are 2.08 valves to large for a stock bore ls1?
07-24-2015, 10:34 AM
#41
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Ideal valve sizes Bump for an old but good thread.
My question is what would the ideal valve sizes be for a stock 3.9" bore? If you had or wanted to change either of them which one would net better gains? Would it be better to keep the stock exhaust size and go bigger on the intake or vice versa?
I'm going to be sending my 243's off to TEA or AI soon and want to get the best gains possible. I've contemplated going with turned 2.055/ 1.6 LS3 valves to gain size but also keep the weight down. Heck I've even thought about Ti for the intakes to go that much further.
Thoughts?
My question is what would the ideal valve sizes be for a stock 3.9" bore? If you had or wanted to change either of them which one would net better gains? Would it be better to keep the stock exhaust size and go bigger on the intake or vice versa?
I'm going to be sending my 243's off to TEA or AI soon and want to get the best gains possible. I've contemplated going with turned 2.055/ 1.6 LS3 valves to gain size but also keep the weight down. Heck I've even thought about Ti for the intakes to go that much further.
Thoughts?
07-24-2015, 10:50 AM
#42
TEA has two programs for the 243s... stock valves and the 2.04/1.575 combo. Ai has the stock valve combo and a 2.055/1.55 stock valve combo. I run the Stage 2 on my TEA but have turned-down LS3 valves to help with weight on the 2.04" valve.
The bigger valves lose some velocity because the coefficient of discharge drops (given the same port and port cross-sectional area) and the formula for CeD is CFM/(Valve size*Pi*Lift). Now, bigger valves can work better than smaller ones if the port is optimized for it. For example, a 260cc port with a 2.165" valve that flows 300cfm @ .400" would be better than a 226cc port with a 2.00" valve that only flows 260. But when comparing the same port with different sized valves such as what TEA and AI do; aim for balance.
However, where you may gain little in mid-lift flow, you gain significantly in the upper lift areas above .550" with the bigger valve. If you go with a hydraulic cam with .600" lift, a majority of the time is spent in the .200-.400 range and the better coefficient of discharge from the smaller valve makes better avg power.
But, if you run high-lift hydraulics or go solid and do .650"+ lifts, then you start to reap the benefits of the larger valve. And the larger valve options, on the right motor, can make another 10-20HP.
I plan to run the TEA Stage 3 heads which go to a 2.08/1.60. And I'll run the solid stem valves. They are heavier, but in a solid roller, I'd rather have the strength. The control comes from the solid lifter setup. On a hydraulic setup, weight is the enemy. Go as light as you can.
The bigger valves lose some velocity because the coefficient of discharge drops (given the same port and port cross-sectional area) and the formula for CeD is CFM/(Valve size*Pi*Lift). Now, bigger valves can work better than smaller ones if the port is optimized for it. For example, a 260cc port with a 2.165" valve that flows 300cfm @ .400" would be better than a 226cc port with a 2.00" valve that only flows 260. But when comparing the same port with different sized valves such as what TEA and AI do; aim for balance.
However, where you may gain little in mid-lift flow, you gain significantly in the upper lift areas above .550" with the bigger valve. If you go with a hydraulic cam with .600" lift, a majority of the time is spent in the .200-.400 range and the better coefficient of discharge from the smaller valve makes better avg power.
But, if you run high-lift hydraulics or go solid and do .650"+ lifts, then you start to reap the benefits of the larger valve. And the larger valve options, on the right motor, can make another 10-20HP.
I plan to run the TEA Stage 3 heads which go to a 2.08/1.60. And I'll run the solid stem valves. They are heavier, but in a solid roller, I'd rather have the strength. The control comes from the solid lifter setup. On a hydraulic setup, weight is the enemy. Go as light as you can.
Last edited by JakeFusion; 07-24-2015 at 10:57 AM.
07-24-2015, 11:15 PM
#43
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TEA has two programs for the 243s... stock valves and the 2.04/1.575 combo. Ai has the stock valve combo and a 2.055/1.55 stock valve combo. I run the Stage 2 on my TEA but have turned-down LS3 valves to help with weight on the 2.04" valve.
I didn't know that Ai had another level with bigger valves? I'd like to see and compare that one to the TEA Stage 2's. I've looked at the flow sheets for a few of the heads that each offer and they are very close in most lifts. I've also inquired about turned LS3 valves at TEA, might even consider Ti intakes to further lighten the valves depending on price.
The bigger valves lose some velocity because the coefficient of discharge drops (given the same port and port cross-sectional area) and the formula for CeD is CFM/(Valve size*Pi*Lift). Now, bigger valves can work better than smaller ones if the port is optimized for it. For example, a 260cc port with a 2.165" valve that flows 300cfm @ .400" would be better than a 226cc port with a 2.00" valve that only flows 260. But when comparing the same port with different sized valves such as what TEA and AI do; aim for balance.
