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    Member TOMSS1's Avatar
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    Bob - Getting ready to put the 496 together for my Hallett 19 ss lake rig and need a bit of your sage advise prior to visiting the Dyno and finshing the boat.

    Motor is 4.310 x 4.250
    8.5 - 1
    Iron 345 Merlins with a nice port job
    C Straub roller set to head flow In. 259, Ex 271 @ .050, Lobe lift In. 660 Ex 630, 112 center
    Innercooler w B & M 420
    2 - AED 850s
    Dry Headers
    AV gas
    and your favorite....a Mallory Mag, just like a hillbilly from north of here

    Blower overdrive and Timing starting point?

    Oil cooler or not ?, Not sure it will clear my t pan but I will make it work if you think I need it

    Valve Covers have oilers, should I plumb them?

    Carbs are boost referenced, The Pro Systems Carbs on my Hydro arent and according to Pro Systems at under normal boost you dont need to, Can you explain?

    I have a shorty Glide In a past post on transmissions you recommended not bracing the back of the trans, Can you explain?

    As always, thank you very much for your help. It is appreiciated, Tom

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    gn7
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    Quote Originally Posted by TOMSS1 View Post
    Bob - Getting ready to put the 496 together for my Hallett 19 ss lake rig and need a bit of your sage advise prior to visiting the Dyno and finshing the boat.

    Motor is 4.310 x 4.250
    8.5 - 1
    Iron 345 Merlins with a nice port job
    C Straub roller set to head flow In. 259, Ex 271 @ .050, Lobe lift In. 660 Ex 630, 112 center
    Innercooler w B & M 420
    2 - AED 850s
    Dry Headers
    AV gas
    and your favorite....a Mallory Mag, just like a hillbilly from north of here

    Blower overdrive and Timing starting point?

    Oil cooler or not ?, Not sure it will clear my t pan but I will make it work if you think I need it

    Valve Covers have oilers, should I plumb them?

    Carbs are boost referenced, The Pro Systems Carbs on my Hydro arent and according to Pro Systems at under normal boost you dont need to, Can you explain?

    I have a shorty Glide In a past post on transmissions you recommended not bracing the back of the trans, Can you explain?

    As always, thank you very much for your help. It is appreiciated, Tom
    You probably won't be able to run more than 6 lbs and maybe 32* Start with 30 and move to 32 and see if picks up anything. But keep an eye on the jetting when you make a move with the timing!

    I didn't think it was possible to run a rear mount and a shorty. I see nothing wrong with a cross member support under the rear of the trans, I don't like bolted mounts. See too many break the case when mounted with a hard mount. Boat flexes and the case doesn't. Cars have pretty soft cushy mounts, boats tend to have solid mounts.

    Oil cooler is going to depend on how long and hard you run the boat. Short blasts or medium cruises you may not need one. But I would invest in a gauge. I'd rather have oil temp than water temp. You pretty much know when the water isn't flowing, and the engine starts to heat up. Not so easy with the oil.

    Let us know how it works out on the dyno

    If you're east of the Continental Divide, and below the Mason Dixon line, the magneto will be fine.

    What jets do you have in the carbs now.



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    Some guy obnoxious001's Avatar
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    Quote Originally Posted by TOMSS1 View Post
    Bob - Getting ready to put the 496 together for my Hallett 19 ss lake rig and need a bit of your sage advise prior to visiting the Dyno and finshing the boat.

    Motor is 4.310 x 4.250
    8.5 - 1
    Iron 345 Merlins with a nice port job
    C Straub roller set to head flow In. 259, Ex 271 @ .050, Lobe lift In. 660 Ex 630, 112 center
    Innercooler w B & M 420
    2 - AED 850s
    Dry Headers
    AV gas
    and your favorite....a Mallory Mag, just like a hillbilly from north of here

    Blower overdrive and Timing starting point?

    Oil cooler or not ?, Not sure it will clear my t pan but I will make it work if you think I need it

    Valve Covers have oilers, should I plumb them?

