Stock HP Exhaust Manifolds: Can They Make High HP / TQ?

[Road_Runner]

I know headers have always been one of the first things hot rodders have done to boost performance, but for those of us interested in stock appearing cars can motors and specifically stroker motors still be built without the manifolds being a huge restriction?  I'm interested in either a 318 or 340 stroker for the Barracuda and probably a 440 six pack stroked to 528 for the Roadrunner.  Does it even make sense to go with aftermarket heads, stroker kit, etc. if I don't go with headers?  Does anyone have examples of engines with stock exhaust manifolds making big HP/TQ numbers?  I know I've read that longer exhaust duration camshafts are a help but just trying to get some feedback if this even makes sense as a goal.

Thanks in advance, Jim

[burdar]

Cars that race in the FAST series have to run the factory manifolds.  The fastest car is in the 9's.  There are some SB cars in the 11's I think.  It can be done.

[Road_Runner]

Cars that race in the FAST series have to run the factory manifolds.  The fastest car is in the 9's.  There are some SB cars in the 11's I think.  It can be done.

Wow, that's a great example of even more performance than what I'm shooting for!  Now I wonder what's their secret?....Anybody know?

Later, Jim

[HP2]

They extrude hone the manifolds. A very costly process for the resulting gain, which is why it is so much more economical to go headers on a more practical build. How much power are the giving up to conform to the rules, 40, 60, 100, I don't know. FAST engines are pretty built and probalby have as much R&D in them as Stock Eliminator  mills.

[Road_Runner]

They extrude hone the manifolds. A very costly process for the resulting gain, which is why it is so much more economical to go headers on a more practical build. How much power are the giving up to conform to the rules, 40, 60, 100, I don't know. FAST engines are pretty built and probalby have as much R&D in them as Stock Eliminator  mills.

I read an article about extrude honing several years ago.  Seems like the shop that did it was in the Northeast somewhere, maybe New York state?  For the Barracuda I probably wouldn't go that far, Roadrunner maybe.  I was thinking more of a list of readily available parts that would comprise a strong street motor that still looked stock on the outside.  Racing fast not as important, but would be nice to get as close as reasonably possible without spending a fortune.  I would love to hear what others have gotten using stock manifolds and what other parts did or didn't work with them.

Later, Jim

[burdar]

Extrude honing is very expensive.  There are NO gains on a street car.  The FAST cars are hindered by the factory componants and need to look for 1 or 2hp where ever they can get it.   

[Road_Runner]

Extrude honing is very expensive.  There are NO gains on a street car.  The FAST cars are hindered by the factory componants and need to look for 1 or 2hp where ever they can get it.

I understand.  The best that I can recall the article mentioned a slight increase over stock of maybe 5-10 HP whereas a good set of headers are probably worth 40-50 HP or more especially on a high rpm motor.  I was just curious if others had tried successfully to build the kind of stock looking motor I described and what the specifics of their build was. 

Later, Jim

[cudabob496]

In general, the more stock an engine is, the less power it makes. Don't think you can get the 20 to 40 hp advantage of headers,
from stock or near stock exhaust manifolds. You could get the headers ceramic coated in black, so they would not stand out as much,
to keep your near stock appearance.  Maybe TTI has some suggestions?

[Chryco Psycho]

I have built a number of engines this way using the 512 stroker kits & stock HP manifolds & also small blocks for customer wanting  the stock look  , most of the power would be trimmed at higher RPM but the strokers make a ton of low & mid range torque & still run very fast with manifolds . I am alway careful porting , I raise the roof of the ports a little & wident the ports massively in the heads & then port out any restrictive area in the manifolds making the manifold larger than the ports for anti reversion , it seem to work well .

[Road_Runner]

I have built a number of engines this way using the 512 stroker kits & stock HP manifolds & also small blocks for customer wanting  the stock look  , most of the power would be trimmed at higher RPM but the strokers make a ton of low & mid range torque & still run very fast with manifolds . I am alway careful porting , I raise the roof of the ports a little & wident the ports massively in the heads & then port out any restrictive area in the manifolds making the manifold larger than the ports for anti reversion , it seem to work well .

When I get closer to pulling the trigger on either of these builds I'd like to pick your brain if you have the time.  I'm not totally against headers on the Roadrunner, but more & more I really want to use manifolds on the Barracuda's small block.  If I can still reach my HP/TQ goals of around 400 for both.  I'm thinking more like 500-550 HP & TQ for the Roadrunner's 512.

Thanks, Jim

[Chryco Psycho]

Brain  
Sure if you can find it !!

[Road_Runner]

Brain  
Sure if you can find it !!

Hey, I resemble that remark more & more these days!   

Thanks again, Jim

[Gumby]

Buy Andy F's book, " How To Build Big Block Mopars ". It is fantastic. He has tested many different combinations and outlines them all. He got close to 600 HP on a stroker 400 with stock HP manifolds. It can be done. Surprisingly enough, a big cam hurt performance. I looked into extrude hone. It is approx. $100 per cylinder. I have some HP exhaust manifolds that I bought from year One years ago. They were on sale and cheap. I don't know what they charge now. Mine came with a heat riser and all bolts. Gaskets, etc. They are nice. $400.00 bux years ago. Andy's book covers everything you could possibly want to know. He is up to date. He covers induction, exhaust, headers, ignition, rocker arms, bottom end  - everything. High end, low end. Everything. It is very thorough. WELL worth the money. Lot's of pictures. He has tested quite possibly every combination that you could imagine, and has dyno results to back them up. I got my copy off Amazon. I hate headers. I will not run them. TTI, the header company sells down pipes for stock exhaust manifolds to hook into yours (or theirs) exhaust system dirt cheap. Look them up. You CAN get a streetable big block high horsepower engine with stock  HiPo exhaust to deliver without all the headaches of headers. The information is out there. Good Luck,

[cudabob496]

bought it!

http://www.ebay.com/itm/How-to-Build-Max-Performance-Mopar-Big-Blocks-/140934770641?pt=US_Nonfiction_Book&hash=item20d05defd1

[Road_Runner]

Buy Andy F's book, " How To Build Big Block Mopars ". It is fantastic. He has tested many different combinations and outlines them all. He got close to 600 HP on a stroker 400 with stock HP manifolds. It can be done. Surprisingly enough, a big cam hurt performance. I looked into extrude hone. It is approx. $100 per cylinder. I have some HP exhaust manifolds that I bought from year One years ago. They were on sale and cheap. I don't know what they charge now. Mine came with a heat riser and all bolts. Gaskets, etc. They are nice. $400.00 bux years ago. Andy's book covers everything you could possibly want to know. He is up to date. He covers induction, exhaust, headers, ignition, rocker arms, bottom end  - everything. High end, low end. Everything. It is very thorough. WELL worth the money. Lot's of pictures. He has tested quite possibly every combination that you could imagine, and has dyno results to back them up. I got my copy off Amazon. I hate headers. I will not run them. TTI, the header company sells down pipes for stock exhaust manifolds to hook into yours (or theirs) exhaust system dirt cheap. Look them up. You CAN get a streetable big block high horsepower engine with stock  HiPo exhaust to deliver without all the headaches of headers. The information is out there. Good Luck,

Thanks for the heads-up.  I have several engine building books but not that one so I will pick it up.  I don't hate headers per se, its just that I like the less rattley & deeper sound manifolds get plus if they're right they are 100% zero maintenance.

Later, Jim