So, in summary, no data to review, and no port velocity numbers. May be convincing to you, but not to anyone else.


You post in technical threads all the time. My point was that you are more aware than most participants that port velocity is a critical factor, and simple flow numbers are not the kind of data that, standing alone, supports a conclusion that one head is superior in performance even to a stock head. That's apparently been ignored in your reliance of this "secret" test to assert that JAM's head performs better than Cosworth (or Brand X), for that matter.

JAM says that it's Stage IV CNC cylinder head is "Not designed or intended for the street use but rather 1/4 or 1/8 mile passes only" -- basically only for all out drag motors. That's a very limited use, and has specific flow and velocity demands that would be very different than a head directed at street or road racing use. There might be more flow at the top end, but the area under the curve under 6500 may be darn near useless for any common set of mods. I'm sure you've seen or heard of heads that have this performance limitations in the real world.

I question every opinion that is made without backup data. You ask about questioning COSWORTH flow data. Cosworth's data is not automatically more believeable than JAMs, nor do they publish port velocity numbers -- that's why I said the heads needed to be tested on the car to get a comparison that would be useful to someone like the original poster looking for a performance head upgrade.

I don't know whether JAMs head would "give more HP" than Cosworth's head, Buschur's head, or Portflow's head. Apparently, neither do you. That was the question originally posed, although the poster did not provide specifics about whether he wanted a single use all out drag trailer car, or intended his question to mean a modded street car. I simply pointed out that you posted no data to support your confident conclusion of JAM's superiority in either use. You still haven't, and after several posts worth of opportunity to back up your opinion, there's still no data that would allow someone to form an independent analysis of the performance characteristics of the JAM head.

Since you have no data you are willing or able to share with us, I'll just accept your opinion as that -- another "JAM FTW" with no more weight than the next person.

 

Thank you for that post Vr4, exactly what I wanted to say I just didnt have the motivation

Scorke

 

No, you are just too darn lazy to type, thats all...

 

I agree that head porting is a complex subject despite how heads are generally marketed (more flow = better). The ideal head port size/shape depends on how the car's going to be used, the cam profiles to be used, the size of the turbo, the displacement, etc. The head that's optimal for a road race car with a Green turbo, a stroker and S1 cams is surely going to be a lot different than the ideal head for a GT37R car running Jun 272s that never sees under 5K RPM.

 

That depends upon the intended use.


Not being posted in this particular forum does not necessarily constitute 'secret'.


The same thing is often said about large turbos. It's a matter of perspective.


I absolutely, wholeheartedly agree.


There are many, many things I don't know with absolute certainty. If I had to wait for peer reviewed scientific studies to be conducted on everything prior to making purchasing decisions, I'd have done little at this point, and I could toss out 95+% of the data reported in this forum. Being a research scientist, I know a little bit about that! However, since I am putting something together that isn't 'recommended for street use' (ahem), the outright flow potential at relevant lift ranges IS a primary factor. In fact, it's important enough that I've contracted one headflow comparison test on my own fairly recently. It wasn't the first, and it won't be the last. Such tests may not be absolutely scientific, but they work well enough to point me in the right direction. Tests conducted by others whom I know to be competent carry equal weight with me. If it isn't good enough for someone else, that's fine too.

 

COVR4, why don't you call JAM if you are interested in the details of the test that was conducted? 410-859-3269 Maybe they can provide you with some data?

 

Ted, on JAM's website, it only shows the CNC'd Heads being offered for the DSM's. Under the EVO Cylinder Heads, there is no mention of CNC'd heads. I'm not saying that you are wrong and that they don't offer it, Im just saying that's why I believed that JAM's EVO heads were hand ported. Thanks for clearing the air though, Ted!

~fred

 

My apologies, it is ME that requires correction with respect to the CNC question. I noted your statement about the website and called for clarification.

JAM CNC ports Gen I and II heads. The EVO heads remain hand-ported at this time. Why? Because JAM feels there still may be a tweak or two more left in them to be unearthed, and so long as they feel this is the case, they won't invest the $6k in developing the CNC program, which more or less finalizes everything.

 

Hmmm, cool. Good info, Ted. Thanks for that tidbit. Looking at, say, a 1st Gen DSM, I wonder how much more an equivalent "stage" CNC'd head makes on the DSM over one of their regular heads, both heads being the same "stage". That would be an interested test, but I doubt it will be ever carried out.

