fuel pressure, head bolt torque question

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Jul 29, 2004 | 12:44 AM

69firebird

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From: hurst tx

fuel pressure, head bolt torque question

Hi,
I have a couple questions for you big players

what did you all torque your head studs to? I know that I have herd of some of you over torquing them but how much, and how much total torque are you putting on them? I have standard 12-point ARP studs.

Also what are you guys putting your base fuel pressure at?
thanks
ed

Jul 29, 2004 | 06:00 AM

smokinHawk

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From: Columbus, ohio

last time i torqued them to 80ft-lbs

Jul 29, 2004 | 06:51 AM

TTSSZ

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my f.p. is 65. w/ 55# inj. for 575whp - walbro in tank, kenny bell ext. boster.
went 55# for bigger hp in the future. No prob w/ startup or idel. smells rich at idel.

Quote:

Originally Posted by 69firebird

Jul 29, 2004 | 02:47 PM

MelloYellow

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From: Centrifugal City

Quote:

Originally Posted by smokinHawk

last time i torqued them to 80ft-lbs

Heya SmokinHawk.

You do that with Moly Lube or Engine Oil?
We just hit ours at 70 ft/lbs with Moly and was wondering how far we could push it.

Does higher TQ always mean better or can it start to press the gasket unevenly and can higher TQ result in actually less clamping force when higher but not optimal?

Jul 29, 2004 | 06:09 PM

red ws6 99

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From: Las Cruces, NM

For any bolt or stud you want to use whatever the manufacturer specifies for a lube. The torque they have calculated is based on the thread lube, material of bolt, material of the block, material of head, thread type and pitch, thread engagement, and of course cylinder pressure. For instance, using no lube v.s. a good moly or silicon or telfon lube would mean that if no lube was used 50-70 percent less of the applied torque would actually be translated to clamping force. On modern engines with torque to yield bolts/studs adding more torque will usually yield less clamping force. On bolts that are not torque to yield you may get more clamping force but you are cutting down on bolt life. Basically the calculations are pretty easy but are long,tedious and very situation dependent. Bolt calculations usually take on the order about 10-15 pages of calculations depending on the situation.

69firebird, you want base pressure to be as low as possible with the injector duty cycle not exceeding 80% (or if you are brave not exceeding 80% for too long). Injectors will flow more with higher pressure (up to a point) and pump will flow less as the pressure increases. So its fine line on making sure you don't go lean, don't max out the injector or the pump. If you are using large injectors then the lower pressure will give better idle fueling.

Gary

Jul 30, 2004 | 06:40 AM

smokinHawk

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From: Columbus, ohio

last time i torqued them down was with motor oils, so i guess that was in the specs (probably my post was a litle misleading) i think its 70 with the moly and 80 with oil

once i torqued a head down to about 150-200ft lbs, the silly torque wrench wasnt working right and i just keep on cranking, thought i was getting week, it was getting harder and harder, but the wrench wouldnt click, then it got easy again, and i was like ok i just got pass some friction zone, next crank.....SNAP there goes the stud.

Thanks Mike Brown for your crappy torque wrench!

(but thanks for letting me use your garage.)
Reckless was helping me with the HG swap and he ended up getting the stud out of the block.....thanks Todd.

Jul 30, 2004 | 06:50 AM

2001WS6Vert

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From: Cincinnati, Ohio

I called ARP when I did mine because the 70lbs. just sounded too light for a boosted car. They said to do the 70lbs. with moly lube which is what I did. I still wonder if I should maybe retorque them a little tighter one day, maybe to 80 lbs.