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Discussion Starter #1
Ok looks like i am going to go the blown route. Now the questions really start for me.
Here is what i am thinking of doing, just do not know the path to take.

496 BBC with a 8-71

I have a gen 4 HP block to start with, I also have a set of Dart Pro 325 heads to go with it. What do i do from here.

Need info to give the Machine shop. This build will take some time for money reasons but i want to lay out my path and start gathering parts for my goal.

This is going in a shovel nose ski hydro. Not looking to be the fastest boat on the river but a cool hot rod.
 

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Ok looks like i am going to go the blown route. Now the questions really start for me.
Here is what i am thinking of doing, just do not know the path to take.

496 BBC with a 8-71

I have a gen 4 HP block to start with, I also have a set of Dart Pro 325 heads to go with it. What do i do from here.

Need info to give the Machine shop. This build will take some time for money reasons but i want to lay out my path and start gathering parts for my goal.

This is going in a shovel nose ski hydro. Not looking to be the fastest boat on the river but a cool hot rod.
spend more money :D
 

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Ok looks like i am going to go the blown route. Now the questions really start for me.
Here is what i am thinking of doing, just do not know the path to take.

496 BBC with a 8-71

I have a gen 4 HP block to start with, I also have a set of Dart Pro 325 heads to go with it. What do i do from here.

Need info to give the Machine shop. This build will take some time for money reasons but i want to lay out my path and start gathering parts for my goal.

This is going in a shovel nose ski hydro. Not looking to be the fastest boat on the river but a cool hot rod.

what fuel do you plan on running ?.....how much power you looking at ?
 

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Discussion Starter #6
what fuel do you plan on running ?.....how much power you looking at ?
I am on the fence will the fuel deal. Really thinking hard about using alky but not 100% on that. I am not super keen on the idea of taking fuel with me. I like being able to pull up and fill up with 93

I am looking to get somewhere in the 800-900 range
 

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l if ur really thinking alcohol and HP you better really need to get a better block, stock gen 4 4 bolt will have problems, maincaps walking, cracking in lifter valley,cracks in rear,ect ect etc...oh and with out adding the extra headbolts sealing becomes a issue as well.

I guess the question would be what kind of HP are you lookin at?? 800?, 1000? or 2000?
 

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Discussion Starter #9
l if ur really thinking alcohol and HP you better really need to get a better block, stock gen 4 4 bolt will have problems, maincaps walking, cracking in lifter valley,cracks in rear,ect ect etc...oh and with out adding the extra headbolts sealing becomes a issue as well.

I guess the question would be what kind of HP are you lookin at?? 800?, 1000? or 2000?
800-900. This will not be a race boat just want a peppy lake boak
That looks good and runs a little too.
 

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I am on the fence will the fuel deal. Really thinking hard about using alky but not 100% on that. I am not super keen on the idea of taking fuel with me. I like being able to pull up and fill up with 93

I am looking to get somewhere in the 800-900 range
I dont see any compression over 8.5 if you have a decent blower and less than 32 in the Mag, I dont like cheap fuel deals, alky is the best, you may not get much mileage but you are WAY less likely to hurt a bunch of expensive parts, the choice is yours, go with Alky, and Up the compression if not, you have to kill the compression or the engine will murder itsealf, and on 93, it'll never come close to what it runs with alky
 

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Discussion Starter #13
I dont see any compression over 8.5 if you have a decent blower and less than 32 in the Mag, I dont like cheap fuel deals, alky is the best, you may not get much mileage but you are WAY less likely to hurt a bunch of expensive parts, the choice is yours, go with Alky, and Up the compression if not, you have to kill the compression or the engine will murder itsealf, and on 93, it'll never come close to what it runs with alky
Seems like this is the way to go. Do i need to do anything extra to the block? What compression should i run on Alky with an 8-71?
 

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Seems like this is the way to go. Do i need to do anything extra to the block? What compression should i run on Alky with an 8-71?


