promaxx 317 heads
 

i am interested in hearing from guys that are using these heads,information about engine build and dyno results.

Mike I'm surprised you didn't get any response on this thread so I thought I would at least bring it to the top and hopefully get some activity. I will however just add that after Valako worked on mine he was impressed with the quality of the head and flow numbers he ended up with. I'm excited to see the real results on dyno but just not ready yet because of some unfortunate delays non engine related. Intake runners ended up close to 340 cc's and flowed 407 and exh was just under 300 @ .650 lift im pretty certain. The casting look really nice and have a generous thick deck.

From what I've heard from others with some non extensive port work they are a great improvement over any GM stock head at an affordable price. Wish I had true results but I know there's others on the form here who have them and just was hoping they'd chime in for you.

Im still a little ways away from results... but my short block is turning into a long block monday. I do plan on dynoing and I do plan on flogging the motor without mercy once its in the boat....

keep us informed.
Tks
jr

I will know before to long. My 548 builds with heads and 871 blowers will give us a clue. Jim has no doubt we'll see 1,000 hp with 8 pds boost but time will tell. I'm only after 900 to save drives but he did same builds not long ago that dynod ove 1,000 hp on 540's. I'm using different cams though that he's not thrilled about. Same as merc 900sc. The heads are a basic test for first engine. Cams will be swapped out on dyno to what Jim v wants. Shorter duration and higher lift. Either way valvetrain will take a beating but I really don't care as boat will be limited use given short season etc.

definately solid roller regardless. Otherwise billit hyd roller with solids.

What are the specs on the 900sc cam?

i built a pair of 548,s with 8.71,s they had dart 320 heads,they made 950,they had crane 651 hyd roller cams.i set it up for 8 to 9 lbs boost,the 320 heads had no port work done to them.imo they needed a bigger blower like a 10.71.i used to run the crap out of that thing every weekend and fixed the xr drives monthly.

There like 252/257-672/672 SR. Can't remember lsa. There a little hard on valvetrain but I don't log many hours anyway. I thought about going back to hyd roller but have bad luck with hyd lifters and already have new SR lifters.

Mike that cam is the ticket and I know you and several others have had great success with similar builds both NA and SC. I've been looking at another Lunati SR cam. Both carb guy and Valako would like to see me with a little less duration. I already have the cams and could likely make more power with cam swap but like I mentioned I'm concerned about the drives but suppose I could always just run less boost and install more preferred cams.

Lunati

• Advertised Duration (Int/Exh): 273/279
• Duration @ .050 (Int/Exh): 243/249
• Gross Valve Lift (Int/Exh): .655/.663
• LSA/ICL: 110/106. Timing events look good but if I went this route I'd have Lunati do a custom grind on a 114. How do blowers react with a tighter lsa?

those 651's would be the smartest thing to do but... Any other solid rollers that come to mind please post. I'm not sure what ones Valako was running but I'm almost certain they are hyd rollers with solids.

what did you end up for cam?