Rochester MFI unit.

[pdq67]

Has anybody ever converted the old Rochester MFI unit over to EFI?

0306VET_RochesterTWO01_z

If so, how did it work?

http://www.superchevy.com/how-to/engine ... -corvette/

pdq67

[peejay]

I believe Bosch bought the rights to it and worked all the bugs out and named it K-Jetronic, the later versions of which used electronic control of the fuel distributor in addition to the air door/spill plate.

Despite all of the very high precision, tight tolerance internals, it was sold as the "Cheap" fuel injection... Expensive was the L-Jetronic electronic injection. But the K-jet was also used in some higher end cars like turbo Audis and practically all 1980s Mercedes. Porsche used it right up until 1994 on the turbo aircooleds!

K-jet was like a Quadrajet. When it worked it worked extremely well. When it didn't work it was horrid.

[pdq67]

Thanks peejay for the info on what happened to it.

I really like the old Weiand BBM 3x2 elevated cross-flow intake with it's long runners, (part number 7252), because I figure if it is tuned properly, it should make some nice midrange torque.

I am having trouble pulling a picture of it up, but I have posted before about it.

It's made like an "X" with the 3x2's in the middle of the top of the runners.

Weiand only made this one so there aren't any others for different engines. A SBC one should be a dandy, imho...

pdq67

[HDBD]

I can't understand why anybody would cut up such a poor design that has so much value to collectors. Back in the day guys ran dual air meters and they still weren't that great not that the heads were any champs either. Want Cool looking EFI use Hilborn

[strokersix]

The article says they salvaged scrap parts.

[pdq67]

Thanks peejay for the info on what happened to it.

I really like the old Weiand BBM 3x2 elevated cross-flow intake with it's long runners, (part number 7252), because I figure if it is tuned properly, it should make some nice midrange torque.

I am having trouble pulling a picture of it up, but I have posted before about it.

It's made like an "X" with the 3x2's in the middle of the top of the runners.

Weiand only made this one so there aren't any others for different engines. A SBC one should be a dandy, imho...

pdq67

Try this link, it's the one at the top left if it pulls up?

https://www.bing.com/images/search?q=we ... &FORM=IGRE

pdq67

[mk e]

Despite all of the very high precision, tight tolerance internals, it was sold as the "Cheap" fuel injection... Expensive was the L-Jetronic electronic injection. But the K-jet was also used in some higher end cars like turbo Audis and practically all 1980s Mercedes. Porsche used it right up until 1994 on the turbo aircooleds!

All the ferraris got it too...like 1980-1990 or there about. I've converted 1/2 dozen of the intakes to efi so most all the mechanical stuff goes away but there is a company that keeps it all looking pretty stock using an ecu to control the mechanical system.

[kirkwoodken]

The Rochester F.I. hides its complexity with of simplicity. Think of the Rochester system as a Hilborn with an adjustable pill operated by a pitot tube, because that's what it is. They will give excellent fuel curves which follow torque curves and will adjust for different air density's and temps. Everyone with a flow bench understands how accurate pitot tubes are, but most Rochester haters don't realize the unit uses pitot type measurement systems to adjust fuel flow to match air flow.
Years back, a friend of mine told me they didn't put any extra parts on Rochester F.I.'s. The first thing the typical Corvette owner did to his F.I. was replace the air filter with a larger one, because he KNEW the original was too small. The air cleaner housing was HALF of the fuel metering system. Intake impact air pressure was measured by the large tube the air filter sat on. There was a tube that ran from the air cleaner housing to the underside of the main control diaphragm. That was 1/2 of the pitot tube! The other half of the "tube" was a venturi looking affair with an intake butterfly underneath. It measured the "Wall pressure" part of the pitot tube. The Chief designer of the Rochester was John Dolza, who designed F.I. units for WW II aircraft. If they were good enough for aircraft, they were good enough for everyday drivers, for aircrafts go through many varied temps and densities as they fly.
I was told by a Rochester engineer years ago that the Rochester Division cut the price to Chevrolet Division in an effort to have Chevy push the units as gas mileage improvers, which the units did do, but Chevrolet (Corvette) division raised the price to the consumer to make greater profits. The engineer I talked to said mass production the the FI could have been done for about $50.00 back in the day. And the basic system could have been used on any/all vehicles if the company had decided to do so.
In their day, the real problem with the Rochester FI was poor ignition systems, bad spark plug placement, uneducated mechanics, and desire to make too much money. The rich and lean stops on the Rochester consisted of 10-32 Allen screws. 1/6th of a turn of the adjustment from ideal setting would cause a drop in power. The unknowing "experts" would give the screws a couple turns, and the good factory adjustment would be lost forever.

I have an original dual air meter Bill Thomas unit on my 406 SBC and it works quite well. The original FI fuel pump pumps enough gas for 900 HP. If I were independently wealthy, I'd install a couple nitrous spray bars on the intakes and solenoids on the rich stop, and show how much power a NA 1963 Corvette with FI could have made. (Bob Steigemeier tried to talk me into it when we set the rich and lean stops on his chassis dyno.) And I'd take Paul for a ride.

[HDBD]

I am very familiar with the units, at one time I restored the castings including welding on the diecast and I reproduced the PITA cranking signal valves. They were OK after the first few years.

[kirkwoodken]

I have replaced the cranking signal valves with the equivalent to the 1973 transmission spark control solenoid. Those can be bought from various surplus supply houses for less than $5.00. Ebay prices for original solenoids are over $100.00. Total rip offs. Solenoids are triggered by starter and vent manifold vacuum into control diaphragm circuit. Circuit needs cutout switch in case of flooding, just like the later models had. Also, putting an extra 100 cubic inches under the FI's make them start and run better. I run a 255/263@.050" SR on 109 LDA, giving about 10" vacuum at 1200 RPM. I try to limit manifold vacuum to 10" or above for good street driving performance. Just my opinion.

[Dave Koehler]

Good info Kirk. I always wanted to play with one of those. Unfortunately, they are now "gold".

Here is a what if. Since oem filters likely no longer exist does a modern aftermarket replacement filter cause any grief with that pitot system?

[kirkwoodken]

Dave, the setting for accurate measurement of impact air has a formula, but I do not have it handy. If you have an original air cleaner holder you can copy that. It is approximately 3/4 of the length of the radius with the short measurement closest to the OD of the tube. I'll bet someone on this site knows for sure. Most important is that the main control diaphragm is getting its signal from both impact and wall pressures. Signal from wall pressure is expressed as vacuum and is as low as 1/2 inch of vacuum. You can see from this small amount of vacuum that the operating system is very sensitive and is balanced so only fuel pressure on the spill plunger and opposing pressure/vacuum on the control diaphragm meters the fuel to the nozzles.

A good book explaining the FI's and other factory inductions is here: see 1958 new product information manual.

https://www.google.com/search?q=1958+ro ... t1jjmLveQM:

I started out with this manual when in high school. There were changes made in subsequent years, but the basics are explained in this book intended for GM mechanics of that era. Hope I make some converts. Keep in mind the later units were simplified with better startup and idling circuits.

PS: I'll try to come up with better real numbers for air filter. The mistake made with the filters was they should have been lengthened instead of increasing the diameter. That way air volume would have been increased without disturbing measurement system. Even Smokey didn't understand that part. With the first unit I put on my car, every time I closed the hood, the engine quit. Learning curve started then.