Build Advice
 

Im about 4 weeks away from the boating season up here from being over and i think its time to do a little maintenance and maybe go a little faster. i have a 03 575sci, 15Xhours on the clock. been on here doing a lot of reading so i know enough to know i know nothing, or just enough to spend a lot of money and go no faster haha. so far my plan is floating around the bottom end not needing anything, all leak down numbers where pretty good at the start of the season and its ran all good for the year.

• heads. im leaning on the Brodix BB-R heads - 2061013 -, the flow numbers look pretty darn good for a "smaller" head, and flow pretty close to a lot of the bigger heads into the .600 range, the 115cc chamber should help with bringing up compression a wee-bit . they also dont raise the exhaust port so that keeps added work down to a minimum.
• cam. seems like a very popular pick is the "741" or 525 cam and i was honestly going to go with that. if its not broken kinda deal. especially for a not super extreme build
• Intake. going to retire the 256 and go 8-71 and aim for 6psi

My question is, am i even close? haha i had seen a few threads about the 741 not responding well to lower compression and with the 575 being a 7.5:1 motor. am i to low to try and get away with it? will it respond well to boost?
The heads, even with good numbers and what looks like maybe some good velocity, are they going to choke the motor out? i dont see my self wanting it to spin higher then 5800 (for now) will the 115 chamber vs the 118 chambers on the stock heads make any difference at all?
what head gaskets? i dont want to pull the motor and do a full tear down if i can avoid it and from what i recall MLS gaskets prefer a fresh surface.
any and all feed back is welcome please!

My suggestion is to call Eddie Young (Nashville). He did a real nice job on the 575's in our previous boat (rebuilt stock heads, custom grind roller cam, on water tuning, etc - bottom ends were in good shape, as I expect yours are).

He also has a custom fuel injection setup to get rid of the obsolete injectors in the throttle bodies - and it is very reasonably priced.

ive seen his fuel injection system and will be doing that set up when mine start to fail or i go past the stocks limits, for now im just going for some extra umph and getting rid of the one issue at a time, or two in this case i was hoping some of them would chime in haha. im still to far out i think to seriously bother someone and take up time form their day

The right ported heads and 871 will get you 750 plus easily.

i am now leaning to a 305 afr with a 114cc chamber, they dont seem to be much more and have way way more flow

NA I'd say perfect choice but sc I'd personally go a little larger int runner. 320-325 cc.

I wouldn't sweat the compression ratio. You will have plenty of blower, so use it. With the static being low, and the 871, I wouldn't sweat running 8lbs of boost.

There's lots of good head options out there. I wouldn't get caught up in port runner volume. I been running 330cc intake runners on a 8:1 iron headed 468 that makes over 800hp and are extremely responsive , that's the beauty of a positive displacement blower . The cam you want is one that coincides with how the heads you choose flow, how much boost you plan to run, etc.

Bang for the buck heads

Dart 3​​​​​​08 iron eagles

Engine quest 320

Promaxx from AK racing

i was thinking of going bigger, i figured any newer head is going to smoke the stock heads in flow any witch way i go. 8psi un cooled? eventually id like to get a whipple cooler and really crank it up. i dont recall off the top of my head but would a stock 575sci bottom end take 8psi?

i was looking threw a bunch of the threads you had along with the build on your motors Mild Thunder. id be happy if i even came close to that kinda power in my little V

8psi non intercooled from an 871, is probably a cooler temperature than the stock little 256 blower at 6psi.

If you changed nothing except the blower, you'll see some nice gains. 575 owners who did the dyers 871 conversion kits were very pleased.

The stock forged rotating assembly in the 575 is pretty stout. With head upgrade, cam upgrade, and the 871, it will be a different animal even at 6psi of boost.

Sounds like a fun build

thats what i was thinking but couldnt find any info to back it up about the IATs on un cooled readings. another reason im wanting to go alumi heads. i think i saw one on here about a guy going from the 256's to 8'71 and picking up 5mph(?) with nothing els changed
im hoping so, its currently running to 83mph on gps, hoping with a little less weight and some more motor it should show some nice gains

Icdedppls non intercooled 1071 making around 8 lbs of boost on his 540s, has around 135-140* intake temps iirc. It didnt seem to change much if any going from 6 to 8 psi.

My intercooled B&M 420s, are in the 105-115 range with 8-9psi. My boat takes a while to plane off. I can see the intake temps climb to 140-150, then as the boat lays over, and begins moving water thru the intercooler, the temp drops 30 degrees very quickly. I was always skeptical about intercoolers, as I had never found anyone doing any temp readings in the intake manifold. After installing them, I can say that they do in fact do their job.

I would love to see some intake temps with a 177 or 250 blower setup. It be interesting to compare.

not only interesting,might be down right scary!

might know where a bare set of afr 325;s are.wink wink.:D

i may know a guy that knows a guy that is looking:P they got the anodizing?
my 575 is bone stock as they come, maybe ill try and tinker with some readings. im guessing Mefi 3 only has a IAT in the throttle body in this application
what coolers are you using Mild?

anyone know where to get a smoking deal on some afr 305's or 325's?

been doing some more digging with different blowers, is a 10-71 to large for a 502? would a "standard" -71 intake manifold work on a 10-71? with the 10-71 being longer then a 6 or a 8, i would need to run a crab style cap on the distributor? or do i need to replace the whole unit?

