SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: jamiemwedmore1234 on June 05, 2016, 09:01:07 PM
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Got a few questions for the motor heads I'm looking at upgrading my heads on my 496 I think it's about the only thing stock on my set up guesstimating my HP I would say somewhere around 550 based on RPM and MPH currently I have rectangular port iron heads nothing to fancy bigger valves if anything and a decent cam set up .im looking at either AFR or DART aluminum heads I would like to continue to run 91 Octane My basic set up is 496ci. Solid flatt tappet cam. Hp 950 Holley carb I will probably Change the cam when I swap out the heads and go full roller but this is about the heads what do you guys prefer
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James Bostick to the SCJB Phone
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Honest opinion, out of the box the AFR heads will outperform the Darts, with a quality port job and working the combustion chambers will be the best money can buy.
These are just my opinions based on information I gathered more than 10 years ago.
GT
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Got a few questions for the motor heads I'm looking at upgrading my heads on my 496 I think it's about the only thing stock on my set up guesstimating my HP I would say somewhere around 550 based on RPM and MPH currently I have rectangular port iron heads nothing to fancy bigger valves if anything and a decent cam set up .im looking at either AFR or DART aluminum heads I would like to continue to run 91 Octane My basic set up is 496ci. Solid flatt tappet cam. Hp 950 Holley carb I will probably Change the cam when I swap out the heads and go full roller but this is about the heads what do you guys prefer
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Thank thing runs really well bud.
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AFR is my first choice. But I have Brodix bb2's on the race motor and they work really well.
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Thank thing runs really well bud.
thank you it does run good and for the most part pretty reliable just looked to go a little faster naturally aspirated
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Has anybody had a problem with corrosion with the aluminum heads is there anything you can do about it if so
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Has anybody had a problem with corrosion with the aluminum heads is there anything you can do about it if so
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Stay out of firebird lol.
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Has anybody had a problem with corrosion with the aluminum heads is there anything you can do about it if so
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About the same as a aluminum intake.
Salt is the killer.
Flush flush flush. ..
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My boat has only been in Elsinore or the river so sounds like shouldn't be a problem
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They sure don't give those heads away around 3000 for the darts and 2800 for the AFR good thing the motor goes from boat to boat
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They sure don't give those heads away around 3000 for the darts and 2800 for the AFR good thing the motor goes from boat to boat
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$3k?
You should be buying them bare and should only be about $900 a head.
What are you looking at?
GT
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Complete assembled set of heads off summit racing but I also need to get with my engine builder on what cc heads to get.
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Complete assembled set of heads off summit racing but I also need to get with my engine builder on what cc heads to get.
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Just my pinion, I would buy them bare. Have your machinist build them with the best valves, retainers, springs and rotators.
Remember to use larger than stock guide to valve clearance.
JMHO
GT
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Just my pinion, I would buy them bare. Have your machinist build them with the best valves, retainers, springs and rotators.
Remember to use larger than stock guide to valve clearance.
JMHO
GT
ill give my motor guy a call on that specially since he knows my motor inside and out and I want to put a more aggressive came in it he can deal with the clearances
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If you have the option, go for a "cast smaller" combustion chamber. Otherwise you will need to deck the heads to bring the compression ratio back up.
First, you are switching to aluminum heads. Aluminum is a greater conductor of heat which will pull heat out of the combustion chamber. To maintain equal performance between identical heads, with the only difference being iron vs. aluminum, the general rule of thumb is increase the aluminum head compression by one ratio point. The act of compressing air generates heat. The additional point of compression puts that lost heat back into the combustion chamber.
Second, going to a more aggressive roller cam will most likely result in increased timing events. That means that your dynamic compression ratio will be down compared to what it is now.
Working with your engine builder and starting out with bare castings will help you arrive at what is best for your combination. It would also allow you to hard anodized the heads if you are overly concerned about corrosion.
Good luck,
Joe
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Either one of those heads are good. Your not going to make a mistake with either. I believe Bostick prefers pro 1 heads but likes both. Hopefully he will chime in.
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To be honest, pump gas deal 496... Gm iron rectangle heads with a little fluff and buff... and right cam combo... 650-670 is not too hard to get... In a jet usable range (6200-6400). I mean spend money if you want some aluminum heads, but bang for buck... You got a good deal of potential left with what you got already.
