LS7 heads or ls3 heads
#23
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In theory and implementation its a waste. That is why TSP makes a small bore ls7 head and a few others.
Most of the people that want to modify the stock ls7 heads to fit the smaller bore wind up using just as much money as well as waiting quite a while vs just buying a much better designed aftermarket small bore head. Trying to put them on as is is also not what i would ever advise.
Its exactly the same as putting the smaller seat in the ls3 head and using them on an ls1 etc. alot of time and money wasted for little return vs an aftermarket head.
Ive put ls7 heads on an ls3 to check even. The amount of bore size there isnt proves enough to me. Even if they were less $$ and easier to get, its still not a goof idea. Plus youre already looking at doing new exhaust valves and possibly guides as well before you even bolt them on so its moot after that.
Most of the people that want to modify the stock ls7 heads to fit the smaller bore wind up using just as much money as well as waiting quite a while vs just buying a much better designed aftermarket small bore head. Trying to put them on as is is also not what i would ever advise.
Its exactly the same as putting the smaller seat in the ls3 head and using them on an ls1 etc. alot of time and money wasted for little return vs an aftermarket head.
Ive put ls7 heads on an ls3 to check even. The amount of bore size there isnt proves enough to me. Even if they were less $$ and easier to get, its still not a goof idea. Plus youre already looking at doing new exhaust valves and possibly guides as well before you even bolt them on so its moot after that.
#24
Read of a few doing it either way, aftermark and or made. Better head was what was taken exhaust seems a tad shrounded yet working camming would negate the negatives. The word on the web is 20hp vs a factory ported ls3.
#27
Something to read.
https://www.yellowbullet.com/forum/s....php?t=2564993
Normal port finish vs Burr finish.
http://speierracingheads.com/uploads...ynoinfo2_1.pdf
https://www.yellowbullet.com/forum/s....php?t=2564993
Normal port finish vs Burr finish.
http://speierracingheads.com/uploads...ynoinfo2_1.pdf
#28
TECH Apprentice
iTrader: (3)
I built a LS3 4.070" block and put both factory LS7 and the as-cast LSX-LS7 heads on it. The intake valves clear by a mile since the valve location is different vs. a LS3, but the exhaust valve is what gets close. To give myself a little more clearance and reduce shrouding, I turned the new one-piece stainless valves down on the lathe from 1.61" to 1.59". Didn't cost me any more money that if I had put a set of LS3 heads on it.
Oh yeah, the heads were free to me from an LSX454, so i couldn't pass them up, along with the cam. Not to mention I got an LS7 intake, fuel rail AND injectors of CL for $160. I don't think I could find an LS3 intake and injectors for that price.
#29
ModSquad
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I wouldn't go so far as to say it's "a waste" to run a LS7 head on a smaller-ish bore, it will just "waste" a few more dollars in the cost of the heads.
I built a LS3 4.070" block and put both factory LS7 and the as-cast LSX-LS7 heads on it. The intake valves clear by a mile since the valve location is different vs. a LS3, but the exhaust valve is what gets close. To give myself a little more clearance and reduce shrouding, I turned the new one-piece stainless valves down on the lathe from 1.61" to 1.59". Didn't cost me any more money that if I had put a set of LS3 heads on it.
Oh yeah, the heads were free to me from an LSX454, so i couldn't pass them up, along with the cam. Not to mention I got an LS7 intake, fuel rail AND injectors of CL for $160. I don't think I could find an LS3 intake and injectors for that price.
I built a LS3 4.070" block and put both factory LS7 and the as-cast LSX-LS7 heads on it. The intake valves clear by a mile since the valve location is different vs. a LS3, but the exhaust valve is what gets close. To give myself a little more clearance and reduce shrouding, I turned the new one-piece stainless valves down on the lathe from 1.61" to 1.59". Didn't cost me any more money that if I had put a set of LS3 heads on it.
Oh yeah, the heads were free to me from an LSX454, so i couldn't pass them up, along with the cam. Not to mention I got an LS7 intake, fuel rail AND injectors of CL for $160. I don't think I could find an LS3 intake and injectors for that price.
