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The two intakes I know will fit are the CHI 3V single plane air gap
and the Scott Cook low rise dual plane (externally very similar looking
to a Ford dual plane). I'm running a 351C dyno project with Dave
McLain and we've flow bench and dyno tested the CHI 3V and Pro Comp
heads, along with unported iron 4V heads. We still have a bunch of
heads to test but I've posted some results below that may be of
interest. The short block in the tests below was a simple
street 351C with flat top TRW forged pistons and a mild hydraulic
roller cam with specs of:

228/232 degrees at 0.050" lift (280/284 at 0.006"), 0.588"/0.588" lift,
107 LSA, 68 degrees overlap, installed in the engine on a 104 intake
centerline.

Later we'll be testing 393C and 408C short blocks. Even on the relatively
mild 351C street engine, the CHI heads were worth nearly 50 HP (48.5 HP at
6000 RPM to be exact) through the mufflers in back-to-back tests compared
to the Pro Comp heads.

I found it interesting that the CHI single plane intake gave up nothing
to the dual plane anywhere in the RPM band tested while picking up the
expected 20 HP on the top end. I'm an aerospace engineer with an aerodynamics
background and the CHI plenum is designed the way I've always thought a
plenum should be with blunt rounded edges. Subsonic flow responds best
to blunt rounded edges (think of the rounded nose and thick wings of a
Boeing 747 aircraft) while supersonic flow prefers thin sharp edges
(think of the pointy nose and thin wings of a Concorde supersonic
transport). Many 351 Cleveland single plane intakes have relatively sharp
dividers between the ports. I remember discussing the CHI single plane
intake with Jon Kaase. He said he spent a lot of time modifying a Yates
single plane NASCAR intake to match the CHI heads thinking it would give
him an edge in the Engine Masters Competition, only to find the CHI single
plane out-performed it out of the box. Be aware the CHI intake is very tall.
Given the Scott Cook low rise dual plane only gave up 20 HP or so to the
CHI, I think it did very well.

We've also test unported iron 4V closed chamber Cleveland heads (ported heads
will also be tested at a later date). With a Strip Dominator intake on the
4V heads, they bested the Pro Comps by around 30 HP but wer down around 20 HP
to the Pro Comps.

Dan Jones

6500 rpm test 4V Boss
Gave the engine more timing still, 37 degrees max. Same as previous pull with
37 degrees timing. Took engine to 6500rpm just to see and it runs the same as
at 5700rpm Good solid pull but engine is done at about 6200 just like before.

RPM HP Torque (ft-lb)
4000 299.5 388.8
4100 302.3 388.5
4200 310.8 388.4
4300 321.4 392.8
4400 328.4 392.3
4500 338.3 394.7
4600 349.0 398.4
4700 359.3 401.5
4800 367.8 402.5
4900 375.3 402.2
5000 382.1 401.0
5100 388.4 400.1
5200 396.8 400.6
5300 403.1 399.7
5400 407.5 396.2
5500 413.4 394.7
5600 415.5 390.1
5700 409.6 377.6
5800 406.0 367.6
5900 407.6 362.5
6000 406.7 356.3
6100 410.0 352.8
6200 415.2 352.1
6300 417.0 347.6
6400 418.7 343.8

CHI Heads with CHI single plane intake (4150 flange) and HVH spacer.
Best combination for CHI heads

RPM HP Torque

3200 222.0 359.8
3300 222.4 354.8
3400 230.3 356.0
3500 240.0 360.3
3600 249.9 364.9
3700 262.0 371.8
3800 277.0 382.4
3900 293.2 394.4
4000 302.8 397.8
4100 315.7 404.3
4200 329.8 412.1
4300 341.1 416.5
4400 349.7 417.9
4500 357.7 417.5
4600 369.2 421.2
4700 377.5 422.1
4800 386.2 422.4
4900 394.5 422.9
5000 401.7 422.1
5100 411.6 423.7
5200 420.5 424.8
5300 428.3 424.6
5400 436.2 423.4
5500 434.2 415.1
5600 431.2 404.6
5700 430.8 396.8
5800 432.4 391.9
5900 433.2 385.7
6000 435.6 381.5
6100 435.1 374.4

