I'm building a 355, 530/542 solid lift cam, 1.6 roller rockers, ported 350 heads with 194 valves, 9-1 compression, edelbrock perfromer 750 carb, about how much hp will I be making ?  

need more info than that you provided....

 what is the casting number on the cylinder heads you've chosen?

 you mention porting... were you provided with flow numbers for the finished ports? or, is it a home cleanup of the bowl area type port job?

what brand intake manifold are you using? is there any work done to it?

 need event timing for the camshaft. if you are unsure what i mean give me the part number and manufacturer .

what type of ignition are you working with? initial timing, total timing....?

headers? diameter......

I'm not sure on the casting numbers, all I know is that they have the bigger 194 valves and 76cc combustion chambers, giving me the 9-1 compression, the port work is going to be the at home smoothing out the bowl area on the valves, I'm going to port the intake an exhaust runners also, I will port the intake manifold to match the runners, the intake is an aluminum dual plane, ignition I'm not sure yet, the headers have 1/4 collectors, they are the summit brand headers for an 86 camaro, I was advised on another forum to go with a smaller lift cam because of my compression, so I've decied to go with a 508/508 solid lifter with 249/249 duration at .050, the intake manifold is the typhoon at www.midwestmotorsports.com, about how much hp will I be making ?  

Sounds like a smog head.....

Cam is a bit large for my taste.  Why are you running so much duration?  It will be a dog on the street.....won't shine until upper RPMs....I'd recommend something more like 224-236 @.050 intake, 224-246 @.050 exhaust...depends on the application- stoplight racer, drag, road, show, ?

Have you had the heads machined for larger springs?  To get the flow that you'd need out of a smog head, you'll need to do a LOT of porting, use valves like Manley Race Flo's, screw in studs, cut for larger springs, etc.....by the time you are done, you'll have as much $$ as it would cost for a nice set of aluminum heads. 

Those Summit headers are ok, but you will be better off w/ LT's in the long run.....shorties are better than nothing, and if you've dropped the car a couple inches, make a world of difference in clearance. 

My personal favorite site for all things Fbody....www.z28.com. ; I am biased, though .  Good folks- talk to BBCam, he won't BS you one way or another. 

You don't have enough compression to run this cam effectively. As duration goes up, usually the amount of overlap also goes up. This however, also, depends upon Lobe Seperation Angle (LSA). Less LSA nets more overlap, more LSA less overlap for otherwise identical durations. All we're talking about is taking the cam lobes, intake and exhaust, and twisting them toward or away from each other.

Anyway the heart of the matter is that as overlap goes up, bottom end and mid range torque goes down because in these lower RPM ranges there isn't enough mixture velocity inside the intake system to overcome the reverse pulsing caused by residual pressure in the cylinder when the intake valve is opened early while the exhaust valve is still open. To compensate for this, static compression is rasied to force more power out of the weak bottom end charge, we're speaking of not many mixture molecules and some exhaust gases being present in the low thru mid RPM range. This is one reason why a large cammed engine lopes at idle because the mixture has low density and is contaminated so combustion is not steady, if at all. The other reason that contributes to a low density (weak) charge is a late closing intake, this is another characteristic of a long duration cam. Here the piston has risen 40 degrees or so beyond Bottom Dead Center (BDC) and if the mixture velocity in the ports is too slow, the piston blows some mixture that it took in on the suction stroke back into the intake. At high RPM, the mixture has enough velocity that its inertia overcomes the piston's reverse pumping after BDC and continues to pack the cylinder. But you've got to get the engine spinning fast enough for this to happen. This is harder to do on the street, it really requires a manual gear box and some stiff final gears in the rear end to give you the ability to keep the revs up high regardless of road speed. Automatics really don't like this kind of treatment, up and down the gears all the time, and have short lives under these circumstances irregardless of any super-duper parts you put in them.

I'm not saying to build like this, just makeing you aware that a race engine on the street is a real headache to live with. Great on the Saturday night stoplight to stoplight Gran Prix, but a real pain if you drive this thing to and from work everyday.

