Again that was what Dart was telling people about the heads. Yes it would need more of an angle cut before flat milling but like I said I was told never said it was confirmed. They still claim its was done that way. But like all iron heads they are never on target cc regardless of brand. The tech sheets say one thing but till you start machining you never know for sure and the valve size would also depend on the amount you could mill as well as they came with a 2.055 or 2.08 intake as per heads I used then so a heavy angle mill would be into the seat area. While they say in print it is possible after you cut a head and learn its coming up short of the target is a problem I have seen as well. an out of the box irn head with a .060-.080 angle cut is almost into a valve seat with a 2.02 valve based on seat height in the chamber.CGT wrote: ↑Wed Mar 11, 2020 11:10 amHow would that little amount milled at an angle change the valve angle to 21.5? Or take 23 cc's of volume out? That don't seem to jive out. It would take .140 or so off roughly, with a flat mill to get there...They either don't start at 72, or they take a hell of a lot more off than what they told you at an angle, or they aren't 21.5°. Or all of the above...unless I'm missing something here.ProPower engines wrote: ↑Sun Mar 08, 2020 8:34 pm I talked to dart when they 1st came out they told me they were a 72 cc angled milled .040 and flat milled .060
I have some iron eagle heads in here for a mill job to 60cc and they are advertised as 67cc but they are really 73cc out of the box others I have used were closer to advertised target volume but never dead nuts on target volume.
There was alot of issues with the roll over but during that time iron heads were still really popular and the +/- 1 degree valve angle rules were common with most race bodies. Most just tried to upgrade to the smaller chamber and then found all the valve gear was not going to work because the head was rolled then off set stud mounted rockers could be sub'd but they were still not the best way to go on them.
I always used Crower SS shaft rocker setup's on the PT EQ and Dart heads. Cost was better and easier to setup and mounting hardware was easy to get and swap between other heads.
Pro-Topline from NZ also had a head in production as well which Comp took over distribution among other things but the topline head was 1st out.
Shaver was selling them like crazy back then as well but between the Pro-Topline and the EQ head which was basically the same head as the PT head at the time them came the Dart iron platinum series heads.
There was the piston issue that was learned along the way and most budget racers that bought into the small chamber head found out the hard way about what else needed to be changed to make them useable for their engine combo's.
It sucked as there was tons of guys that learned the hard way about them.
They were a great head to start with and build around for FT piston class's because they were offered with decent port sizes and valve size options.
But as a cheap up grade to gain compression without the time and cost of a tear down to up the compression with pistons etc. etc. they are not a real cost effective alternative for a guy on a tight budget not wanting to swap out all the valve train parts as well as PTV issues to deal with.
But there was a piston with a small dome available from Diamond at the time to further boost comp. if there was no piston rule or comp. limit. They were special order at the time as well.
