Will 243 heads clear a big cam?
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Teching In
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Will 243 heads clear a big cam? I found a set of 243 heads that are ported and polished and already have brand new Comp 921 springs for a good deal and I want to try and use them to higher my CP on my 2004 lq9. The springs are rated for up to .650. The cam specs I’m looking to run are .600/.600 lift 242/242 duration and 108 lsa. Does this cam sound right to you guys as far as clearances. Can I use the springs which are rated for .650 on a .600 lift cam? Stop me and steer me in the right direction if I’m doing something wrong I’m 19 and building my first motor! Block and crank are getting honed and polished right now plan on going with a set of forged pistons.
Last edited by Trans-AmGuy; Jun 19, 2020 at 09:33 AM.
welcome to the hobby. A few things:
1. The heads will clear the cam just fine. It's not like DOHC where the cam is in the heads.
2. Yes, you can run springs that are good for .650 lift with only .600 lift. Jsut don't go the other way around, lol.
3. Your main issue is going to be valve to piston clearance. With a cam that large and that tight a LSA, the valves are going to hit the pistons in a LQ4. Unless you are ordering custom pistons, you will need to get a flycutting tool and learn how to use it.
My advice to you would be to find a smaller cam. Yes, that cam will be super rowdy, and you'll get nods of approval from all the dudes in your neighborhood with mullets. But if it's your first motor, I don't recommend complicating it with a cam like that. Especially if you want it to start, and drive, and stuff like that.
I would look into some of the milder cam options with intake durations in the 225-230 range tops and LSA in the 112-114 range. Make it easy on yourself.
1. The heads will clear the cam just fine. It's not like DOHC where the cam is in the heads.
2. Yes, you can run springs that are good for .650 lift with only .600 lift. Jsut don't go the other way around, lol.
3. Your main issue is going to be valve to piston clearance. With a cam that large and that tight a LSA, the valves are going to hit the pistons in a LQ4. Unless you are ordering custom pistons, you will need to get a flycutting tool and learn how to use it.
My advice to you would be to find a smaller cam. Yes, that cam will be super rowdy, and you'll get nods of approval from all the dudes in your neighborhood with mullets. But if it's your first motor, I don't recommend complicating it with a cam like that. Especially if you want it to start, and drive, and stuff like that.
I would look into some of the milder cam options with intake durations in the 225-230 range tops and LSA in the 112-114 range. Make it easy on yourself.
Thread Starter
Teching In
Joined: Mar 2018
Posts: 9
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welcome to the hobby. A few things:
1. The heads will clear the cam just fine. It's not like DOHC where the cam is in the heads.
2. Yes, you can run springs that are good for .650 lift with only .600 lift. Jsut don't go the other way around, lol.
3. Your main issue is going to be valve to piston clearance. With a cam that large and that tight a LSA, the valves are going to hit the pistons in a LQ4. Unless you are ordering custom pistons, you will need to get a flycutting tool and learn how to use it.
My advice to you would be to find a smaller cam. Yes, that cam will be super rowdy, and you'll get nods of approval from all the dudes in your neighborhood with mullets. But if it's your first motor, I don't recommend complicating it with a cam like that. Especially if you want it to start, and drive, and stuff like that.
I would look into some of the milder cam options with intake durations in the 225-230 range tops and LSA in the 112-114 range. Make it easy on yourself.
1. The heads will clear the cam just fine. It's not like DOHC where the cam is in the heads.
2. Yes, you can run springs that are good for .650 lift with only .600 lift. Jsut don't go the other way around, lol.
3. Your main issue is going to be valve to piston clearance. With a cam that large and that tight a LSA, the valves are going to hit the pistons in a LQ4. Unless you are ordering custom pistons, you will need to get a flycutting tool and learn how to use it.
My advice to you would be to find a smaller cam. Yes, that cam will be super rowdy, and you'll get nods of approval from all the dudes in your neighborhood with mullets. But if it's your first motor, I don't recommend complicating it with a cam like that. Especially if you want it to start, and drive, and stuff like that.
I would look into some of the milder cam options with intake durations in the 225-230 range tops and LSA in the 112-114 range. Make it easy on yourself.
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From: Coast of San Mateo County Between Pacifica & HMB
Darth was trying to be gentle, The 242/242 108 lsa will drive like CRAP with a long runner plastic intake and be VERY hard to tune. Even a Cam Motion LS1 Titan King 236/244 112+3 is a Huge cam and would ideally have 5000 stall and at least 4.10 gears. The Titan 4 227/232 113 would be a kick *** combo with your heads and stall and actually be enjoyable to drive .
Just my .02 & experience.
Rock On
Just my .02 & experience.
Rock On
Last edited by NAVYBLUE210; Jun 19, 2020 at 05:47 PM.
