An exhaust system has the potential to be much more than just a way to move exhaust from the head to the tail pipe.
I don't think I would bolt on an excellent flowing head only to choke it with a sub par exhaust system.
It's not all about max hp. It's about tourque through out the rpm range. The max flow volume of exhaust occurs well before max rpm or Max hp.
Do some research on exhaust systems and cast manifolds vs headers.
Here is an article to get you started.
http://www.moparmusclemagazine.com/t...o_numbers.html

If both heads are aluminum, I'd go with the the profiler's for your what it sounds like you want. 64 cc should work if it has a piston with decent quench pad.

 

Times five. If going afr which I would, I can't say anything bad about profiler as I've never used them. Hear good things about them hear and there, but I own a set of afrs and am thoroughly pleased with them. If you stay with cast iron manifolds, both heads would do better with long tube headers.

 

Go with the AFR 65cc heads. Being that they are aluminum and not iron 10:1 is not an issue. Even with iron heads 10:1 is ok if tuned correctly. Also what altitude do you live at. Higher than sea level needs more compression. If you want to run cast iron manifolds go with a smaller cam and smaller intake with less compression. Its all a system and all needs to match.
You did not mention the transmission, TQ Converter if and auto and gear ratio. All important info to evaluate your parts choice.
I have owned my 79 for 15 years and have used factory manifolds, 2 1/2 rams horns, shortly and long tube headers. I word recommend the long tube headers. Just make sure you get a set with thick flanges and use good gaskets and you will not have a problem. With the hooker shortly they melted the engine mounts, caused starter problems and melted spark plug boots. The Hooker long tube have been on for 6 or 7 years and I have no problems with them. That's with stock steering and now with borgison. Also the long tube headers will give you more low rpm TQ. As far as heat I can not tell any difference in my car with any of the set ups. I also did a build for a friend with hooker long tube headers and no issues on a 1980.
I also have a 1971 C10 with a 350 and hooker long tube headers. I have been using it as a daily driver for 20 years and have driven about 350,000 miles with the headers and no problems at all, no burned plug wires and no leaking gaskets. I drive it 80 miles a day.
I once bought a 83 Z28 with cheep headers and they went to the trash the first week because of the thin flanges.

Here is a link to my current rebuild that I am on. You can see the clearance with the headers. http://forums.corvetteforum.com/c3-g...ld-thread.html
My car has the 180 AFR and the XE 276 HR, good cam, just a bit bigger than yours but had last ran it with Sportmen II heads and made 335 HP at the wheels.

 

Also can you weld, if so an exhaust system is really ease to fab up.

 

Another vote for AFR. and headers. An engine is an air pump. Air in, air out. Anywhere you have a restriction reduces power. This is why proper matching of components throughout creates a greater than expected result and one mismatched component often creates disappointment Your good through the entire system until you try to eliminate exhaust gases. It is the same theory as running a restrictor plate in Nascar limiting possible power on certain tracks. All the improvements your making to make more power are reduced or eliminated by your version of your restrictor plate. Your likely giving up close to 100 HP with your build specs if your running ramhorns and 2" factory type exhaust compared to full flow headers and free flowing 2/1/2" exhaust.

 

I appreciate the comments, but to suggest that headers on this mild build would produce 100 HP is quite hard to believe. I have never read or heard anybody make such a claim.

 

I'll take a last swing at this, although it seems your mind is made up.

On a relatively mild 350 making around 1 HP/CID the right headers are worth potentially 25-30 HP and about 30-35 peak torque. I've personally seen it on the chassis dyno. The torque curve is fatter throughout the RPM range - not "15 HP at 6,000 RPM" - and this is really what matters on the street.

On your engine that would normally make 400+ at the crank, you can expect slightly less than double those numbers or better. So 100 HP is in the ballpark of the power you'll lose. Approaching 1.2 HP/CID is not a "mild" build. But I'd put $50 that you'll fail to get 1 HP/CID at the crank with iron manifolds.

It's your build of course, but you asked for opinions. I'd make a few small tweaks here and there, but if you're going to run iron manifolds or shorty headers don't bother spending money on decent heads. The guy with some half-assed ported stockers is going to beat you at the stoplight.

There's no reason to compare some garbage header with the quality items out there. Quality headers, good gaskets, the right fasteners, etc. aren't going to give you any trouble. They're not maintenance free, and you'll want to check the bolts when you change the oil. But nowhere near what you report anecdotally.

Don't choke an otherwise excellent build because of bad things you've heard about crappy headers.

 

Yes, I'm pretty happy with the system. 2 1/2" aluminized exhaust pipe, crossover tube, (although it's pretty far back) Magnaflow mufflers, ceramic coated block-hugger headers. I'm thinking about full-length headers someday, unless I decide to go with sidepipes. I think the block-huggers will work well with the factory-style sidepipes, as far as routing the exhaust goes. Either way, I dumped those heavy, restrictive stock manifolds like a bad habit, and I haven't looked back.

It's hard to really find much data concerning the block-hugger design, but the conventional wisdom says that they just about in-between a full-length header and the stock exhaust manifold, as far as power production goes. They allow the exhaust gasses to escape more easily than a manifold, but you don't get the benefit of the "suction" effect that a well-designed full-length header has. In short, they are not as good as a full-length header, but better than a stock, cast iron manifold. Easy to install, too. Mine go on and come off from the top of the engine bay, no need to crawl around under the car. Also, it allows an O2 sensor to be placed relatively close to the head, which is good, the closer the better. The Corvette Central version uses a ball-and-socket type connection for the header to the exhaust pipe, for a very secure, leak free connection. Overall, it's a pretty well-designed system, which can be easily converted over to full-length headers, if the desire ever comes up.

