I was givin a Q Jet carb #17057287 and I know that it is for a marine application. I plan on rebuilding this carb. However the primary rods will have to be replaced I think. The numbers or letters in this case are DE and the jets are not easy to read but I think they are marked as 68 or 69. If this makes sense to anyone could you tell me if These are not proper for a 350 bored .060 over with headers alum 2101 Edelbrock and a Speed Pro cam, Oh hell I can't find the tech sheet for the cam. Anyway can anyone get me in the ballpark with the #s I have given so I can be assured that this car will stay running for break in?
I will get the specs for the cam later,I have to run right now.

 

The primary metering rods should have numbers, not letters. My guess it that they probably say 48. You'll need a microscope to actually read the numbers on them. You'll need a jets ranging from 73 to 76 and rods from 43 to 48.

 

The DE rods are for the secondaries.

BigBlockk

Later.....

 

Why would there be secondary rods in the primaries, though...?

 

I've just been working on mine changing the jets. My primary rod is marked 46K and I'm pretty happy with a .073 primary jet. You can get these from Summit made by Edlebrock p/n 1973, .074 would be p/n 1974, etc.

The secondary rods are always two letters, I believe you must be looking at those. Mine are CH. I can't say they are the right ones for my engine, I'm not happy with the performance yet but it might be something else. There are a TON of different secondary rods made

I switched from .074 to .073 primary and it made a noticable difference in performance. These might not be exact for your applicatioin but it'll get you real close.

I have a ZZ4 and 4 speed.

Bill

 

BigBlock is correct. I had misspoke as to which rods I was reading. I have everything soaking in laquer thinner now. when I get everything cleaned,I will post the correct numbers.
Thanks.

 

O.K. After cleaning everything I find that the primary rods are 35 and jets are 69. Secondary rods are marked DE which translates to a0.0877 and they are medium length. any additional input with this new info???
Also I find that there is NO power valve spring and the spring that I assume holds he accelerator pump seal(blue in color) is broken. Should I continue to invest in this carb,or should I look for another??? Remember this is my first rebuild and I feel like I am getting in over my head.

 

I'm not an expert on carbs but here's a little info:

Primary metering rod of 35 means it's a single taper rod .035 dia and since the carb ser no. begins with 170.. it means they are .080 shorter and not interchangable with double taper rods like the number I gave you that ends with a letter, so be careful when changing them if you do. I would leave them for now.

The main jet at .069 sounds too small to me for your engine, I would increase the diameter to around .073.

I'd start with that for jetting and see how it performs one step at a time. Your secondary rods are allot bigger than mine, .0874 at the tip vs mine at .0567. I would think a change might be in order here to but I'd start with the mains first. The secondaries are real easy to change later.

my .02 cents

Oh, and about the broken parts....bring the ser no to NAPA and you can buy a rebuild kit for it with new Acc. pump, gaskets etc. It's pretty easy to do.

Bill

 

The carb you have is a 1977..
Be sure to order rods for 1975 and newer
I believe the pre 75 rods are of a different lenght.
EDIT oops......Top Gunn already explained this

READ THIS IS YOU PLAN ORDERING RODS FROM RDELBROCK

I ordered a set of primary metering rods from Edelbrock for a Quadrajet Im rebuilding
I wanted 0.42 rods so I ordered part #1942 which I thought would be a .042 rod....turns out that they are .041
This has to be the MOST SCREWED UP NUMBERING SYSTEM I have ever seen.... take a look..... Which is what I SHOULD HAVE DONE before I ordered them...on the bright side, their main Jet numbers do coincide with the actual size.

I now realize they dont produce a .042 primary rod but I cant believe the way they number their rods
______________________________________

Primary Metering Rods (Pairs)

Single Taper for Q-Jet Model 4MV (1974 & earlier). Dimension indicates maximum diameter of taper.

* (.035") ....#1936*
* (.037") ....#1937*
* (.039") ....#1939*
* (.041") ....#1942*
* (.043") ....#1944*
* (.045") ....#1946*

Primary Metering Rods (pairs)

Single Taper for Q-Jet Model M4M (1975 & later) and Edelbrock ....#1910. Dimension=maximum dia. of taper.

* (.048") ....#1941*
* (.050") ....#1943*
* (.052") ....#1945*
* (.054") ....#1947*
__________________________________

 

No rubber or plastic parts I hope

 

No rubber or plastic,and thank you Bob for sharing your experience.

 

I figured he was mistaken about the rods so I wanted to make sure he knew that "DE" was a secondary rod designation.

As for this carburetor, it has a "truck" calibration. It will be about right on at idle, richer at cruise and lean at WOT. It was calibrated for a heavy vehicle operating mostly at part throttle.

For your application it will do best with a 72 to 75 main jet, something around a 45 main rod and a secondary rod that is somewhere in the middle between rich and lean like a DA. The DE rod is VERY lean.

BigBlockk

Later.....

 

69 jet with a 35 rod? Holy crap that's RICH. That's a 288 metering area. a 45 with a 73 jet would be 163. Being that this is an M4M, rods are a pain in the butt to get in the right size. IF you can find a 57 jet you could use your same rods and have the same metering area. However, I don't think you can find a jet that small so you'll have to find some primary metering rods between 40 and 50 in the k or p spec. Maybe olescarb can help on that.

You can get a power piston spring at www.carburetion.com

 

Thanks guys.

 

His engine would probably melt at WOT with a 57 main jet. Check that, it probably wouldn't even run long enough to get to the secondaries.

At WOT below 3500 RPM the mains are providing almost all of the mixture for the engine. The mixture at WOT, before the secondaries open, is dictated by the main jets and only the main jets. All of the usable main metering rods have the same power tip size (.026"). At WOT the metering rods are as far out of the jets as their going to get so you are running on the main jets only.

This engine would lean out so badly that it probably wouldn't be able to pull the vehicles weight long enough to get the secondaries open at around 2800 RPM. I would think there would be massive carburetor backfiring.

Besides, I believe the smallest main jet for the Q-Jet is a 60.

Edelbrock makes a race tuning kit for the '75 and later carburetors that could help with this. It is #1992.

http://www.jegs.com/webapp/wcs/store...tegoryId=10285

BigBlockk

Later.....

 

Forgot about the tip vs. jet size... That edelbrock kit won't help much, though. All of the rods are M rods which have an .032 tip size, not the .026 that we want.

 

Hey Kal, how do you calculate this and more important what does "metering area" mean? and how do you apply this info when deciding what jets/rods to use?

Thanks
Bob

 

Holley, Think Holley.

 

Go to corvettefaq.com -> engine -> intake -> lars jet tuning chart