MILD THUNDER

iTrader: (3)

Nice number for a low compression 502. Those are the as cast heads with the CNC program run in the chamber only correct?

SB

iTrader: (1)

Totally depends on the motor build up.

Also camshaft vs exhaust sizing/wave tuning has a large effect.

I did a few million tests on a basic small cam low compression 502cid/540hp with wet marine / dry dyno headers/ undoing each belt accessory (including belt driven sea pump) one at a time / etc /etc / etc. 15hp max difference no matter what was done / added / or taken off.

The more actual overlap a cam has, in a NA motor, exhaust can be a big deal !

JRider

iTrader: (1)

What size carb spacer? Material? Is it 4 hole or wide open?

Unlimited jd

iTrader: (5)

Open, 1" wood. Consistently worth 10hp on the last 3 engines I've tried it on and all the ones the dyno operator has tried. 4 hole typically worth a couple more ft lbs, couple less hp

Drock78

iTrader: (2)

So 1 guy is saying 50hp and another guy is saying 15...? That's a bit of a difference. Just curious cause my 500efi dynoed at 522hp and 591ft/lbs of torque fully dressed with all accessories wet exhaust and pulling water through the sea pump. I guess I'm pretty darn happy with that.

Unlimited jd

iTrader: (5)

Found the cam card. .645 lift 234 dur intake/ .640, 240 exhaust. 112 lobe seperation

SB

iTrader: (1)

Different motors. Different rpms, heads, cam, compression, etc,etc.

Read what I said about cam overlap vs exhaust.

Also, I've been a part of 100's of non marine engine dyno tests and I'll tell you accesory hp loss not only depends on what you are turning but how hard (rpm) you are turning them. It'd usually not as much hp loss though as magazine ads make it look like.

Anyway, so yeh....had a chance to run that 502 full wet....exactly how engine would go in boat. It was low compression (8.8:1) with mild cam and good heads. Ran 3 different intake manifolds and different spacers also.

Nothing really phased that engine. I think I could have pissed in the carb and it would have ran the same. LOL.

SB

iTrader: (1)

I look at CFM #'s a lot. Of course I do. Ooops, forgot I'm SB here. Normal name is CFM.

Anyway - anyone notice this Motor could have used more carb ? Also, it looks like the carb had difficulties keep a half way linear A/F ratio.

The A/F ratio on the sheet appears not be to a wideband, but thru the fuel meter vs Air meter. So , the ratio is not what was actually used by engine but you can look at it to see peaks and valleys. Seems to flutter. Could be the carb itself, but I see the same sort of trends on carb's that aren't sized the way the motor wants.

Seems to be some power left in the carb dept. Not just WOT.

Just letting out some thoughts from my own couch / armchair on the internet. LOL.

242LS

iTrader: (1)

Those at not the babblings of a mad man.... Bob Madara told me I'd need more carb. He suggested 950-1000 CFM. They were new last summer, so I didn't want to spend more money on a new set.

Unlimited jd

iTrader: (5)

I had brought my 1000 cfm pro systems carb but since we made the power we were looking for and even if it picked up 30 hp new carbs aren't in the budget, we left it as is. Those are calculated air fuel numbers from the air and fuel flow data.
Rotating assembly is hp500.