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Old 11-20-2012, 02:15 PM
BogiesAnnex1 BogiesAnnex1 is online now
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Originally Posted by stackitup_91 View Post
i have some questions about a build that i am in the process of Building. i Wanted to know how much horse power you all will think i will be at with this combo (TO THE TIRE) and any advice about the cam that i am using,
compression is at 10-1 I Have a 350 bored .40 over
Comp cam 292H, (501/501) Lift 1.5 ratio Roller tip Rocker Arms
VORTEC HEADS that have been modified with screw in studs. double springsswitch the heads have been machine for and they have been ported and polished
Edelbrock RPM airgap Intake
Flat top Pistons Eagle Connecting Rods (Standard Length 5.7)
700R-4 trans
650 quick fuel Carb
3.73 Rearend Gears and hooker headers..
whats would be the best cam to go with for this build?? I will be driving the car twice or 3 times a week, this motor will be going in a 1984 z28 Camaro my goal is to get at least 350 hp to the tire
Thank you and responces are appriciated
Are these roller rockers or only roller tipped? On my soap box, I have little understanding of roller tipped rockers; the help these provide is minimal at best. The real issue when it comes to rockers is the fulcrum, not the tip, due to heat generation as that affects part reliability. The ball fulcrum gets real hot real fast when it has to operate against stiff valve springs. On top of that; it gets really hot at high revs. This double whammy causes a lot of nasty fulcrum failures. From your description of this engine build, it really needs a high quality fully rollerized rocker. A stud girdle isn't a bad idea with the Comp 292 cam especially if all you did was to use a 3/8ths stud. 7/16ths is a way better place to start from for reasons of stud stability. I say this because the 292 cam is getting up on that edge where these things are necessary not over the edge yet but depending upon how hard and often you push the revs. You'll probably need more lift to get into the power range needed to put 350 horses on the rear wheel; I'd recommend 1.6 rockers to get there.

As for the heads, the Vortec will deliver into the edge of the kind of power you're looking for. But this is the upper end for them. A competent porting job is necessary but polishing is not. I don't know what you've really got in these ports but polishing is not desirable. A grinder rough surface from the cutter is more desirable in the ports especially the intake as this keeps some turbulence along the wall that helps keep the fuel mixed into the air while preventing the adhesive forces between molecules from slowing and thickening the boundary layer. This effect essentially reduces the port size as the flow sees it. Polish within the chamber can be useful to reduce carbon accumulation but here again this is zone dependent. Where the top of the port becomes the backside of the valve pocket the fuel tends to separate and run in on this side as a separate stream, again you want this to remix so the chamber should remain rough from the plug boss around the intake valve side of the chamber wall going into the turn for the bore side. You don't need to worry about carbon build up here as the fuel wash keeps this area pretty clean.
On the exhaust side polish is OK in the port where the walls converge. But when you go into divergent sections the wall should be a bit rough to again encourage diss- attachment and separation to prevent the buildup of a thick boundary layer. If you can't truly tell if the walls are converging or diverging with all the bends and twists they do this can be difficult, then the default should be cutter rough.

A lot of power can be lost between the crankshaft and the tires when an engine is installed to the vehicle. The changes I describe to your build which may also need a 700-750 cfm carb should put this engine into the 440-450 Hp categories which you're going to minimally need to put down 350 on a chassis dyno. The purveyors of chassis dynos like to talk about 15-20 percent driveline looses but it's way easy to lose as much as 50 percent. Extreme attention has to be paid to the headers and subsequent exhaust system as this is a major source of power loss between what the motor will dyno at the crankshaft and what finally gets to the tires. Other losses are to be found in the driveline and tires, but you're more limited in what you can do about this short of buying true race car parts that are way expensive. You're going to need 1-3/4 dia. long tube headers; they will need to empty into 3.0 to 3-1/2 inch collectors. This is bigger than the calculators will tell you but my experience says this is necessary to get where you want to go. A dual exhaust with a smooth cone style transition to a 2-1/2 inch to 3 inch lead pipe to a 1 or 2 chamber FlowMaster muffler. Side dumps that minimize plumbing turns are probably on order here placed to dump ahead of the rear wheels. If going behind the rear wheels go straight back to the rear instead to take advantage of the low pressure atmospheric area that follows the moving vehicle which helps pull the exhaust out, this trick does not show anything on a dyno 'cause you ain't movin'. Use either an H or X pipe depending on how much space you've got for the plumbing.

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