questions on a 32/36 install

[erichappymeal]

Hi all, Im installing a weber 32/36 carb on my L16 510 wagon (coming from a 32/34) and i have some questions on a couple of things, and how things SHOULD be routed.

First off, vacuum advance, should i hook it up to the carb or to the manifold? P.O. installed an HEI coil/distributor if that makes a difference. From what i could gather the carb hookup is more emissions friendly, but this seems to be a hot topic of debate, so im curious what everyone else has done.

second, EGR/crankcase vent lines. P.O. tee'd the crankcase vent and VC vent into the air filter housing. new carb doesnt seem to have any spot to route the EGR into, so i feel like my best bet is to block off that crankcase vent, and just put a breather off of the VC. is this the most common option? and what do you block off that crankcase vent line with? my intake has the PCV inlet plugged off.

which then brings me to my next, possibly most important question: the brake vacuum setup on a non-booster car. i found this picture:


here i can see they have the lower port connected to that little nipple on the crankcase vent pipe. is this the correct setup? P.O. had both ports capped off, and the upper port on the brake line connected to a port on the filter housing (i was looking for a reducer to go from the larger white connector from the kit to the small line the brakes require).


i have probably seen a dozen different picture showing the correct way to route this things, but now that i need it i cant find them anywhere.

there has been a lot of hackwork done on this car as well, and i know that i cant always trust the P.O.s work, and i am not well versed in datsun so i am at a loss here. Thanks in advance.

[datzenmike]

The block vent should be connected to the PCV valve in the intake as shown in the picture. The valve cover vent should go to the air filter housing. I hate when people fuck with this beautifully simple and benign system through ignorance. In operation, at idle and part throttle, intake vacuum draws a small amount of fumes from the crank case which is replaced by filtered air from the air filter. The 'blow by' of combustion gasses, oil and gas fumes and water vapor is burned in the engine. If at full throttle when vacuum is lowest, there is more blow by than can be taken into the intake it reverses out the valve cover vent and is sucked into the carb. Nothing is wasted or escapes. It has zero effect on performance or running but it removes combustion by products and moisture from the engine and prevents it diluting the oil. An engine with a properly functioning PCV will be able to extend it's oil change interval and run cleaner.

The 510 never had EGR so no worries on that. EGR was introduced on the '74 L20B in the 610 and the L18s in the 620 and 710s of that year..

Vacuum advance should come from a port on the carburetor. If you run it on the intake vacuum it will run too advanced at low speed and may ping and you will need to reduce the timing. When the engine revs up the timing will be not advanced enough the amount you had to back it off. You could modify the distributor to correct this but why not just run it the proper way?

EI with the GM HEI module will have no bearing on running.

[Byron510]

Mike, I love your blunt-ness, but you are right about the vent and PCV.
OP - you may have to adjust jetting on that carb to make it optimal. The addition of a PCV will lean out an otherwise correct mixture - but who's to say your mixture wasn't rich to begin with.

As Mike noted, distributor vacuum must be taken above the throttle plate - some DGV's do have this port.
Brake booster vacuum is manifold vacuum - your stock manifold has a port on Cyl#4.

You're on your way.

Byron

[erichappymeal]

update: so i am an idiot. the port/hose in question is highlighted in red here:



which, is not for the brakes, but when i glanced over things while putting tools away (2 year old came outside and wanted to play with them so i had to close up shop). it looked like it went to the brake master. but, im guessing its actually for the fuel tank breather. I see the port on the intake manifold now, which is plugged (non booster car).

The block vent should be connected to the PCV valve in the intake as shown in the picture. The valve cover vent should go to the air filter housing. I hate when people fuck with this beautifully simple and benign system through ignorance. In operation, at idle and part throttle, intake vacuum draws a small amount of fumes from the crank case which is replaced by filtered air from the air filter. The 'blow by' of combustion gasses, oil and gas fumes and water vapor is burned in the engine. If at full throttle when vacuum is lowest, there is more blow by than can be taken into the intake it reverses out the valve cover vent and is sucked into the carb. Nothing is wasted or escapes. It has zero effect on performance or running but it removes combustion by products and moisture from the engine and prevents it diluting the oil. An engine with a properly functioning PCV will be able to extend it's oil change interval and run cleaner.

very interesting. i never really put much thought into the system other than seeing how much oil and soot it can potentially bring into intake systems. i will have to source the PCV and hose now. i can tee the vacuum hose from the port above the hose in red (previous picture) to the VC vent before routing it into the air filter housing? or should it have its own connection?

OP - you may have to adjust jetting on that carb to make it optimal. The addition of a PCV will lean out an otherwise correct mixture - but who's to say your mixture wasn't rich to begin with.

this is a new off the shelf install.

[datzenmike]

That hose connects to the flow guide valve mounted low on the strut tower it's pointing at. The flow guide valve does several things depending if the engine is running or not. When off, it allows evaporated gas from the tank (under very slight positive pressure) into the engine crank case for storage. When the engine starts, intake vacuum draws these fumes into the intake via the PCV valve to be burned. At the same time it will allow filtered air back into the tank as the tank empties and is under very slight negative pressure. A non vented gas cap is needed for this to work. Later model Datsuns pipe the tank fumes to a charcoal canister that absorbs and saves them. When the engine starts fresh air is drawn through the canister by vacuum from the PCV valve. This vacuums up the stored fumes and burns them.

You would be lucky to get over 100K miles on a 1950's engine. Yes the oil was terrible but the PCV is one of the greatest improvements to engine longevity. If you drove far enough the engine heat would boil away the water vapor that sweated and condensed inside the block over night. Old engines just vented the crank case fumes outside the engine and under the cars but it was passive. A PCV actually vacuum cleans the engine as you drive it.