Edit: I did a little number crunching, and according to my DCR calculator, the AFR 180 heads, with the 65cc chambers, will give you a Dynamic Compression Ratio of 8.33:1, which is getting pretty close to borderline with pump premium. Be careful setting your timing.
Scott

 

One other think you have to consider is that there are no 2.5 inch outlet ram horn manifolds used since the early 60's. Even later HP engines had 2 in outlet manifolds that dumped into pipes that expanded to 2.5 inches after the connection at the engine.

That being said, I respect your choice and I like the look of stock manifolds with the wires laced through the looms underneath. If someone made a factory-type cast manifold with larger outlets I would be temped to use them myself.

Hooker does (or used to) make the pipes to attach headers to the stock dual-type pipes. My 77 has them as installed by the original owner. They seem to fit well and the pipes fit in the crossmember openings perfectly.

 

You have now. with Billa. your looking at a 400-420+ Hp build with the right exhaust and well under 350 hp with stock 2" exhaust. It is like sticking a potato in your exhaust pipe. The big point missed is the huge difference in torque you will see throughout the RPM range. That power loss is not just at peak but from off idle to redline, increasing as RPM increases.
EDIT: Just noticed you do have upgrade 2 1/2"exhaust but the ramhorns are still killing it. At least 50 HP and torque with your specs and again power loss though the entire RPM range with loss increasing with RPM.

 

If you don't use headers go with a smaller cam and the smaller roller will not be worth the money as far as power, , maybe a head such as the World products S/R TQ and a performer intake, not the RPM. A lot less money and will only be slightly less powerful than what your talking about with out the headers. This way you have a matching system.

On my last post I missed the transmission and gear, sorry.

 

Personally, I would probably run a smoother cam with stock manifolds. The factory 350/350 horsepower cam is really hard to beat with stock exhaust. It gives a good idle with a slight lope. L-82's used the same cam. Not sure how the cam specs translate over to a similar roller cam but it makes for a nice package with big valve heads and decent compression. Torquey and docile around town but has a nice kick when you hit passing gear on the road.

 

50 RWHP drop is huge!

 

And porting them is a complete waste to before anyone mentions it.

 

Shorty headers provide no scavenging effect and little or no HP/TQ increase - they're not in-between manifolds and headers...they're pretty manifolds Sometimes they're the only choice on a street rod or other swap build...but don't expect any power.

Under-camming a big head is the surest way to end up with a pig in terms of power and driveability. I've seen it many, MANY times - if you're not going to cam to the capabilities of the head...then save yourself some money and buy a head matched to the lesser cam. "I'm gonna swap it later" often never happens.

 

 

Take a look at the article I referenced.
http://www.moparmusclemagazine.com/t...o_numbers.html

Notice at what RPM the torque maxed with the stock manifolds vs shorty vs long tube manifold 4200 RPM;
Stock = 469
Shorty's= 503
long tube= 537

So the shorty's do show some improvement over stock and it does appear to be half way in between stock and the long tubes in their example.
But stock vs long tube is 68 lb/ft of torque @ 4200 rpm. Also a difference of 70 HP at 5400 rpm. both of these RPM's achievable on a mild to medium type build. That's almost 17% on the build illustrated.

 

Ya way to much chaos , it is a shame the stock ZZ4 was not bought. For everything you have posted and your goals that set up was designed for you exactly as if you had a tailor make you a suit.

But reality ,,ok I am back to it. Grab ZZ4 specs sheet.. And match it with or with out GM parts. You will have a very solid fun motor built to run many many miles and years to come. No sense complicating the build with your goals in mind.

 

[QUOTE=CaseyJones;1585789986]One other think you have to consider is that there are no 2.5 inch outlet ram horn manifolds used since the early 60's. Even later HP engines had 2 in outlet manifolds that dumped into pipes that expanded to 2.5 inches after the connection at the engine.

That being said, I respect your choice and I like the look of stock manifolds with the wires laced through the looms underneath. If someone made a factory-type cast manifold with larger outlets I would be temped to use them myself.

I have purchased a set of very nice original GM 2-1/2 inch outlet rams horns. The Magnaflow 2-1/2 inch system with the X will bolt right up to these, so there will be a complete 2-1/2 exhaust path from the manifold outlet to the tailpipe, no step downs.

 

Here is one of the problems. I could have made a choice early on to buy down, like you suggest. But I bought many of the components I did buy not for performance, but for quality and durability. I wanted roller rockers and a roller cam simple because it makes more sense to me to have a roller type interface, less friction, and no break in problems. I also don't have to panic about ZDDP loss in oil, etc.

So, that lead me to buy a 86-up engine block, in my case a ZZ4 shortblock. I also wanted the one piece rear main seal as a fix for typical two piece seal leaks. Having a four bolt main is icing on the cake.

I feel like I have a very solid reliable base for my engine. Now that I have done that, I can take advantage of that and build some performance. So, it just seems silly to bolt on low performance cast iron heads, and a weak cam. SO here is my question to you all suggesting headers.

Are you saying I will have less performance out of this engine with good heads like Profilers or AFR than I would if I put on World SR Torquers? Please answer yes or no.

Cause sometimes when I here about building a system that works together, you make is sound like if I install these 2-1/2 inch rams horn manifolds, I will actually lose performance by installing AFR heads rather than a weak set of heads. Do you really mean that?

By the way, the Profiler heads I am considering will be $1140 a set ASSEMBLED at my door. Yes, if I were to buy AFR heads I would be spending money, but other than going cast iron, I really can't buy an American made aluminum head for less money. If I were buy down in performance, I would have to spend more money on Brodix IK180 or Performer RPMs, all that cost more. Does that make sense?