lq4 power loss
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
scrap 90% of the info in this thread.
Compression on LQ4 and T-Rex is a huge mismatch.
My advice, mill the heads (6.0s), get a smaller cam and you'll make way more power than the combo you are talking about.
Compression on LQ4 and T-Rex is a huge mismatch.
My advice, mill the heads (6.0s), get a smaller cam and you'll make way more power than the combo you are talking about.
Running milled 5.3's would be much better than running milled 6.0 heads. You'd have to mill the 6.0 heads a crazy amount to get the CR worthwhile for a NA application. I never made a suggestion on what cam to use.
Cause they both outflow the 853's. Head flow is a big factor in the power equation. You can use the 853's no problem though. I don't remember the specs of the Trex cam off hand, but I know it is a rather stout cam. I'm more of a fan of a mid-range cam, but that's just me. Do your research, a lot of it, and you will find out what combo's work well together and what kind of numbers to expect.
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
Cause they both outflow the 853's. Head flow is a big factor in the power equation. You can use the 853's no problem though. I don't remember the specs of the Trex cam off hand, but I know it is a rather stout cam. I'm more of a fan of a mid-range cam, but that's just me. Do your research, a lot of it, and you will find out what combo's work well together and what kind of numbers to expect.
2- Only ported 5.3L heads outflow stock castings
3- 6.0 castings are the same as LS6/LS2 but with bigger chambers 72cc
4- T-Rex is a 242/248 110+0 LSA adertised.
5- Dynamic Compression Ratio with .020 853s and T-rex is ~7.4x DCR, it will have a saggy below curve trq and power, it will need to rev to the moon to make any power, bottom line wrong cam unless it is a full fledged drag car.
Please avoid giving advice on things you do not know
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Verdad Gallardo 1- 5.3 do not outflow LS1 castings in stock form (smaller valves, smaller runners)
2- Only ported 5.3L heads outflow stock castings
3- 6.0 castings are the same as LS6/LS2 but with bigger chambers 72cc
4- T-Rex is a 242/248 110+0 LSA adertised.
5- Dynamic Compression Ratio with .020 853s and T-rex is ~7.4x DCR, it will have a saggy below curve trq and power, it will need to rev to the moon to make any power, bottom line wrong cam unless it is a full fledged drag car.
Please avoid giving advice on things you do not know
2- Only ported 5.3L heads outflow stock castings
3- 6.0 castings are the same as LS6/LS2 but with bigger chambers 72cc
4- T-Rex is a 242/248 110+0 LSA adertised.
5- Dynamic Compression Ratio with .020 853s and T-rex is ~7.4x DCR, it will have a saggy below curve trq and power, it will need to rev to the moon to make any power, bottom line wrong cam unless it is a full fledged drag car.
Please avoid giving advice on things you do not know
I knew #3, but bigger combustion chambers will yeild lower CR.
I didn't know #4 exactly, but I knew it was a huge cam.
As for #5, I never advised to go with a T-rex cam.
I don't know everything, but I don't know nothing.
My advise would be to run CNC'd 243's or 5.3's, maybe a 23x/23x cam, and all the supporting mods.
and running the t-rex in a stock compression 346 isn't a mismatch? obviously the cam needs more compression to shine, but losing less than a point in compression isn't going to hurt him given the difference in cubes. also, i believe it is ground with 4 degrees advance. people have been successfully running 250* duration cams with ~9.5:1 compression for decades. it's a budget setup that will still run well with A LOT of room to grow. what's so wrong with that?
not to mention, if this is going in a 4k+ stalled auto car he will NEVER know the "saggy below curve" torque and power. also consider the extra cubes will aid in limiting the rpm required to make power. it's one thing to look at a dynograph and critique with speculation, it's another thing to go drive the car in the real world. people are quick to point out poor setups having never driven or even been around something similar.
not to mention, if this is going in a 4k+ stalled auto car he will NEVER know the "saggy below curve" torque and power. also consider the extra cubes will aid in limiting the rpm required to make power. it's one thing to look at a dynograph and critique with speculation, it's another thing to go drive the car in the real world. people are quick to point out poor setups having never driven or even been around something similar.
I am pretty sure the trex is ground with 0 advace as the pistons would meet the valves. My 236/236 is ground on a 110+4 and everyone says i have less than .050 intake ptvc.
