Technical Rochester Ramjet Fuel Injection

Ok Guys and Girls, for some reason today I was thinking about Fuel Injected Chevrolet’s. I know almost nothing about the system other than it was offered on 283 and 327 Small Block Chevrolet’s. Can anyone explain how it works? Has anyone worked on an engine with it? Does it really run better/stronger that a four barrel carburetor ? And lastly, does anyone have any stories about it from “back in the day”? Thanks so much for all of your help, I’ve learned so much from all of you guys!


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Cool looking. Hard to tune. $$$$$ not that good. Go with a fiteck system. Work good looks like a carb easy to install runs great. Done a few no problems

 

My opinion

 

Here's one in the classifieds, spendy and you need to find someone that knows how to tune them. Parts aren't exactly easy to come by and cheap if they are missing.


What about just the unit itself, https://www.jalopyjournal.com/forum/threads/1957-59-fuelie-unit.1128705/

 

Rochester was kind of like Hilborn but the added a throttle valve that used a venture like a carburetor to set up a vacuum signal to control the fuel valve to sense load. Hiborn only knew throttle opening and RPM.. Equal fuel distribution was the big advantage.

 

Except in the Corvette circles, many more were taken off rather than installed over the years'

 

My Hobby Shop landlord has a 62 fuelie that I rebuilt the injection on. Loves it, runs like a top.

 

I have owned a '65 unit since the early '70's and ran it on different cars over the years. The above picture is on my Roadster I completed in 2011. They are not that hard to tune once you understand how they work and use an wideband air fuel ratio meter. I finally gave up on it after having idling problems while sitting in traffic. The new gas is so thin and with the ethanol the small lines going to the injectors would vapor lock. If you go the websites of the people who rebuild them they all tell you they won't work correctly with the ethanol gas. The unit never stranded me on the road and I put many miles on it. I bought the complete 375 HP motor with the FI unit out of a totaled '65 Corvette for $250, even got the air cleaner which I sold for $125 thinking I did good!!

 

I have had a few, still have 2 63 units. I think fuel injection is like electricity magic if you understand it hell if you don’t. I still have my manometer ,the unit is adjusted in inch’s of water. Had one on one of my convertibles with a new LT -1 in the early 70’s. It really hauled. I haven’t ran one for at least 30 years, The only things I would be concerned with now is rubber seal compatibility, and nozzle size , alcohol requirements would need larger nozzles and maybe lines or an increase in pressure for volume. I stay away from the ethanol stuff. Not sure what you have to deal with in Illinois. If I wanted to run one now,I would they were really great , just keep a spare drive cable in the glove box.

 

Ran one on my 57 Fuely for 38 years. Sold the car a couple of years ago. Never had any major issues. Rebuilt it a few times and a few for other guys as well. Did a 40 that had a 65 unit on it--still running great. Always carried an extra drive cable-never broke one. We drove that car everywhere. Wife ran it at the drags as well a few times. It did not like the new ethanol gas as stated above.

 

Ran a '62 Fuely for 13 years, rebuilt it a few times, street raced it a few times. I was smart enough back in the '70's to buy all the rebuild kits and consumables I could find for future use. Was happy with everything about it. Got a hair up my ass one day and installed a Victor Jr. and a 750 Holley double pumper on the 366 and found some hidden power. I think the FI was as good as any 4 barrel & manifold sold at the time but later manifolds & carbs would out perform the FI. JMO!

 

I'll bet you lost milage when those thing were right they were craze good.

 

Ran a 1960 unit on 4 different 283’s. Last one was a 1965 Chevelle power glide for my wife. 20 mpg in town and 25 on the road. Always carried the cable and starter cranking valve. Loved it... wish I had it. Bought it for $125.. sold it for $750.

 

I love seeing those in non vettes

 

Yeh, its not often you see that and even back before they got rare and expensive you mostly only saw them in street rod type cars, rarely muscle cars.
In the very early 70's there was a guy here that had a Rochester FI on a 66 or 67 Chevelle, he was the go to guy and actually had a wood box with all the factory repair/adjustment tools/gages. The guy had one weird quirk in that he stamped his name on EVERYTHING, his FI was the early (60/61) smooth top plenum and in HUGE letters he stamped his name.

 

Had a college buddy who was a mechanical engineer and an SCCA racer in 1964. He raced Corvettes, both with the fuel injection and with the single 4-barrel. He knew how to tune one. The original equipment 4-barrel car he was racing would easily, and always, beat the fuel injected version. He was racing either 1960 or 1961 283's, so the carburetor was the Carter WCFB, not the later AFB's or the Holleys. Still would whip the fuel injection.

Have no experience with anyone running one of the Chevrolet versions on the street, but for racing, not a good choice unless mandated by the sanctioning body.

