FORGED BLOWER PISTONS VS. NATURALLY ASPIRATED ONES

[THE BOSTON SIDEWINDER]

WHAT ARE THE MAIN DIFFERENCES BETWEEN NATURALLY ASPIRATED ENGINE PISTONS AND BLOWN PISTONS, ASSUMING BOTH ARE FORGED? CAN BLOWN PISTONS BE PLACED IN A BLOCK AND FOR A SHORT WHILE TO BE FED BY A CARBORATOR? (MAYBE JUST A WASTE OF MONEY FOR A SHORT TIME)? WHAT J/E (OR THEIR LESS EXPENSIVE LINE) PISTONS WOULD FIT THIS BILL? IT WILL TAKE ME A WHILE TO GET THE WHIPPLE CHARGER FUNDS SAVED UP, AND WANTED TO RUN THE 502 IN THE MEAN TIME ON JUST A CARBORATOR. IF I DIDN'T HAVE TO GO INTO THE ENGINE TO CHANGE OUT PARTS WHEN THE TIME CAME TO GO BLOWN IT WOULD BE A LOT BETTER! (AND I THINK CHEAPER)..BILL.

[Blown 472]

You will have lower comp ratio, if you dont mind running a carb on a low comp motor, it wont do anything to it. I put together a 7.70 to 1 440 and broke it in on a carb and drove it with a single carb, it was kinda a dog but it ran fine.

[OMEGA_BUBBLE_JET]

should be very 'pump gas friendly'....... :D

[Duane HTP]

Definitely go with the blower pistons. Then it's done. Might be a little dogie at first, but the blower pistons are much thicker to dissapiate the heat from the motor once the blower is put on. The top rings on the blower piston will be further down from the heat too. Then when you are ready to put on the blower, the engine will be broke in and the rings seated good.
[ September 23, 2003, 07:16 AM: Message edited by: Duane HTP ]

[058]

Blower pistons have a stronger oil ring land. Most nat. asp. pistons use a oil slot for return, blower pistons are drilled, less material is removed making the piston stronger.

[Blown 472]

058:
Blower pistons have a stronger oil ring land. Most nat. asp. pistons use a oil slot for return, blower pistons are drilled, less material is removed making the piston stronger. What about a trw forged, non blower application??

[THE BOSTON SIDEWINDER]

THANKS, ALL!
... HEY OMEGA_BUBBLE_JET: THAT SOUNDS LIKE A WINNER, AFTER SPENDING ALL THIS MONEY I'LL BE ABLE TO TELL THE WIFE HOW CHEAP IT WILL BE TO BUY GAS FOR THE BOAT NOW??!
...DUANE HTP- IF I WERE TO SHAVE THE HEADS COULD SOME, OR A LOT, OF THE C.R. BE RETURNED TO GET A LITTLE MORE OUT OF THE MAGNUM 502 THAN STOCK POWER(WITH THE BLOWER PISTONS WE'VE BEEN DISCUSSING)?
...058: SO FOR GETTING A LOT BETTER PISTON, I GET BETTER OIL RETURN TOO? KOOL....THANKS! BILL.

[ttmott]

If running less than 8.0:1 make sure the cam is really low on duration (valve overlap)so the effective compression will be up. The only other problem with dished pistons and no forced induction is two things:
1. The quench area, if you are running quench or closed chamber heads, is gone and the flame front will not be proper causing a bad fuel burn.
2. The cylinder turbulence is not as good due to the VE being so low and again bad fuel mixing and uneven burn.
But, it will run....
TM

[Duane HTP]

Bill, you can buy blower pistons that are flat top and you won't have to worry about the heads. Call Probe, or Ross, they can help you

[superdave013]

I ran flat top Ross blower pistons for years. I leaned on them really hard and they held up.

[058]

Blown 472:
058:
Blower pistons have a stronger oil ring land. Most nat. asp. pistons use a oil slot for return, blower pistons are drilled, less material is removed making the piston stronger. What about a trw forged, non blower application?? I've used TRW pistons in my turbo hoopty with no problems whatsoever. They just have the oil slots as described and do not have the small holes that blower pistons use. Should be no biggie with the TRWs.

[Blown 472]

058:
Blown 472:
058:
Blower pistons have a stronger oil ring land. Most nat. asp. pistons use a oil slot for return, blower pistons are drilled, less material is removed making the piston stronger. What about a trw forged, non blower application?? I've used TRW pistons in my turbo hoopty with no problems whatsoever. They just have the oil slots as described and do not have the small holes that blower pistons use. Should be no biggie with the TRWs. Thanks 058, I might be building another blown 440 for a bracket car.

[TIMINATOR]

For a blower make sure you 0 deck the block so the quench area is tight,square deck it while your at it & BHJ deck if you can afford it, run extra wall clearance and ring end gap,modify(port!)the oiling system,and have someone GOOD port the heads(mostly on the exhaust side),run premium bearings and DON'T SKIMP ON ANYTHING! There are so many blower boats that look GOOOOOD! and don't run,my greatest joy is beating them with a single 4 bbl.carb! My other entertainment is seeing how long their stuff lasts,or doesn't. Finding an engine guy that KNOWS jetboats is tough,finding one that knows blowers and blower carbs is VERY TOUGH! Before commiting to anyones shop, ask how many carburated blown car engines, and blown gas jetboat motors they have done and ask for names and phone #s. Doing this is harder than they think,don't spend your $$$$ for them to experiment with!!!GOOD LUCK! you'll need it!
:) :) :) TIMMINATOR

[newbie Mike]

Boston
You have a whole host of issues to resolve in running a blower set up with a naturally asperated carburetor . With a blower you must determine what pounds of boost you want to run, and compression ratios of 8 to 1 or less is probably most desireable, and give a greater chance to keep everything together.
Of course the cam is also a major issue as the durations, overlap, and lift are much different.
I am not sure what engine you are running but on some it would be better to increase oil porting to the heads and also on some to change to flow back. The engine guru's I have talked to have very strong opinions on this

[THE BOSTON SIDEWINDER]

NEWBIE MIKE...I PICKED UP A 8.2 GEN VI 502 GM 4 BOLT ROLLER BLOCK.
TIMINATOR... IF YOUR MAKING THAT KIND OF POWER W/ NO BLOWER, MAYBE I SHOULD LISTEN TO YOU ABOUT JUST MAKING MY ENGINE KIND OF WILD WITH NO BLOWER, BUT IN THE FUTURE I WANTED TO PUT THE ENGINE IN A BIGGER BOAT WITH A DUAL JET DRIVE SET UP. I ASSUME THOSE TAKE A LOT OF POWER TO GET ABOUT 60 OUT OF A 25 FOOTER OR SO...BILL.

[Duane HTP]

You are on the right track for that application!

[THE BOSTON SIDEWINDER]

SUNDAY NOV 2 I'M GOING TO THOMPSON SPEED WAY IN THOMPSON CONN.FOPR A HUGE PARTS SWAP MEET. MAYBE I'LL BE ABLE TO FIND SOME PARTS FOR THIS 502 BLOCK I'M GOING TO BUILD THERE.