I mean my po-dunker single carb 461 with iron 990 heads made 658 @ 6300 on Valero 91... But everything is just right and the cam/head combo works very well. So don't think of them as door stops just yet.
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To be honest, pump gas deal 496... Gm iron rectangle heads with a little fluff and buff... and right cam combo... 650-670 is not too hard to get... In a jet usable range (6200-6400). I mean spend money if you want some aluminum heads, but bang for buck... You got a good deal of potential left with what you got already.
I mean my po-dunker single carb 461 with iron 990 heads made 658 @ 6300 on Valero 91... But everything is just right and the cam/head combo works very well. So don't think of them as door stops just yet.
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by all means my iron heads do get the job done but loosing 60-70 pounds and going full roller should wake it up that much more and talking to my motor guy going with 650-700 lift cam opens up a few more possibilities that those iron heads won't allow the heads and cam combo that I will be taking off will be put on the shelf ready for another motor project
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by all means my iron heads do get the job done but loosing 60-70 pounds and going full roller should wake it up that much more and talking to my motor guy going with 650-700 lift cam opens up a few more possibilities that those iron heads won't allow the heads and cam combo that I will be taking off will be put on the shelf ready for another motor project
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Iron rectangles not allow performane @.650-.700 lift range? On a pump gas deal? News to me.
Well... Then nevermind... You got it figured out.
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Iron rectangles not allow performane @.650-.700 lift range? On a pump gas deal? News to me.
Well... Then nevermind... You got it figured out.
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didn't say iron heads don't get the job done I want the most I can get out of my motor rectangular port 990 we'll never flow as good as a set of AFR OR DARTS heads and if I'm going to go dump a grand into stock heads why not spend a little more s go bigger and better so whether I got it figured out or not 👍🏻you like the 990s that much I'll sell you mine give you a hell of a deal that way you dump more money into them and it not hurt so bad 🤔
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didn't say iron heads don't get the job done I want the most I can get out of my motor rectangular port 990 we'll never flow as good as a set of AFR OR DARTS heads and if I'm going to go dump a grand into stock heads why not spend a little more s go bigger and better so whether I got it figured out or not 👍🏻you like the 990s that much I'll sell you mine give you a hell of a deal that way you dump more money into them and it not hurt so bad 🤔
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Nah... I'm good... You asked an opinion... I offered one that involved spending a considerable amount less money, using much of what you already have, and making a decent power gain... My opinion was wrong... No big deal.
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What are you looking to get for them?
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I've seen some real bad ass engines running iron rectangle ports. If I hadn't been lucky in getting a good deal buying aluminum heads id gladly run 990's over procrap or something of the like that was in my price range. I'd vote for giving them some love and finding the proper solid roller for the combo, Bostick knows his stuff!
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didn't say iron heads don't get the job done I want the most I can get out of my motor rectangular port 990 we'll never flow as good as a set of AFR OR DARTS heads and if I'm going to go dump a grand into stock heads why not spend a little more s go bigger and better so whether I got it figured out or not 👍🏻you like the 990s that much I'll sell you mine give you a hell of a deal that way you dump more money into them and it not hurt so bad 🤔
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I Would listen to the Bostick .... He's a knowledgeable man when it comes to making power ... JMO
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Chit I got a set of 781's with big valves in them that would hold up against just about any of the knock off aluminum heads... And I know I wouldn't have a ticking time bomb on my hands...
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Nah... I'm good... You asked an opinion... I offered one that involved spending a considerable amount less money, using much of what you already have, and making a decent power gain... My opinion was wrong... No big deal.
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i value your opinion I see what you have built I've got my ass handed to me my a couple of your boats the discussion was a preference on AFR vrs DART I'm all ears what do you have to offer on reworking the heads I have and rough cost or shoot me a phone # so I can better describe my set up to see if working my heads over is even worth it or going to the after market word
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Jamie, I wouldn’t dismiss what James Bostick has told you, I’m going to side with him also on this topic. The GM rectangle port iron heads are great, there is a lot of potential in those heads, but you have to ask yourself, how much more power and speed are you really after?. Remember one important thing, bigger WILL NOT guarantee you more power, bigger port volume can hurt overall performance due to loss of velocity filling the cylinders, the only way to get the velocity back along with volume is to turn higher RPM, (piston speed), your pump is now in question, what’s your max RPM now? We all know how important cam selection is, Flusher spoke of loosing dynamic compression, this is another concern with big lift and long duration cams in an engine that won’t see the necessary RPM to justify these components. Usually in larger displacement engines we can have cams custom ground with a wider lobe separation to get the dynamic compression back, not requiring as high of RPM to fill the cylinders adequately. Sounds like you have money burning a hole in your pocket, just be wise in your choices, also going with a big solid roller cam may require more maintenance and upkeep, also quicker valve spring fatigue. Taking some of these expensive steps may not give you the results your looking for, and also put you in a category of giving up some reliability and fun. If your 496 is healthy it should be putting out close to 600hp, I just built a 489ci BBC with 781 oval port heads with the larger valves and mild port & bowl work and it dynoed just shy of 600hp, hell my 10.0:1 467ci with shit box slightly worked peanut port heads made 541hp on the dyno. It’s all about the complete combination within the useable rpm range along with everything working in harmony to produce good power.
