Why convert EFI to Carbs!?

[LJ851]

the best thing for throttle response is nothing at all. ;)

The best thing for throttle response is light rotating/reciprocating mass and a single throttle plate per cylinder close to the valve.

[gstuning]

Stock engine, never said stock metering.

The AFM is not to blame. The M20 intake manifold and throttle body size are however.

[u3b3rg33k]

You could always make some horns for the M20 the same length as the OE runners (depending on where you like the torque), but then it's not stock anymore.

[Norbert]

Question: i am planning on putting Dellorto carburators in my m20b20. I have completely refurbished TOP in it which was flowed and has custom crafted Camshaft with 284 degree angle. New everything. Block of the engine was inspected and it is as well in very very nice condition (will be worked on next year).

Now what list of things i need to buy to set up carburetors myself? I am more concerned about what connections i have to buy and where to buy (or they have to be welded in fact?) to connect the carbs and what is required to attach a throttle line to the carbs?

I know i need a fuel pressure regulator as well or correct me if i am wrong.

Any kind of quality resource of information on how to do it is very welcome. So far all i found on the internet was just technical information to how carbs work and so on and so forth but i had trouble finding a decent how to guide or info of any sort.

Thanks in advance :)

[LJ851]

Question: i am planning on putting Dellorto carburators in my m20b20. I have completely refurbished TOP in it which was flowed and has custom crafted Camshaft with 284 degree angle. New everything. Block of the engine was inspected and it is as well in very very nice condition (will be worked on next year).

Now what list of things i need to buy to set up carburetors myself? I am more concerned about what connections i have to buy and where to buy (or they have to be welded in fact?) to connect the carbs and what is required to attach a throttle line to the carbs?

I know i need a fuel pressure regulator as well or correct me if i am wrong.

Any kind of quality resource of information on how to do it is very welcome. So far all i found on the internet was just technical information to how carbs work and so on and so forth but i had trouble finding a decent how to guide or info of any sort.

Thanks in advance :)

It sounds like you are not very familiar with carburetors. Regarding tuning, invest in a wideband 02 sensor/gauge to read your air/fuel ratios. This will help you immensely.

You will need a low pressure regulator and probably need to build custom linkage parts to actuate the carbs. Dellorto is a lot less common here in the US compared to weber.

[BlackbirdM3]

There is a guy on the Datsun roadster forum who autoXs his 2l car in CSP with SCCA. Since he is allowed to run any fuel metering system out there he did a mega-squirt ITB setup to replace his Mikuni 44pHHs. After 10 hours of dyno time trying to get the ITB system to work, it still made less power than the Mikuni setup that the car came with. The A/F ratios were correct, the spark timing was correct, but it was still down 15 hp across the board from the Mikunis. He even tried swapping the Mikunis back on on the same day and retesting. They still made more power. He got so pissed off that he pulled the motor and swapped a modern one in, then took a competitive car in CSP and made it a back marker in OSP. Some motors just don't like EFI.

My carbs aren't really affected by the weather, but they really make nice power when its crazy cold out. No dead spots, easy to drive all the time, everytime. The things just work beautifully.

Will

[Norbert]

It sounds like you are not very familiar with carburetors. Regarding tuning, invest in a wideband 02 sensor/gauge to read your air/fuel ratios. This will help you immensely.

You will need a low pressure regulator and probably need to build custom linkage parts to actuate the carbs. Dellorto is a lot less common here in the US compared to weber.

You are right i am not, but i have a person who is a Bruce Lee in carburator world. The problem is i can't catch up with him as due to that very reason he is extremely busy, but if i only could connect it myself i would just ask him to adjust them.

As i said i know the difference betwwen FI and Carbs but i like the oldschool stuff and carburettors do make insane sound as most of you know. I am anti "electronic" guy. The simpler the car the better.

Coming back to original question, aren't there any allready bolt-on kits available for m20 engines? Or perhaps somebody knows somebody who can make connections which i could pay for?

[Smelser]

I like my Ljet!!

Weld the distributor to get rid of any variable advance,
Pump up the fuel pressure to deliver more fuel
cold air box to suck up the coldest dense air it can

put foot on throttle and make car go left by turning right!

plus have a built in rev limiter so my 30 yr old rods dont fly out the bottom of the engine!

[SkiFree]

The problem with current off-the-shelf M20 ITB manifolds is that they sit the carbs sit up at 20degrees or so. Side-draft carbs in general don't like more than 5degrees tilt. There are ways to monkey with the float bowel, but 20 degrees is a lot to overcome (especially if you want a full street-strong powerband).

I am making a manifold that would sit the carbs nearly flat (just up a couple degrees), but honestly don't plan on anytime within the next couple months.

