offshore to onshore
08-21-2013, 11:42 PM
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offshore to onshore
i want to start of by saying i know nothing about boating!! only cars and i have experience in chevy and big blocks. i wanted to build a 496BBC when i found a guy on craigslist selling a 496 BBC. i paid $3500. which i thought was a deal. i could not have build this motor with its parts. he actually seemed upset selling me the motor especially when i gave the the money to his wife to verify and she was pissed about the amount.
eagle stroker kit
h beam rods
probe piston
brodix rect port 305
edlebrock vick jr
quick fuel 850
all comp interanls no cam specs
he had this motor professional built. he didnt know the cam specs. he said he had it on a boat with twin impellers and that one impeller broke so he pulled the motor. i cant remember the size of the boat but i remember him commenting a long boat. i verifyed the internals when i changed out the huge oil pan and the head gaskets. i put the motor in my 73 vette with a m21 and 3.36 gears. which im currently switching to 3.70.
now my question is this... the motor seems to be slugish at low rpms (with 3.36 gears). but on the freeway she starts coming alive at 70 mph. and 90 feels like nothing to her. if i want a strong take off i have to rev the motor high then punch it. problem with that is i broke the passenger side half shaft the first month doing that, never did it with the stock 350 or the beef up 383. i have played with timing a bit have her at 24 or 26 initial. she dont misfire or ping at all. im hoping the switch to 3.70 will improve low end speed. i wish i new more about the cam. maybe thats my issue???? i have been driving her for about a year now. any comments on cam or timing?? maybe its just gearing. compression seems tight no oil being consumed. he said motor had under 5 hrs. which i thought was wierd, didnt know boat motors were measured in hours. externally and internally the motor is very good which led me to believe this motor was not a high mileage motor.
eagle stroker kit
h beam rods
probe piston
brodix rect port 305
edlebrock vick jr
quick fuel 850
all comp interanls no cam specs
he had this motor professional built. he didnt know the cam specs. he said he had it on a boat with twin impellers and that one impeller broke so he pulled the motor. i cant remember the size of the boat but i remember him commenting a long boat. i verifyed the internals when i changed out the huge oil pan and the head gaskets. i put the motor in my 73 vette with a m21 and 3.36 gears. which im currently switching to 3.70.
now my question is this... the motor seems to be slugish at low rpms (with 3.36 gears). but on the freeway she starts coming alive at 70 mph. and 90 feels like nothing to her. if i want a strong take off i have to rev the motor high then punch it. problem with that is i broke the passenger side half shaft the first month doing that, never did it with the stock 350 or the beef up 383. i have played with timing a bit have her at 24 or 26 initial. she dont misfire or ping at all. im hoping the switch to 3.70 will improve low end speed. i wish i new more about the cam. maybe thats my issue???? i have been driving her for about a year now. any comments on cam or timing?? maybe its just gearing. compression seems tight no oil being consumed. he said motor had under 5 hrs. which i thought was wierd, didnt know boat motors were measured in hours. externally and internally the motor is very good which led me to believe this motor was not a high mileage motor.
08-22-2013, 07:09 PM
#2
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Good luck friend.
Your best bet is to pull the timing cover and top sprocket and get the numbers off of the cam.
Difficult to advise without knowing the cam profiles. Do you at least know whether it is a hydraulic flat or a hyd roller or mech cam?
Those are good flowing heads, and are probably the stock 119cc chambers.
What is the piston to deck measurement? and what cc are the pistons? You need this to know what kind of compression to expect and to know whether or not you are running a squish motor or not (which will affect its need for ignition timing, and its need for octane).
A Victor Jr won't help you at ALL with the low end. If you want to use this on the street, I would advise replacing the VickJr with a RPM Airgap intake. You'll pick up 40 ft lbs of torque in the lower to midrange, and won't lose but maybe ten horses on top.
What kind of advance curve do you have in the distributor, and are you using a vacuum pot for part throttle advance - and are you running it off of ported vacuum or unported?
Bottom line is that it sounds like you got a solid motor, but it may not be matched up to your needs. A few changes and you should be good to go.
Obviously you won't be milling the block to get the deck where you want it, but you can still play with other things to move the torque curve around to where you need it.
And with that kind of power and torque, you need to upgrade ALL of your U-joints. They aren't expensive, and need to be extra beefy.
MC
Your best bet is to pull the timing cover and top sprocket and get the numbers off of the cam.
Difficult to advise without knowing the cam profiles. Do you at least know whether it is a hydraulic flat or a hyd roller or mech cam?
