HiI have a 26T coupe with a L20B engine and matching 5 speed (neat huh) The engine is bored .40 has 280Z pistons& valves,a87 head,475 lift camwith275 duration offenhauser 4 brl intake,holley 390 and a header. What I want to know is---I have the valves set to factory specs -.008&.010 when hot and they make a lot of noise should I set them tighter? Also it seems this engine is fine at high rpm, but has no torque (real dog on hills) is this normal?Any help will be appreciatedthanksGary

I used to have a 620 with a L20B it had been bored .40 over, I tried to get rid of the valve niose by fudging on the valve clearance. I kept burning valves and could never find a happy medium point for the adjustment. The .40 boring came after I started doing gas mileage experiments with it.

The L20B is a very strong and torquey engine. If yours is behaving like a tired dog, something it wrong, either mechanically or perhaps the electronic ignition system.

I have an L20B in my 610 and it is very strong. The difference between the L18 ( in my 710 ) and the L20B ( my 610 ) is writ and ostensible.

Something is wrong, that engine is quite powerfull.

HI I know its awhile after your asked for help, but if that L20 is still down on power it is because the cam you have in it is the same specs as a cam I used in one of my datsun pickups back in the early eighties. It is a datsun motorsports RALLY camshaft and has a useable power band of 4000 to 7500 rpm, I bet your motor did not like to idle below 1500 rpm and at that rpm it was still very rough. I built a L20b stock bottom end with SSS cylinder head, 68 MG 1.5 inch SU carbs, rally cam you have ,clifford research header with 2.5 inch exhaust thru cherry bomb glass pack. It idled at 1500 rpm very rough ( cammed up ) and had very poor bottom end power but would come alive at 4000rpm and pull strong all the way to 7500 rpm. With the five speed it made 4th & fifth gears useless for any real accelration just steady cruising, i would drop into 2 or 3rd to gain speed fast. It would run 110 mph in third gear at 7500 rpm. You would be better off using a stiock L18 0r 20b cam to give you good low and mid range power and it will still pull strong to 6000 rpm. I currently have a 78 620 with L20b, U67 head, stock cam, the same twin su setup, 510 factory cast iron header and true dual exhaust and truck runs excellent , very fun to drive, more power with same mpg. Hope this helps if you have not corrected problem already

Mikemotor.

Nice info Mike....welcome to the forum!