    Carbs are boost referenced, The Pro Systems Carbs on my Hydro arent and according to Pro Systems at under normal boost you dont need to, Can you explain?

    I have a shorty Glide In a past post on transmissions you recommended not bracing the back of the trans, Can you explain?

    As always, thank you very much for your help. It is appreiciated, Tom
    Quote Originally Posted by gn7 View Post
    You probably won't be able to run more than 6 lbs and maybe 32* Start with 30 and move to 32 and see if picks up anything. But keep an eye on the jetting when you make a move with the timing!

    I didn't think it was possible to run a rear mount and a shorty. I see nothing wrong with a cross member support under the rear of the trans, I don't like bolted mounts. See too many break the case when mounted with a hard mount. Boat flexes and the case doesn't. Cars have pretty soft cushy mounts, boats tend to have solid mounts.

    Oil cooler is going to depend on how long and hard you run the boat. Short blasts or medium cruises you may not need one. But I would invest in a gauge. I'd rather have oil temp than water temp. You pretty much know when the water isn't flowing, and the engine starts to heat up. Not so easy with the oil.

    Let us know how it works out on the dyno

    If you're east of the Continental Divide, and below the Mason Dixon line, the magneto will be fine.

    What jets do you have in the carbs now.
    With AV gas and intercooler,, only 6 psi?

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    Senior Member Hass828's Avatar
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    Quote Originally Posted by obnoxious001 View Post
    With AV gas and intercooler,, only 6 psi?
    That's only west of the continental divide. Anywhere else we can get away with MUCH more.
    "if we keep doing it the same way we always do..we will always get the same results"
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    Bob - To get the boost to 6 what should I run for overdrive on this B & M deal?

    - The rear mount JJ worked out picked up the bolt circle that holds the end plate that replaces the tail housing. I will pass this on and get him to figure out a less rigid deal.

    - I have gauge, The longest would be 15 miles or so at 3500 / 4000 with the occasional blast.

    - Carbs are 85 in the primary w a 3.5 PV, Secondary s are 92, No PV, Texas , Elevation here is 650. What do you think? and what about this boost reference?

    - What about the Valve cover oilers?

    Fixing to be Turkey time, PM your adress and I will shoot you off a bottle of Hootch for helping me, Thanks Again Tom

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    Quote Originally Posted by gn7 View Post

    If you're east of the Continental Divide, and below the Mason Dixon line, the magneto will be fine.
    thanks. I needed that...

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    gn7
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    Quote Originally Posted by obnoxious001 View Post
    With AV gas and intercooler,, only 6 psi?
    Oops. Thanks for pointing that out Barry. Completely over looked it.
    Quote Originally Posted by TOMSS1 View Post
    Bob - To get the boost to 6 what should I run for overdrive on this B & M deal?

    - The rear mount JJ worked out picked up the bolt circle that holds the end plate that replaces the tail housing. I will pass this on and get him to figure out a less rigid deal.

    - I have gauge, The longest would be 15 miles or so at 3500 / 4000 with the occasional blast.

    - Carbs are 85 in the primary w a 3.5 PV, Secondary s are 92, No PV, Texas , Elevation here is 650. What do you think? and what about this boost reference?

    - What about the Valve cover oilers?

    Fixing to be Turkey time, PM your adress and I will shoot you off a bottle of Hootch for helping me, Thanks Again Tom