I use them on my 6liter builds with 823 heads to give me more room on intake side, for unshrouding. For what you did, these would work great for LS7 heads, which as you said, push the exhaust valve way over and shroud it. No intake alignment issues. Pretty trick.
#30
TECH Senior Member
Offset dowels for valving clearancing heads is ingenius! Clearance gained via a little sideways displacement! And who would know by appearances?
#31
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The main issue is the stock exhaust valves. They like to break. So youre out quite a bit there to begin with, and not everyone has a lathe to do that. So for the real world consumer, reading this on the internet and thinking its so simple, its VERY misleading. And for them, a waste.
Do you have any airflow numbers from either or power difference numbers? Until then its all theoretical conjecture that definitely doesnt point to the ls7 head on a small bore to be a good idea.
Do you have any airflow numbers from either or power difference numbers? Until then its all theoretical conjecture that definitely doesnt point to the ls7 head on a small bore to be a good idea.
#32
Guy on YB posted flow result of a ported Ls3 head and custom Ls7 head by major porters (small bore). Ls7 won thru out the lift with a smaller port.
Even these guys do a Ls7 head for a smaller bore.
www.not-a-sponsor.com
Even these guys do a Ls7 head for a smaller bore.
www.not-a-sponsor.com
Last edited by Smokey B; 02-27-2019 at 12:22 AM.
#33
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I have a set of Cnc LS7 heads with a smaller exh. Valve 1.560 vs 1.610, I acquired these in a deal of a bunch of parts and the seller told me they were now set up for smaller 4.065 bore, without clearance issues. Having read the comments here by some this is not a good idea?
#35
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Originally Posted by 64post
I have a set of Cnc LS7 heads with a smaller exh. Valve 1.560 vs 1.610, I acquired these in a deal of a bunch of parts and the seller told me they were now set up for smaller 4.065 bore, without clearance issues. Having read the comments here by some this is not a good idea?
#36
TECH Apprentice
iTrader: (3)
The main issue is the stock exhaust valves. They like to break. So youre out quite a bit there to begin with, and not everyone has a lathe to do that. So for the real world consumer, reading this on the internet and thinking its so simple, its VERY misleading. And for them, a waste.
Do you have any airflow numbers from either or power difference numbers? Until then its all theoretical conjecture that definitely doesnt point to the ls7 head on a small bore to be a good idea.
Do you have any airflow numbers from either or power difference numbers? Until then its all theoretical conjecture that definitely doesnt point to the ls7 head on a small bore to be a good idea.
First, the cost of a set of NEW stainless vales from SI (part number SI-1137) was $99.89 for 1.615" LS7 exhaust valves. So not what I would consider "quite a bit" by any means.
Second, you don't HAVE to machine the valves down in order for the LS7 head to be placed on a 4.070" bore and have ample clearance. Ideal, maybe not, but will it break any parts, no.
Third, it really is THAT simple to put LS7 heads on a 4.070" bore. No doubt about it. There is about .030" clearance to the bore and the valve notches in MOST LS3 pistons will clear MOST cams that street cars would be running. Definitely NOT misleading and far from being a "waste" in my opinion.
Fourth, if you have plans of a stroker in the future, the LS7 is a great head to start with.
I'm NOT saying a LS3 head is bad, or a worse choice. It's all about what the owner has in mind and what the BIG picture is. Is the LS7 head the right choice for everyone, no. Is it a BAD choice to put them on a 4.070" bore, I really don't think so.
Do I have power numbers of the two heads on the same engine? No, I don't have the luxury of acquiring all the parts, money and time to do so. But, I will say my "baby" LS7 runs really well for what it is. I will update with track times, dyno numbers, etc. once I get them. All I have to go by at the moment is the injector flow, pulse width, RPM, MAF g/sec, etc. from HP Tuner logs and it all tells me that I'm around 600HP at the flywheel. Not bad for a 6.2 with a 236/246 @ .050" cam and only 10.4:1 compression.