[Norbert]

The problem with current off-the-shelf M20 ITB manifolds is that they sit the carbs sit up at 20degrees or so. Side-draft carbs in general don't like more than 5degrees tilt. There are ways to monkey with the float bowel, but 20 degrees is a lot to overcome (especially if you want a full street-strong powerband).

I am making a manifold that would sit the carbs nearly flat (just up a couple degrees), but honestly don't plan on anytime within the next couple months.

Thanks for the tips. Didn't think that tru :)

[totheredline]

I'm gonna be the guy to revive this thread. I have some questions and I'm hoping somebody can help me out.

So I have a substantially modified m30b34. B35 pistons, headers, ported, polished, 1mm oversized valves on intake and exhaust, hbeams, retainers, springs, locks, HD rockers, blueprinted balanced..... Yeah you get the gist. RACECAR BRO


Anyway. I was going to run MS1 v2.2 with a old L jet dizzy controlling spark. But I'm in a little bit of a time crunch. I'm joining the navy as a rescue swimmer AIRR and I'll probably be leaving mid November. In order to get the car running so I can have fun with it this summer I'm really seriously considering carbing my car. Has anyone ever used twin 2bbl Bavaria manifolds on an m30 swapped e30? Will they clear the brake booster? How about the 4bbl intake? (This is the one I really would like to use. So I don't have to sync carbs. And I can tune a 4bbl holley) one I really want to Any clearance issues there? I highly doubt ANYONE has done this but I thought I'd give it a shot.

[BlackbirdM3]

I'm gonna be the guy to revive this thread. I have some questions and I'm hoping somebody can help me out.

So I have a substantially modified m30b34. B35 pistons, headers, ported, polished, 1mm oversized valves on intake and exhaust, hbeams, retainers, springs, locks, HD rockers, blueprinted balanced..... Yeah you get the gist. RACECAR BRO


Anyway. I was going to run MS1 v2.2 with a old L jet dizzy controlling spark. But I'm in a little bit of a time crunch. I'm joining the navy as a rescue swimmer AIRR and I'll probably be leaving mid November. In order to get the car running so I can have fun with it this summer I'm really seriously considering carbing my car. Has anyone ever used twin 2bbl Bavaria manifolds on an m30 swapped e30? Will they clear the brake booster? How about the 4bbl intake? (This is the one I really would like to use. So I don't have to sync carbs. And I can tune a 4bbl holley) one I really want to Any clearance issues there? I highly doubt ANYONE has done this but I thought I'd give it a shot.

The issue with running downdraft 4 barrels is that air doesn't like to make 90 degree turns. A straight six is a sidedraft head and so in order to run a downdraft carb, that air is going to have to make a 90 degree turn right after the carb. Not a good way to go as the air velocity will drop to nothing, the fuel will de-atomize and turn to droplets because of the turn. Sure, it might run but it will be unhappy. You will still have to sync them anyway. Down draft carbs work best on V6,8s, and 12s, or flat engines (Porsche, Ferrari) because they don't require the air to make a 90 degree turn, and can more or less go straight into the intake port.

You want a set of sidedrafts.

Will

[LJ851]

The issue with running downdraft 4 barrels is that air doesn't like to make 90 degree turns. A straight six is a sidedraft head and so in order to run a downdraft carb, that air is going to have to make a 90 degree turn right after the carb. Not a good way to go as the air velocity will drop to nothing, the fuel will de-atomize and turn to droplets because of the turn. Sure, it might run but it will be unhappy. You will still have to sync them anyway. Down draft carbs work best on V6,8s, and 12s, or flat engines (Porsche, Ferrari) because they don't require the air to make a 90 degree turn, and can more or less go straight into the intake port.

You want a set of sidedrafts.

Will

Have you ever driven a Bavaria? I wouldn't call that an "unhappy" engine. Not saying it's better than a sidedraft, but it certainly works just fine. So do 2002s.

[totheredline]

Sidedrafts are out of the question unfortunately. I'd most definitely have to modify the brake booster and I really don't have the time for that. Also... Im a 19 year old kid and I've exhausted my funds on this car. I don't have the knowhow to mess with side drafts either. Once I get done with training I'll probably convert to a nice efi setup with ITBs ect. Right now I just want the car to run. I can sell my efi stuff and probably turn a profit. Buy some used delltoros, munikis or Webber's and rebuild them. I realize its not going to make as much power with a 4bbl or twin 2bbl. Just by looking at the intakes you can tell they are far from optimal. The intake charges wouldnt be even as the runners are different lengths. I CAN afford a 500-600 cfm speadbore 4bbl and get it running well in a couple hours.

[graveshaker]

Side draft Webers are great, here's my built VW Rabbit GTI 13.1 compression 180hp dune buggy. The sound and throttle response like many mentioned is pure awesomeness.