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Discussion Starter #1
So i blew up my blower 496 as seen below new boat damage.jpg
it has all good parts in it, except it is still just a gen IV chevy with the same Iron heads, not even ported. I have the motor apart and might just port the old heads since they arent in bad condition at all. Or should i opt for a set of aluminum heads with a new cam to better suit the increased flow ill probably get. Also is anyone interesd in a pair of iron heads for a 496? Im saving the block, boring out to .070 new pistons bearings seals, will have on dyno soon. Just need to decide on heads.

Any input i'd appreciate.
 

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The type of HEADS you decide to run is the least of your problem. Better solve the cause of that meltdown, starting with your entire fuel system! (from tank pickup, fuel line/regulator sizes,float level,jetting). Your heads didn't cause this, nor will a "upgrade" to aluminum solve it. Just my .02 Good luck! Jocko
 

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Discussion Starter #3
The type of HEADS you decide to run is the least of your problem. Better solve the cause of that meltdown, starting with your entire fuel system! (from tank pickup, fuel line/regulator sizes,float level,jetting). Your heads didn't cause this, nor will a "upgrade" to aluminum solve it. Just my .02 Good luck! Jocko
The heads aren't to fix the problem. The system leaned out running about 9 ilbs of boost, due to the fuel lines being 3/8" up to the carbs and 1/2" into the regulator. Ill get new lines, deliver more fuel. The rest seems to be set up pretty well, has a good pump and everything should work great. Figured if i can get some more air to flow, ill ahve a little more power, but it will also lower the pressur ein the manifold to about 8 lbs. Ill be running 91 octane also.

I was just wondering if the added money in the rebuild is a good idea, or i wouldnt see the difference in performance?
 

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AKA Blownjet 468
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The heads aren't to fix the problem. The system leaned out running about 9 ilbs of boost, due to the fuel lines being 3/8" up to the carbs and 1/2" into the regulator. Ill get new lines, deliver more fuel. The rest seems to be set up pretty well, has a good pump and everything should work great. Figured if i can get some more air to flow, ill ahve a little more power, but it will also lower the pressur ein the manifold to about 8 lbs. Ill be running 91 octane also.

I was just wondering if the added money in the rebuild is a good idea, or i wouldnt see the difference in performance?
your problem has nothing to do with 3/8 fuel lines from the regulator etc.. look at my sig pic!
that's what I ran on my 12-71 blower motor @ 16 lbs boost for years, not a problem.
I'd be looking further if I was you;)
 

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Discussion Starter #5
your problem has nothing to do with 3/8 fuel lines from the regulator etc.. look at my sig pic!
that's what I ran on my 12-71 blower motor @ 16 lbs boost for years, not a problem.
I'd be looking further if I was you;)
It could be many things. I'm having a motor builder do the build, so he should be able to fix whatever it was. And since I'm putting it on the dyno, maybe a post dyno inspection might be a good idea.

So stay with iron heads ported? or get some new Aluminum heads? since its oging ot be a new motor
 

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Some guy
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The heads aren't to fix the problem. The system leaned out running about 9 ilbs of boost, due to the fuel lines being 3/8" up to the carbs and 1/2" into the regulator. Ill get new lines, deliver more fuel. The rest seems to be set up pretty well, has a good pump and everything should work great. Figured if i can get some more air to flow, ill ahve a little more power, but it will also lower the pressur ein the manifold to about 8 lbs. Ill be running 91 octane also.

I was just wondering if the added money in the rebuild is a good idea, or i wouldnt see the difference in performance?
I agree the the size of the fuel lines was not the problem. Better check the entire fuel system,, and also how much timing were you running?

As to the aluminum heads,, how big is your wallet? If you had aluminum and iron heads with identical flow, you won't gain performance with the aluminum,, just save weight and have something that is easier to repair (weld). The aluminum may be very slightly more forgiving to detonation.
 

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steelcomp was here
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Most aluminum heads these days are going to benefit you with more modern combustion chamber and port designs, and while flow numbers might be identical as your iron heads...even after you port them...chances are you'll make more power with aluminum heads. If it's a light weight boat, the weight savings can be significant.
 

