just picked up a 5.3
1.89 intake valves and 1.55 for exhaust valves if memory serves me correct. The seats are big enough to have 2.02 intake/1.575exhaust valves cut in no problem. Just be careful with PTV clearance if you get 1.575's and 2.02's and are running a big cam on a stock bottom end.
so i stripped the motor of the heads and stuff today and the cylinders still have good cross hatches (amazing for 90k mi.) but on cyl. 1 and 2 the intake valves were white could those to cyl. be lean for some reason? maybe the injectors are clogged?
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With that said, 706 heads are fine on a 5.3L even with a decent cam. There is no real need for bigger valves on the 5.3L because it doesn't flow as much as the 5.7 and 6.0+. 5.3L's are hard pressed to support a cam much bigger than in the 22x range anyways so a huge cam will only rob more low end. But the popular choices are in the 206-224 range for duration.
The 02+ LS6 cam and springs should do wonders; however I'd recommend taking the heads off and having them milled for a compression bump. Stock is 9.4:1 on most 5.3L's, and 10:1 would offer a much better feel everywhere, especially down low. The LS6 cam will start to rob the 5.3L of low end torque and make awesome mid-to-upper power. Tuning will definitely help give you back some low end grunt, as well as milling the heads for 9.8-10.x on pump gas. 11:1 might get a little tight on the timing with a "small" cam such as the LS6 cam, so if it were my 5.3L I'd shoot for 10.3-10.6 and have a stout motor for sure.
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Verdad Gallardo I think you might have misunderstood the OP. The title is "just picked up a 5.3" and he's asking about 706 heads which are stock on 5.3L's, and I believe you're talking about putting 706 heads on an LS1.
With that said, 706 heads are fine on a 5.3L even with a decent cam. There is no real need for bigger valves on the 5.3L because it doesn't flow as much as the 5.7 and 6.0+. 5.3L's are hard pressed to support a cam much bigger than in the 22x range anyways so a huge cam will only rob more low end. But the popular choices are in the 206-224 range for duration.
The 02+ LS6 cam and springs should do wonders; however I'd recommend taking the heads off and having them milled for a compression bump. Stock is 9.4:1 on most 5.3L's, and 10:1 would offer a much better feel everywhere, especially down low. The LS6 cam will start to rob the 5.3L of low end torque and make awesome mid-to-upper power. Tuning will definitely help give you back some low end grunt, as well as milling the heads for 9.8-10.x on pump gas. 11:1 might get a little tight on the timing with a "small" cam such as the LS6 cam, so if it were my 5.3L I'd shoot for 10.3-10.6 and have a stout motor for sure.
With that said, 706 heads are fine on a 5.3L even with a decent cam. There is no real need for bigger valves on the 5.3L because it doesn't flow as much as the 5.7 and 6.0+. 5.3L's are hard pressed to support a cam much bigger than in the 22x range anyways so a huge cam will only rob more low end. But the popular choices are in the 206-224 range for duration.
The 02+ LS6 cam and springs should do wonders; however I'd recommend taking the heads off and having them milled for a compression bump. Stock is 9.4:1 on most 5.3L's, and 10:1 would offer a much better feel everywhere, especially down low. The LS6 cam will start to rob the 5.3L of low end torque and make awesome mid-to-upper power. Tuning will definitely help give you back some low end grunt, as well as milling the heads for 9.8-10.x on pump gas. 11:1 might get a little tight on the timing with a "small" cam such as the LS6 cam, so if it were my 5.3L I'd shoot for 10.3-10.6 and have a stout motor for sure.
My answer is...it depends. Boost or nitrous?
Low boost is ok on high compression. Medium boost levels are still ok on high compression, as long as the tune is spot on and an effective intercooler is somewhere in the intake piping. High boost does not like high compression, so you'll either have to run race gas, pull a butt load of timing, or make sure the boost charge is no hotter than ambient air temp (using a big intercooler with extra cooling, meth injection, nitrous cooling, ect ect). Typically high boost coincides with less compression, which stock 9.4:1 compression is ideal for.
