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For what you're describing....I wouldn't widen the LSA. You want a cam to come on hard in the midrange and don't care about anything after 5000 RPM. Typically the cams that do that end up on a narrower LSA. The small heads would "like" a slightly larger duration to help them not fall off a cliff at the top end..so we've got some tradeoff's here. I would talk to a custom cam guy to narrow it down to do exactly what you want. This is right in Chris Straub's area of expertise. He'll select lobes based on your heads and the stroke/cubes/rpm range you're dealing with and the LSA will end up at whatever it ends up with. The small headers and heads will throw a curve ball into the mix.
In the chart I posted you can see how the single plane actually made more peak TQ at the same RPM as the dual plane, but was down 15-20 lb ft in the lower ranges. If you look at the ported 2x4 intake numbers you'll see that even though this is a tiny intake as compared to even the dual plane...the low end TQ numbers are way below the dual plane. larger and better flowing fills cylinders better at low speed too (to a point). A lot of people confuse driveability and throttle response with peak TQ numbers. That is as much to do with tuning as anything else. Dyno numbers come at WOT and the 'feel" you get as you run through the gears at less than WOT can be a whole lot different. "Big" heads and intakes can come on hard and fast on the low end...and if the gearing is strong...they go right through those RPM range quickly anyway.
For what you're describing....I wouldn't widen the LSA. You want a cam to come on hard in the midrange and don't care about anything after 5000 RPM. Typically the cams that do that end up on a narrower LSA. The small heads would "like" a slightly larger duration to help them not fall off a cliff at the top end..so we've got some tradeoff's here. I would talk to a custom cam guy to narrow it down to do exactly what you want. This is right in Chris Straub's area of expertise. He'll select lobes based on your heads and the stroke/cubes/rpm range you're dealing with and the LSA will end up at whatever it ends up with. The small headers and heads will throw a curve ball into the mix.
In the chart I posted you can see how the single plane actually made more peak TQ at the same RPM as the dual plane, but was down 15-20 lb ft in the lower ranges. If you look at the ported 2x4 intake numbers you'll see that even though this is a tiny intake as compared to even the dual plane...the low end TQ numbers are way below the dual plane. larger and better flowing fills cylinders better at low speed too (to a point). A lot of people confuse driveability and throttle response with peak TQ numbers. That is as much to do with tuning as anything else. Dyno numbers come at WOT and the 'feel" you get as you run through the gears at less than WOT can be a whole lot different. "Big" heads and intakes can come on hard and fast on the low end...and if the gearing is strong...they go right through those RPM range quickly anyway.
JIM
Jim, appreciate your input. I have heard many times that the AFR 180 heads flow as well as many other manufacturer 200's.
But, what I keep hearing is that these heads, and the 1-5/8 inch headers may be choking the 406. So, I have toss up in my head that maybe I should just stick with a 383 mod due to this limitation. BUT, at the same time I also hear that displacement, with all other things the same, moves the entire torque curve up higher....correct?
This is always give and take. I keep telling myself that what matters is creating a torque curve that comes on at 2000 strong and is flat or rising to 5000 RPM. The question is obviously what is the best way to achieve this. You chart shows that the dual place is ONE factor that helps make this happen, so that is one given.....the other would be displacement to do the same. Then of course, the right cam.....seems like the general consensus is my current .500 lift is a little weak....need to increase that by some.
Straub chimed in on a thread of mine, and offered to have me call him, which I will.
Last edited by Torqued Off; 04-16-2017 at 04:03 PM.
I am not following your comment?? If you are suggesting that AFR 180 Eliminator heads, Edelbrock Performer RPM with a Lars build Carb, and 1-5/8 inch long tube headers into 2-1/2 inch stainless exhaust system is somehow CHOKING a 350 built for low end torque, then I guess that is your logic. But many would disagree. Using these same parts on an engine with more displacement will create more torque, but will limit 6000 RPM HP, which I do not care about. Note: I would probably use a slightly bigger cam in the 406.
I am going to guess that your idea is to use big CC heads, like 210 or more, a single plane manifold and 1-3/4 inch headers, and THAT would give me MORE bottom end torque, and 7000 RPM HP???
