provided by keeping the mixture spot on 99 percent of the time. Go EFI. I did and I'm very happy with the difference.
If your looking for increased power. Look at better heads. bigger cam, things that will make more power. EFI helps with tuning, but it doesn't make more power.
The last three people I spoke to with a FiTech were struggling with the way they run........all three have dual plane intakes on their engine.....all three are like "no way" at me when I explain it is probably the intake that is doing it.......I mean, it is a shiny new intake on a shiny new engine and it was "designed" for it right? Wrong.
I wouldn't install another EFI on a dual plane intake......I have my reasons......but the simple answer is most of these unit's MAP sensors are only on one venturi....so it doesn't know what the other side is doing.....
I have installed two Sniper systems and I can say they are a very straight forward setup......but if you don't get the hyperspark ignition with it, don't waste your money....and use an single plane intake.
A properly tuned carb vs. a tuned EFI will always leave the carb as the victor for peak power on a Multi Port system......these Throttle body systems are a wash though.....exactly the same power everywhere......
Jebby
Last edited by Jebbysan; Dec 22, 2021 at 07:23 AM.
I’m considering this upgrade to a 600hp Fitech multiport system. I have a 383 crate that dynoed at 485 HP. Has anyone done this upgrade that can speak to their experience? Installation, tips, advice, and of course my main reason would be to potentially add HP. How much HP gain would a system like this add? I’m seeing mixed reviews online and was looking for input on anyone who has done this.
MPFI typically does not add power. If you have 485 you will keep it, and in some cases lose a few hp at the very top of your RPM vs a Carb.
I use the Holley set up. For both fuel and ignition. And I have a stout 434 with a 251/262 duration cam. About 600 lift that makes 652/602 for power. So for me the MPFI was for tuning. I am dialed in so well that anyone can drive this car in any situation. And not stall or experience any driving issues at all. I also run a coil on plug ignition just like a modern LS. And its often confused as a LS by everyone.
MPFI typically does not add power. If you have 485 you will keep it, and in some cases lose a few hp at the very top of your RPM vs a Carb.
I use the Holley set up. For both fuel and ignition. And I have a stout 434 with a 251/262 duration cam. About 600 lift that makes 652/602 for power. So for me the MPFI was for tuning. I am dialed in so well that anyone can drive this car in any situation. And not stall or experience any driving issues at all. I also run a coil on plug ignition just like a modern LS. And its often confused as a LS by everyone.
love your set up. Thanks for the feedback and picture.
I have converted my 77 to a FiTech EFI system.
You can look at numerous you tube videos showing dyno shoot outs between EFI and Carburetors.
You will find a fairly mixed message.
Bottom line, we put EFI systems on for easy start ups. Drivability, and often better fuel economy. Ease of dialing in the fuel mixture, computer controlled Ign timing. And sometimes just to replace a worn aging Carbureted fuel system.
But peak horse power. Not so much.
Which intake manifold your using may make some difference.
But a properly sized carb, properly jetted up will make the same if not more horse power than EFI.
just 2 different systems getting the same job done.
If your looking for ease of start ups, warm ups. Better general Drivability. and even a bit better fuel economy provided by keeping the mixture spot on 99 percent of the time. Go EFI. I did and I'm very happy with the difference.
If your looking for increased power. Look at better heads. bigger cam, things that will make more power. EFI helps with tuning, but it doesn't make more power.
exactly the type of feedback I was looking for. At this point, this is NOT a project I will take on.
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
Carbs these days have all sorts of easy adjustability which means they can be tuned to almost efi responsiveness when tuned with a vacuum gauge and an afr gauge. At a steady cruise speed such as going down the highway, you wouldn't see any difference between efi or a carb.
I would only do it for more hp. I wouldn’t get that. I have a 750 streetbrawler that is easy to tune and an afr gauge that helps me keep it in check. Not worth my time and money as I don’t care much to improve gas mileage.
MPFI typically does not add power. If you have 485 you will keep it, and in some cases lose a few hp at the very top of your RPM vs a Carb.
