bajabrat

Does anyone have any information on using aluminum heads on a 525 SC motor? Currently have valve and valve seat problems. Already have replaced valves once.....been told it is a fuel pressure issue, but don't know that I agree. We were told to use larger fuel lines, but they are stock motors and do not know why the stock lines are not sufficient.
Motors have only 70 hrs, and have not been abused. Always use 93 oct fuel.

DMOORE

What type of heads are you using? Do they have smaller combustion chambers that raised your compression? Usually, going to a good aluminum head is a big plus.


Darrell.

bajabrat

Brodex Heads. Intake valves were slightly bigger.....as far as the combustion chambers, not sure. The guy that built our engines ordered these heads.
One motor blew, so had both rebuilt. This is the second time in 70 hrs that we have had to replace valves and seats. Now same guy who rebuilt motors is claiming the trouble is due to needing larger fuel lines.
We only had this gentleman rebuild the heads. We are having another mechanic we use put them back on motors, but this mechanic doesn't think that is the problem. He is wondering if we need special valves or seats for the aluminum heads on SC motors.

FIXX

iTrader: (2)

the only time you will need valves and seats are when you run a blower motor with out enough fuel pressure or you have too much timing in them or your carburetors don't have big enough jets...if i were you i would spend the extra money and have the engines dynoed.. the rite dyno shop will use afr sensors in the exhaust and that should tell you by the readings if your engines have enough fuel going in them..

DMOORE

For a blown boat motor, I would suggest stainless intakes and inconel exhaust. The valves have to take a huge amount of heat on a boat motor. It's always under a serious load unlike a car.


Darrell.

Griff

I can tell you that with 8#'s of boost and a bigger roller cam on a 525SC that the stock fuel pump and lines are enough. I did bump the jetting on all 4 corners up 4 sizes. Stock jets are 98's all around. Do you know what jets you have on your carb????

What else was done to engine besides the heads???? Stock 525SC's use GM rect port heads.
Stock compression is only 7.5:1 and stock timing is 35* at full advance.

I would say the actual problem is not the valves or heads. I think it is in the tuning of the engine.

blue thunder

Ditto. If those heads didn't come with inconnel exhaust valves you are just asking for trouble. I just redid the heads on a stock sbc crusader engine and it even came with inconnel exhaust valves. They are a must in marine apps, particularly blown motors.

bajabrat

We are definitely doing that this winter when they are getting pulled again! We just put bigger jets, will look into the timing as well....thanks

bajabrat

just bumped up to 102's .........always thought that the timing was an issue, but mechanic sat them at regular 454 timing, not for SC motors

bajabrat

mechanic thought builder had installed inconel, but he installed stainless steel valves. we are looking at sending the heads to a place in indy that is spoken highly of.