Nitrous on the other hand doesn't care either way. I've heard it actually likes high compression, and I can see why. When you're spraying a wet shot of nitrous, chances are it's mixed with premium gasoline or better even. Nitrous is two parts nitrogen and one part oxygen and when heated up inside a combustion chamber, the nitrogen and oxygen atoms split. The nitrogen cools the combustion chamber, while the oxygen gets burned to make your power. Higher compression makes this process happen sooner and more efficiently, but I'll leave the specifics to a chemistry major to answer.
As for what's safe...again, "depends". 125 I'd say is safe given that your tune is accurate and the gasoline is of higher octane levels and of good quality and that all safety sensors/switches are in place that come with most kits these days. 200 I'd still say is safe. 250? Ehh...maybe not on stock internals for long, but it's been done plenty of times before. These new motors are built tough, start with a 125 shot and move up from there.
Low boost is ok on high compression. Medium boost levels are still ok on high compression, as long as the tune is spot on and an effective intercooler is somewhere in the intake piping. High boost does not like high compression, so you'll either have to run race gas, pull a butt load of timing, or make sure the boost charge is no hotter than ambient air temp (using a big intercooler with extra cooling, meth injection, nitrous cooling, ect ect). Typically high boost coincides with less compression, which stock 9.4:1 compression is ideal for.
Nitrous on the other hand doesn't care either way. I've heard it actually likes high compression, and I can see why. When you're spraying a wet shot of nitrous, chances are it's mixed with premium gasoline or better even. Nitrous is two parts nitrogen and one part oxygen and when heated up inside a combustion chamber, the nitrogen and oxygen atoms split. The nitrogen cools the combustion chamber, while the oxygen gets burned to make your power. Higher compression makes this process happen sooner and more efficiently, but I'll leave the specifics to a chemistry major to answer.
As for what's safe...again, "depends". 125 I'd say is safe given that your tune is accurate and the gasoline is of higher octane levels and of good quality and that all safety sensors/switches are in place that come with most kits these days. 200 I'd still say is safe. 250? Ehh...maybe not on stock internals for long, but it's been done plenty of times before. These new motors are built tough, start with a 125 shot and move up from there.
well i think nitrous is gonna be cheaper... and i am in high school so probably nitrous
so how much power you think i could make with this setup
milled 706 heads (10.5:1)
ported TB
truck intake
LS6 cam/springs (204/218 .551/.547)
32# injec
LT's
150shot
good tune
so how much power you think i could make with this setup
milled 706 heads (10.5:1)
ported TB
truck intake
LS6 cam/springs (204/218 .551/.547)
32# injec
LT's
150shot
good tune
Hmm...the 5.3L probably isn't going to be all that fun in the fox body but at least you can get everything finished up with the 5.3L and later on down the road swap in a 6.0L+ for more power. If everything works with the 5.3L, the other Gen III motors will swap in very easily.
The reason I say that is because the 5.3L isn't designed to be a peppy motor. It has a small bore and large crank when compared to it's bigger displacement brothers. It's put in trucks, SUV's and heavy cars centered around low end torque, stock-ish red lines and decent gas mileage. The heads are small, actually flowing the least amount compared to every other Gen III/IV head, and as itchygomey98 pointed out, the valves are pretty weak for making good N/A power.
However, with a forced induction system like a nitrous setup, you can still have good fun. Actually, on second thought, with you being in high school, this car with a 5.3L might save you a few tickets. Later on you could rebuild it by boring the 5.3L out to 5.7L, but after all that machine work you've basically spent twice that of what a stock 6.0L costs. Now you're talking fun.
With the LS6 cam, tune, and minor bolt on's I'd suspect you'll be putting down somewhere around 300rwhp, especially with the 10.5 compression. That should sit you around 340-350 flywheel horsepower, up at least 50 over stock I'd imagine. That should be pretty fun for awhile I think.
The reason I say that is because the 5.3L isn't designed to be a peppy motor. It has a small bore and large crank when compared to it's bigger displacement brothers. It's put in trucks, SUV's and heavy cars centered around low end torque, stock-ish red lines and decent gas mileage. The heads are small, actually flowing the least amount compared to every other Gen III/IV head, and as itchygomey98 pointed out, the valves are pretty weak for making good N/A power.
