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Lets have a vote...

11814 Views 37 Replies 9 Participants Last post by  terrible one
I am stuck on whether or not to go multiport EFI or a performance Quadrajet from JET.

With the EFI, I have to use the stock manifold. I can get one of these, fuel rail, and throttle body. Pretty expensive. However, I have been told the EFI manifold is crap for flow, and even with a lot of porting would barely catch up to a stock carb manifold. Also, the EFI system is much more expensive of course.

With the carb, I would get a pre-EGR manifold for the better flow, port it, and run a JET Quadrajet on there. Everyone is telling me this is what I should do, and save money and get better performance.

Now, the catches.

Others tell me that the runners on the EFI manifold are about the same. No one has proof of either. I am almost tempted to buy it just to see for myself. I also was looking forward to the tuneability of the EFI setup, and just the sheer broad powerband performance and coolness. However, it has been said that it would come back to bit me in the ass because it would be such a pain and if something went wrong I have to troubleshoot, yadda yadda yadda. The guy helping me is really wanting the EFI thing to happen.

Now, with the carb, I know I will always wonder how the Megasquirt/EFI setup would have worked out. Plus the fuel economy wont be as good. Some people say big difference, others little. Also, a carb is always a carb, and won't have the computer tuning the MEgasquirt has, the awesome response, the almost limitless powerband, etc etc. Also a carb is just simple.

Okay, feels good to get all of that off my chest. This has been killing me guys. I don't know what to do.
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Ah crap forgot to add the pole. Oh well who cares, just type your response. I'll get more info out of that, and everyone always does anyways.

Thanks guys.
I have an EFI manifold here. Find out just what is supposed to be so restrictive on it and I'll have a look.
Runners are supposed to be the problem, the size and curves. I would really like to make this thing work, but then again it is a MUCH more expensive route, dunno if it would be worth the performance gain in the first place...

Thank you
Really, how much difference will there be over a well built, well tuned carb?
Not a ton of difference, but there WILL be a difference. Thing is Quadrajets aren't known to be easy to tune. A computerized system that's able to take feedback from the engine will always outperform a carb.

I've heard from some people that Al at MTS says the EFI manifold outperforms a carb one by a big margin. I've heard from some people that the Torque Inc crew says they don't flow for crap. I also know the factory rated the EFI cars 20hp higher than the carb ones, but that the factory ratings aren't exactly that accurate either. So really who knows. If you get the EFI unit you could have it and your carb intake on a flow bench and let us all really know what's up.
Wouldn't a holley or eldebrock be better. I always heard they were Quadrajunk. Could be wrong though.
Nah, a well tuned Quadrajet will out perform those carbs hands down. But it needs to be well tuned (not as easy as an AFB, or Holley)... I used to have a PDF that explained performance tuning of a Quadrajet in detail... I'll hunt it up and if I can find it I'll post it.
One thing I do wonder is that even if the carb manifold and EFI manifold are neck and neck, is the performance gain worth the extra $900-1k?

The people who don't like Quadrajets are the ones that don't understand them.They are tuned in an entirely different way than a Holley or Edelbrock or Demon. Once they are tuned right and happy with what engine they are sittign on top of they will outperform a same class Holley in performance and ecomomy.
Here are some of the guides I used, I'm still looking for the one that actually made modifications to the carb (drilling) for maximum performance... I know I had it downloaded at one time for my '70 Camaro/454 project...

Hope this helps... Be a LOT cheaper than EFI...

And a whole lot of links about nothing but Q-Jet tuning (about half of the links are dead):
Here are some pictures of an EFI manifold which was originally from a 1978 425. It was last on my 500 which lived under the hood of a 1982 Trans Am.

Dunno where the runners would be restrictive. Maybe I need new glasses.


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Even if the EFI and carb manifold are identical (that manifold looks pretty similar to me) you will have an advantage to the EFI because there is only air flowing through those twisted runners so you do not have to worry about fuel fallout. Plus, you can fit a huge throttlebody that will flow more air than a Q-jet without hurting your street manners. Getting over 800cfm through a carb without resorting to huge bores that kill response gets tough, although a carefully ported Q-jet can get up in the 900+cfm area. .
How much do you use the car, especially in cold weather? I would go for EFI hands down but for the $$$ issue. A well-tuned Q-jet car is darn close to EFI in terms of driveability and response, so rest assured you will not me giving up very much if you go that route.
I don't see much wrong with the EFI manifold from the pictures except for the fact that it is flatter.

BluEyes, this is a question I asked myself. Even if the EFI manifold was identical and EFI would be better than carbureation, would it be worth the money?

