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Do I need to Balance HP454 !

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Ditchdigger, Feb 4, 2003.

  1. Ditchdigger

    Ditchdigger Registered Member

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    Help!
    I rebuilding my 454 for my 84 Blazer and I'm going with
    Hypereutectic pistons and jumping to 9:0.1 Compression!
    I'm using the stock Rods and using a factory steel crank
    Do I need to Balance??????????????????????????????????

    P.S it will not be a racer, just street performance, and what would be the going cost for balancing?

    Thanks!
     
  2. 4DiggerDan

    4DiggerDan 1/2 ton status

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    Balance it!!! Figure out what the weight of a stock 454 piston is and compare it to the weight of that hyeruetectic. Then you'll see why. That and balanced engines live longer and run smoother. Going rate where I live is 180 bucks on a V8. So thats what we charge /forums/images/graemlins/laugh.gif

    You say your going hypereutectic?? Keith Black?? Make sure you ask your engine machinist if he has to do anything different on KBs. If he says, "Naw, you just stick the rings on the damn pistons and stuff 'em in the hole..." Run... Run far far away... And hide... With a weapon... He should say "Yes, since KB locates their top ring farther up on the piston than most manufacturers, you DO need to run more ring gap. The nice thing about KB's having the top ring up farther is that it makes a few more ponies and keeps emissions down, HOWEVER being farther up it runs HOTTER, when rings run HOTTER, they EXPAND more. When rings EXPAND more, they need more GAP. I usually stay to the loose end of their formula in their catalog and I haven't had an engine come back with KB's with the top ring gap pulled out of the pistons. Of course we had to blow up a few 400 CSB's on the local race track to figure that out..."

    I'd probably call up Summit and order a set of ARP Wavelocks for the rods (cheap insurance) and have your FLEM install them for ya'. I've seen too many rods come apart on big blocks in my time. Usually from turning too many RPMs with stock rod bolts. Rotating assemblies get heavy at 6000 R's /forums/images/graemlins/laugh.gif

    The last thing I'll say... Its nice to see somebody keeping the compression ratio inline. Much more than 9:1 in a 4X4 with a low end/midrange cam, with the dinosaur piss we've got for gas these days is asking for detonation.
     
  3. OrangeCrushK10

    OrangeCrushK10 1/2 ton status

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    yeah, these days it's probably best just to run low compression unless you're really planning on some heavy racing and have deep enough pockets for $5 per gal racing fuel.

    Ofcourse, at that rate, just buy a nice supercharger, heh.
     
  4. madmike

    madmike 1/2 ton status

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    I've been doing some research before I build my 402bbc, which will also have 9:1 compression, hypereutectics, mild cam for low end torque and aluminum intake. Every machinist I've talked to so far recommended balancing, as was said, it will run smoother and last longer. Around here, they're telling me $200 to balance, so you're in line. I do plan on balancing mine. Good luck! /forums/images/graemlins/grin.gif
     
  5. BigRed89

    BigRed89 1/2 ton status

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    Balance it! It's worth the extra money. In fact you'll be saving money in the long run because your engine will last longer.
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    Get some good heads, and 9:1 compression on 87 octane is nothing.

    If GM could run '83 305's at 9.2:1, you can do better now /forums/images/graemlins/smile.gif

    For the original poster, you might want to look into various BBC heads that are out...either AL or cast iron, the newer designs make more power and tolerate higher compression without detonation. If you REALLY look into it, buying new heads is not that bad of an investment if you are looking at having stock heads completely redone anyways.

    Don't know what it is on BBC's, but with 30-40hp gains with "just" Vortec's over stock headed 350's, I'd bet the BBC's can see some impressive gains as well. Obviously it's not all about HP in a heavy truck, and the new heads (such as the Vortecs) really help you build a low end torque-monster.

    Obviously more power costs more dollars, just depends on how much you can justify.

    Oh yeah, and balance the motor /forums/images/graemlins/smile.gif
     
  7. Thunder

    Thunder 3/4 ton status

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    I have every engine I build balanced. it only costs an extra 200 or so. It is totally worth it. Runs smother
    Last longer. May even make a little more power.
     
