I do. Flow numbers when prospective buyers ar comparing them to other manufacturers. Same on the exhaust side. AFR has 64CC, Dart is 75CC. Don't flow as well either. That said when you compare heads you always check flow numbers and rarely check actual port CC. You take them at their word.

 

Did this you're right it's painfully obvious when I compare mine to an AFR head how shrouded the valves are. Unfortunately I have the heads installed already and the bottom end is completely assembled so I can't cylinder match the heads and un-shroud the valves now. If it becomes a big enough concern down the road I'll consider it. However I am going to be building a 406 over the next couple of years and on the heads for that I will remember that process. It may get AFR heads for that one in any case not sure yet.

I didn't feel I knew enough about what I was doing to mess around with changing the dimensions of the runner or short turn, long turn dimensions so I left those alone for now. Just like you guys said smoothed stuff up and skinnied down the bosses a bit.
If I feel like there still more I want out of these heads after running it for a while and I get braver, then I'll take em back off and do a little more. Unfortunately there are no flow benches in this area or dyno's so any thing I do can only be judged by timing or seat of the pants.

I did put together a water depression monometer and using a vacuum and a home made assembly was able to compare flow before to flow after for the ports. Both showed improvement. Then again not all results are necessarily flow related so that's only one consideration. The only one I can measure right now.

 

I probably would have taken them at their word if the 64cc chambers had actually been 64ccs and not 67ccs. So you think they increase the port volume to get the flow numbers up?

 

Did you know some flow heads on a 4.125 bore to make flow numbers look bigger ? This also gives an idea how much shrouding you can have in a smaller bore.

That aside port velocity is something that is to be considered as well. The trick is having a big flowing port, but keeping velocity up. This is an aspect I didn't venture in when I did mine. It involves working on the short side radius

 

Right, By doing what they are doing Dart is increasing their flow numbers but sacrificing port velocity to do it. They are killing bottom end shooting for maximum peak power, something that is done way to often by manufacturers and those designing and building their engine.

 

I'm glad you said that Mako. That is exactly what I think they are doing. The end user takes it in the shorts.

 

Don't overestimate heads and intake runner cc's (unless you're talking about a more exotic head like an 11-15-18° which has more to do with valve shrouding than anything else). Usually the induction and exhaust side plays a more significant role in the power production and VE of an engine, together with the cam (duration, lift, overlap and all other variables). At least that is what I've experienced untill now.

 

I can't argue with that. I'm just gonna get this engine together and see what I think when I get it all running well. If I'm not satisfied with the heads performance (and I can narrow it down to that) I'll pull them off and do more. Unshrouding the valves will be among that.

 

I think you have improved the heads nonetheless. I was lucky in that I read a lot of books before attempting it. They pointed me into the direction of unshrouding the valves as one of the most important things as well as the bowl area (D. Vizard). The rest came when I joined the speedtalk forum. Lots of knowledgeable people there. Couldn't have built my engine without the advice of people over there.

 

And THAT is precisely why I will never buy another set of Dart heads ever again. Bought mine in late 90s...to this day they are still doing it. Slight variance is gonna happen, 1-3cc????? Not 20. or 10

Now dont get me wrong the castings are nice they work great and all but still. if Id known how big they were then

I woulda bought some old school 190 AFRs (elims werent out yet) that woulda worked a lot better.

3 motors later these heads just about work on the car. + money trying to get a good # out of them
Wasted thousands!!

 

Been over there too. I'm really treading water just trying to understand some of those guys.
If I had the know how I probably would have done some short side filling and reduced the total volume of the port closer to 180ccs. Keeping my fingers crossed.

I haven't actually run these heads yet but with such loose tolerances I'm not pleased either. I would have to agree so far.

 

Think youll be Ok. Id leave the short side alone for now.
Bet youll be happy with the way they run. THey are not bad heads by any means quite the opposite I was just ranting about the whole truth/advertising thing.

 

I hear what your saying.

 

Pricewise they're not that bad. When looking upon the shape of runners/chambers there is not much difference between the darts and afr's

 

I don't disagree with that. I think most of their R&D want into the intake port shape and valve seat configuration based on my far than experienced eye. Exhaust looks like it could use some work. It's a "you get what you pay for" scenario I think. If I want tighter tolerances, nicer ports better fit and finish I'm gonna hafta pony up another$800 to $1000 for it. I like that they are aluminum and not likely to crack or warp even under moderate to heavy use, and US made, just be nice to have a little more quality control out the door.

In the end I hope that they work well and most likely they'll be just fine for this application. So I'm not ready to condemn them or anything yet. I'll wait until I got some time on them to make my final descision on whether Darts will be a future purchase or recommendation of mine.