243 head question... larger valves or more compression
04-23-2017, 07:49 PM
#1
243 head question... larger valves or more compression So... I am debating where to send my 243 heads. Still bouncing between PRC, ,TEA, and AI.
TEA heads can't be milled with my cam, PRC can be milled a little, AI can be milled the most.
TEA flows the best, AI and PRC are pretty close.
TEA is the most expensive, PRC is the least... by about $300.
So... which is better... more airflow, or higher compression? Stock LS1 short block. low to mid 230's cam.
TEA heads can't be milled with my cam, PRC can be milled a little, AI can be milled the most.
TEA flows the best, AI and PRC are pretty close.
TEA is the most expensive, PRC is the least... by about $300.
So... which is better... more airflow, or higher compression? Stock LS1 short block. low to mid 230's cam.
04-23-2017, 08:52 PM
#3
A smaller bore wont gain much from a larger valve too much with the stock valve angle. a 2.02 is about all youd want to go unless 4.00 or larger. It still shrouds. Any of those companies can recess the valves and mill if you want for more compression on your cam. Any of them will touch the chamber and make cr lower, so youd want to combat that somehow. They are all good choices otherwise.
04-23-2017, 09:12 PM
#5
A smaller bore wont gain much from a larger valve too much with the stock valve angle. a 2.02 is about all youd want to go unless 4.00 or larger. It still shrouds. Any of those companies can recess the valves and mill if you want for more compression on your cam. Any of them will touch the chamber and make cr lower, so youd want to combat that somehow. They are all good choices otherwise.
04-23-2017, 09:13 PM
#6
You have options with nearly any of them, you just have to ask. AI uses larger valves too as an option. Youve just gotta ask. Since your cam seems larger im guessing you arent worried about torque or low lift flow, so the larger valves will help the higher end power. As long as you have an intake to feed them youll be ok.
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04-23-2017, 10:01 PM
#8
Would a bump in compression yield better mid-band power than 10-15 CFM more mid-lift airflow?
With stock valves, I think the heads could be milled .04", since my cam is below 235/235 (unfortunately, I don't know the exact specs. I think its 234/235, the guy who designed the cam thinks it is closer to 232/233...but neither of us can find the specs)
With stock valves, I think the heads could be milled .04", since my cam is below 235/235 (unfortunately, I don't know the exact specs. I think its 234/235, the guy who designed the cam thinks it is closer to 232/233...but neither of us can find the specs)
04-23-2017, 11:03 PM
#11
Compared to PRC 2.5, AI heads should have lower velocity but use .02" smaller valves.
Compared to TEA 2, the AI heads should have lower velocity, but use .04" smaller valves.
I took ((CFM/test bore)times 4) divided by intake CC divided by valve size to get a number to compare velocity. I'm sure that equation does not accurately measure velocity, but it seemed like it would be a reasonable number to use to compare heads.
Last edited by FCar2000TA; 04-24-2017 at 12:41 AM.
04-23-2017, 11:08 PM
#13
Velocity is also dependant on port design as well. Dont get too caught up in numbers. Youll likely make the same off all of them. But youve also gotta make sure the bore size they are being flowed on are the same...otherwise you cannot compare. Also if they flow xxx on a 4.00 bore but you are 3.905 the numbers really dont matter then, and you can expect less.
04-24-2017, 12:35 AM
#15
That's not how you look at velocity. You look at coefficient of discharge.
See this post for more information on it: https://ls1tech.com/forums/generatio...l#post19592368
The TEA Stage 2 heads are the ones with the larger valves. Stage 1 is the stock valves like AI.
What would I do? Well since I had the same dilemma back in 2013 when I bought my heads, I did TEA Stage 2. And would do them again, everyday of the week. They've made 520rwhp on a 346 with a 234 duration cam. And over 550 on a 408 with a pretty mild cam... think 239 duration. But more importantly, they are fast as hell at the track. The flow numbers don't mean jack. They make real power and run fast. Flycut your pistons and run as much compression as you can. Aim for 8.7:1 DCR.
Btw, the valve job they do is the same ones TEA cuts into their TFS heads. And that's where most of the power is.
One other thing to note, the 226-229cc port runner size of the TEA is about equivalent to the AI heads.
See this post for more information on it: https://ls1tech.com/forums/generatio...l#post19592368
The TEA Stage 2 heads are the ones with the larger valves. Stage 1 is the stock valves like AI.
What would I do? Well since I had the same dilemma back in 2013 when I bought my heads, I did TEA Stage 2. And would do them again, everyday of the week. They've made 520rwhp on a 346 with a 234 duration cam. And over 550 on a 408 with a pretty mild cam... think 239 duration. But more importantly, they are fast as hell at the track. The flow numbers don't mean jack. They make real power and run fast. Flycut your pistons and run as much compression as you can. Aim for 8.7:1 DCR.
Btw, the valve job they do is the same ones TEA cuts into their TFS heads. And that's where most of the power is.
One other thing to note, the 226-229cc port runner size of the TEA is about equivalent to the AI heads.
04-24-2017, 12:37 AM
#16
Velocity is also dependant on port design as well. Dont get too caught up in numbers. Youll likely make the same off all of them. But youve also gotta make sure the bore size they are being flowed on are the same...otherwise you cannot compare. Also if they flow xxx on a 4.00 bore but you are 3.905 the numbers really dont matter then, and you can expect less.
