243s vs. 5.3 Heads
04-14-2009, 09:38 PM
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243s vs. 5.3 Heads Im trying to figure out which heads would be the best bang for the buck...
Im planning on rebuilding some heads for my stock ls1. I dont know if these heads are going to be the ones I keep after some future plans. Im going to be running the stock 99 ls1 cam and stock rocker arm ratio, and stock bottom end. My engine has higher mileage and im starting to think maybe my factory springs are not as firm as they use to be under higher rpm.
But anyways just to freshen up my top end, Im wondering which head you guys prefer...
What is the largest diameter valve that can go in the stock 5.7 bore with a stock 5.7 cam. or a cam with about .570 lift someday. Also any specs on each head be great, stock valve size, chambers, ports etc...
Im going to be doing the works to whichever set i pick. Porting, new valves, 3angle cuts, Surface milled for more compression, new springs... Wouldnt mind increasing the valve diameter if possible in 5.3 heads if its possible to grind into the factory seats. If thats a bad idea let me know too lol....
In conclusion, is worth spending around $600 on nice used 243s and do mild builds, or just get 5.3 heads cheap and build them to what I want. *Note* My dad is a pro at rebuilding heads for small blocks and has the proper tools so I can save money from a machinist. Were both interested what we can turn out of some lsx heads since weve never worked on them.
Im planning on rebuilding some heads for my stock ls1. I dont know if these heads are going to be the ones I keep after some future plans. Im going to be running the stock 99 ls1 cam and stock rocker arm ratio, and stock bottom end. My engine has higher mileage and im starting to think maybe my factory springs are not as firm as they use to be under higher rpm.
But anyways just to freshen up my top end, Im wondering which head you guys prefer...
What is the largest diameter valve that can go in the stock 5.7 bore with a stock 5.7 cam. or a cam with about .570 lift someday. Also any specs on each head be great, stock valve size, chambers, ports etc...
Im going to be doing the works to whichever set i pick. Porting, new valves, 3angle cuts, Surface milled for more compression, new springs... Wouldnt mind increasing the valve diameter if possible in 5.3 heads if its possible to grind into the factory seats. If thats a bad idea let me know too lol....
In conclusion, is worth spending around $600 on nice used 243s and do mild builds, or just get 5.3 heads cheap and build them to what I want. *Note* My dad is a pro at rebuilding heads for small blocks and has the proper tools so I can save money from a machinist. Were both interested what we can turn out of some lsx heads since weve never worked on them.
04-14-2009, 10:23 PM
#2
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Im trying to figure out which heads would be the best bang for the buck...
Im planning on rebuilding some heads for my stock ls1. I dont know if these heads are going to be the ones I keep after some future plans. Im going to be running the stock 99 ls1 cam and stock rocker arm ratio, and stock bottom end. My engine has higher mileage and im starting to think maybe my factory springs are not as firm as they use to be under higher rpm.
But anyways just to freshen up my top end, Im wondering which head you guys prefer...
What is the largest diameter valve that can go in the stock 5.7 bore with a stock 5.7 cam. or a cam with about .570 lift someday. Also any specs on each head be great, stock valve size, chambers, ports etc...
Im going to be doing the works to whichever set i pick. Porting, new valves, 3angle cuts, Surface milled for more compression, new springs... Wouldnt mind increasing the valve diameter if possible in 5.3 heads if its possible to grind into the factory seats. If thats a bad idea let me know too lol....
In conclusion, is worth spending around $600 on nice used 243s and do mild builds, or just get 5.3 heads cheap and build them to what I want. *Note* My dad is a pro at rebuilding heads for small blocks and has the proper tools so I can save money from a machinist. Were both interested what we can turn out of some lsx heads since weve never worked on them.
Im planning on rebuilding some heads for my stock ls1. I dont know if these heads are going to be the ones I keep after some future plans. Im going to be running the stock 99 ls1 cam and stock rocker arm ratio, and stock bottom end. My engine has higher mileage and im starting to think maybe my factory springs are not as firm as they use to be under higher rpm.
But anyways just to freshen up my top end, Im wondering which head you guys prefer...
What is the largest diameter valve that can go in the stock 5.7 bore with a stock 5.7 cam. or a cam with about .570 lift someday. Also any specs on each head be great, stock valve size, chambers, ports etc...
Im going to be doing the works to whichever set i pick. Porting, new valves, 3angle cuts, Surface milled for more compression, new springs... Wouldnt mind increasing the valve diameter if possible in 5.3 heads if its possible to grind into the factory seats. If thats a bad idea let me know too lol....
In conclusion, is worth spending around $600 on nice used 243s and do mild builds, or just get 5.3 heads cheap and build them to what I want. *Note* My dad is a pro at rebuilding heads for small blocks and has the proper tools so I can save money from a machinist. Were both interested what we can turn out of some lsx heads since weve never worked on them.
Why would you want to put in the largest intake (I assume) valve that will physically fit? If your answer is "big valves flow more", you don't really understand as much as you think you do.
As for most bang for the buck, 243s with stock size valves, the correct valve job (which very few people do), an some flat milling will walk all over just about anything you and your dad (no offense, my progeny is an engine guy) can do to 5.3 heads.
If you are up to it, do your best on a set of 5.3s and dyno them on your engine. If you can score some unmolested 243s, have one of about 2 or 3 folks (who must remain nameless here) valve job them, mill them and put on good springs of their choice and run these back to back with your Stage 3 or 4, etc. 5.3s. You then might want to sell the 5.3s and run the 243 Stage .1 heads.
Don't think traditional SBC when working on LS heads. No offense, but way too many SBC guys don't get SBCs right either.
