Here We Go: My 383 Stroker Winter Project

[greg82255]

Re: Here We Go: My 383 Stroker Winter Project

I would say your right on the bubble with your Air/Fuel ratio. I would tweek it just a bit up, and watch performance, then back down just a bit.

4600 RPM is low and that could be a couple of things - timing is off, A/F is a bit off, spark scatter from the distributor, cruddy fuel, you have hit the hp limit of the engine/hull, your tach is off, you left the anchor line out and are plowing a new trench

you will find the problem. with 93 octane, you can run a bit more ignition timing. Where is your base timing now?

I am at 8 degrees BTDC base timing, but that may be off because my timing tab is a bolt-on and could be a degree or 2 off.

I wouldn't get too caught up reading plugs. They are a good indicator of overall running condition or health of the engine but... If you were trying to judge the main jet size by reading the plugs you would need to run at WOT and shut the engine down as quickly as possible not letting it idle too much. You could for example have a perfect or slightly lean WOT condition, if you had a pig rich or poorly tuned idle circuit you could throw off the plug reading while idling back to the dock. Then mistakenly go down a jet size because the plugs look rich. Or vise verse....

Be patient, follow the instructions that came with the carb for tuning. If you haven't done so already take someone to manage the helm with you and check to see that at WOT on the boat, the carb is actually running at WOT.

Unfortunately I didn't have time to get out to the boat today. Hopefully tomorrow afternoon. What do you mean by the carb is actually running at WOT when the engine is at WOT? Opened all the way?

After timing, I'd be checking to see how far the carb air valve is openning under wot. It can be a bit "fun" but a 2nd person can slightly open the air valve from its wot position (engine and flame arrestor off). If you gain more speed you have found an issue. You have to be careful though, it can cause a severe bog if it is opened too far or too fast. At 60mph, that might send your head toward the windshield frame.

PS: Agree with Joe on the plugs.

So you mean while someone else is driving, see if I can open the carb any more than it already is? What specifically is the air valve - the valves in the barrels? I can't seem to find the manual.. looking around for it now. If I can't find it I'll get it online.

 

[Tail_Gunner]

Re: Here We Go: My 383 Stroker Winter Project

Using a slip calculator, indicates about 10% slip which is reasonable for your style boat. (assuming 23" pitch prop)

4600 is low, and would seem that your engine should be able to spin that prop better. But, if timing checks out, might want to drop back to 21" pitch. Your top speed won't change much, but your accel in any rpm range will be much better.

You are not using all of that 750cfm carb currently. Can't see that a proform is going make much noticeable improvement.

Well f your going to run with a full load of people and gas 4600 is not bad im sure the 270 cam is rated for 5200. ITs also a stilletto so it has some very aggressive cupping and should act like a 24p prop. Big question is timing and AFR...In a marine engine a nice dark brown plug would be the least i would go with... heavy loads and running a bit rich is very safe bet. Most efi tuners will run 12/1 from about 2500 to 4000 then fatten here back up to 10/1....Cold block hot piston goota watch it...

Id be willing to bet youd be much happier with a 4 blade when playing with a boat load of people..You might lose a few mph but that stroker would really hit it with the improved mdirange punch a 4 blade has..Id bet with a empty boat youd get 5000 with that 3 blade. Greg it would be intresting to note...does the stilletto lift the boat a bit higher out of the water as compared to the other props?

 

[joewithaboat]

Re: Here We Go: My 383 Stroker Winter Project

Greg,

Yea John and I are referring to the carb throttle blades actually being strait up and down At WOT. Note they can sometimes travel past straight up and down also. Not sure about referral to Air valve. Ive only messed with those carbs a few times.

I would guess the HP from 4600 to 5200 to be around 25 or more. I'm no prop expert but if you are trying to go fast id stick with a three blade. What does that boat weigh?

All engine combos are different but i would think you will end up somewhere in the mid to high 30's... 36 deg give or take for total timing advance. Checking at idle is fine and once you get a better light or some timing tape & know exactly how much the ignition provides for advance, the real number to keep track of is the total.

Running too rich is only a little better than running too lean. Both can tear up the engine, one just takes a little longer...

Oh and make sure to always set timing with a warmed up engine....