  8. Ditchdigger

    Ditchdigger Registered Member

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    Hey! thanks for all the help guys!

    I will balance it /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif
    I'm going to go with SpeedPro 9:1.1 Hypers. (no KeithBlack)
    and I have some good fresh ported an polished 118cc cast heads.

    The only reason I'm going with hypers are raising compression and more performance rather than shaving heads but the cost is getting up there, does anyone know how well our Blazers do with stock compression 454(Flattops)?
    with alum. intake and edelbrock carb and headers?
    I do have some Federal Mogul Flattops with single reliefs
    would I need to balance with those pistons?

    Anyone here do some porting and polishing?
    I did both Intake and exhaust and I think
    it will make a big difference?
    I also smoothed and polished the chambers
    and took of the sharp corner on the piston side
    has anyone here done that, I have no doubt
    it lowered compression so I'm probably actually 9:0.1
    or if I go stock, lower yet!

    Not to mention I need a 700R4 tranny besides!

    Performance is expensive /forums/images/graemlins/angryfire.gif
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    The word I've seen on actual porting is that unless you have a flow bench, it's not hard to make it *worse* than you started. Don't see how you can screw up polishing though /forums/images/graemlins/smile.gif

    Porting and polishing unfortunately will never come close to the performance difference available by the new design combustion chambers, all else head-wise being equal.

    If you already paid to have the heads done, use them. If you stole them (as in great deal), and can get the same or more than you paid for them, see what a new set of heads will run. You might have a better choice of CC's, so that you could still get at a better chamber, but even higher compression.

    Believe me, once you start comparing "old" head design to new, the difference is night and day. Unfortunately thats where the $$ come in /forums/images/graemlins/frown.gif
     
  10. 4DiggerDan

    4DiggerDan 1/2 ton status

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    Dorian's half right. If you don't have a flow bench (or access to one) its real easy to make it worse... He's also right about newer head designs being more efficient... Where he's wrong is thinking that aftermarket is the way to go with BBC's Most aftermarket big block heads are built for cars running big cubes and big cams, not low end grunt monsters that have to run on pump gas with your camper in the back of the truck and towing a boat. There's no BBC comparison like old CSB to Vortec. What you will see is big CC runners and big valves, with smaller chambers that are pretty much the same as early CBBs. For what you want to do, I'd stay with early CBB oval port heads

    The other thing I found interesting was the assumption that since an '89 305 is 9.2 then you should be able to build a big block to 9.2 as well... The LT1 thats in Vettes and some Camaro's comes factory at 10.2 to one. You know the difference between all 3 engines??? Fuel delivery (and to a lesser degree, cam timing)... The LTI is an EFI that pretty much points the injector at the back of the intake valve. the 89 305 is most likely a TBI, which atomizes fuel somewhere between an LT1 EFI and a carb...

    One of the biggest mistakes back yard porters make is polishing the intake runners up mirror finish. Intake runners should be no smoother than 120 grit finish... Why??? Fuel atomization, AGAIN... If they're too smooth, it lacks the turbulence that keeps fuel in suspension. When gas starts puddling up, bad things happen. Exhaust is a whole different story though. If they're shined up mirror smooth it doesn't really give carbon anything to stick too.
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    http://www.airflowresearch.com/news/BBC_release.htm

    http://www.replikamaschinen.com/Web_Content_110401/Chevy/Big%20Block%20Vortec%20Combustion%20Chamber.jpg

    I find it hard to believe that combustion chamber design such as the lower link, is no better for low end performance than the older style heads. That top one I threw in there because they talk about useable low-mid power. (no indication of the chamber design, just CC's) You are right, I don't know if the aftermarket heads have larger than stock runners (such as the above ones linked to AFR) but I'm sorry, I refuse to believe that newer heads are anything BUT superior to older heads, as *long as you match the head design to your motor's intended use*. If you can justify the right aftermarket heads to yourself, then you definitely won't be hurting anything.

