I just had a set of heads ive been working on for the summer flowed, there 487X castings are in perfect condition have 2.02/1.6's, .550 lift springs and chrome-moly retainers, im contemplating selling them or putting them on my 406 street machine, the 406 was predicted at 425 horse by the guy who flowed my heads which he did extensive dyno work on 406's with John Lingenfelter so i think hes in the ballpark, the only reason i wasnt sure of putting them on my 406 is im not sure if the Runners are big enough for 406 cubes but it is only a 6500 RPM engine, im guessing the runners at 180 CC, but thats a guesstimate, i need to whip out the buret first but anyway give me your opinion, oh yeah heres the numbers (without a 30 degree backcut on the intake valve, which is a 20 horsepower pickup)
2.98 ScaleIntake:.200-128 CFM-278 Potential Horse.300-186 CFM-405 Potential Horse.400-227 CFM-495 Potential Horse.450-231 CFM-501 " ".500-232 CFM-505.550-231 CFM-501.600-231 CFM-501
3.06 ScaleExhaust:.200-105 CFM.300-135 CFM.400-154 CFM.450-161 CFM.500-166 CFM.550-171 CFM.600-175 CFM
So whats your opinion on what i should do with these heads?
Sure im only 15, sure ive only been turning wrenches for a couple years, but i did stay at a holiday inn express last night
casting #487X , is that a cast iron bowtie ? when we used to screw around with oem heads the magic casting #was 461X , 65 375 hp 327 , the old fuelie head . the 292 was a turbo slant plug head , the 492 was the Z28 head , the 806 was the late model L82 head . I don't screw around with oem heads anymore . the aftermarket is full of bargain priced stuff that outflows the *** out of worked over factory stuff , with none of the cracking we used to get back in the day .Is John Lingenfelter doing any better ? last we heard he was in a coma after the cavalier crash
Look at it this way, how much money do you have invested in the machine work on your heads. Now you can buy heads for $500 to $700(a pair) that will out flow your heads right out of the box. Just think what they will do with a little porting. So don't screw around with factory crap, cause by the time you mill them, do the valve job, change out the guides, and do the porting, your spending just as much money as a new set would cost.
machine work? $0, do my own valve job, guides are fine, no milling needed, port work done all myself, the heads were off of my brothers car after it hit the scrap yard after he crashed it, low miles before the crash no harm to the engine, i have no money invested in the heads and aftermarket heads are overkill, aftermarket heads dont flow at .400 lift and if they do there a waste of money cause because there small CC runners, standard valve sizes, and port work on OEM heads can get the same efficiency, aftermarket heads are needed for .700 race engines not mild street, or hot street
Ok so your a machinist, not everyone has the tools to do head work. But for your info no matter what you do to those heads they will not make as much power as a set of aftermarket heads. There have been serveral dyno tests to support this. Also here are some flow numbers of some popular aftermarket heads.
Dart pro1 227cc
As you can see these heads flow more than your heads do threw the whole lift range. You see where your lacking is in runner volume. No matter how far you open the valve, your only going to flow what the runner allows and with your heads after 0.400 lift the runner only allows 230 cfm. That is the same reason the AFR heads above 0.500 lift only flow 260 cfm.
As where the Dart heads level off at over 0.600 lift. Basically the bigger the runner the more air flow you'll have at 0.700 lift, also a bigger runner doesn't alway lose in the lower lift range as seen here. I would take the aftermarket Dart heads over your heads any day, they flow 40 cfm more at 0.500 lift than your heads which I guess to your calculations is another 90hp.
Also who runs a cam with less than 0.500 lift.
Edited 9/18/2003 12:49:59 AM ET by TubbedCamaro
1. both of those are aluminum
2. both of those heads are probably at least $1000 bare, and if i buy em bare i will have to buy new stainless valves because im sure there bigger than 2.02 and 1.6's, if i buy em assembled big $$$
3.what did i pay for my heads?
4. there is many cams that run less than .500 lift, street hydraulics, my cam is .500 max but it will be running then .400-.450 most of the time especially if its a street engine
5. can you even get those heads in 76 CC chambers?
6. both of those heads lose a lot of port velocity behind OEM ported heads, which is what needed for a hot street engine
7. i understand that people dont have the tools to port heads but for me my argument is this
Ok there aluminum, so here is the biggest cc intake runner head I can find for a small block chevy. It is a Pro Action Iron Lightning 235, these heads have 235cc intake runners and Chevy High Performance cc'd the runners and they are more like 245cc. These heads sell for $575 a pair from summit, and are iron heads. Here are the flow numbers, right out of the box with no port work.
I know these heads don't flow as much as your heads do down low, but what did your heads flow before you ported them. Most likely not as much as these do. These heads have the ability to flow 325 cfm on the intake and 225 cfm on the exhaust with a little port work.
So you got someone's hand me downs. And you have access to a machine shop. I guess your time is not worth anything either.
Also do you have a variable lift cam or something. I don't see how you can lose lift at maximum lift. And how much duration does this cam have.
