ok i have a stock 350 and i wanted to get more power from it. I was looking through summit racing catalogue and they have some cylinder heads for about 1500 to 2000 made by trick flow and they tell you how much horsepower you will get by using them. My question is are the numbers accurate or atleast close to it because theyre saying that all i have to do is put these cylinder heads on and i will get 350hp,400 hp from another cylinder head set and so on and so forth.It seems a little to good to be true for me.

 

I hope they say something like, "...with xxx cam and yyy induction and zzz exhaust...", because those also play a big part in power made.

$1500-$2000 is a lot of money for 400 HP heads these days.

 

If you read the print above the section of dyno chats it will tell you what bore and stroke the engine was on the graph, also the cam size and other specs are listed below them i believe, aluminum heads do not make more power but the decrease is allot of times a desired gain for allot of people, two aluminum heads weigh about what 1 cast head weighs.

 

It comes with assembled cylinder heads,cam and timing chain. It said it was tested with a holley 600 and a edelbrock rpm intake. It seems like a good deal to me considering a 3000 dollar supercharger will only give you around 150hp but i just dont believe the horsepower numbers for the cylinder head package. Have anybody ever bought one of these kits and is trick flow a popular brand?

 

Trick Flows were pretty hot about 10 years ago.

A stock 350 can easily make 400 HP. Port the heads, XE274 (or similar roller grind) cam, Performer RPM intake, 650 DP Holley. Assuming good exhaust (headers, free-flowing back to the rear bumper), that's an easy 400 HP package.

The cam in that package is most likely flat tappet. If this is a stock 3rd gen 350, then it is a roller lifter cam. I'd stick with that type, even though higher priced, before going with a "package" flat tappet cam.

If you insist on changing the heads, then the SDPC2000.com upgraded Vortec package makes more sense. Vortec heads capable to .525" lift, RPM Vortec intake, rockers, bolts, gaskets - $1100. Add $250 for a roller XR274 (or whatever it is exactly), plus a little for small parts, you're under $1500 and again, well over 400 HP. (Of course, you need to buy the carb, but that wasn't included in your $1500-$2000 package, either.)

 

by stock 350 im talking about like 240hp. So your saying all i have to do is upgrade my exhaust, cam, intake, carb and port my heads and that will bring me to around 400hp?

 

I would also replace the valve springs, either pin the rocker studs or have the heads machined to accept screw-in studs, and have the valve guides cut for positive-type stem seals.

We need to understand some things about horsepower ratings. That "400" number is "gross" flywheel horsepower, meaning on a dyno with longtube headers, most likely no mufflers, an electric water pump powered by the dyno facility, same with fuel supply, no alternator, a velocity stack on the carb. The "240" number is "net" flywheel horsepower, meaning the engine on a dyno with exhaust as-installed in the car, the engine powering the alternator, water pump, and fuel supply, the air intake as-installed in the car, etc. That is typically 10-20% lower than a "gross" rating. So, that 240 horse engine, with headers, performance intake, carb, velocity stack, electric water pump, etc., would pull about 260-300 HP. So, getting to "400" HP is a matter of increasing that by a little over 100 HP.

With that in mind, a stock L98 with ported heads, a cam like a Comp XR276HR or XR282HR, Performer RPM intake, and 650-750 Holley, would be very close to or over that 400 HP mark.

 

Well if you went the distance withe your stock heads you would not make the better of an aftermarket head, doing new springs, larger valves, port, polish, studs, guidplates, and even angle mill you could easile find a aftermarket set of heads that would compete with what you would spend on re amping a set of factory castings and the gains would not be better than the aftermarkets.

 

There are many paths to this destination.

For instance, stock ported heads:
Electric die grinder, 1/4" collet, $80; Standard Abrasives Deluxe Porting Kit (includes great instructions, with clear pictures, on what to do), $35; a couple of burr/tree carbide bits, $25; dust masks & goggles, $15. Valve springs, retainers, & seals, $160. Pinning rocker studs, $5 (assuming you have a drill and drill bits already). Valve job afterwards, including cutting guides & assembly, $200. Gaskets, $100. RPM intake, $135. Misc (shipping, tax, gasket sealer, etc), $100. Total: $855. My first time porting job took me 10 hours (plus about 2 hours practicing on an old head doing one cylinder).

SDPC2000 Vortec head kit:
http://www.sdpc2000.com/catalog/2172...former-RPM.htm, included heads, gaskets, manifold, bolts, rockers. $1030 plus shipping (probably $100 or so). To me, this is the best package out there for the money for good heads and what's needed to support them. It includes things that you don't get with any other package I've seen.

Either of these routes would easily get you to 400 HP with the aforementioned Comp roller cam ($260) & Holley carb (~$350). But, obviously, the stock heads can be done for less than buying new heads. For 400 HP, you don't need $1500 heads (or heads/cam package).