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tooslow
01-27-2002, 06:20 PM
I recently built a 383 for my 21ft ultra open bow. Specs: 383 Eagle crank, 5.7" rods, KB pistons, zero decked. Dart Iron Eagle heads 200cc runner, 64cc combustion chamber, comp cams roller tipped rockers 1.5 to 1 comp cams xe262h cam-218,224 duration @.050"-.462,.469 lift. Edelbrock Rpm air gap manifold, Holley 750 vac secondary carb, stock ignition, EMI Thunder exhaust out the transom. Problem is the motor doesn't do much more than stock 350 did. It has more on the bottom end, but boat still only does about 54mph at 5100rpm turning 22 four blade stainless on alpha 1.5 ratio drive. Any suggestions?? I'm considering pulling the motor and drive and starting over with a big block, but only if absolutely necessary to reach 65mph.

Havasu Hangin'
01-27-2002, 06:30 PM
Man, that's almost my exact motor. I went with a little more cam, and smaller heads. From my old 350, I picked up around 10MPH. I have a bigger (23'), heavier (a couple tons) boat.
Was the engine dynoed? Where is your timing set?
Were those speeds GPS? You're speed shows about 22% slip.
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tooslow
01-27-2002, 06:58 PM
the timing is about 36 total, the figures are from gps. I don't know what the problem is. The motor wasn't dynoe'd but I am considering pulling it and having it professionally tuned. Also, the boat didn't show much difference from a 21 alum 3 blade to the 22 four blade, only a few mph
[This message has been edited by tooslow (edited January 27, 2002).]

Havasu Hangin'
01-27-2002, 07:24 PM
Mine is at 36 total, as well. Something is definately fishy. A couple thoughts...
22% is high for a 4 blade- not good. Are you trimming a good amount to carry the nose?
What is the rev limiter on that ignition. Are you against it? That cam should pull peak HP around 5,000RPMs. Have you tried a bigger prop?
What comp pistons did you put in? 68cc heads? Are you running AV gas?
Is the carb "out of the box"? Are the secondaries opening up?
As a point of reference, I spin my 23" 3-blade a little over 5,000RPMs. With the right tune up and prop, you should definately be pulling on me...
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tooslow
01-27-2002, 07:42 PM
The 4 blade was actually a bravo prop, so the diameter is bigger, I'm not sure of the rev limiter on that ignition, but I'm not hitting the limiter, the carb is out of the box, I've yet to try rejetting it, but the secondaries are opening. the heads are 64cc, the pistons are quench style but i'd have to find the paper work to find out what dish they are, the compression ratio worked out to about 9.6 to 1. I don't know what the problem is. Those figures are at fully trimmed up position, no I don't run av gas
[This message has been edited by tooslow (edited January 27, 2002).]

77charger
01-27-2002, 08:11 PM
That sounds like a healthy small block and cam numbers are welll suited for that rpm range.I would play with the jetting,if not go to a bigger cam next step up.at a rough guess i would say you motor i making at least 375hp.

Havasu Hangin'
01-27-2002, 08:13 PM
Well...hmmmm...if the ignition and fuel are curved OK, then my unprofessional instinct tells me you are running out of prop. Maybe a bigger SS 3-blade, with some bow lift, so you won't have to trim up so much (22% is unacceptable, and has nothing to do with the engine).
That hydraulic cam is fairly conservative, and you might be pulling past your peak HP. A bigger cam would give you more top end. My hydraulic roller is (222/230; .509/.528) and pulled peak HP at 5,200RPMs (457 HP).
As Kevin knows, my out of the box Holley was giving my builder fits. He kept jetting up to get the exhaust temps down, but it kept falling on it's face. After I had the carb and timing curves set, it came alive.
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tooslow
01-27-2002, 08:40 PM
I agree with your prop advice, my only concern is that with the 22 four blade, when trimmed up the boat chine walked a bit, I'm not sure whether or not more lift would magnify this problem. Do you know what your builder did to fix your carb problem. Also, how do I get my prop slip down- is just bow lift that affects slip. What exact prop are you running, so I know what to look for. I considered running two steps up from my current cam to the xe274h just to see what happens. Did you do anything to the bottom of your hull? I have read that if there is hook in the hull you can add hp with no gains, but haven't yet checked for hook in mine..are you also running an alpha drive?
who dyno'd your motor for you?
[This message has been edited by tooslow (edited January 27, 2002).]
[This message has been edited by tooslow (edited January 27, 2002).]

