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Camshafts

Double A

Member
i’ve been reading and gathering info from here for about 2yrs. i have a Predator haul 13’,O 360,3 blade 68’’excalibur prop. Kinda new to airboats but not. Back in 1974 my dad ran a gore with a io360 and can’t remember what my uncle ran gore haul Lycoming ??? Anyway read a post on CM DD V.S. AC got me thinking (now there’s some trouble) you have a wide range of performance parts for CM but a limited parts for AC if I’m right? or really deep pockets. the camshaft is what dictates power and where it comes in at. But from what I’ve read phase 3 is about the best we can get? would like to hear back watch you think?
 

Slidin Gator

Well-known member
DA,
What do you plan to do with your boat? Racing, dry ground, general riding with some scattered full power runs?

The primary limit to your ability to make power is the ability to maintain cooling/temperature. Liquid cooling is definitely more efficient at pulling heat out of the motor. Air cooled aviation is definitely simpler but requires attention to proper cooling to add power.
 

Double A

Member
General ride with scattered runs. But sometimes curiosity gets the better of me. I believe it’s better to have and not need than to need and not have. The AA is for the 1931 truck I‘ve done.top speed new 45 mph,but now 65mph. It took some time And out of the box thinking.model A engine had to make way better than 40hp to pull it off. Detail,details,details you have to make all your power between idle to 3000 rpm for the OD kinda like AC with more prop. but with out the cooling issues,that you mentioned,Thanks for bringing that up,more to think abouto_O. and anything else you can think of. Not looking to build a fire breathing monster but don’t want to leave anything on the table. I see they have a roller cam now was wondering about rockers also? Has anybody tried Weber sidedraft carbs? Instead of the updrafts? the boat came with electronic ignition. The down side to that is no battery no spark.then there’s AV VS SV does the av out flow the sv? Closer balancing specs? CC the Combustion part of the cylinder ? And keeping it cool or better cooling?
 

John Fenner

Well-known member
Ok, to start, invest in a set of forged 10:1 pistons from combustion technologies or diamond you will need to know your bore sizes, all standard or P.010 or mix matched bores, if mix matched have the others bored to match, a proper valve job is in order as well.
Next, need to determine what camshaft is in it, is it an integral gear or a bolt on gear, using a degree wheel to find out what the lobe centerlines are, and even find the profile If that curious, you want at least 114° which should be 10° advanced, if not, a cam grinder is in order to get the profile and advance that is desired on integral gear or get a bolt on advanced gear to adjust.
Now on to the angle valve and parallel valve question, angle valve heads are heavier, no real flow differences to speak of just weight.

Induction, if you want to omit that glorified updraft tractor carb from the sump, study how an O-470 or even a Franklin intake log system is designed, build a plenum out front to hold a 350 CFM 2V holley carb, a bit of tuning and it will be very efficient.
 

Slidin Gator

Well-known member
the boat came with electronic ignition. The down side to that is no battery no spark.then there’s AV VS SV does the av out flow the sv? Closer balancing specs? CC the Combustion part of the cylinder ? And keeping it cool or better cooling?
Unless you plan on hand propping, electronic ignition will fire long past the point any battery will spin the motor over. I've gone a whole weekend without an alternator with no issues. More information on the Pacemaker at this link.

Pacemaker Install

As John says, make sure all 4 bores are the same is about the limit to balancing that most folks do. Most also remove the crankshaft counterweights, they can fail under hard acceleration. These engines only run to 2,800 after all.

4 cylinder engines do not generally have cooling issues like the 6 cylinders, but you want to know what everything runs at. Get an IR temp gun and shoot the cylinders at the spark plug bosses (top and bottom). Check it immediately after a hard run with the engine idling. Add 50 deg higher for actual cylinder temp. 400 F max for maximum life, 500 F Max. is Lycoming CHT specs.
 

Double A

Member
Thanks for your thoughts and John’s also. Sorry took so long to get back,work life ect.ect.That and after further study of the #3 cylinder I hit the ceiling🤬🤬. #3 cyl. And #1 had a noise from the intake #3 way worse than #1.how bad? Bad enough to feel it with your fingers slapping the seat. So started checking compression on the cylinders #1-65 #2 80 #3 70 #4 65. Anyway back to #3 thought maybe lifter? Tore apart cleaned checked nothing stuck or sticking,checked valve lash on all other cylinders that all checked out. Noticed there where 2 different outer springs listed hmm.one white one blue ok,problem child #3 had white not blue so bought a new spring. While making a spring compressor had to take off rockers to center up bolt and cup for spring. Intake rocker looked normal exhaust rocker has chip/chunk missing where it rides on valve 🤬🤬. Now more checking looking more hitting the ceiling. I was told one thing but sold another,so the start of this season is shot.can’t do any more until I get the cylinders off check them and see which ones are good and which ones get trashed. Did the IR temp check in the shop and after a tour (dry) in the back yard 350* ish F. I try to eliminate the obvious things first then keep digging until I find out what and why cause the problem.
 
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