heads for 4.125 bore and help me choose what parts
08-15-2018, 06:36 AM
#21
i got responses from a few guys i was looking for so thanks......i also got another answer i was looking for but didn't ask and that was would the ls3 heads flow well enough to shift at 7500 if i chose the LLSR route but i got that answer.......not ready to turn this into an intake. im definitely liking the idea of my current heads....
on a head that is advertised for a 4.00 or bigger bore vs a head designed for a 4.125 or bigger bore, what is the difference between them? i know valve sizes, but what makes you unable to run the 4.125s heads on a 4.00 bore?
on a head that is advertised for a 4.00 or bigger bore vs a head designed for a 4.125 or bigger bore, what is the difference between them? i know valve sizes, but what makes you unable to run the 4.125s heads on a 4.00 bore?
08-15-2018, 06:39 AM
#22
hammer do you have a dyno graph? and sorry to disappoint you but if i go hydraulic roller ill probably get a rod mod LS3 intake, at least to start out....which we can discuss later
im really leaking towards running what i got.....LS7 heads wouldn't fit my 60% low end 40% high end goals....now if my goals were 60%high end 40 % low end then the ls7 would fit.....the cathedrals may still be in the picture, but the investment would be a lot more than what i have now, and those are designed for a 4" or bigger just like my ls3 heads.
im really leaking towards running what i got.....LS7 heads wouldn't fit my 60% low end 40% high end goals....now if my goals were 60%high end 40 % low end then the ls7 would fit.....the cathedrals may still be in the picture, but the investment would be a lot more than what i have now, and those are designed for a 4" or bigger just like my ls3 heads.
Last edited by Floorman279; 08-15-2018 at 06:43 AM. Reason: .......
08-15-2018, 07:14 AM
#23
Run the heads you have but get a piston and head gasket to get compression and quench right.
my 427 dart SHP-LS-Next-Block has 8cc wiseco pistons and heads milled to 64 cc. Piston is 0decked and going with a .036 cometic head gasket to set me at 11.95 compression and .036 quench.
I had my ls3 heads ported and running a llsr cam from Geoff Skinner at EPS. And as suggested earlier to you by Big Hammer I am using the Holley sniper intake low profile.
Good luck with the build
my 427 dart SHP-LS-Next-Block has 8cc wiseco pistons and heads milled to 64 cc. Piston is 0decked and going with a .036 cometic head gasket to set me at 11.95 compression and .036 quench.
I had my ls3 heads ported and running a llsr cam from Geoff Skinner at EPS. And as suggested earlier to you by Big Hammer I am using the Holley sniper intake low profile.
Good luck with the build
08-15-2018, 08:41 AM
#26
10 Second Club
yes using the ls3 heads on the larger bore will just potentially let them flow more. I asked mast what my heads would flow on a 4.125 bore and they just said more but wouldn’t tell me how much
08-15-2018, 09:29 AM
#27
Anybody have PROOF that a LS3 head is better down low vs the LS7?
1) Cam choice
2 ) Intake used
3 ) Size of runner or CSA
LS7 heads, for example, are praised for their raised runners because air does not have a sharp angle at the short-turn radius VS say a ls3 head. The short-turn radius is directly related to torque, mid-range power, and top-end power. As is the runner size *CSA and runner placement. Now ask yourself if all stays the same such as using a factory style intake and the same cam....Which runner is larger in terms of shear size and sits lower. Ls3!!!!! One would think that just off the top of my head that the Ls7 would make more TQ....The cathedral heads have a even smaller CSA which leads one to think it would be even better down low. CFM doesn't make TQ it's the Velocity & CFM @ lower lifts which makes TQ with smaller runners. Larger runners generally lose TQ or move the TQ up in the RPM band.
08-15-2018, 09:58 AM
#28
10 Second Club
hammer do you have a dyno graph? and sorry to disappoint you but if i go hydraulic roller ill probably get a rod mod LS3 intake, at least to start out....which we can discuss later
im really leaking towards running what i got.....LS7 heads wouldn't fit my 60% low end 40% high end goals....now if my goals were 60%high end 40 % low end then the ls7 would fit.....the cathedrals may still be in the picture, but the investment would be a lot more than what i have now, and those are designed for a 4" or bigger just like my ls3 heads.
im really leaking towards running what i got.....LS7 heads wouldn't fit my 60% low end 40% high end goals....now if my goals were 60%high end 40 % low end then the ls7 would fit.....the cathedrals may still be in the picture, but the investment would be a lot more than what i have now, and those are designed for a 4" or bigger just like my ls3 heads.
my engine info and dyno sheets are in the dyno section in my thread. Don’t put a piece of **** stock intake on it
08-15-2018, 02:03 PM
#29
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The Heads you have + ~11.5-12.0:1 Compression, Mid-Length Fast, and Medium LLSR ~(245*/255*) ~.680"/.660"
LSA Specced by Steve AKA SpeedTigger @ CamMotion will give you all the torque you can use and 600+RWHP @ ~6800 RPM.
