Boost Limit on 4 bolt heads
09-29-2014, 10:34 PM
#41
I'll verify those tomorrow. I didn't believe the darts were any thicker that 317s.
09-30-2014, 11:23 AM
#42
This thread has some really useful info. I planned to only push my combo to 20 lbs. because I thought that's when people started lifting heads...now I know. Everything on my build has been done to handle 1000 WHP and then some, now I wont be so hesitant to push things a little harder.
09-30-2014, 01:06 PM
#44
10-08-2014, 12:17 PM
#45
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Ok so if a Dart head will do just fine on a 6.0 block as long as the tune is right. Would you guys say that the Dart head is better to go with then the 317?
11-04-2014, 08:20 PM
#46
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im running 317s with stock size studs. e85, 26psi, 20* timing. went 5.4@126mph with 1.25 60ft last weekend. Going to turn it up around 28psi this weekend and see what happens. Car is 3500-3600 with me in it
11-05-2014, 04:48 AM
#48
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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!
Something to consider is how and what lifts; what happens the head lifts between studs, not the stud stretching as must people think when conversation is brought up about the subject.
Fact; ARP studs will hold a lot more boost than must heads and cylinder blocks ever will.
Another misconception is the block, aluminum blocks lifts just like the head
by stretching upwards at the stud area which is really the reverse of what happens with the head.
When the block stretches up, the block area between the studs looses it's head gasket pressure leak starts there, will remain till you change head gasket but will come back as soon is boosted beyond casting capability, (this means will keep happening)
Those why some of us prefer cast iron blocks for boost, however a 4.6 and 5.3 liter motor will take a lot more for longer due to smaller piston diameter which don't load the heads and block to their limit as soon.
Here's how to know whether block is stretching or head is lifting;
If leak appears above the head gasket or between gasket and head and the lower area of gasket is clean, THE HEAD IS LIFTING.
If leak "or black exhaust path trace" is at lower area of head gasket only, THE BLOCK IS STRETCHING UP at stud area, (not the stud) If stud lifts black exhaust path will surround area immediately around stud, I personally NEVER seen this.
If you have boosted enough to encounter all the limits then;
You would know that's possible to stretch the block and lift the head all at the same time when black exhaust path marks are present both above and below on head gasket.
The head usually lifts at outer area rite in the middle between studs sense the LS engine heads tapered-out on the out side away from best structural area which is the inner and center of head where taller structural valve cover and rocker area is.
The piston cylinder positions outside the center of head placing combustion chamber outside the center tours heads weak end, other weakening factor for LS head is the spark plug hole at heads weakest taper area and center between studs, presence of the spark plug does not help at all either, it gladly lifts up for the ride.
This next fact may be surprising but happened to me so how I know, inner side of head lifts as well with enough boost though not as prom as the out side, I seen leaking tours the center as well.
So why 6 bolts heads and blocks, the inner or six bolt is very important as well when you want to make sure.
Hopefully these goes to save some active soul some work and $ as well as unnecessary expending on 1/2 inch or 12 MM studs and help clear the air as to what lifts, why and how.
If this is all blah blah to nobody same is lacking enough tools, cash, will and wisdom even with enough beer.
thanks for the insightful and informative post!! you really helped me. I'm looking at an upgrade on an LS6 TTiX turbo car. currently running 800 rwhp on 17.5 psi, but heavily meth dependent
I'm looking to upgrade as follows (all in)
haltech s2000 with flex fuel and 8 channel egt to help with tuning
magnafuel 4303 + intank + ecs tank bulkhead (maybe upgrade to 450 internal pump if I can make it work)
FIC bosche 127 injectors
having the haltech run the alchy injection and considering the ECS direct port to help with fuel distribution
engine build
4.8 with stock crank, lunati h beam rods, and diamond coated pistons
AFR 225 heads (already on car)
stock ls6 intake
9.5-1 or so compression (many recommend higher but I'm looking for high boost!!)
dr phil cam (specs unknown, but I like the way it runs)
open to other cam recommendations, this cam is designed for a 346
.82 exh turbine housing + champion 3" downpipes
currently have borla 2.5 stinger, may just keep that and run cut outs but I'll likely go with a flapper in the tip (c6 exh tips) for quiet crooze
I drive this car whenever possible on the street
3.42 gear diff with an RPM 4lL65E Lvl 5 (already in car)
looking for a good paddle shift or bump shifter that will provide better control of the tranny and likely a tranny retune
the one downside to the haltech is it doesn't have a tranny control
11-05-2014, 08:37 AM
#49
I am going to try a set of 823 heads that I had in the garage from a different build this season. Biggest concern is that they have been decked a lot (.060). But the curiosity in me has to see how it goes.
if it doesn't work Ill go right back to the 317s
11-06-2014, 07:22 AM
#50
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We were on the dyno last week. 31 psi, 22 degrees of timing, on C16. Wasn't pushing any water at all. It's a 4 bolt set up but I am running the ARP CA625 studs. Hitting the track this weekend to see what it can do.
11-11-2014, 04:39 PM
#54
I know for a fact my buddys 6.0 block 408 with stock LSA heads and stock size 11mm ARP head studs is seeing 27-28psi no issues on race gas. GT4788. Waste gate pinned shut on the big end. Made around 908whp been 8.40s
The GT47 exhaust wheel is to small for his 408 so over the winter its getting the GT55 wheel then back at it. Hopefully 1100whp or so at same boost level with better flowing wheel
The GT47 exhaust wheel is to small for his 408 so over the winter its getting the GT55 wheel then back at it. Hopefully 1100whp or so at same boost level with better flowing wheel
11-11-2014, 04:44 PM
#55
I run 20psi on pump and meth and it doesn't lift the heads...ebay head studs too
11-11-2014, 06:31 PM
#56
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I'm running ported stock chamber LSA heads, ARP CA625 studs and on methanol for fuel. not sure how much boost it will take but shooting for 4.5x's in a 2800lb car with gt5588
11-11-2014, 08:49 PM
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Been to 23lbs on standard arps/ls9 gasket, with my stock l33 stock 799/springs 850whp. Plan on 23-25lbs and a 100 hit on my forged iron 5.3 with thicker deck afr 210s same studs/gaskets. should be well over 1000whp/tq
pt7675 .96 billet both setups
pt7675 .96 billet both setups