    And you read the year wrong it's *'83*. That's not injected, and it was with poor head design. Factory Vortec motors don't use that head design, and run 9.6:1 compression on iron heads. AL heads would get you even more compression than that. Of course, carbureted will not be exactly the same, but the difference between AL and iron will still be there.

    Don't know what the new BBC's run compression wise, but I'm thinking it's higher than they were able to achieve 20 years ago.

    "The 7400 big block's redesigned cylinder heads have new high-flow ports that significantly increase the big block's breathing ability. Revisions in the high-swirl, fast-burn combustion chambers and computer-designed pistons raised the compression ratio to 9.0:1 (up from 7.9:1 for 1995). This boost in compression ratio improves thermal efficiency and performance, but does not increase the engine's octane requirement."

    http://media.gm.com/division/chevrolet/products/archive_prod_info/pguide/ckpickup/ckpeng3.htm
     
  12. Ditchdigger

    Ditchdigger Registered Member

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    Thanks for the info!
    I got the long block for about 400 bucks
    complete and the heads were complete and guides are
    fine, but there is no way I'm buyin new heads
    this engine ain't going to make me any money
    but the future who knows what it will hold /forums/images/graemlins/smirk.gif
    but is there a big problem with doing the
    exhaust and INTAKE to almost mirror-finish /forums/images/graemlins/blush.gif
    I did both about the same!
    will it not Idle right or what!
    I mean my edelbrock 750carb should do most of it
    and my alum. intake manifold is very rough inside except
    where I portmatched, I can hardly believe there would be
    a noticeable problem from that,
    I mean when that air fuel mixture hits the beginning of the intake manifold runner it gets to the chamber QUICK!
    not to mention gas puddling where's it gonna puddle too
    its dang near straight down to the chamber?
    Its got some roughness to it but is smooth to touch.
    the first link of dyeagers shows a pic and that looks pretty darn close but pictures can be deceiving!
    Is it such a thing that I should take my diegrinder out
    again and rough it up!

    Thanks
     
  13. 4DiggerDan

    4DiggerDan 1/2 ton status

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    Dorian, is that 2nd link a picture of the AFR head? If so, then thats a nice head..

    You ever read the back page of the World Products catalog? In their FAQ there's something there that makes a lot of sense when you think about it. First of all, 80% of the guys out there with a Superflow SF600 have the one that only reads CFM. Not many pony up the extra 800 bucks for a manometer, and even fewer yet pony up 1500 bucks for a dual manometer set up. There's another part to port work that many people overlook. Velocity past the valve head... World products (and all the greats in cylinder head work, like Mondello) will tell you that it isn't always the head with the highest CFM rating that makes the most horsepower. Its not uncommon for a head flowing LESS air with MORE velocity past the valve head to create MORE horsepower and Ft/Lbs. As with ALL things in building an engine, its a compromise. I'm not denying that usually aftermarket heads move more air than OEM stock heads and usually with better velocity. A lot of times (especially after 1970) manufacturers had smog laws and all that BS to deal with. You know where the biggest pay off in cylinder head port work is? The pocket area... A properly pocket ported set of CBB "semi closed" oval ports can make a lot of power when set up right. Especially in a 4X4

    With all that being said AFR KNOWS THEIR SH!T!!!!!! Where I live and work, NOBODY here has that kind of money You gotta ask yourself, is the extra 60-70 horsepower and maybe 20-30 Ft/Lbs worth that extra 2500 to 3 grand on a 9:1 454?? Most of those heads are built for guys bolting them on a 509 or bigger, IMHO.
     
  14. dyeager535

    dyeager535 1 ton status Premium Member

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    </font><blockquote><font class="small">In reply to:</font><hr />
    is that 2nd link a picture of the AFR head? If so, then thats a nice head..

    [/ QUOTE ]

    Apparently, it's a worked GM BBC Vortec head:

    http://www.replikamaschinen.com/auto_chevy.html

    I only linked that due to the combustion chamber. This was pretty much my point...I don't recall a factory head having combustion chambers like prior to '96 or so.