    If your running AV, I would start the boost at about 8 and maybe check the power difference at 10. That blower is a little tough to nail down a speed for a given boost sue to the rotor design and the fact that is a touch bigger than a 6-71. But 10% over should get you close to 8psi, and 15 % will get you nearer to 10. I would not go past 32 on the timing. If anything, add boost. You will get more bang from the boost than adding timing.
    I wouldn't lose to much sleep over the trans mount. With a shorty glide, the distance from the rear trans mount to the engine plate is pretty short. A turbo 400 with a tail housing is quite a bit longer, and the tail piece is a thin weak POS. I'd go ahead and run the mount JJ made. I don't think its necessary with the glide, but I don't see it hurting anything with a short trans.
    The deal with the boost referenced PVs is that in a light boat in cruise mode, you MIGHT have enough vacuum to keep them closed and save a little on fuel. MIGHT. It depends on YOUR cruise. Id would hook up a vacuum gauge to the manifold and drive the boat normally. If you have less than 3.5" of vac at normal cruise, the referenced PVs are of little use. Its not hard to get 3.5" at cruise in a light boat, specially if your aren't running hi boost pressures. The primary jetting with the PV seems about right. Maybe a touch big on the secondary but I'd leave it there for the dyno. I'd be prepared to jet the carb as low as 88 square with no PV. Steelcomp build a blown 496 some time back with AED 850s. I see if I can find the thread and see what he ended up with.
    As for the oil, if you have a gauge, and it stays around 225 and no higher than 250 with a synthetic, I wouldn't get too concerned over it. Mine runs 250 with a cooler, I never give it second thought,


    Just a heads up. My experience has shown me that fuel and boost make the power in these things. Torque flies out the door when they start to go lean a little, and timing seems to do little after about 32 degrees. If it can take more timing, it can usually take more boost instead, and that will make more power than more timing. I'll take boost over timing any day.

    As for the oilers, they're a great addition for a boat, but not all that important on a lake boat. Millions of boats out there without them. With a dry sump, I am all over spring oilers, but with a wet sump, its just more oil pouring over a spinning crank. The most important thing is don't restrict the lifter gallery.
    If your running the poly V belts on this thing, be prepared for them to slip if you spin the blower past about 10lbs. To get the overdrive ratio you are going to have to measure the pulleys and divide the diameters.

    Thanks for the offer of the hooch, but I never drink hard stuff. It gets me too drunk to fast. About all I can handle is Coors light, and less and less as time goes on. But I do plan to hammer my fair share this Thanksgiving at Parker.



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    Last edited by gn7; 11-14-2013 at 12:59 AM.

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    Quote Originally Posted by gn7 View Post
    Oops. Thanks for pointing that out Barry. Completely over looked it.



    If your running AV, I would start the boost at about 8 and maybe check the power difference at 10. That blower is a little tough to nail down a speed for a given boost sue to the rotor design and the fact that is a touch bigger than a 6-71. But 10% over should get you close to 8psi, and 15 % will get you nearer to 10. I would not go past 32 on the timing. If anything, add boost. You will get more bang from the boost than adding timing.
    I wouldn't lose to much sleep over the trans mount. With a shorty glide, the distance from the rear trans mount to the engine plate is pretty short. A turbo 400 with a tail housing is quite a bit longer, and the tail piece is a thin weak POS. I'd go ahead and run the mount JJ made. I don't think its necessary with the glide, but I don't see it hurting anything with a short trans.
    The deal with the boost referenced PVs is that in a light boat in cruise mode, you MIGHT have enough vacuum to keep them closed and save a little on fuel. MIGHT. It depends on YOUR cruise. Id would hook up a vacuum gauge to the manifold and drive the boat normally. If you have less than 3.5" of vac at normal cruise, the referenced PVs are of little use. Its not hard to get 3.5" at cruise in a light boat, specially if your aren't running hi boost pressures. The primary jetting with the PV seems about right. Maybe a touch big on the secondary but I'd leave it there for the dyno. I'd be prepared to jet the carb as low as 88 square with no PV. Steelcomp build a blown 496 some time back with AED 850s. I see if I can find the thread and see what he ended up with.
    As for the oil, if you have a gauge, and it stays around 225 and no higher than 250 with a synthetic, I wouldn't get too concerned over it. Mine runs 250 with a cooler, I never give it second thought,


    Just a heads up. My experience has shown me that fuel and boost make the power in these things. Torque flies out the door when they start to go lean a little, and timing seems to do little after about 32 degrees. If it can take more timing, it can usually take more boost instead, and that will make more power than more timing. I'll take boost over timing any day.