It's not like a HUGE increase in cubic inches though guys. The bigger the cam the lower your dynamic compression ratio (ratio of rotating motor). A smaller cam will maintain a higher dynamic compression ratio because it has less valve overlap.
Listen to PREDATOR Z he knows what hes talking about and has responded to nearly all of my valve train threads and was right in every one of them.
It's not like a HUGE increase in cubic inches though guys. The bigger the cam the lower your dynamic compression ratio (ratio of rotating motor). A smaller cam will maintain a higher dynamic compression ratio because it has less valve overlap.
Listen to PREDATOR Z he knows what hes talking about and has responded to nearly all of my valve train threads and was right in every one of them.
ok, im getting the lq4 for cheap, the heads for free, and the cam for very cheap. Once again BUDGET! I agree w s346-you telling me a an untouched 346 w/ a trex is an optimized setup? Of course it would need better flowing heads and a higher cr but there are a ton of happy people running it-even thunder advertised it w/ stock heads.
This is not an all out race motor, car has been dead for four years, and im just trying to get it to run and have a little fun for the rest of the summer before I leave for air force.
Now, which head gaskets w/ milled .020 853's, what should my cr be (not static,) and Im pretty sure there wont be any ptv problems although im going to doulbe check.
Thanks again.
This is not an all out race motor, car has been dead for four years, and im just trying to get it to run and have a little fun for the rest of the summer before I leave for air force.
Now, which head gaskets w/ milled .020 853's, what should my cr be (not static,) and Im pretty sure there wont be any ptv problems although im going to doulbe check.
Thanks again.
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
^^perfect exemple^^
Yeap, I think you are right, I know little about cams, please forgive me 
Low DCR, means poor cylinder pressures, which means low output.
In any case, why am I even arguing, you guys know best, good luck.
Originally Posted by s346k
and running the t-rex in a stock compression 346 isn't a mismatch? obviously the cam needs more compression to shine, but losing less than a point in compression isn't going to hurt him given the difference in cubes. also, i believe it is ground with 4 degrees advance. people have been successfully running 250* duration cams with ~9.5:1 compression for decades. it's a budget setup that will still run well with A LOT of room to grow. what's so wrong with that?
not to mention, if this is going in a 4k+ stalled auto car he will NEVER know the "saggy below curve" torque and power. also consider the extra cubes will aid in limiting the rpm required to make power. it's one thing to look at a dynograph and critique with speculation, it's another thing to go drive the car in the real world. people are quick to point out poor setups having never driven or even been around something similar.
not to mention, if this is going in a 4k+ stalled auto car he will NEVER know the "saggy below curve" torque and power. also consider the extra cubes will aid in limiting the rpm required to make power. it's one thing to look at a dynograph and critique with speculation, it's another thing to go drive the car in the real world. people are quick to point out poor setups having never driven or even been around something similar.
Low DCR, means poor cylinder pressures, which means low output.
In any case, why am I even arguing, you guys know best, good luck.
predator z, I by no means am doubting your knowledge but for the money i will be spending I will be happy w/ results similar to ponyhater27 setup. Once again, your trying to get me to spend more money than intended. I know he isn't make the power he should but the point is room to grow.
Ponyhater27, where your heads milled? How much?
Once again, if I do choose to mill the heads, how much and WHICH THICKNESS GASKETS? I would like to get my cr back up. Predator, I don't know much about dcr but w/ what im trying to do could you advise me on what I should do w/ what I have to make the best of it? Not trying to be an *** im just getting frustrated and am about to say to the hell w/ it and sell the rolling chassis, start over again when I get our of AF. Thanks
Ponyhater27, where your heads milled? How much?
Once again, if I do choose to mill the heads, how much and WHICH THICKNESS GASKETS? I would like to get my cr back up. Predator, I don't know much about dcr but w/ what im trying to do could you advise me on what I should do w/ what I have to make the best of it? Not trying to be an *** im just getting frustrated and am about to say to the hell w/ it and sell the rolling chassis, start over again when I get our of AF. Thanks
My heads where milled enough to true them up or thats at least what I was told. My car makes good power for the money I have in it and I really can't complain. I do know that to make more power I will need better flowing heads and a higher compression ratio and some bigger injectors. I just used a stock thickness multilayer gasket. If your not worried about power or anything just put it together and get a good tune and drive it around and then later on put nicer heads on it.