The numbers posted here are corrected to Std Day atmospheric conditions and
through a full exhaust (some mufflers lost 50 HP!). With a bit more timing
I think the peak was just under 450 HP but we had some detonation at low
RPM. Rather than re-curving the distributor we pulled back on the total
timing. A later test with a shorter rocker 1.65:1 ratio on the exhaust
picked up torque (as much as 13 ft-lbs at lower RPM) but made about the same
peak HP.

On the same night as the Pro Comp tests, here's what the CHI 3V heads and
intake pulled. At 6000 RPM, the Pro Comps were down 48.5 HP.

RPM HP Torque
3200 219.2 359.1
3300 218.7 348.6
3400 225.8 348.7
3500 236.4 354.6
3600 247.4 361.1
3700 259.5 368.2
3800 273.9 378.1
3900 287.4 386.8
4000 298.6 392.3
4100 309.2 396.4
4200 320.1 400.4
4300 332.0 405.4
4400 343.8 410.3
4500 355.3 414.6
4600 367.3 419.1
4700 374.7 418.2
4800 375.8 411.8
4900 382.8 410.1
5000 392.1 412.0
5100 406.5 417.7
5200 410.3 414.9
5300 419.7 415.8
5400 427.5 415.5
5500 432.8 412.9
5600 429.1 403.0
5700 425.7 392.4
5800 421.7 381.9
5900 423.0 376.4
6000 428.5 375.3
6100 428.3 368.3


Pro Comp Heads with CHI single plane intake (4150 flange) and HVH spacer.
Best combination for Pro Comp heads

RPM HP Torque
3000 198.8 347.2
3100 202.8 343.7
3200 212.2 348.3
3300 218.6 348.1
3400 224.5 347.1
3500 234.2 351.3
3600 247.4 360.3
3700 258.7 367.5
3800 268.1 370.5
3900 279.4 376.0
4000 291.7 382.9
4100 303.6 388.8
4200 315.7 394.6
4300 328.4 401.0
4400 334.2 399.4
4500 339.2 396.1
4600 346.6 395.6
4700 361.1 402.5
4800 368.6 403.5
4900 374.7 401.5
5000 376.8 396.2
5100 379.9 391.1
5200 385.1 388.8
5300 388.9 385.4
5400 393.4 382.5
5500 396.7 378.6
5600 396.3 371.6
5700 391.2 360.7
5800 387.7 351.0
5900 384.1 342.2
6000 380.0 332.5
6100 384.5 330.6


CHI 3V Heads and Scott Cook Dual Plane Intake
1 inch open spacer and 34 degrees timing.

RPM HP Torque
2500 151.3 319.2
2600 157.1 317.3
2700 165.2 321.5
2800 173.9 326.4
2900 184.2 333.3
3000 193.6 338.8
3100 201.8 342.0
3200 209.3 343.5
3300 219.6 349.7
3400 233.0 359.8
3500 245.2 367.9
3600 257.5 375.5
3700 271.6 385.2
3800 285.5 394.6
3900 299.3 402.9
4000 312.9 410.6
4100 325.5 417.0
4200 334.0 418.1
4300 341.3 416.9
4400 350.7 418.3
4500 359.8 419.8
4600 369.8 421.7
4700 378.3 423.6
4800 383.0 419.4
4900 388.3 416.1
5000 394.6 414.4
5100 401.8 413.5
5200 408.7 412.9
5300 415.4 411.6
5400 416.7 405.1
5500 416.7 398.3
5600 415.3 389.2
5700 414.1 381.9
5800 414.4 375.3
5900 419.0 372.9
6000 418.8 366.7
 

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I agree, bless Dan Jones. I have been following that dyno test for awhile now after seeing it over on Network54. That dyno test is the reason I chose 4V iron heads and have put off the CHI's. I paid $675 for a "built" set and have been very happy. I will still purchase the CHI's but not yet. Keep up the great work Dan Jones and Dave McLain as well.
 

