Low boost due to porting?? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 06-04-2007, 10:22 PM   #1
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Default Low boost due to porting??

i have a 94 ssei
i just rebuilt the entire motor, gasket matched the heads to the intake and the ported exhaust manifolds, i also ported the intake extensivly , before i rebuilt it, i ran about 10psi but now i only get 7-8.5 (autometerprocomp guage) and i even have a 2.5" pulley on it
i have a aem wideband which reads 11.0 with my meth on
i scan my car everytime i drive it and i have 0 kr and about 18 degrees of timing advance

any help would be great
thanks
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Old 06-04-2007, 10:25 PM   #2
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you were probably boost stacking before the rebuild

does it feel more powerful?
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Old 06-04-2007, 10:40 PM   #3
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it feels like i gained 50 horse


i think i may install a smaller pulley and my afc once again to get back to 10+ psi
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Old 06-04-2007, 10:50 PM   #4
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50? Wanna do mine?

I agree, you are flowing better. Boost is kinda a measure of air you're not using. You are still moving as much air, and more is getting into the cylinders. Good stuff.
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Old 06-04-2007, 11:28 PM   #5
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0 KR and 18* advance? I wouldn't worry about a thing. lol As stated, you're flowing better...which is only expected after what you've done. It'* common to see a drop in boost in that case.
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Old 06-05-2007, 12:28 AM   #6
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If you really GASKET matched, your port velocity may be suffering. While I agree with the loss of boost reasons stated above, you may have over-ported. I'd strongly suggest a cam or higher ratio rockers at this point.
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Old 06-05-2007, 10:47 PM   #7
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i actually ported to one sharpe line or 1/16 to the inside, sos not to get carried away,

i put my other pulley on its a 2.1" from pulley boys and tuned with my afc and my air/ fuel is at 10.9- 11.3 with 18 degrees of advance , 0 knock retard, and my blower only still puts out 10-11 psi

the performance is great the power is right there all the time but the low boost numbers still have me concerned
thanks again
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Old 06-05-2007, 10:52 PM   #8
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2.1 on a 94 with only the mods listed?

You're creating tons of heat for no benefit. That'* WAY too small of a pulley without the supporting mods.
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Old 06-05-2007, 11:36 PM   #9
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actally i have lots of stuff done to the motor
complete underdrive pulley kit - custom made
160 degree t-stat
custom ordered bosch 38lb injectors
ported intake
ported heads
ported exhaust manifolds, lots of material removed
no cat
hi flow dual outlet exhaust
fenderwell intake
auto lite 103 plugs gapped at 45 (copper)
egr removed and tuned out of the computer via custom chip
custom boost controller
water/ meth injection, custom controller

and a 4t65e hd with a 2750 stall converter and a stage 3 shift kit
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Old 06-05-2007, 11:45 PM   #10
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You swapped in a 4T65E? Interesting. Hows the computer like that? Did you rewire the tranny? I thought they had different wiring.

Sorry, that'* off topic. Start a new thread if you want to discuss the changes you did to the tranny.
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