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Old 08-21-2013, 07:46 PM
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355 SBC cam recommendations-425hp

I will be rebuilding my 350 which is my first build and looking to produce about 425hp.

I'm starting with a 1996 .030 over block, forged scat rods, scat crank, speed pro pistons 10.1cr using pro comp aluminum angle plug heads 64cc 2.02 intake/1.60 exhaust. 1.6 roller rockers with girdles.

Current cam is LT4 Hot Cam duration at .050" tappet lift (intake/exhaust) is 218/228; and maximum lift with 1.6 rocker ratio (intake/exhaust) is 525/525. Roller lifters, Summit dual plane intake.

While i have the motor apart i think i would be better served with a bit more radical cam, looking for recommendations/part numbers, I'm assuming i have to change out the valve springs also.

TH350- 2600 stall
Rear gears-3.42 posi (Possible future upgrade to 3.73
Rear tires- 275/60/15
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Old 08-21-2013, 08:27 PM
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what are you using for intake and fuel management? what size and type of headers?
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Old 08-21-2013, 09:18 PM
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You don't need to change anything except the cylinder heads.
and maybe the carb get a 750/800cfm HP carb.
Sell the heads to someone you don't like.
If you only want to run mild gears and mild stall then keep the moderate camshaft
Get horsepower by using much better cylinder heads
EG AFR 195cc eliminator and a Performer RPM intake and 750-800cfm carb
1-3/4" long tube headers 2-1/2" dual exhaust.
It will make 425++hp without changing the LT4 hot cam camshaft.

You probabily don;t even need to rebuild the motor.
its the heads that are killing it.

Last edited by F-BIRD'88; 08-21-2013 at 09:34 PM.
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Old 08-21-2013, 09:39 PM
How fast is fast enough?
 
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The recent versions of those heads are not that bad. They're not afr quality but they're better than anything oem. A port clean up and maybe valve job should be enough on them. Didn't mention the headers or exhaust, there's a lot of power there. And lastly the tune, dyno time will help you tune for peak numbers. The cam should be adequate if you clean up the heads run a good exhaust and get the tune dialed in.
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Old 08-22-2013, 05:48 AM
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Intake is summit dual plane- made by weiand
Headmen headers #65104 1 3/4 primary
Carb is carter 625 cfm which i will be replacing. Thinking holley 670 or 750..
New heads are not really in the budget
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Old 08-22-2013, 06:28 AM
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A 750 CFM carb will help
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Old 08-22-2013, 07:18 AM
How fast is fast enough?
 
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going to at least a 750 will help peak power numbers, and get the damn thing dialed in (this doesn't mean just swapping out jets either!) Getting your carb tuned in makes a hell of a difference- the problem with a carb is that keeping it dialed in is damn near impossible when the weather changes. May want to consider going to EFI instead of a new carb if this is driven on the street. For a track only car a carb is easier to tune as you're always at WOT, and can just tune it every time you go to the track for current track conditions.
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Old 08-22-2013, 12:48 PM
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Quote:
Originally Posted by maddart View Post
I will be rebuilding my 350 which is my first build and looking to produce about 425hp.

I'm starting with a 1996 .030 over block, forged scat rods, scat crank, speed pro pistons 10.1cr using pro comp aluminum angle plug heads 64cc 2.02 intake/1.60 exhaust. 1.6 roller rockers with girdles.

Current cam is LT4 Hot Cam duration at .050" tappet lift (intake/exhaust) is 218/228; and maximum lift with 1.6 rocker ratio (intake/exhaust) is 525/525. Roller lifters, Summit dual plane intake.

While i have the motor apart i think i would be better served with a bit more radical cam, looking for recommendations/part numbers, I'm assuming i have to change out the valve springs also.

TH350- 2600 stall
Rear gears-3.42 posi (Possible future upgrade to 3.73
Rear tires- 275/60/15
What you have with an Edlebrock Performer RPM intake or a Victor Jr with a 750 Holley or Holley clone in place of the Summit intake and 625 CFM carb should go to an easy 425 on an engine dyno. I'd keep a half set if 1.5 roller rockers in my tool box, often on these split intake to exhaust duration cams the use of 1.5's on the exhaust has the effect of bringing the power band down a few hundred RPM with no sacrifice in the top end power. just widens the peak curve over more RPMs. So this is a useful tuning item as are carb spacers.

The Comps are an OK head especially the latest go around. They like a lot of lift on the intake. They also respond to a back cut of 30 degrees on both the intake and exhaust valves more than most other heads, this will pick up the Comp's rather weaker mid lift flow as well.

Valve springs should be a decent quality beehive. These things really keep the valves under control without having to go to exceptionally stiff springs.

Other than that this should be good to go where you want.

Bogie
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