Rochester also made two different versions for Pontiac. Have a number of friends who have tried to run these on the street. Next time you see a 1957 Bonneville at auction, listen for the announcer to announce "exceptionally low original mileage". There is a reason.

Jon.

 

I have had this one since 1968....modified 7250 unit on a 327/375 motor........runs like a top, never failed me. Always fires right up. It does not like E-10 fuel though......percolates in the bowl. Most Rochester rebuilders recommend race gas or avgas. I started working on these in 1963.......put a '58 unit on my '55 BelAir. I have the calibration/flow kit and have been doing all the work myself since '63. You need to make sure all the nozzles are perfectly flow-matched. No big mysteries......just need to learn some fundamentals.......a bit more complicated than setting up a big Holley carb. Tuning is quite simple once it's set up properly....there is a lot of literature available to help you do this.

 

I’ve never even touched one but I lurk on the corvette forum. There seems to be a lot more info readily available thanks to the internet. And I believe rebuild parts are be reproduced, I would love to have one for one of my cars but unless I sneak up on one at a garage sale, it ain’t gonna happen.

 

I thought I was hot stuff buying Rochester FI units in Dallas for $100 and selling them in CA for $150....
if only I knew.

 

Found a neat FI repair shop website with many cool photos and tech stuff.
Make sure to click on FI fun facts too.

Here's a couple interesting photos.




http://chevroletfuelinjection.com

 

In 1965, I put a FI off a 57 Belair on my 63 Impala 300 HP 327 with no changes made for tuning and I have no time slips to verify any improvement but my seat of the pants dyno said it was an improvement that was worthwhile! It was a fun ride with the FI and since there was not enough room for the factory air cleaner/silencer I ran a chrome air cleaner that was made for dual 4 barrel setup and that thing would whistle so loud you could hear me coming from 6 blocks away!

 

Thanks for all of the insight and information everyone. I know I can always count on fellow H.A.M.B.ers to teach me and enlighten this Farm Kid. Thanks Guys!


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Rochester Fuel Injection is traditional.

 

Way back before I was legal age to drink beer I had a '57 Chevy wagon. Everytime I broke something I upgraded eventually ending up with a 270HP, 4speed, 5.13 rear. Consistently turned 9.40's at Balboa in the 1/8 mi. A buddy found a Nomad and built up a 283HP motor. One weekend when his motor was down I borrowed the injection, bolted it on and turned 9.20. I thought I was pretty hot stuff, but had to give the injection back. Dave got the Nomad to turn 8.75. Hell, and I was cheating with a 30-30 cam.

 

It's a high dollar setup. Probably always has been except in the early sixties when units were being discarded because of tuning. the 64 65 units are the largest cfm units and the highest technology. They like steady vacuum and big inch sbc's.

They have to run in a high state of tune (difficult without equipment , there is no seat of the pants tuning) and today like race gas only due to percolation and vapor lock. The design was not heat friendly because of a the fuel distribution spider which is copper tubing under the doghouse and sandwiched on top of the intake valley. they hold a tune almost indefinitely if you can keep from fiddling around with your complete setup , all of it, valve lash, timing, fuel to air, etc (that is why they were removed in the first place by dealers and individuals alike - they didn't understand the system and it is an analog engineers dream come true). The fuel economy and throttle response is extremely impressive.

I've had lots of them, and yes they are traditional to me too.

 

Curious why they stopped casting the early style without the cooling fins on the top of the plenum.

 

DDDenny - GM changed the plenum design to make it lower in order to fit under the StingRay hood. The early style will not fit.

 

That makes sense on the 63-67's.
I'm not up on the differences year to year but wasn't it the 60-62 that had no fins on the plenum and did they have a decreased hood clearance compared to the 57/up Corvettes which had the finned plenum.

Found this neat article.

http://www.superchevy.com/how-to/vemp-1303-mechanical-fuel-injection-systems

 

You are correct that the '60-62 had no fins....with some exceptions: the ".....7250" units (only 73 produced) were used on the hi-po '59s through '60. Duntov used these on his race cars. I believe the hood clearance was about the same from '57 through '62, but not sure......I have had a '59, '60 and '61.....none earlier.

The article you sited is a good summary.....there are many in-depth books/articles/papers on these. I also have the original SAE technical paper that GM presented to introduce their design......quite fascinating history.

Here is my first one - a '58 unit on a 283/315 HP motor I built for my '55 BelAir in '63 - That unit cost me a whopping $45 (including the distributor)!! It was one of those thrown in a trash bin at a dealer.......the unit on my '40 coupe (above message) cost me $75 (complete and running) in 1968.......inflation I guess!! They are running north of $8500 for a good rebuilt one these days...