    As for the oilers, they're a great addition for a boat, but not all that important on a lake boat. Millions of boats out there without them. With a dry sump, I am all over spring oilers, but with a wet sump, its just more oil pouring over a spinning crank. The most important thing is don't restrict the lifter gallery.
    If your running the poly V belts on this thing, be prepared for them to slip if you spin the blower past about 10lbs. To get the overdrive ratio you are going to have to measure the pulleys and divide the diameters.

    Thanks for the offer of the hooch, but I never drink hard stuff. It gets me too drunk to fast. About all I can handle is Coors light, and less and less as time goes on. But I do plan to hammer my fair share this Thanksgiving at Parker.
    Great post Bob.
    "if we keep doing it the same way we always do..we will always get the same results"
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    I'll be very interested to see how much boost you can generate with that blower and those heads.
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    Quote Originally Posted by gn7 View Post
    Oops. Thanks for pointing that out Barry. Completely over looked it.



    If your running AV, I would start the boost at about 8 and maybe check the power difference at 10. That blower is a little tough to nail down a speed for a given boost sue to the rotor design and the fact that is a touch bigger than a 6-71. But 10% over should get you close to 8psi, and 15 % will get you nearer to 10. I would not go past 32 on the timing. If anything, add boost. You will get more bang from the boost than adding timing.
    I wouldn't lose to much sleep over the trans mount. With a shorty glide, the distance from the rear trans mount to the engine plate is pretty short. A turbo 400 with a tail housing is quite a bit longer, and the tail piece is a thin weak POS. I'd go ahead and run the mount JJ made. I don't think its necessary with the glide, but I don't see it hurting anything with a short trans.
    The deal with the boost referenced PVs is that in a light boat in cruise mode, you MIGHT have enough vacuum to keep them closed and save a little on fuel. MIGHT. It depends on YOUR cruise. Id would hook up a vacuum gauge to the manifold and drive the boat normally. If you have less than 3.5" of vac at normal cruise, the referenced PVs are of little use. Its not hard to get 3.5" at cruise in a light boat, specially if your aren't running hi boost pressures. The primary jetting with the PV seems about right. Maybe a touch big on the secondary but I'd leave it there for the dyno. I'd be prepared to jet the carb as low as 88 square with no PV. Steelcomp build a blown 496 some time back with AED 850s. I see if I can find the thread and see what he ended up with.
    As for the oil, if you have a gauge, and it stays around 225 and no higher than 250 with a synthetic, I wouldn't get too concerned over it. Mine runs 250 with a cooler, I never give it second thought,


    Just a heads up. My experience has shown me that fuel and boost make the power in these things. Torque flies out the door when they start to go lean a little, and timing seems to do little after about 32 degrees. If it can take more timing, it can usually take more boost instead, and that will make more power than more timing. I'll take boost over timing any day.

    As for the oilers, they're a great addition for a boat, but not all that important on a lake boat. Millions of boats out there without them. With a dry sump, I am all over spring oilers, but with a wet sump, its just more oil pouring over a spinning crank. The most important thing is don't restrict the lifter gallery.
    If your running the poly V belts on this thing, be prepared for them to slip if you spin the blower past about 10lbs. To get the overdrive ratio you are going to have to measure the pulleys and divide the diameters.

    Thanks for the offer of the hooch, but I never drink hard stuff. It gets me too drunk to fast. About all I can handle is Coors light, and less and less as time goes on. But I do plan to hammer my fair share this Thanksgiving at Parker.

    Bob - The Blower has 8mm pulleys so I dont have the v belt problems to worry about. I think Scott has a good point that I wondered about, Whether the blower would make boost over 6 or 7 lbs, Too big a head, Too small a blower. I had the same problem on my 509, same head, Non teflon big rotor 6-71, Wouldnt make any more boost after 18 over, We got 7 lbs out of it. I need to break down a buy a pair of Merts 10-71s, kind of hoping to find some used, Anyway we shall see, I am picking the parts up today so before Christmas we will see what the pump has to say about this bunch of junk.

