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-   -   Sci 575 head replacement. (https://www.offshoreonly.com/forums/do-yourself-boating-budget/387904-sci-575-head-replacement.html)

hpmaniac 04-30-2026 03:53 PM


Originally Posted by snapmorgan (Post 4946672)
Yes, cam was degreed

Hmm i bet those has a 2.3 intake valve. That is crazy they had radial intake clearance issues.

snapmorgan 05-01-2026 08:50 AM

https://cimg8.ibsrv.net/gimg/www.off...7960c13af0.jpg
Here is a pic

hpmaniac 05-01-2026 03:30 PM


Originally Posted by snapmorgan (Post 4946725)

I just measured mine, I checked between 10 before tdc and 10 after with dial indicator and never found anything less than 225ths. My cam is 621 lift intake 241 at 50. Afr 315 2.25 intake. I checked and most of those Brody heads have 2.3 intake. Maybe valve float at some point. Thanks for this because it made me double check

hpmaniac 05-02-2026 11:53 AM


Originally Posted by snapmorgan (Post 4946663)
A few years ago I did a cam and head upgrade on my 575SCI. Installed a custom roller and a pair of Big Brodies. I had some very slight piston to valve clearance issues with the stock pistons due to the bigger valves in the Brodix heads. It never caused an issue and I didn't even know about it until a couple of years later when I had the heads off again. There were witness marks on all of the pistons just outside of the valve relief area. I installed a set of JE blower pistons that time which had larger valve reliefs.

Just something to be aware of.

did you have any issues with valve cover fitment on yours? I don't like the way mine feel, I machined the 2 rockers per side that touch, the adjustment rocker nuts clear but damn there close. It's just the way they fit the head surface on these afr heads.

hpmaniac 05-03-2026 12:55 PM

https://cimg3.ibsrv.net/gimg/www.off...aeb5264449.jpg
https://cimg5.ibsrv.net/gimg/www.off...de8a3f97ee.jpg
Sci 575 upgrades coming along.

hpmaniac 05-03-2026 01:04 PM

Upgrades are these
my spec hydraulic roller, 241 251 637 621 intake on a 114 installed at 110.5 intake cenerline.
gm hydraulic lifters.
Afr full cnc 315 head with inconel exhaust valves.
young performance fuel system and injection upgrade with his tuning.
Whipple intercooler.
Stock 575 bottom end, only had 111 hrs on her. Compression specked out at 7.8. I rolled new h series main bearings just because along with a melling hv pump. Young performance double roller chain that he has custom built for him.
new mercury starter, water pump, oil lines.
New blower shop 250 replacement blower with a 3.35 pulley. I really went back n forth on blower, I already had the whipple intercooler so I decided to stick with the smaller blower. I'm looking for between 750-800 hp so this little blower with the whipple will do the job and should be very reliable.

hpmaniac 05-03-2026 01:10 PM

https://cimg1.ibsrv.net/gimg/www.off...0f62344789.jpg
motor goes in this girl, ultra clean 2003 velocity 280, hull has 355hrs. With the stock sci 575 engine with young performance injection and blower shop replacement blower i was running low 90's. When I bought the boat it was running around 76, with engine tuning and prop tuning i went from mid 70's to low 90's!
goal with new engine combo is 100, I think I'll be there or close. Once i learned how to drive this boat it was a blast. Such a fast hull!!

Padraig 05-03-2026 02:37 PM

Beautiful Velocity! I had a 1998 280 before I got the VR 1. Great Boats and a great builder to deal with.
.
Padraig

hpmaniac 05-03-2026 05:07 PM


Originally Posted by Padraig (Post 4946821)
Beautiful Velocity! I had a 1998 280 before I got the VR 1. Great Boats and a great builder to deal with.
.
Padraig

Steve stepp tought me a lot about driving the boat, amazing how sensitive they are to having the correct prop.

Padraig 05-03-2026 08:13 PM

What prop are you running?


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