Flame Arrestor Question

[xj2tow]

Is there a formula for determining minimum arrestor size?

I’ve spent a bit of time researching online but haven’t found anything.

I’ve got a bbc making a little over 700 hp n/a and I’m trying to find an arrestor that will fit under my hatch but won’t choke the engine.

Any and all help would be greatly appreciated.

 

[obnoxious001]

First you might say what sort of induction you have. Simple answer is as large as you can make fit. I don't want to tell you to remove layers of material from one, as that would ruin the coast guard rating on it.

 

[mattyc]

Do any of the arrestors advertise air flow in cfm? I seem to recall looking into this a long time ago. I remember some advertising an airflow capacity but I called one of the companies and I believe the rating was at ambient air pressure, not with a vacuum like cylinder heads.

 

[xj2tow]

It’s a carb set up with a 1050 dominator and carb spacer.

I actually sold you (obnoxious001) my old set up from heads to arrestor back in October 2020–the red Stoker. I’ve been running a large arrestor with no hatch but want to get the hatch back on.

I have a transom facing scoop and thought about taking the scoop off but doesn’t the air coming across the carb hurt performance?

 

[xj2tow]

Mattyc

I have not been able to find any cfm ratings online. I have emailed a couple companies but never received a response.

 

[mattyc]

It seems you have a baseline for performance since you've been running it with large arrestor and no hatch. Maybe pick the largest arrestor that the hatch will accomodate, and compare performance? If it runs the same and makes the same rpm then run it, if not then deal with it accordingly.

 

[obnoxious001]

It’s a carb set up with a 1050 dominator and carb spacer.

I actually sold you (obnoxious001) my old set up from heads to arrestor back in October 2020–the red Stoker. I’ve been running a large arrestor with no hatch but want to get the hatch back on.

I have a transom facing scoop and thought about taking the scoop off but doesn’t the air coming across the carb hurt performance?

If you are running the carb with nothing on it, air flowing over it will tend to draw fuel up through the vent tubes, so you are correct, not good. I would think the regular flame arrestor made for the Dominator carb flows enough, but certainly you could compare performance against your rearward facing scoop.

 

[DaveH]

the best way to really gauge if your arrestor is restrictive would be to hook up a vacuum gauge or map sensor and run it. if you pull more vacuum at WOT with the arrestor on, its a restriction.

 

[HAP]

the best way to really gauge if your arrestor is restrictive would be to hook up a vacuum gauge or map sensor and run it. if you pull more vacuum at WOT with the arrestor on, its a restriction.

 

[wet hull]

Here is mine. Fuel injected 540. Had to make shorter to clear hatch. During tuning we were sucking plenty of air. Its 2" tall at the screens.

 

[wzuber]

Here is mine. Fuel injected 540. Had to make shorter to clear hatch. During tuning we were sucking plenty of air. Its 2" tall at the screens. View attachment 1083463

Nice...who makes that piece. Is it uscg approved or just a good effective spark arrester? I inquire out of insurance co. acceptance etc.

 

[wet hull]

Nice...who makes that piece. Is it uscg approved or just a good effective spark arrester? I inquire out of insurance co. acceptance etc.

No brand name on it. Its all billet aluminum with 5 layers of metal mesh. I cut the mesh shorter and redid the bolt hardware to fit. Lools completely factory ish