LQ4 6.0L Build...what cam to run w/ 243 heads
08-10-2020, 06:39 PM
#21
Teching In
Oh that... skewzzz me.
PTV problems have to do with duration more than anything else. THINK: max lift occurs when the piston is roughly halfway down the bore. The ONLY time during the engine cycle that it's an issue, is when the piston is near TDC. Cams that hold the exh open REAL late, or open the int REAL early, can cause problems, because then you have a valve significantly open and a piston near the top. Otherwise, not a problem.
Yes that TSP "Stage 3 truck" is pretty much exactly what I had in mind.
Yes. The high-lift will outrun the low-lift, every time. Especially if the heads have been opened up to take advantage of it, such that the valve opening is The Bottleneck, and the extra lift overcomes it. Only thing is, it requires ALOT better valve springs, and ALOT more attention to detail in setting up the valve train. That last .050" of lift is a killer if you're not careful.
PTV problems have to do with duration more than anything else. THINK: max lift occurs when the piston is roughly halfway down the bore. The ONLY time during the engine cycle that it's an issue, is when the piston is near TDC. Cams that hold the exh open REAL late, or open the int REAL early, can cause problems, because then you have a valve significantly open and a piston near the top. Otherwise, not a problem.
Yes that TSP "Stage 3 truck" is pretty much exactly what I had in mind.
Yes. The high-lift will outrun the low-lift, every time. Especially if the heads have been opened up to take advantage of it, such that the valve opening is The Bottleneck, and the extra lift overcomes it. Only thing is, it requires ALOT better valve springs, and ALOT more attention to detail in setting up the valve train. That last .050" of lift is a killer if you're not careful.
Oh ok thats some good information that doesn't sound to confusing compared to other stuff I've read. So would it be safe to say that the btr cam 227/234 I refered to at first is more prone to give me ptv issues. How do you think a tsp stage 3 high lift would pair up with some milled 243s (62cc) maybe a light port job?
Speaking of springs some have been saying that I should go with beehive springs for long term due to the double springs not being optimal for long term use and should be change at I think was 30k miles.
What kind of attention to detail are you referring to?
08-10-2020, 07:18 PM
#22
What scares you!?!
cam 227/234 ... is more prone to give me ptv issues
Beehive springs are STOCK on these motors. Yes absolutely you can use them. Double springs are considered an upgrade, not least because, if one breaks, there's one still left to keep the valve from just falling into the cylinder. Not saying you MUST use double springs, you MUST use beehives, or anything like that; only, it's not a matter of, look it up in the catalog, buy it, slap it on, end of story. There's more to it than that.
By "attention to detail" I'm referring to getting the push rod length (lifter preload) right, spring installed height right, shimming or grinding the rocker stands to get the rocker geometry right, and any number of other things RIGHT, ... did I use the word "RIGHT" enough times?
You can't just buy abuncha romantic-sounding stuff that "all the fast cars" have, slap it onto your motor, and expect automatic success. REALLY BAD THINGS can happen with an improperly set up valve train.If you don't know how to do that, or have no experience at it, or nobody to teach or show you, or no measuring tools to do it with, just go with the low-lift version of that kind of cam, and some GOOD QUALITY beehive (stock configuration) springs such as PAC 1218 or 1219. Ask whoever you get the cam from what springs they recommend as a minimum, then what they recommend as an upgrade, and go with the upgrade. You'll lose a little compared to the high lift version, but you'll have less chance of a severely unwanted outcome. And probably still have ALOTTA FUN driving it.
08-10-2020, 07:31 PM
#23
Teching In
Very few things. What doesn't kill me makes me stronger. I've done ALOT of things and had ALOT of things happen to me. And I'm still alive. So you do the math.
Yes. But "more prone" is relative. Kinda like, how likely is it that you will be (a) hit by lightning, (b) killed in a shark attack, or (c) die in a plane wreck? Which one should you protect yourself against? (speaking strictly as one who has been hit by lightning and been in a plane wreck, but am still alive)
Beehive springs are STOCK on these motors. Yes absolutely you can use them. Double springs are considered an upgrade, not least because, if one breaks, there's one still left to keep the valve from just falling into the cylinder. Not saying you MUST use double springs, you MUST use beehives, or anything like that; only, it's not a matter of, look it up in the catalog, buy it, slap it on, end of story. There's more to it than that.
By "attention to detail" I'm referring to getting the push rod length (lifter preload) right, spring installed height right, shimming or grinding the rocker stands to get the rocker geometry right, and any number of other things RIGHT, ... did I use the word "RIGHT" enough times? You can't just buy abuncha romantic-sounding stuff that "all the fast cars" have, slap it onto your motor, and expect automatic success. REALLY BAD THINGS can happen with an improperly set up valve train.
If you don't know how to do that, or have no experience at it, or nobody to teach or show you, or no measuring tools to do it with, just go with the low-lift version of that kind of cam, and some GOOD QUALITY beehive (stock configuration) springs such as PAC 1218 or 1219. Ask whoever you get the cam from what springs they recommend as a minimum, then what they recommend as an upgrade, and go with the upgrade. You'll lose a little compared to the high lift version, but you'll have less chance of a severely unwanted outcome. And probably still have ALOTTA FUN driving it.
Yes. But "more prone" is relative. Kinda like, how likely is it that you will be (a) hit by lightning, (b) killed in a shark attack, or (c) die in a plane wreck? Which one should you protect yourself against? (speaking strictly as one who has been hit by lightning and been in a plane wreck, but am still alive)
Beehive springs are STOCK on these motors. Yes absolutely you can use them. Double springs are considered an upgrade, not least because, if one breaks, there's one still left to keep the valve from just falling into the cylinder. Not saying you MUST use double springs, you MUST use beehives, or anything like that; only, it's not a matter of, look it up in the catalog, buy it, slap it on, end of story. There's more to it than that.
By "attention to detail" I'm referring to getting the push rod length (lifter preload) right, spring installed height right, shimming or grinding the rocker stands to get the rocker geometry right, and any number of other things RIGHT, ... did I use the word "RIGHT" enough times?
You can't just buy abuncha romantic-sounding stuff that "all the fast cars" have, slap it onto your motor, and expect automatic success. REALLY BAD THINGS can happen with an improperly set up valve train.If you don't know how to do that, or have no experience at it, or nobody to teach or show you, or no measuring tools to do it with, just go with the low-lift version of that kind of cam, and some GOOD QUALITY beehive (stock configuration) springs such as PAC 1218 or 1219. Ask whoever you get the cam from what springs they recommend as a minimum, then what they recommend as an upgrade, and go with the upgrade. You'll lose a little compared to the high lift version, but you'll have less chance of a severely unwanted outcome. And probably still have ALOTTA FUN driving it.
08-11-2020, 08:45 PM
#25
TECH Senior Member
08-12-2020, 06:18 AM
#26
But to the question that was being asked, I ran a Lq4 with 243 heads and MS3 cam, NO clearance issues.
Also ran the summit 8702 cam with .010 milled 243 heads with flat top pistons, and NO clearance issues.
08-12-2020, 06:38 AM
#27
you WILL die .... one day
True dat.I can only hope that when the time comes, it only takes one day. (or less, ideally; as little time as possible)
But yes, it usually takes ALOT of cam, with ALOT of duration, to create PTV problems. It would be extremely unusual to see that with any cam having much less than 240 degrees @ .050". Not "impossible"; just, "unusual". Lift is not much of a factor; it's duration, specifically having valves open when the piston is near TDC.
