Tuning for altitude

[RawkerStatus]

So been messing with a holley carb, I'm at 4500 feet and the jets that came with it are for sea level. After research, they said to drop down a jet size for every 2k feet. The carb came with 66 jets. I went down to 64 jets and it ran better. Timing is at 32degrees total. What do you guys think of the spark plug? This is cylinder 1.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

 

[Frankenchevy]

The electrode is neither brown, nor black nor white. Reading plugs with modern gas isn’t really as telling as it once was.

What protocol are you using leading up to pulling the plug? WOT, normal driving, babying it...?

 

[Rusty Nail]

Can't say with them platinum plugs..no experience.
Looks to me like you're running the wrong plugs.

xc_hide_links_from_guests_guests_error_hide_media

 

[C10MixMaster]

http://www.bgsoflex.com/holley.html Holley jet correction calculator

https://www.crankshaftcoalition.com/wiki/Reading_spark_plugs article on reading plugs


I agree with rusty platinums dont belong in a sbc

 

[RawkerStatus]

The electrode is neither brown, nor black nor white. Reading plugs with modern gas isn’t really as telling as it once was.

What protocol are you using leading up to pulling the plug? WOT, normal driving, babying it...?

This was driving 5 miles at 65, shutting down and pulling over and checking after a few minutes cooling down.

http://www.bgsoflex.com/holley.html Holley jet correction calculator

https://www.crankshaftcoalition.com/wiki/Reading_spark_plugs article on reading plugs


I agree with rusty platinums dont belong in a sbc

Thanks I've been looking for a calculator. Blue Print recommended those plugs since they run the 906 heads.

 

[Rusty Nail]

Oh yeah. Vortex heads.
I didn't read that.

*edit

I didn't read it cuz...lol?

Hold on... Was I suspossed to know that?
I don't believe it's assumed. Vortex heds are not the typical cylinder head in the majority of members' trucks.

 

[82sbshortbed]

I don't think 5 minutes of driving is long enough to get you an accurate reading. I'd run them a week and check.

 

[Bextreme04]

I wouldn't be running the plugs based on the head. I'd be running them based on the fuel and ignition system. If you aren't running fuel injection and Vortec ignition, I'd switch back to a standard plug. The older HEI's tend to not like the platinum or Iridium plugs and especially not anything over a 0.045" gap. I think those platinum Vortec plugs were gapped at 0.060" which could burn up the HEI coil pretty fast.

 

[RawkerStatus]

My bad, so it's a 350 Blueprint engine. 220 intake, 224 exhaust with .50 duration at 114 degree lobe separation cam. 609 heads with the plugs gapped at .45 per Blueprints recommendation. I've gotten about a max of 14 inches of vacuum after tuning with the 64 jets. Theres a hesitation at take off where I have to feather the throttle to get it not to stumble.

 

[C10MixMaster]

My bad, so it's a 350 Blueprint engine. 220 intake, 224 exhaust with .50 duration at 114 degree lobe separation cam. 609 heads with the plugs gapped at .45 per Blueprints recommendation. I've gotten about a max of 14 inches of vacuum after tuning with the 64 jets. Theres a hesitation at take off where I have to feather the throttle to get it not to stumble.

check the accelerator pump, there should be zero slop in the linkage and it should squirt at soon as you move the throttle.

 

[RawkerStatus]

check the accelerator pump, there should be zero slop in the linkage and it should squirt at soon as you move the throttle.

It squirts pretty good. I'm wondering if it's the wrong profile for the weight of the vehicle.

 

[C10MixMaster]

It squirts pretty good. I'm wondering if it's the wrong profile for the weight of the vehicle.

cam profile or a larger nozzle

 

[RawkerStatus]

cam profile or a larger nozzle

So weird thing, stumble is gone. Been in the 90s last few days. Dont know if that has anything to do with it.

 

[SquareRoot]

So the air thinned out with the rise in temp. Therefore, it was a lean stumble. This is why carburators suck. You get to tune them every time the weather changes. Thank goodness for efi.

 

[C10MixMaster]

Temperature defiantly makes a difference. I got a WB wideband air fuel ratio gauge , was planning on using it to tune and then remove it. I also have an APT Adjustable part throttle this allows me to adjust the cruise mixture . What I found is if I set the cruise mixture at 14.7 : 1 in the winter then when summer comes around the mixture will richen to 13.2 : 1 . So I made the Air fuel gauge permanent and now i can just tweak a couple screws when the seasons change to keep everything dialed in.

You must be registered for see images attach