 

Having the ports cut with a CNC does not make a head flow better than a hand ported head. It simply allows the original hand ported head to be replicated with more precision, or in some cases, allows a different "finish" to be done that could not be done by hand (like the ridges on the Cosworth head, which would be difficult to do by hand).

The usual process of porting a head (after a basic casting cleanup) is to experiment in forming the port design by removing material, adding clay or epoxy and sanding or grinding to change the port shape and size, and flowing the head on a flow bench with the various changes you create in the ports. This is almost always done by hand.

After the person porting the head goes as far as they are interested in going, then if a CNC program is to be created, the shape of the ports are digitized with a CNC machining center using a digital probe, the "point cloud" data is then fed into a computer, and then into a CAD/CAM program to translate the design into the program that tells the computer how to cut the ports.

In contrast, porters who do the work by hand often make latex "plugs" of their ports, and use those as templates to do the next head, so they're not starting from scratch...

Actually cutting the ports typically requires a 5 axis CNC machine, long (and expensive) carbide tooling, hundreds of "passes" to shape each port, sometimes turning the head over to get into the port from both the intake end and the combustion chamber end, and in some cases, hand finishing after the head has been completed.

5 axis machines this size cost $100,000+ used, without tooling. That's why CNC heads are not that common, and why they cost a premium. They don't necessarily perform better than a hand ported head, but once you get the first one right, you can make it exactly that way 1000 times if you have customer demand for that many...

 

thats really gr8 info .

 

Wanted to clear up some bunk that's floating around in this thread. We do NOT CNC our Evo series cylinder heads, only the 1g and 2g 4G63 heads. Every Evo head is hand ported based on the customers plans for the car. Flow volume, as well as charachteristics such as velocity and swirl are evaluated. So NO, it's not all about CFM Heads are ported, tested, and it we're not happy it goes back into the porting room. Every head is tailored for each customer. If you want proof of how they work on the car and not just on the bench, fell free to contact anyone with one of our heads and you'll never find anyone that wasn't 100% satisfied with our product. Plenty of our strokers are in daily drive 500+ WHP cars, many running 10's and competing in rally, time attack and Autox. Far cry from the 12sec club.

As far as time invested in R&D, our experience goes back 30+ years. Our 4G63 specific experience spans 10+ years which includes the worlds FIRST 8 second DSM. No one else can say that.

 

That's useful information, direct from the vendor, and clears up some of the misinformation Ted B. and others have made trying to support your offerings.

I've not knocked your work or products in this thread. I've simply pointed out that without emperical data for comparison (whether it's pure flow, port velocity, HP, torque curves or anything else), the rest is just opinion.

There are a number of well respected DSM engine (and engine parts) builders that have been working with 4g63 motors for much longer than the 10+ years you mention. Magnus Motorsports, Buschur, RRE, AMS just to name a few. Does length of time matter? Probably, but not in any way that you could quantify. Magnus is building the engines and heads for the 4g63 powered 6 second car. AMS and Buschur have demonstrated 8 second Evo capability. There's plenty of very capable engineering demonstrated by all of these shops.

It's funny, though, that folks on this forum would compare technical capability between Cosworth and these companies, or, for that matter, with anyone more than a handful of companies in the world. Cosworth engineers and entirely manufactures their own racing engines, and consults for manufacturers in technical engineering exercises. Look on their webpage (www.cosworth.com) if you have any interest in the depth and breadth of their corporate capability.

I'd be wary of anyone who suggests that Cosworth would send out a new head with a crappy deck surface finish or full of shavings...

 

Why? You say you're not "knocking" our produts or services, but what you are doing is taking a shot at our credibility upon which you have no solid, factual basis.

We didn't publicize the information. Had it been our intention to bash another company, we would have brought it out into a public forum long ago. We don't play that game. Our work speaks for itself as evidenced by the positive feedback in this thread. Maybe it was a one time QC issue with Cosworth, who knows. Either way it is unacceptable for a company with their breadth and engineering expertise to let such a thing out the door.

 

Funny, I didn't see anyone in this thread contesting Cosworths technical capabilities. Sure, they manufacture some of their own racing engines from the ground up and their history in racing is to be respected. Their experience and knowledge with the 4g63, however, is limited.