Big vs Small heads debate
Big vs Small heads debate I have noticed that alot of the LT1 guys are absolutely scared to put a decent sized head on this motor. You guys really dont get it do you? Is it just the lack of big heads and the shitty <200cc stock and tiny runner aftermarket castings that have brainwashed everyone into beleiving tiny ports are a good thing?
If you have a 350, dont hesitate to run a 200cc+ head. If you have a 383, dont be scared of a 220+cc port! A properly designed huge port head will always make more power than a properly designed small port head. I suppose everyone wants to run 2" exhaust on their cars to keep the velocity up too huh.
Very simple case in point, LS6s, 347ci, come standard with a 205cc intake port. L92 heads that are for TORQUE producing pickups are 260cc!!! These are on a production motor that has to have good drivability and pass emmissions, and you guys are scared of a set of 220cc heads for a track car? WTF is going on here!
I have a blown 355, and sure the price had alot to do with my decision, but it was getting a set of AFR 210s or 227s. I came across these fully ported Brodix SBC heads for a song so they are going on. Im not afraid of the 230cc ports they have in the least. So, discuss! Why do you hate a large efficient runner? What kind of BS convinced you that big heads are the devil, or why do you think they are good.
Gary
If you have a 350, dont hesitate to run a 200cc+ head. If you have a 383, dont be scared of a 220+cc port! A properly designed huge port head will always make more power than a properly designed small port head. I suppose everyone wants to run 2" exhaust on their cars to keep the velocity up too huh.
Very simple case in point, LS6s, 347ci, come standard with a 205cc intake port. L92 heads that are for TORQUE producing pickups are 260cc!!! These are on a production motor that has to have good drivability and pass emmissions, and you guys are scared of a set of 220cc heads for a track car? WTF is going on here!
I have a blown 355, and sure the price had alot to do with my decision, but it was getting a set of AFR 210s or 227s. I came across these fully ported Brodix SBC heads for a song so they are going on. Im not afraid of the 230cc ports they have in the least. So, discuss! Why do you hate a large efficient runner? What kind of BS convinced you that big heads are the devil, or why do you think they are good.
Gary
Last edited by Grr; Feb 7, 2009 at 09:44 AM.
hmmm interesting...curious on a answer. are your brodix heads lt1 heads or sbc heads? I had a set on an old 355 sbc that i loved. I am planning down the road to carb and put a vic jr intake on my lt1. the intake limits the power on the lt1 ive been reading
give me the money for a set of 227cc heads or a set of 220cc trickflows. its mostly about money. ill be using AI 200cc stock ported heads on my 383 because there proven to make badass numbers. id love to go with the reccomended 215cc trickflows but money doesnt allow. also the lsx motors can run such a large runner because design. i dont think its completely by choice that everyone doesnt go big. ppl are limited with choice and money.
8 Second Club
Joined: May 2004
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From: Savannah, TN
When i had a lt1 i used a set of fully ported AFRs. I figure guys like me that look at it like this why spend all that money on a set up that will be limited by the block. I hade a few block problems before the 1000 hp mark. I still have them and are mony wasted. Just the way i see it.
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To me, velocity is much more important than flow numbers.
A head can flow good on a bench but be crappier on the street to drive because of poor velocity.
That being said, I agree with your statement that a "properly designed" large port is not a bad thing, especially on a track car. Properly designed being key.
A head can flow good on a bench but be crappier on the street to drive because of poor velocity.
That being said, I agree with your statement that a "properly designed" large port is not a bad thing, especially on a track car. Properly designed being key.
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If only it were as simple as "big vs small".
Runner shape, not only size, has a huge impact on performance. Since most people are running stock castings, they are limited to smaller heads since the factory castings can only be opened up so much while keeping any decent port shape.
Not to mention, ask David Vizard - an engine that makes 400hp with a 220cc head will outperform an engine that makes 410hp with a 240cc head. It will have more under the curve.
No point in comparing parts from engines that are fundamentally different from LT1s-that is a moot point.
Runner shape, not only size, has a huge impact on performance. Since most people are running stock castings, they are limited to smaller heads since the factory castings can only be opened up so much while keeping any decent port shape.
Not to mention, ask David Vizard - an engine that makes 400hp with a 220cc head will outperform an engine that makes 410hp with a 240cc head. It will have more under the curve.
No point in comparing parts from engines that are fundamentally different from LT1s-that is a moot point.
