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Old 05-10-2013, 06:00 PM
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Camshaft help for RHS heads

Hey guys, need help choosing a cam for my 350. Here's the deal with the heads. I stumbled upon a hell of a deal last week on these rhs pro top line heads that were ported and polished, milled to 62cc from 64, and had 2.05 valves installed for a total of 500 dollars! I couldn't pass them up as he had about $2000 in them and they looked really good. He ran a best time of 11.6 in the 1/4 with nitrous in a stout 434 sb with a mechanical roller from comp with .610 lift. I'm not trying to run 11s in my nova but would like to have a very hot street/strip engine. I know a 350 is far from a 434 with nitrous but wanted to see if you guys could guide me in the right direction. I'm basically going to run a stock bottom end, I have a 650 double pumper Holley, rpm intake 1 5/8 headers with 2.5 flow master exhaust, th350(will be buying a stall converter to match combo),and 3.55 Ina 10 bolt rear end. I haven't taken off the stock heads to see what kind of pistons I have but I assume dished/flat? I am not opposed to running a solid flat tappet but a roller setup might be out of my budget unless the hp numbers would be worth it. I'm just hoping I don't have too much head on my hands for my build if that's even possible... Thanks in advance

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Old 05-10-2013, 08:07 PM
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Mark the location of all parts in the heads, disassemble the heads, take to your favorite local machine shop and have them magnafluxed for cracks. If they're solid heads, then maybe you'll share the part number and intake runner size with us so we can keep up.
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Old 05-10-2013, 08:10 PM
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If the heads flow big numbers,you will need to spin that 355 tight to use up all the flow
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Old 05-10-2013, 08:45 PM
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Originally Posted by techinspector1 View Post
Mark the location of all parts in the heads, disassemble the heads, take to your favorite local machine shop and have them magnafluxed for cracks. If they're solid heads, then maybe you'll share the part number and intake runner size with us so we can keep up.
Ok Tech I will do that but it is kind of difficult as the nearest machine shop is 80 miles away. Cracks in aluminum heads would be kind of rare no? I will post the part number as soon as I get home but im sure the runner size will be bigger as these were opened up a lot. Thank you
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Old 05-10-2013, 09:09 PM
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Using that "hell of a deal" I would sell the heads of now. Make some cash, and go buy something better suited to your needs. Your issue is going to be a typical "miss match" problem.
Big valve heads, ported runners, and enough airflow to feed a 434ci small block. While that's cool and all, its going to be lame on a stock bottom end 350. If your willing to roll the dice time and time again with 7000rpm shift points then maybe you can work with them. But then you need lots and lots of cam, which means lots and lots of converter, which means lots and lots of gear. You see where I'm going with this? Doesn't sound like it fits your "street car" wants.
If they are real clean, and you can provide documentation that shows what's been done to them then you might be able to get 1000$ for them.
Then go buy these
JEGS Performance Products 514002 JEGS Small Block Chevy Cylinder Heads
Then this
http://www.summitracing.com/parts/cc...make/chevrolet
Then this
http://www.summitracing.com/parts/hu...make/chevrolet

And now go enjoy your really stout, really fun, really streetable car.
Combo combo combo.....those heads won't fit the bill.
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Old 05-10-2013, 11:34 PM
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Ok guys heres what i found. Rhs part number 12025 BUT it has the pro top line number stamped 123 4000 00a. They do have the RHS cast in them by the rocker studs. Guy said he bought them right when RHS bought out the ProTopline brand and made quality control much better. So...they are As Cast 23 degree 200cc runner 64cc chamber (now 62) 2.02 (now 2.05) int 1.60 ext valve + 1.00 inch longer. Description actually said they are street performance/short track 327-350ci up to 6500rpm approximate 325-400 horsepower. Now I havent been able to find the flow numbers out of the box but these specs seem mild to me. One thing I forgot to mention is the guy never said how much he was spraying as far as shot of nitrous. Im guessing with porting n big mech roller he was at 475-500hp and then sprayed it with a 150 shot to get to 11.6 or something to that effect idk. Either way id be happy with 450 hp. Just to be clear, im not building a daily driver. Call my nova a weekend warrior. Just gonna take it out on a saturday night or to the track every once in a while. Will never see traffic. Hope this helps guys...
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Old 05-11-2013, 06:22 AM
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That a lot of head for your street engine. It would run better with a set that flow around 180 or so. If you are still set on them. We need the rest of your combo car weight gears transmission and so on.
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Old 05-11-2013, 06:37 AM
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The heads are good for 6800 RPM out of the box,from what I can figure out.If yours are ported?

You need to run a 7,000 rpm solid roller to get a good percentage of the power potential.If this appeals to you and drags are what the car is set up to do?You will need around 10.5:1 CR to work with that cam,,,

If your short block is near stock and you are using a flat tappet hydraulic cam,then do not use these heads.Maybe trade the heads for heads that better match your application.
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Old 05-11-2013, 10:17 AM
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The heads are good for 6800 RPM out of the box,from what I can figure out.If yours are ported?

