Does anyone have pictures, or, is anyone interested in seeing pictures of dual air meter FI units???
I'm having photos put onto a disc at Walmart (when my wife returns from her shopping pilgramage). If there is any interest, I'll post some.
OK, here they are.
The first 8 pictures are of the dual air meter that is installed on the FIRST SRII (originally built for Jerry Earl). I'm sure several of you are familiar with this car.
If I could EVER find a complete 62 Air meter, I WOULD modify the unit on my 56 like the below!!!!!!
If you look close, you can tell that almost the whole side of an early finned top plenum was cut out and what appears to be a 1/2in alum plate welded in place with holes cut for the 2 air meters. Actually, this is quite an ingenious modification and as I understand, it works great!
The next 3 pictures are of a 64-65 type FI that John Eyestone had advertised for sale a number of years ago. I took these pictures at the NCRS Nationals at Grand Lake in '93. As you can see from the decal on one of the pictures, this must have been on one of the GULF Oil Corvette racers at one time.
A unit like, or similar to this was also used on some of the Bill Thomas Chetahs.
From what FI knowledge I have gained over the years, the primary limiting factor to the early FI units (57-65) was air intake. Adding a second air meter, theoretically, would double air flow (of course assuming the plenum could also flow the added air). I have a HEALTHY SB400 in my 56, and it is a rocket from 2000-5300rpm. By about 5500, it is falling off and at 6000 it is straining for air. There is no question in my mind that my 400/FI could benefit from a second air meter. Although, it I don't really need that much more air, because I seldom push it beyond 5000. The car has a 3.08 rear and the 406 cubic inches will easily turn a 3.08 gear, even uphill out of the hole. So, from stop to 5000 and then a hard power shift to 2nd, and its gone! (but it would be nice to go up to 6500 more easily)
The person that owns the early unit told me that the fuel meter had to have some special modification done to it (in the area of the main fuel valve). Also, I have a drawing given to me by John Eyestone years ago that shows the necessary modification to be done to the two types of fuel valves for use with a dual air meter FI unit.
The person who owns the early unit that's on the SRII told me who did the fuel meter cation on his unit (forget his name). I called him about the mod to the fuel meter and he confirmed that he knew what to do-----------------but he would NOT give me ANY information about exactly what had to be done. From the drawing that John Eyestone gave me, I believe I could figure out what and how to do the mod. BUUUUUUUUUUUT, I don't have a second 62 air meter to add to my unit, so, at this time, it really doesn't matter!
As far as driveability goes, well, I don't know because I don't have any personal experience behind a dual air meter equiped car. But if set up properly, it should be just as smooth as a normal FI unit.
I mentioned earlier that if a plenum could handle the added air flow from a second air meter, there should be a noticeable increase in power output.
My plenum is already hogged out for added air flow. I have one of the early finned top plenums that was cut in half by Bill Thomas (maybe in conjunction with Hayden Proffit????), right down the middle between the center fins, severely hogged out, then welded back together. Because so much material was removed from the inside of the plenum, a 283 would probably loose some bottom end torque. But, on my 400, the added displacement seems to adequately overcome any loss.
As I understand, the 57-61 air meters flowed around 550cfm and the 327 (62-65) air meters flowed a bit more, about 600cfm. My FI unit has a 62 air meter on it, thus, theoretically, if a second 62 air meter were added, then that would be about 1200cfm!!!! So, how much engine could 1200cfm support?
Tom, good luck with your search for another air meter. Would you like me to ask around for you out here?
I've been looking for a 62 FI unit, but haven't had much luck. From looking at them, they look like they'd give a little more mid range and top end than the low rise factory carb set-ups.
Given the cost of the Rochester units, I started looking at the alternatives. There are guys in the C4 section converting later LT1 fuel injections to work with the earlier TPI bases, which fit the early heads and allow a distributor to be used. The LT1 runners are similar to the early Rochester units, and have a good reputation for making power in the mid and upper RPM ranges.
I suspect you could use a tach drive distributor, if it was converted to run a later TPI module (similar to a Dave Ray small cap HEI conversion).
Anyways, before I stray too far off topic, I'd be interested in hearing from someone (with experience) how a dual air meter set-up performs on the street.
i have seen, but don't have pictures of, a 63 - 65 unit with 3 air meters; the 2 on top and the 3rd one in it's original postion. and i've seen, (again no pictures) an early style with 2 air meters 'stacked' in the original position (effectively giving a longer air passage length).
This duel air meter set up was used on the Grand Sport driven by Dick Thompson for the Yenko/Gulf Oil Corvette racing team in 1963.
Gulf went with Ford in 1964.
This engine was part of the Yenko estate sale.
Has alum heads and billet machined alum. prototype parts
Also has a gear driven fuel pump set up on the dist.
I read in the Yenko note books that one of the problems they had with racing the stock FI was breaking the cable drive
Gulf Research Lab did extensive development and testing on Corvette FI. I saw some of the Gulf engineering notebooks that showed ink splatter testing results. They had books full of cards with ink splatter samples that they must have used to analyze the FI system.
I have have some of Yenko's note books that show the dyno test results from 1961 where they had recieved special FI system from Chevy that made 24hp more then the stock FI system. In the notes they mention somthing was a "one piece design" vs (I guess) a stock two piece design?
looks to me that one of the air meters are either turned up side down or has had machineing to remove some bosses.
There is a fellow in South bend Indiana that has been doing fuel injection for years,,and has parts for sale. His name is Jack Podell.He used to advertise in hemming alot,maybe still does.I think he has an email addy,email@example.com.......not sure.
Tom, I'd be interested in the fuel valve modifications if you would care to send me the info. I too have been playing with FIs for many years and am currently running 62 FI on HP 355 motor. I have long thought about building a dual air meter unit for mine as well.