10:1 is safe, you can run some decent boost, like 20-30% over and not worry at all, just depends


I would look into putting some filler in the block if it's a big bore deal to thin a cylinder wall isnt good you might have it sonic tested to see if the walls are good, no core shift....
 

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If I was going to build another blower motor this is how I would do it. Simple, Easy, Cheap Horsepower. http://www.draglist.com/stories/SOD%20Apr%202001/SOD-042701.htm


the Truck Block has an additional advantage in that you can use a longer Rod, raising the torq curv a little, and I agree with most of the above site, except for the Main and Rod Clearances, there is absolutely NO reason to run more than .0032, nor less than .0027, anything in that range will be fine on 50W , if you run Higher clearances, you overwork the Oil rings and oil pump, and you want this engine Internally Balanced if at all possible

no less than .090 on exhaust valve to piston clearance, .085 on intake and dont use a dial indicator to find TDC, use a positive stop and divide by 2 , that is correct TDC. many rear mains on BBC are small, make sure yours isnt...
 

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the Truck Block has an additional advantage in that you can use a longer Rod, raising the torq curv a little, and I agree with most of the above site, except for the Main and Rod Clearances, there is absolutely NO reason to run more than .0032, nor less than .0027, anything in that range will be fine on 50W , if you run Higher clearances, you overwork the Oil rings and oil pump, and you want this engine Internally Balanced if at all possible

no less than .090 on exhaust valve to piston clearance, .085 on intake and dont use a dial indicator to find TDC, use a positive stop and divide by 2 , that is correct TDC. many rear mains on BBC are small, make sure yours isnt...
Amen, I hate it when I hear someone give advice to use the ole dial indicator for that. Positive piston stop is the only way to go Baby.
 

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Discussion Starter #18 (Edited)
Ok here is the deal, got a deal on a new BDS 8-71 kit (did some horse trading)
I am going to order the pullleys so hear is where i am at

I know there are many factors to this but lets say i want to make 10lbs of boost on pump gas (93 or avgas) BBC 496 say 8.5:1 compression Should i have this thing around 5% overdriven? If so is this a safe setup for the fuel mentioned?
If i am reading the chart correctly should use 47 bottom and 44 top??
 

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Ok here is the deal, got a deal on a new BDS 8-71 kit (did some horse trading)
I am going to order the pullleys so hear is where i am at

I know there are many factors to this but lets say i want to make 10lbs of boost on pump gas (93 or avgas) BBC 496 say 8.5:1 compression Should i have this thing around 5% overdriven? If so is this a safe setup for the fuel mentioned?
If i am reading the chart correctly should use 47 bottom and 44 top??
Every engine will be different. Your going to have to toy with it to get the boost dialed were your wanting it.
I would buy the pulleys and start out with them swapped at 5% under instead of over and see were your at before changing them.
10psi is going to be pushing it on the pump gas, watch your plugs and start out with the timing low, like 26-28 total and creep up 1 degree at a time while watching the earth strap on the plugs. I'd stop at 31-32 if everythings looking good on the plugs. And what ever you do dont be tempted to throw some cheap 89 octain in it to get ya home, or you'll be sorry.

Edit- you'll also want to lock your advance out in your dizzy. It wont want to start with that low of comp. and much mech. advance in it with a total of 28. If you lock it out it'll start just fine.
 

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Ok here is the deal, got a deal on a new BDS 8-71 kit (did some horse trading)
I am going to order the pullleys so hear is where i am at

I know there are many factors to this but lets say i want to make 10lbs of boost on pump gas (93 or avgas) BBC 496 say 8.5:1 compression Should i have this thing around 5% overdriven? If so is this a safe setup for the fuel mentioned?
If i am reading the chart correctly should use 47 bottom and 44 top??

dont know if I am reading this correct, but you have a lot of other parts you need ,before pulleys.. If you dont have unlimited $$$, I would build your 496 @ 8.5:1 with your 8-71 with around 5%-8% overdriven on pump gas ONLY if you run a water/ alky injection set up, or a more expensive intercooler. I think 10lbs on pump gas alone is too much boost. Of course, heads, and cams have a big affect on boost.
 
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