You need to run a 7,000 rpm solid roller to get a good percentage of the power potential.If this appeals to you and drags are what the car is set up to do?You will need around 10.5:1 CR to work with that cam,,,

If your short block is near stock and you are using a flat tappet hydraulic cam,then do not use these heads.Maybe trade the heads for heads that better match your application.
You need a lot more cubes for those heads or that engine will be more happy turning higher RPM maybe up to 7500 or so. Depends on the flow numbers. A set of heads right around 165-170cc would work good with that engine.
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Old 05-11-2013, 10:28 AM
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So what you guys are saying is 200cc runners dont work on the street? These heads wont make power under 7000rpm? I guess I have to explain my goals again. I am trying to make a hot street car which basically means a car that is able to go to the track every once in a while and hold its own on the street. Im NOT trying to take FULL advantage of the flow of these heads. I know I will be leaving power on the table with stock bottom end, no NO2, etc. I kind of want to "tame" these heads if you will. I knew these were a serious set of heads when I bought them but to say they are useless on the street??? Techinspector I trust your advise, what are your thoughts if they check out good for cracks/warping?
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Old 05-11-2013, 10:47 AM
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So what you guys are saying is 200cc runners dont work on the street? These heads wont make power under 7000rpm? I guess I have to explain my goals again. I am trying to make a hot street car which basically means a car that is able to go to the track every once in a while and hold its own on the street. Im NOT trying to take FULL advantage of the flow of these heads. I know I will be leaving power on the table with stock bottom end, no NO2, etc. I kind of want to "tame" these heads if you will. I knew these were a serious set of heads when I bought them but to say they are useless on the street??? Techinspector I trust your advise, what are your thoughts if they check out good for cracks/warping?
Your stuck with the port size as a ratio of flow. Ideally the best performing head has the most flow for the least port volume. But even that ain't that simple.

What's important to behavior of the engine and where the torque and power peaks are located in the Rev range is a combination of camshaft timing, port flow velocity, and compression ratio. Your current topic is one of port velocity. Port velocity is what rams mixture into the engine, port velocity is proportional to RPM and inversley proportional to port and valve size as well as the intake valve closing event in crankshaft degrees. The latter is the subject of the Dynamic Compression Ratio (DCR) look it up I've got to blast out of here so I'll limit this to the port size for right now.

So for any given engine displacement, RPM and throttle position the larger the port the slower the flow of mixture in the port. This pushes the torque and horsepower band up the RPM range and to a great extent for which there is no inclusion in DCR calculators; the simple addition of these heads will demand more compression because the reduction in port flow velocity will make the lower RPM power band feel more cammy as if the engine was running a cam with a much later intake closure. You can get yourself into a place where the engine actually looses power everywhere because without the proper cam, compression and overall gearing that gets the revs up into the power band, the engine will be very sluggish.

Gotta run, lots more to say I'll be back Monday.
Bogie

Last edited by oldbogie; 05-11-2013 at 10:49 AM. Reason: trade a couple letters around hear and there
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Old 05-11-2013, 02:48 PM
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So what you guys are saying is 200cc runners dont work on the street? These heads wont make power under 7000rpm? I guess I have to explain my goals again. I am trying to make a hot street car which basically means a car that is able to go to the track every once in a while and hold its own on the street. Im NOT trying to take FULL advantage of the flow of these heads. I know I will be leaving power on the table with stock bottom end, no NO2, etc. I kind of want to "tame" these heads if you will. I knew these were a serious set of heads when I bought them but to say they are useless on the street??? Techinspector I trust your advise, what are your thoughts if they check out good for cracks/warping?
Yes they will make power on the street. But a 170cc will make more torque an be stronger at lower rpm where you are going to spend most of your time. The 200cc will pull good where the smaller heads start to drop off but it is to late then. If you were running a 406 or bigger they would work better at the lower rpm. Of course they would still need more camshaft an all other good stuff that makes the car run harder.
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Old 05-11-2013, 08:46 PM
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tech/combination combination

Quote:
Originally Posted by 1badLemans View Post
So what you guys are saying is 200cc runners dont work on the street? These heads wont make power under 7000rpm? I guess I have to explain my goals again. I am trying to make a hot street car which basically means a car that is able to go to the track every once in a while and hold its own on the street. Im NOT trying to take FULL advantage of the flow of these heads. I know I will be leaving power on the table with stock bottom end, no NO2, etc. I kind of want to "tame" these heads if you will. I knew these were a serious set of heads when I bought them but to say they are useless on the street??? Techinspector I trust your advise, what are your thoughts if they check out good for cracks/warping?
If you want to build a 13 second turd,then use those heads with a stock short block.Those heads would make very good power if you give them the parts to match. You want to use a 14 second engine,bolt on 11 second heads and expect,,,,,what?
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Old 05-16-2013, 09:20 PM
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Ok guys so would these heads be better suited on a 383 or 400 sbc with hi compression pistons? What about a 350 with dome pistons?
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Old 05-17-2013, 02:13 PM
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Quote:
Originally Posted by 1badLemans View Post
So what you guys are saying is 200cc runners dont work on the street? These heads wont make power under 7000rpm? Techinspector I trust your advise, what are your thoughts if they check out good for cracks/warping?
I have to go along with the other posters on this thread, too much head for a street 350. Should work great on a street 400 though, where you can keep charge velocity up and cylinder packing as a result.... at a lower rpm.
As I always say, combination, combination, combination.

Domed pistons would have little to do with overcoming a lazy intake tract. Matter of fact, the dome would probably be in the way of the fire front as the plug fires and would detract from lighting off the whole mix.

No matter the application, a flat-top piston will work better than any other design in my opinion. You just have to adjust the combustion chamber volume to get the right static compression ratio, then adjust the piston deck height with the head gasket thickness to arrive at the proper squish.

Last edited by techinspector1; 05-17-2013 at 02:20 PM.
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