 

[John_S]

Re: Here We Go: My 383 Stroker Winter Project

Your idle timing is fine, but as Joe said need the wot timing.

The throttle plates can be checked at wot position, sitting at rest. To see the 2ndary butterflies you will have to move the airdoor out of the way. The airdoor is counterbalanced by weights, and only opens under vacuum demand through the 2ndary barrels. On Edelbrocks marine carbs there is not any adjustment to when the doors open, opening rate, etc. I have seen people report that they had issues with the 1409 and had to drill some holes in the counterweight to adjust them. http://forums.iboats.com/showthread.php?t=429895&highlight=1409+drill

 

[joewithaboat]

Re: Here We Go: My 383 Stroker Winter Project

Your idle timing is fine, but as Joe said need the wot timing.

The throttle plates can be checked at wot position, sitting at rest. To see the 2ndary butterflies you will have to move the airdoor out of the way. The airdoor is counterbalanced by weights, and only opens under vacuum demand through the 2ndary barrels. On Edelbrocks marine carbs there is not any adjustment to when the doors open, opening rate, etc. I have seen people report that they had issues with the 1409 and had to drill some holes in the counterweight to adjust them. http://forums.iboats.com/showthread.php?t=429895&highlight=1409+drill

I just glanced at that thread....

Brings back memories of messing with the air doors on the "quadrajunks"

That Holley is looking better and better LOL

Edelbrock manual here ...

http://www.edelbrock.com/automotive_new/mc/carbs_acc/pdf/carb_owners_manual.pdf

 

[Scott Danforth]

Re: Here We Go: My 383 Stroker Winter Project

cant argue with adjusting a holley.

 

[greg82255]

Re: Here We Go: My 383 Stroker Winter Project

I want to buy that Holley but $660 is a little much. Maybe if I could sell the 1410 for close to what I paid it would be a step in the right direction. I still haven't sold the merc exhaust manifolds and risers - not much interest around here unfortunately. If I can sell enough old parts to get close to the $660, then I'll probably buy the Holley.

In addition, I just took a look at the manual for my ignition and it says the total advance is between 28 and 32 degrees, but I haven't actually checked yet. If that's not enough, could that also be causing me some power?

Tail Gunner, I'm not positive, but I'd say the boat does sit slightly higher now with the stilletto prop.

 

[Scott Danforth]

Re: Here We Go: My 383 Stroker Winter Project

your voyager distributor is supposed to have 22 degrees of advance, so with base timing between 6 and 10 degrees BTDC, that would give you between 28 and 32. however that is also for a stock engine running 87 pump gas.

your running 93 in a slightly tweeked engine. you should be able to go up to about 34-36 degrees of total advance. there is not much more to gain beyond that.

 

[greg82255]

Re: Here We Go: My 383 Stroker Winter Project

Alright, I'll check the total advance this afternoon and keep bumping it up in 2 degree increments until I hit 36 and see where that gets me. Well, 36 or until it starts pinging, whichever comes first.

 

[greg82255]

Re: Here We Go: My 383 Stroker Winter Project

Alright, I'll check the total advance this afternoon and keep bumping it up in 2 degree increments until I hit 36 and see where that gets me. Well, 36 or until it starts pinging, whichever comes first.

I just got back from a few hours of messing around with the boat. I got myself a timing light with an advance dial and checked the total timing, which ended up being only 26 degrees.. I bumped the total timing up to 32 right away and gave it a go. I hit 60-61 (mostly 60, hit 61 for a fraction of a second) mph at somewhere between 45-4600 rpm. Then I bumped it up to 34 degrees and I got a constant 61 mph and quickly hit 62 on two of the runs. Everything ran great. Then I decided I would throw on the 1" open spacer that I bought and I jumped up to 63 mph at about 4600 rpm. So the spacer helped, and advancing the timing helped too.

I am definitely getting close to my top speed, if I'm not already there. If the engine makes more power north of 5000, would it make sense to go back to my 21" prop and give it a go now that the timing is adjusted? I believe I was turning 5000 and doing 59 mph with the 21 before, but the prop was damaged. I bet I could get 64-65 out of a 21" stilletto prop.