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568 hp on an engine dyno with a 230 cc cfm port head and 400 cubes...

that is plain disappointing.
So ryans88, you want to make bs comments and focus on the "400 cube" aspect... If this engine was a sbf w or c 400" stroker then I might see your point but the FACT is this is basicly a Stock 400M" (9.5:1 comp Stock Block, Crank, Rod... boat anchor) short block which has a so much diffrent bigger/heavyer rotating assembly than a 400cube W or C. As 56f100 mentioned that 400M engine is not really impressive at all... nothing special. So 568 HP from basicly a stock POS 400M 9.5:1 compression short block boat anchor seems VERY DECENT to me... and hey they even did it with out a pair of $3000/$4000 dollar heads... sound like a decent bang for the buck to me.

Never rule out the 4V iron head. I asked Dr J's about the 4V heads early last year because I was very impressed with those flow numbers. One thing that they do is replace the 2.19 intake valve with a 2.25 intake valve. I personally am a huge fan of the original 4V head. I don't think ppl are just throwing them in the dumpster either. Especially the 4V close chamber head. They do turn up from time to time very economically though, compared to aluminum heads. It is common knowledge that the exhaust port is a little weak but can be fixed. This is the reply I got from Dr J's:... Eddie,

Thanks for the email. The 2.25 valve fixes a lot of the problems with the heads. With a 2.19 the low lift flow will go down quite a bit, because of the factory under cuts in the valve set. The larger valve allows us to clean all of that up. If you have more questions please feel free to ask.

Competition Cylinder Head porting Both heads $795.00
* gasket match
* Blend blows
* Stream line guide bosses on Intake & Exhaust
* Increase Push rod pinch
* fully radius short turn intake and exhaust
* flow testing before and after

Anti-Reversion Valve Job $250
5 angle anti reversion intake valve seat form
Fully radius exhaust seat form
Chambers swept to increase radial clearance on the valve
30 degree back cuts on intake and exhaust valves
radius top on exhaust valves

Bottom line is this. For about $1100 you can have a 4V iron head that flows 355 cfm intake and 225 cfm exhaust at .700 inch lift. 4V iron heads turn up on eBay and craigslist often for $400-$500. Sometimes cheaper. The only disadvantage is they are in iron and not aluminum. Also it is very annoying to Chevy guys when they get beat by a 40 year old stock headed small block. Ask me how I know.... Eddie
Great post, glad finaly others are comparing the good old factory american 4V heads to all this offshore aluminum stuff... to me THIS! is what its all about. Will repeat it again. I can put together a killer set of american highport 4V heads for 2 grand or less (CND) so I would NEVER spend more than this on any old tech 2 valve aluminum head.

Mr Jones, always enjoy reading your tech. I have a question, these PC heads you tested, were they a cnc head or an as cast head?. Just wondering if they were a cnc version, what company they came from?.
 

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All three sets of heads (CHI 3V, iron 4V, Pro Comp) were unported and treated only to a valve job. I have some Ford Motorsport high ports (A3, C302, C302B) to test, along with ported 4V's and ported Aussie 2V's. Just received a set of CHI 4V's to run on the 408C.

Dan Jones
 

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Learning that the PC heads are casted with extra meat for porting, I can see how they could be at a disadvantage to some other heads when used as cast and not ported. Especially if your looking for big hp, imo unless a person wants/needs castings to get into some type of porting I would recommend just buying the finished $1500 cnc versions of these PC heads.
 

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> Learning now that the PC heads are casted with extra meat for porting,
> I can see how they could be at a disadvantage to some other heads when
> used as cast and not ported.

The disadvantage has nothing to do with the thickness of the casting in
the port area. The Pro Comps are no different in that respect than the
CHI's or other aluminum Cleveland heads I've had in the shop. The problem
is the valve seats are sunk which ruins the short side radius. It's not
clear that porting would help. You can port the heads and maybe pick up
high lift flow but low and mid lift may still suffer. The CNC heads have
substantially larger ports so velocity suffers. A friend has a set of
Pro Comps and is working with a pro head porter to see if they can come
up with a fix. We'll see.