As for balance, I would hope that both companies have "optimized" the program they run on the CNC for the upgraded valves. Maybe not?
However, where you may gain little in mid-lift flow, you gain significantly in the upper lift areas above .550" with the bigger valve. If you go with a hydraulic cam with .600" lift, a majority of the time is spent in the .200-.400 range and the better coefficient of discharge from the smaller valve makes better avg power.
But, if you run high-lift hydraulics or go solid and do .650"+ lifts, then you start to reap the benefits of the larger valve. And the larger valve options, on the right motor, can make another 10-20HP.
I'd like to stay with a hydraulic package with short travel, slow leak, linked lifters with more than .600 lift. Cam specs and lobe profile TBD. Any suggestions?
I plan to run the TEA Stage 3 heads which go to a 2.08/1.60. And I'll run the solid stem valves. They are heavier, but in a solid roller, I'd rather have the strength. The control comes from the solid lifter setup. On a hydraulic setup, weight is the enemy. Go as light as you can.
I didn't know that Ai had another level with bigger valves? I'd like to see and compare that one to the TEA Stage 2's. I've looked at the flow sheets for a few of the heads that each offer and they are very close in most lifts. I've also inquired about turned LS3 valves at TEA, might even consider Ti intakes to further lighten the valves depending on price.
The bigger valves lose some velocity because the coefficient of discharge drops (given the same port and port cross-sectional area) and the formula for CeD is CFM/(Valve size*Pi*Lift). Now, bigger valves can work better than smaller ones if the port is optimized for it. For example, a 260cc port with a 2.165" valve that flows 300cfm @ .400" would be better than a 226cc port with a 2.00" valve that only flows 260. But when comparing the same port with different sized valves such as what TEA and AI do; aim for balance.
As for balance, I would hope that both companies have "optimized" the program they run on the CNC for the upgraded valves. Maybe not?
However, where you may gain little in mid-lift flow, you gain significantly in the upper lift areas above .550" with the bigger valve. If you go with a hydraulic cam with .600" lift, a majority of the time is spent in the .200-.400 range and the better coefficient of discharge from the smaller valve makes better avg power.
But, if you run high-lift hydraulics or go solid and do .650"+ lifts, then you start to reap the benefits of the larger valve. And the larger valve options, on the right motor, can make another 10-20HP.
I'd like to stay with a hydraulic package with short travel, slow leak, linked lifters with more than .600 lift. Cam specs and lobe profile TBD. Any suggestions?
I plan to run the TEA Stage 3 heads which go to a 2.08/1.60. And I'll run the solid stem valves. They are heavier, but in a solid roller, I'd rather have the strength. The control comes from the solid lifter setup. On a hydraulic setup, weight is the enemy. Go as light as you can.
07-24-2015, 11:20 PM
#44
Stage 3 is an upgrade to Stage 2 heads and is LS6 based. From what I understand, they use the Stage 2 Port Program and they add the Stage 3 Valve Job and hand blend into the port. So it remains around 229cc with the larger valves and doesn't pick up a ton of flow until the upper lift areas. It's going on a 416.
I'll be running PAC 1207X springs (155/436; .700" lift) with the LLSR. I'll shim them up probably for 165 on the seat. Would work well with the Cam Motion lobes.
I'll be running PAC 1207X springs (155/436; .700" lift) with the LLSR. I'll shim them up probably for 165 on the seat. Would work well with the Cam Motion lobes.
07-25-2015, 03:28 PM
#45
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I'm no cam expert but as a point of reference, I have CNC 799 heads with 2.055/1.60 on a stock LS1. It did hurt the lower end performance and OK at anything above top end, probably the wrong choice for my car.
Martin spec'd me a cam to offset the shrouding and it made a world of difference, drivability, performance from low to high power band and no clearance issues. Car drives amazing. It is a baby cam and specs are probably why it is not an issue for me.
If I could have done it over again, I would have gone with closer to stock size on the exhaust side from what I heard.. I would say 2.08 is extreme for stock & 2:055 may be OK with proper cam size.
Martin spec'd me a cam to offset the shrouding and it made a world of difference, drivability, performance from low to high power band and no clearance issues. Car drives amazing. It is a baby cam and specs are probably why it is not an issue for me.
If I could have done it over again, I would have gone with closer to stock size on the exhaust side from what I heard.. I would say 2.08 is extreme for stock & 2:055 may be OK with proper cam size.
Last edited by BBATCAR; 07-25-2015 at 03:40 PM.
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01-17-2022, 08:05 PM
#50
Maybe it was the same glitch as it happened to me twice in last 3 days. I hit reply in thread and my post ends up in some old thread where my answer is completely irrelevant.
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