    Beer is too heavy to ship so I guess me and JJ need to come watch you boys do your magic with that red boat. Maybe try to fit a few beers in the trunk of the rent car for you. What is the best race to attend ?

    Again thanks for taking time to help me. I have learned a lot from you. The info on Boost vs timing is totaly enlightening, Let me know on the race , Tom

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    Quote Originally Posted by TOMSS1 View Post
    Bob - The Blower has 8mm pulleys so I dont have the v belt problems to worry about. I think Scott has a good point that I wondered about, Whether the blower would make boost over 6 or 7 lbs, Too big a head, Too small a blower. I had the same problem on my 509, same head, Non teflon big rotor 6-71, Wouldnt make any more boost after 18 over, We got 7 lbs out of it. I need to break down a buy a pair of Merts 10-71s, kind of hoping to find some used, Anyway we shall see, I am picking the parts up today so before Christmas we will see what the pump has to say about this bunch of junk.

    Beer is too heavy to ship so I guess me and JJ need to come watch you boys do your magic with that red boat. Maybe try to fit a few beers in the trunk of the rent car for you. What is the best race to attend ?

    Again thanks for taking time to help me. I have learned a lot from you. The info on Boost vs timing is totaly enlightening, Let me know on the race , Tom
    Not sure why the heads would limit the boost. I agree with Steel, the heads will effect the boost compared to restrictive heads. But ultimately the boost attained with the heads that flow well enough is the size of the engine. A 385cc head doesn't require any more blower to hit 8 psi on a 496, than a set of 345 or even good flowing 320s. If the head and cam are there, the cylinder size determines the boost, unless your throwing out the exhaust, and I doubt that's going to be a problem. The cam and cylinder size play a larger part of boost numbers than the heads, unless the heads are too small, like stock SBF heads, and the air stacks up in the manifold.
    If you ran out of air with a 6-71 at 18 over, it was probably a small bore 6-71. The B&M is a little more efficient at moving air than a unstrapped GMC. Its the same basic rotor design as the 144 and 177, and they spin the shit out of those things. Not saying its not limited, but I think you can hit 10psi with it.
    In the end, its CFM delivered past the intake valve and air stacked up in the cylinder that determines the power, not the air stacked up in the manifold.



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    Last edited by gn7; 11-14-2013 at 11:46 AM.

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    When the port isn't the restriction the intake valve becomes the next bottleneck in the pipeline. I believe these heads have a 2.30 intake valve which is pretty big, even for a blown 496. NA 496 in the 6000rpm range needs a 2.19 valve with ~85% throat. Even with 15# boost you're only looking at an increase of 2% over that for optimal. Airspeed through that 2.30 valve with it's 85-88% throat will be very slow. That'll make it hard to build boost (which doesn't mean it won't make power) aside form the size of the engine...which I agree on what you said. Displacement and blower size are directly related when it comes to boost.
    Also, OP:
    I'd make sure you have valve-to-bore clearance for that intake valve.
    Last edited by scott foxwell; 11-15-2013 at 06:18 AM.
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    Quote Originally Posted by steelcomp View Post
    When the port isn't the restriction the intake valve becomes the next bottleneck in the pipeline. I believe these heads have a 2.30 intake valve which is pretty big, even for a blown 496. NA 496 in the 6000rpm range needs a 2.19 valve with ~85% throat. Even with 15# boost you're only looking at an increase of 2% over that for optimal. Airspeed through that 2.30 valve with it's 85-88% throat will be very slow. That'll make it hard to build boost (which doesn't mean it won't make power) aside form the size of the engine...which I agree on what you said. Displacement and blower size are directly related when it comes to boost.
    Also, OP:
    I'd make sure you have valve-to-bore clearance for that intake valve.
    Scott - Heads have 2.250 valve, Thanks for reminding me about valve to bore

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    Quote Originally Posted by TOMSS1 View Post
    Scott - Heads have 2.250 valve, Thanks for reminding me about valve to bore
    OK, cool. That helps. Still big, but definitely better.
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