Author Topic: Stock or "modified" carb rebuild?  (Read 3038 times)

Offline streetjeep

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Stock or "modified" carb rebuild?
« on: March 04, 2013, 04:48:24 AM »
I have a factory 250 HP 68 327 with 4bbl Quadrajet #7028212. After sitting in a barn over twenty years I am hoping this summer it gets rebuilt and put in my Jeep Comanche.  I will use a Weiand manifold, headers, a Pure Energy CompCam, and possibly the one step up from stock World heads (larger valves), and this will probably bump it to 3-320hp.   ;D  It will be a street daily driver. When I rebuild my carb, should I do anything different than stock rebuild?

Offline Shark Racer

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Re: Stock or "modified" carb rebuild?
« Reply #1 on: March 04, 2013, 08:51:28 AM »
Are you talking about the S/R Torquer heads? Or something else? The S/R Torquer heads are pretty much a complete stock replacement, and aren't particularly good. They might be better than a small valve stock casting, but that's about it. You'd be better off going with Vortecs, and much better going off with something like a Trick Flow or AFR aluminum cylinder head.

Anyhow, it does sound like you'll need to modify the carb settings to get the most out of your new engine. I am not good at all at recommending mods as I simply don't have the experience to make even a decent guess, but the others who do will want to know the specs of your cam and the planned static CR most likely.

Offline Cliff Ruggles

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Re: Stock or "modified" carb rebuild?
« Reply #2 on: March 08, 2013, 04:00:43 AM »
Considering the application, I would use the factory replacement 350/300hp camshaft.  It will idle great, and make TONS of low end power with a broad power curve.  They are available thru most auto parts stores, including NAPA, part number CS-274. 

Rebuild the carb to stock specs with one of our kits, and use the stock jets and metering rods.  Replace the power piston spring as well, most of those are rusted and/or weak due to age.

Bottom plugs will be leaking, seal them up during the rebuild, we sell a kit for them......Cliff

Offline streetjeep

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Re: Stock or "modified" carb rebuild?
« Reply #3 on: March 08, 2013, 06:16:42 AM »
Considering the application, I would use the factory replacement 350/300hp camshaft.  It will idle great, and make TONS of low end power with a broad power curve.  They are available thru most auto parts stores, including NAPA, part number CS-274. 

Rebuild the carb to stock specs with one of our kits, and use the stock jets and metering rods.  Replace the power piston spring as well, most of those are rusted and/or weak due to age.

Bottom plugs will be leaking, seal them up during the rebuild, we sell a kit for them......Cliff

Thanks, Cliff. Will do on carb as you say. You are the expert there! 
On the cam, are you sure of that number? Did some reading, and summit says the Sealed Power CS-274 is the stock replacement cam for 327 (except Hi-Performance) and every stock 350 no matter the HP.  Advance Auto does not list it as one of the Sealed Power "performance" cams for what I put in as application; 1972 Biscayne with a 350.  Compared it's lift to the stock 250 hp 327's as stated in a spec sheet I have from GM for the 1968 full sized chevy and they are identical. That same sheet says the 327's duration for the Intake is 280 excluding ramps and 310 including ramps, and for the Exhaust 288 excluding and 320 including ramps.  Don't know how to cipher that IRT the "at 50 degrees" for the CS274 but if it means subtracting 50 from each of these numbers, the CS274 has less duration than the stock 68 cam. 

Offline billy 2

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Re: Stock or "modified" carb rebuild?
« Reply #4 on: March 09, 2013, 06:56:00 AM »
I have used the 274 small block cam shaft in many of the engines that I rebuilt over 30 years.  I have had extremely good luck with them and, as Cliff said, it has a good power range for a street car.  I would not be afraid to use that in any small block Chevrolet.  billy 2

Offline Cliff Ruggles

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Re: Stock or "modified" carb rebuild?
« Reply #5 on: March 12, 2013, 05:51:57 AM »
+2

Used that cam many times, it's a great choice for any truck or mild performance application, where smooth idle, and strong low end power are required, with broad mid-range power. 

Larger cams, especially "RV" grinds really need increased compression as they shift power up in the rpm range, and hurt performance at low rpm's.

The CS-274 will also be the hands down winner for fuel economy.  We've hid mid-20's with that cam in several applications, including a 1967 Impala SS I used to own with a 327cid engine in it.  It was backed by a 4L60 transmission and 3.31 gears....Cliff