Staging Lane
Joined: Jul 2006
Posts: 93
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Puck:
"609.154rwhp/390.917rwtq NA LT1: 350ci, GM HOT cam, big valved corvette heads, type "R" lifters w/ hydra rev kit, edlebrock air gap intake, ported stock TB with airfoil and 3" tornado, 700r4 w/ corvette servo and B&M Holeshot 2000rpm stall, flowmaster cat-back"
130 in the 10's?
lmao
Cheers -- Gary
"609.154rwhp/390.917rwtq NA LT1: 350ci, GM HOT cam, big valved corvette heads, type "R" lifters w/ hydra rev kit, edlebrock air gap intake, ported stock TB with airfoil and 3" tornado, 700r4 w/ corvette servo and B&M Holeshot 2000rpm stall, flowmaster cat-back"
130 in the 10's?
lmao
Cheers -- Gary
Puck:
"609.154rwhp/390.917rwtq NA LT1: 350ci, GM HOT cam, big valved corvette heads, type "R" lifters w/ hydra rev kit, edlebrock air gap intake, ported stock TB with airfoil and 3" tornado, 700r4 w/ corvette servo and B&M Holeshot 2000rpm stall, flowmaster cat-back"
130 in the 10's?
lmao
Cheers -- Gary
"609.154rwhp/390.917rwtq NA LT1: 350ci, GM HOT cam, big valved corvette heads, type "R" lifters w/ hydra rev kit, edlebrock air gap intake, ported stock TB with airfoil and 3" tornado, 700r4 w/ corvette servo and B&M Holeshot 2000rpm stall, flowmaster cat-back"
130 in the 10's?
lmao
Cheers -- Gary
Yea, through stock vette heads too
You guys are hilarious
. 
10 Second Club
Joined: Oct 2007
Posts: 2,630
Likes: 28
You really cannot compare the port size (cc) from one family of heads to the next family. It isn't apples to apples when you do that. Case in point, take a small block Ford vs a SBC. A SBF cylinder head is shorter along the width. What I mean is the distance from the intake manifold gasket to the entry at the intake valve is roughly 1 inch shorter. That is 1" worth of volume that is simply not there to be measured. You could have a monster port on that SBF head but it will only measure out to be like 205cc or so, because of how short it is. It does not directly compare with a SBC head that is 205cc.
Another way to think about it would be to have 2 engines that are physically the exact same width. The first engine has an intake manifold that is 20 inches accross and cylinder heads that are 5 inches wide. The second engine has a smaller intake manifold that is 14 inches accross but the cylinder heads are 8 inches wide. The cross sectional area on the engine with the 8-inch wide heads could be a lot smaller but the overall port volume would be higher than the 5-inch wide headed motor. Which would flow more?
Another way to think about it would be to have 2 engines that are physically the exact same width. The first engine has an intake manifold that is 20 inches accross and cylinder heads that are 5 inches wide. The second engine has a smaller intake manifold that is 14 inches accross but the cylinder heads are 8 inches wide. The cross sectional area on the engine with the 8-inch wide heads could be a lot smaller but the overall port volume would be higher than the 5-inch wide headed motor. Which would flow more?
You have to take into account port LENGTH when you Cc a runner.
If I told you guys the port size on my heads most of you would **** a BRICK! My car tools around just fine, makes 400 lb ft of torque to the wheels at 3000 rpm and gets decent fuel mileage. I can be rolling 30 mph and gas my car and set the 325/50 drag radials ON FIRE. I can reach in the door with it 30* outside and crank it up and it will idle as pretty as you please.
Most of these port size "rules" came from the carb days. Because the carb needs a high velocity vacuum"signal" to be effective. Not NEAR as critical in a port fuel injected engine.
If you cam a big port head efi application CORRECTLY you can get away with less camshaft.
But alot of what people on boards talk about is what they have seen on other boards. They dont know DICK about building an engine combination(not saying I do either).
If I told you guys the port size on my heads most of you would **** a BRICK! My car tools around just fine, makes 400 lb ft of torque to the wheels at 3000 rpm and gets decent fuel mileage. I can be rolling 30 mph and gas my car and set the 325/50 drag radials ON FIRE. I can reach in the door with it 30* outside and crank it up and it will idle as pretty as you please.
Most of these port size "rules" came from the carb days. Because the carb needs a high velocity vacuum"signal" to be effective. Not NEAR as critical in a port fuel injected engine.
If you cam a big port head efi application CORRECTLY you can get away with less camshaft.
But alot of what people on boards talk about is what they have seen on other boards. They dont know DICK about building an engine combination(not saying I do either).
