Smallest bore for ls7 heads?
Smallest bore for ls7 heads? Looking into changing my heads and was curious if a ls7 will work on a 4.060 bore. Is it possible to go a size smaller on the intake valve?
Originally Posted by strokedls1
Looking into changing my heads and was curious if a ls7 will work on a 4.060 bore. Is it possible to go a size smaller on the intake valve?
Man you normally know these answers.
From what I have "read" 4.060 is the smallest.
However I have seen a few 346 cubic inch 3.898 bore LS1's with the 4.125 bore AFR 225 heads on top.
There are very few combo's I can even picture that would make puting the LS7 heads on worth it.
Their runners are very very big for a 383 or smaller motor.
Negative Jason. Nominal bore size is 4.100". The exhaust valves are very close to scrapping the bores on a 4.060" setup. The valve placement in the LS7 is the reason. They're moved to different locations than LS1 heads. I have some unported LS7 heads that the guides could be moved to clear a smaller bore. A bit of work yes, but it would make an exceptional small bore LS7 setup.
Call me at the shop and I can explain better.
Richard
Call me at the shop and I can explain better.
Richard
Originally Posted by Richard@WCCH
Negative Jason. Nominal bore size is 4.100". The exhaust valves are very close to scrapping the bores on a 4.060" setup. The valve placement in the LS7 is the reason. They're moved to different locations than LS1 heads. I have some unported LS7 heads that the guides could be moved to clear a smaller bore. A bit of work yes, but it would make an exceptional small bore LS7 setup.
Call me at the shop and I can explain better.
Richard
Call me at the shop and I can explain better.
Richard
I am up in the air about these L92 heads with the composite gm intake. I know they will work fine. I do have some offset bores so clearance does play a big roll to me. Thanks for the replies guys. I figured the vavles would be too tight. Hopefully the L92 heads and intake pan out.
Originally Posted by Richard@WCCH
Negative Jason. Nominal bore size is 4.100". The exhaust valves are very close to scrapping the bores on a 4.060" setup. The valve placement in the LS7 is the reason. They're moved to different locations than LS1 heads. I have some unported LS7 heads that the guides could be moved to clear a smaller bore. A bit of work yes, but it would make an exceptional small bore LS7 setup.
Call me at the shop and I can explain better.
Richard
Call me at the shop and I can explain better.
Richard
Richard .... I had a discussion with I believe ETP about this awhile ago, and they said that the valve is very close to scraping, but it would work on a 4.060" (absolute minimum tho). Now, I personally wouldn't run an LS7 head on anything below a 4.100", but that doesn't mean it can't be done. If the valves did hit on a 4.060", then that would be a different story. Obviously you would know more about this then I would, I'm just going by what I've heard from other head manufacturers.
The block I checked the heads on was a std. bore LS2 block. We checked each chambers valve/bore fit. On two bores the exhaust valves scraped the bore. On two other bores, the exhaust valves hit the top edge and would not fully open. A 4.060" bore would yield an additional .030" of valve/bore clearance. In the case of the two cylinders that had valves that hit, you would have less than .030". This is still not a safe amount on a hot, running engine in my opinion. Others may disagree. Static clearance doesn't guarantee the parts won't hit once the engine is run.
Richard
Richard
Originally Posted by xphantomws6x
Richard .... I had a discussion with I believe ETP about this awhile ago, and they said that the valve is very close to scraping, but it would work on a 4.060" (absolute minimum tho). Now, I personally wouldn't run an LS7 head on anything below a 4.100", but that doesn't mean it can't be done. If the valves did hit on a 4.060", then that would be a different story. Obviously you would know more about this then I would, I'm just going by what I've heard from other head manufacturers.
Trending Topics
Originally Posted by Richard@WCCH
The block I checked the heads on was a std. bore LS2 block. We checked each chambers valve/bore fit. On two bores the exhaust valves scraped the bore. On two other bores, the exhaust valves hit the top edge and would not fully open. A 4.060" bore would yield an additional .030" of valve/bore clearance. In the case of the two cylinders that had valves that hit, you would have less than .030". This is still not a safe amount on a hot, running engine in my opinion. Others may disagree. Static clearance doesn't guarantee the parts won't hit once the engine is run.
Richard
Richard
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Topdon ONE vs. Artidiag 800 BT2: Which is the Diagnostic Tablet For You?
Pouria Savadkouei
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
8 Second Club
Joined: May 2002
Posts: 1,043
Likes: 0
From: Toronto
How about ETP's small bore LS7 head that is made for a 4.00 bore?
http://www.etheads.com/mainpage.htm
Cylinder Head: G III LS7 Application: Street / Race
Port Volume: 250cc Chamber Volume: 35cc to 72cc
Test Bore: 4.000" Test Pressure: 28.00" Water
Intake Valve: 2.125" Exhaust Valve: 1.600"
Valve Lift Intake Exhaust Valve Lift
.100" 73 56 .100"
.200" 154 110 .200"
.300" 236 166 .300"
.400" 287 199 .400"
.500" 321 214 .500"
.550" 336 219 .550"
.600" 345 222 .600"
.650" 350 226 .650"
Exhaust to Intake Flow Ratio 68%
Jobber Price: $2,850.00 Retail Price: $3,199.99
http://www.etheads.com/mainpage.htm
Cylinder Head: G III LS7 Application: Street / Race
Port Volume: 250cc Chamber Volume: 35cc to 72cc
Test Bore: 4.000" Test Pressure: 28.00" Water
Intake Valve: 2.125" Exhaust Valve: 1.600"
Valve Lift Intake Exhaust Valve Lift
.100" 73 56 .100"
.200" 154 110 .200"
.300" 236 166 .300"
.400" 287 199 .400"
.500" 321 214 .500"
.550" 336 219 .550"
.600" 345 222 .600"
.650" 350 226 .650"
Exhaust to Intake Flow Ratio 68%
Jobber Price: $2,850.00 Retail Price: $3,199.99
The cost and wait time on the ETP stuff is a definite cancellation for it. I have dealt with the lies and bs of head delivery before and won't go that route again. I don't know about the valve placement on the l92, but I would venture to say no on a 4" bore. The intake valve size was 2.150 and the ls7 is 2.200. If the ls7 doesn't really fit at 4.060, then the l92 is gonna be in the same close proximity for a 4.00" bore.
Originally Posted by strokedls1
The cost and wait time on the ETP stuff is a definite cancellation for it. I have dealt with the lies and bs of head delivery before and won't go that route again. I don't know about the valve placement on the l92, but I would venture to say no on a 4" bore. The intake valve size was 2.150 and the ls7 is 2.200. If the ls7 doesn't really fit at 4.060, then the l92 is gonna be in the same close proximity for a 4.00" bore.
Stay tuned,
Richard