Those are good flowing heads, and are probably the stock 119cc chambers.
What is the piston to deck measurement? and what cc are the pistons? You need this to know what kind of compression to expect and to know whether or not you are running a squish motor or not (which will affect its need for ignition timing, and its need for octane).
A Victor Jr won't help you at ALL with the low end. If you want to use this on the street, I would advise replacing the VickJr with a RPM Airgap intake. You'll pick up 40 ft lbs of torque in the lower to midrange, and won't lose but maybe ten horses on top.
What kind of advance curve do you have in the distributor, and are you using a vacuum pot for part throttle advance - and are you running it off of ported vacuum or unported?
Bottom line is that it sounds like you got a solid motor, but it may not be matched up to your needs. A few changes and you should be good to go.
Obviously you won't be milling the block to get the deck where you want it, but you can still play with other things to move the torque curve around to where you need it.
And with that kind of power and torque, you need to upgrade ALL of your U-joints. They aren't expensive, and need to be extra beefy.
MC
08-22-2013, 07:20 PM
#3
Platinum Member
Platinum Member
Use SPICER brand U-joints - the solid ones WITHOUT grease fittings (they break AT the grease fitting under lots of torque).
And get billet caps to replace the cheap factory U-straps that hold the U-joints in place.
Bottoming out the rear suspension on a launch will also put your u-joints at the worst angle for transmitting torque at the worst possible time. Upgrade your shocks to something with adjustable compression damping, and set them so that when you launch, it doesn't quite bottom out. Upgrading your heavy steel spring to a fiberglass one is also a win-win - although I recommend getting a fairly stiff one - not the factory rated one from 80's C3s.
Changing the gears will let your motor rev more freely, but it won't save your U-joints any trouble. In fact, your deeper gear will allow more torque to reach them. While you're playing with all of this getting it dialed in - RUN TIRES WITH NORMAL: STREET TRACTION - medium hard to hard tires. Running a cheater slick or drag radial is begging all of your driveline to blow up. Get the squat and shocks and springs and ujoints sorted out before you go to sticky rubber.
MC
And get billet caps to replace the cheap factory U-straps that hold the U-joints in place.
Bottoming out the rear suspension on a launch will also put your u-joints at the worst angle for transmitting torque at the worst possible time. Upgrade your shocks to something with adjustable compression damping, and set them so that when you launch, it doesn't quite bottom out. Upgrading your heavy steel spring to a fiberglass one is also a win-win - although I recommend getting a fairly stiff one - not the factory rated one from 80's C3s.
Changing the gears will let your motor rev more freely, but it won't save your U-joints any trouble. In fact, your deeper gear will allow more torque to reach them. While you're playing with all of this getting it dialed in - RUN TIRES WITH NORMAL: STREET TRACTION - medium hard to hard tires. Running a cheater slick or drag radial is begging all of your driveline to blow up. Get the squat and shocks and springs and ujoints sorted out before you go to sticky rubber.
MC
08-22-2013, 08:20 PM
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Good luck friend.
Your best bet is to pull the timing cover and top sprocket and get the numbers off of the cam.
Difficult to advise without knowing the cam profiles. Do you at least know whether it is a hydraulic flat or a hyd roller or mech cam?
Those are good flowing heads, and are probably the stock 119cc chambers.
What is the piston to deck measurement? and what cc are the pistons? You need this to know what kind of compression to expect and to know whether or not you are running a squish motor or not (which will affect its need for ignition timing, and its need for octane).
A Victor Jr won't help you at ALL with the low end. If you want to use this on the street, I would advise replacing the VickJr with a RPM Airgap intake. You'll pick up 40 ft lbs of torque in the lower to midrange, and won't lose but maybe ten horses on top.
What kind of advance curve do you have in the distributor, and are you using a vacuum pot for part throttle advance - and are you running it off of ported vacuum or unported?
Bottom line is that it sounds like you got a solid motor, but it may not be matched up to your needs. A few changes and you should be good to go.
Obviously you won't be milling the block to get the deck where you want it, but you can still play with other things to move the torque curve around to where you need it.
And with that kind of power and torque, you need to upgrade ALL of your U-joints. They aren't expensive, and need to be extra beefy.
MC
Your best bet is to pull the timing cover and top sprocket and get the numbers off of the cam.
Difficult to advise without knowing the cam profiles. Do you at least know whether it is a hydraulic flat or a hyd roller or mech cam?
Those are good flowing heads, and are probably the stock 119cc chambers.
What is the piston to deck measurement? and what cc are the pistons? You need this to know what kind of compression to expect and to know whether or not you are running a squish motor or not (which will affect its need for ignition timing, and its need for octane).
