I don't believe so. Maybe after some extrude honing and what not you might get close .

Was this a 18726543 firing order?

No. Even the 500EFI has a hard time with this HP.

MPI has a good intake for a tow truck.

BSFC is not really a good measurement of lean or rich. Yes, it's #'s can be swayed by lean or rich but that, again, is not the true nature of BSFC.

It is how much fuel it takes to make each HP.

Peak torque usaully has lower BSFC's then rest of the rpm curve because that's when the engine is usually most effecient....thus the peak torque.

My 500 EFI with Cam similar to a Crane 741, 315 cnc AFRs, 9.6:1 JEs made 572hp @ 5400.
BTW was a 509

The intake was prob costing you some power. A full cnc head with that cam, shoulda did a little better than that. The 525 almost makes that with similar cam, cast edelbrock heads and less compression.

Either way still a big gain from stock 500EFI. The OP engine has as cast 305 heads

MT , Different Dyno SAE standards, but that was another thread. Regular 607 Standards and would be 600 plus/minus a few.

Anyhow, well known, looking for 600+ time to move on to something else. Holley Single Plane EFI intakes get nod by many at this point.

I was also correlating it to the High AFR's that is saying that it is lean. Almost stoichiometric burn.

Me comprendo.

Issue with the A/F readings on this sheet along with a million other sheets that the dyno does not read A/F Ratio from wideband is that they are wrong. Suks huh ?

When dyno's don't use a wideband they calculate A/F ratio from air entered thru the Airflow Meter Hat vs the fuel going thru the fuel flow meter.

Not exact by any means. Many dyno's I have been at with both have showd Wideband reading of 12.8-13.0 while the Airflow Meter Vs Fuel Flow Reading showing well into the 14.0's.

Even though widebands can throw you for a loop once in a while , this really shows how important Widebands have been in all our lives.

FYI: I am assuming his #'s are not wideband because I mentioned it earlier and was not told otherwise #1, and #2, who would leave a dyno seesion with those #'s. LOL.

I would like to mention, while on the subject of BSFC's, be very warry of other dyno sheets floating around internet land where all are in the .300's. Very, very good chance it's because of inflated power #'s.

Remember, BSFC is derived from how much fuel per horsepower an engine uses. It is a measurement of effeciency only. If the fuel use remains the same but the HP magically is up, the result is very low and quite unobtainable (in the real world) BSFC's.

The air/fuel numbers were calculated. Good catch sb. A close eye was kept on egt's and we kept jetting up until we did not gain any power. On this dyno mid to high 13's seems to be the sweet spot for power on bbc's and equates to low 13, high 12's when measured with a wideband. I have the wideband and bungs ready for the tails to fine tune it in the boat. I'm pretty confident the actual air fuel in the boat will be very close to mid 12's.

Jammie avg. egt,s @ 1468 seems a bit tall, yes ? __ did you guys try 32* on the clock?

No, by the time it richens up into the 12.4-12.8 range egt's are going to drop 100* or more. Lowering timing will increase egt by starting the burn later and causing the burn to still be on going while the exhaust valve is opening. Could go to a -8 plug but I prefer 7's and running 93 octane

so the 1468 avg. is not the temps on the best run, what was the avg. you ended up with thanks. 7 lbs fuel on the posts correct ? the 8 plug could help. make sure Mr. dyno runs 93 don't let him cheat. lol

dyno water temps 140+ he's fresh water cooled @ 155 +- so will he pick up a few hp

7lbs of fuel pressure, egt's just broke 1400 at the top end of the pull. I don't have the sheet in front of me but I think it was 1370? At peak power.

Did you try 35 or 36 deg Jamie ?

J, would have liked to see your carb. on top just for the #'s thanks cu in a bit. have fun in Fl..

I did on a 548 last week with the same heads and quench, same style piston. Power didn't go up, actually lost some at 36* and egt's only dropped a few degrees. Most of these guys fill up on the road with 93 octane which I prefer, more additives etc. less chance of getting a bad tank of fuel. So I don't mind running a little hotter plug, a little lower air fuel and the temps fall in line. Without fouling plugs or poor idling.

did the 548 near 665hp? thanks so much on 242's engine builds your good to go, now he must be careful on the sticks. any prop talk yet ? or just spin em.

Considering I never saw more than 4950 RPMs with my BBlades labbed M+ 23P 3 blades (1.36 GR), I want to see more RPM with the same prop. Bob's target was 5700. I'd be very happy with 5400-5500.

BTW - Just went 188 MPH on the MagLev in Shanghai.
[ATTACH=CONFIG]523509[/ATTACH]

Reason I asked is the shorter 4" stroke might have liked a little more timing. I am with ya on the fuel stuff. A lean marine engine is a burnt marine engine! Either way, congrats on a nice build buddy!

Did you go with a a18726543 firing order, or standard BBC?

I'm assuming if he used Bobs cam it is the 2/3 4/7 swap. I'm pretty sure they are designed off the new firing order mine from Bob were.

Yeah seems he does quite a few of those these days, but not all. Mine is as well, thx!

The 548's cam is a bit more conservative. It was originally selected for a boat with reversion issues. It made 635 and 660tq

Nice numbers. Same 305cc as cast AFR with CNC chambers?

Standard. We had a mixup - so it will be swapped next time it gets open heart surgery (I hope that doesn't happen for a long time).

What is the top end valve train refresh interval on a cam that size?

Yes same heads

My opinion 2-250 hours

im curious,what kind of performance gain can one expect to see with the swapping of the firing order in a marine application?

Mike,

From speaking with Bob regarding my cam, I came away with the understating that it's implemented (firing swap) primarily to reduce forces on the crankshaft, and that in many cases, it can add "some" HP. I think some people on the Internet have talked it up regarding hp, to something it's definitely not. I'm not quantifying the actual gains, just sounds like it's not as grandiose as some make it out to be.

Personally I was happy to learn about the reduced loads on the crankshaft. There may be other benefits I've missed, and as such I will leave that up to bob and those that are more familiar add to this.

i am not against a firing order swap but i dont buy into the claims of big hp gains.in a 10,000 +rpm pro stock engine a little gain in hp can be big but once one team realizes the gain they all do it.the guys that think they will see a noticable gain in performance in the marine world might be dissapointed .this is my opinion but im not one to buy into snake oil,i like results,not hype.

Was told smoother idle also. Dunno..

Generally you are right. The good news was since GM did the swap on the 8.1L, it made the cores cheaper and thus not much more money for someone with the standard BBC.

When it was a lot more money, it was not worth it.

It's a free benefit. Swapping the firing order evens out the load on the cam so that lifters are being pushed on opposite sides reducing core deflection. No performance gain at all, just less stress on the cam core and longer life with aggressive profiles and spring pressures

Do they sound any different with the 18726543 firing order?

Mine does not sound nearly as nasty as my previous cams. But, that also might be the grind. I really miss the crack of my old cams they were just raw. But, I didn't change cams for sound:(

Bob is correct. 4150 based 950HP Holley carb. http://www.summitracing.com/parts/hl...96-1/overview/ Works extremely well on the 502 motor. Mine started life as the carb listed, but modified. Now flow (flow tested) 1000cfm.