Questions on a different LQ4 build...opinions wanted, please.
11-20-2010, 11:02 AM
#21
I am not convinced that porting will necessarily have an adverse affect on low end torque or shift the peak torque higher.
I added a set of TFS 215s (milled to 61.5cc) to my LS6, which already had a baby EPS cam. The peak torque before adding the 215s was at 4,800 rpm and was still at 4,800 after adding the 215s. Additionally the 215s resulted in torque at least equal to the 243s everywhere up to 3,400 rpm and significantly above the 243s throughout the 3,400 rpm to 4,800 rpm range. In short the addition of 215s only helped the torque values.
I added a set of TFS 215s (milled to 61.5cc) to my LS6, which already had a baby EPS cam. The peak torque before adding the 215s was at 4,800 rpm and was still at 4,800 after adding the 215s. Additionally the 215s resulted in torque at least equal to the 243s everywhere up to 3,400 rpm and significantly above the 243s throughout the 3,400 rpm to 4,800 rpm range. In short the addition of 215s only helped the torque values.
Porting usually involves removing material. The point is to shape the port differently and to make cross sections larger in order to appropriately place the torque curve in a range suitable for the cubic inches and RPM range of the engine.
Aftermarket castings, however, can start out with material in places that help boost the entire curve without changing cross sections and without shifting it higher in the RPM range. Not to mention, the valvejob was likely a little better than stock.
With small cams, the port has a minimal effect anyways. Up until a certain lift-valve diameter ratio (some say ~.32), the valve is going to be the restriction and 99% of the gains you will see will be made by focusing on that area. The cam he is using is well below that point so changes in the port should translate into very, very minimal gains, but a real valvejob (not just the "competition" 30-45-60) will be way more cost effective.
11-20-2010, 11:10 AM
#22
Never get caught up in the high flow number must mean better head theory that goes around on here. its not how much material is taken out , its where its taken from that makes or breaks a head. My heads on my t/a only flow 262cfm (ported 241 casting) with 2.02 int. valves and stock exh valves with a good valve job.
When i had my friend and shop owner do my heads, he told me he did not want to make the heads all top end, he wanted to make tq so he just did a bowl job, short turn work and valve job with the bigger int. valves and even though they dont make big numbers on the bench, they work great on the car. dyno and track.
441/410 tq with f13 cam and trapped 121.3
now they are on an lq4 short block with f14 cam and trapped 123 at 3850lb race weight after opening the combustion chamber some to match my 4" bore.
no dyno on the lq4 yet , next week it will though . going to fine tune it at Eps.
When i had my friend and shop owner do my heads, he told me he did not want to make the heads all top end, he wanted to make tq so he just did a bowl job, short turn work and valve job with the bigger int. valves and even though they dont make big numbers on the bench, they work great on the car. dyno and track.
441/410 tq with f13 cam and trapped 121.3
now they are on an lq4 short block with f14 cam and trapped 123 at 3850lb race weight after opening the combustion chamber some to match my 4" bore.
no dyno on the lq4 yet , next week it will though . going to fine tune it at Eps.
11-20-2010, 11:20 AM
#23
GM 243's and an aftermarket casting like the TFS heads are an apples to oranges comparison. An entirely new casting is not really comparable to a ported GM casting.
Porting usually involves removing material. The point is to shape the port differently and to make cross sections larger in order to appropriately place the torque curve in a range suitable for the cubic inches and RPM range of the engine.
Aftermarket castings, however, can start out with material in places that help boost the entire curve without changing cross sections and without shifting it higher in the RPM range. Not to mention, the valvejob was likely a little better than stock.
With small cams, the port has a minimal effect anyways. Up until a certain lift-valve diameter ratio (some say ~.32), the valve is going to be the restriction and 99% of the gains you will see will be made by focusing on that area. The cam he is using is well below that point so changes in the port should translate into very, very minimal gains, but a real valvejob (not just the "competition" 30-45-60) will be way more cost effective.
