worth upgrading carbs?

[janaka]

Hey guys;

I'm listing my entire mod list on my L28. I'm considering upgrading to triple weber carbs but I'm not sure if the gains are worth the cash outlay. The local guy is asking $600cdn for the 3 carbs, 3 rebuild kits, new linkage, manifold and all. Would my mod list below warrant these carbs for power gains? My current setup is pulling 162hp/162trq at the wheels.

L28 #F54 engine block, flattop pistons, siamesed cylinders. The block was professionally boiled and cylinders honed. New- piston rings, crankshaft bearings, oil pump, timing gear and chain kit, water pump, freeze plugs, gaskets and seals, hoses and belt.

P79 cylinder head. Performance rebuild including- resurfaced head, 3 angle valve grind, rocker arms, lash pads, springs and retainers, seals.

Schneider cam- .460 valve lift, 270 intake duration, 280 exhaust duration.

Dual domed top 4 screw SU carbs- rebuilt, performance needles and nozzles.

N33 carb intake manifolds.

K&N air filter.

MSA 6 into 1 header.

MSA 2.5 inch aluminized performance exhaust with super turbo muffler.

Holley “RED” fuel pump with adjustable pressure regulator.

Late model “close ratio” 5-speed transmission.

2+2 flywheel mated to a Perfection brand performance clutch.

R-200 differential with 3.90 gears, new u-joints, rebuilt half shafts, solid diff mount.

Nissan electronic distributor with a E12-80 ignition module, Standard Plus UC15 12V coil, NKG BPR6ES-11 spark plugs, Standard Plus silicone core A-5 spark plug wires, new fusible links and covers.

much appreciated

[jmortensen]

If they're 45 webers I'd go for it. I wouldn't bother with the 40's. Too much hassle and not enough return on the 40's. I would estimate that I got about a 40 hp gain by switching to 44 Mikunis. My engine was somewhat similar. I had a slightly larger cam (close to MSA stage IV) and about the same compression ratio of 8.5:1.

If you do buy the carbs, be prepared for some teething problems and don't let them get you too upset. You'll spend time and money figuring the Webers out, they're a lot more complicated than SU's. My biggest piece of advice would be to install an O2 sensor in the header collector. I used a narrowband one wire Bosch sensor and a simple volt meter to read it. Shoot for about .8V at WOT as that is about 13:1 air/fuel ratio. The O2 sensor works SO MUCH BETTER than trying to read plugs or smell the exhaust or whatever. Doesn't tell you how to fix the mixture, but at least you'll have an idea of what rpm range and load condition is lean or fat, and you can use that info to figure out what jets to change.

Oh and if you're scared of the Webers the Mikunis are a lot easier to tune as they are much less adjustable.