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carb tuning

Old 5/13/13, 06:43 PM
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88 gt
Tfs tw 170 heads
Fti custom cam
.614 int lift
.607 exh lift
1.72 rr
Tfs double springs
Wieand stealth intake

Im running a 670 street avenger carb. I have a wideband af gauge. I just recently upgraded to the fti cam. Before that I was running a b303. With the b303 I was working on getting my af tamed then the lifters went out. So I never really had it better than a 15:1 af ratio.

This 15:1 with the b303 was already increasing the carb jets 4 sizes. Now with the new cam I cant even run it yet. I had it running for a couple minutes and its so lean my headers started turning red quickly. Right now my af is around 18:1.

My question is am I gonna need more than just huge jets? Do I need to modify the air bleeds? Maybe change accelerator pump?

I havent ran it past idle yet. But I know to the accelerator pump will cause a stumble if its not good enough for my setup.

Any carb tuning tips would be greatly appreciated. I do have a vacuum gauge and know that trick to setting the air bleeds. But I have had them all over the pkace with no avail. I also am running a steady 5-6 psi. And the pressure doesnt drop at all so I would think my pump is ok.

Here is an idle video if anyone is curious.

Last edited by onebadvert; 5/13/13 at 07:02 PM.
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Old 5/14/13, 08:56 PM
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No carb guys or anyone used to tuning super high lift cams eh?
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Old 5/15/13, 12:28 AM
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I'd play around with your timing to start off. Then maybe make adjustments to the carb. What's your fuel pressure?
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Old 5/15/13, 03:00 AM
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I think it's gonna be hard to find someone with experience in a cam with over .600 lift Dream!!!lmao
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Old 5/15/13, 03:51 AM
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Originally Posted by Fox85 View Post
I'd play around with your timing to start off. Then maybe make adjustments to the carb. What's your fuel pressure?
15* initial 36* total
6-7 psi.
I have played with timing and fuek pressure to no avail.
I wondering if I need a vacuum canister to help pull fuel?
Originally Posted by 91notchback View Post
I think it's gonna be hard to find someone with experience in a cam with over .600 lift Dream!!!lmao
Right? Lol
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Old 5/15/13, 09:46 AM
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make sure you don't have a vacuum leak.
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Old 5/15/13, 09:50 AM
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Originally Posted by skunk21 View Post
make sure you don't have a vacuum leak.
Funny. Cause I actually just called holley to verify my setup is up to the task. They said I shouldnt have any issues and to check for a vacuum leak.

Thanks
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Old 5/15/13, 09:56 AM
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yeah a nasty vacuum leak can cause a problem, both lean and rich conditions can get the headers to glow. you figured out it was lean. check for things like timing that is too retarted ( verify timing marks/pointer are marked correct ), vacuum leak(s) etc.
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Old 5/15/13, 10:05 AM
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Originally Posted by skunk21 View Post
yeah a nasty vacuum leak can cause a problem, both lean and rich conditions can get the headers to glow. you figured out it was lean. check for things like timing that is too retarted ( verify timing marks/pointer are marked correct ), vacuum leak(s) etc.
I also have a high idle. Which is another reason the vacuum leak makes sense. Now I just need to track it down.

I know my timing, fuel pressure, etc are all good. So hopefully I can find the leak. Ill get some propane and start spraying suspect areas.
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Old 5/15/13, 05:53 PM
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Check all vacuum lines. And try replacing your map sensor out
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Old 5/15/13, 05:58 PM
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Originally Posted by Fox85 View Post
Check all vacuum lines. And try replacing your map sensor out
No map sensor. Im running a carb with no ecu. I did find a vacuum leak but haven't had time to try and re tune it.
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