joeyl

Where the 1961 fuel injection units for the 275hp version the same as the 315hp?

Smooth top with the tach drive off of the distributor?

Or did the 275hp fuel injection unit have the finned top with tach drive off of the generator and the smooth top units where for the 315hp version only.

I think there were only 100 or so 1961 275hp fuel injection cars?

Thanks.

mashinter

This is a quote from Tom Parsons:

"Some, and maybe all, HYDRAULIC cam FI engines up through 61 got the finned top plenum."

DZAUTO

I'm not quite as familiar with the 61 units as I would like to be, BUT, here's the breakdown as I know it to be.
1961 FI 283 with HYD cam (275hp):
7017200 FI unit-Ribbed plenum
7017310 FI unit-Smooth plenum

1961 FI 283 with SOLID cam (315hp):
7017250 FI unit-Ribbed plenum
7017320 FI unit-Smooth plenum

Personally, I have NEVER SEEN a 60 or 61 ribbed plenum on a SOLID lifter FI engine. All of them I've ever seen (60-61 with solid cam) had the smooth top.
I HAVE seen a couple of 61 hyd cam FI plenums with a ribbed top. One of them was purchaced by an acuaintence from the original owner. It was a complete running car in virgin condition, but with slight fiberglass damage to the righr rear quarter. It was purchased new and owned by a pharmacist in Colo until sold to my acquaintence who was doing a frame off back in the mid 90s time frame.
So, that's the best info I can give you. This is also verified by NCRS information as well as Noland Adams. Thus, yes, ribbed plenums did exist in 61.

Now, as an added observation on my part. ALL the ribbed top plenums that I've ever seen (when I was rebuilding them) had the smaller runners and the smooth top plenums had the larger runners.

UNFORTUNATELY, this is the ONLY picture I have of the underside of a ribbed top plenum with its smaller runners (yes, this is a modified duel air meter FI unit). You can just barely tell the runners are a little smaller than the lower picture of a smooth top plenum with the larger runners.




Sometimes it never occurs to me to take more pictures for possible future reference.

And, while we're on the subject of 61 FI engines, BOTH the HYD (275hp) and Solid (315hp) cam engines for 61 got the FIRST double hump (461X) heads. This was the ORIGINAL beginning for the term "Fuelie" heads. The term really DID NOT begin with the 57 FI (539) heads, because the 57 539 heads were used on BOTH FI engines as well as the "Power Pac" passenger car 283 engines with 4bl carb.

Tom Parsons

joeyl

Thank you for the reply....

So then for a 1961 FI 283 with HYD cam (275hp) with 7017200 FI unit-Ribbed plenum is the tachometer powered off the generator?

Thanks again,

Joe

DZAUTO

Joe,
With one exception, ALLLLLLLL hyd cam FI engines up through 61 had a generator driven tach. ALLLLL solid cam FI engines up through 65 (end of FI) had a distributor driven tach.
The lone exception to the above was 57. ALLLLLLLLLLLLLL 57 tachs, EXCEPT the 43 column mount tachs were generator driven. The 43 cars in 57 with the column mounted tach had a 908 distributor which was the ONLY tach drive distributor in 57. AND, there MAY be an exception to the exception for 57. The 43 cars with the column tach were also Airbox cars. BUUUUUUUUUUUT, there is an outside possibility that MAYBE a few 1957 NON-Airbox FI cars also got a distributor driven column mount tach. It is possible that a VERY SMALL handful of RPO684 (HD brake, FI) cars got the column mount tach BEFORE the first Airbox was installed by the factory. And then, there is also an exception, to the exception to the exception. It MAY be possible that an even smaller amount of 57 FI cars had the dash mounted tach driven by a 908 distributor. But this is NOT verified.
John Neas has a GENUINE 57 RPO 684 car (with FI) that was built BEFORE the Airbox was installed. The Airbox on his car was shipped, and later installed, AFTER delivery of the car. It has a DASH mounted tach.

Soooooooooo, other than the VERY FEW 1957 cars with a distributor driven tach, ALL Hyd cam FI engines had the generator driven tach and solid cam FI engines had a distributor driven tach. Beginning with 62, there were no longer any hyd cam FI engines and EVERY SINGLE 62-65 car had the tach driven by the distributor (both hyd and solid engines with lo-hp and hi-hp ratings).

Tom Parsons

mashinter

Tom:

Here are pictures of a 7017300 vs. 7017360 plenum and a 3748947 vs. 3768233 bedplate. The gaskets are the same size to help illustrate the difference. (The smaller ports are for a ribbed top plenum and base plate.)

Bill

jimgessner

Tom,
Have you ever seen Paul Eardley's 61 white/ red vin #825 283/275hp fuel car?

Paul restored in the early 90's. From Streator Chevrolet in Salt Lake City when new, it was very well known in the Salt Lake area forever.

Nicely optioned with two tops, radio, positraction, 4 speed, heater, anti freze. Paul sold it in 2002-03 time to another collector also in Salt Lake. I am curious what fuel injection unit the car has. I will ask and get back to you.
Regards,
JIM

DZAUTO

Bill,
EXCELLENT comparrisons-------------------those are better than the pictures that I have.
Is it OK if I save them?

Tom Parsons

mashinter

Sure Tom! I wouldn't have done the study without your insight. I wondered what the difference was between ribbed and smooth...now I know! Thanks!