Yes they are avalible in 76cc, most aftermarket heads give you that option.
How can they loose port velocity if they are out flowing your heads.
It sounds like your building a mild daily driver, and their is nothing wrong with that. But if you want to make serious horsepower you'll have to go with bigger heads and a bigger cam. Your heads are ok for a cam up to 0.500 lift, but anything over that and they are restricting air flow.
Remember they are stock castings, and there is nothing special about that.
yeah i never think of what port work could do for those heads but my heads are almost the exact same at .500 lift and those heads have twice the intake CC and probably much bigger valves, yes port velocity is lost, port veloicty is throttle response and torque, large ports make low end sloppy and yes im worrying about low-end with this motor due to only its a 6500 engine, but i guess i got your answer if you say my heads are fine for a .500 lift engine, i dont have a varible lift cam, it what it is that a valve does spend its whole time at max lift it spends it .50 to .75 below max lift thats why my heads i think are better for a .500 lift engine cause as you go down the flow numbers of those huge runner heads it gets worse, as you go down to .400 and .450 on mine they stay pretty much the same, oh yes and i dont mind about the time it takes, its my hobby, and if i work hard a set of heads can be done in a few days easy, its people that have never ported a head that thinks that it takes 3 months, these first set took me a while, i was worried it was the first set ive ever done that had large meaning to me, ive done a couple sets since then its gotten easier and much quicker
just my 2 cents...... if you want to stick to factory type heads do yourself a favo and go with the vortec, they flow more out the box than a re-worked camel hump....they have 170 cfm intake runners good stock head to start with
1.94 intake 1.50 xhaust
lift in. flow cfm lift in. flow cfm
0.100 70.0 0.100 49.0
0.200 139.0 0.200 105.0
0.300 190.0 0.300 137.0
0.400 227.0 0.400 151.0
0.500 239.0 0.500 160.0
0.600 229.0 0.600 162.0
see these are stock numbers not far from your extensively worked 487x......work on the vortec would flow a circle around those heads....
I agree with you that the vortec heads are a great head and they are really inexpensive. But with a 406 they might be robbing you of HP. The 170cc intake runners seem a little small to feed the cubes, and if your using a hot street cam with like 0.550 lift or more these heads would definetly be robbing you of HP. In my case I have a 13:1 406 with WP/Dart Sportsman II iron heads with 200cc runners,2.08/1.625 valves,and 64cc chambers. The heads have been heavily ported and match ported to Felpro's large race port gaskets. I think these heads should flow the 0.670 lift of my cam. And since the cam is a solid roller the valve sees 0.500 lift very quickly and stays over it for most of the duration. The flow numbers under 0.500 lift aren't that important. There is one thing i'm not sure on, and that is if these head will flow the 7-8 grand my motor will spin or rob me of HP. Someone told me that they are only good to 650hp. So will a bigger cc runner head allow you to make more HP? Probably
yeah you defintley need more CC of runner for 406 cubes cause you have no rod ratio to aid the intake volume
Ok lets talk a little about rod ratio, for one most rod ratios fall between 1.4 and 2.1 and engine builders say a rod ratio of 1.75 is ideal, where this may be compromised in racing applications. My motor has a 1.52 rod ratio which is not far from the ideal ratio, and to get the ideal ratio I would have to have a 6.5 inch rod or a stroke of 3.25" and then I wouldn't have a 406 anymore, and I don't think you can put that big of a rod in a small block 400. Also with smaller rod ratios intake vaccum rises sooner ATDC, allowing bigger carbs and intake port runner and plenum volumes to be used without loss of response. On the negative side a small or badly designed port will "run out of breath" sooner.
What things come down to is you need to match your rod ratio to your intake setup(carb, intake, heads). As in my motor I need to have large intake runner volumes, a single plain intake and a large carb, to compensate for the small rod ratio.
If my rod ratio was bigger like 1.95, small runner volumes, dual plain intakes and smaller carbs are the way to go.
yeah you pretty much summed it up, except you make it sound like if you dont want to rod ratio isnt needed at all, longer rods reduce sideload friction also and thats something that will always help at high RPM, but yes if the intake system is tuned right engines dont need large rod ratio's how do you think 632 big block chevy's can work soo well
If I was to change a couple of things on my motor, I would go with a 6 inch rod and bigger CC runner heads. I've seen one dyno test on a 400 SBC were they ran the same motor and the only thing they change in it was the rod length. The stock rod make the most torque but least horsepower, The 5.7 rod made more HP than the stock rod but not as much torque, and the 6 inch rod made the most HP but the least amount of torque of all the tests. That is one reason I went with the 5.7 rod, probably won't change the rod length, But the heads I think they'll be coming in the mail. I think 235cc intake runners will feed my beast fine.
"Who uses a cam with under .500 lift" Good question...
How does a 15 year old kid have access to a machine shop to do all of this stuff? Sure porting can be done in ones garage with ad ie grinder, but what about all the other stuff? If your eally didn't spend anything on these heads than good for you, they make pretty good numbers for free...