What size is my carb?

63 F85 Cutlass · January 19th, 2009, 03:49 PM

My 63 F85 with a 215 has a rochester 4 barrel on it, Its not the original one, I'm trying to figure out how big it is so I can decide weather a new one would be benificial, or if rebuilding this one will be fine. I'm not sure if its too big for my motor.

The number on the tag is

7025054

From decoding I know

70= Rochester
25= 1965
0= 49 state monojet
5= Oldsmobile
4= Automatic Tranny

None of it told me size, and the applications I found it listed for were either a 330 or a 400

If anyone posseses this knowledge, it would be grately apretiated. Thanks guys

-Ryan

Wireman134 · January 19th, 2009, 04:34 PM

I have this information from HPBooks "Rochester Carburetors" by Doug Roe @1986

Model 4G: Throttle bore -- venturi size in inches
1-7/16--1-1/8 primary; 1-7/16--1-1/4 secondary = 486cfm
1-7/16--1-1/8 primary; 1-11/16--1-15/32 secondary =553cfm
1-9/16--1-1/8 primary; 1-11/16--1-15/32 secondary =692cfm

Your carb is off of a 64-65' 330cid. Carb # as per rebuild kit site says #'s7023054, 055 for 63' 215cid.
http://www.carburetor.ca/carbs/kits/CK515.htm

I would bet the one you need is the 486cfm. The 692cfm is probably for the 394/425 engines.
The 215cid only needs 400cfm @6000rpm though.

63 F85 Cutlass · January 19th, 2009, 05:04 PM

Thanks wireman

Through one of those carb size calculations, the optimum size is a 372cfm, and the closest I can find is a 390cfm, so I'll probly rebuild the rochester on it now, and If I feel its too big i'll spring for the holly 390cfm (if funds permit)

Thanks again, and if anyone has anymore input, I'm still listening.

-Ryan

Wireman134 · January 19th, 2009, 05:16 PM

As long as you stay out of the secondaries the 553cfm will drive the same I would think. Most factory carbs have been over sized anyway.

63 F85 Cutlass · January 19th, 2009, 05:23 PM

Ok, I'll have to see how its doing next time I see it. Its at my grandmas in here garage for the winter because I'm in colledge at the moment. I just found a vaccume leak to the carb when I started it sunday, so when I replace the split hose, i'll see what she needs. I'm pretty sure the throttle to venturi sizes are that of the 486 cfm.

Wireman134 · January 19th, 2009, 05:58 PM

Found this Rochester 4G manual on PDF.

http://www.carburetor.ca/pdf_manuals...er4GManual.pdf

January 19th, 2009, 03:49 PM	#1 (permalink)
63 F85 Cutlass Registered User Join Date: Nov 2008 Location: Colchester,CT Posts: 74	What size is my carb? My 63 F85 with a 215 has a rochester 4 barrel on it, Its not the original one, I'm trying to figure out how big it is so I can decide weather a new one would be benificial, or if rebuilding this one will be fine. I'm not sure if its too big for my motor. The number on the tag is 7025054 From decoding I know 70= Rochester 25= 1965 0= 49 state monojet 5= Oldsmobile 4= Automatic Tranny None of it told me size, and the applications I found it listed for were either a 330 or a 400 If anyone posseses this knowledge, it would be grately apretiated. Thanks guys -Ryan

January 19th, 2009, 04:34 PM	#2 (permalink)
Wireman134 Registered User Join Date: Jul 2008 Location: Manhattan, Illinois Posts: 113	I have this information from HPBooks "Rochester Carburetors" by Doug Roe @1986 Model 4G: Throttle bore -- venturi size in inches 1-7/16--1-1/8 primary; 1-7/16--1-1/4 secondary = 486cfm 1-7/16--1-1/8 primary; 1-11/16--1-15/32 secondary =553cfm 1-9/16--1-1/8 primary; 1-11/16--1-15/32 secondary =692cfm Your carb is off of a 64-65' 330cid. Carb # as per rebuild kit site says #'s7023054, 055 for 63' 215cid. http://www.carburetor.ca/carbs/kits/CK515.htm I would bet the one you need is the 486cfm. The 692cfm is probably for the 394/425 engines. The 215cid only needs 400cfm @6000rpm though. Last edited by Wireman134; January 19th, 2009 at 05:01 PM..

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January 19th, 2009, 05:04 PM	#3 (permalink)
63 F85 Cutlass Registered User Join Date: Nov 2008 Location: Colchester,CT Posts: 74	Thanks wireman Through one of those carb size calculations, the optimum size is a 372cfm, and the closest I can find is a 390cfm, so I'll probly rebuild the rochester on it now, and If I feel its too big i'll spring for the holly 390cfm (if funds permit) Thanks again, and if anyone has anymore input, I'm still listening. -Ryan

January 19th, 2009, 05:16 PM	#4 (permalink)
Wireman134 Registered User Join Date: Jul 2008 Location: Manhattan, Illinois Posts: 113	As long as you stay out of the secondaries the 553cfm will drive the same I would think. Most factory carbs have been over sized anyway.

January 19th, 2009, 05:23 PM	#5 (permalink)
63 F85 Cutlass Registered User Join Date: Nov 2008 Location: Colchester,CT Posts: 74	Ok, I'll have to see how its doing next time I see it. Its at my grandmas in here garage for the winter because I'm in colledge at the moment. I just found a vaccume leak to the carb when I started it sunday, so when I replace the split hose, i'll see what she needs. I'm pretty sure the throttle to venturi sizes are that of the 486 cfm.

January 19th, 2009, 05:58 PM	#6 (permalink)
Wireman134 Registered User Join Date: Jul 2008 Location: Manhattan, Illinois Posts: 113	Found this Rochester 4G manual on PDF. http://www.carburetor.ca/pdf_manuals...er4GManual.pdf