> IMO unless a person wants/needs castings to get into some type of porting
> I would recomend just buying the finished $1500 cnc versions of these PC heads.

After testing the Pro Comps, I'd recommend starting with a better head.
Making up the 50 HP deficit we saw on the dyno would take a bunch of
work to the heads.

Dan Jones
 

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The disadvantage has nothing to do with the thickness of the casting in
the port area. The Pro Comps are no different in that respect than the
CHI's or other aluminum Cleveland heads I've had in the shop. The problem
is the valve seats are sunk which ruins the short side radius. It's not
clear that porting would help. You can port the heads and maybe pick up
high lift flow but low and mid lift may still suffer. The CNC heads have
substantially larger ports so velocity suffers. A friend has a set of
Pro Comps and is working with a pro head porter to see if they can come
up with a fix. We'll see. Dan Jones


I guess it will be interesting to see what your/the head porter comes up with and if he can get simular results to what DR.J's, FPS, SOM and others have gotten. I cant help but wonder about some guys complaining about sunk seats, as HD eng head builders also sink the valve seat a bit to gain more clearance with out hurting anything. Can this also not be helpfull when installing a 2.25" int valve in even factory 4V heads?. I dont agree with you about velocity suffering with cnc ported heads as factors as engine CI would change this. Some out there also say factory 4V heads int ports are no good/to big and still some others have proved that wrong. I guess guys/girls will have to factor in for them selfs if a set of $1500 CNC finished heads is worth it or not, also what if any hp deficit the CNC finished heads have compared to others.
 

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> Learning now that the PC heads are casted with extra meat for porting,
> I can see how they could be at a disadvantage to some other heads when
> used as cast and not ported.

The disadvantage has nothing to do with the thickness of the casting in
the port area. The Pro Comps are no different in that respect than the
CHI's or other aluminum Cleveland heads I've had in the shop. The problem
is the valve seats are sunk which ruins the short side radius. It's not
clear that porting would help. You can port the heads and maybe pick up
high lift flow but low and mid lift may still suffer. The CNC heads have
substantially larger ports so velocity suffers. A friend has a set of
Pro Comps and is working with a pro head porter to see if they can come
up with a fix. We'll see.

> IMO unless a person wants/needs castings to get into some type of porting
> I would recomend just buying the finished $1500 cnc versions of these PC heads.

After testing the Pro Comps, I'd recommend starting with a better head.
Making up the 50 HP deficit we saw on the dyno would take a bunch of
work to the heads.

Dan Jones
Haha, I tried to tell Boss that like a year ago... I think the guy just doesn't want to listen to any reason. Hardcore procomp nutswinger.
 

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The as cast CHI heads out flow any CNC PC ported head. That is fact. You can't CNC port your way out of valve sunk too far in the chamber. They will never have good low and mid lift numbers.

You simply do not need to CNC port the CHI heads unless you are looking for more than 350 cfm.
Oh hey look it was even in this same thread, almost a year ago exactly...
 

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spend the extra couple hundred dollars and buy parts that are made correctly or cheap out and then spend the extra money later trying to correct someone else's poor engineering...

that is what it comes down to really.
 

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Haha, I tried to tell Boss that like a year ago... I think the guy just doesn't want to listen to any reason. Hardcore procomp nutswinger.
AH. still hurling insults... the sign of a feeble mind.... what the hell are you still ranting about anyway...

 

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Hey thanks again!!! ryans88gt, I guess I am the only one on the planet earth that has had no problems buying junk parts lol... hey I got a brand new pack of NAPA razor blades I could send you (no charge) that are made in america... well actually they come from Taiwan but same poo anyway. The FACT IS.. that there are LOTS of pc products allready out there, apparantly from what I seen on the net pc does 500.000+ in sales a year in north america alone so posts as yours are really great!... I get a good laugh out of some people (mostly the chi bretherin?) Ranting away about "China made junk"... Here in CND we dont have the same hang ups some of you chi fan boys do as since I was a kid CND has had TONS! lol of china/taiwan products, heck some of my paychecks from my work come from there lol as the shop has been building stuff for china and japan lol...