Havasu Hangin'
01-27-2002, 09:12 PM
Originally posted by tooslow:
I agree with your prop advice, my only concern is that with the 22 four blade, when trimmed up the boat chine walked a bit, I'm not sure whether or not more lift would magnify this problem. Do you know what your builder did to fix your carb problem. Also, how do I get my prop slip down- is just bow lift that affects slip. What exact prop are you running, so I know what to look for. I considered running two steps up from my current cam to the xe274h just to see what happens. Did you do anything to the bottom of your hull? I have read that if there is hook in the hull you can add hp with no gains, but haven't yet checked for hook in mine..are you also running an alpha drive?
who dyno'd your motor for you?
If you trim up too high, then you are now pushing downward more, and forward less. Also, the prop will begin to get close to the surface, and may lose bite. This will cause slip. If your prop has bow lift, then you don't need to trim as high to carry the nose. More lift would not magnify the problem, you just need less trim. Although the Bravos are supposed to have some bow lift, I think you need to tinker.
For example, with your current prop, if you were to get your slip down to 10% (acceptable level), you should see 63.8MPH- that has nothing to do with the engine.
As for my engine, I sent my carb and dist to a performance shop that specializes in carbs. They did a 830 conversion, cross-drilled the plates, installed a cross tube (instead of the "j" tubes) installed different secondary springs (purple .063), re-jetted (75/86), new nozzle (.033), and power valve (6.5). Without these changes, the engine would continue to pull and fall- I suspect trying to open the secondaries.
I have a Volvo outdrive, and I am running a Hill SS 3-blade Turbo. As for hook, if you look under the boat, you'll be able to see it, if you have a problem. Take a straight edge to the last few feet. Over 3/16" gap is unacceptable.
With those heads, you're engine will definately like a bigger cam. If you're not thinking about a hydraulic roller, I would reconsider. They have steeper ramps, so more flow- those 200cc intakes will like more flow. However, any bigger than mine, and the idle will kill your outdrive (mine idles at 800-1,000 right now...tough on the shifting)
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tooslow
01-27-2002, 09:18 PM
Thanks for all the advice, it looks like I have a little work to do in order to get this thing right. I was unclear on slippage, thanks for the enlightenment. My block is an early style, how hard is it to retro fit to a roller cam. At this point, I just want to get it right in time for the season. Do you recomend having the motor dyno'd. If so do you know of any reputable shops in So Cal?

Havasu Hangin'
01-27-2002, 09:48 PM
Retrofitting a roller cam is pretty easy (mine is a retrofit). You don't need to machine the block, the retrofit lifters are linked together to keep them from turning. Also, a small bearing is placed in front to keep the cam from "walking". The most painful part is that it costs about $200 more for the kit. I went with Crane.
Dynoing the engine is always nice because you can rest assured that you got the best tune up- one less variable. However, it is expensive. Most shops want $500 just to put it on. I guess it depends on your budget, and how much you are willing to pay to get that peace of mind.
I used to live in HB, and Phaff (714-894-7573) was always highly recommended (but expensive) for dyno work. Maybe someone else can chime in on alternatives.
C&J Engineering did my carb- they are in Whittier (562-946-1388).
I think you got all the right parts- you just need to tweak some areas.
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tooslow
01-27-2002, 09:58 PM
Thanks Again Havasu,
If I see you on the lake, I owe you a beer, hopefully all your help will make me a happier boater... What kind of boat do you have.. Mine is hard to miss. The bottom is black and the top is green and grey.. Hopefully I'll be able to keep up with you by the time summer is here.. Thanks

Havasu Hangin'
01-27-2002, 10:05 PM
Originally posted by tooslow:
What kind of boat do you have...
Hey partner...no worries...that's why we hang around here. I hope you stick around and let us know how it turns out. Us SBC guys gotta stick togther...
Under my profile, under "homepage", there is a link to a page that has a picture of my boat. I'll be more than happy to put away a cold one with you...
...and I expect by summer you'll not only be keeping up, but passing me!
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[This message has been edited by Havasu Hangin' (edited January 27, 2002).]

tooslow
01-27-2002, 10:25 PM
You're boat is clean, nice job. I used to have a 23ft Omega, but it wasn't nearly as nice as your boat is. Did you do all the paint work yourself, and who did your interior?

Havasu Hangin'
01-27-2002, 10:32 PM
Originally posted by tooslow:
Did you do all the paint work yourself, and who did your interior?
Not bad for an '81, eh? The gel was done by Quality Boat Repair in Riverside, and the interior was done by a friend of mine, who is now working for DCB.
She's getting some stereo upgrades and power steering as we speak. BTW, make sure your steering is solid, as you are getting up there in speed, and any play will be bad news- maybe even cause chine walk.
Yep, the HH Tugboat is old, but she holds a cooler with the best of em...
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waterbum
01-29-2002, 06:48 AM
My opinion is I suspect the secondaries are not opening fully.A small block marine stroker does not spin enough r.p.m.'s to flow enough c.f.m.'s to pull open the secondaries on a 750 in the out of the box configuration.My advice would be to either go to a lighter spring so it will take less vac.to let her open or go to a mechanical secondarie(my personal faverite)I have a Nickerson on my stroker.850 baseplate,750 mainbody,flo's 930c.f.m. Really woke my beast up.You do have an advantage with your Holly because you can adjust when your sec's open. I'm still stuck with a brand new Edelbrock 750 that has no adjustments on sec. control.I need someone with a B.B. to buy it.Hope this info helps you get dialed in.Have fun.Hi H.H. The Bum http://free.***boat.net/ubb/smile.gif