Always tuning. Always.
March 9th, 2016, 05:19 AM
#1
Always tuning. Always.
Good Morning CO,
I pulled the Hurst out yesterday to cruise and do some tuning. I pulled the plugs after a good long cruise and honestly, I was having a hard time interpreting them. No smell of gas and it looks a little lean to me.
Let's talk about timing. I've been back and forth with using the VA at the full manifold port or the timed port. Yesterday I set the total 36* @ 3k and hooked up the VA at full vac- idle smoothed out and acceleration through the RPM band but on the test drive I was getting an off idle stumble.
Motor has less than 700 miles on it since build. All discussion is welcome as always.
I pulled the Hurst out yesterday to cruise and do some tuning. I pulled the plugs after a good long cruise and honestly, I was having a hard time interpreting them. No smell of gas and it looks a little lean to me.
Let's talk about timing. I've been back and forth with using the VA at the full manifold port or the timed port. Yesterday I set the total 36* @ 3k and hooked up the VA at full vac- idle smoothed out and acceleration through the RPM band but on the test drive I was getting an off idle stumble.
Motor has less than 700 miles on it since build. All discussion is welcome as always.
March 9th, 2016, 06:39 AM
#2
Registered User
Join Date: Dec 2011
Posts: 7,286
Accelerator pump in good shape?
Off idle to what throttle setting- 1/4 or WOT or ??
what carb?
factory QJET should have a link that prevents the secondary air valve from opening too quickly, it must be in place and choke pulloff operating as designed.
You can always swap to the Pontiac type secondary air valves with cutouts to help with the secondary transition.
Off idle to what throttle setting- 1/4 or WOT or ??
what carb?
factory QJET should have a link that prevents the secondary air valve from opening too quickly, it must be in place and choke pulloff operating as designed.
You can always swap to the Pontiac type secondary air valves with cutouts to help with the secondary transition.
March 9th, 2016, 07:43 AM
#3
Quick fuel slayer 750. I reviewed my notes from yesterday and made some more adjustments and I think I'm ok. Pulled the timing back to 34* and let out the idle a/f mixture screws 1/2 turn to richen it up and and it ran flawlessly. Longer trip this afternoon.
March 9th, 2016, 03:58 PM
#4
Registered User
Join Date: Mar 2010
Location: South-central Pa.
Posts: 1,309
Something I don'tunderstand About the manifold vacuum vs ported is when you connect vacuum advance to manifold when you open the throttle the vacuum in the manifold drops when it is connected to port on the carb when you throttle is opened vacuum goes up seems like it shouldn't work both ways I'm sure I'm just not getting something but I like to know what it is. did you see the part in the holley book that explains the the crossover slot.
Railguy
Railguy
March 10th, 2016, 04:43 AM
#5
http://www.chevytalk.org/fusionbb/sh...hp?tid/239321/
I really enjoyed this article; gave me a lot of perspective on the need of advance based on burn characteristics.
I believe the difference in full manifold vs. ported and the characteristics of vacuum has everything to do with the position of the throttle blades but I'm still reading and learning.
I really enjoyed this article; gave me a lot of perspective on the need of advance based on burn characteristics.
I believe the difference in full manifold vs. ported and the characteristics of vacuum has everything to do with the position of the throttle blades but I'm still reading and learning.
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