Edelbrock 600cfm

[opunui]

Would the edelbrock 600cfm carb be big enough for the crusader 454.I mean not starving but real economical? my quadra jets are history.Thanks

[John F.]

I've had the Edelbrock 600 cfms on my 454s for 5 or 6 years. They seem fine. From what I remember, 600 cfm can handle alot more flow than my 454s at their hp (310 or 330? don't really know) need. You'll need square-bore adapters for your manifold.

John

[DRIFTER31]

I would think so but at wot it may not be quite enough. The secondaries are operated by how much vacume the engines pulls so at cruise it will open up to what the engine needs and you can also read the plugs after a long run at cruise and change the metering rods/jets for more fuel if necessary. Good carb.Troy

[John F.]

I spoke to a marine carb place, Summitt Racing, and e-mailed Edlebrock. The marine carb place and Summitt said to go with the 600cfm for my application--lots of time at idle (trolling) and at steady 2800-3000 rpms. Summitt also told me that that as a rough estimate the 600cfm was enough carb for up to 500 hp. Edlebrock emailed back that I should get the 750 cfm--no explanation. My 454s go to WOT once every few years. If I were building a go-fast with BBs, then maybe I'd go for the 750cfms.

[DRIFTER31]

You may want to question their reason for 750CFM. heres why The secondaries open by vacume and the smaller carbs primary holes will possibly allow the secondaries to open faster or at an earlier RPM. The Holly style is nice because YOU can control when the secondaries open by purchasing a spring kit for the secondary vacume diafram and just install a stronger spring. Reading the plugs while you play with the springs is a must.

[ScottD]

I would rebuild the Quadra-jets. The small primaries and large seconderies are a great fit to a marine application.
don't change a good thing.

ScottD

[Carl]

Scott is right, the Quadrajet may not be as user friendly or easy to rebuilt like the Carter/Edlebrock are, but they have great fuel flow for the higher rpms and efficient at low rpms. I changed out my Quadrajet to a Carter/Edelbock on the vette and really lost the extra punch and efficency at low cruise. I could have tuned for either but just decided to keep in middle.

I put Edlebrocks on my 440's, 330hp and had to really tune them in as they burnt overly rich and secondaries opened way to early. Good thing is you just buy the kit and swap out springs, metering rods and jets then take it for a good run, read the plugs and tune again till it's right on.

[scot]

Go with 600cfm.

The larger the bore in the carb, the lazer the engine will be. Meaning a larger bore carb will result in less velocity of the air/gas flowing through it. Think of it this way; a small hole trying to move 600cfm through it will have higher charge velocities than a large hole trying to move the same amount of air. The amount of air needed is dictated by the engine's displacement (454 cu inches in your case), and how much air can flow through a given displacement is dictated by the lift of the valves, and the efficiency of the ports in the head and manifolds.

The higher velocities of the charge will make the engine more responsive at low to medium rpms. The air flow moving through the carb "signals" the jets on how much fuel to mix into the flow....so the signal gets weaker as the bore size increases, resulting an unresponsive engine, compared to a carb bore that provides a stronger signal to the jets.

A strong signal creates good low end torque, which is what puts a boat on plane.

Always run the smallest carb you can get away with, and still feed the engine to it's potential. I "may" question Summit about 600cfm being good for 500hp, but I would at least say that 600cfm is good for any engine under 450hp. But considering the amount of stuff as I have purchsed from Summit I sure hope they are right most of the time!

Although I love my Eldebrock 600, Scott is right about the primary bore sizes on the Q-jets. They work very well providing low end with the small primaries, and top end with the huge secoundaries.

Now go do the right thing!

[Capt. DQ]

All good points on the carbs, but consider this point that will make the most difference.

I use to have 87-model Crusader 454's in my B31 until I switched to deisels and best thing you can do, is to change the intake manifold's out to the Eldebrock T-2 intakes and go with the Eldebrock Marine 750cfm carb that will out perform the others when it is matched up with the Edlebrock intake. Edlebrocks tech department will confirm this point.

If you look at your original intake ports on your intakes, the ports are not matched up very well to heads, leaving edges that protrude and are not matched up, in-turn causing fuel not to flow smoothly from the intake to the head.

If you have Flow-Scans on your boat, you can install either the port or starboard engine with one of the new intakes and carbs and leave the other side like it is, and you will be able to see the difference by the flow-scans while doing a sea trial and if your props are proped right. You will be totaly suprized at what your data will read. You will also notice how much smoother your engine runs @ different rpm's.

R,
DQ