mrhorsepower1

The majority of the time, yes engines will run richer in the boat due to lack of air flow. I am just relaying information from our 50 years building performance engines, that's all. Every engine builder will have his/her own way and ideas on things. You know that. The spotting your seeing is most likely condensation. If your not running a oil thermostat, you may want to consider it. I have seen it on other engines that have come in the shop.

J-Bonz

Dean,
What are you using to calculate A/F ratio, O2 sensors or a Gas analizer?
Jus Curious,
Jr.

Heres some standardize Testing pics fo ya.............

RumRunner

Also, remember a number is just a number!

Everyone's equipment will read a little different.

There are also other variables such as type of exhaust system (wet, dry, pipe lengths, etc.) bung placement, etc.

On any application you need to find where it runs best on the specific combination.

As mentioned there are different ways to measure AFR.
- Mathematical (lbs of fuel vs. lbs of air entering the engine)
- WBO2 sensors (Which can give you false readings in certain circumstances)
- 4 or 5 Gas Anylaizers (One of the most accurate ways but not the quickest)
and a few others.

J-Bonz

[QUOTE=RumRunner;2100175]
- 4 or 5 Gas Anylaizers (One of the most accurate ways but not the quickest)
QUOTE]

Aint that the truth, they are slooooow!!!

RumRunner

[QUOTE=J-Bonz;2100204]Too slow for most people to use for acceleration testing, but if you're doing steady state stuff they're great

I try to use that to back up what I'm seeing from my lambdas when doing calibration work.

HARDCORE A/O

Thanks again for sharing the expertise gents.
Smitty (as usual:-)) gave me something else to think about: oil temps. I've been seeing an oil temp of around 260 degrees after a long WOT blast without an oil cooler (running N/A -the sensor is mounted in the oil filter boss on my Dart Big M block). I didn't think this was too bad a temp (is it?) but - it's no longer an N/A engine, so...
I'm in the procees of installing a Rex Marine 3" "combo" oil cooler. I don't plan to use an oil thermostat unless it is necessary, but I can understand why we should - much like the rich vs. lean argument, too cool is probably worse than too hot, cause water don't really have a lot of lubricity and it don't mix well with oil (and it cause "age spots" in your motor!) Oh well, just one more friggin thing to worry about..
Thanks again for the insightful info...
to be continued...

articfriends

I also felt the spotting was caused by condensation,I run a 3x18 oil cooler with a thermostatic bypass but I get alot of condensation in my motor from running it at 100 degrees,I think the oil (which I change every 12-14 hours/2 weekends of running) ends up with some condensation from this which evaporates in the crankcase thus the spotting on the cylinders below where the rings run,more prevelant on the sides of the cylinders from wristpin down where nothing rubs on the cylinder. It wasn't rusted or pitted and still looked good where the rings ride,just is strange looking. On a side note I am having teenier racing install a set of your extra head bolt bosses on my merlin 2 block,it was lifting the heads enough to push the paper out near#7 and going to mls gaskets,the only thing left sealing the cylinder was the fire ring,it was one of the cylinders that still had perfect compression and 4% leakdown too which I could hardly believe,Smitty

HARDCORE A/O

I know what you mean, something as simple as a flame arrester can seriously affect the A/F ratio, and lots of boats have restrictive engine room ventilation - but not mine - I have a Harwood Pro-Drag hood scoop on my hatch so I don't think that'll be a prob. The problem for me is going to be dealing with jetting the carb in that POS Vortech Box. Man, what a PITA that is!

BTW: Smitty. I had to ditch the inlet screen on my M-3 though (for now), to get the inlet to clear the water elbow coming out of the riser on my Gen III's. I also reconfigured the flow of water through the manifold to eliminate the lower (manifold) elbow and re-routed the hose to the back of the manifold but the screen still can't fit. I think you run a similar setup and I recall you saying that you had to modify your inlet screen to fit. I can't figure out how to do that without going to a custom (longer) S/C bracket to clear the manifolds altogether. How'd you do it?

articfriends

My inlet screen interfered so bad with the fittings on the stainless marine3 manifolds that I pulled the supercharger housing off the main body of the supercharger and trimmed 3/8 or 1/2 inch off the aluminum casing then cut 1/4 of the bottom of the inlet screen and horn off to get it to clear,its less than ideal but it still directs the flow into it for the most part and keeps debris out. If I can find a file photo I'll post it,Smitty
you can give me a call at 989-823-7319 if you want a better explanation

RumRunner

Keep in mind that a Pro-Stock style scoop can actually hurt you as much as it helps! If the air is not directed properly to your inlet, it can actually run away from your inlet and decrease air flow. On a drag car we can change the shape, and ending spot (internally) of a scoop and change a cars MPH, and jetting drastically.