I made 690 @ crank & 590+ RWHP (from 6800-7300) with those heads(Ported by Tony Mamo), 393",
Schmedium LLSR (243*/249*), Mid-Length Fast & 11.7:1 comp.
My Bore ?.......... 4.175",......... Crank only 3.60"
With a 4.0" Stroke you will have torque everywhere unless you put a HUGE Cam in there.
LSA Specced by Steve AKA SpeedTigger @ CamMotion will give you all the torque you can use and 600+RWHP @ ~6800 RPM.
I made 690 @ crank & 590+ RWHP (from 6800-7300) with those heads(Ported by Tony Mamo), 393",
Schmedium LLSR (243*/249*), Mid-Length Fast & 11.7:1 comp.
My Bore ?.......... 4.175",......... Crank only 3.60"
With a 4.0" Stroke you will have torque everywhere unless you put a HUGE Cam in there.
08-15-2018, 08:20 PM
#31
ModSquad
iTrader: (6)
Didn't find any test.....What makes HP and TQ down low
1) Cam choice
2 ) Intake used
3 ) Size of runner or CSA
LS7 heads, for example, are praised for their raised runners because air does not have a sharp angle at the short-turn radius VS say a ls3 head. The short-turn radius is directly related to torque, mid-range power, and top-end power. As is the runner size *CSA and runner placement. Now ask yourself if all stays the same such as using a factory style intake and the same cam....Which runner is larger in terms of shear size and sits lower. Ls3!!!!! One would think that just off the top of my head that the Ls7 would make more TQ....The cathedral heads have a even smaller CSA which leads one to think it would be even better down low. CFM doesn't make TQ it's the Velocity & CFM @ lower lifts which makes TQ with smaller runners. Larger runners generally lose TQ or move the TQ up in the RPM band.
1) Cam choice
2 ) Intake used
3 ) Size of runner or CSA
LS7 heads, for example, are praised for their raised runners because air does not have a sharp angle at the short-turn radius VS say a ls3 head. The short-turn radius is directly related to torque, mid-range power, and top-end power. As is the runner size *CSA and runner placement. Now ask yourself if all stays the same such as using a factory style intake and the same cam....Which runner is larger in terms of shear size and sits lower. Ls3!!!!! One would think that just off the top of my head that the Ls7 would make more TQ....The cathedral heads have a even smaller CSA which leads one to think it would be even better down low. CFM doesn't make TQ it's the Velocity & CFM @ lower lifts which makes TQ with smaller runners. Larger runners generally lose TQ or move the TQ up in the RPM band.
Nothing wrong with your current heads at all. Stay away from the GM ls7 castings, unless you want reliability issues. They flow well, but even when re-done with better valve guides, still aren’t lasting 10k miles. I know you don’t want to go there yet, but...you really have to invest in a intake manifold here. It will compliment the package very well.
08-15-2018, 09:08 PM
#34
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Originally Posted by big hammer
sounds like you really don’t want this thing to perform. It’s a 429. You’ll have lots of torque regardless what you do with it. All
my engine info and dyno sheets are in the dyno section in my thread. Don’t put a piece of **** stock intake on it
my engine info and dyno sheets are in the dyno section in my thread. Don’t put a piece of **** stock intake on it
08-15-2018, 11:15 PM
#36
A 429/TFS 255 headed engine asking for a 6800 peak with close to 600 rwhp. Heck we can just look @ the 427 TFS head comparison and add:
1) Better cam LLSR
2) More Compression
3) Vacuum pump
All the builds I've listed besides 1Sickengine (6.2 Ls3) would make 600 rwhp with a LLSR and pretty much NOTHING else. Your only asking for around 670 to 690 @ the crank. Don't overthink it! There ARE NO new combinations under the sun. Find one that's close to yours and copy it and add better stuff where needed for more HP. To Easy, simple math.
TFS head test: BTR LS7 STAGE IV CAM : Cam specs are 247/258 112+3 over 600 lift
TFS 245: 102mm FAST LSXR intake with matching 102mm Big Mouth throttle body. 1.7 rocker ratio
The 245-headed 427 produced peak numbers of 648 hp at 6,400 rpm and 596 lb-ft of torque at 5,100 rpm
LS7: MSD Atomic intake and 105mm Holley throttle body. 1.8 rocker arm ratio
After dialing in the air/fuel and timing, the LS7-headed 427 produced peak numbers of 658 hp at 6,600 rpm and 587 lb-ft of torque at 5,000 rpm.