 

[John_S]

Re: Here We Go: My 383 Stroker Winter Project

Good news with the timing and spacer test. Were you able to get it to idle rpm so it doesn't slam the gears? and engine turn over fine? I estimated you are at 16 degrees BTDC at idle. Maybe you can re-curve that distrubuter. Does it have weights and springs?

You might want to put a shop tach on it to get a reliable rpm. Going faster with the same rpm doesn't make sense. Boat tachs are not that accurate.

If it is really at 4600 rpm, then I think you would like to drop down to the 21" pitch.

 

[greg82255]

Re: Here We Go: My 383 Stroker Winter Project

Good news with the timing and spacer test. Were you able to get it to idle rpm so it doesn't slam the gears? and engine turn over fine? I estimated you are at 16 degrees BTDC at idle. Maybe you can re-curve that distrubuter. Does it have weights and springs?

You might want to put a shop tach on it to get a reliable rpm. Going faster with the same rpm doesn't make sense. Boat tachs are not that accurate.

If it is really at 4600 rpm, then I think you would like to drop down to the 21" pitch.

I can get it to idle at about 850, sometimes 900 - not as low as I'd like but good enough for now. Where can I get a shop tach? - a place like Autozone? I have a Gaffrig tach on there right now - I figured it would be as accurate as any, but definitely couldn't hurt to check. The distributor is an EST - no mechanical advance. I don't think I can re-curve it. An MSD system may be in next year's budget.

 

[John_S]

Re: Here We Go: My 383 Stroker Winter Project

I have an old shop tach that is good for idle rpms (reads only up to 2K), and use an inductive tach to check high rpm. It has a peak hold function. This was only around $35 and its primary use is for rpm on my small outboards and other small engines. It is like this one: http://trailtech.net/tto_tach-hour.html

You might want to sacrifice some of that advance, so you are not slamming those alpha gears on the shifts. Try to find a happy medium until you get a new distributer.

 

[Tail_Gunner]

Re: Here We Go: My 383 Stroker Winter Project

Good news with the timing and spacer test. Were you able to get it to idle rpm so it doesn't slam the gears? and engine turn over fine? I estimated you are at 16 degrees BTDC at idle. Maybe you can re-curve that distrubuter. Does it have weights and springs?

You might want to put a shop tach on it to get a reliable rpm. Going faster with the same rpm doesn't make sense. Boat tachs are not that accurate.

If it is really at 4600 rpm, then I think you would like to drop down to the 21" pitch.

Indeed boat tachs are about as truthful as a polotician during campaign season..So far 4600 seems as far as that tach want's to run and you've jumped to 63 mph

Actually 1.50 gearing with a 23p @4600 nets 67 in theory...your showing of 63 nets 6%...Stilletto are not that good....

So lets try 4800 now that gets 10% and if your running with a load of people that's pretty much insane...empty or 1 passenger that is good..Tach time...

Just adding a spacer and getting that speed bump....Id check up on things.. they add plentium volume that is more air in the column.. maybe you do need a larger carb..dunno but if that was TBI it would be unheard of gain

http://forum.grumpysperformance.com/viewtopic.php?f=55&t=1038

 

[joewithaboat]

Re: Here We Go: My 383 Stroker Winter Project

Good to see you are getting good results from tweaking. Its not uncommon for a big small block to gain 10 hp in the upper rpm ranges by adding a 2 inch tall open spacer.

You defiantly need to figure out the RPM thing. If it wont swing that prop past 5,000 RPM id be trying that 21 again.

 

[Tail_Gunner]

Re: Here We Go: My 383 Stroker Winter Project

Good to see you are getting good results from tweaking. Its not uncommon for a big small block to gain 10 hp in the upper rpm ranges by adding a 2 inch tall open spacer.

You defiantly need to figure out the RPM thing. If it wont swing that prop past 5,000 RPM id be trying that 21 again.

No a 21 only nets 65mph with 0 silp hes has the right prop to find the sweet spot...the rpm being stated is what is important..Think of that boat like a dyno..real world dyno speed increasing and rpm dropping along with timing changes..Not plausible. Just keep tuning or tinkering until it runs out of steam. Accurate rpm level's will help you determine...your best gear ratio..errr prop size. Ohh then there is hull dynamic's....and performance traits..