A Victor Jr won't help you at ALL with the low end. If you want to use this on the street, I would advise replacing the VickJr with a RPM Airgap intake. You'll pick up 40 ft lbs of torque in the lower to midrange, and won't lose but maybe ten horses on top.
What kind of advance curve do you have in the distributor, and are you using a vacuum pot for part throttle advance - and are you running it off of ported vacuum or unported?
Bottom line is that it sounds like you got a solid motor, but it may not be matched up to your needs. A few changes and you should be good to go.
Obviously you won't be milling the block to get the deck where you want it, but you can still play with other things to move the torque curve around to where you need it.
And with that kind of power and torque, you need to upgrade ALL of your U-joints. They aren't expensive, and need to be extra beefy.
MC
probe piston single valve relief, .220 dome height -18cc volume. when i had the head off the piston pop out a bit at TDC
im in the process of replacing the entire front and rear suspension to prevent damage. thanks for the advise.
as far as timing is concerned im using hei with vaccum advance at base of carb. i try to only get about 10 deg from the advance and have more initial timing , i think i have my initial at 24. i feel like pushing back the initial will only make matters worst
08-23-2013, 09:32 AM
#5
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iTrader: (1)
More initial timing will help the bottom end power some, try 2* at a time. You may have to back it down some unless theres an MSD ignition on it with a start retard.
How does it idle? Really lopey like a race car, a little choppy, like stock? Performance cams in cars like a lot of timing early, but all engines are different so theres no magic #.
I guess theres no way to ask the owner who built the engine, and call that person and see if they happen to have a record of what cam is in it?
How does it idle? Really lopey like a race car, a little choppy, like stock? Performance cams in cars like a lot of timing early, but all engines are different so theres no magic #.
I guess theres no way to ask the owner who built the engine, and call that person and see if they happen to have a record of what cam is in it?
08-23-2013, 10:35 AM
#6
Platinum Member
Platinum Member
The piston DOME on those will definitely stick out of the deck. Can you recall about where the "edge" of the piston crown is in regards to the deck?
If your crown is at "zero" deck, and you use an .036" headgasket, then you are at 10.2:1 and you are running "in squish" (which is awesome).
If you are down in the hole more than .015" then you lose your squish. Or if you run a thicker head gasket you can also lose squish.
If you are running squish, then this is great.
Have you put stops in your distributor to limit the advance to 10*. If so, then your timing strategy sounds good, too.
For off-idle carburetion, you should temporarily set your idle up to 1000-1100 and adjust your 4 corner idle screws with a vacuum gauge attached. Adjust for max vacuum. Then adjust your distributor to find max vacuum at that same place - you may have to readjust your butterflys to keep the idle down to 1100 while you do this. Wherever your idle screws are, leave them there. Wherever your timing is, that is where you want it for best bottom end. It may end up at 18, or it may end up at 28. Wherever it ends up, then that should be your initial to start off with - and you may have to change out the advance bushings to keep max under 36.
The vacuum advance MAY have an adjustment screw for the spring tension in it. You want to stay close to where she pings on an uphill top gear light throttle situation, but just a bit less than that.
Again - the Victor Jr is your biggest killer. You may also benefit from advancing the cam a few degrees (but you should KNOW where it is at before you go to moving it).
If your crown is at "zero" deck, and you use an .036" headgasket, then you are at 10.2:1 and you are running "in squish" (which is awesome).
If you are down in the hole more than .015" then you lose your squish. Or if you run a thicker head gasket you can also lose squish.
If you are running squish, then this is great.
Have you put stops in your distributor to limit the advance to 10*. If so, then your timing strategy sounds good, too.
For off-idle carburetion, you should temporarily set your idle up to 1000-1100 and adjust your 4 corner idle screws with a vacuum gauge attached. Adjust for max vacuum. Then adjust your distributor to find max vacuum at that same place - you may have to readjust your butterflys to keep the idle down to 1100 while you do this. Wherever your idle screws are, leave them there. Wherever your timing is, that is where you want it for best bottom end. It may end up at 18, or it may end up at 28. Wherever it ends up, then that should be your initial to start off with - and you may have to change out the advance bushings to keep max under 36.
The vacuum advance MAY have an adjustment screw for the spring tension in it. You want to stay close to where she pings on an uphill top gear light throttle situation, but just a bit less than that.
Again - the Victor Jr is your biggest killer. You may also benefit from advancing the cam a few degrees (but you should KNOW where it is at before you go to moving it).