    I learned from my SBC search that there are a LOT of variations of heads. I don't know enough about BBC's to know what port size would potentially have at least as much velocity as stock, but as in cams, you've gotta match the heads to your purpose. I just pointed to AFR because their BBC heads have a few variations in port size, and in chamber volume.

    I dunno about the cost, we'll go back to my example with SBC stock Vortecs, except this time I'll use semi-realistic numbers.

    $500 for heads, w/shipping
    $160 carb intake
    $40 for GM rail rockers

    You'd already be at $700.

    Look at AFR's 190CC street head: Any intake pattern you want, tons of different port sizes, 2.02 valves (perhaps 1.94's if you ask?), aluminum, screw in studs, angle or straight plugs, pushrod guides, good springs, no rail rockers required, and no special intake required.

    $1250. If you ask me, $1250 for all of that, compared to being shoehorned into parts with the Vortecs, and having to "upgrade" them to run anything more than a stock cam, is a deal! (you mentioned $400, on top of a $500 acquisition cost, you're almost completely there if you have to buy a new intake)

    If you really wanted to, you could go with some cast iron Worlds Product heads, and come out *ahead* of the Vortecs, at least cost-wise.

    In closing, if you can get BBC heads that are AL (lighter weight, even if you don't like their other charecteristics), produce more HP/TQ, with higher compression and less detonation, for a couple of hundred dollars over rebuilt stockers, why not? 60-70hp and 20-30ft/lbs for $200 is a STEAL if all you have to do is bolt the heads on. You know as well as I do, once you start getting into the "more power than stock" category, price starts to go up exponentially, for smaller and smaller gains...$200 additional spent on heads for that kind of gain is something you will feel every time you drive the vehicle.

    Obviously, I have no clue how much it costs to acquire decent BBC stock heads, and have them completely rebuilt for a decent cam, nor how much a set of "low end power" aftermarket BBC heads run that equate to the $1250 SBC heads from AFR.
     
  15. 4DiggerDan

    4DiggerDan 1/2 ton status

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    Well, I hate to be the new guy and start a flame war. That makes me look like a prick...

    BBCs and SBCs are entirely different animals. First off, there's NOT ONE SBC head on the market that will flow the numbers (both port velocity and CFM) that a stock early oval port 269CC big block will. Think about it for a second, stock valve size on most CBBs is 2.06 1.72 (with a hog job you CAN put 2.25 1.88's in most open chamber stock CBBs) IMHO the port and runner layout in CBBs is much better than that of CSBs. If you spent 10 grand on a CSB with a blower, and 10 grand on a BBC naturally aspirated (most likely fuel infected) the big block will still kick its ass and probably live longer. Blown engines with carbs tend to get leaned out and grenade... In you wanted to build a CSB blown and fuel infected, you'd be over you 10K budget.

    To the big block thing... I've seen intake runners anywhere from 240ish CC up to 420CC A 340 CC intake runner with 2.3 1.9" valves ain't going to be worth a sh!t on a truck, even with a 489 stroker. With the cam you should run with those heads the thing wouldn't even crawl without 7.38 gears in low range and a 3200 stall. It'd kick ass in a car that weighs 2800 Lbs with a Comp roller solid around .720" lift and 312 degrees duration. Of course you'd need flyweight pistons and titanium rods just to have any chance of keeping a low end together at RPMs up around 8500 RPM. You'd probably have a 10 second car IF (and thats a big if) you could hook it up.

    Small block heads... I never said that Vortecs are the best small block head going. I'm kind of partial to World Products stuff. Pro Topline is making some really sweet heads too. Most companies out there chasing after the performance head market build 10 times as many heads for the small block, and funnel piles more money into R&amp;D for CSBs than they do all the rest of the heads out there combined. CSBs are the cheapest horsepower out there... The reason I was going off about the Vortec thing is becuase that was the head that you were talking about. Its a head that I build a fair amount of. Usually for people that sit on the crapper and read too many comic books (HotRod, Car Craft, ETC) and already have their minds made up. It never fails to amaze me what people will pay for used castings for those things. I wouldn't give up more than 150 bucks for a pair of used heads. Hell, I wouldnt' even pay that for the rare and obscure 041 "X" casting camel humps.

