Boost Limit on 4 bolt heads
Boost doesn't mean anything, neither does HP
Cylinder pressure (tq) is what is driving the head off.
control where and how torque is delivered and you are in good shape
Most problems stem from tuning issues whether it be detonation which creates insane cylinder pressure or it be boost delivery and timing
Cylinder pressure (tq) is what is driving the head off.
control where and how torque is delivered and you are in good shape
Most problems stem from tuning issues whether it be detonation which creates insane cylinder pressure or it be boost delivery and timing
TECH Fanatic
Joined: Mar 2011
Posts: 1,916
Likes: 8
From: Statesville, NC
like a supra running 45psi with no head lifting issues. Keep things in the upper rpm?
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
Ive used close to 40psi on a Subaru before with no problems, but it used 14mm studs.
The CA625's can be bought for around $700 though.
Yes it's still expensive, but in the overall scheme of things not that much really. Certainly cheaper than 1/2" studs and supposed to offer similar clamping ability
Here is a link to them. You will see why few people run them in your average turbo builds when you see the price.
http://www.coloradospeed.com/arp-cyl...6-p-24550.html
http://www.coloradospeed.com/arp-cyl...6-p-24550.html
$550 in 1/2" studs and the machine work to tap and thread the holes.
Totaly agree. I only did it because i was building a brand new motor from the ground up and whats another 550 at this point, got the main caps pinned too. Im going to push it to 1200rwhp atleast.
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Boost doesn't mean anything, neither does HP
Cylinder pressure (tq) is what is driving the head off.
control where and how torque is delivered and you are in good shape
Most problems stem from tuning issues whether it be detonation which creates insane cylinder pressure or it be boost delivery and timing
Cylinder pressure (tq) is what is driving the head off.
control where and how torque is delivered and you are in good shape
Most problems stem from tuning issues whether it be detonation which creates insane cylinder pressure or it be boost delivery and timing
Boost is just a number.
If anyone tries to tell you a certain amount of boost will blow your engine up or lift your heads, they don't understand how physics works.
You might have a 5.3L engine that needs 30psi to make 1000hp, whereas a 408 might only need 20psi to make 1000hp. Are you going to say that the 5.3 is going to lift the heads before the 408 because it needs more boost to make the same amount of HP? No!
Just like rotary said, it's torque production(cylinder pressure I.E. VE) and at what RPM it occurs that will lift the heads.
I am running 25-26psi and making well north of 1000rwhp with 4 bolt LSA heads, LS9 gaskets, stock diameter studs(custom aged) and an iron block.
My engine doesn't make peak torque until 6000rpm though, and this eases cylinder pressure at lower RPM's where if my engine made more torque at a lower RPM(I.E. more cylinder pressure) it would have a higher probability of lifting the heads.
Boost is a measurement of efficiency and how efficient your engine is in consuming/demanding air mass.
Factory heads hold a lot of boost specially the lsa /ls9 castings. the shorter the stroke and the narrower the piston diameter the more boost allowance you will have with the OEM cylinder block and heads.
Worse heads for boost are Dart pro1 ls1/ls2 with 4" stroke they lift like an elevator, ouch Dart!
TECH Fanatic
Joined: Mar 2011
Posts: 1,916
Likes: 8
From: Statesville, NC
Look at Shawns mustang 5.3 record he just set. L33 making nearly 42psi with a gt55-88 and Chinese head studs with stock heads. Pure meth for fuel but that said, the heads will stay down with MEGA boost pressure if other factors are correct.
plenty of people seem to be running 800-900 wheel on 317s with no issue. are people just refering to darts being a bad choice for 1200+hp?
I went 162 with my 317's recently but came across a killer deal on some Trick Flow GenX 225's and picked those up. Converting to 1/2 head studs as well. Mains are already pinned with ARP hardware.
I want to lean on this combo hard to see if I can squeeze 175 out the back door with the stock crank.
Yes - Dart's have a bad reputation as an upgrade from stock heads. If you had no heads to start your build I would personally take a Dart head over a stock head. But obviously a trick flow head over a dart head etc...
I went 162 with my 317's recently but came across a killer deal on some Trick Flow GenX 225's and picked those up. Converting to 1/2 head studs as well. Mains are already pinned with ARP hardware.
I want to lean on this combo hard to see if I can squeeze 175 out the back door with the stock crank.
I went 162 with my 317's recently but came across a killer deal on some Trick Flow GenX 225's and picked those up. Converting to 1/2 head studs as well. Mains are already pinned with ARP hardware.
I want to lean on this combo hard to see if I can squeeze 175 out the back door with the stock crank.
Simple Eagle Rod ARP2000 rod bolt, Wiesco Piston, Stock Crank 370 Shorty.
Custom Comp Cam
Comp Magnum Rockers
Just switched to the Trick Flow 225 Heads (no times with these yet)
Pro Flo
Twin 70's
A/W IC
E85
Twin MagnaFuel 4303's
Bosch 1600 High Impedance
Holley HP
Reid Case Billet Glide
Neal Chance Converter
Custom Comp Cam
Comp Magnum Rockers
Just switched to the Trick Flow 225 Heads (no times with these yet)
Pro Flo
Twin 70's
A/W IC
E85
Twin MagnaFuel 4303's
Bosch 1600 High Impedance
Holley HP
Reid Case Billet Glide
Neal Chance Converter
dang. i got a great deal on dart pro1 that i wanted to use on my 408.
i was under the impression they were an upgrade above stock castings.
i have a bunch of sets of 317s. but didnt really want to use em on something i have planned to run 25-30psi.
i was under the impression they were an upgrade above stock castings.
i have a bunch of sets of 317s. but didnt really want to use em on something i have planned to run 25-30psi.
stock heads are .300, darts are .500 or .550 i believe on the deck thickness. tfs/afr are like .650 and .750 i believe. I was pushing 23lbs on stock heads making peak tq at like 4500 and never lifted the heads. So Darts should do a bit better then stockers.