Porting usually involves removing material. The point is to shape the port differently and to make cross sections larger in order to appropriately place the torque curve in a range suitable for the cubic inches and RPM range of the engine.
Aftermarket castings, however, can start out with material in places that help boost the entire curve without changing cross sections and without shifting it higher in the RPM range. Not to mention, the valvejob was likely a little better than stock.
With small cams, the port has a minimal effect anyways. Up until a certain lift-valve diameter ratio (some say ~.32), the valve is going to be the restriction and 99% of the gains you will see will be made by focusing on that area. The cam he is using is well below that point so changes in the port should translate into very, very minimal gains, but a real valvejob (not just the "competition" 30-45-60) will be way more cost effective.
Never get caught up in the high flow number must mean better head theory that goes around on here. its not how much material is taken out , its where its taken from that makes or breaks a head. My heads on my t/a only flow 262cfm (ported 241 casting) with 2.02 int. valves and stock exh valves with a good valve job.
When i had my friend and shop owner do my heads, he told me he did not want to make the heads all top end, he wanted to make tq so he just did a bowl job, short turn work and valve job with the bigger int. valves and even though they dont make big numbers on the bench, they work great on the car. dyno and track.
441/410 tq with f13 cam and trapped 121.3
now they are on an lq4 short block with f14 cam and trapped 123 at 3850lb race weight after opening the combustion chamber some to match my 4" bore.
no dyno on the lq4 yet , next week it will though . going to fine tune it at Eps.
When i had my friend and shop owner do my heads, he told me he did not want to make the heads all top end, he wanted to make tq so he just did a bowl job, short turn work and valve job with the bigger int. valves and even though they dont make big numbers on the bench, they work great on the car. dyno and track.
441/410 tq with f13 cam and trapped 121.3
now they are on an lq4 short block with f14 cam and trapped 123 at 3850lb race weight after opening the combustion chamber some to match my 4" bore.
no dyno on the lq4 yet , next week it will though . going to fine tune it at Eps.
11-20-2010, 02:00 PM
#24
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So....the general consesus is a good valve job and some bowl work and leave the ports alone? Alright!
Anybody want to double check, or at atleast say, 'yeah that sounds about right', my numbers below?
A stock lq4 with around a +.010" deck with .041" gasket would net me a .031" quench. A bit on the tight side maybe?
So, with a .041" compressed gasket, assuming the bore is around 4.085", and 59cc chamber heads, the SCR should be around 11.3:1 with the stock dished lq4 pistons?
Sound about right?
Anybody want to double check, or at atleast say, 'yeah that sounds about right', my numbers below?
A stock lq4 with around a +.010" deck with .041" gasket would net me a .031" quench. A bit on the tight side maybe?
So, with a .041" compressed gasket, assuming the bore is around 4.085", and 59cc chamber heads, the SCR should be around 11.3:1 with the stock dished lq4 pistons?
Sound about right?
11-26-2010, 03:19 PM
#25
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So....the general consesus is a good valve job and some bowl work and leave the ports alone? Alright!
Anybody want to double check, or at atleast say, 'yeah that sounds about right', my numbers below?
A stock lq4 with around a +.010" deck with .041" gasket would net me a .031" quench. A bit on the tight side maybe?
So, with a .041" compressed gasket, assuming the bore is around 4.085", and 59cc chamber heads, the SCR should be around 11.3:1 with the stock dished lq4 pistons? Should I stick to 61cc to run on 93 octane?
Sound about right?
Anybody want to double check, or at atleast say, 'yeah that sounds about right', my numbers below?
A stock lq4 with around a +.010" deck with .041" gasket would net me a .031" quench. A bit on the tight side maybe?
So, with a .041" compressed gasket, assuming the bore is around 4.085", and 59cc chamber heads, the SCR should be around 11.3:1 with the stock dished lq4 pistons? Should I stick to 61cc to run on 93 octane?
Sound about right?
