Carter or Rochester?

[gregcarter]

Hi there!!

I bought 2 quadrajet cores on the internet to build one or both for my '76 chevy pickup driver.

The numbers were  almost identical, the Rochester is 7045213 YA and 1605 stamped under.

The Carter is 7045213 with CG  YA stamped under. 52009 is stamped on the throttle plate.

This number shows up in my factory manual for Federal use in 1975  or 1976, I don't remember which.

I thought I would use the Carter because it had a 1/4 hose fitting for EFE next to the driver idle screw, which the Rochester doesn't.

The measurements on the Carter are:

idle tube        .037

idle channel   .075

upper idle air bleed (main body) .085

upper idle air bleed (horn)    .046

main air bleed  .046
 
main air bleed (horn)  .042


main jet 64C

primary metering rod  .044/.026

The bypass air is plugged on both sides

MY rebuild kit came today. 76 mains and 44B rods were provided with an APT screw as well.


I need to know if the idle down tubes are too big, and I'm pretty sure .032  is big enough for the idle tubes.

Please let me know if I should redrill the bypass holes, if I should change the down tubes, and reduce the idle tubes.

I forgot to mention, the engine has an RV cam and Edlebrock manifold with EGR.

Thanks,
Greg Carter

[gregcarter]

I made an obvious error in the previous post, there is no upper idle air bleed in the horn.

The main jet was probably a 72.

The year is obviously 1974.

I can't find my book.

I need to know if I should modify the idle system on the Carter 7045213 as the Rochester 7045213 and my Edlebrock  1902 have .052 idle down restrictors, .032 idle tubes   (.037 on Rochester) and bypass air.
Thanks
G. Carter

[Cliff Ruggles]

Looking at the MAB sizes and blocked bypass air in the main casting the carb has been commercially remanufactured at some point.

The 76/44 combo is for the original .118" MAB's.

I'd need to know all the engine specs to set up the idle system.

CID, compression ratio, camshaft, etc......Cliff

[gregcarter]

Hi Cliff,

Sorry my phone cut out today, I was on top of a mountain all day at work.

My engine specs are:

cid= 355 cu in.

 cam specs are 1500-4000\t270 280\t204 214\t.420 .443\t107Deg 117Deg\tB ( well, that's what it

says on the card) little rv cam. Plenty of vacuum...

edelbrock manifold with egr (heat sink)

compression ratio = probably 8.5 to 1 (says the machine shop)

The carb specs are corrected as follows:

idle tube        .037

idle channel   .075

upper idle air bleed (main body) .085

main air bleed  .046
 
main air bleed (horn)  .042

main jet 72

primary metering rod  .044

The secondary rods are not numbered but measure .100 tapering to .135.

The secondary air tubes are .075 and .042.

The bypass air is plugged on both sides.

The bypass opening in the throttle body is .095.


So I'll need to purchase the idle parts you recommend and it sounds like the mabs too.



What did I forget?

This carb is for a daily driver that I'm looking for economy. At 12 mpg, I don't really expect much

improvement. Since I'm retiring soon, it won't be driven all the time.

Thanks,
G. Carter

[Cliff Ruggles]

.037" idle tubes are pretty big used with .075" DCR's.  Stock DCR's were around .046" or so in one of those nearly as I can remember.

What is the lower idle airbleeds size, should be pretty small if you have .085" uppers?

[gregcarter]

Hi Cliff,

The lower idle airbleeds are .067.

Also, the idle tubes are larger, I pulled one out and it was .039.

The stock idle set up would be good enough for me, unless you have a better idea.

The Rochester of the same carb number that I bought has .039 idle tubes, .052 DCR's, and .067 lower air bleeds, .092 upper idle air bleeds. I don't know if it is the stock setup.

I await your opinion..

Thanks,
Greg Carter

[gregcarter]

I didn't understand your reply about the 76/44 jet/needle combo you sent me until today.
You said they were specified for the original mabs of .118.
Since my carb has smaller mabs, should I take them out?

Thanks ahead,
Greg Carter

[Cliff Ruggles]

Yes, use the 76/44 with the stock size MAB's.....

[Kenth]

Here is what i