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You really cannot change ptv all that much with head gasket thickness. Maybe a whopping .010. Not enough for that cam.
Changing the heads will not really do much. Some aftermarket heads have raised ports but even then a high 230s cam is going to cause problems.
Ideally you want the hg to set quench. Not ptv. Too much quench - too thick hg -- and you make the motor more prone to detonation.
So I am afraid the only good options are to make sure your pistons have massive reliefs or to alter the cam selection
Changing the heads will not really do much. Some aftermarket heads have raised ports but even then a high 230s cam is going to cause problems.
Ideally you want the hg to set quench. Not ptv. Too much quench - too thick hg -- and you make the motor more prone to detonation.
So I am afraid the only good options are to make sure your pistons have massive reliefs or to alter the cam selection
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Teching In
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The whole motor is getting all new bearings cranks getting polished blocks getting honed. The reason I’m getting new pistons is because the stock lq9 ones had an imperfection on one. I Talked to one of Michigan’s best engine builders/ tuners and he told me ptv clearance on 317s and 243s are the same” which I did not know. I figured 243s has less ccs due to being a shorter chamber, not a smaller bore” and I shouldn’t have an issue running a big cam. Also called Texas speed and he said the same thing. Now I’m going with their tsunami v2 cam it’s got 111 lsa which I have now learned lsa isn’t the only thing making the cam lumpy.
Thread Starter
Teching In
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Thread Starter
Teching In
Joined: Mar 2018
Posts: 9
Likes: 0
Domed pistons would low my ptv even less! Blocks getting honed and new bearing put in. And I had one iffy piston.
Originally Posted by Trans-AmGuy
Domed pistons would low my ptv even less! Blocks getting honed and new bearing put in. And I had one iffy piston.
I am ordering some forged pistons. Do you think I could get away with adding a thicker gasket? I’ve spent some time researching the cam specs I want and I do want to go kindof crazy. Already have it geared built tranny with a 3800 stall. I don’t want to throw a mild cam in it. Should I maybe scratch the 243 heads idea? Only reason I’m trying to make it work is because he wants 900$ for them. My dad did the same work on a less desirable head “317s” and he has 2500 into them from our machine shop .
I found a set of 243 heads that are ported and polished and already have brand new Comp 921 springs for a good deal and I want to try and use them to higher my CP on my 2004 lq9. The springs are rated for up to .650. The cam specs I’m looking to run are .600/.600 lift 242/242 duration and 108 lsa. Does this cam sound right to you guys as far as clearances. Can I use the springs which are rated for .650 on a .600 lift cam? Stop me and steer me in the right direction if I’m doing something wrong I’m 19 and building my first motor! Block and crank are getting honed and polished right now plan on going with a set of forged pistons.
welcome to the hobby. A few things:
1. The heads will clear the cam just fine. It's not like DOHC where the cam is in the heads.
2. Yes, you can run springs that are good for .650 lift with only .600 lift. Jsut don't go the other way around, lol.
3. Your main issue is going to be valve to piston clearance. With a cam that large and that tight a LSA, the valves are going to hit the pistons in a LQ4. Unless you are ordering custom pistons, you will need to get a flycutting tool and learn how to use it.
My advice to you would be to find a smaller cam. Yes, that cam will be super rowdy, and you'll get nods of approval from all the dudes in your neighborhood with mullets. But if it's your first motor, I don't recommend complicating it with a cam like that. Especially if you want it to start, and drive, and stuff like that.
I would look into some of the milder cam options with intake durations in the 225-230 range tops and LSA in the 112-114 range. Make it easy on yourself.
1. The heads will clear the cam just fine. It's not like DOHC where the cam is in the heads.
2. Yes, you can run springs that are good for .650 lift with only .600 lift. Jsut don't go the other way around, lol.
3. Your main issue is going to be valve to piston clearance. With a cam that large and that tight a LSA, the valves are going to hit the pistons in a LQ4. Unless you are ordering custom pistons, you will need to get a flycutting tool and learn how to use it.
My advice to you would be to find a smaller cam. Yes, that cam will be super rowdy, and you'll get nods of approval from all the dudes in your neighborhood with mullets. But if it's your first motor, I don't recommend complicating it with a cam like that. Especially if you want it to start, and drive, and stuff like that.
I would look into some of the milder cam options with intake durations in the 225-230 range tops and LSA in the 112-114 range. Make it easy on yourself.
Question for you Darth, I'm doing almost the same build as OP, but mine is a sbe lq4 with 243s, ls6 intake, and the TSP 233/239 cam with a 111 lsa with a 4l80e and either a 3400 or 3600 stall. What valve springs would you say go with? And would this in your opinion be a good combo? It will see a little street, a little strip.