If you just add a SR cam that's a bump of let's just say 20 hp + vacuum pump + 10 hp and we'll say they used 11.0 compression and you'll use 12.0 or closer to 12.0. +8 hp. So you've just added 38 hp to a baseline of 648 or 658 = 680 to 690 @ the crank. Basic math.The heads choice really doesn't matter as I've listed a 427 factory Ls3 heads making 658 hp with a HR cam same basics as the TFS test.
1) Better cam LLSR
2) More Compression
3) Vacuum pump
All the builds I've listed besides 1Sickengine (6.2 Ls3) would make 600 rwhp with a LLSR and pretty much NOTHING else. Your only asking for around 670 to 690 @ the crank. Don't overthink it! There ARE NO new combinations under the sun. Find one that's close to yours and copy it and add better stuff where needed for more HP. To Easy, simple math.
TFS head test: BTR LS7 STAGE IV CAM : Cam specs are 247/258 112+3 over 600 lift
TFS 245: 102mm FAST LSXR intake with matching 102mm Big Mouth throttle body. 1.7 rocker ratio
The 245-headed 427 produced peak numbers of 648 hp at 6,400 rpm and 596 lb-ft of torque at 5,100 rpm
LS7: MSD Atomic intake and 105mm Holley throttle body. 1.8 rocker arm ratio
After dialing in the air/fuel and timing, the LS7-headed 427 produced peak numbers of 658 hp at 6,600 rpm and 587 lb-ft of torque at 5,000 rpm.
If you just add a SR cam that's a bump of let's just say 20 hp + vacuum pump + 10 hp and we'll say they used 11.0 compression and you'll use 12.0 or closer to 12.0. +8 hp. So you've just added 38 hp to a baseline of 648 or 658 = 680 to 690 @ the crank. Basic math.The heads choice really doesn't matter as I've listed a 427 factory Ls3 heads making 658 hp with a HR cam same basics as the TFS test.
Last edited by Patron; 08-15-2018 at 11:22 PM.
08-15-2018, 11:39 PM
#37
Big Hammer: Yes using the ls3 heads on the larger bore will just potentially let them flow more. I asked mast what my heads would flow on a 4.125 bore and they just said more but wouldn’t tell me how much.
http://speedtalk.com/forum/viewtopic.php?t=8676
https://www.castheads.com/equipment-...ble-cylinders/
08-16-2018, 05:57 AM
#38
TECH Veteran
Can't believe someone just said MORE CFM SELLS HEADS. Wow!! I be telling my buddies at work the exact same thing.
08-16-2018, 09:39 AM
#40
"I wish I could lay out some quick and easy mathematical equations or some simple guidelines to help, but there simply aren’t any," says D. Morgan. "It’s a complex issue, which is why so many people have trouble. The best way to grasp what’s most important is to use what I consider the five most important variables used to tune the induction system."
- Average velocity;
- Individual instantaneous velocities;
- Shape/design (maximize a homogeneous velocity profile over the entire port and at the same time promote efficient flow);
- Rate of velocity change; and
- Airflow.
- *C.Boggs says that most of his customers are professional engine builders who call him to make custom cylinder heads. "Customers who call me tend to call three different shops on a regular basis – we all do high end head work. I can tell who they’ve called by the CFM number they quote," jokes Boggs. "If it’s 20 CFM higher than the laws of physics, then I know who they’ve talked to. Boggs reiterates what other cylinder head specialists have said about comparing flow numbers to a dyno rating. "It’s become a popular way to sell cylinder heads," says Boggs. "Publications have promoted the CFM number too, probably from a little ignorance (we plead the fifth! – Ed). "While it makes sense that a larger CFM number indicates more air flow, and therefore more power, that’s partially true, but it’s not the most important aspect in selecting a good cylinder head." "It’s all air speed," says Boggs. "If you understand basic fluid dynamics (how things flow and what kind of shapes they like), you’ll have well-shaped ports. And if you’ve designed your port to hit the proper target air speed (it’s going to give you a certain size port to hit that speed if you design around the cross-sectional areas), in general, the CFM number should follow that. * Boggs and other cylinder head experts say they need to get as much detail as possible from a customer before they can properly design the port. Everything comes under consideration at that point. "But the CFM number is the last thing I pay attention to," continues Boggs. "If everything else has lined up properly in designing the port, the CFM number should be there. But it’s not the number you design around." Remember: a CFM number is a just a number that someone decided to advertise.