...anyway here are some more pics of my china? OR! maybe croation? junk 280cc Avenger heads... that are machined, assembled and sold in america... by probably a mexican... that got sold to a canadian that was originaly from europe... thats thinking about moving to japan lol:)
I tried telling you about the valve seat being sunk in the PC heads and this is the response I got...


If you are insulted by the truth, I'm sorry
Here's a cookie...let's be friends

 

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I tried telling you about the valve seat being sunk in the PC heads and this is the response I got...


If you are insulted by the truth, I'm sorry
Here's a cookie...let's be friends


LOL, AND... for frick sakes... I tryed to tell you... I DONT CARE, the fact is I NEED to have the seat sunk a bit for what I want these for... SO...



As far as your or anyone elses version of the truth goes... I DONT NEED IT...

I got my own version...



So why dont you stop loosing sleep over what I spend MY money on and stop trying to piss on my rug.... Man.
 

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LOL, AND... for frick sakes... I tryed to tell you... I DONT CARE, the fact is I NEED to have the seat sunk a bit for what I want these for... SO...

As far as your or anyone elses version of the truth goes... I DONT NEED IT...

I got my own version...

So why dont you stop loosing sleep over what I spend MY money on and stop trying to piss on my rug.... Man.
Hahaha...loosing sleep over it...no. Stopping the spread of ignorance...if I can.

The PC heads are just not a good deal when a properly prepared head can be had for a tiny bit more. That's my story and I'm sticking to it.
 

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Trying to save the world EH LOL. You really need to stop smoking pig shat like the 351C.unt forum owner/s and buy some good canadian weed.



never seen so much crying bs propaganda on some of these so called "auto forums" from the >internet parts peddlers/vendor TROLLS< and there islamist fanboys trying to keep the status quo going with there own bs agendas shepherding/peddling/pushing over priced parts on internet forums lol. Bar None, auto forums are the worst for this internet forum vendor/parts peddler sales bs. its hilarious how some of the "china junk" trolls push the offshore import scm/chi/afd crap so hard/much online as its NOT! even American lol, hell the import Avenger heads are More American than the over priced offshore import scm/chi/afd china cast stuff is :rofl:

The sm/pc bashing/propaganda by some of the islamist fanboys/internet parts peddlers on some of these so called auto forums is really pathetic as its a FACT guys have been making 1000+HP with SM/PC products, heads, blocks, cranks, rods ... Speedmaster/Procomp ...
 

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For those interested in these heads, I just did a quick comparo to the short side radius of my pc/av heads to my factory 4V heads with some soldering wire. Well the short side of the pc looks good to me, hell its even better than the short turn in my 4V cannonball heads...




obviously the pc/av one is on bottom, the hook on the end is the seat area with valves pushing on solder and cut at the valve edge.



:salute::salute::salute:
 

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I dont think thats a perfect short turn but its better than the stock one.needs to be a little straighter above the valve job before it flattens out at the crest of the short turn.
 

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Well... I dont agree with you, I think its a excellent short turn. Fact is bad or not the even the stock 4V head casting with its short turn can make 700+ na hp with some work. Also I dont think it is written in stone anywere on the planet that only one kind of short turn works for all...

check paragraph #8

http://www.diyporting.com/E7p3.html

Also just to quote Darin Morgan... "A good port design will flow a lot of air. The bad news is, a bad port design can flow just as much if not more air!"

http://www.darinmorgan.com/
 

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I dont doubt it can still make power and like i said i think that short turn is better than the stock head.

some stuff that i have done from years ago ran suprisingly well without great short turns,just sayin...

i have never seen one of these procomps so i cant say to much one way or the other.
 
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