    Next thing I wanna bring up. I wouldn't recomend running an aluminum head on a 4X4. You know why?? Because sooner or later a head gasket failure is inevitable. Aluminum and cast iron don't contract and expand in heating cycles at the same ratio (cast iron on cast iron does.) So every time you start your engine, or shut it off, you're grating away at your head gasket. The technolegy of head gaskets is getting better with the invention of MLS, but not many people make this type of gasket for bi-metal engines that origionally had cast heads. A lot of guys just stick whatever head gaskets on their engine NAPA has in stock. /forums/images/graemlins/eek.gif

    This tangeant got started because I said it was nice to see somebody keeping their compression ratio inline. I figured that he had an early 454 with OEM cast iron heads. In a 4x4 where engine loads can be pretty high, and carbs can get a little soggy when run off angle, and the low octane dinosaur piss we got for gas these days. 9:1 is really all a guy wants to run. High compression ratios and aluminum heads are for hot rods. IMHO, they have NO place on 4x4's where dirt simple engines that are built tough and reliable should be the norm. I'd rather trade off that 30-40 horse, and 20-40 ft/Lbs for reliability (cast heads, 9:1 compression) so I don't have to tear off a set of heads to replace a head gasket in the ass end of nowhere. I go wheelin' to get away from my problems, not deal with more...

    3 years ago, I thought that roller valve trains had no place in 4x4 engines (more moving parts that can frag and piss me off.) Now you can get roller lifters and rockers that'll hold up really well. After Ford and Chevy doing it in stock engines, and having very few failures for over 10 years, I changed my mind. 3 years from now there may be a revolution in gasket sealing ability and I'll take that extra horse, torque .5:1 increase in compression ratio.
     
  16. the professor

    the professor 1/2 ton status

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    Would be worth a check on the differece in weight between you stock pistons/pins/rings and the aftermarket ones..
    --
    If your running the engine at 5500rpm or less, a difference of 100grams (or more) is tolerable...as long as all the new pistons are the same weight..and you will never feel the difference..
    --
    Engines are not balanced 100%, but use a "balance factor", keyed to the rpm used...
    --
    This "balance factor" is a built-in imbalace...
    -
    Engine balance does nothing to improve wear, as when the crank turns, there are always points of imbalace...
    -
    Each pair of pistons, on one crank pin, at 90deg, come close to "perfect balance"...but the power impulses do not...resulting in a "harmonic vibration" lengthwise in the crank...thus the "harmonic balancer", to dampen that...also, the power pulses run up and down the crank, causing twisting and flexing, even in the strongest crank
    --
    The "power pulses" put far more stress on the bearings than engine imbalance
    --
    Also, besides the power pulse, there is the "negative force" on the rods on all but the power pulse...that produces wear on the bottom rod shell....
    --
    NO amount of imbalance will effect the wear on the rod bearings...the ONLY thing that will effect wear on the rod bearings, is lighter components (rods/pistons) that reduce the recpricating weight...but that is will be offset but the wear on the upper rod shell, with increased compression and power...
     
  17. dyeager535

    dyeager535 1 ton status Premium Member

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    </font><blockquote><font class="small">In reply to:</font><hr />
    Next thing I wanna bring up. I wouldn't recomend running an aluminum head on a 4X4. You know why?? Because sooner or later a head gasket failure is inevitable. Aluminum and cast iron don't contract and expand in heating cycles at the same ratio (cast iron on cast iron does.) So every time you start your engine, or shut it off, you're grating away at your head gasket.

    [/ QUOTE ]
    </font><blockquote><font class="small">In reply to:</font><hr />
    3 years ago, I thought that roller valve trains had no place in 4x4 engines (more moving parts that can frag and piss me off.)

    [/ QUOTE ]

    So since GM has (/had, whatever, the mid 70's to 80's don't count : ) been using AL heads on cast iron BBC's for 35 or so years, when do you think they will be acceptable?

