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Old 04-27-2012, 12:32 AM
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I need some sbc hp help

I have a 86 C10 with a .030 over 350. I'm trying to build a nice street-rod, maybe 310-350 horses. Here's are my specs so far. Flat top pistons, Crane 1.52 Roller Rockers, 1.94-1.5 ported 305 heads (For now), Edelbrock Performer EPS intake, Holley 600 carb, Flowtech long tube headers, true dual Flowmaster super 44s, 2 inch open chamber aluminum carb spacer, MSD street fire distributor, Accel plugs and 8.0 wires. I don't know the cam size but its a hair over stock. I know the heads are the biggest problem but I'm working on that, so here's my question. I'm looking at a set of GM Performance cast iron vortec heads. Are these a good match for the specs above aside from the intake. Or will I have to change the carb, stall and cam too. And if so what do you guys recommend? I might take it to the track occasionally like once or twice a year but I want the power just in case some kid wants to try me at a light. Other than that its just a weekend crusier

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Old 04-27-2012, 01:14 AM
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Quote:
Originally Posted by ant07
I have a 86 C10 with a .030 over 350. I'm trying to build a nice street-rod, maybe 310-350 horses. Here's are my specs so far. Flat top pistons, Crane 1.52 Roller Rockers, 1.94-1.5 ported 305 heads (For now), Edelbrock Performer EPS intake, Holley 600 carb, Flowtech long tube headers, true dual Flowmaster super 44s, 2 inch open chamber aluminum carb spacer, MSD street fire distributor, Accel plugs and 8.0 wires. I don't know the cam size but its a hair over stock. I know the heads are the biggest problem but I'm working on that, so here's my question. I'm looking at a set of GM Performance cast iron vortec heads. Are these a good match for the specs above aside from the intake. Or will I have to change the carb, stall and cam too. And if so what do you guys recommend? I might take it to the track occasionally like once or twice a year but I want the power just in case some kid wants to try me at a light. Other than that its just a weekend crusier

what cam are you running?
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Old 04-27-2012, 06:01 AM
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I'm not sure about the specs but the builder said its the biggest one you can get before you need a stall converter its a hydraulic flat tappet..
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Old 04-27-2012, 08:15 AM
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I think Vortecs heads would be great for you motor. What kind of carb do you have now? If you have a squarebore 4150 style you choices are unlimited, but if you have a Quadrajet your choices are somewhat limited, but still available.

Are you prepared for the cost of just switching over to Vortecs? You will need:

Vortec heads
Center bolt style valve covers
Valve cover gaskets
Valve cover bolts
Vortec style intake manifold
Vortec style intake manifold gaskets
Vortec style intake manifold bolts
New heads gaskets
New head bolts

It sounds like you have a mild enough cam that you will not have to modify the heads for extra valve lift (but you need to verify for sure). However, you will still probably need to take them to a head shop to either swap the old springs and get them at the correct installed height, or install new ones at the correct installed height, or I supposed you could take your chances if you get pre-assembled heads and use whatever is installed and hope you don't wipe your cam lobes.
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Old 04-27-2012, 08:39 AM
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Thanks. Its a 4150 series 600 Holley Carb, I was planning to go with the assembled GM performance vortec's from Jegs. If I decide to change the cam what size should I go with for a smooth lope. Don't want the dragster sound
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Old 04-27-2012, 09:54 AM
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Quote:
Originally Posted by ant07
Thanks. Its a 4150 series 600 Holley Carb, I was planning to go with the assembled GM performance vortec's from Jegs. If I decide to change the cam what size should I go with for a smooth lope. Don't want the dragster sound
You will want a cam with an intake duration of 206-210 and a gross valve lift around .450" assuming you are using 1.5:1 rockers (or lobe lift around .300") to make around 300-350 HP. Keep in mind OEM Vortecs may not handle .450" lift. They vary, some could go .490" without being modd'd. You will have to check yours. Also if you use the good positive type valve seals you will need to account for that as well as they take more room. The solution is to grind down the tops of the valve guides. You can get a special tool from Comp Cams or Crane Cams, or you can take it to a head shop and have them do it.

To smooth out idle will want to have a wide lobe seperation angle (LSA). Something like 114. This will decrease valve overlap. My cam has a 60 overlap and is considered lopy.

Also to smooth out idle you will want an early closing intake valve. The later the intake valve closes (which occurs after BDC) the rougher the idle (intake reversion occurs). My cam closes around 60-64 a BDC and is considered lopy.

Comp Camps has a pretty decent tool to help get you started: http://www.camquest.com/

You could call their technical support guys on the phone, but you should consider their advice along with that link I sent you, my advice, your intuition, and the advice of others here. No one is right, you must weigh all options and resources and information.
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Old 04-27-2012, 09:58 AM
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Also BTW, a rule of thumb.

Intake duration determines where power is made. Less duration, low RPM power. More duration. High RPM power.

Valve lift determines how much power is made. More lift, more power. Less lift, less power.

More radical cams (aka more duration) require higher static compression ratios. Since the intake valves closes later and reversion occurs, the cylinder doesn't built up PSI as easily.

Conservative, less radical cams, like what you want, build PSI a lot more easily because the intake valve closes sooner, so you need less compression. For the cam I suggested earlier, you probably want to stay around the 9.1 - 9.4:1 range if you expect to run on 87 octane.
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Old 04-27-2012, 10:16 AM
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Vortec heads require self aligning rockers unless guide plates are installed. A page comparing static compression to cam duration is here.
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