[Dick Boneske]

Has anyone tried the Kauffmann intake with Rochester Tri-Power carbs?

We put end carbs from a '66 Tri-Power on the intake that have the venturi's bored to 1.410", which is about .100 larger than the stock 1.310" factory size. We put .080" jets in the end carbs to compensate for the larger venturi size.

The center carb is a 2G similar to the 1971 Bonneville 455 carb with 1.375" venturi's. We jetted that to .070".

The engine is 461 cu in with extensively ported #64 iron heads., 9.5:1 compression.. Trans is a Muncie four speed. Due to the fairly radical Crower #60353 solid lifter cam, with .533/.555 lift, 256/265 degree duration at .050" lift and 108 degree centerline, we made extensive mods to the idle tubes, bypass restrictors, and weakened the power valve spring due to low vacuum.

Idle is decent at about 950 rpm, wide open throttle is awesome, but at light throttle in any gear around 2000-2500 rpm, there is severe bucking.

Looking for suggestions on how to eliminate the bucking.

[3X24SPD]

Hi Dick,

I have a couple of those beautiful Kauffman TriPower Intakes on larger motors with higher compression & large roller cams, running Rochester Carbs.
No bucking issues.

Off the cuff, it sounds like yours might be going lean in the transition between the idle circuit and main pullover.

You didn't mention where you are at with ignition system (stock Pontiac points I assume, with a good coil), vacuum advance & timing- which could be contributory.
I might try a couple easy things and see how it responds:

Try opening the plug gaps up a tad- and see if it improves the situation.
A wider gap would light off a leaner mixture better- see what happens.
Depending on if/what you have for vacuum advance numbers, try disconnecting and plugging the vacuum advance and see what happens.
Something like what you have I would expect manifold vacuum in the 10" range at idle. Should have something like a B28 Vacuum Advance Can at minimum.
Static/Total Timing is another thing you could try playing with and observe the results.
I assume you have a proper ignition curve set up, and with that you should be pretty much all in by 2500. I would think you would be somewhere around 12-14 initial with around 34 total- with those iron heads and that high of compression. Try bumping the initial down 5 degrees and see what that does.

[Dick Boneske]

3x24SPD,
Thanks for the replay. We've tried playing with the idle idle circuit in the venturi cluster and the power valve spring. The large center carb is jetted at .070", the enlarged end carbs at .080".

Spark plugs are dark, indicating a rich mixture. I agree the problem is the transition from idle to cruise speed. I've noticed the later 2G carbs have an extra circuit to help with pullover. I'm wondering if that may be helpful.

[chrisp]

Weaken the power valve spring more