Carb Sync Problem

1972-1979 Datsun 620 forums. All 620-specific topics and discussion can be found here.
Posts: 14
Joined: Tue Jan 10, 2012 10:30 am
Car: 1975 Datsun 620 Longbed


L20B with dual SUs from L16 SSS. Rear carb draws plenty of air, front carb doesn't draw much. Can't adjust them to get even close.

Also smokes pretty bad, and gets a bit of a backfire from one or more of cylinders 3 & 4.

Adjusted valve clearances, hoping to find a tight valve. They were already pretty close.

Compression check said 120-125lbs. except #4, which is 110. Does not show symptom of blown head gasket.

Idles great once warmed up. Starts right up.

I had this same intake & exhaust setup on another L20B in a different truck before, and it ran superbly and hauled a**. Even passed smog test without cheating.

This thing is not running well. Fire away with ideas!

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