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So i blew up my blower 496 as seen below View attachment 117079
it has all good parts in it, except it is still just a gen IV chevy with the same Iron heads, not even ported. I have the motor apart and might just port the old heads since they arent in bad condition at all. Or should i opt for a set of aluminum heads with a new cam to better suit the increased flow ill probably get. Also is anyone interesd in a pair of iron heads for a 496? Im saving the block, boring out to .070 new pistons bearings seals, will have on dyno soon. Just need to decide on heads.

Any input i'd appreciate.
i have done this a few times,once this bad in 2 cylinders at once. check your fuel pressure. if it is good at wot you are most likely lean ,realy lean. not sure about what the detonation looks like , mine detonated & hammered the bearings out. but no piston damage. anyway i did it all to get enough fuel. tank pick-up enlarged, vent enlarged, bigger regulator, new fuel switch, bigger wire to the electric switch, jetted super big,#10 to (2)#8an hoses to the carb. the whole main problem was the needle & seat was too small in the carb. a pyrometer is a good cheap way to see if you are running lean if the temp keeps creeping up you definetly need to fatten it up .after i put the needle & seats in, it would hold the exaust temp & i coulkd see the temp difference when jetting was changed. i am running @1425* now but thats too fat for my set-up i need to get it to @ 1475* to match the afr needed. thats kind of hot for most. not sure if it is the gauge location ,cam causing burning fuel into pipes gauge itself. all i know is @ 1550* sh*t melts if i dont let up @ 1/4 mile, 1600* too late! valves tulliped, possible piston damage.hope this helps
 

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Discussion Starter #9
Most aluminum heads these days are going to benefit you with more modern combustion chamber and port designs, and while flow numbers might be identical as your iron heads...even after you port them...chances are you'll make more power with aluminum heads. If it's a light weight boat, the weight savings can be significant.
Wallets tight, but motor is out, and I might as well get it done. And it is in a 25ft daytona, running 90 mph 30 minutes at a time. weight not an issue. They will provide better heat transfer though.
 

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Discussion Starter #10
i have done this a few times,once this bad in 2 cylinders at once. check your fuel pressure. if it is good at wot you are most likely lean ,realy lean. not sure about what the detonation looks like , mine detonated & hammered the bearings out. but no piston damage. anyway i did it all to get enough fuel. tank pick-up enlarged, vent enlarged, bigger regulator, new fuel switch, bigger wire to the electric switch, jetted super big,#10 to (2)#8an hoses to the carb. the whole main problem was the needle & seat was too small in the carb. a pyrometer is a good cheap way to see if you are running lean if the temp keeps creeping up you definetly need to fatten it up .after i put the needle & seats in, it would hold the exaust temp & i coulkd see the temp difference when jetting was changed. i am running @1425* now but thats too fat for my set-up i need to get it to @ 1475* to match the afr needed. thats kind of hot for most. not sure if it is the gauge location ,cam causing burning fuel into pipes gauge itself. all i know is @ 1550* sh*t melts if i dont let up @ 1/4 mile, 1600* too late! valves tulliped, possible piston damage.hope this helps
Thanks for the input, I'll have them pyro while its on the dyno under full load at WOT. The rest of the pistons seem about ready to go also, getting discolored. and also the bearings are done. I have a builder working on it, and he was looking into the fuel system, its got all good stuff, just an adjustment needed., a few degrees in timing thinking the iron heads can take it will cause this. I don't know how much they can port the old iron heads, im not concerned baout weight given its a 25' daytona loaded with people at 90mph. but a little larger chamber coupled with a little larger cam may help some.

Builder was saying almost 100hp more with some nice heads over the stock iron ones. from about 750 to 850HP. The Dyno will tell :)
 

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Purple headed member
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Thanks for the input, I'll have them pyro while its on the dyno under full load at WOT. The rest of the pistons seem about ready to go also, getting discolored. and also the bearings are done. I have a builder working on it, and he was looking into the fuel system, its got all good stuff, just an adjustment needed., a few degrees in timing thinking the iron heads can take it will cause this. I don't know how much they can port the old iron heads, im not concerned baout weight given its a 25' daytona loaded with people at 90mph. but a little larger chamber coupled with a little larger cam may help some.

Builder was saying almost 100hp more with some nice heads over the stock iron ones. from about 750 to 850HP. The Dyno will tell :)
What heads are you currently running?
 
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