    Saying that dissimilar metals are not good when talking engine components invites the argument that AL intake manifolds have been used both OEM and aftermarket for probably 40+ years, with cast iron heads. Obviously they aren't seeing the extreme temp variation at the cylinder, but I'd argue that the heat gain/loss at the intake is MORE extreme (faster), due to thinner material with more surface area, and less coolant. I haven't heard of any inherent problems in all AL intakes such as loosened bolts, leaking gaskets, and cracked castings...

    I think the AL head "durability" issue is a lot less than its made out to be. It's almost a given on any engine anymore, that if the block is still iron, the heads at least are aluminum. Not sure on the new truck motors, but we all know that cost is what drives GM, not performance, unless it helps them sell vehicles...

    I don't really see the difference between a truck engine and a car engine when it comes to head material. Sure, trucks DO put more stress on certain components than cars, but if you don't get carried away with extreme heat variations, I don't think the AL heads will be any more apt to fail than iron.

    As to the Vortecs, I think you and I are on the same page here...I used them as an example, because for awhile, they were ALL you heard about. They are great heads, depending on your goals, but there are a lot more choices out there now, and they certainly aren't the best for all applications.

    In the grand scheme of things, my argument is that if you can get better performance out of a cylinder head that costs a couple hundred dollars more than a stock one, and you can afford it, why not? (and who can't justify more kick in the pants every time you drive? : ) Additional compression certainly stresses the components more than stock, but the newer components (pistons, rods, bolts, etc) are designed to handle the stress daily.

    When talking about a "stock" carbed or injected daily driven engine, not getting more power with the same grade of gas when possible, to me is equivalent to throwing it away. I could build an engine with 8:1 compression, but when I can build it with 9:1+, run the same gas, on components that are designed to handle it, why wouldn't I?

    The argument REALLY doesn't even come down to AL vs Cast Iron, it comes down to technology. Combustion chamber design ALONE, regardless of any other aspect, has changed dramatically in the last 20 years, and the older heads just can't compete. I would LOVE to see some BBC (or even SBC) head tests that pit an old style combustion chamber against new, with all else being equal.

    I'm sorry to the original poster for us getting way off topic, but I know had I seen something like this before, I would have considered a lot more choices before I embarked on my engine build.
     
  18. 4DiggerDan

    4DiggerDan 1/2 ton status

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    </font><blockquote><font class="small">In reply to:</font><hr />
    So since GM has (/had, whatever, the mid 70's to 80's don't count : ) been using AL heads on cast iron BBC's for 35 or so years, when do you think they will be acceptable?



    [/ QUOTE ]

    Really??? GM has been using aluminum heads on cast iron BBC's for 35 years??? Then how come 90% of them have iron heads??? I've never once seen a BBC powered truck (pre '95 or so) with FACTORY aluminum heads.

    I've seen dyno tests done in which they used two cylinder heads that were as close to the same as they could find in both aluminum AND cast iron. In two out of three dyno pulls, the cast iron head made more horsepower (like 12-15.) Sometimes keeping more heat in the combustion chamber makes more horsepower.

    I refuse to believe the flow numbers posted BY the cylinder head manufacrurers, they rarely deliver as promised. Do you know the difference between "Gross Engine Horsepower" and "SAE Horsepower??" There is NO SAE flowbench standards out there.

    I can't argue with you theory about newer designs of chambers being, for the most part, better than older chambers.

    Back to the big block thread. He's probably into the stock heads for about 5 bills... So since you seem to think that you would spend the extra 200-300 bucks for a "does everything but wipe your ass, and gaurenteed to make 40 more horse" set of heads. You show me ONE example of an aftermarket CBB head that meets all of your "criteria" for 800 bucks....

