Open chambers or not?
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Open chambers or not? With the L92 heads designed for the 4.80 size bore is it recommended to open up the chambers to 4.125 when using for the 427? Was told that they are so close it is not necassary. That did not make any sense to me and thought I would ask you guysfor your opinions. Thanks for the help.
If you're going to run a cam with 42 degrees of overlap, you're going to need all the compression you can get. Opening up the chamber even more might hurt you more than help. FWIW, the incremental flow gains will most likely be offset by the loss of compression. I hope your pistons are flat-tops because if they're not, you may not hit your torque goals since your compression is going to be lower than optimal.
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2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
FormerVendor
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From: Houston, Tx.
Airflow wise the chambers should be as unshrouded as the valves want but as Patrick said you will lose compression when you do this. If you had too much compression this would be great and if you needed more compression you might have to mill the heads or run a small dome if you made the chambers much larger. It just depend on your combo. I am doing some of my own L92 Flat Tops and they have pretty high compression but we have domes as well for people that are going to much higher compression numbers.
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Originally Posted by Patrick G
If you're going to run a cam with 42 degrees of overlap, you're going to need all the compression you can get. Opening up the chamber even more might hurt you more than help. FWIW, the incremental flow gains will most likely be offset by the loss of compression. I hope your pistons are flat-tops because if they're not, you may not hit your torque goals since your compression is going to be lower than optimal.
3cc dished pistons but the piston only comes out of the hole .005 on the Diamond L92 pistons.
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Erik, what are you guys doing for L92 ported heads righ now? I am in need of a set. TSP is having a hard time with the digitalizing of the program and I am getting tired of waiting for heads. The shortblock has been done for some time now and I am ready to get this thing back together. TSP has already told me they would not be offended if I got heads elsewhere.
FormerVendor
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From: Houston, Tx.
Dont bet on it till you mock it up. Decks never come out right on these LSx engines. It might be close or it might not but don't make any head gaskets choices if you are cutting it close without knowing the real deck. It's not the TSP or Diamond is wrong it's just that the deck tolerances are not that great on the LSx family.
I've already had several instances of the LS1Tech Quench junkies that have pistons hitting the heads more often than you might think. I had a customer in the Dallas area that had the pistons .030 out of the hole on his new iron block 408 and that's maybe the tenth time so far that I have seen that so just check and be safe. Most of the L92s so far aren't totally Fubar but they aren't right on either.
I've already had several instances of the LS1Tech Quench junkies that have pistons hitting the heads more often than you might think. I had a customer in the Dallas area that had the pistons .030 out of the hole on his new iron block 408 and that's maybe the tenth time so far that I have seen that so just check and be safe. Most of the L92s so far aren't totally Fubar but they aren't right on either.
FormerVendor
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From: Houston, Tx.
Originally Posted by 03 BUSA
Erik, what are you guys doing for L92 ported heads righ now? I am in need of a set. TSP is having a hard time with the digitalizing of the program and I am getting tired of waiting for heads. The shortblock has been done for some time now and I am ready to get this thing back together. TSP has already told me they would not be offended if I got heads elsewhere.
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From: Kannapolis, NC
Originally Posted by racer7088
I am just now seeing the heads I ordered and the ones sent to me so I don't know but I don't think you would need much porting to tell you the truth. These are certainly plenty large and I think can be made much better with minimal work.
TSP's first cnc job came out around 340 flow on the intake and they are not going to release until they hit their 360 from the first hand ported set they did. I am trying to find a ported bare set and just use their PRC valve train stuff and get this thing back together. My goals are mid 500 hp and tq NA. Cam is a 257/266 622/646 110 lsa 110 icl
Originally Posted by 03 BUSA
3cc dished pistons but the piston only comes out of the hole .005 on the Diamond L92 pistons.
with less than 50k miles, and as low as .002
Originally Posted by 03 BUSA
TSP's first cnc job came out around 340 flow on the intake and they are not going to release until they hit their 360 from the first hand ported set they did. I am trying to find a ported bare set and just use their PRC valve train stuff and get this thing back together. My goals are mid 500 hp and tq NA. Cam is a 257/266 622/646 110 lsa 110 icl
on what lobes? solid roller?
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From: Kannapolis, NC
Originally Posted by NemeSS
is that a custom ground cam?
on what lobes? solid roller?
on what lobes? solid roller?
Custom grind, hydraulic setup. I believe this cam has been ground before on a 112 but never a 110.
Originally Posted by 03 BUSA
My goals are mid 500 hp and tq NA. Cam is a 257/266 622/646 110 lsa 110 icl
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2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
Livernios has CNC'd L92 heads that flow 360 on the int and 245 w/o a pipe & 264 on a 1 3/4" pipe. However I only see them sold as assembled for $2000.
Last edited by 1997bird; Jan 21, 2007 at 02:35 PM.
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Originally Posted by Patrick G
You're going to need some very high static compression to have dynamic compression in the 8s. Unless your hydraulic cam has super fast ramps, you're going to need over 12.0:1 compression to get your DCR into the 8s. What is the duration at .006" of your cam?
Patrick, these are the numbers I have been given:
18.6 BTDC and 58.6 ABDC on the intake
63 BBDC and 23 ATDC on the exhaust
that gives me a DCR of around 8.4.1 and SCR of 11.5.1
this is with pistons .005 out of hole and .056 compressed GM LS7 head gaskets. Let me know what you are coming up with. Thanks.
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Originally Posted by 1997bird
Livernios has CNC'd L92 heads that flow 360 on the int and 245 w/o a pipe & 264 on a 1 3/4" pipe. However I only see them sold as assembled for $2000.
I saw those, I will be calling them tomorrow to see if they will just sell the bare ported castings. TSP quoted me $1499, I do not see where they justify 500 more with the same flow numbers and almost identical valvetrain.