This type of debate never ends, because one side only thinks about MAX HP at big RPM. For those on that side, answer this simple question. With your big RPM engine, will the actual torque numbers be higher at 2000-4000 RPM than a 406 with my current parts. That is really the bottom line. IF you can get MORE torque at 2000-5000 RPM, especially at the lower end of this range, then that is what I want.
But, from everything I have read and learned you trade torque for HP in this 2000-5000 RPM range, you can't have both. Explain how I am wrong.
I want a torque curve that starts high at 2000 RPM, stays flat or rises up to 5000 RPM. If the HP is less at 5000 RPM and above, but still will easily sustain 75 MPH in a 4-speed with 355 gears, then that satisfies all me needs. Top speed means nothing to me, as I am not racing anyone. I want acceleration, like big block acceleration, at the shift points I use on the street.
I can tell you that with my current motor, I can feel it starting to really come alive above 4000 RPM, so with my 4-speed, I can run it to that number in each gear, but will be doing over 55 MPH by second or third gear. So, I have what I want, I just want it at lower RPM. And frankly, it does not push me back in my seat as much as I expect out of a muscle / sports car.
First of all it is a sbc , second no specific size is going to be the best every time. You want TQ , Which Also needs air in and out and the more torque you want to enjoy requires parts that allow the motor to breath. Which means more is better
To end HP requires the same formula
So in the end rather then choke off a 406 with that head get a 220 AFR and a CAM SHAFT PROFILE that is not designed for top end hp but low end torque.
Here is the mistake you are making (IMOP) You think smaller means more torque and less up top , well guess what smaller means less torque ad less up top , and when you have the cubic inches 406 and up in a sbc you need to move air as efficiently as possible for torque ,no different then if you had that 7500 650 hp goal which you do not ..
You could always just drop an underhood blower (on corn) and get that BB torque from the SB
On a serious note.. if you are between the 383 and 406 only because of possibly restricting the 406, then I'd say go 406. Use what you have, which will be a big improvement over the ZZ4, and if you need more there is plenty of room for improvement down the road by opening it up. If cost is a concern, stick with the 383.
The subjectivity of terms make it tough to give advice. One man's "good low end" is an other's "so radical ya cant drive it in traffic".
Their are a lot of big inch SBC driving around built to various levels of performance maybe the OP can get ride in some existing vehicles to help pick components.
I can offer a ride behind a 406: AFR 195, 11.5:1, mid 240s hyd roller, ported Victor Jr. It's in a '69 Camaro but the character still comes across. I would describe it as an "every day driver capable" but some might find it more than they want in traffic.
Jim, appreciate your input. I have heard many times that the AFR 180 heads flow as well as many other manufacturer 200's.
But, what I keep hearing is that these heads, and the 1-5/8 inch headers may be choking the 406. So, I have toss up in my head that maybe I should just stick with a 383 mod due to this limitation. BUT, at the same time I also hear that displacement, with all other things the same, moves the entire torque curve up higher....correct?
This is always give and take. I keep telling myself that what matters is creating a torque curve that comes on at 2000 strong and is flat or rising to 5000 RPM. The question is obviously what is the best way to achieve this. You chart shows that the dual place is ONE factor that helps make this happen, so that is one given.....the other would be displacement to do the same. Then of course, the right cam.....seems like the general consensus is my current .500 lift is a little weak....need to increase that by some.
Straub chimed in on a thread of mine, and offered to have me call him, which I will.
The 180's do flow well for their size. To really get it nailed down we'll need to find the minimum cross section of the intake ports to determine where they're going to become a restriction on a 406" engine. I doubt they'll be much of an issue at 5000 RPM....but larger would still be better. I get the need for strong street performance...but when I decide to really open it up I want to pull like a son of a gun until 6500-7000 rpm. You're not wanting to do that..so not really an issue. In fact...I've seen a lot of 400's running with 1-5/8" headers. Some even been pretty quick.....not what you'd ideally do...but a $1000 is a $1000.
