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Discussion Starter · #1 ·
Anyone experience a loss in boost when installing XR heads ? My 2.6 KB with reg stage 2 PI head made 22 to 23 normal weather and almost 24 in cooler weather. (10lb lower, 3.5 upper). With XR head stage 2, it made 20 psi. Prob going to pully down to a 3.25. Do I need to get a different lenght belt for the 3.25 ?

Pretty happy with dyno #'s. Weather was horrible, hot and very humid. Conservative 15 deg timing, C16 and 11.8 A/F 675/696. Going to do some passes first then turn the boost up to 24 and up the timing to 18 deg. Figuring I will be happy with 720 to 725 since most guys with stage 3 and laying down like 735 to 750. :smt017
 

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street truck
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Anyone experience a loss in boost when installing XR heads ? My 2.6 KB with reg stage 2 PI head made 22 to 23 normal weather and almost 24 in cooler weather. (10lb lower, 3.5 upper). With XR head stage 2, it made 20 psi. Prob going to pully down to a 3.25. Do I need to get a different lenght belt for the 3.25 ?

Pretty happy with dyno #'s. Weather was horrible, hot and very humid. Conservative 15 deg timing, C16 and 11.8 A/F 675/696. Going to do some passes first then turn the boost up to 24 and up the timing to 18 deg. Figuring I will be happy with 720 to 725 since most guys with stage 3 and laying down like 735 to 750. :smt017
I can't say that I have but I'd expect to see a boost drop with that type of swap. Those XR heads move some serious air! :smt023
 

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Good meeting you Tuesday.

I'd say the loss is normal. My old setup with the R heads made 22psi with the 10lb/3.5 combo. We only saw 21psi the other day with the same pullies. ALOT more then just the heads changed on my setup though so it wouldnt be anything to base a comparison off of. BTW, I use the same belt between the 3.5 upper and the 3.25
 

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Discussion Starter · #5 ·
Good meeting you Tuesday.

I'd say the loss is normal. My old setup with the R heads made 22psi with the 10lb/3.5 combo. We only say 21psi the other day with the same pullies. ALOT more then just the heads changed on my setup though so it wouldnt be anything to base a comparison off of. BTW, I use the same belt between the 3.5 upper and the 3.25

Thanks man, nice to meet you as well. Hang in there man, things will work out ! Don't jump ship just yet, you have a swweet looking truck there.:smt023
 

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Boost Freak!!!!!!!!
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Between the heat and better flowing heads the loss in boost is normal. Loss in boost due to better flowing heads, doesn't mean a loss in HP. If your moving more air you should be making more HP.
 

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Fat Bastad
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Same pulley ratio and a drop in boost means only one thing. Better flow!

Jim
:bigtu If Jim says it...It's the gospel and you can take that to the bank.

Your loss of boost reading doesn't mean a loss of power...That's a very common misconception so don't be fooled. It's better to make the same power at less boost...cooler intake air temps=healthier for the motor because is reduces your chance of detonation occuring.


Roach
 

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Slower than Jim
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You should be right where I am at. I make just shy of 16lbs with a 10lb lower and a 3.75 upper, so I figure I am gonna have to go 3 inch on top for 22lbs which is where I wanna be at the moment. I am just wondering where some of these trucks here are getting the big numbers from as mine has not had any impressive dyno numbers yet. I only have a 12 degree street tune at the moment and it would not put down 600. But it does run 7.30s at full weight , so I figure it has to be making a little power...Gotta get it making some power as to not let Jim school bus me at sts...hehe
 

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E85 POWERED L
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As these guys have said the drop in boost is good. I repullied my tuck before the install so Im not sure how much mine would have lost. But I replied to your pm:bigtu
 

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But it does run 7.30s at full weight , so I figure it has to be making a little power...Gotta get it making some power as to not let Jim school bus me at sts...hehe
LOL!!! You better figure a way to drop well over a second from your 1/8 mile times, then. Good luck to you, and I look forward to seeing you at the STS!:bigtu
 

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Mr. Crossfire
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Someone's upgraded for Spookfest. Why didnt you upgrade the cams?
 

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Slower than Jim
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LOL!!! You better figure a way to drop well over a second from your 1/8 mile times, then. Good luck to you, and I look forward to seeing you at the STS!:bigtu
Workin on it man, I have not even got a race tune for this thing yet and still have a nitrous kit if need be. I also figure I got about 300lbs - 400lbs that I can take out of the thing without doing anything drastic. I just wanna at least look like I am trying to keep up..looking running it in the 100 degree South Carolina heat does nothing for performance either..Look forward to meeting you and everyone else this year, be nice to put faces with names..
 

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Discussion Starter · #15 ·
Someone's upgraded for Spookfest. Why didnt you upgrade the cams?
Gunna try and be one of very few Lightnings to run 10 flat or (9.99) with a stage 2 and no juice. Trying to cut 400 lbs out of this beast but not the AC or heater. Keeping it street even the stock drivers seat. It's going to be tough but I will give it a try.
 

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Slower than Jim
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Upgrade does not always mean bigger...
 
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