Can you make a run with just you in the boat..Ive talked about lift before... the less wetted surface the faster you go it would be intresting to see if that engine can push that hull on its tail. There's a hull that has reached its limitl..anything more would be dangerous foolish

 

[joewithaboat]

Re: Here We Go: My 383 Stroker Winter Project

Greg,

The prop calculator I'm looking at says to add 1" to prop sizes if they are aggressively cupped props. I'm assuming you have a 1.5 drive, and using using 10% slip just to put some numbers in.

So a good 21, really a 22 in the calculator, gets you 65mph at 5200rpm
............. 23.............24.....................................63..........4600

Id say your tach could be correct, Try the 21 if it isn't tore up. Lets see what you get.

FYI using this calc.

http://www.rbbi.com/folders/prop/propcalc.htm

 

[greg82255]

Re: Here We Go: My 383 Stroker Winter Project

Unfortunately the 21 is all dinged up from earlier - ill have to get it repaired before I can do the test. I may just buy a different used one and sell mine as a repairable prop. The previous owner of my current stiletto prop said he was getting very low slip #s. I'm not sure exactly but I think it was 6% - to the previous owner, I think you are watching this thread so feel free to correct me if I'm wrong.

Joe, I have also heard you have to add inches of pitch to account for aggressive cupping. My uncle used to run a laser II and said to add 2" of pitch when doing the slip calculation.

Tail gunner - the 63 mph was with just me in the boat but I definitely have more hull in the water than in that picture. At 4600, 63 mph nets 6% slip with the 23" prop. The tach could be accurate. I'm definitely going to try another 21" and see what happens - certainly couldn't hurt to try it.

 

[Tail_Gunner]

Re: Here We Go: My 383 Stroker Winter Project

Greg i would hold off buying a new prop. Validate your rpm first.. it is off...you cannot increase speed without a rpm gain and 4800 sounds about right. A 21p prop may be in the cards with accurate rpm reading and under a load..However a 21 cannot reach 63 and that speed needs to make sense...Your rpm is very constant and your speed is climbing that does not work for boats....Tuing up a engine does not tune up a prop...and the prop seems to be more effecient all the time with timing changes..
http://www.go-fast.com/Prop_Slip_Calculator.htm

There is a calc that will let you play with variables...you will see something is a miss. and a 21 does not fit in...I really wish i could source the dyno curves for the 270 the whole ideal is to find out where the tourqe curve falls and there are no more gain's..Psst that's the secret to propping.. tourqe rpm and speed where does it all converge and 5200 may not work for a stroker,,By the way i have that cam in a 4.3 and 5000 is the sweet spot..that boat up above is my tub. 19' 3000lbs 8' beam not much difference that yours.

 

[greg82255]

Re: Here We Go: My 383 Stroker Winter Project

Greg i would hold off buying a new prop. Validate your rpm first.. it is off...you cannot increase speed without a rpm gain and 4800 sounds about right. A 21p prop may be in the cards with accurate rpm reading and under a load..However a 21 cannot reach 63 and that speed needs to make sense...Your rpm is very constant and your speed is climbing that does not work for boats....Tuing up a engine does not tune up a prop...and the prop seems to be more effecient all the time with timing changes..
http://www.go-fast.com/Prop_Slip_Calculator.htm

There is a calc that will let you play with variables...you will see something is a miss. and a 21 does not fit in...I really wish i could source the dyno curves for the 270 the whole ideal is to find out where the tourqe curve falls and there are no more gain's..Psst that's the secret to propping.. tourqe rpm and speed where does it all converge and 5200 may not work for a stroker,,By the way i have that cam in a 4.3 and 5000 is the sweet spot..that boat up above is my tub. 19' 3000lbs 8' beam not much difference that yours.

Just spent a week in lake winnipesaukee up in NH on an island with nothing but the boat.. upset that I am back home now. I didn't mess with the props while I was up there - just wanted to have some fun. Now that I'm home I'll pick up a shop tach and go out and see what the RPM really is. I'll post some #s in a day or 2 once I get out there.

By the way, just an observation... Everyone says that adding a thru-hull exhaust doesn't add anything but noise on a small block. I'm not sure if it's different with a stroked engine, but when I was running WOT with the exhaust closed, I couldn't get above 61 on GPS. Then I opened the thru-hulls while at WOT and instantly jumped up to 63 and gained something like 200 rpms. Just a thought.