The car is going to be a daily driver, but not used on short trips where the moped can be due to gas prices. (What can I say, I'm broke)

It seems to me that the Q-jet is darn close to the EFI, with the EFI still being better. But is it worth the money. Even after I get decent figures from the EFI manifold, is it still worth the money?

Would you say that the Q-jet will be plenty for my engine right now? I am going to be working with JET on this one who builds a Q-jet specifically for your engine.

Anyways guys, this is what the vote is for. There are just too many factors.

Will this well tuned Q-jet have good power throughout the entire band like the EFI?

This shouldn't be as complicated...:(
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Personally, I would prefer all my vehicles to be EFI. Reliability, cold weather starting, accurate A/F ratio throughout the rpm range, mpg...

But is it worth the cost to retrofit? Not in my eyes, unless you are going to build the Megasquirt system over time.

My vote would go for Q-Jet... Unless money isn't an issue, then EFI hands down.
Well money is an issue. It doesn't get cold here really either. Almost never snows, just ices. Not like I would be driving in those conditions, so there you go.

The RPM range power was what I was seeing through the EFI. That and the crazy easy tuning and effieciency. But for over a grand more, I'm kind of just not seeing it. It's still a hard decision to make, but I am only 16. I'm not made of money and the rest of the engine needs tending to as well.
Megasquirt is fairly affordable, just would be very time consuming.

Im doing megasquirt for my cadillac. Most likley, im pulling its 425 and getting a built 500" bottom end (or possibly a stroked one).

With fuel injecton, there is no funny buisness involved once its set up.

Also, dont forget. Carburetors must have some kind of restriction in the airflow, in order to atomize the fuel.

Im tired of playing games with carburetors. Im done. @#() em.

Dont expect fuel injection to improve your gas milage a whole bunch on these cadillacs. If you want good milage, drop in a cummins diesel with 600Ft-Lbs of torque.

If you have the time, and the money, and the need. EFI.
Broke, just need to drive around town... Quadrajet.
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I would go with a carburator... I enjoy them alot more, much more simple and you don't need nearly the stuff as you do for EFI.

The best carburator to use on an, even wild 500.... is the origanal Qudra-Jet that came on them.... say what you want about it, I love it, and it is a great carburator.

fuel mileage.... you would be surprised how good a well-tuned carburator will do on gas.... dare I say I have seen some carb engines get better gas mileage then FI? (similar engines)

Keep in mind, what really killed the carburator on passenger cars.... was emmissions... carburators need an over rich fuel mixture when cold, until they warm up, FI does not, so in the 80's with tighter and tighter emmissions testing and such, the only way to go (for that route) was FI..... *not* driveability or mileage.... which, as was said... once the engine is warmed up (a whopping 5mins) and with a well tuned carb, you shoudln't be able to tell the difference in driving, and gas mileage should be quite similar... now tell me.... do you care about emmissions? (hell its a Big Block Cadillac) much les cold-start emmissions? :)
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Also, weather the FI allows the engine to rev better or not...

none of the BB Cad's are revvers... they are tuggers, you will not see the tach dancing up and down, it is more like it goes to a certain RPM (torque peak) and S.L.O.W.L.Y climbs.... and that is anything besides dead on WOT, where the secondaires are opened... which is also why when you build up a hi-po Cad engine and put it in a Caddy, the highest gear you really want to use is a 3.08, unlike Chevy guys where 3.11 is economey gear and 4.11 is considered normal.... these engines don't like to rev, and don't need to, so as far as I am concered, more responsive, and high revving is not an issue... my stock 425 redlines around 4,200RPM... the most you'll easily get out of a built 500, without starting to speed mega bucks is 5,000 or 5,500RPM.... 4.3" is a long stroke to be pushing any faster.
Night Wolf, dont' worry, I share your views with the Quadrajet. I was planning on using it. People that hate it are the ones that have experienced a 30 year old one with no rebuild, etc etc. Also, people don't understand them. They are tuned in a much different way than a Holley, etc. However, when tuned right, they are economical beasts. Simply put.

Emissions. There will be absolutly no emissions control equipment. No PCV valve, gas fume canister, exhaust port going to manifold, cat converter, etc etc. No emissions testing here. This is good.

Also, I know they are low revers. We are thinking the most this thing is going to come to is 5200 or so RPM. That's where Potters rockers come in handy.

Either way, I see that we see eye to eye on a lot of things. It makes me feel good that I've got my facts straight and the build headed down the right path.
No matter how much you like your QJet, MPFI will outperform it in every way: power, throttle response, performance through the entire RPM range, fuel efficency, & emissions. That is not the question. The only question is if it's worth the cost or not. Seeing how a megasquirt isn't very expensive at all, and the rest of the components from a OEM MPFI system aren't too bad either I'd think FI is worth it. Hell, never worrying about jets and metering rods again alone almost makes it worth it.
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