    Oh... Dorian, I almost forgot. You see CBB aluminum manifolds pop all the time at the rear of the head (towards the fire-wall where they plug off the back water ports.) Then of course you dump a bunch of water into your oil. Then it etches all your bearings, then sh!t breaks. You don't see it as often on CSB's because its not spanning a 15 or so inch gap. One of the worst examples of this is seen all the time on Ford FE's (360,390,428.) I've had a couple of aluminum intakes pop on CSBs before too. I've never had a cast iron one let go. However, its a risk I'll take. There's just not anybody making good 4 barrel manifolds in cast iron out there.

    One more thing. All I do 5 days out of the week from 8 to 9 or 10 is pressure test and surface aluminum cylinder heads. One day last summer, I surfaced 28 aluminum heads. You forget, I see what happens to these theories that auto makers dream up.

    You have your opinions, and I have mine. My 400 CSB in my '76 Stepside has 120,000 on a rebuild now. I rod the sh!t out of it. I've adjsuted my valves once, and changed the oil every 2500-3000 miles. It makes all the power I need, gets 14 MPG, and I've never turned a wrench on it (other than adjusting valves and oil changes.) /forums/images/graemlins/smirk.gif
     
  19. Thunder

    Thunder 3/4 ton status

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    Hmmm..... reguarging the Al vs cast iron head issue.
    The japs have been using AL heads on cast iron blocks for years...........
    One of the most common repairs in the engines, is head gasket replacement............... I wonder why????????

    Thats all I got to say about that. /forums/images/graemlins/smile.gif
     
  20. dyeager535

    dyeager535 1 ton status Premium Member

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    </font><blockquote><font class="small">In reply to:</font><hr />
    Really??? GM has been using aluminum heads on cast iron BBC's for 35 years???

    [/ QUOTE ]

    Some 427 Vettes. I didn't say quantity, vehicle, nor that it was consistent, just that GM has been doing it for quite some time. They stopped due to emissions, insurance, and I'm sure cost, no other reasons. AL L98 heads are the next ones I can think of that GM used in large quantities on iron blocks.

    </font><blockquote><font class="small">In reply to:</font><hr />
    Sometimes keeping more heat in the combustion chamber makes more horsepower.


    [/ QUOTE ]

    Just read a dyno test of AL vs Iron heads. Back to back, the AL head made more power, but they speculated if the heads were as cast (I think the AL heads were higher compression) the AL would have made a bit less power, like 1-2%.

    </font><blockquote><font class="small">In reply to:</font><hr />
    I refuse to believe the flow numbers posted BY the cylinder head manufacrurers, they rarely deliver as promised.

    [/ QUOTE ]

    I don't blame you, but as most manufacturers now state, you have to base your results on the SAME flow bench. Just as in engine dyno's, variables exist, and you likely won't get the same numbers from two different testing setups. So what one company says you should see, won't necessarily hold up when tested by someone else.

    </font><blockquote><font class="small">In reply to:</font><hr />
    since you seem to think that you would spend the extra 200-300 bucks for a "does everything but wipe your ass, and gaurenteed to make 40 more horse" set of heads. You show me ONE example of an aftermarket CBB head that meets all of your "criteria" for 800 bucks

    [/ QUOTE ]

    http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=1238&amp;prmenbr=361

    </font><blockquote><font class="small">In reply to:</font><hr />
    Oh... Dorian, I almost forgot. You see CBB aluminum manifolds pop all the time at the rear of the head (towards the fire-wall where they plug off the back water ports.)

    [/ QUOTE ]

    Oldsmobile used cast AL intakes back in the 60's/70's. With the exception of a small (pretty much useless) piece that often cracked off, there were no problems with them. I used Olds as an example, because the Big Blocks have 14" of width between them. The SBO is 12" across, and used an aluminum intake almost entirely, after about 1980.

    I don't disagree with your experience. Aluminum in any application is going to take different care than something that was originally another material, heads being no different. But I also don't believe experience with different makes indicates problems that WILL occur on a Chev motor. I'd be almost willing to bet you that an Olds motor for instance, with AL heads, would be 10 times as likely to have head problems than a SBC set up the same way. The Chev simply has a better head retention setup (cylinders surrounded by bolts) which would definitely make a difference in resistance to warpage.
     

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