Displacement doesn't necessarily move the powerband upwards. In fact...given same heads etc it will move it down. The added inches will pull more air through the intake tract and peak TQ/HP will occur at a lower RPM unless you re-cam it to crutch it to go further. Let's say you've got a good healthy pump gas engine making 1.2-1.3 HP per cube. You're talking about picking up 60-65 HP..without other changes (as long as it can still RPM fairly decently). I think the right cam could make it run strong with your heads and your RPM restrictions. Yes,,,it would have more than .500" lift for sure if it was mine. AFR says those heads are for 6000 rpm range 383's. The larger bore of the 406" is just going to help them out.
i can give you a good comparison because i own the two my driver is a 71 with modified 195 AFR full cnc heads,408"( +.040 over) line bore camshaft and mains and decked all on CNC machine.at first 572 hp then detuned to 525hp at 5500rpm .by way of dual plane air gap removed single plane and changed cam to lunati .541/541 lift at .050.dur. at 231/241 and LSA at 112. all forged,all roller 1 7/8"primarys on headers.dual fan,aluminum w/p, ps no other power and real nice 700R4 ,3.55 gears with 2600stall. engine only went into second fan for 5 minutes in 95 degree bumper to bumper traffic.this car will blow the doors off my 67 coupe 427" 435hp with engine internal (all roller ) modifications appears OEM. with 4 speed, built by the world champ with all his tricks like angle milling . i made him reduce hp from 572hp to 525hp.i have no opinions other then his advise NEVER build a 406 unless you use 6" rods he also used HV oil pump (55A) and special pick up in 7 quart pan gives perfect 60-70 psi all day with VR-1 oil.to sum it up the 406 + will definitely give you the kick in the *** of big block but the weight of small block in addition to very fast rev up .i think you will need 195 AFR heads to take advantage of cubes.
Last edited by Captain bob; 04-17-2017 at 10:43 AM.
IMO, I'd leave your current motor alone before I put 180cc heads on a 406. Those cubes need a 200-220 intake runner in order the achieve the required minimum cross-section needed for it to rpm at all. I actually think your current engine would be pretty fun with a nice hydraulic roller in the 230 duration range and some more rear gear (3.73 or a low 4-series).
I appreciate all the input, but the differences in input leaves me still unsure of what to do. I am not engine expert, just trying to learn.
The Big Inch SBC book written by Graham Hansen, has an engine build with dyno information of a 406 with stock Vortec 170 cc heads, with a flat tappet 230 cam and 1-5/8 inch headers producing 525 ft. lbs of torque at 3500 RPM.......and I am supposed to believe I need 200 cc AFR heads to make the torque I want????
Very contradictory information, and somebody is wrong.
Last edited by Torqued Off; 04-17-2017 at 09:14 PM.
I appreciate all the input, but the differences in input leaves me still unsure of what to do. I am not engine expert, just trying to learn.
The Big Inch SBC book written by Graham Hansen, has an engine build with dyno information of a 406 with stock Vortec 170 cc heads, with a flat tappet 230 cam and 1-5/8 inch headers producing 525 ft. lbs of torque at 3500 RPM.......and I am supposed to believe I need 200 cc AFR heads to make the torque I want????
Very contradictory information, and somebody is wrong.
Well not wrong, but not explaining the whole thing.
A bigger head will make the same or close to same torque.....but the potential for much more horsepower is the benefit.
I would not build a 406 without at least a 200 cc head on it.....it just makes no sense unless you are putting it in a pickup....
Well not wrong, but not explaining the whole thing.
A bigger head will make the same or close to same torque.....but the potential for much more horsepower is the benefit.
I would not build a 406 without at least a 200 cc head on it.....it just makes no sense unless you are putting it in a pickup....
Jebby
I hate to disagree, but what about this 525 ft lbs torque at 3500 RPM with a 170CC VORTEC IRON head. Similar builds and dyno stats I have seen with larger heads do NOT make that amount of torque unless its way up at 5000 plus RPM. Yeah great horsepower, but not massive torque at these lower to mid RPM. That kind of torque is going to push you back in the seat while going through every gear, which is what I stated I wanted at the start of this thread.
