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Carb choice, cam choice

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Old 12-04-2016, 09:30 PM   #1
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Default Carb choice, cam choice

I'm building an exo hot rod based on C5 corvette 6-speed manual drivetrain and running gear.

I'm expecting the final weight to be between 1800 and 1900 pounds.

I found a Victor Jr. locally, fairly cheap, and I like the look so that's what I'm going to run.

I'll start with the stock exhaust manifolds, but I'll go to long tubes at some point.

No plans for big power at this point, but I want stuff to kind of work together.

I'm not sure if a Holley 650 or 750 will be best. Double pumper, manual choke. I'd like to go with a cheaper, older model if that's not unwise. Any helpful advice on this?

Also, I'd like to swap in a cam that matches the combo a bit better than the stock setup, but I want to do it as cheaply as possible. Any helpful advice on this?

Thanks,
Micah
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Old 12-05-2016, 04:43 AM   #2
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On the cheap...I would guess the ASA cam would be a decent pick in a mostly stock motor.
As for the carb....a 650 will work fine.
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Old 12-05-2016, 04:57 AM   #3
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I run a 750 DP with a manual choke on my stock cam 6.0L. Motor has a GMPP single plane intake very similar to your Vic Jr. A 750 is by far the most common size on carb'd LS motors. Get a 750

As for old or new doesn't really matter if you aren't afraid to drill out the idle feed restrictors and maybe airbleeds. The newer HP carbs seem to have an out of the box calibration that is better suited to LS motors with their high flowing heads and roller cams. But with a little bit of effort you can dial in a swap meet vintage double pumper.

Invest in a good wide band O2 sensor with data logging capability. That is almost a necessity to get the carb right.

As for cams you will need to provide a good bit more info, like what motor/heads you have and how you intend to use the car. If that were my car I would get something optimized for higher RPM HP. Cam Motion seems to be this forum's cam vendor of choice these days. They have some very good packages geared toward carb'd LS motors. Lunati has some super high lift cams with carb profiles. Can't say I have seen anyone on here who runs one though, even their mildest cam seems like too much for a street car. A full cam kit with proper valve springs will run a grand. If you want cheap than see if you can source a GM hot or ASA cam.

I'm happy with the stock LS2 cam. I'm definitely leaving some HP, but one thing for sure at your vehicle's weight pretty much anything you choose is going to scream.
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Old 12-05-2016, 10:33 AM   #4
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Quote:
Originally Posted by MJFuss View Post
I'm building an exo hot rod based on C5 corvette 6-speed manual drivetrain and running gear.

I'm expecting the final weight to be between 1800 and 1900 pounds.

I found a Victor Jr. locally, fairly cheap, and I like the look so that's what I'm going to run.

I'll start with the stock exhaust manifolds, but I'll go to long tubes at some point.

No plans for big power at this point, but I want stuff to kind of work together.

I'm not sure if a Holley 650 or 750 will be best. Double pumper, manual choke. I'd like to go with a cheaper, older model if that's not unwise. Any helpful advice on this?

Also, I'd like to swap in a cam that matches the combo a bit better than the stock setup, but I want to do it as cheaply as possible. Any helpful advice on this?

Thanks,
Micah
Great project! I Love the EXOs and would not mind building one myself.

Camshaft choice will depend on the power goals you have and the personality and driving characteristics you want from the engine. In a very light vehicle with a manual transmission that is capable of such incredible handling, I think you will like the engine to have a very wide and smooth powerband.

For you, I would pick a camshaft that would provide a great power increase, increase the RPM range and still have great street manners in your light vehicle. For that criteria, I would recommend the Titan 4 camshaft: http://store.cammotion.com/the-titan4

As for the carburetor, the 750 mechanical secondary Holley will be a good choice. You can absolutely rebuild and older unit. The old model 4779 750 holley is a great carburetor but there are a few caveats: 1. Often, the older carbs have worn throttle shafts that can be sticky or bind. 2. The metering blocks in older carberetors can get crud inside the passages causing problems with the fuel metering that can be maddening. So, while you can just rebuild an older unit, you may run into some grief with those issues.
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Old 12-05-2016, 06:41 PM   #5
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Thanks guys. Good info. Confirmed a lot of what I was thinking.

Apparently the wider lobe separation of the FI cams isn't too much of a problem on the Vic Jr?
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Old 12-13-2016, 11:19 AM   #6
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Thanks guys. Good info. Confirmed a lot of what I was thinking.

Apparently the wider lobe separation of the FI cams isn't too much of a problem on the Vic Jr?
The lobe separation number itself is not a problem. What the Vic Jr typically needs to maintain good mid-range torque is a camshaft earlier intake valve events. The Titan IV has an intake valve open of 4.5 degrees BTDC @ .050" and an intake close of 42.5 degrees ABDC @ .050". These are great for your application and desired RPM range. One of the reasons this camshaft has a 113 degree lobe separation angle is that it only has 3.5 degrees of overlap due to its conservative 1 degrees BTDC exhaust valve close. This limited overlap design helps smooth out the idle and limit any low speed bucking that might make driving a light, stick shift vehicle less fun.
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Old 12-17-2016, 09:55 AM   #7
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Doug and Pop, you both mention the GM ASA cam as cheap. I have been looking for one, not the Hot Cam, and the best price I can find is $470. Do you know where I can find one at a better price?
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Old 12-17-2016, 01:39 PM   #8
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This one is very close in specs.... but you could go with any Mfg. you'd like.

http://www.jegs.com/i/JEGS-Performan...00579/10002/-1
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Old 12-17-2016, 05:35 PM   #9
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Doug and Pop, you both mention the GM ASA cam as cheap. I have been looking for one, not the Hot Cam, and the best price I can find is $470. Do you know where I can find one at a better price?
They are cheap when you can find them used. They show up in the classified from time to time.
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Old 12-18-2016, 08:42 PM   #10
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Thanks guys. I appreciate the info.
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Old 01-08-2017, 08:23 PM   #11
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is that a kit or did you build it
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