Bill

CorvettePI

I purchased a '61 Impala about 2 years. It came with a fuel injection unit that was not on the car, but each of the past two owners (three including me) were handed a box of parts and told "this came with the car." I have put the unit in to be identified and rebuilt, and although I have been told that passenger cars did not come with FI post 1959, I am trying to determine if my car was (possibly) a special order. My Impala also has factory A/C, power brakes, steering, power seats and power windows, with AM push button as well as windshield wiper sprayers, every single option you could get. The unit has a finned (ribbed) plenum and has been identified by the person rebuilding the unit, as a 1961 275HP unit. In searching the build stats, it appears there were 110 275HP '61 fuelies made. I am trying to find someone with one if these cars. I'd like to see some pictures. Additionally, according to what I read, the cost was the same for the 315HP and the 275HP. Does anyone have any more information on this.

grumpy10956

please keep me posted

CorvettePI

Grumpy,

Where I live (Los Angeles), there is an informal car show every Sunday. I went this morning because I knew there was a guy with a '61 Fuelie. He claims that his fuelie was the 275 but showed me photos with the flat plenum. He's unfortunately really angry with the world so it was a short conversation. All of my research indicates the original information you forwarded is accurate. The plenum on the 275HP were on the hydraulic lifter 283's with ribbed plenum. There were, according to what I was able to determine, 110 built from the factory, but I can not seem to find any photos. This website

http://www.vettefacts.com/C1/1961.aspx

refers to the 275HP with the code CR as opposed to CS with the 315HP. It also shows
the cost as being the same for either and the production numbers. But still no pictures...

RPO Description Price Production

353 283ci, 275hp Engine (fuel inj.) $484.20 118
354 283ci, 315hp Engine (fuel inj.) $484.20 1,462

CorvettePI

Sorry - 118 built, not 110.

ghoastrider1

[QUOTE=CorvettePI;1591002386]Grumpy,

Where I live (Los Angeles), there is an informal car show every Sunday. I went this morning because I knew there was a guy with a '61 Fuelie. He claims that his fuelie was the 275 but showed me photos with the flat plenum. He's unfortunately really angry with the world so it was a short conversation.]

If his 61 was a factory black car, that was painted/converted to a white car AND had a repair (hand sized) to the pass side . ,behind the rear wheel repair (was turned up on its pass side ) AND had a tow hitch, I can give info on the owner and location in 1966/67.

CorvettePI

His '61 is red with white coves. It is allegedly being restored to 100 points (according to him.) I've never seen the car, just pics. He showed me pics of his fuel injection, but it was the smooth plenum and I don't believe he really knows much of what he is talking about. He said he has the hydraulic lifter 283. Several Chevy historians, including my FI specialist (Tom Ordway) has indicated the opposite. My '61 plenum is dated Jan 1961, consistent with the build date of my Impala.

DZAUTO

Just to add more clarification, I DO NOT maintain that all 61 FI units with hyd cam had the finned top------------------BUT FOR SURE some certainly did.
And certainly for sure, all 60-61 solid cam FI plenums had the smooth top.
MANY, MANY years ago (before most of you were born), when I first started messing with FI cars (back when they were plentiful), it never occurred to me to pay attention, take notes and take pictures of these kinds of details. As a result, so many things have been changed, modified, replaced, swapped and it is often difficult to say for sure just what is/was what. I personally have seen and worked on sooooooooooooo many FI units that have been bubbafied and butchered that it is unbelievable to know just exactly how they started life. The earlier units have been bubbafied the worst because dumazz didn't have a clue how to make them work and didn't understand the consequences of the modifications (or attempted modification) he was performing. GM and Rochester spent gazillions of dollars to make FI a dependable and viable fuel delivery system. For everyday dependability and driving, the very best thing that can be done to an FI unit is to return it to the original condition of that version.
And yes, MULTIPLE modifications to one of my personal FI units have been done, and each one has been thoroughly flogged and tweaked to assure it works-----------------and it does. The ONLY modification (done by Bill Thomas back about 1960-61) which works marginally is the seriously porting of the plenum which reduces low end performance (but I'm running it on a SB400 which enhances the flow through the plenum runners). So for a street/driver/dependable FI car-------------DON'T SCREW WITH THE PLENUM RUNNERS!!!!!!!!!!!!!

desertpilgrim

"And certainly for sure, all 60-61 solid cam FI Plenums had the smooth top.".
Well, you MIGHT NOT want to bet the homestead on that. Engine compartment shots at 1960 Sebring show VINs 2272, 2538 and 3535 all running 7300 finned top units.
VIN 2272 retained its 7300 unit for Le Mans and other races; the Cunningham cars all received different motors for Le Mans that were topped of with modified 7320 units. Those Le Mans motors were removed at Momo's garage and returned to Chevrolet for evaluation and the original motors re-installed before being transferred to Bill Frick.
The 7320 units were delayed at the request of Rochester; they needed to use up excess inventory of older parts before the changeover, hence the 7200, 7250 & 7300 units.

DZAUTO

Good info Loren, I hadn't considered that about the 60 units.

CorvettePI

The 275hp was put on hydraulic lifter engines only. Only 118 were built and sold. The plenum is ribbon on these as opposed to the 315 solid lifter. What's bizarre is the pricing was the same for either. I have a 1 off special order '61 Impala with the 275 fuelie (as well as my '62).

MikeM

Is this the one that also has the CE block?