FWIW, the guys who can do the correct valve job are not going to tell you what to do. Conversely, those that tell you online what valve job to run most likely will not be too close to what is good. Funny how that works, isn't it?
Anyhow, good luck and have a ball!
Jon
04-15-2009, 04:27 PM
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I was going have them mill them to bump up the compression a bit and to true them up. How much milling can I get away with without running into detonation problems. My tune is set up for 93 octane which is easy to get around here.
PM me or email me about what to look for with valve jobs.
brnagain at maine.rr.com
04-15-2009, 04:47 PM
#4
If you get the 243's milled to 60 cc's and use a .040 gasket it should be around 11.3:1.
n.m. racer - most people use the 5.3's b/c they're plentiful and you get a bump in compression just by bolting them on with no milling b/c of the 61 cc chambers (I think thats right).
Heres a good site for LSX info on motors and heads:
http://chevythunder.com/LS1%20compon...20ID%20Numbers
Use the LS6 (243) heads and you'll be farther ahead of the game down the road.
n.m. racer - most people use the 5.3's b/c they're plentiful and you get a bump in compression just by bolting them on with no milling b/c of the 61 cc chambers (I think thats right).
Heres a good site for LSX info on motors and heads:
http://chevythunder.com/LS1%20compon...20ID%20Numbers
Use the LS6 (243) heads and you'll be farther ahead of the game down the road.
04-15-2009, 04:50 PM
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04-15-2009, 11:16 PM
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Hi n.m. You are probably not going to like what I say, but you did ask.
Why would you want to put in the largest intake (I assume) valve that will physically fit? If your answer is "big valves flow more", you don't really understand as much as you think you do.
As for most bang for the buck, 243s with stock size valves, the correct valve job (which very few people do), an some flat milling will walk all over just about anything you and your dad (no offense, my progeny is an engine guy) can do to 5.3 heads.
If you are up to it, do your best on a set of 5.3s and dyno them on your engine. If you can score some unmolested 243s, have one of about 2 or 3 folks (who must remain nameless here) valve job them, mill them and put on good springs of their choice and run these back to back with your Stage 3 or 4, etc. 5.3s. You then might want to sell the 5.3s and run the 243 Stage .1 heads.
Don't think traditional SBC when working on LS heads. No offense, but way too many SBC guys don't get SBCs right either.
FWIW, the guys who can do the correct valve job are not going to tell you what to do. Conversely, those that tell you online what valve job to run most likely will not be too close to what is good. Funny how that works, isn't it?
Anyhow, good luck and have a ball!
Jon
Why would you want to put in the largest intake (I assume) valve that will physically fit? If your answer is "big valves flow more", you don't really understand as much as you think you do.
As for most bang for the buck, 243s with stock size valves, the correct valve job (which very few people do), an some flat milling will walk all over just about anything you and your dad (no offense, my progeny is an engine guy) can do to 5.3 heads.
If you are up to it, do your best on a set of 5.3s and dyno them on your engine. If you can score some unmolested 243s, have one of about 2 or 3 folks (who must remain nameless here) valve job them, mill them and put on good springs of their choice and run these back to back with your Stage 3 or 4, etc. 5.3s. You then might want to sell the 5.3s and run the 243 Stage .1 heads.
Don't think traditional SBC when working on LS heads. No offense, but way too many SBC guys don't get SBCs right either.
FWIW, the guys who can do the correct valve job are not going to tell you what to do. Conversely, those that tell you online what valve job to run most likely will not be too close to what is good. Funny how that works, isn't it?
Anyhow, good luck and have a ball!
Jon
You definately made the choice seem easier so Ill probably just save up for some well taken care of 243's. I dont mind having someone else do the headwork but I would like to learn the process to building true racing heads. It is funny the guys with the know-how keep the information to themselves but then again thats where they make their money. Im also not trying to build my dad up to be some glorious headwork master either, but he definately knows his stuff for sbc's, big block chevys and fords. Hes been a machinst for over 30 years and I havent even had the chance to talk to him about any help yet... so I dont even know what he'd suggest.
But great job on the replies, all the input really helps.
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04-15-2009, 11:36 PM
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Not to hijack but what about 317 heads compared to the 243. I know that the 317 heads are off the same design but with a larger combustion chamber. So what I would really like to know is that should I keep and mill the 317's or get a set of 243's?
04-16-2009, 12:54 PM
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I would go 243. If you can afford a good valvejob like OldSS said I would go that route, if not run them.
Once you get enough money saved up send the 243s out to have them ported/good VJ (by a reputable head guy).
Now the big question, being on a budget like alot of us here are, and spending $2,000 to port a set of 243 heads properly... you have to decide where to spend your money.
For me I decided to just run the stock 241 heads as I plan on going to a bigger bore engine in the near future. Then i'll spend the big bucks on a nice ported set of Dart 225, but if you plan on running the 3.90 bore for a long time then 243s will work great!
Another option which some have seemed to have some good luck with is to run the DART225 as cast on a 346, then when you upgrade to a larger cube/bigger bore engine have them ported at that point. I'm thinking about doing that if I can find the $$$ and time.
Once you get enough money saved up send the 243s out to have them ported/good VJ (by a reputable head guy).
Now the big question, being on a budget like alot of us here are, and spending $2,000 to port a set of 243 heads properly... you have to decide where to spend your money.
For me I decided to just run the stock 241 heads as I plan on going to a bigger bore engine in the near future. Then i'll spend the big bucks on a nice ported set of Dart 225, but if you plan on running the 3.90 bore for a long time then 243s will work great!
Another option which some have seemed to have some good luck with is to run the DART225 as cast on a 346, then when you upgrade to a larger cube/bigger bore engine have them ported at that point. I'm thinking about doing that if I can find the $$$ and time.
