Cold air intake

[Alpheus]

Re: Cold air intake

who are you quoting? I don't see that...

Post # 5

 

[Tail_Gunner]

Re: Cold air intake

I will be the first to chase hp gains in a 4.3...Been there and still trying..
But when you try to do slight mods on a boat to get gains remeber this...Pushing a car to 60mph is one thing...Pushing a boat to 60 is another...Simple experiment..@ 60 mph let off the gas in your car..take careful notes to measure the distance traveled before coming to a halt...Now get in a boat doing 60mph ...again take special notes as to how far the distance traveled to a stop...With one caveat..take special care to not let your head go thourgh the windsheild on the boat when you cut the power..

It takes a huge amount of tourqe or HP to move a boat on plane..small gains are just almost meaningless on a boat..But tinker away its part of boat ownership i firmly believe that now...

 

[bruceb58]

Re: Cold air intake

Adjusting your trim is way more significant to your speed than any spark arrestor you could possibly buy.

 

[wca_tim]

Re: Cold air intake

my engine, before putting the afr heads on it, would pick up 300-400 rpms with the gaffrig flame arrestor that's on it versus the stock one. I did it more than once to be sure. Required a step richer jetting as well. The stock flame arrestors for most boats are restrictive. note that often times when you change something like that, to realize the performance benefit that might be possible, you may have to adjust the fuel mixture (ie jetting). when you flow more air, you need more fuel...

Just my own experience. My corvette really benefited from a cold air intake... this post has me thinking...

 

[John_S]

Re: Cold air intake

my engine, before putting the afr heads on it, would pick up 300-400 rpms with the gaffrig flame arrestor that's on it versus the stock one. I did it more than once to be sure. Required a step richer jetting as well. The stock flame arrestors for most boats are restrictive. note that often times when you change something like that, to realize the performance benefit that might be possible, you may have to adjust the fuel mixture (ie jetting). when you flow more air, you need more fuel...

Just my own experience. My corvette really benefited from a cold air intake... this post has me thinking...

Yes, I certainly agree that you would have to adj the carb to get those type of gains, or it was way off to start with.

I'd bet that even before your afr head change, we are not talking a stock engne?

What you are suggesting is that the new flame arrester increased cfm by 30 or 40, which sounds reasonable. What doesn't seem reasonable to me, is the calculation of the flow of a stock arrester to lower the carbs cfm that much. It only takes about 500cfm for a 350 @ 5000 rpms at 100% eff. So, if you only had a 600cfm carb on it or larger, says the stock arrester could only flow 500 max. Or am I missing something?

 

[wca_tim]

Re: Cold air intake

Yes, I certainly agree that you would have to adj the carb to get those type of gains, or it was way off to start with.

I'd bet that even before your afr head change, we are not talking a stock engne?

What you are suggesting is that the new flame arrester increased cfm by 30 or 40, which sounds reasonable. What doesn't seem reasonable to me, is the calculation of the flow of a stock arrester to lower the carbs cfm that much. It only takes about 500cfm for a 350 @ 5000 rpms at 100% eff. So, if you only had a 600cfm carb on it or larger, says the stock arrester could only flow 500 max. Or am I missing something?

no, not stock... ported world products sportsman heads. and a 383 with 10: compression, edelbrock 750 carb, freel flowing exhaust, etc...

the biggest point I wanted to get across is that many times when we make a change to en engine that is dialed in, and assume it didn't help or even hurt, performance it's because we fail to consider that we may need to adjust the tune to take advantage of the change.

I started with the combo above, that had been jetted carefully, went to a competition ported afr195 heads, a holley 750 dp with a proform body and quickfuel base, an airgap rpm intake and picked up around 100 horsepower (ie over 10 mph with same drive, etc...) once the jets were dialed in. and that was dropping compression to below 9:1 (I anticipated a blowed in the future of this particuler engine). It likes less timing now... and has a lot more power from idle up to 5500 rpms (approximately where I target wot when propping).

bottom line - always look at a single mod in terms off everything else in your setup - if you've sent the time to tune what you have carefully, you'll likely have to adjust to realize possible gains... in my experience...

 

[Aloysius]

Re: Cold air intake

The stock flame arrestors on mine shrouded the primary side, where the choke extension on the top is. The steel mesh was restrictive, and the flow into the carb was compromised. A restrictive filter/arrestor sends a false signal to the venturis/discharge nozzles..kinda like the choke being closed..thus, more fuel is sucked out of the discharge nozzles.

Chevy heads like the vortecs, with excellent turbulence in the chambers, require less ignition advance for the flame front to spread. On our race engines, we back off the timing a couple degrees from optimum for longevity.

WCA has done everything correctly..addressed the entire package from intake to exhaust. Changing one part of the package may require recalibrating timing and fuel deliveryfor optimum performance.

 

[MCL]

Re: Cold air intake

I see that ive raised quite a bit of discussion.I do know that that a small increase in speed requires alot more hp on a boat.

Will I gain hp? -very likely
Will this be enough to be noted? -Maybe
Will it be worth the work and $? -Probably not for most people.Sadly I play more with my toys than use them,Its more for the fun than anything else.

I have no test data with my current setup,I also dont have a flame arrester for my new carb.So there is no way to tell if it will gain me anything.This will be my winter project so it will be 8 months until I can post some actual results.

Has anyone ever measured the temp in the engine compartment?