Open chamber heads are either GM SMOGers or after market race heads if their not GM. 1.94/1.55 valves are standard GM fair for 327/350 heads, the high performance heads often, but not always, use a 2.02/1.60 combination. Open chamber heads are best used where the engine exceeds 6000 RPM all the time and acceleration and fuel economy are not concerns, they're also necessary when using methanol or nitro-methane fuels, which are extremely rich mixtures using at least twice as much fuel as gasoline. But on the street burning gasoline they're lazy, fuel hungry, low emission heads. To get the compression up where you need it with these cam selections, you need compression around 10 to 10.5, that's hard to do with an open chamber head without resorting to a pop-up piston. Pop-ups don't have very good flame propigation characteristics, they require lots of timing advance, are detonation prone, like overly rich mixtures, generate lots of pollution and just don't produce much power for all these extra problems. They're best relagated to pro racers with liquid dynamite for fuel or low compression, low emission grocery getters. A modern head using tight small fastburn combustion chambers, like the Vortec, are a 40 to 80 horsepower bolt on. An aluminum head will easily take another ratio higher than the best cast iron and this getting up into the 11s can be necessary if the cam is long enough and the overlap and late closing events big enough. This is more important than lift. However, big lift events on SMOG heads is a waste of effort, the ports on these heads don't flow enough to take advantage of high lifts. If you take a look at documented port flows, you will find that 160 to 190 cc ports show a flattening in the rate of flow increase often starting as low as .4 inch lift. This is showing that the port is reaching capacity, thus lifting the valve higher simply brings diminishing returns against the mechanical problems encountered with the cam, lifters, pushrods, springs, rockers, etc. with increasing lift. At this point more valve timing would be required to buy more open time with which to fill the cylinder, but like everything else, there's limits here as well.

1.6 rockers make the cam act as if there's more cam timing as well as more lift. They not only make the max lift at the valve bigger, but the exaggerated lift ratio is seen as more amount everywhere in the lift rate. This has its good and bad effects. The engine reacts like it has more cam, so at low thru medium revs the reverse pumping issues are greater, the top end will be stronger, wear problems in the valve actuation system get worse. As cam timing gets larger and valve springs get stiffer, you've really got to install a cam bumper to take the thrust loads off the cam lobes and lifters. You should also consider drilling a .030 inch hole from the cam gear thrust surface of the block into the oil passage that services the #1 cam and main bearing to supply pressure oil for this highly loaded surface. As normally installed the engine sits at about a 3 degree angle toward the rear, this means that most drain oil from the top end goes to the sump from the back of the engine, leaving scant little dribbling down the front to lube the timing case components. This only gets worse when racing where "G" forces especailly when accelerating do even more to push drain-back to the rear of the engine. (Plugging the rear drain backs as some book and magizine articals recommend, only causes oil to puddle in the valley till it's deep enough to run down the front of the engine. This is a lot of oil not in circulation, without a deep sump pan the pump could go dry.) There is little more than cam and main bearing throw off to lube the timing case components, so the cam gear to block thrust face is left to run with mighty little oil unless you do someting to put some pressure lube on the thrust face.

Your engine would be about 400 hp. But for a street engine it's a pretty crude and inefficient design, for a race engine, the open chamber heads won't maximize output unless your running "fuel" and then a whole lot of work needs to be done to get ports big enough to both accommodate a doubling of fuel volume (weight actually) and enough air to burn it. With modern heads there's better ways to get 400 hp than lots of cam and high ratio rockers.

I know you've spent al lot of money, but you really need to go back to the drawing board.

To be of any further help a lot more technical data is needed, like piston part number, head casting number, all the data off the cam's timing card, etc.

Bogie  

thanks for all of the help, it's a lot better than other forums that just harp on me because the compression isn't enough, I haven't actually got the engine completely together yet, all I have in it are the .030 hypereutectic flattop speed pro pistons, crank, and all of the bearings and plugs, I think I have found a cam that would be better, it's a speed pro "cheater" hydraulic lift cam, .510/.510 lift, 244/244 duration, I'll try to get the casting numbers from the heads when I go to the shop tomorrow.  

Looking forward to the numbers.

Bogie

sorry for not responding sooner, but I've decided to ditch the 350 heads and try and find a pair of 305 heads with the small combustion chamber to bump my compression up to 10.4-1, with the 194 valves, I'm going to port those and then have them machined for 202 valves, I think my cam will work a lot better with that setup, it's a 510/510 lift 244/244 duration at 050 hydraulic lift, I hope to pick up 30-50hp from all of that, I think I will be making around 425hp, if I have enough money I'll dyno it when it's done

I need to slow you down a bit, reworked 305 heads with bigger valves and enlarged ports were the poor man's way to big power back in the 80s thru mid 90's when 1960's era heads couldn't be found. Today, by the time you invest in a set of 305 heads to feed a warmed up 350, you will have sunk as much or more money into those heads as you could have a set of Vortecs or aftermarket fast burn chamber heads, which will deliver as much or more performance as reworked 305s, but more importantly are more reliable as the 305 head has to be ported just short of getting wet, and you might have to go through several before you can open up the ports enough and not get wet. These very thin walled ports that result really aren't too keen on heating and cooling cycles that you want from a street machine.

I'd put together a realistic cost estimate of reworked 305 heads against a new set of modern heads before commiting my checking account to this project. Don't forget to look at Ebay there's a lot of Chevy stuff out there used or rebuilt as well as new.

Bogie