10-71 would be fine, I believe the rotor diameters are the same with 6,8,10, and 14-71a (with the exception of some 671s) just the case length grows. There are different helix rotors too, I would not get too hung up on that, also there are stripped and nonstripped. Anywhere from 6-71 to 10-71 will work fine, you may want to do some homework on the length of a 10-71 to see if you can pull the distributor without pulling the blower, that is a PITA on 1471s. The nice thing about going with a bigger blower is that you would not be so dependent on a chiller (which they also can cause hatch clearance issues).

I have a stripped 871 with whipple chiller on my 575, I ran with stock cam and heads for years with 9psi boost and never had an issue, although on teardown it had a cracked exhaust valve. I would not be afraid to run the 7.5 stock (JE) pistons, even with a 671 which is a 155CI larger than your 256. The lower end has (Manley?) crank and Manley H beam rods so you will be fine there.

You are going to want to do a full tear down

I wanna avoid a full tear down as much as i can, i have this very bad habit of wanting to do more then is needed, like a 540 and a bottom end to take on 10+psi if I'm already in their why not right?, that being said if i have to go bottom end i will but I'm going to try and avoid it as much as i can, with 15Xh on the clock and it being a Havasu boat I'm hoping most of the clock time is from sitting on the beach. I did get a set of AFR 305's, going to go with Eddie young's EFI and some more of his recommended goodies. im just worried that a 10-71 will suck to much power at lower boost like 8psi vs a 8-71 and will be spinning to slow to be worth it. even if the 10 was at a 1:1 ration, on TBS site it show it around 10psi, with the bigger cam and heads thats probably 9 ish. that even in a 10-71 efficiency range?

When you pull the heads you might find cylinders glazed due to wash-down and may need to tear it down. Changing the oil pump may also be a good idea as well as a larger capacity pan. If you are going to have it out, why not flip it over and at minumum inspect the bearings? I will be the devils advocate...if you go with eddies injection plate you could easily go 540. Anyway, the faster you spin the blower the more heat you will make, I would think their would be some added safety margin with a 10-71. I dont think the parasitic loss would be much more than a 871 especially at 10psi or less.

if it shows any signs of having a weak spot it will be tore down and re built for sure, this was just going to be a little bump for the next year or two, using parts i can grow into. now with a 10-71 being longer, this may be a dumb question but i should just be able to put a crab cap on my existing distributor?

has any one had experince with the Comp cams 525efi replacement cam? pn 01-446-8 wondering if it will make any noticeable difference over the 741/525 cam in a boosted 502 application
comp specs
610/627
@ .050 in. (Deg)
235/243
Duration Advertised
289/297

The Comp EFI cam is near identical to the 741 but with the 14* LSA instead of the 12* on the Crane. You wouldn’t feel the difference in the boat but with everything else equal I’d take the 14*LSA.

does any one know the stock dish and how deep the stock pistons sit? trying to see how many points of compression im going to loose with the new heads

another newb question!
cam bearings

when doing a top end or a cam swap. do you replace the bearings? - condition pending of course
but if they are clean and and in good shape, do you change them out with a cam swap?

I have never changed out cam bearings on a top end refresh with cam swap and never had an issue.
As long as the cam you take out looks good, I'd leave them.

i would inspect the cam bearings but i doubt they need to be replaced.

That cam is fine. Are you going with diffetent heads? Your gains will be primarily be on the exaust side of them, the intake side of the head will not be worth much. So, with raised port height of good heads you will need to worry about tails lining up to the transom holes. Your limiting factor will be the stock injection. Sick of thumb typing, til tomorrow

afr CNC 305 heads cut down a little to get the chambers close to stock and clean up some damage in a port. the exhaust port is raised slightly(.375") but i think its small enough i should be ok. going with a Eddie young fuel plate then plumbing it the same way Whipple goes on the 500/525efi set ups

Eddies injection is a smart move, you could possibly go a little bigger on the cam. The next restriction would be the throttle bodies.

i went with that cam hoping it will make tuning a bit easier even if it leaves power on the table

as for timing chain with going to a roller. would i just go after a 500efi timing chain set, just get a new chain and 500efi cam strocket, or get a GMPP timing chain kit for a 502 gen 6 they both look like simple single roller set ups, the GMPP unit seems like the bang for buck option as it comes with everything
gmpp unit : https://www.gmperformancemotor.com/parts/12371053.html

what has anyone els used for a chain set?

yet another noob question

what am i looking for in a push rod. what is the go-to brand and material

AK Racing/Powermax BBC 315
 

I thought you were gonna give me a shot at those heads!! nudge nudge wink wink!!

i was going to

my builder had a set laying around from a take off and i could not pass up the deal

as for the rods, looking for a ball park on where to start. i know with a roller cam and the taller lifters ill be a lot shorter then the stock ones at like 9/8" dont want to have to order a whole set of rod lenght checkers just to use two