With test bore factored in, TEA stage 2 are the best heads to get, but they cannot be milled to raise the compression.
The rest have lower velocity, but can be milled to get higher compression.
04-24-2017, 12:44 AM
#17
I would talk to tea first. like jake said you can flycut as well. Taking .04 off for an .04 larger valve is not how it works either.
If the tea head is the mos true, then use it. All the heads have to at least be cleaned up on the surface which is usually .005 or so...so roughly 1cc off. Id never honestly look at .040 off a head honestly. .020 should be more than enough if you were going to do it. Thats about 3cc.
Like i said im sure they can make arrangements for the milling the head just like the others do. They are all full service shops.
If the tea head is the mos true, then use it. All the heads have to at least be cleaned up on the surface which is usually .005 or so...so roughly 1cc off. Id never honestly look at .040 off a head honestly. .020 should be more than enough if you were going to do it. Thats about 3cc.
Like i said im sure they can make arrangements for the milling the head just like the others do. They are all full service shops.
04-24-2017, 12:46 AM
#18
Again, that's not how velocity works.
All have the same size runner and CSA. So the airspeed through the port is pretty much the same. The difference is the efficiency of the valve to flow. The TEA heads are a more efficient head when you look at the coefficient of discharge.
And compression helps with drivability more than anything. But when we're talking going from 10.1:1 to 11.1:1, you may see 3-4% more power. Of course, 10-15CFM is more like 20-30HP since the very general rule is 2HP per CFM.
The better way to look at it is the TEA heads would add about 45-50rwhp to your combo with no compression change. So 450? What's 3-4% of that? Another 10-15HP? And milling down to 59-60cc would be about .030" which is about as much as I'd go. Even with a flycut... which is about 1cc (.080" depth int/exh for a 2.04/1.575 combo) with a .040" gasket is like 11.8:1 CR... But you'd need probably a larger cam or a looser ICL to get your IVC up to make use of that much compression.
All have the same size runner and CSA. So the airspeed through the port is pretty much the same. The difference is the efficiency of the valve to flow. The TEA heads are a more efficient head when you look at the coefficient of discharge.
And compression helps with drivability more than anything. But when we're talking going from 10.1:1 to 11.1:1, you may see 3-4% more power. Of course, 10-15CFM is more like 20-30HP since the very general rule is 2HP per CFM.
The better way to look at it is the TEA heads would add about 45-50rwhp to your combo with no compression change. So 450? What's 3-4% of that? Another 10-15HP? And milling down to 59-60cc would be about .030" which is about as much as I'd go. Even with a flycut... which is about 1cc (.080" depth int/exh for a 2.04/1.575 combo) with a .040" gasket is like 11.8:1 CR... But you'd need probably a larger cam or a looser ICL to get your IVC up to make use of that much compression.
04-24-2017, 12:47 AM
#19
That's not how you look at velocity. You look at coefficient of discharge.
See this post for more information on it: https://ls1tech.com/forums/generatio...l#post19592368
The TEA Stage 2 heads are the ones with the larger valves. Stage 1 is the stock valves like AI.
What would I do? Well since I had the same dilemma back in 2013 when I bought my heads, I did TEA Stage 2. And would do them again, everyday of the week. They've made 520rwhp on a 346 with a 234 duration cam. And over 550 on a 408 with a pretty mild cam... think 239 duration. But more importantly, they are fast as hell at the track. The flow numbers don't mean jack. They make real power and run fast. Flycut your pistons and run as much compression as you can. Aim for 8.7:1 DCR.
Btw, the valve job they do is the same ones TEA cuts into their TFS heads. And that's where most of the power is.
One other thing to note, the 226-229cc port runner size of the TEA is about equivalent to the AI heads.
See this post for more information on it: https://ls1tech.com/forums/generatio...l#post19592368
The TEA Stage 2 heads are the ones with the larger valves. Stage 1 is the stock valves like AI.
What would I do? Well since I had the same dilemma back in 2013 when I bought my heads, I did TEA Stage 2. And would do them again, everyday of the week. They've made 520rwhp on a 346 with a 234 duration cam. And over 550 on a 408 with a pretty mild cam... think 239 duration. But more importantly, they are fast as hell at the track. The flow numbers don't mean jack. They make real power and run fast. Flycut your pistons and run as much compression as you can. Aim for 8.7:1 DCR.
Btw, the valve job they do is the same ones TEA cuts into their TFS heads. And that's where most of the power is.
One other thing to note, the 226-229cc port runner size of the TEA is about equivalent to the AI heads.
04-24-2017, 12:51 AM
#20
Yep.
My huge *** build thread has pictures of me flycutting the pistons. But my cam was a 234 on a 108 ICL. So it was going to be tight even with stock heads. Milling down, running a larger valve, and .040" cometics just made it worse.
Of course, now with the 227 cam on a 110 ICL... my DCR went from 8.5:1 to 8.7:1. And I've weakened my pistons for when I boost it. Yay! But I didn't even check when I installed this cam. I knew I had miles of space.
My huge *** build thread has pictures of me flycutting the pistons. But my cam was a 234 on a 108 ICL. So it was going to be tight even with stock heads. Milling down, running a larger valve, and .040" cometics just made it worse.
Of course, now with the 227 cam on a 110 ICL... my DCR went from 8.5:1 to 8.7:1. And I've weakened my pistons for when I boost it. Yay! But I didn't even check when I installed this cam. I knew I had miles of space.