However, with a forced induction system like a nitrous setup, you can still have good fun. Actually, on second thought, with you being in high school, this car with a 5.3L might save you a few tickets. Later on you could rebuild it by boring the 5.3L out to 5.7L, but after all that machine work you've basically spent twice that of what a stock 6.0L costs. Now you're talking fun.
With the LS6 cam, tune, and minor bolt on's I'd suspect you'll be putting down somewhere around 300rwhp, especially with the 10.5 compression. That should sit you around 340-350 flywheel horsepower, up at least 50 over stock I'd imagine. That should be pretty fun for awhile I think.
Hmm...the 5.3L probably isn't going to be all that fun in the fox body but at least you can get everything finished up with the 5.3L and later on down the road swap in a 6.0L+ for more power. If everything works with the 5.3L, the other Gen III motors will swap in very easily.
The reason I say that is because the 5.3L isn't designed to be a peppy motor. It has a small bore and large crank when compared to it's bigger displacement brothers. It's put in trucks, SUV's and heavy cars centered around low end torque, stock-ish red lines and decent gas mileage. The heads are small, actually flowing the least amount compared to every other Gen III/IV head, and as itchygomey98 pointed out, the valves are pretty weak for making good N/A power.
However, with a forced induction system like a nitrous setup, you can still have good fun. Actually, on second thought, with you being in high school, this car with a 5.3L might save you a few tickets. Later on you could rebuild it by boring the 5.3L out to 5.7L, but after all that machine work you've basically spent twice that of what a stock 6.0L costs. Now you're talking fun.
With the LS6 cam, tune, and minor bolt on's I'd suspect you'll be putting down somewhere around 300rwhp, especially with the 10.5 compression. That should sit you around 340-350 flywheel horsepower, up at least 50 over stock I'd imagine. That should be pretty fun for awhile I think.
The reason I say that is because the 5.3L isn't designed to be a peppy motor. It has a small bore and large crank when compared to it's bigger displacement brothers. It's put in trucks, SUV's and heavy cars centered around low end torque, stock-ish red lines and decent gas mileage. The heads are small, actually flowing the least amount compared to every other Gen III/IV head, and as itchygomey98 pointed out, the valves are pretty weak for making good N/A power.
However, with a forced induction system like a nitrous setup, you can still have good fun. Actually, on second thought, with you being in high school, this car with a 5.3L might save you a few tickets. Later on you could rebuild it by boring the 5.3L out to 5.7L, but after all that machine work you've basically spent twice that of what a stock 6.0L costs. Now you're talking fun.
With the LS6 cam, tune, and minor bolt on's I'd suspect you'll be putting down somewhere around 300rwhp, especially with the 10.5 compression. That should sit you around 340-350 flywheel horsepower, up at least 50 over stock I'd imagine. That should be pretty fun for awhile I think.
if i swapped in ls7 high rev lifters and dif rod bolts would i be able to rev it higher?
do you think i would have more fun with a forced induction setup like a T70 with a small A/R like .68?
also would i be better off using 4.8 pistons and rods (flat tops) instead of milling the heads?
Last edited by nastychevelle; Dec 15, 2008 at 10:32 AM.
if i swapped in ls7 high rev lifters and dif rod bolts would i be able to rev it higher?
do you think i would have more fun with a forced induction setup like a T70 with a small A/R like .68?
also would i be better off using 4.8 pistons and rods (flat tops) instead of milling the heads?
do you think i would have more fun with a forced induction setup like a T70 with a small A/R like .68?
also would i be better off using 4.8 pistons and rods (flat tops) instead of milling the heads?
Turbocharger = fun? You bet! Though, you bought the 5.3L for budget reasons, and a well thought out and put together turbo system will be quite expensive. More expensive I think than buying a 6.0L with nitrous instead of turbocharging a 5.3L.
