IDLE AFR QUESTION

[rgalajda]

With regards to the “ big HSAB's and the delayed activation was very clear in the car's function when conditions were just so. Made it very clear when the idle circuit was being deactivated.”

This subject or similar has been thrashed before and I for one don’t care which side of the fence anyone is on. And I believe circumstances could sway things. We don't need to go down this road again.

Now here I am voicing an opinion. You guys are good contributors to this forum and appreciated, so I hope we can continue.

[CDN]

I started this to understand cruise tuning in a large DP carb. from input here general consensus is work with IFR /bleeds first and in most cases you will be successful
It appears somme carbs can benefit from restricting he TSR and hat s where Im curious when do you go to TSR

[GTO Geoff]

Rg,
The 383 4 speed Cuda you mentioned. How much idle timing. Reason I ask:
Just finished dialling in a 850 TQ on a 440 Chys. TF heads, M1 single pan intake, sizeable sol roller cam, man trans.
With the generic 12-15* init timing, idle vac was 11".
With 44* of idle timing [ best idle achieved ], vac increased to 13.5". Idle speed was about 800-900, no tach to verify. Although the idle was not smooth, it was a lot smoother than I expected considering the parts used.

[Right hand drive]

[rgalajda]

[GTO Geoff]

Good man. You 'get' it!

[rgalajda]

This oem Holley carb for the Cuda was very interesting to work on , not at all like an aftermarket Holley. Aside from being a 3 circuit carb, It was a staggered bore with front throttle plates size of a 600 and rear throttle plates size of an 850 . The primary plates were factory drilled .083" ( idle bias air ). The curb idle ports were at the rear of the throttle plate .075".
The metering block used the standard .028" emulsion . PVRC was staggered .072" and .075" . The secondary metering plate was also staggered .093 and .091" jets.
Main jet was #64
IFR .039"
TSR/tube .024"
IAB .066
HSAB .027

SIAB .059
SHSAB .035

The only other change I made was to drill a .030" bypass in the vacuum pod and leave the check ball and original spring. The carb performed very good .
As for the cfm of this carb. Don't know , but definitely over 700 cfm.
This was a complete restoration that I spent a year putting back together for a friend.
The camshaft was 107LSA 227/240 duration Thumper cam.

[GTO Geoff]

What/where is the 3rd cct?

[rgalajda]

These OEM Mopar Holley carbs are usually referred to as the first 3 circuit Holley carbs. The idle circuit is independant of the transfer slot circuit. Idle circuit/ transfer slot circuit/ main circuit. These are pictures of another one I have on the shelf.

[GTO Geoff]

I am not sure about the logic. Isn't the t slot fed by the IFR [ idle jet ]?