People keep skirting around this and not reading what I am asking. Some people seem to understand it, others can't get off the max HP at 6000 RPM concept. And I am just trying to understand it.
If I put 200 cc AFR heads on this 406, and I can get 525 ft lbs of torque at 3500 RPM, AND big HP at 6000 RPM, then I guess I believe what you are saying.
To all following.....is this correct?
Last edited by Torqued Off; 04-18-2017 at 07:38 AM.
You can accomplish what you want with the heads you have. I believe they are trying to tell you the smaller head is going to give up some power that is potentially there. There is a youtube video of a 406 that Chris Straub made a cam for that does exactly what you want. I believe it was using a 195 pro-filer. Your afr heads should deliver close to the same results. Give him a call and get some feedback.
If I remember correctly the cam was ground on a 107 lsa.
Phone calls are cheap compared to parts.
I hate to disagree, but what about this 525 ft lbs torque at 3500 RPM with a 170CC VORTEC IRON head. Similar builds and dyno stats I have seen with larger heads do NOT make that amount of torque unless its way up at 5000 plus RPM. Yeah great horsepower, but not massive torque at these lower to mid RPM. That kind of torque is going to push you back in the seat while going through every gear, which is what I stated I wanted at the start of this thread.
People keep skirting around this and not reading what I am asking. Some people seem to understand it, others can't get off the max HP at 6000 RPM concept. And I am just trying to understand it.
If I put 200 cc AFR heads on this 406, and I can get 525 ft lbs of torque at 3500 RPM, AND big HP at 6000 RPM, then I guess I believe what you are saying.
To all following.....is this correct?
That is exactly what I am saying.....it would make so much average torque that losing 25 ft/lbs. of it would be unnoticeable.....
Remember....Horsepower is torque measured over a period of time.....if you make much more power with close to the same average torque....it will accelerate much harder......
I run a 200 head and single plane intake with a 3:36 gear.....in second, from a 30 roll.....it simply twists the tires off if floored (no double clutch)......and it revs to 5800-6000 before it noses over......to me, that is a great street engine.....
I always wanted to build an engine like this and glad I did.....not a tractor and not too high strung. Torque off the bottom to the top....flat as Kansas.
Vortec heads on a 406 are like 283 heads on a 350.....no volume.
It is not only about filling the cylinder.....it is about VE (Volumetric Efficiency)....how much can you fill the cylinder at BDC. If you have volume and air speed....you have a brutally power engine.
That is exactly what I am saying.....it would make so much average torque that losing 25 ft/lbs. of it would be unnoticeable.....
Remember....Horsepower is torque measured over a period of time.....if you make much more power with close to the same average torque....it will accelerate much harder......
I run a 200 head and single plane intake with a 3:36 gear.....in second, from a 30 roll.....it simply twists the tires off if floored (no double clutch)......and it revs to 5800-6000 before it noses over......to me, that is a great street engine.....
I always wanted to build an engine like this and glad I did.....not a tractor and not too high strung. Torque off the bottom to the top....flat as Kansas.
Vortec heads on a 406 are like 283 heads on a 350.....no volume.
It is not only about filling the cylinder.....it is about VE (Volumtric Efficiency)....how much can you fill the cylinder at BDC. If you have volume and air speed....you have a brutally power engine.
If I put 200 cc AFR heads on this 406, and I can get 525 ft lbs of torque at 3500 RPM, AND big HP at 6000 RPM, then I guess I believe what you are saying.
To all following.....is this correct?
Conceptually yes. Appropriately sized heads will make every bit as much torque as undersized heads and they will carry that torque much further up into the power band. You really need to experience the difference in a car with the seat of your pants, but an engine that makes torque and then immediately falls over on itself just doesn't really feel like a performance engine to many of us.
I hate to disagree, but what about this 525 ft lbs torque at 3500 RPM with a 170CC VORTEC IRON head. Similar builds and dyno stats I have seen with larger heads do NOT make that amount of torque unless its way up at 5000 plus RPM. Yeah great horsepower, but not massive torque at these lower to mid RPM. That kind of torque is going to push you back in the seat while going through every gear, which is what I stated I wanted at the start of this thread.
