There was no hydraulic lifter bleed off during my PV clearance measurements because I used low load checking springs that are designed specifically not to compress the hydraulic lifter during these measurements. RE: http://www.summitracing.com/parts/CCA-4758-2/

Again The HP3 Gen I cam had 0.030" min PV clearance and I made a personal decision to cut the releaf 0.040" deeper because I was not using the correct high load valve springs that the HP3 engine specified.

Again the HP3 Gen II cam had 0.250" min PV clearance as configured for the HP3 Gen II engine. No way the intake valve is going to hit the stock piston unless something in the valve train failed.


In any case the new Dart heads will be out soon and can then be tested to see what is what.

When the engine is out of the boat you need to Remove the heads to replace, pull the oil pan and front cover to replace the camshaft, so it does not take much to replace the stock pistons with a forged piston at that point because the stock cast piston is weak even at 525HP. Then you can put what ever cam you want, you can add a superchager down the road, you can make 575HP with a stock intake manifold. You can add a Raylar intake and make 600HP....Just put the pistons in so you can use .600 lift !!!

I was wrong about one thing, The 575hp Innovation Marine "HPi" was campaigned on a limited basis and still is being campaigned in this boat maybe more, pictures of both attached. This engine logged 190 racing hours before finally needing new bearings. It has the stock Vortec intake manifold with the previously noted mods. I suspect the heads also embody the Jim V upgraded 2.25 intake 1.183 exh valves/porting. The HP3 closed cooling is also replaced by direct sea water cooling in the HPi engine. Pictures were taken yesterday at the Miami Boat Show if you are in the area and want to see for yourself.

head CFM data
 

At 0.6" lift

Dart 8.1 heads 348cfm Int/ 249 cfm Exh (2.195" dia Int/ 1.89 " dia Exh & 11/32" dia stems) from Dart tech line.

Best Jim V 8.1 heads 350cfm Int/ 252 cfm Exh (2.250" dia Int/ 1.83 " dia Exh & ?1/4" dia stems) from Jim V

Raylar 8.1 heads ~348cfm Int/ ~226 cfm Exh (2.195" dia Int/ 1.79 " dia Exh & 11/32" dia stems). Raylar head cfm data obtained from Raylar web site when heads were first made available. This data is no longer posted on the Raylar web site that I can find.

Note: Corrected typo for Jim V exhaust CFM, was incorrectly posted as 275 now corrected to 252CFM in red

Rage,
I will probably see JimV tonight or tomorrow. I will have him dig through his notes and pull up his info. He was just at Dart a couple weeks ago getting his new BBC castings. Maskin let him change the ports on 7 sets of PRO1's for Jim's new marine head. I know they talked about Darts new 8.1 block and heads. Maybe I can persuade to comment on his dealings on the 8.1. I think he also has a set laying around the shop that might be ported.

Rookie,

It would be very interesting to hear what cfm Jim V thinks he could push the new Dart 8.1 heads to using bigger intake valves (2.30"dia?) and exhaust mods.

CP Performance was supposed to have the new 8.1 heads at the Miami show... They didnt, I wanted to check them out. I even made a special trip the second I walked thru the gate, I went straight to CP... They did however have the block and it was ok but I dont think you could bolt all the 496 Mag/Ho stuff to it. Has anyone made a Mercury style engine out of the block yet? It might not work...

For what its worth, yes, that must be old data. Rays heads flow more than that now, I just flowed mine before we put them on. But, either way, with a .600 lift cam the rpm redline for most of these cams is 5400 (some are 5600) so what is the sense if the heads outflow most of these cams and they all fall off at 5400? The CFM doesnt really mean much in this case. There are a lot of other factors other than what the heads "flow" and you are going to have to turn them waaaayyy higher to benefit.

625hp 525EFI Upgrade Kit
 

This is off topic. Teague I think it was had a 525EFI upgrade kit for <$4000 that provided 625HP. The kit included a set of CNC'd 525 heads complete (exchange), cam and ECU reflash. That sounded pretty good for someone with a 525EFI that was ready for a refresh and looking for more hp.

Weh in Doubt, Check it Out!
 

Yes, as I keep trying to tell everyone if they were listening carefully, Raylar has a standing order in at Dart for two of the new blocks, WHEN!, Repeat WHEN they are provided with exactly all the correct configuration to allow them to be used in place of the stock 8.1L 496 engine block so that everything will transfer over correctly and exactly as needed I will be one of the first to let you all know! In the mean time anyone that wants can order Dart's first almost attempts at getting the block correct for use and transfer and then they can pull their hair out and waste their money trying to get everything to fit and work!!!
When Dart gets our block orders built as needed we will be one of the first to let every expert here know. I am not attempting to bad mouth the product, I am just trying to help get the product correct!
I could just keep my mouth shut, sit on the sidelines and LOL as users frustrate themselves and make an expensive lesson out of what they don't know!

Rage,
As for that 496 in the boat at the Miami show, love to see the engine dyno report on that engine showing 575HP on a stock GM 496 8.1L intake. I'll believe it when I see it and verify its not a doctored or tweaked dyno report. I'd also like to see what exact pistons and such are in that engine on a tear down, got a suspicion that all is not what its purported to be?? I know Tom an crew at Flagship Marine tried for a long time tried along with us to make more than 500HP with the stock block and intake including fairly major stock head mods,intake mods, cams, exhausts and never got there as well as a few other engine builders around the country from about 8-10 years or so ago also.

How about this for some interesting info?
We are about to clamp a Raylar HO600 engine on a respected independent dyno in a week or so and I am going to specifically start the dyno test with a stock 496 intake and throttle body on the engine, make some pulls and then change over to our intake manifold and measure the exact results and the vacuum numbers the stock intake will pull from about 4500 rpms to 5500rpms and lets have readers here on OSO look at the results and see if I know what I am talking about or not! As we sometimes say in the performance game, the bull**** stops when the green light drops!!

As for the current version of the Raylar BigPower aluminum heads like Kieth received recently I can assure you they flow more than 342cfm intake at .600 lift and I am sure any good aftermarket 8.1L head, iron or otherwise with a good intake port and 2.25 intake could make these flow numbers also.
I guess if the added weight 100lbs of iron heads and lower limits of compression for the iron heads are not an issue and cost is the only issue then the iron heads will make sense for some and I think that's great and they should buy them if they choose.
If iron heads were the best real performance answer, why would all those aluminum aftermarket and stock performance heads be made from aluminum??? for SBC's, BBC's and others???
Raylar makes aluminum 8.1L 496 heads for a reason-they are just a lot better!, especially on a closed cooling system engine like the Merc 496!

Best Regards,
Ray @ Raylar

As mentioned repeadly the pistons in the HPi engine are not stock and are forged.