I use the Holley set up. For both fuel and ignition. And I have a stout 434 with a 251/262 duration cam. About 600 lift that makes 652/602 for power. So for me the MPFI was for tuning. I am dialed in so well that anyone can drive this car in any situation. And not stall or experience any driving issues at all. I also run a coil on plug ignition just like a modern LS. And its often confused as a LS by everyone.
This is exactly what I consider a perfect setup for a Gen 1, Kudos ! I have a RamJet intake that I may finally use with an aftermarket controller and with CNP also.
This is exactly what I consider a perfect setup for a Gen 1, Kudos ! I have a RamJet intake that I may finally use with an aftermarket controller and with CNP also.
Some 20 years ago I got a welder buddy to mod an LT intake for an HEI up top where GOD intended....sparks and water ****......and so.....same thing.....
I converted my RamJet 350 multiport EFI from the MEFI to the EZ-EFI 2.0 ... pretty much plug and play. I reinstalled my MSD distributor & 6A box and removed the MEFI distributor. Locked out the MSD and let the EZ-EFI 2.0 control the timing. Been on there like 8 or 9 years. Nothing difficult with these self-learning systems. Just a matter of wiring and plumbing.
Have you checked out the Edelbrock Pro-Flo 4 multi port? I've heard good things about it.
As a Brit used to seeing you USA guys doing all sorts of wonderful and 'adventurous' things to your cars and engines I'm really surprised (considering how long the Pro-Flo has been on the market) that few, if any of the Vette fraterity seem to be using it. Considering it allows you to have a full multi-port system (and the benefits that gives) for not a lot more money that a TBI system I would have thought you guys would be straight 'on it'.
As a Brit used to seeing you USA guys doing all sorts of wonderful and 'adventurous' things to your cars and engines I'm really surprised (considering how long the Pro-Flo has been on the market) that few, if any of the Vette fraterity seem to be using it. Considering it allows you to have a full multi-port system (and the benefits that gives) for not a lot more money that a TBI system I would have thought you guys would be straight 'on it'.
I had looked at it , however the intake as cool as it is.. Would not work for my Heads, it just wont flow enough. And has no material in the runner walls to massage out to get the proper fit and flow for my application
As a Brit used to seeing you USA guys doing all sorts of wonderful and 'adventurous' things to your cars and engines I'm really surprised (considering how long the Pro-Flo has been on the market) that few, if any of the Vette fraterity seem to be using it. Considering it allows you to have a full multi-port system (and the benefits that gives) for not a lot more money that a TBI system I would have thought you guys would be straight 'on it'.
just no power gain. That’s why. Efficiency is great for a driver and these are not in most cases. USA guys want good old fashioned raw power blocks.
just no power gain. That’s why. Efficiency is great for a driver and these are not in most cases. USA guys want good old fashioned raw power blocks.
I know that MPI rarely produces any power benefits when fitted direct to an engine with no further mods or changes..........but with the improved mixture distribution (using MPI with a cam/compression etc that would otherwise be 'baulky' in city use with conventional carburation) you'd have the opportunity to 'step-up' a little further with MPI using perhaps an even stronger cam and achieve both power increase and smoother running?
Yet I find I get that with my throttle body EFI.
And my conversion, total, pump, lines, computer, sensors, throttle cable fittings and throttle body came in at just a tad over 1,000 U.S.
Unfortunately for me, with shipping overseas. Import taxes and all. it cost me double that. But if I went for a really nice sequential port setup. quadruple that or more.
Yet I find I get that with my throttle body EFI.
And my conversion, total, pump, lines, computer, sensors, throttle cable fittings and throttle body came in at just a tad over 1,000 U.S.
Unfortunately for me, with shipping overseas. Import taxes and all. it cost me double that. But if I went for a really nice sequential port setup. quadruple that or more.
Here in the UK we generally accept that at the best anything that comes over from the 'States is at best the same price in UK Sterlingh £'s the same number as in US $'s. So $1000 is £1000. Usually though it is generally more........the shipping costs during Covid have been really high.
Multi Point EFI
