Holley 90670 fine tuning

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Grand_Wag_85
Posts: 1792
Joined: Sat Aug 27, 2011 8:46 am

Holley 90670 fine tuning

Post by Grand_Wag_85 »

Just swapped a Holley 90670 (670 CFM off road truck avenger) onto my ‘77 401. Only thing I’ve done to the carb so far is to jet it for 10oooFT. The manual says to drop one number for ever 2oooFT elevation gain. Factory jets are 68&89 and I’ve gone to 63&84.

Truck will idle great but under acceleration will stumble and stall out if you don’t lift your foot. It’s drivable but pretty much only on the road. Pulling out of the driveway requires way over revving the engine to avoid stalling.

I’m guessing I need to adjust the accelerator pump?
82 J10
77 J10 Golden Eagle 401
88 GW

You know it's bad when your car is on the EPA's 10 most wanted list!

Dr.Bob
Posts: 108
Joined: Thu Dec 26, 2019 8:57 pm

Re: Holley 90670 fine tuning

Post by Dr.Bob »

You may either need a more aggressive accelerator-pump cam, or increase the shooter size, or both. I know I needed to do both on my 600cfm carb at sea level to get rid of the bog.

Also make sure your ignition advance is coming on quick; AMCs tend to like a lot of advance right off idle, or else they bog.
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Topic author
Grand_Wag_85
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Joined: Sat Aug 27, 2011 8:46 am

Re: Holley 90670 fine tuning

Post by Grand_Wag_85 »

I’ll take a look. Thanks!
82 J10
77 J10 Golden Eagle 401
88 GW

You know it's bad when your car is on the EPA's 10 most wanted list!

chevelleguy
Posts: 379
Joined: Mon Oct 08, 2012 10:11 am
Location: Hughes Springs, TX

Re: Holley 90670 fine tuning

Post by chevelleguy »

This is a great book if you are going to own a tune on a Holley.

https://www.summitracing.com/parts/sad-sa216


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David
'83 Wag Limited, 360/727/pinned 229/D44 front/AMC20,lockrite,rear/6" BJ lift w/ 35/12.50/15 M/T Baja MTZ/ Pro-Jection EFI.

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