Cole
#37
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Misinformation? No. Difference of opinion? Yes.
You can justify it any way you want, but real world numbers would be a seller. As in flow or dyno or even track.
Plus youre into a set of ls7 heads for quite a bit to start with unless you "have them lying around" or the like. So still...a moot point.
You can justify it any way you want, but real world numbers would be a seller. As in flow or dyno or even track.
Plus youre into a set of ls7 heads for quite a bit to start with unless you "have them lying around" or the like. So still...a moot point.
#39
From what i've gathered.
Ls7 heads sold as 250 cc bare as cast. Darin Morgan 275 cc runner after being done, runner after being done looks at minimal a hair off from being as cast. Hand port work in the bowls, short side rad., with matching runners 2.20 valve.
Both test bores used .060-0.80
Huge factory Ls3 runner 268cc low laying placement: 2.165/1.6 FED stg1 Chris Frank
299/212@.400
363/236@.600
371/247@.900
Morgan Ls7 smaller Port CSA but 275cc runner 2.20 /1.55 no pipe
300/191@.400
360/219@.600
379/222.@.700
Mast STR8 head *port face measures* 2.275h x 1.635w
FED stg1 Ls3* 2.559 x 1.260
D*Ls7 heads* 2.244 x 1.259
Custom 12degree Ls3* 2.68 x 1.28
Lsx CT raw cast head * 1.95 x 1.3 from Rocko...Head of the Lsx Division
CHI 3Vpro* 2.12598 x 1.65354 - Yates D3 Cylinder Head Intake Port Dimensions: 2.175" x 1.650"
Darin Morgan Programs for Ls3 and LS7 heads
http://speierracingheads.com/gm-vls3.html
http://higginsraceheads.com.au/heads/hrd-6-bolt/
Mast
https://www.mastmotorsports.com/coll...oducts/ls7-265
https://www.mastmotorsports.com/coll...oducts/ls3-255
https://www.mastmotorsports.com/coll...ium-bore-4-000
Both test bores used .060-0.80
Huge factory Ls3 runner 268cc low laying placement: 2.165/1.6 FED stg1 Chris Frank
299/212@.400
363/236@.600
371/247@.900
Morgan Ls7 smaller Port CSA but 275cc runner 2.20 /1.55 no pipe
300/191@.400
360/219@.600
379/222.@.700
Mast STR8 head *port face measures* 2.275h x 1.635w
FED stg1 Ls3* 2.559 x 1.260
D*Ls7 heads* 2.244 x 1.259
Custom 12degree Ls3* 2.68 x 1.28
Lsx CT raw cast head * 1.95 x 1.3 from Rocko...Head of the Lsx Division
CHI 3Vpro* 2.12598 x 1.65354 - Yates D3 Cylinder Head Intake Port Dimensions: 2.175" x 1.650"
Darin Morgan Programs for Ls3 and LS7 heads
http://speierracingheads.com/gm-vls3.html
http://higginsraceheads.com.au/heads/hrd-6-bolt/
Mast
https://www.mastmotorsports.com/coll...oducts/ls7-265
https://www.mastmotorsports.com/coll...oducts/ls3-255
https://www.mastmotorsports.com/coll...ium-bore-4-000
Last edited by Smokey B; 03-01-2019 at 11:59 AM.
#40
TECH Senior Member
iTrader: (4)
The LS3 head is definitely the hotrodders head as Hammer said.
Hard to beat the 750+hp potential, quality and value of a set of Darin Morgan's CNC ported LS3 heads w/Manley dual springs good to .660 lift for ~$1,000 if you have cores. They are inexpensive enough to use in daily driver friendly builds with small cams and capable of serious power with big cams for more race oriented builds.
Exactly as I received mine
Hard to beat the 750+hp potential, quality and value of a set of Darin Morgan's CNC ported LS3 heads w/Manley dual springs good to .660 lift for ~$1,000 if you have cores. They are inexpensive enough to use in daily driver friendly builds with small cams and capable of serious power with big cams for more race oriented builds.
Exactly as I received mine