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Jamie, I wouldn’t dismiss what James Bostick has told you, I’m going to side with him also on this topic. The GM rectangle port iron heads are great, there is a lot of potential in those heads, but you have to ask yourself, how much more power and speed are you really after?. Remember one important thing, bigger WILL NOT guarantee you more power, bigger port volume can hurt overall performance due to loss of velocity filling the cylinders, the only way to get the velocity back along with volume is to turn higher RPM, (piston speed), your pump is now in question, what’s your max RPM now? We all know how important cam selection is, Flusher spoke of loosing dynamic compression, this is another concern with big lift and long duration cams in an engine that won’t see the necessary RPM to justify these components. Usually in larger displacement engines we can have cams custom ground with a wider lobe separation to get the dynamic compression back, not requiring as high of RPM to fill the cylinders adequately. Sounds like you have money burning a hole in your pocket, just be wise in your choices, also going with a big solid roller cam may require more maintenance and upkeep, also quicker valve spring fatigue. Taking some of these expensive steps may not give you the results your looking for, and also put you in a category of giving up some reliability and fun. If your 496 is healthy it should be putting out close to 600hp, I just built a 489ci BBC with 781 oval port heads with the larger valves and mild port & bowl work and it dynoed just shy of 600hp, hell my 10.0:1 467ci with shit box slightly worked peanut port heads made 541hp on the dyno. It’s all about the complete combination within the useable rpm range along with everything working in harmony to produce good power.
here are my thoughts a set of dart aluminum 121cc heads 320cc intake runner a Howard roller 663 lift and keeping the compression pump gas friendly my motor guy claims I'll gain in the ball park of 100 hp and butt load of torque I haven't pulled the trigger on this price tag we'll be around 3500-4000 $ which is a lot I am open to reworking my rec port heads. But am looking to get the most I can with out spraying I'm not no motor guy but should still be somewhat reliable yah/no there's nothing else to do to my motor or pump and I don't want to spray
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here are my thoughts a set of dart aluminum 121cc heads 320cc intake runner a Howard roller 663 lift and keeping the compression pump gas friendly my motor guy claims I'll gain in the ball park of 100 hp and butt load of torque I haven't pulled the trigger on this price tag we'll be around 3500-4000 $ which is a lot I am open to reworking my rec port heads. But am looking to get the most I can with out spraying I'm not no motor guy but should still be somewhat reliable yah/no there's nothing else to do to my motor or pump and I don't want to spray
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with all that being said I'm just chasing that mph whether the iron rec port heads do the job or the more $$ dart heads do it my goal is hit 90s I figured Buying a better head would be the more reliable rout but I am by no means a motor builder so I'm all ears
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Had a seat of 990 heads ported. The head Porter called them a economy port job. These 990 heads blew 368 int. 277.9 ex. That is pretty respectable to make power. As they say! Speed cost! How fast do you want to go?
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with all that being said I'm just chasing that mph whether the iron rec port heads do the job or the more $$ dart heads do it my goal is hit 90s I figured Buying a better head would be the more reliable rout but I am by no means a motor builder so I'm all ears
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Get to 90s is gonna take some hp. I have the same hull but a bit older, I'm at 700-750hp never Been on a Dino. And I'm running around 85mph. Bbf521 a pretty built pump. No show no ride plate. Running a droop and a nozzle insert. 85mph has been my best I've seen in the lake river may be a few more if we're counting down river I can prolly get right under 90.
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Well I pulled the trigger ordered new pro 1 darts now order up a head stud kit and a roller cam and let the game begin
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Christmas in July
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