People keep skirting around this and not reading what I am asking. Some people seem to understand it, others can't get off the max HP at 6000 RPM concept. And I am just trying to understand it.
If I put 200 cc AFR heads on this 406, and I can get 525 ft lbs of torque at 3500 RPM, AND big HP at 6000 RPM, then I guess I believe what you are saying.
To all following.....is this correct?
You need flow in and out and a CAMSHAFT made to provide this. You also have a Small Block . .and want bb torque // Well typically a SBC needs more rpm to get torque numbers equal to a BBC that is because the stroke is not as long
Use what you have, follow the guy in that article nothing wrong with that at all unless it dont work out, but I am sure it will ..
You need flow in and out and a CAMSHAFT made to provide this. You also have a Small Block . .and want bb torque // Well typically a SBC needs more rpm to get torque numbers equal to a BBC that is because the stroke is not as long
Use what you have, follow the guy in that article nothing wrong with that at all unless it dont work out, but I am sure it will ..
This form of communication is so tedious. I am not sure if you are being sarcastic or not? If anyone is suggesting this Vortec engine is NOT producing 525 ft lbs of torque at 3500, just say it directly. If I am to believe it is B.S., then I guess I don't know who to believe. And with every posting, it gets more unclear.
Last edited by Torqued Off; 04-18-2017 at 08:11 PM.
A 406 with better average torque number and more horsepower will walk a high torque 406 that runs out of breath at 4500 rpm.....
Simple acceleration and curve.....
Do not get hung up on peak torque numbers down low....
A good 406 with 200cc head will make 400 ft/lbs. torque at 3000 rpm and carry that above 400 well past 6000....
This is the point some of us are trying to make.....why not have your cake and eat it too?
You will see 60-70 horsepower over a Vortec head compared to a 200cc Dart or AFR.....and maybe 30-40 ft/lbs. less torque.....the compromise is a no brainer if the torque curve is flat....and that is where VE and Volume come in......let the engine accelerate and it will go faster....proven fact.
A 500 inch Pro Stock engine make almost twice as much power than torque.....A built diesel make twice as much torque than horsepower....put both of these engines in the same car and test them.....the P/S engine will always go faster assuming you stay on its torque curve....which is fairly flat....the diesel is flat too....but with limited rpm range....you would need a 10 speed trans to stay anywhere near the gas engine...
Like I said....Horsepower is work over a period of time.....if you have a lot of work.....then the horsepower will accelerate it with happiness
I thank you for listening and am not trying to sway you anyway.....
A small head small block will run like my Peanut Port 454.....it will get the job done.....I can tell you from experience that the small head engine will
be easy to tune.....
This form of communication is so tedious. I am not sure if you are being sarcastic or not? If anyone is suggesting this Vortec engine is NOT producing 525 ft lbs of torque at 3500, just say it directly. If I am to believe it is B.S., then I guess I don't know who to believe. And with every posting, it gets more unclear.
I believe wholeheartedly that it is.....it would be a monster with tall gear and a 5 speed....
So if I am following this path, here is what I need to do if I want a 406.
- First I have to get rid of my $1500 AFR 180 heads - $1500 loss
- I have to bag the 1-5/8 headers $1000 loss
- I have to buy another set of heads....most likely AFR 195, or some 200 cc head at $1500.
- I have to buy 1-3/4 or 1-7/8 headers at $1000
This puts me $5000 in the hole, and I haven't even bought a cam or a Dart block yet.
I don't know, maybe I just get happy with my 350.......do you all think my AFR 180 heads are good on my 350? Or did I make a mistake there too?
If the bottom line is just building a whole new motor as a 406, and spending $7000-$8000, then maybe I will just have to wait to some later time when it makes sense.
I was trying to use what I thought were great parts, but apparently, it is a bad idea. Maybe I just stroke my block to 383, and keep all the same. I don't know.
Thanks for all you help.
Last edited by Torqued Off; 04-18-2017 at 08:30 PM.
04-16-2017, 12:41 PM
