Rage

Any of those heads headed your way for porting?

Rage

I called Dart tech line. He said that the only dimensions (for assembly purposes) that are not stock are the valve guides (stock 3/8", Dart 11/32"), the spring seat dia (stock ~1.3", Dart 1.25" or 1.437" your choice) and the exhaust valve (stock 1.79, Dart 1.88). I asked if I could order a set of these heads with 3/8" valve guides. He said he could not see why not. They still do not have detailed CFM vs lift air bench data available for these heads.

Keith Atlanta

Assume I am an idiot... (giving myself credit)

I dont understand how you can flow a head at .700 lift if the cam is actually .600 or so. How is it relevant to performance?

Rookie

iTrader: (4)

The head will flow the air at .700 so if you put a cam with that lift you would be fine. That is potential power. Some heads will not flow the air at higher lift. So if the cam you want to install is .684 lift you are fine.

Rookie

iTrader: (4)

The important thingis the head will flow the air at .700 so if you put a cam with that lift you would be fine. That is potential power. Some heads will not flow the air at higher lift. So if the cam you want to install is .684 lift you are fine.

Raylar

Rage:

I have to say sometimes you just flat "crack me up!"
Why would you ask if a newly designed good flowing head be on its way to Jim V. for Porting? From What Tyler Crockett already posted here on these heads, it sounds like they are flowing to much air, let alone not enough!? The only heads that generally need porting are poor flowing heads that need substantial improvements in the original castings and design.
I know that Dart obviously took great pains to make sure their newly designed and manufactured head hit good flow numbers right out of the mold as most of their well engineered aftermarket performance cylinder heads do.
As for cross compatibility with stock 496 (8.1L) heads lets hope they have very little flow equalities or they are going to be a pretty poor performing head.
As a cylinder head designer, manufacturer and pretty good authority on cylinder head performance, especially when it comes to the 496- 8.1L Gen 7 engine I can caution all who consider air flow cfm numbers to be careful in applying those flow numbers (flow bench) to actual or planned engine performance, especially when it comes to naturally aspirated marine high performance engines. There are many other very important factors such as low lift flow, port air flow velocities, fuel atomization, valve throat percentages, fuel mixture mixing, mixture tumble and swirl in the cylinder, mixture burn rates, combustion chamber temperatures, burn propagation, flame travel, spark ignition thresholds,etc., etc., that will all combine to establish whether a cylinder head is really a good or great overall design.
I always find so many discussing cylinder head air flow numbers especially at max lift as being the end all, be all of cylinder head performance. Hope you and others trust me when I say that is is probably only the beginning of many important features, factors and measurements that will determine the ultimate performance level of a cylinder head! The demands on a cylinder head will also change with the application, rpm operating ranges, power and torque levels desired and whether its being used on a long stroke, short stroke, naturally aspirated or forced induction engine.
As for being able to transfer all stock 496 (8.1L) valve train into these new bare heads, I would say that's probably not the best idea other than being the CHEAPEST option because the stock valves other than the exhaust valve shape are pretty poor choices due to their inexpensive material makeup, heavy valve weights, oversize stems and marginal spring, retainer and lock strengths.
My thought would be that Dart can supply good quality valves, retainers, locks, valve springs and the like and fully fit the Dart head much less expensively than a private single entity can and their head shop can turn out a better fully fitted ready to run "out of the box" version of these heads than most average shops could do and hopefully still keep the cost of these IRON heads in a reasonable range for those users who want to keep the budget tight and the ease of a complete product in their upgrade usage.
I say these things here not to bash or be a "smart ass" but to make sure our OSO readers and 496 owners get a reasonable sense of what is what with cylinder head performance so they can make good decisions when it comes to buying a good product and get good performance improvements whether it be Dart or Raylar heads for their own 496 usage.
As for my statements about one of the reasons Dart has been coming up with new 8.1Liter 496 blocks and heads, I don't believe I said that industrial replacement engines was their only reason for the product, I just said with my own personal discussions with them it was told to me that that was a major reason.
Just thought I would clear that point a little and impart some more thoughts about cylinder heads and the importance "big" flow numbers.

Best Regards,
Ray @ Raylar

Rage

As you say it is a new design that we have yet to see what improvements can be made and if one would want to increase the stock 2.219 stock intake to 2.25 or 2.3 that would likely require some porting. Correct me if I am wrong but have you not developed a CNC porting of your Big Power heads for some of your engines?

Rage

That is exactly the point. To have the availability of a lower cost head option to improve the power from the 8.1 starting with a bare Dart head built up reusing all the stock valve train to a full Dart head assembly to your Big Power heads, etc. and iterations in between.

Rage

ttt

jmccart

Dart has a carb. intake for these heads on the website now.