You'll obviously have to take the 5.3L apart in order to swap in the 4.8L pistons, but not the rods, those are too long. However, the cost of completely rebuilding the bottom end for a bump in compression will be at least 10 times the cost of just milling the heads. Around here, milling the heads is $52 for the pair, and you'll need new head gaskets and head bolts. Having the rotating assembly balanced for the new pistons and rebuilding the bottom end will cost no less than $500 at a reputable shop, on top of also needing new head gaskets and head bolts. Sounds like an expensive way to gain 1 point in compression.
ahhh hell I missed that it was an entire 5.3 engine. I was under the assumption it was 5.3 heads on a 5.7. Everthing I said about valve sizes is still true, but it won't give you the 11:1 that I mentioned earlier. 11:1 is what those heads on a 5.7 will yield.
???????????sigh?? Hmm...the 5.3L probably isn't going to be all that fun in the fox body but at least you can get everything finished up with the 5.3L and later on down the road swap in a 6.0L+ for more power. If everything works with the 5.3L, the other Gen III motors will swap in very easily.
The reason I say that is because the 5.3L isn't designed to be a peppy motor. It has a small bore and large crank when compared to it's bigger displacement brothers. It's put in trucks, SUV's and heavy cars centered around low end torque, stock-ish red lines and decent gas mileage. The heads are small, actually flowing the least amount compared to every other Gen III/IV head, and as itchygomey98 pointed out, the valves are pretty weak for making good N/A power.
However, with a forced induction system like a nitrous setup, you can still have good fun. Actually, on second thought, with you being in high school, this car with a 5.3L might save you a few tickets. Later on you could rebuild it by boring the 5.3L out to 5.7L, but after all that machine work you've basically spent twice that of what a stock 6.0L costs. Now you're talking fun.
With the LS6 cam, tune, and minor bolt on's I'd suspect you'll be putting down somewhere around 300rwhp, especially with the 10.5 compression. That should sit you around 340-350 flywheel horsepower, up at least 50 over stock I'd imagine. That should be pretty fun for awhile I think.
The reason I say that is because the 5.3L isn't designed to be a peppy motor. It has a small bore and large crank when compared to it's bigger displacement brothers. It's put in trucks, SUV's and heavy cars centered around low end torque, stock-ish red lines and decent gas mileage. The heads are small, actually flowing the least amount compared to every other Gen III/IV head, and as itchygomey98 pointed out, the valves are pretty weak for making good N/A power.
However, with a forced induction system like a nitrous setup, you can still have good fun. Actually, on second thought, with you being in high school, this car with a 5.3L might save you a few tickets. Later on you could rebuild it by boring the 5.3L out to 5.7L, but after all that machine work you've basically spent twice that of what a stock 6.0L costs. Now you're talking fun.
With the LS6 cam, tune, and minor bolt on's I'd suspect you'll be putting down somewhere around 300rwhp, especially with the 10.5 compression. That should sit you around 340-350 flywheel horsepower, up at least 50 over stock I'd imagine. That should be pretty fun for awhile I think.
op that setup will get you easy 11s in a fox maybe better...no need for a heavier bigger valve on a 3.77 bore..i have an identicle engine im building to replace my damaged ls1...the 706 heads flow 226 cfm in stock form thats enough to make plenty of power...theres an article here where a sponsor put this same setup in an 01 ta and made 327 rwhp...that in a 3000lb fox will kick ***...just do a search on cammed lm7's
little proof ...not peppy you say????hmmm. guess these will be unpeppy turds
baby cam
https://ls1tech.com/forums/dynamomet...hp-314-tq.html
ls6 cam and headers
https://ls1tech.com/forums/conversio...onversion.html
10s with an ms3 and juice....
https://ls1tech.com/forums/midwester...10s-5-3-a.html
hmm un peppy....
theres one over on the truck board where vengeance got 390rwhp cam only out of a 4.8...all the ls motors are peppy and all respond well to any mod...
baby cam
https://ls1tech.com/forums/dynamomet...hp-314-tq.html
ls6 cam and headers
https://ls1tech.com/forums/conversio...onversion.html
10s with an ms3 and juice....
https://ls1tech.com/forums/midwester...10s-5-3-a.html
hmm un peppy....
theres one over on the truck board where vengeance got 390rwhp cam only out of a 4.8...all the ls motors are peppy and all respond well to any mod...