Heads for my XER; 243s or raise the cr more?
06-04-2006, 09:59 PM
#1
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Heads for my XER; 243s or raise the cr more? Okay, I searched and read, and read what I searched, but still not sure.
I have an LS1 GTO M6 with boltons, no cats, Formato tune and a swap to 3.91s (3.46 stock). 340 rwhp with above mods.
I recently picked up a Comp XER with 234/240, .598/.608 lift. Having a set of dual spring ported and polished with ceramic coating heads built by Bob @ Precision motorsports in FL.
My plan was to go 243 and pick up a little CR with the smaller chambers. Bob mills 'em just enough(like .005) to smooth them out.
So, I should be like 10.6 instead of 10.1 right? Ok.
Should I consider 4.8 or 5.3 heads to use instead of 243s for a higher CR with this cam?
I want to end up about 11:1 but don't think further milling would be prudent, and don't have experience with the smaller heads. I will probably do a small dryshot once I stick some 42# injectors down the road, or at least want to be able to, and still run pump 93.
Your thoughts please.
Bill
I have an LS1 GTO M6 with boltons, no cats, Formato tune and a swap to 3.91s (3.46 stock). 340 rwhp with above mods.
I recently picked up a Comp XER with 234/240, .598/.608 lift. Having a set of dual spring ported and polished with ceramic coating heads built by Bob @ Precision motorsports in FL.
My plan was to go 243 and pick up a little CR with the smaller chambers. Bob mills 'em just enough(like .005) to smooth them out.
So, I should be like 10.6 instead of 10.1 right? Ok.
Should I consider 4.8 or 5.3 heads to use instead of 243s for a higher CR with this cam?
I want to end up about 11:1 but don't think further milling would be prudent, and don't have experience with the smaller heads. I will probably do a small dryshot once I stick some 42# injectors down the road, or at least want to be able to, and still run pump 93.
Your thoughts please.
Bill
Last edited by Swamp Goat; 06-04-2006 at 11:42 PM.
06-05-2006, 05:42 PM
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Originally Posted by PREDATOR-Z
Prolly will have to flycut with bigger valves and mill.
What is the LSA/ICL?
What is the LSA/ICL?
@.050 intake opens 5btdc, close 49abdc
exh open 52 bbdc, 8 atdc close
Originally Posted by GuitsBoy
I would certainly go with the smaller chambers, you really want much more compression with a cam that bleeds off that much. Youll want to bring the DCR back up.
The thought of flycutting spooked me a bit, but having done DIY on all my mods, including the diff install and irs work, I can probably figure it out.
Just sorta scarey to saw on the pistons. I am not a machinist, nor do I want to blow the damned engine up cause I take too much off, or end up outta balance.
Thats why I was thinking 4.8 or 5.3 with the decent cost on cores and hopefully avoiding the flycutting. If the chamber decrease alone would get me the compression, I would be thrilled.
I'm not broke, but as a single parent on RN salary, I have to consider many things...
Thank you for responses. I want to hear any hints or suggestions ya'll have, as this is my first LSx valvetrain build, although I have done SBC/BBC in past in my F-bods.
06-05-2006, 05:56 PM
#6
Originally Posted by Swamp Goat
The thought of flycutting spooked me a bit, but having done DIY on all my mods, including the diff install and irs work, I can probably figure it out.
Just sorta scarey to saw on the pistons. I am not a machinist, nor do I want to blow the damned engine up cause I take too much off, or end up outta balance.
Just sorta scarey to saw on the pistons. I am not a machinist, nor do I want to blow the damned engine up cause I take too much off, or end up outta balance.
06-05-2006, 09:12 PM
#7
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Originally Posted by GuitsBoy
Nothing to it. Very simple for the DIYer to do well on their first shot.
Sure was nice on the F Bod motor to order the pistons with the valve reliefs cast in.
Well, hopefully I won't have the opportunity to purchase pistons anytime soon!!
Still wondering if the 4.8s would get me where I need to be without cutting anything. Be a lot easier, as I am NOT paying somebody to do this and don't have a set of old ls heads to use as a template, nor do I have the tool to snake into the valve hole. Hmm. Better to plan it out now though.
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06-06-2006, 11:06 AM
#10
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Thanks for the hints guys. I believe a set of 5.3s is in my future, and will clay it, play with degreeing the cam for DCR and see what happens. With a little spray in the future I want smooth pistons with no potential hotspots. I know its all in the tune, but I have a great tuner here in Tampa. Why screw with pistons if I can not screw with piston integrity?
Cam is in my garage....bought it on a good deal and it was close to what I had been considering, TRAK, S, etc.
I am a rev happy guy with gears and an M6, so down low torque was not my primary concern. I thought the long exhaust duration would like N2O down the road.
Cam is in my garage....bought it on a good deal and it was close to what I had been considering, TRAK, S, etc.
I am a rev happy guy with gears and an M6, so down low torque was not my primary concern. I thought the long exhaust duration would like N2O down the road.
06-06-2006, 12:50 PM
#11
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5.3/4.8 ported will have at least 2.02 valves and you will have to flycut.
5.3L unported with stock valves are worthless.
My advice if you want to stick this cam in, no fly cut is to get a set of LS2/LS6 243 castings with stock valves from TSP/PP or Livernois.
They are 64 cc and you'll benefit fom 3 cc increase in compression.
You can get them with PRC dual springs.
5.3L unported with stock valves are worthless.
My advice if you want to stick this cam in, no fly cut is to get a set of LS2/LS6 243 castings with stock valves from TSP/PP or Livernois.
They are 64 cc and you'll benefit fom 3 cc increase in compression.
You can get them with PRC dual springs.
06-18-2006, 10:16 PM
#12
Sorry for the late chime in, but I would also suggest the 243's with a stage III port and the biggest valves they are willing to put in for you. That is a lot of in/out and with the XER lobes and that much duration you are going to need all the breathing help you can get. I regret not getting them to step up the valve size a bit more on the heads in my goat. I had 241's milled and port/polish with 2.02/1.57, 243's would have been better with even bigger valves.
06-19-2006, 12:15 AM
#13
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Originally Posted by MyGoatBites
Sorry for the late chime in, but I would also suggest the 243's with a stage III port and the biggest valves they are willing to put in for you. That is a lot of in/out and with the XER lobes and that much duration you are going to need all the breathing help you can get. I regret not getting them to step up the valve size a bit more on the heads in my goat. I had 241's milled and port/polish with 2.02/1.57, 243's would have been better with even bigger valves.
Then I saw his mad hi comp4.8s and read all the posts here. Been reading a lot on cam/head and flow dynamics. Whew....and I thought I was gonna do a swap to a lumpy cam easily.
Gonna clay it with built 5.3s, and have a set of 243s in reserve if it gets too close to the piston. Guy I know has a pro degree set up for LS1 from COMP, so might as well do it right. Proven LSx head shop is just 20 minutes from my house.
Thanks again to all who chimed in with advice.
Bill